There are probably thousands of kinds of metabolisms, or chemical processes that maintain life, said Donald Canfield, a geobiologist at the University of Southern Denmark, but "virtually all eukaryotes" (life-forms whose cells contain a nucleus) and a vast array of prokaryotes (life-forms that lack a nucleus), use oxygen.

Canfield is talking primarily about heterotrophs — organisms, including humans, that get their nutrients and energy by consuming other organic matter. Not all organisms do this exclusively. For example, "plants get their carbon from CO2 in the air," said Dan Mills, a postdoctoral researcher at the University of Munich.

Heterotrophs break down organic matter in food by stripping electrons off of it. These are passed from one enzyme to another in the membrane of the mitochondria, generating a small current that pumps protons across this barrier. And given its high electronegativity, oxygen usually serves as the final station on this electron transport chain, accepting the electrons and picking up two protons to form water.

The process essentially creates a reservoir of protons that then flood through a protein channel in the membrane like a tiny hydroelectric dam. And, like a turbine, the protein synthesizes energy in the form of adenosine triphosphate (ATP) as it spins, explained Nick Lane, a professor of evolutionary biochemistry at University College London, in a public presentation. The cell can then use this packaged energy or send it off into the body to do things.

Life can use many other electron acceptors — like sulfate, nitrate and iron — but oxygen is the highest-energy acceptor available.

"The reduction of oxygen provides the largest free energy release per electron transfer, except for the reduction of fluorine and chlorine," University of Washington professor David Catling and his co-authors explained in a paper published in the journal Astrobiology.

Related: What is the world's most dangerous chemical?

Chlorine and oxygen can generate similar amounts of energy. Fluorine could certainly provide more energy than oxygen, but "fluorine is [...] useless as a biological oxidant because it generates an explosion upon contact with organic matter," they wrote in the study. That's not a gas you'd want to breathe.

Chlorine and fluorine are also poisonous, which highlights another benefit of oxygen. Aerobic respiration doesn't produce any toxic compounds, just water and carbon dioxide. However, oxygen's reactivity can be an issue if it builds up in tissues, where it can damage cellular components like DNA and proteins. That's why antioxidants, in moderation, are good for our health.

Oxygen is also far more abundant than fluorine, chlorine or the myriad electron acceptors used in other forms of respiration. Despite its proclivity for forming compounds with other atoms, a copious amount of oxygen is constantly produced via photosynthesis. This enables it to accumulate in the atmosphere and dissolve in water, where it is readily available to life. And, as a gas, it's easy to transport across membranes, Canfield and Mills explained.

Speaking of abundance, why not use nitrogen, which comprises 78% of Earth's atmosphere?

"The main problem with nitrogen is that it's triple bonded," Canfield said. "And it's very, very difficult to break."

Nitrogen is an important component of many biologic compounds, and there are whole groups of organisms that specialize in the energy-intensive processes required to break nitrogen's strong bonds to make it bioavailable, Canfield said.

Oxygen's unique utility comes down to quantum physics. Oxygen in its normal ground state can only accept electrons in the same spin state, not as an electron pair, which is the usual currency of chemistry.

"So the real trick to oxygen is that it can accumulate to high levels without reacting, but releases a lot of energy (to pump protons) when it is fed electrons one at a time," Lane told Live Science in an email.

So it seems oxygen sits in a sweet spot of reactivity and availability. It's milder than halogens such as chlorine and fluorine, and it isn't bound too strongly, like nitrogen. But it's much more reactive than other electron acceptors, like sulfate and nitrate.

Oxygen is easy to acquire, and it doesn't generate toxic compounds that require further processing. What's more, plants produce copious amounts of this reactive gas through photosynthesis, enabling us to use it to fuel our own bodies.

Periodic table of elements quiz: How many elements can you name in 10 minutes?

By exposing a common type of plastic to an inexpensive catalyst and leaving it exposed to ambient air, researchers broke down 94% of the material in just four hours.

The plastic transformed into terephthalic acid (TPA), a highly valuable building block for polyesters. Because TPA can be upcycled into more valuable materials, the process offers a safer and cheaper alternative to current plastic recycling methods. The researchers published their findings Feb. 3 in the journal Green Chemistry.

"The U.S. is the number one plastic polluter per capita, and we only recycle 5% of those plastics," co-corresponding author Yosi Kratish, a research assistant professor of chemistry at Northwestern University, said in a statement. "What's particularly exciting about our research is that we harnessed moisture from air to break down the plastics, achieving an exceptionally clean and selective process. By recovering the monomers, which are the basic building blocks of PET [polyethylene terephthalate], we can recycle or even upcycle them into more valuable materials."

Plastic waste is an increasingly important issue. Over half of the plastic ever made has been produced since 2000, and annual production is projected to double by 2050, according to the European Environment Agency.

To date, only 9% of the plastics ever produced have been recycled. The remainder, with lifetimes often lasting generations, can have serious environmental and health impacts. For example, they wash out to sea to form floating blobs of trash, harm wildlife, and break down into microplastics that can enter the human brain and other parts of our bodies.

Related: Will we ever be able to stop using plastic?

To find a new method to break down some of this waste, the researchers applied a molybdenum catalyst — a silver, ductile metal — and activated carbon to PET, the most common type of polyester plastic. The researchers then heated the mixture. After a short time, this broke the polyethylene's chemical bonds.

Then, when the team exposed the material to air, the mixture transformed into TPA, a valuable polyester precursor; and acetaldehyde, an industrial chemical that is also valuable and is easy to lift from the mixture.

When they tested the method on mixed plastics, the researchers found that it had an effect only on the polyester materials. That meant they didn't have to presort the plastics. It worked on plastic bottles, T-shirts and colored plastics, breaking them down into pure, colorless TPA.

"It worked perfectly," Kratish said. "When we added extra water, it stopped working because it was too much water. It's a fine balance. But it turns out the amount of water in air was just the right amount."

The team's next steps will be to adapt the process to large-scale industrial applications.

"Our technology has the potential to significantly reduce plastic pollution, lower the environmental footprint of plastics and contribute to a circular economy where materials are reused rather than discarded," study first author Naveen Malik, who was a researcher at Northwestern University at the time, said in the statement. "It's a tangible step toward a cleaner, greener future, and it demonstrates how innovative chemistry can address global challenges in a way that aligns with nature."

Often referred to as the "holy grail" of solar power, perovskite cells offer a lightweight alternative to traditional silicon-based solar technology. Their flexible structure enables them to be applied to cars and phones in the form of a printable layer so they can charge on the go.

Sounds too good to be true? So far, you're right. Perovskites come with some major flaws. Notably, they degrade quickly due to chemical reactions with moisture in the air that make them leak iodine.

But now, a team of researchers has found a solution to this problem. By embedding nanoparticles within the perovskites, they produced a new cell that lasts for 1,530 hours, a near-tenfold increase on previous perovskite solar cell designs. The researchers published their findings Feb. 20 in the journal EES Solar.

"By addressing these common challenges we see with perovskite solar technology, our research blows the doors wide open for cheaper, more efficient and more widely accessible solar power," study co-author Imalka Jayawardena, an engineering researcher at the University of Surrey's Advanced Technology Institute in the U.K., said in a statement. "What we've achieved here is a critical step toward developing high-performance solar cells that can withstand real-world conditions — bringing us closer to their commercial use at a global scale."

Solar power surge

As the fastest-growing and cheapest form of renewable energy, solar power is key to cutting greenhouse gas emissions. But the technology's growth is hampered by its reliance on silicon, a finite and non-renewable resource that, in its purest form, is costly to produce.

To get around this bottleneck, scientists have looked to develop perovskite alternatives — synthetic versions of naturally occurring calcium titanium oxide crystals that can be made at a fraction of the cost. But unlike pure silicon cells, which can last for decades, solar cells made from perovskite only last for 100 or so hours, drastically limiting their utility.

Related: Ultra-thin solar 'coating' can turn phone cases and EVs into mini power generators

In the new study, the scientists looked for a way to trap the iodine that leaks from perovskites. Their solution was to embed tiny nanoparticles of aluminum oxide within the cells as they were manufactured. This not only prevented the iodine from leaking but also created a more uniform and electrically conductive structure.

After testing these cells under extreme heat and humidity, the researchers found that the modified cells maintained a high performance for more than two months (1,530 hours), a significant improvement on the 160-hour lifespan of unenhanced perovskite cells.

The researchers plan to continue investigating their new technique to see if these gains can be built upon further.

"A decade ago, the idea of perovskite solar cells lasting this long under real-world conditions seemed out of reach," study lead author Hashini Perera, a researcher at the Advanced Technology Institute, said in the statement. "With these improvements, we're breaking new ground in stability and performance, bringing perovskite technology closer to becoming a mainstream energy solution."

And right before they split, the molecules did something completely unexpected: They flipped 180 degrees.

This micro acrobatic stunt takes energy, which offers a crucial explanation for why splitting water takes more energy than theoretical calculations suggested.

The researchers say that studying this further could offer key insights into making the process of splitting water molecules more efficient — opening a pathway to cheaper clean hydrogen fuel and breathable oxygen for future Mars missions. They published their findings March 5 in the journal Science Advances.

Making hydrogen fuel

Hydrogen has a number of key properties that make it an enticing source of green energy. The energy-rich fuel is capable of powering trucks and even cargo ships, and it is the only alternative to fossil fuels in industries such as steel and fertilizer manufacturing. When it's burned, the fuel releases water instead of carbon dioxide.

Yet the steep energy requirements for hydrogen production severely limit the scale at which the fuel is produced. According to the International Energy Authority, 322 million tonnes (354 million tons) of hydrogen fuel needs to be produced each year to meet global energy needs. But in 2023, only 97 million tonnes (107 million tons) was manufactured at a monetary cost 1.5 to six times greater than fossil fuel production — and the vast majority of it was made using fossil fuels too.

Related: Scientists discover revolutionary method that makes fuel from water and sunlight — but it's not finished yet

Hydrogen fuel is made by adding water to an electrode and then splitting the water with an applied voltage into hydrogen and oxygen.

This process is most efficient when the chemical element iridium is used as a catalyst for the oxygen evolution reaction that cleaves oxygen from water molecules. But iridium only arrives on our planet from meteorite impacts, making it costly and scarce.

But even when using iridium, the process is less efficient than scientists believe it should be.

"It ends up taking more energy than theoretically calculated. If you do the math, it should require 1.23 volts. But, in reality, it requires more like 1.5 or 1.6 volts," study lead author Franz Geiger, a professor of chemistry at Northwestern University, said in a statement. "Providing that extra voltage costs money, and that's why water splitting hasn't been implemented at a large scale."

To better understand the energy requirements of this process and why it's less efficient than theory suggests, the researchers placed water on an electrode inside a container and measured the molecules' positions using the amplitude and phase of laser light shone onto them.

When the scientists applied a voltage across the electrode, they observed that the molecules rapidly flipped and rotated so that their two hydrogen atoms touching the electrode faced up and the oxygen atom faced down.

"Electrodes are negatively charged, so the water molecule wants to put its positively charged hydrogen atoms toward the electrode's surface," Geiger said. "In that position, electron transfer from water's oxygen atom to the electrode's active site is blocked. When the electric field becomes strong enough, it causes the molecules to flip, so the oxygen atoms point toward the electrode's surface. Then, the hydrogen atoms are out of the way, and the electrons can move from water's oxygen to the electrode."

By measuring the number of molecules that rotated and the energy required for them to do so, the researchers found that this flipping was likely a necessary and unavoidable part of the splitting process. What's more, the researchers discovered that higher pH levels made this process more efficient.

Further studying this process could help scientists to design more efficient catalysts to use in the process, and to better understand the chemical processes involved, the researchers said, while also offering fresh insights into how water behaves.

"Our work underscores how little we know about water at interfaces," Geiger said. "Water is tricky, and our new technology could help us understand it a bit better."

"By designing new catalysts that make water flipping easier, we could make water splitting more practical and cost-effective," he added.

Specialized nanoparticles that absorb sunlight and convert it to heat are embedded within the new material, which was described late last year in the journal Advanced Composites and Hybrid Materials. At the same time, temperature-responsive dyes incorporated into the fibers reversibly change color, allowing users to visually monitor temperature fluctuations.

Maintaining body temperature

For years, scientists have designed wearable heaters to help maintain a comfortable body temperature in cold environments. Such fabrics could be used in mountain rescue equipment and even pet clothing, but existing designs typically rely on expensive components such as metal nanomaterials or cumbersome battery-powered heating elements.

To get around these problems, chemical engineer Yuning Li and his team at the University of Waterloo in Canada looked to photothermal polymers, which are plastic-like materials that convert light into heat.

Nanoparticles of the two polymers — polyaniline (PANI) and polydopamine (PDA) — are embedded within a matrix of thermoplastic polyurethane (PTU) fibers, a material widely used to produce waterproof clothing and sportswear. The team also incorporated various temperature-responsive (thermochromic) dyes into the mix during the spinning process, producing a series of fibers that changed color as the temperature of the material increased.

These newly spun fibers were readily woven into fabric and the team knitted a tiny sweater for a teddy bear to test the properties of the smart material. The red jumper reached an impressive 128.3 F (53.5 C) after just 10 minutes of sun exposure. As the temperature climbed, the red dye molecules changed chemical structure, causing them to turn white.

"The incorporated nanoparticles are highly efficient at absorbing sunlight across a range of wavelengths," Li told Live Science in an email. "When sunlight hits these nanoparticles, they absorb the energy and release it as heat through a process called photothermal conversion."

The smart fabric has a soft and elastic texture, which allows the material to stretch by as much as five times its original size and retain its color- and temperature-changing properties even after 25 washes, according to the study. "We prioritized durability, ensuring the fabric could withstand repeated use and environmental exposure while maintaining its innovative properties," Li said.

The team is working to prepare the material for commercial manufacturing, but they still have to do further testing before it can gain widespread use.

"The next steps for this research focus on reducing production costs, scaling up the fabrication process, and ensuring the fibers are safe for prolonged skin contact," Li said.

Editor's Note: The headline for this story was updated on Monday, Feb. 3 at 1:11 p.m. EST to note that the fabric heats up more than 50 degrees, not almost 50 degrees.

The new nanomaterials, made using machine learning and a 3D printer, more than doubled the strength of existing designs. The scientists behind the new study said they could be used in stronger, lighter and more fuel-efficient components for airplanes and cars. They published their findings Jan. 23 in the journal Advanced Materials.

"We hope that these new material designs will eventually lead to ultra-light weight components in aerospace applications, such as planes, helicopters and spacecraft that can reduce fuel demands during flight while maintaining safety and performance," co-author Tobin Filleter, a professor of engineering at the University of Toronto, said in a statement. "This can ultimately help reduce the high carbon footprint of flying."

In many materials, strength and toughness can often be at odds. Take a ceramic dinner plate, for example: while plates are usually strong and can carry heavy loads, their strength comes at the cost of toughness — it doesn’t take much energy to make them shatter.

Related: Scientists discover revolutionary method that makes fuel from water and sunlight — but it's not finished yet

The same problem applies to nano-architectured materials, whose construction from multitudes of tiny, repeating building blocks 1/100th the thickness of a human hair makes them strong and stiff for their weight, but can also cause stress concentrations that lead to sudden breakages. So far, this tendency to shatter has limited the materials' applications.

"As I thought about this challenge, I realized that it is a perfect problem for machine learning to tackle," first-author Peter Serles, an engineering researcher at Caltech, said in the statement.

To search for better ways to design nanomaterials, the researchers simulated possible geometries for their design before passing them through a machine learning algorithm. By learning from the designs they had generated, the algorithm was able to predict the best shapes that would evenly distribute applied stresses while also carrying a heavy load.

With these shapes in hand, the researchers used a 3D printer to create their new nanolattices, finding that they could withstand a stress of 2.03 megapascals for every cubic meter per kilogram — a strength five times higher than titanium.

"This is the first time machine learning has been applied to optimize nano-architected materials, and we were shocked by the improvements," Serles said. "It didn’t just replicate successful geometries from the training data; it learned from what changes to the shapes worked and what didn’t, enabling it to predict entirely new lattice geometries."

The researchers said their next steps will center on scaling up the materials until they can be used to make bigger components, while also searching for even better designs using their process. The primary aim is to design much lighter and stronger components for vehicles in the future.

"For example, if you were to replace components made of titanium on a plane with this material, you would be looking at fuel savings of 80 litres per year for every kilogram of material you replace," Serles said.

The sample, which the OSIRIS-REx spacecraft collected from the asteroid Bennu and returned to Earth in 2023, contains all five nucleobases — the "letters" that make up DNA and RNA — alongside mineral compounds, all of which have never previously been seen on extraterrestrial rocks.

The minerals are rich in carbon, sulfur, phosphorus, fluorine and sodium, making them resemble those left in the crusts of dried lake beds on Earth — except they date to the birth of the solar system 4.6 billion years ago. These elements, alongside the five nucleobases that make up DNA and RNA, are the basic building blocks for life on our planet.

The two teams of researchers who made the discoveries published their findings Jan. 29 in two papers in the journal Nature Astronomy.

"We now know from Bennu that the raw ingredients of life were combining in really interesting and complex ways on Bennu's parent body," study co-lead author Tim McCoy, curator of meteorites at the Smithsonian's National Museum of Natural History, said in a statement. "We have discovered that next step on a pathway to life."

Bennu is a potentially hazardous asteroid that has a 1-in-2,700 chance of striking Earth in the year 2182 — the highest odds of any known space object. But scientists are more interested in what's trapped on the space rock: As a carbon-rich asteroid, it likely contains many of the primordial molecules present when life first emerged on Earth.

Related: NASA's OSIRIS-REx mission almost bit the dust — then Queen guitarist Brian May stepped in

OSIRIS-REx launched in September 2016 and traveled 200 million miles (320 million kilometers) to reach Bennu.

Once there, the spacecraft orbited the asteroid for nearly two years as flight engineers searched for a landing site. Upon making contact with the space rock, OSIRIS-REx fired a burst of nitrogen from its Touch-and-Go Sample Acquisition Mechanism to stick the landing and prevent itself from sinking through the asteroid. The nitrogen burst captured a 4.29-ounce (121.6 grams) sample in the process.

In October 2023, the sample was brought to Earth aboard OSIRIS-REx's capsule, which reached speeds of up to 27,000 mph (43,000 km/h) before it deployed its parachute and landed safely in the Utah desert. To avoid contamination, the sample container was taken to a clean room before being opened.

The researchers behind the first study received slices of the Bennu sample, which they examined under a scanning electron microscope. This enabled the team to study features on the sample's surface with a resolution of one-hundredth the width of a human hair.

The scientists discovered sodium carbonate, typically found in evaporated lakes that once contained life on Earth, on the space rock's surface. Within the sodium carbonate, the team found 11 minerals that are important precursors for organic compounds. The mineral compositions differed subtly from those found on our planet; being rich in phosphorus and poor in boron, when the reverse is true in Earth’s lakes.

The researchers think brine similar to that found on Bennu could also exist on other bodies in the solar system, such as the dwarf planet Ceres and Saturn's icy moon Enceladus.

In the second study, conducted by scientists in Japan, a separate piece of the sample was also found to contain the five nucleobases — adenine, guanine, cytosine, thymine and uracil — which combine with ribose and phosphate to form DNA and RNA, the ladder-like structures that make up the genetic code of all life on Earth.

This is the first time that scientists have found these nucleobases on a distant asteroid. In 2023, a sample taken from the Ryugu space rock by the Hayabusa2 spacecraft was found to contain uracil, yet the other nucleobases were missing.

It's unclear what this means for life beyond our planet. While the existence of these minerals on Bennu is a sure indication that the asteroid had the right ingredients for life, the researchers are unsure if the asteroid's environment was too harsh for the compounds to grow into complex organic structures. To further investigate, the scientists plan to reexamine meteorites in their collection for similar salts and compounds.

"We now know we have the basic building blocks to move along this pathway towards life, but we don't know how far along that pathway this environment could allow things to progress," McCoy said.

Researchers fused lines of molecules like links in a chain to create sheets of the world's first two-dimensional mechanically interlocked material (2D MIM), which has length and width. The material contains 100 trillion chemical bonds per square centimeter (around 650 trillion per square inch), which is the highest density of mechanical bonds ever achieved, the researchers reported in the study, published Jan. 16 in the journal Science.

The study authors added a small amount of the material to a tough plastic material called Ultem — also made from molecule chains. Ultem is already incredibly strong but became even stronger with the 2D MIM. The research, which could eventually be used in body armor, was partly funded by the government's Defense Advanced Research Projects Agency.

"It's similar to chainmail in that it cannot easily rip because each of the mechanical bonds has a bit of freedom to slide around," study co-author William Dichtel, a chemistry professor at Northwestern University in Illinois, said in a statement. "If you pull it, it can dissipate the applied force in multiple directions. And if you want to rip it apart, you would have to break it in many, many different places."

Related: Scientists discover revolutionary method that makes fuel from water and sunlight — but it's not finished yet

The 2D MIM material is made of interlocked polymers, which are long chains of smaller molecules, called monomers. The team took lines of X-shaped monomers and arranged them into crystal structures that react together so that the ends of the monomers bond with the ends of other monomers, according to the statement.

Each monomer's X-shape left gaps in which researchers could weave additional lines of these molecular building blocks, creating layers of interlocked 2D polymers within the crystals. The scientists then dissolved the crystals to retrieve the interlocked polymers.

"After the polymer is formed, there's not a whole lot holding the structure together," Dichtel said. "So, when we put it in solvent, the crystal dissolves, but each 2D layer holds together. We can manipulate those individual sheets."

To test their new material, the researchers made composite materials out of 97.5% Ultem fiber and 2.5% 2D MIM. The small amount of interlocked 2D polymer increased the force needed to deform Ultem fibers by 45% and the amount of stress the Ultem could withstand by 22%, according to the study.

"We have a lot more analysis to do, but we can tell that it improves the strength of these composite materials," Dichtel said. "Almost every property we have measured has been exceptional in some way."

The new 1,076-square-foot (100 square meters) reactor uses photocatalytic sheets to split apart the oxygen and hydrogen atoms found in water molecules, thus siphoning the hydrogen away to be used as fuel.

While the technology remains in its infancy, the scientists behind the research say that, if more efficient photocatalysts can be developed, their breakthrough could enable the production of cheap, sustainable hydrogen fuel to meet various energy needs. They published their findings Dec. 2 in the journal Frontiers in Science.

"Sunlight-driven water splitting using photocatalysts is an ideal technology for solar-to-chemical energy conversion and storage, and recent developments in photocatalytic materials and systems raise hopes for its realization," senior author Kazunari Domen, a chemistry professor at Shinshu University in Japan, said in a statement. "However, many challenges remain."

Upon being exposed to light, photocatalysts boost chemical reactions that break water molecules down into their constituent parts. However, most existing "one-step" catalysts — which decompose water into hydrogen and oxygen in one go — are extremely inefficient, leaving most of the hydrogen fuel to be refined using natural gas, a fossil fuel.

Related: 'Holy grail' of solar technology set to consign 'unsustainable silicon' to history

To look for a way past this deadlock, the researchers behind the new study investigated a photocatalyst that uses a more sophisticated two-step process, with one step separating out the oxygen and the next step removing the hydrogen.

Creating a photocatalyst for this process enabled the scientists to build their prototype reactor, which ran for three years and worked even better using real sunlight than the ultraviolet light used in the lab.

"In our system, using an ultraviolet-responsive photocatalyst, the solar energy conversion efficiency was about one and a half times higher under natural sunlight," first author Takashi Hisatomi, a researcher at Shinshu University, said in the statement. "Simulated standard sunlight uses a spectrum from a slightly high latitude region. In an area where natural sunlight has more short-wavelength components than simulated reference sunlight, the solar energy conversion efficiency could be higher."

Despite these promising gains, the efficiency of the reaction is still too low for commercial use.

"Currently, the efficiency under simulated standard sunlight is 1% at best, and it will not reach 5% efficiency under natural sunlight," Hisatomi said.

To make the important strides to increase efficiency, the scientists have called on others to create better photocatalysts and larger reactors. Work on safety will also be vital: Hydrogen fuel refining also produces the explosive byproduct oxyhydrogen, which can be safely disposed of in the two-step process.

"The most important aspect to develop is the efficiency of solar-to-chemical energy conversion by photocatalysts," Domen said. "If it is improved to a practical level, many researchers will work seriously on the development of mass production technology and gas separation processes, as well as large-scale plant construction. This will also change the way many people, including policymakers, think about solar energy conversion, and accelerate the development of infrastructure, laws, and regulations related to solar fuels."

Where it lives: Seabeds in the northeast Atlantic, from the Mediterranean to northern Norway

What it eats: Organic matter filtered from the water and small invertebrates.

Why it's awesome: Green spoonworms are named for their spoon-shaped proboscis — a long,sucking mouthpart used for feeding — which stretches out into the water to catch food floating by.

"They basically look like a tentacle monster from a sci-fi film," Trond Roger Oskars, a research scientist specializing in marine invertebrates at Møreforsking Research Institute, told Live Science in an email.

The rest of their thick, sausage-shaped body remains buried in the seafloor — sometimes in burrows created by other animals — while their ribbon-like proboscis flutters in the water to fish for tiny pieces of organic matter to eat, including algae, rotten materials and even poop. "They're like vacuum cleaners sweeping over the ocean floor," Oskars said.

While green spoonworms' bodies are around 6 or 7 inches (15 to 18 centimeters) long, "that wavy proboscis can extend up to 10 times longer," he said.

Their iconic bright green color, which comes from a toxic pigment called bonellin, warns predators to stay away. But not all green spoonworms look like this. "Here's the twist!" Oskars said. "The green specimens you see are only the females."

The sex of an individual relies on chemistry rather than genetics. If a larva floats through the ocean and settles on the seafloor, it develops into a female. But if a larva lands on a female, it reacts to the bonellin in her body and turns into a male. Like some species of anglerfish, these males are microscopic and are absorbed into her body, becoming a parasite with the sole purpose of fertilizing her eggs. "It's basically reduced to a living testicle," he said.

Related: 'Parasitic provider of sperm on-tap': Why the sex lives of deep sea creatures demand extreme solutions

As well as protecting spoonworms from predators and turning males into living gonads, bonellin kills bacteria. "It is being targeted as a potential new antibiotic but may have a whole host of other interesting uses," Oskars said. "They are a prime example of why we need to know more about weird creatures and their habitats… We know only 10% of the species in the ocean, who knows what other creatures are hiding that have additional benefits?"

There are currently 118 known elements listed on the periodic table; from hydrogen, which has a single proton in its nucleus, all the way up to oganesson, which was officially named in 2016 and has at least 294 subatomic particles packed into the centers of its atoms (118 protons and at least 176 neutrons).

However, researchers know that, theoretically, there should be even heftier elements in the cosmos — and they have even predicted what these elements will look like and how they'll act. But to find them, we either have to discover new ways to synthesize them on Earth or scour the solar system for their potential whereabouts.

The two most promising potential element candidates are element 119, tentatively named ununennium, and element 120, aka unbinilium. These elements are so massive that they do not fit in any of the seven rows that make up the periodic table. If they are created, they will be added to a new eighth row on the iconic chart. However, neither has been synthesized, despite multiple attempts.

Related: Why are rare earth elements so rare?

In a new study, published Oct. 21 in the journal Physical Review Letters, researchers demonstrated a new technique for creating the superheavy element livermorium (element 116) by bombarding plutonium-244, an isotope of plutonium with extra neutrons, with vaporized ions, or charged atoms, of titanium.

The researchers think the same technique can be used to create unbinilium, by shooting titanium ions at isotopes of californium, which is heavier than plutonium. The new study is an important proof of concept that will allow the scientists to step up their search for the hypothetical element, they wrote.

"This reaction had never been demonstrated before, and it was essential to prove it was possible before embarking on our attempt to make [element] 120," study lead author Jacklyn Gates, a nuclear scientist at Lawrence Berkeley National Laboratory (Berkeley Lab) in California, said in a statement. "Creation of a new element is an extremely rare feat. It's exciting to be a part of the process and to have a promising path forward."

However, it could be some time before the researchers can create unbinilium. In this study, it took over 22 days to create just two atoms of livermorium inside Berkeley Lab's 88-Inch Cyclotron machine, which was constantly shooting titanium ions at the plutonium isotope. However, it could take even longer for unbinilium to form.

"We think it will take about 10 times longer to make [element] 120 than [element] 116," study co-author Reiner Kruecken, a nuclear scientist at Berkeley Lab, said in the statement. "It's not easy, but it seems feasible now."

Normally, superheavy elements quickly break down once they are formed because they are highly unstable. However, researchers predict that once elements reach a certain size, they will reach an "island of stability" where they will remain intact considerably longer than current known superheavy isotopes.

Unbinilium is expected to reach this island of stability, meaning its creation would open up a range of possibilities for researching superheavy elements, the study authors said. However, there is also a chance that the hypothetical element will not behave as expected.

"When we're trying to make these incredibly rare elements, we are standing at the absolute edge of human knowledge and understanding, and there is no guarantee that physics will work the way we expect," study co-author Jennifer Pore, a nuclear scientist at Berkeley Lab, said in the statement.

Think you know the elements? Test your knowledge with our new periodic table quiz, and try to guess the names of all the elements in just 10 minutes.

The molecules in question violate Bredt's rule, which describes where certain types of bonds can occur within a class of 3D chemical compounds. Successfully synthesizing these "anti-Bredt" molecules, as described Nov. 1 in the journal Science, could help scientists make new kinds of medicine.

"If there's a rule that says something absolutely is impossible, then maybe you just haven't thought of the right way of solving it. And if you do it, it actually might not be as difficult as you think," study first author Luca McDermott, an organic chemist at UCLA, told Live Science.

The anti-Bredt molecules fall into a class of compounds known as olefins. Olefins have at least one double bond — a strong chemical bond made from two pairs of electrons — connecting two carbon atoms. Each of those carbon atoms usually lies in the same 2D plane as the other atoms to which it's bonded.

Early in the 20th century, German chemist Julius Bredt studied double bonds in bicyclic molecules, a group of chemicals that contain two ring-shaped structures stuck together. To get an idea of the shape of these bicyclic molecules, imagine folding two five-sided sticky notes in half and sticking them together back to back. You'd end up with a roughly Y-shaped 3D structure.

Related: Inside the 20-year quest to unravel the bizarre realm of 'quantum superchemistry'

Bredt's rule, based on his observations in the laboratory, states that the carbon atoms at the junctions of that "Y" — otherwise known as the bridgehead position — can't have a double bond. Since the bridgehead carbon and its surrounding atoms don't all lie in the same plane, Bredt predicted that introducing a double bond at the bridgehead position would make the molecule too unstable to exist.

Now, McDermott and his colleagues have come up with a way to make anti-Bredt olefins and used the method to synthesize complex 3D molecules. Because the anti-Bredt olefins are unstable and highly reactive, the team wasn't able to isolate them directly in the new study. Instead, they added other molecules that could immediately react with the anti-Bredt olefins and form more stable products. That allowed them to experiment with several different variations on anti-Bredt olefins and their more stable products.

Reactions using anti-Bredt olefins could open doors to new types of medicines, study co-author Neil Garg, a professor and chemist at UCLA, told Live Science. The rigid, 3D structures could interact better with proteins in the body than existing flat medicinal compounds, he suggested.

The researchers said they plan to synthesize more compounds with unusual structures and explore new types of reactivity in the future.

"If we can question [Bredt's rule] after 100 years and push the limits of it, there's probably all sorts of other rules that are waiting to be reexamined," Garg said.

The molecule, called pyrene, is made up of four fused planar rings of carbon. It's therefore categorized as a polycyclic aromatic hydrocarbon (PAH) — one of the most abundant complex molecules in the visible universe. PAHs were first detected in the 1960s, in meteorites known as carbonaceous chondrites, which are remnants from the primordial nebula that formed our solar system.

"One of the big questions in star and planet formation is how much of the chemical inventory from that early molecular cloud is inherited and forms the base components of the solar system?" Brett McGuire, an assistant professor of chemistry at the Massachusetts Institute of Technology, said in a statement.

PAHs are thought to make up roughly 20% of the carbon found in space and are present at different stages in the life of stars, from their formation to their death. Their stability and resilience to ultraviolet (UV) radiation makes them likely to survive even in the harsh conditions of deep space.

Related: Most of Earth's meteorites may have come from the same 3 spots

The researchers say they began searching for pyrene and other PAHs in the Taurus cloud after pyrene was found in high levels in samples collected from the near-Earth asteroid Ryugu. Finding these molecules in the birthplace of our solar system provides a direct link astronomers have long been searching for.

"What we're looking at is the start and the end, and they're showing the same thing," said McGuire. "That's pretty strong evidence that this material from the early molecular cloud finds its way into the ice, dust and rocky bodies that make up our solar system."

The discovery was made using radio astronomy, a major subfield of astronomy that observes celestial objects, such as stars, planets, galaxies and clouds of dust, in the radio spectrum. By studying the radio waves originating from these sources, astronomers can learn about the compositions, structures and motions of particular targets.

Compared to other instruments used to identify molecules in space, radio telescopes offer the ability to observe individual molecules as opposed to general molecular groups. They do this by detecting the unique "fingerprints" of electromagnetic radiation a molecule emits or absorbs at specific frequencies where each molecule has a distinct set of rotational and vibrational energy levels. Characteristic radio waves are generated when the molecule transitions between these levels.

"This is now the seventh individual PAH identified in space since we first found one in 2021," said Ilsa Cooke, assistant professor in the UBC department of chemistry. "[PAHs] have similar chemical structures to the building blocks of life. By learning more about how these molecules form and are transported in space, we learn more about our own solar system and so, the life within it."

The astronomers estimated that pyrene accounted for about 0.1% of the carbon found in the cloud. "That is an absolutely massive abundance. An almost unbelievable sink of carbon. It’s an interstellar island of stability," said McGuire.

What was even more intriguing to the team, aside from finding pyrene in the origin place of our solar system, is the fact that the temperatures of the cloud were measured to be only 10 Kelvin (-263 degrees Celsius). On Earth, PAHs are formed during high temperature processes, namely through the combustion of fossil fuels. Finding them in this cold environment was therefore surprising. "Future work aims to explore whether PAHs can form somewhere that’s extremely cold, or whether they arrive from elsewhere in the universe, potentially via the death throes of an old star," said Cooke.

Originally posted on Space.com.

Another essential part of a cell is the membrane that encloses it. Proteins embedded on the surface of the membrane control the movement of substances in and out of the cell. This sophisticated membrane structure allowed for the complexity of life as we know it. But how did the earliest, simplest cells hold it all together before elaborate membrane structures evolved?

In our recently published research in the journal Science Advances, my colleagues from the University of Chicago and the University of Houston and I explored a fascinating possibility that rainwater played a crucial role in stabilizing early cells, paving the way for life's complexity.

The origin of life

One of the most intriguing questions in science is how life began on Earth. Scientists have long wondered how nonliving matter like water, gases and mineral deposits transformed into living cells capable of replication, metabolism and evolution.

Chemists Stanley Miller and Harold Urey at the University of Chicago conducted an experiment in 1953 demonstrating that complex organic compounds — meaning carbon-based molecules — could be synthesized from simpler organic and inorganic ones. Using water, methane, ammonia, hydrogen gases and electric sparks, these chemists formed amino acids.

Scientists believe the earliest forms of life, called protocells, spontaneously emerged from organic molecules present on the early Earth. These primitive, cell-like structures were likely made of two fundamental components: a matrix material that provided a structural framework and a genetic material that carried instructions for protocells to function.

Over time, these protocells would have gradually evolved the ability to replicate and execute metabolic processes. Certain conditions are necessary for essential chemical reactions to occur, such as a steady energy source, organic compounds and water. The compartments formed by a matrix and a membrane crucially provide a stable environment that can concentrate reactants and protect them from the external environment, allowing the necessary chemical reactions to take place.

Related: How fast does evolution happen?

Thus, two crucial questions arise: What materials were the matrix and membrane of protocells made of? And how did they enable early cells to maintain the stability and function they needed to transform into the sophisticated cells that constitute all living organisms today?

Bubbles vs. droplets

Scientists propose that two distinct models of protocells — vesicles and coacervates — may have played a pivotal role in the early stages of life.

Vesicles are tiny bubbles, like soap in water. They are made of fatty molecules called lipids that naturally form thin sheets. Vesicles form when these sheets curl into a sphere that can encapsulate chemicals and safeguard crucial reactions from harsh surroundings and potential degradation.

Like miniature pockets of life, vesicles resemble the structure and function of modern cells. However, unlike the membranes of modern cells, vesicle protocells would have lacked specialized proteins that selectively allow molecules in and out of a cell and enable communication between cells. Without these proteins, vesicle protocells would have limited ability to interact effectively with their surroundings, constraining their potential for life.

Coacervates, on the other hand, are droplets formed from an accumulation of organic molecules like peptides and nucleic acids. They form when organic molecules stick together due to chemical properties that attract them to each other, such as electrostatic forces between oppositely charged molecules. These are the same forces that cause balloons to stick to hair.

One can picture coacervates as droplets of cooking oil suspended in water. Similar to oil droplets, coacervate protocells lack a membrane. Without a membrane, surrounding water can easily exchange materials with protocells. This structural feature helps coacervates concentrate chemicals and speed up chemical reactions, creating a bustling environment for the building blocks of life.

Thus, the absence of a membrane appears to make coacervates a better protocell candidate than vesicles. However, lacking a membrane also presents a significant drawback: the potential for genetic material to leak out.

Unstable and leaky protocells

A few years after Dutch chemists discovered coacervate droplets in 1929, Russian biochemist Alexander Oparin proposed that coacervates were the earliest model of protocells. He argued that coacervate droplets provided a primitive form of compartmentalization crucial for early metabolic processes and self-replication.

Subsequently, scientists discovered that coacervates can sometimes be composed of oppositely charged polymers: long, chainlike molecules that resemble spaghetti at the molecular scale, carrying opposite electrical charges. When polymers of opposite electrical charges are mixed, they tend to attract each other and stick together to form droplets without a membrane.

The absence of a membrane presented a challenge: The droplets rapidly fuse with each other, akin to individual oil droplets in water joining into a large blob. Furthermore, the lack of a membrane allowed RNA — a type of genetic material thought to be the earliest form of self-replicating molecule, crucial for the early stages of life — to rapidly exchange between protocells.

My colleague Jack Szostak showed in 2017 that rapid fusion and exchange of materials can lead to uncontrolled mixing of RNA, making it difficult for stable and distinct genetic sequences to evolve. This limitation suggested that coacervates might not be able to maintain the compartmentalization necessary for early life.

Compartmentalization is a strict requirement for natural selection and evolution. If coacervate protocells fused incessantly, and their genes continuously mixed and exchanged with each other, all of them would resemble each other without any genetic variation. Without genetic variation, no single protocell would have a higher probability of survival, reproduction and passing on its genes to future generations.

But life today thrives with a variety of genetic material, suggesting that nature somehow solved this problem. Thus, a solution to this problem had to exist, possibly hiding in plain sight.

Rainwater and RNA

A study I conducted in 2022 demonstrated that coacervate droplets can be stabilized and avoid fusion if immersed in deionized water — water that is free of dissolved ions and minerals. The droplets eject small ions into the water, likely allowing oppositely charged polymers on the periphery to come closer to each other and form a meshy skin layer. This meshy "wall" effectively hinders the fusion of droplets.

Next, with my colleagues and collaborators, including Matthew Tirrell and Jack Szostak, I studied the exchange of genetic material between protocells. We placed two separate protocell populations, treated with deionized water, in test tubes. One of these populations contained RNA. When the two populations were mixed, RNA remained confined in their respective protocells for days. The meshy "walls" of the protocells impeded RNA from leaking.

In contrast, when we mixed protocells that weren't treated with deionized water, RNA diffused from one protocell to the other within seconds.

Inspired by these results, my colleague Alamgir Karim wondered if rainwater, which is a natural source of ion-free water, could have done the same thing in the prebiotic world. With another colleague, Anusha Vonteddu, I found that rainwater indeed stabilizes protocells against fusion.

Rain, we believe, may have paved the way for the first cells.

Working across disciplines

Studying the origins of life addresses both scientific curiosity about the mechanisms that led to life on Earth and philosophical questions about our place in the universe and the nature of existence.

Currently, my research delves into the very beginning of gene replication in protocells. In the absence of the modern proteins that make copies of genes inside cells, the prebiotic world would have relied on simple chemical reactions between nucleotides — the building blocks of genetic material — to make copies of RNA. Understanding how nucleotides came together to form a long chain of RNA is a crucial step in deciphering prebiotic evolution.

To address the profound question of life's origin, it is crucial to understand the geological, chemical and environmental conditions on early Earth approximately 3.8 billion years ago. Thus, uncovering the beginnings of life isn't limited to biologists. Chemical engineers like me, and researchers from various scientific fields, are exploring this captivating existential question.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

The periodic table of elements is a landmark categorization developed in 1869 by the Russian chemist and inventor Dmitri Mendeleev. It arranges all natural and synthetic elements by their atomic number , ranging from 1 to 118, grouping them by elements that look or behave similarly, such as metals or gases, while also giving each individual element its own chemical symbol.

In this periodic table of elements quiz, you have 10 minutes to name as many elements as you can, given only their symbol, atomic weight and the broad group they live in. It's no mean feat, the best we got was 57, a little under half — can you do better? Make sure you login to add your name to the leaderboard, and if you need a hint, tap the lightbulb in the top left corner.

Related: Inside the 20-year quest to unravel the bizarre realm of 'quantum superchemistry'

More science quizzes

—Black hole quiz: How supermassive is your knowledge of the universe?

—Constellations quiz: Can you name all the animals, objects and mythological figures hiding in the night sky?

—Moon landing quiz: How quickly can you name all 12 Apollo astronauts that walked on the moon?

—Equator quiz: Can you name the 13 countries that sit on Earth's central line?

The video was part of a new study, published Sept. 27 in the journal PNAS, in which researchers tested how palladium catalyzes a reaction between hydrogen and oxygen gases to create water in standard lab conditions. The team studied this reaction with a new type of monitoring apparatus that captured the process in extraordinary detail.

"We think it might be the smallest bubble ever formed that has been viewed directly," study lead author Yukun Liu, a materials scientist at Northwestern University in Illinois, said in a statement. "Luckily, we were recording it, so we could prove to other people that we weren't crazy."

The team induced the reaction using a special ultra-thin glassy membrane that holds gas molecules within honeycomb-shaped "nanoreactor" chambers. This means the tests can be viewed in real time using electron microscopes, enabling the researchers to learn more about how the reaction works.

Researchers from the Northwestern University Atomic and Nanoscale Characterization Experimental Center (NUANCE) pioneered this novel technique in a study published in January.

Related: New reactor could more than triple the yield of one of the world's most valuable chemicals

Researchers have known since the 1900s that palladium, a silver-white rare metal similar in appearance to platinum, can catalyze a dry reaction between hydrogen and oxygen, researchers wrote. However, until now, it was unclear exactly how the reaction worked.

The new study revealed that the gaseous atoms first squeeze between the palladium atoms, which are arranged in a square lattice. This expands the lattice and enables water droplets to form on the catalyst's surface. The team also found that the process can be sped up by adding hydrogen atoms to the palladium first, because they are smaller than oxygen atoms. This enables the palladium lattice to expand before the oxygen is added, creating bigger gaps for the larger atoms to fit more readily inside.

The team believes that a scaled-up version of the reaction could be used to create water for astronauts in space or in colonies on other planets. The researchers compared it to a scene from the sci-fi film "The Martian" starring Matt Damon, in which a stranded astronaut makes water on Mars by burning rocket fuel and combining it with oxygen from his suit.

"Our process is analogous, except we bypass the need for fire and other extreme conditions," study co-author Vinayak Dravid, director of the NUANCE Center, said in the statement. "We simply mixed palladium and gases together."

Palladium is an expensive and rare material, costing upwards of $1,000 per ounce. This is largely because it can catalyze many other chemical reactions and is used in a wide range of technologies. As a result, creating a water-generating device for astronauts could be extremely costly.

However, the researchers argued that it would be worth the expense in the long run.

"Palladium might seem expensive, but it's recyclable," Liu said. "Our process doesn't consume it. The only thing consumed is gas, and hydrogen is the most abundant gas in the universe."

David Baker, a professor of biochemistry at the University of Washington, received half of the 11 million Swedish krona ($1.06 million) prize for his work on computational protein design — a tool that enables researchers to design and create completely novel protein structures with properties unlike any found in nature.

The second half of the prize was shared between Demis Hassabis and John Jumper, respectively the CEO and director of Google DeepMind, for their work on protein structure prediction. The AI-powered program AlphaFold2, released in 2021, can predict the three-dimensional structure of any protein from the amino acid sequence encoded in DNA, revolutionizing our understanding of how proteins and molecules in living systems interact with each other.

"Proteins are the molecules which enable life," Heiner Linke, chair of the Nobel Committee for Chemistry, said during the announcement ceremony in Sweden this morning (Oct. 9).

A protein has tens of thousands of individual atoms, and its specific function is determined by the precise positions of these atoms, with links and folds between the different parts of the molecule creating a unique 3D shape. "To understand how life works, we first need to understand the shape of proteins," Linke said.

Protein molecules are formed from many individual units called amino acids, which are encoded by three "letter" DNA sequences. It should therefore be possible to predict the 3D structure of a particular protein from this sequence of amino acids. But this problem has been frustrating scientists for decades because there are many possible ways for proteins to fold.

In 2020, Hassabis and Jumper finally cracked this code by developing a program called AlphaFold2, which boosted the accuracy of structure predictions from 40% to 90%. The AI program was trained on a database of protein sequences and protein structures and looks for correlations between the positions of amino acids across thousands of examples. The system then iteratively refines these results down to a single predicted 3D structure.

In the years since it was released, this tool has dramatically improved our understanding of thousands of protein-mediated processes, including antibiotic resistance, and it is now possible to mine these databases for proteins with previously unknown functions, such as plastic-degrading enzymes.

Protein design approaches this same problem from the opposite direction, enabling researchers to visualize the ideal 3D protein structure for a particular function and work backward to calculate the amino acid sequence needed to synthesize it. In 2003, Baker developed a computer program called Rosetta that combines shorter amino acid fragments from an existing database, successively tweaking and optimizing the sequence to match the required 3D shape.

"David Baker opened up a completely new world of protein structures," Johan Åqvist, a member of the Nobel Committee for Chemistry, said during the announcement. "It's only your imagination which sets the limit for what you can do here." Rosetta has since helped to design hundreds of new proteins with diverse applications, ranging from inhibiting the COVID spike protein to acting as biological sensors for opioids in the environment.

Speaking to The Royal Swedish Academy of Sciences Secretary General Hans Ellegren following the prize announcement, Baker said he felt "very excited and very honored" and had been "really deeply inspired by others in the field and people I've worked with."

Soap has a pretty simple formula and a long history. But for centuries, water was the primary means of bathing. For example, in the Indus Valley Civilization — a culture that thrived in parts of what is now Pakistan, India and Afghanistan from 2600 to 1900 B.C. — the Great Bath in Mohenjo-daro is considered one of the earliest public baths for steam bathing. But steam only goes so far.

Before soap became mainstream in personal hygiene, "there would have been a lot of people who smelled really badly," Judith Ridner, a historian at Mississippi State University who writes about material culture, told Live Science.

Although modern formulations of soap contain many extra ingredients, basic soap is a fairly simple concoction. It's a salt of a fatty acid, meaning a combination of an alkali — a water-soluble compound — and a fat, Kristine Konkol, a chemist at Albany State University, told Live Science. As a chemical compound, a soap molecule has a water-loving head and a grease- and oil-loving carbon chain tail that surrounds and lifts up dirt molecules, Konkol explained.

This basic formula was key to premodern soaps in ancient civilizations. Plants; animal bile; oils; and exfoliants, like sand and wood ash, were all staple ingredients of these early cleansers.

Related: How does soap kill germs?

Ancient forms of soap are hard for historians to trace because of one major barrier: "Soap degrades," said Seth Rasmussen, a chemist historian at North Dakota State University. "We can use chemical dating and archaeology, but that requires that samples have survived since when they were first produced until now."

The earliest written records of soap-like substances date to around 2500 B.C. in Mesopotamia. Clay tablets indicate that the Sumerians used water and sodium carbonate — a powdery salt such as from plant ash — to clean themselves and beer and hot water to clean wounds.

A couple hundred years later, the Akkadian Empire in the Mesopotamian region used a mixture of plants, such as date palm, pine cone and a shrubby plant called tamarisk. Such a mixture is consistent with the basic ingredients of modern-day soap: an alkali, such as tamarisk; an oil, such as date palm; and an abrasive, such as pine cone, Konkol and Rasmussen explained in their paper on soap in antiquity.

Indeed, "there isn't actually that much difference between modern soap and ancient soap," Ridner said.

How is that possible when modern science didn't exist in ancient times? People probably created soap unintentionally, Konkol said. Cleaning a greasy pan with plant ash under high heat would produce soap, for example, as would boiling animal fats with wood ash. Historians have traced these methods back to Babylon and ancient Egypt. Natron (a type of salt), clay and the talc-based soapstone are other ingredients that have been documented in Egyptian remains, possibly as part of their bathing routines — or, more grimly, as a chemical result of decomposing bodies, Rasmussen said.

A different approach

The ancient Greeks and the Romans took a slightly different approach to bathing. After rinsing in water, they lathered themselves in scented olive oils. Then, they used a curved tool called a strigil to scrape off the remaining grime. But this may not have been a cleaning technique so much as a masking one, Rasmussen said.

"Oftentimes, the oils would have plant extracts in them that would be aromatic," he said. "So in these time periods, oils were used as perfumes."

Most of these soapy mixtures were used to clean textiles rather than human bodies. "It was really more of an industrial process than it was a cleanliness issue," Rasmussen said.

Historians aren't quite sure when bathing with soap became more routine, but in the Western world, it wasn't until much later — likely the early- to mid-1800s, Ridner estimated.

"It's a whole convergence of factors that are causing it," she said. For one, inexpensive fats became more widely available, Ridner said. Then, the industrial revolution moved soap production from households to factories. City engineers and reformers also turned toward "cleaning up" immigrant communities, which also facilitated the shift. Plus, the Civil and Crimean wars placed a bigger emphasis on sterilization in hospitals and health care.

"It's kind of all these factors coming together to create a mass market for soap that companies, like Procter & Gamble in the U.S., start to take advantage of," Ridner said.

But, as its name suggests, stainless steel doesn't seem to rust. So what's its secret?

Put simply, the chemistry of stainless steel keeps oxygen in the air and environment from reaching the iron in steel, preventing the harmful oxidation reaction.

Regular steel rusts when iron chemically reacts with oxygen to form iron oxide. Although rust generally isn't harmful to humans, it can drastically corrode iron and make it unsafe and ugly.

Related: Why does metal squeak?

Regular steel is an alloy of 99% iron and between about 0.2% and 1% carbon, while stainless steel typically contains between 62% and 75% iron, up to 1% carbon, and more than 10.5% chromium. Stainless steel also usually contains a few percent of nickel, which can make it both tougher and easier to work with.

The chromium is key to stainless steel's rust resistance, materials scientist Tim Collins, secretary-general of Worldstainless, a Belgium-based nonprofit allied with the World Steel Association industry group, told Live Science.

Chromium reacts with oxygen in the environment — usually in the air, but also underwater — to create a "passive layer" of chromium oxide (Cr2O3) on the metal's surface. This layer prevents the oxygen from reaching iron in the steel to create rust, Collins explained.

The passive layer on stainless steel is only a few nanometers thick and thus invisible, he said. The layer of chromium oxide can also self-heal if it is damaged; it is inert, which means it doesn't chemically react with other substances; and it doesn't leach out beyond the surface of the metal, which makes stainless steel suitable for food production, surgery and other applications, Collins added.

Accidental discovery

Modern stainless steel was developed in 1912 by English metallurgist Harry Brearley, who was studying steel alloys to prevent corrosion in gun barrels.

Brearley created an alloy from iron, carbon, chromium and nickel. But it wasn't suitable for a gun barrel, so he threw it in his backyard, Collins said. A few weeks later, Brearley noticed the shiny alloy in his yard hadn't rusted — so he developed the material and introduced it to the world in 1915.

Collins said rustproof stainless steel now makes up about 4% of the steel used worldwide each year — almost 2 billion tons.

But stainless steel is complex and expensive to make — typically between three and five times the production cost of regular steel — and the inclusion of special metallic elements in the alloys (such as molybdenum for underwater applications) can make it more expensive still.

As a result, most applications that need steel use regular or carbon steel, either in conditions where it doesn’t rust or where it is protected by an outer layer of paint or some other coating.

Yet stainless steel is now used for more applications than ever, Collins said, including in food production and food safety.

Johns Hopkins University food scientist Kantha Shelke told Live Science that stainless steel has many advantages over the alternatives: it is resistant to corrosion from food acids and cleaning chemicals — unlike aluminum and copper — and doesn’t contaminate or taint any food that it touches.

Stainless steel is also durable, stronger than aluminum, and hygienic, with a non-porous surface that can be easily cleaned and sanitized, she wrote in an email.

"There's a lot of processes that go on," Wes Osburn, an associate professor of meat science at Texas A&M University, told Live Science. "It goes through a pretty complex series of chemical reactions."

One of these processes is called protein gelation. Proteins are structurally important in meats. They play a key role in holding water and in changing the texture of meat as it gets cooked. Meat proteins are divided into three main groups: myofibrils, which are the most abundant; sarcoplasmic proteins; and connective tissues, including collagen. When meat is heated, bonds within proteins are broken in a process called protein denaturation, which causes proteins to unfold and lose their shape.

Myofibrillar proteins begin to denature at around 104 to 158 degrees Fahrenheit (40 to 70 degrees Celsius). As heat continues to be applied, these proteins refold and form a "gel" — a 3D protein network that traps water and causes a slab of meat to firm up. The process is similar to building a structure with Tinkertoy dowels and spools, Osburn said.

"The more sticks that I can put into the wheel, and that's put into another wheel, the stronger, the firmer the texture is," he explained.

Related: When did humans start cooking food?

If heated too much, meat becomes too tough and dry, but continued heating will break down more proteins and cause the meat to become tender again. When heated above around 160 F (71 C) for a prolonged period, collagens also form a gel, giving slow-cooked meat its silky texture.

But what helps give cooked meat its signature savory, caramelized flavor is a series of chemical reactions collectively known as the Maillard reaction, which occurs when amino acids interact with sugars at temperatures above about 285 F (141 C). The Maillard reaction gives rise to hundreds of new flavor and aroma compounds. In terms of aroma alone, researchers have identified more than 880 compounds in cooked beef.

In another series of reactions, red meat changes color based on the transformation of a protein called myoglobin. Myoglobin remains partially intact when meat is cooked at lower degrees of doneness, giving it a pink or red color. But at around 170 F (77 C), the protein denatures completely, which turns the meat brown.

The rate and extent of chemical reactions that occur in meat change based on the cooking method, cooking length and temperature, Saleh Al-Ghamdi, an assistant professor and head of the Department of Agricultural Engineering at King Saud University in Saudi Arabia, told Live Science in an email. Dry-heat cooking methods — such as searing, roasting or grilling — enhance the Maillard reaction. Moist-heat cooking methods, like braising or stewing, tend to slow or stop the reaction. Flavor also changes based on a variety of other factors, including the ​​breed, sex, diet and age Al-Ghamdi said. Meat aging, or the practice of waiting to cut uncooked meat, and stress of the animal at death can affect the flavor and tenderness too.

"A lot of it just depends upon the composition of the meat," Osburn said. "How much fat, water, protein is there? How much connective tissue is there? What's the pH? And then, how do you cook the product?"

Understanding which chemical reactions take place can help chefs determine which cooking method is best for certain cuts of meat. Beef chuck, for example, would be best cooked "low and slow" with a moist-heat cooking method. Chuck comes from a cow's shoulder and has a lot of collagen because it has been heavily used throughout the animal's life. Tenderloin, a long and lean muscle from the cow's back, would be best cooked more quickly with a dry-heat method to facilitate the Maillard reaction.

The new reactor, described Aug. 12 in the journal Nature Catalysis, produces ammonia gas from water contaminated with nitrate ions.

Ammonia (NH3) is an extremely important industrial chemical. It is one of the key components in fertilizers and also vital in chemical manufacturing processes. Over 180 million tons (163 million metric tons) are produced annually, mostly by the 100-year-old Haber-Bosch process, a high temperature-high pressure reaction between hydrogen and nitrogen. This one chemical reaction alone uses approximately 2% of the world's energy, according to the study.

Nitrate, on the other hand, pollutes rivers and streams when excess runoff from fertilized farmland enters local waterways. Nitrates devastate aquatic ecosystems, and at higher levels in drinking water can pose health risks. To be safe to drink, water must be thoroughly treated to remove nitrates.

Existing commercial treatments use bacteria to convert nitrate ions directly to nitrogen, but this procedure is expensive and also produces nitrous oxide, which, pound for pound, is 265 times more potent as a greenhouse gas than carbon dioxide.

To avoid this climate impact, scientists are working on ways to convert nitrate into ammonia using electricity, but early systems have struggled with unwanted side reactions.

In these devices, there is a positive and negative end, with a difference in charge between the two. Chemical reactions occur at both. Water is split into oxygen gas and hydrogen ions at the negative end of the reactor, while a second reaction converts nitrates to ammonia and hydroxyl ions (OH-) at the positive end.

Unfortunately, hydrogen ions produced on one side tend to diffuse to the other, where they chemically react to form hydrogen. Because even highly polluted water still has tiny concentrations of nitrate, this hydrogen reaction winds up dominating and prevents the main nitrate-to-ammonia reaction from occuring efficiently. Scientists have tried to get around this by putting additives into the mix, but this is impractical for real-world applications in water treatment.

In the new study, the researchers got around this problem in part by adding an intermediate chamber, creating a three-chamber reactor, study first author Feng-Yang Chen, a researcher at Rice University in Texas, told Live Science in an email. In the first chamber, nitrate is converted into ammonia gas and hydroxyl ions. These combine with sodium ions already present in the water to form sodium hydroxide. As the cleaned water leaves the first chamber and is pumped into the middle chamber with this sodium hydroxide, the newly-formed ammonia gas is bubbled out. Meanwhile, in the third chamber, hydrogen ions produced by the splitting of water diffuse across the cell into the middle chamber. Here, hydrogen and hydroxyl ions from the sodium hydroxide combine to form water. The leftover sodium ions then move back from the middle chamber into the first chamber to repeat the cycle.

Crucially, no hydrogen ions reach the other side of the reactor to interfere with the nitrate reaction. In a 10-day test run, over 90% of the electric current in the research team's cell powered ammonia production, compared with around 20% for former systems.

Wang's design is still experimental and they still need to work out several issues before the technology can be rolled out commercially.

One of the big challenges is ensuring the reaction can still proceed in the presence of impurities, such as magnesium and calcium ions, that are often found in water, Chen said.

It turns out, it's all about the periodic shift between metal pieces sticking and slipping against one another. Metal's stiffness and density also make that squeak extra loud, experts told Live Science.

The mechanism behind metal squeaking is no different from the squeal of skidding tires or the squeak of a floorboard, Robert Hyers, a professor of mechanical and materials engineering at Worcester Polytechnic Institute in Massachusetts, told Live Science in an email.

"The squeaks are really periodic thumps," Hyers said. "If the thumps are close enough together, you perceive the high-frequency thumps as squeaks." In other words, when these thumps happen in quick succession, they emit a high-pitched squeaking sound.

This sticking occurs when lubricants on the metal, like oil or water, are "squeezed" out of the way during a moment of high contact stress, Yip-Wah Chung, a professor of materials science and engineering at Northwestern University, told Live Science in an email.

This slipping and sticking also occur when you drag your fingers down a glass window. While friction is key here, Hyers said it accounts only for the sticking part.

"It's the periodic alternation between sticking and slipping that makes the squeak," he said.

Slipping and sticking cause metal materials to vibrate and emit noise Chengzhi Shi, an associate professor of mechanical engineering at the University of Michigan, told Live Science in an email. You could think of this like plucking a guitar string. As the metal sticks and slips, it vibrates. The frequency and strength of the vibration also depend on the shape and material of the metal.

"It is the vibration modes of the metal excited by the friction that radiate the squeaking sound we hear," Shi said.

Related: Why does striking flint against steel start a fire?

While other materials also resonate in this way, metals are particularly noisy, Naresh Thadhani, a professor of materials science and engineering at Georgia Tech, told Live Science in an email.

"Metals are generally denser and have high stiffness, which provides them with certain acoustic properties that enhance sonic effects and sonority," Thadhani said. In other words, they create faster moving sound waves with higher amplitudes.

As for why the squeaking of a subway train is so much louder than the squeak of a door hinge, Thadhani said that greater pressure, speed and size cause louder screeches.

So can you do anything about it? "There are two ways to remove squeaking," Chung said. "One is to reduce the load on the contact. The other is to improve the lubrication."

For a squeaky door hinge, this might involve applying a lubricant, like WD-40, to reduce friction. However, sometimes you need the squeak: "The same additional friction that lets the trains stop and accelerate better also causes the squeak," Hyers said.

Removing this friction by lubricating a subway train's tracks might take away the train's horrible screech, but it could also set up the train for dangerous accidents. So be grateful the next time you hear the loud screech of a subway car.

Cecilia Payne-Gaposchkin

In her 1925 doctoral thesis, the astronomer Cecilia Payne-Gaposchkin proposed that stars are composed primarily of hydrogen and helium — an idea that revolutionized science but was initially met with skepticism. According to the American Museum of Natural History in New York City, Payne-Gaposchkin was renowned for her work on variable stars, and wrote several books. She was born in England in 1900, immigrated to the United States to study astronomy at Harvard College Observatory, and died in 1979.

Srinivasa Ramanujan

Born in Tamil Nadu, India, in 1887, mathematician Srinivasa Ramanujan caught the attention of British mathematician G. H. Hardy, with whom he collaborated and who sponsored his move to Cambridge in England. According to Encyclopedia Britannica, Ramanujan is best known for his work on number theory, infinite series and fractions, while several areas of his work — including elliptical functions and Riemann zeta functions — still inspire modern mathematical research. Ramanujan died in 1920 at the age of 32; his cause of death is debated.

Ellen Swallow Richards

In 1868, the pioneering American engineer and chemist Ellen Swallow Richards (1842-1911) became the first woman admitted to the Massachusetts Institute of Technology, where she earned a degree in chemistry. According to Cornell University, she is regarded as the founder of the field of home economics, which applied scientific principles to domestic life, and she is considered one of the first environmental engineers thanks to her groundbreaking research on water quality and sanitation.

Oliver Heaviside

Born in London in 1850, mathematician and physicist Oliver Heaviside made developments in electromagnetic theory. These include work on transmission lines that advanced long-distance telephony and his prediction of a layer of Earth's ionosphere — sometimes called the Heaviside layer, or the Kennelly-Heaviside layer — that reflected some radio waves and allowed radio broadcasts around Earth's curvature. Heaviside died after falling from a ladder in 1925.

Dorothy Hodgkin

British chemist Dorothy Hodgkin is renowned for her pioneering work in X-ray crystallography and her development of methods for determining molecular structures using X-ray diffraction. Among other compounds, she researched the structures of drugs such as penicillin and insulin, which had significant implications for medicine and biochemistry. Hodgkin was born in Cairo, Egypt, in 1910; won the Nobel Prize in chemistry in 1964; and died in the U.K. in 1994.

Matilda Moldenhauer Brooks

Born in 1890, Matilda Moldenhauer Brooks was an American cellular biologist who made important contributions to toxicology. They include her 1932 discovery that the dye methylene blue, which is commonly used to stain organic samples in biology, can also act as an antidote to poisoning by carbon monoxide and cyanide. She was also an advocate for the role of women in science and faced challenges in securing a research position at the University of California because her husband, Sumner Cushing Brooks, was also a researcher there and anti-nepotism policies prevented her appointment. She died in 1981.

Nettie Stevens

The American geneticist Nettie Stevens was one of the first scientists to identify sex chromosomes. Her studies of mealworms showed that males produced two distinctive types of sperm, which always resulted in either male or female offspring; and her meticulous research showed the presence of X or Y sex chromosomes in the sperm. Her work laid the foundation for the modern understanding of the X-Y sex determination system, which is now a cornerstone of genetics. Stevens was born in Cavendish, Vermont in 1861 and died in Baltimore in 1912.

Ashoke Sen

Indian theoretical physicist Ashoke Sen is a pioneer of string theory and noted for his contributions to quantum field theory and black hole entropy. Sen was born in Kolkata in 1956 and has studied in the United States and the United Kingdom; his research has laid the foundations for explorations into the fundamental nature of the universe. He now lives and teaches in Bangalore, where he is a leading voice in the pursuit of a unified theory of everything.

Hermann Minkowski

Mathematician Hermann Minkowski is most famous for developing a geometric interpretation of Einstein's theory of special relativity. Among his other innovations, he proposed the idea of space-time, which combines the three physical dimensions of space with the fourth dimension of time into a unified mathematical framework. He also made important contributions to number theory and the geometry of numbers. Minkowski was born in Lithuania in 1864, when it was still part of the Russian Empire, and died in Germany in 1909 at the age of 44.

Prahalad Chunnilal Vaidya

Indian physicist and mathematician Prahalad Chunnilal Vaidya (1918-2010) made important contributions to general relativity, including a solution to Einstein's field equations that describes the gravitational field of a radiating star; earlier solutions had assumed only a nonradiating mass. He also contributed to the professional advancement of science in India after its independence from Britain in 1947, which included forming the Indian Association for General Relativity and Gravitation and leading the Indian Mathematical Society.

Maurice Hilleman

American microbiologist Maurice Hilleman (1919-2005) was a pioneer of vaccinology and is thought to have saved millions of lives. In the 1950s, while working for the U.S. Army, he identified the mechanisms by which influenza viruses mutate, which allowed the creation of better vaccines and prevented the possible outbreak of flu pandemics. He also developed vaccines for hepatitis B and meningitis, and his vaccines for measles, mumps and rubella were combined into a single injection, known as the MMR vaccine, to simplify childhood immunizations.

Emmy Noether

German mathematician Amalie "Emmy" Noether (1882-1935) made important contributions to abstract algebra, particularly in what are known as ring, field and group theories, which laid the foundations for modern algebra. Her "Noether's theorem" linked symmetries in physical systems with the principles of energy conservation and is now a cornerstone of physics. Noether was born in Germany but emigrated to the United States in 1933, after her university professorship, along with those of other Jews, was revoked by the Nazis.

Abdus Salam

Abdus Salam (1926-1996) was a Pakistani theoretical physicist who contributed to the scientific understanding of fundamental forces. One of his key achievements was the theory of the electroweak force, which combined the electromagnetic force and the weak nuclear force — a step toward a unified theory of everything. With his colleagues, Salam was awarded the 1979 Nobel Prize in physics for this work. Salam also championed scientific collaboration between countries and co-founded the International Centre for Theoretical Physics in Trieste, Italy, in 1964.

Saharon Shelah

Mathematician Saharon Shelah is a leading figure in model theory, which explores the relationships between logical structures and their interpretations, and set theory, which studies sets of mathematical objects and their properties. Shelah's work examines the foundations of mathematics — particularly the structure and properties of mathematical objects. He was born in Jerusalem in 1945; in 2001, he won the Wolf Prize, one of the most prestigious awards in mathematics.

Jagadish Chandra Bose

Indian polymath Jagadish Chandra Bose (1858-1937) is known for his contributions to the fields of physics, botany and biology. He invented an instrument called the crescograph, which can detect minute changes in plant tissues in response to fluctuations in light, temperature and other factors. His experiments in this field challenged the prevailing view of plants as passive entities and showed they were sensitive to their environments. He also conducted research into radio waves and independently achieved wireless transmission in 1895.

Aristarchus of Samos

Aristarchus of Samos was an ancient Greek mathematician and astronomer who lived from roughly 310 to 230 B.C. in the city-state of Samos. He is thought to be the first to develop the heliocentric model of the solar system, in which the planets orbit the sun. A few centuries after Aristarchus, however, most astronomers preferred the geocentric model, in which the sun and planets orbited the Earth; and that was the dominant theory until it was challenged in the 16th century A.D. by the Polish mathematician and astronomer Nicolaus Copernicus. Copernicus had developed his own heliocentric model, and seems not to have known about Aristarchus.

John Michell

No portrait survives of the early English scientist John Michell (1724-1793) but he made important contributions to several scientific fields, including astronomy and geology. Michell was a friend of the astronomer William Herschel and was the first to determine that double or "binary" stars were in fact orbiting each other. Before this, Herschel and other astronomers believed the many double stars they had seen were just tricks of alignment, and that one of the stars was much further behind the other. But Mitchel showed there were far too many observations of double stars than could occur at random. He also showed that star clusters like the Pleiades could not have occurred at random, which indicated the stars in such clusters shared a common origin. Michell was the first scientist to apply statistics to astronomy; statistical techniques are now a cornerstone of the field.

Daniel Hale Williams

Daniel Hale Williams (1858-1931) was a pioneer in modern medicine and an important Black American scientist. He performed the world's first successful heart surgery in 1893, by controlling the bleeding of a man who had been stabbed in a fight. Williams co-founded Provident Hospital in Chicago, which was the first Black-owned and -operated medical institution in the United States. He was a vocal critic of racial disparities in health care and co-founded the National Medical Association, a professional organization for Black doctors facing limitations in the medical community.

Mikhail Dolivo-Dobrovolsky

Mikhail Dolivo-Dobrovolsky was born in 1862 in Russia. He was an important electrical engineer and invented the first practical alternating-current (AC) induction motor that could easily convert electricity into mechanical power. Earlier AC motors were complex and unreliable, but Dolivo-Dobrovolsky's invention paved the way for the wide-scale adoption of national AC grids. He also designed transformers to vary AC voltage, which allowed it to be transmitted over long distances. In the 1890s, he helped build the world's first long-distance AC power transmission system between Frankfurt and Offenbach, Germany. He died in 1919.

Marguerite Perey

French nuclear chemist Marguerite Perey, born in 1909, was a student of the Polish-French physicist and chemist Marie Curie. She worked for many years as Curie's personal assistant at Curie's Radium Institute in Paris, where she learned how to isolate and purify radioactive elements. In 1935, while studying the radioactive element actinium, Perey discovered the 87th element of the periodic table, which she called "francium" after her home country. She'd hoped the radioactivity of francium would help diagnose cancer in patients, but in fact it was carcinogenic; Perey developed bone cancer and died in 1975.

Sofya Kovalevskaya

Sofya Kovalevskaya, born in 1850, was a Russian mathematician who made important contributions to mathematical methods of analysis, partial differential equations and mechanics. She was the first woman to obtain a modern doctorate and the first woman in Northern Europe to be appointed to a full professorship. Her most notable contribution was the development of the "Kovalevskaya top" — equations that describe a virtual spinning top within a gravitational field — thereby solving what was one of the most complex problems in classical mechanics. She lived in Sweden after the 1870s and died in 1891 at the age of 41.

Émilie du Châtelet

Émilie du Châtelet was an 18th-century French natural philosopher and mathematician who is best known for her translation of and commentary on Isaac Newton's 1687 book "Philosophiæ Naturalis Principia Mathematica," often called the "Principia." Her commentary made several contributions to Newtonian mechanics, including an additional conservation law for the kinetic energy of motion, and she developed new ideas about the relationship between energy and the mass and velocity of an object. Du Châtelet was born in 1706 and died in 1749 from complications during childbirth.

Hero of Alexandria

Hero (or Heron) of Alexandria was an engineer and mathematician who lived in Alexandria, Egypt, when it was ruled by the Romans in the first century A.D. He is credited with the invention of a steam-powered device called the aeolipile, or "Hero's engine," which featured a primitive steam turbine. He also developed the technology behind windmills — an important contribution to civilization. In mathematics, he is best remembered for Heron's formula, which is a way of calculating the area of a triangle using only the lengths of its sides.

Johann Rudolf Glauber

Born in 1604 in Karlstadt, Bavaria (which in 1871 became part of the German Empire), Johann Rudolf Glauber is considered one of the first chemical engineers, and his inventions often had commercial uses. He was the first to describe "chemical gardens," in which inorganic chemicals immersed in a sodium silicate solution appear to "grow" into complex structures. In 1625, Glauber discovered sodium sulfate, also known as "Glauber's salt," which is now a major chemical commodity used to make detergents and paper. He died in about 1670, possibly from poisoning by the chemicals he used in his work.

Ḥasan Ibn al-Haytham

Ḥasan Ibn al-Haytham, also known as Alhazen, was born in Basra, now in southern Iraq, in about A.D. 965. He lived mainly in Cairo, Egypt, until 1040, during the Islamic Golden Age. He is sometimes called "the father of modern optics" and made important discoveries in the field, including a theory of vision that argued, correctly, that it occurred in the brain. (Earlier theories had suggested light rays were emitted from the eyes.) He also studied reflections, refraction, and the nature of images formed from rays of light.

Norman Borlaug

American agricultural scientist Norman Borlaug (1914-2009) is known as "the father of the Green Revolution." His research contributed to global food production, and he spent decades developing disease-resistant strains of wheat that are now planted around the world. Borlaug also championed the transfer of farming technologies to developing nations, for which he was awarded the Nobel Peace Prize in 1970, and stressed the importance of population control to achieve long-term food security.

Annie Jump Cannon

Annie Jump Cannon (1863-1941) was a pioneering American astronomer nicknamed "the census taker of the sky" for her meticulous work classifying stars. She studied physics and astronomy at Wellesley College in Massachusetts and worked at Harvard College Observatory from the late 1890s, where she developed a classification method based on the spectra of stars that was first used by astronomer Edward Pickering. Cannon had exceptional eyesight and classified over 350,000 stars in her lifetime, sometimes at a rate of more than 5,000 stars a month. Her classification system played a crucial role in the development of the modern stellar classification system, which is based on a star's temperature and surface conditions.

Fritz Zwicky

Born in 1898 in Bulgaria to a Swiss father and a Czech mother, Fritz Zwicky emigrated to the United States in 1925 and studied astronomy at the California Institute of Technology. Zwicky developed many astronomical concepts, and with astronomer Walter Baade described neutron stars and supernovae — the powerful explosions of massive stars. His greatest contribution to science, however, was suggesting that galaxy-scale concentrations of what's now called dark matter — he called it "dunkle materie" in German — may be the cause of anomalies in the behavior of galaxies within galactic clusters and the orbital speeds of stars at the edges of galaxies. He died in 1974.

Subrahmanyan Chandrasekhar

Subrahmanyan Chandrasekhar (1910-1995) was an Indian-American astrophysicist who studied the evolution of stars. His most famous research resulted in his determination of what's now known as the Chandrasekhar limit, which is the point at which a star that has run out of fuel will collapse into a white dwarf. Each of these incredibly dense stellar remnants can be smaller than Earth but have a mass greater than that of the sun. His research expanded into the study of black holes, which initially were not widely accepted but now are regarded as both an important feature of astronomy and possible clues to the nature of the universe. Chandrasekhar shared the 1983 Nobel Prize in physics for his work on stellar evolution.

Ida Noddack

German chemist Ida Noddack (1896-1978) was the first woman to hold a professional position in Germany's chemical industry. Her most famous discovery, which she made with her husband Walter Noddack and collaborator Otto Berg, was their isolation in 1925 of the 75th element on the periodic table, a rare metal they named "rhenium" after the river Rhine. The element had been predicted decades earlier, and the discovery confirmed the theoretical structure of the periodic table. Noddack was also one of the first scientists to suggest that the nuclei of some elements bombarded with neutrons could split — a phenomenon now known as nuclear fission.

Eunice Foote

The 19th century American scientist and inventor Eunice Foote (1819-1888) carried out early research on the greenhouse effect, in which some atmospheric gases trap heat from the sun near Earth's surface. In 1856, she presented a paper at the annual meeting of the American Association for the Advancement of Science demonstrating the effect of the sun's rays on different gases and suggested this had taken place in Earth's atmosphere and affected its climate. But Foote, as a woman in the 19th century, was not permitted to read her own paper at the meeting, so a male professor read it on her behalf.

Kary Mullis

American biochemist Kary Mullis revolutionized molecular biology with his invention of the polymerase chain reaction (PCR) technique. He conceived the idea in the 1980s while working for an early biotechnology company. It allows the rapid amplification of specific DNA sequences within a controlled environment, sharply reducing the amount of starting DNA required and cutting the time needed for analysis. PCR can detect DNA from viruses, bacteria and genetic mutations, and it is now a cornerstone of medical diagnostics, genetics, forensics and archaeology. Along with Michael Smith, Mullis was awarded the 1993 Nobel Prize in chemistry for the invention. He was born in 1944 and died in 2019.

Last Chance Lake is a shallow, extremely salty pool of water with an unusual chemistry. The lake has phosphate concentrations 1,000 times higher than the ocean, making it a modern analog for conditions that may have given rise to life on Earth roughly 4 billion years ago.

Phosphate is an essential ingredient to make nucleotides — the building blocks of DNA and RNA — and other life-forming compounds, such as lipids. Although phosphate is bound up in every living being, the element by itself is scarce in nature.

"Someone coined the phrase 'the phosphate problem' for the origin of life, which is that you need a lot of phosphate for these reactions," Sebastian Haas, a postdoctoral researcher in the Department of Earth and Space Sciences at the University of Washington, told Live Science. "The second part of the problem is that phosphate is usually low in the environment, and the only real exception we know are these kinds of lakes."

Related: 'This is weird': Experts 'shocked' by record-breaking longevity of Death Valley's phantom lake

Last Chance Lake is one of several so-called "soda lakes" — lakes that have high levels of dissolved sodium and carbonate. That makes them similar to bowls of water containing large amounts of dissolved baking soda, hence the name. This chemical makeup enables these lakes to have high concentrations of phosphate.

In freshwater lakes, phosphate scarcely exists by itself because it binds to calcium to form calcium phosphate — an insoluble material. But in soda lakes calcium preferentially binds with carbonate and magnesium, freeing up phosphate.

"The high carbonate is sort of the key for the high phosphate in these lakes," said Haas, who led research into Last Chance Lake and neighboring Goodenough Lake for a study published in 2024 in the journal Communications Earth and Environment.

This high carbonate level, together with high sodium, results from a reaction between groundwater and volcanic rocks that sit beneath the lake, Haas said.

Last Chance Lake is particularly intriguing because it has the highest phosphate concentration of all known soda lakes. It's also much saltier, which makes it hard for life to exist there compared with other soda lakes, Haas said. The largest organisms his team recorded at the lake were brine flies (Ephydridae) and brine shrimp (Artemia), he said.

Last Chance Lake formed after the last ice age, which ended about 10,000 years ago, Haas said. Radiocarbon dating indicated the lake is at least 3,300 years old and fed only by tiny amounts of springwater and groundwater. Low input and high evaporation rates concentrate salts, including carbonate, in the lake's waters.

The harsh conditions at Last Chance Lake mimic an environment on early Earth where life may have originated. "We're definitely not claiming that life emerged at Last Chance Lake," Haas said. But "a similar lake may have plausibly existed 4 billion years ago somewhere on Earth, and we're using Last Chance Lake to understand what this environment would have looked like."

Billions of years ago, similar lakes may also have existed on other planets in our solar system, including Mars, according to the study.

Discover more incredible places, where we highlight the fantastic history and science behind some of the most dramatic landscapes on Earth.

It appears that this thick, sticky, sweet nectar owes its properties to chemicals imparted by its makers — honeybees. Astonishingly, there are at least 300 types of honey known today that are produced by more than 20,000 honeybee species.

"The composition of the honey depends on the type of honeybees," Kantha Shelke, a food scientist at Johns Hopkins University and founder of Corvus Blue LLC, a food science and nutrition research firm based in Chicago, told Live Science in an email. 

After collecting nectar from flowers, bees turn the sucrose, a complex mix of glucose and fructose, into highly concentrated simple sugars. While honey is mostly sugars, it also contains more than a dozen other substances, such as enzymes, minerals, vitamins and organic acids. Honey also contains flavonoid and phenolic compounds, which are known to be anti-inflammatory and antioxidants. These compounds are responsible for honey's medicinal properties. 

The multitude of chemicals that coalesce when honeybees create honey makes this natural sweetener inhospitable to microbes that usually spoil food. 

Honey's high sugar content makes it hygroscopic, meaning it can suck moisture from the environment, and even absorb the water from surrounding microbial cells. Honey also has a low level of available water in which microbes can grow. 

After turning flower nectar into simple sugars, bees regurgitate the sweet liquid and pass it on to other bees in the hive. As the nectar sits inside the bees' stomachs, glucose oxidase breaks down the glucose and turns it into gluconic acid and hydrogen peroxide. When the bees finally place and fan the digested nectar in the comb, water slowly evaporates and turns this sweet liquid viscous. 

Related: How do bees make honey? From the hive to the pot

The presence of gluconic, as well as acetic, formic, and citric acid, makes honey even more acidic than coffee. This pH range is lower than what most microbes can tolerate. And the hydrogen peroxide in honey may stop bacteria from forming a slimy network called biofilm that usually sticks to surfaces.

All of these chemicals stop microbes from degrading honey. But while honey remains safe to consume for a long period, it does change over time. 

"Honey constituents undergo changes because of crystallization, fermentation, oxidation, and thermal effects. The changes also depend on the type of honey (light or dark) and source, or region which vary with the season and the plants foraged by the honeybee," Shelke said. "Some of these changes influence the nutritional and sensory attributes including appearance."

When heated or stored for a long time, honey can undergo a Maillard reaction, the same chemical reaction that caramelizes sugar and turns it brown. As sugars become dehydrated, they produce a potentially toxic compound, 5-hydroxymethylfurfural (HMF). HMF is also found in many other food products including breakfast cereals, dried fruits and milk. 

The safe levels of HMF for daily consumption are still poorly understood. Some research has suggested HMF can fuel cancer, while others suggest the compound can prevent allergic reactions. The Codex Alimentarius Standard, an international standard on food safety, has set an upper limit of 40 mg/kg HMF for honey products. But this limit varies among the different types of honey. For instance, sunflower honey can reach this HMF limit after being properly stored for 18 months, while acacia honey takes about five years to reach the same amount of HMF.

Heating leads to HMF production, but cooling causes honey to crystallize. As honey cools, the sugar content becomes too saturated and unable to stay in solution. This can also happen when moisture escapes the honey during storage, causing the sugars to form crystals, Shelke said. 

According to one study, the sensory and chemical properties of honey are best preserved when stored at 75 degrees Fahrenheit (24 degrees Celsius), or around room temperature.

Because of all these variables, "handling and packaging can greatly affect the shelf life of honey," Shelke said. "Raw honey — with intact enzymes and other beneficial compounds — is minimally processed and can last 'forever' if stored in a sealed container."

Likewise, pasteurized honey can last several years. But because it lacks some of the enzymes and antimicrobial compounds, it may be susceptible to microbial damage if not sealed or stored properly, Shelke added. 

Of note, caretakers should avoid feeding honey to infants, because spores from the bacterium Clostridium botulinum can contaminate honey. These spores can withstand pasteurization temperatures. Once ingested, they can release a toxin into babies' intestines and cause infant botulism, a condition that can be fatal. The spores are generally harmless to adults as their mature digestive systems purge the toxin. 

This article is for informational purposes only and is not meant to offer medical advice.

The hope is that this additive could help prevent leaks while also reducing the risk of a dangerous condition called toxic shock syndrome, the researchers behind the product say.

The seaweed-derived material was unveiled in a study published Wednesday (July 10) in the journal Matter. Its developers believe the product could someday be used as an alternative filler in conventional pads or as a spill-proof lining to insert in menstrual cups. For now, though, the prototype has only been tested in early lab experiments.

"The way these products have worked for a long time is to absorb or retain menstrual fluid so that you can remove it later," said lead study author Bryan Hsu, a biomedical scientist at Virginia Tech. "But what if we could improve menstrual care by solidifying menstrual blood? If it's in a gel form, it's less likely to leak and spill."

Related: What causes spotting between periods?

A shortfall of conventional menstrual products is their risk of leaking. Even in developed nations, concerns around such leaks can contribute to children missing school during their periods; besides that, leaks are an inconvenience in that they can damage clothes.  

One reason leaks can occur is because, unlike blood from a vein, menstrual blood doesn't usually coagulate. "There are a lot of fibrinolytic enzymes [in period blood] which break down blood clots, as well as clumps of tissue and cells," Hsu told Live Science. "It's fundamentally a different type of blood." 

Hsu and his colleagues hypothesized that the right material could convert menstrual blood into a solid form that would be less likely to leak. Their solution: polysaccharides. These are chains of sugar molecules that thicken liquid solutions really well. Pectins, which are often used to thicken fruit preserves, and cornstarch are good examples of such molecules. 

Using pig's blood modified to prevent clots, the team tested naturally derived sugars to see which could turn it into a gel-like form. Their tests included xanthan gum, a common food additive, as well as alginate and kappa carrageenan, which are derived from seaweed.

"The advantages of using biomaterials like these are that they're biocompatible," meaning they don't harm living human tissue, "and completely biodegradable," Hsu said. "Single-use, disposable menstrual products contribute a ton of waste, so if we can replace some of the less-biodegradable components, that will have a positive environmental impact."

The researchers measured the viscosity of blood mixed with each polysaccharide and found alginate to be the most promising candidate. According to Hsu, alginate's excellent gel-forming properties most likely stem from a phenomenon called calcium-mediated crosslinking.

Related: Menstrual cycle linked to structural changes across whole brain

"In water, the long sugar chains float around individually," Hsu explained. However, each alginate molecule also has a series of smaller chains, which contain so-called carboxylate groups, branching off it. Period blood contains charged calcium particles that grab hold of these small chains, forming bonds between alginate molecules. Together, these bonds create "an interlinked network" that locks everything together in a gel, Hsu said.

The team needed to ensure that powdered alginate was practical for use in menstrual products. They added a small amount of glycerol — a liquid that draws water to itself — to help draw blood through the dry powder. 

They also incorporated an antibacterial substance to help prevent the growth of Staphylococcus aureus. This bacterium can cause toxic shock syndrome, a rare complication of some infections in which bacteria release dangerous toxins. A small percentage of cases are tied to tampons — typically highly absorbent tampons that have been left in for longer than recommended. 

The antibacterial substance, derived from algae, curbed the growth of S. aureus at body temperature. The substance also didn't leach out of the powder, so the researchers think it's unlikely to disrupt the vaginal microbiome.     

The researchers then created a prototype pad with their new filler and pitted it against conventional pads in laboratory tests. They measured how well the two products absorbed about 0.3 ounces (8 milliliters) of blood and then tested their ability to retain the fluid under pressure, as if someone were sitting on them. 

"[The prototype] performed just as well as the commercial pad in terms of absorption, but importantly, our material retained that blood much better," Hsu said.

The team also tested the powder in a menstrual cup, by placing it in a cotton lining designed to sit inside the cup. In these tests, the alginate powder consistently reduced the amount of spillage that occurred when the cup was removed from a synthetic vagina.

"Even if you invert the cup, the blood doesn't flow out," Hsu said. "You remove the powder-containing cotton to empty out the blood. Hopefully this would make it easier to manage a cup when someone's out and about in a public space."  

There's still a way to go before the team's product makes it to market. Safety testing and manufacturing processes need to be addressed for the additive to pass regulatory muster. But Hsu hopes that, eventually, this will make a difference to the lives of people who menstruate.

Ever wonder why some people build muscle more easily than others or why freckles come out in the sun? Send us your questions about how the human body works to community@livescience.com with the subject line "Health Desk Q," and you may see your question answered on the website!

The images of dragons unleashing torrents of flames on the new series of House of the Dragon got me thinking: if dragons existed, what real-world biological mechanisms and chemical reactions might they use?

But first, a chemistry recap. To ignite and sustain a flame, we need three components; a fuel, an oxidising agent - typically the oxygen in the air - and a heat source to initiate and maintain combustion.

Let’s start with the fuel. Methane could be a candidate. Animals produce it during digestion. The images on the screen of Westeros show dragons are keen on eating sheep. However, our methane-fuelled dragons would need to have a diet and digestive system more like that of a cow to produce enough gas to burn down a city.

There’s also a problem with the storage of sufficient amounts of methane gas. A typical methane cylinder might be rated for 150 atmospheres of pressure, while even a bloated gut can only tolerate a little over one atmosphere. So there’s no biological basis for non-marine animals to store gasses under high pressure.

A better option would be a liquid. Ethanol could be an option. Maybe our dragons hold a vat of fermenting yeast in their guts, or they could have a metabolic system similar to Devil’s Hole pupfish, which live in hot springs in Nevada, US. Under low oxygen conditions, these fish switch to a form of respiration which produces ethanol.

However, storage is once again an issue. Ethanol quickly passes through biological membranes, so keeping it at high concentrations and ready to deploy on the "dracarys" signal (which translates to "dragonfire" in the fictitious language High Valyrian) would require some otherworldly biology.

RELATED: Dragons: A brief history of the mythical, fire-breathing beasts

So, if we are sticking to explanations with at least one foot in real-world biology, then my preferred option is something more oil-based. As anyone who has accidentally set fire to a frying pan knows, this can be a source of roaring flames. There is a biological basis for this in the fulmar gull.

They produce energy-rich stomach oil that they regurgitate to feed their chicks. The oil also serves as a deterrent. When threatened, the fulmar vomits the sticky, stinky oil over predators. Thankfully, the gulls have not yet evolved a way to ignite their vomit.

Feeding the flames

Now that we have a fuel source, let’s turn our attention to the oxidising agent. As with most fires, this will most probably be oxygen. However, it will take more than oxygen in the surrounding air to generate a jet of pressurised flaming oil hot enough to melt an iron throne. And it would have to be well mixed in with the fuel. The better the supply of oxygen, the hotter the flame.

A dragon could draw on some chemistry used by the bombardier beetle. This insect has evolved reservoirs adapted to store hydrogen peroxide (the stuff you might use to bleach your hair). When threatened, the beetle pushes hydrogen peroxide into a vestibule containing enzymes that rapidly decompose the hydrogen peroxide into water and oxygen.

This is an exothermic reaction, which transfers energy to the surroundings, and in this case raises the temperature of the mixture to almost boiling point. The reaction is so aggressive it is sometimes used to propel rockets. The increase in pressure caused by the rapid production of oxygen and the boiling water forces the noxious mixture out of a vent in the beetle’s abdomen and towards its prey or threat.

If employed by a dragon, this reaction has a few nice features. It would create the high pressure needed to drive the jet of oily fuel, the exothermic reaction would heat the oils making them more ready to combust, and most importantly, it would generate oxygen that would drive the combustion reaction.

All the dragon would need is some sort of biological equivalent of a petrol engine carburettor to mix the oil with the oxygen and create an explosive mix. As a bonus, the erupting mixture would probably form a fine mist of oil droplets, like an aerosol, which would ignite all the better.

The spark

Finally, we need a spark to ignite the mix. For this, I’m going to suggest the dragons have evolved an electric organ similar to that found in many fish, particularly electric eels.

These can generate short pulses of up to 600 volts, easily enough to create a spark across a short air gap. If these sparks discharged across the ducts at the back of a dragon’s mouth, they could ignite the high-pressure jet of oil and oxygen.

While we’ll never see a dragon unleashing torrents of flames outside the realm of fiction, it’s intriguing to ponder the science behind fantasy. So, next time you witness a Targaryen’s command of "dracarys," think about the biology behind that magical inferno.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.

There are so many diabolical possibilities, but which chemical is the most dangerous?

It comes down to a combination of effect and exposure—how much makes a deadly dose and what exactly will it do to you? Nerve agents are widely considered the most toxic chemical weapons owing to their tiny toxic limits and devastatingly rapid impacts on the human body: Just 10 milligrams (that’s ten thousandths of a gram) of VX is enough to cause death within minutes. Yet just one person has been killed by the nerve agent over the last decade.

Meanwhile, more than 100,000 people are accidentally poisoned in the U.S. every year by common household chemicals such as bleach and disinfectant, even though these substances are slower-acting and far less toxic than VX. And some common chemicals can be fatal when combined. For instance, combining drain cleaner and bleach will release poisonous chlorine gas. 

Those two examples highlight a key problem in ranking chemicals in order of danger: To evaluate danger, you need to know how likely you are to encounter a chemical.

Safety professionals define danger using a combination of two factors: hazard and risk. 

"A hazard is something with the potential to cause harm. Risk is the likelihood that harm will arise and the severity of that harm," said Richard Webb, the health, safety, environment and well-being officer at the University of Cardiff's School of Chemistry. The hazard is therefore a fixed property of a tool or chemical, while the risk varies depending on how that object is used.

We automatically consider this balance of factors every day. Take the example of a kitchen knife: We know the blade is sharp and will cut things, including us, in the right circumstances. But it's how we use and store the knife that determines whether it poses a danger to us, Webb told Live Science. 

Related: Can foxgloves really give you a heart attack?

This same logic applies to chemicals. "Even a very hazardous chemical does not pose any risk if there is no exposure," a spokesperson for the Finland-based European Chemicals Agency told Live Science. Botulinum toxin, VX and chlorine trifluoride are therefore extremely hazardous but very, very low risk to the average person.

"Some hazardous chemicals are also essential for our health in small doses," added the spokesperson, "whereas in higher exposures they may be lethal."

Ordinary table salt is an excellent example. The small amount in our diets is vital to maintain the correct ion balance within our bodies, but too much can cause severe health problems, like high blood pressure and heart failure. Outside the body, large quantities of that same salt act as a weedkiller by overwhelming plants' ion balance to the point of death.

Even determining which chemicals are the most hazardous is fraught with difficulty, as there are so many ways they could cause harm. In the European Union, classification, labeling and packaging regulations define nine hazardous characteristics, including toxic, explosive and corrosive. But again, Webb emphasized that which of these is most dangerous depends on the context.

For example, although chlorine is a common disinfectant in pools today, the concentrated gas was used as a chemical weapon in World War I and caused both chemical burns and respiratory irritation. The key difference though, is that pools include only a small amount of chlorine, and that small amount is dissolved into the water. "The thing that makes it high risk is the fact it's a gas," Webb said. 

On paper, sodium cyanide looks much worse. "It's famously poisonous. It binds to your hemoglobin permanently, which stops it from carrying oxygen so you can't respire," Webb said. However, as a solid, it's much easier to handle, meaning scientists using this toxic compound can more readily avoid the nasty effects of exposure. 

"If you work with it safely — you wear your PPE [personal protective equipment], work in a fume hood and wash your hands when you finish — the likelihood of contaminating yourself is pretty low," Webb explained.

This means our safety is often within our own control. Anything can become dangerous if it's not handled properly, but there are steps we can take to reduce the likelihood of harm. 

"The most important thing is knowing exactly what the hazards are and what you can do to minimize the risk," Webb said.

The wine, which the scientists described as "reddish liquid" in appearance, was found in a roughly 2,000-year-old tomb during a house construction project in Carmona, a town in Seville, in 2019.

The use of wine in Roman-era burial rituals is well documented, but discovering a wine sample this old, in its liquid state, was "rather exceptional and unexpected," the scientists wrote in their paper, published June 16 in the Journal of Archaeological Science: Reports. 

"It's a sunken tomb that was excavated from the rock, which allowed it to remain standing for 2,000 years," José Rafael Ruiz Arrebola, an organic chemist at the University of Córdoba and a senior author of the study, told The Guardian. 

Wine contains distinct chemical compounds that reflect not only its flavor and appearance but also its origins. But after many years, these chemicals often undergo substantial decay that makes them difficult to characterize, the scientists wrote in the paper. 

During the funerary ritual, cremated ashes were mixed with the liquid, making it murky, the scientists told The Guardian. 

Using analytical techniques including high-performance liquid chromatography and mass spectrometry, the scientists sifted through element-by-element to find components that belonged to the liquid. 

Wine grapes contain distinct plant compounds known as polyphenols that serve as a "barcode," marking their varietal and the conditions in which they were grown and harvested. However, "few studies have been conducted on polyphenols in archaeological wine remains," the scientists wrote in the study. 

When the scientists found polyphenols in the liquid sample, their suspicions were confirmed — the ancient liquid was indeed wine.

From looking at historical texts, they suspected that the wine would have been similar to modern fino wines produced from regions in southern Spain. The scientists compared the polyphenol content of the ancient wine to today's wines to determine that the wine was likely from Doña Mencía, a city in southern Cordoba.

While the liquid is reddish, it lacked syringic acid, a compound that is produced by red wine when it decomposes, which confirmed that the original wine was actually white. 

Despite having mostly decayed, the ancient wine isn't, "the least bit toxic," according to microbiological analyses, Arrebola told The Guardian. Nevertheless, the scientists did not taste it.

Other ancient wine analyses have focused on dried remnants, such as the 8,000-year-old fingerprints of tartaric acid, a compound of grapes and wine, found on a clay jug in the Republic of Georgia. Because the new study analyzed liquid wine, this discovery is one of a kind.

"We have been lucky to find it and analyze it — it's something you only see once in your life," Arrebola told CNN.

Cotton is susceptible to this kind of laundry blunder in a way that synthetic fibers, like polyester, are not. A large part of this vulnerability comes down to the individual fibers of the cotton clothes, Jillian Goldfarb, an associate professor of chemical and biomolecular engineering at Cornell University, told Live Science in an email. 

"Cotton fabric is made by weaving together fibers from a cotton plant, which themselves are made mostly of cellulose, a natural biopolymer," she said. "Cotton … is prone to shrinking because its fibers swell when they get wet and then contract as they dry."

If you've ever sweat in cotton clothes, you know firsthand how well they can absorb moisture. On the other hand, synthetic fabrics — like polyester, nylon and spandex — are more resistant to sweat and shrinkage because their tightly woven fibers don't swell in water.

On a chemical level, weaving cotton fiber for clothing introduces tension that creates a hydrogen bond network, Erika Milczek, a chemist and CEO of biotechnology company CurieCo, told Live Science. 

Related: When did humans start wearing clothes?

When variables like heat and water are introduced, this hydrogen bond network can transform, causing fabric to either relax or contract. This is also the science responsible for wrinkles in your clothes, Milczek said.

The science of shrinking

When it comes to accidentally shrinking your cotton clothes, not all items are made equally, Goldfarb said. 

"Even when they're made of the same material, some cotton fabrics are more prone to shrinking than others depending on how the fibers are assembled into a fabric," she said. "Woven cottons, while they will certainly shrink, see considerably less shrinkage than knit cottons."

Imagine the intersection of woven cotton fibers like a hashtag, where some fibers are woven under others, Goldfarb said. Yarn woven horizontally is called the "warp," and yarn woven vertically is called the "weft."

"As the yarns swell when they're wet, they push the wefts closer together, shrinking in one direction," Goldfarb explained. "When the moisture is taken out of the fabric, the fibers contract." This means that shrinking actually begins before the clothes ever hit the dryer. Shrinking is the dual consequence of water-logged fibers and high heat.

Exactly how much your clothes shrink is determined by a number of factors, Milczek said. For example, it depends on whether you wash your clothes in water alone or add detergent — detergent further disrupts hydrogen bonds — and whether you dry your clothes at high heat or low heat or hang them to dry. 

"The temperature [when line drying] is considerably lower, so evaporation occurs much more slowly, and the fibers are not 'stressed' by the heat in shrinking," Goldfarb explained. A line-dried shirt also experiences more consistent humidity between the outdoors and your closet, which can result in less shrinkage, she said.

Saving a shrunk shirt 

For some, this knowledge may come a little too late. But don't fret; there may still be hope for your shrunken garments. 

One obvious answer, Milczek said, is to look for clothes that are shrink resistant to begin with. These include cotton clothes with synthetic blends or cotton clothes that have been preshrunk. 

If that won't do the trick, there is a science-backed way to attempt to "unshrink" your clothes. 

"Depending on the quality of the yarn and the weave … if we swell the fibers and allow them to dry under tension, it is possible to "unshrink" some cotton fabrics, at least temporarily," Goldfarb said. 

One way to do this at home is to use a steam iron, she said. This reintroduces moisture into the garment to expand the fibers while applying mechanical force to stretch them back out. But tread lightly — this method can also easily swing too far in the opposite direction.

"Of course, it's easy to 'overstretch' your cotton this way, and if it's done unevenly, you can be left with a rather warped item of clothing." Goldfarb said. 

In essence, rocks are aggregates of two or more minerals. Minerals, meanwhile, are solids that, with a few exceptions such as diamonds, lack carbon and are arranged in an orderly, repeating "crystal structure." 

"Minerals are basically the building blocks of rocks," Erika Anderson, an honorary curator of mineralogy and petrology at the University of Glasgow's Hunterian Museum in Scotland, told Live Science. "It's kind of like atoms in a molecule, so minerals are the atoms." 

Each type of mineral has a unique crystal structure, which results from its chemical composition and dictates a set of physical properties, such as hardness, color or magnetism, according to the United States Geological Survey (USGS). For instance, halite — the natural form of sodium chloride (NaCl), from which table salt is made — is a soft mineral that forms clear, cube-shaped crystal fragments. Different minerals, like aragonite (CaCO3) and calcite (CaCO3), can have the same chemical makeup, but their crystal structure and physical properties differ because of how they each formed.

"For each mineral, they will have a set way that those atoms bond together," Anderson said. "Some minerals have the exact same elements in them, but they're bonded differently, so it makes them different minerals."

Related: Fountains of diamonds that erupt from Earth's center are revealing the lost history of supercontinents

A good example of a mineral is quartz, which is found across the world and in different rocks, such as granite and quartzite, Anderson said. Quartz is made of the chemical elements silicon and oxygen and has the chemical formula (SiO2). The mineral is colorless in its pure form, but impurities can either make quartz crystals appear opaque or stain them pink, purple, yellow or brown.

As of May 2024, the International Mineralogical Association — the scientific body responsible for identifying, approving and naming minerals — listed 6,050 mineral species. Experts distinguish minerals based on their crystal structure, which is the specific way in which their atoms or elements are arranged.

While some minerals like halite have relatively simple crystal structures, others can contain 10 or more elements, such as khomyakovite and georgbarsanovite.

"We're constantly finding new minerals, because we're exploring areas that might have conditions we didn't know about," Anderson said.

The rock cycle

There are three main types of rock — igneous, sedimentary and metamorphic — with varying mineral mixes depending on where and how the rock came to be. 

Igneous rocks — which form as magma solidifies either deep within Earth or at the surface after a volcanic eruption, for example — contain a limited number of minerals that crystallize, Richard Bevins, an honorary professor of Earth sciences at Aberystwyth University in the U.K., told Live Science in an email. "These are termed the common rock-forming minerals and include feldspar, olivine, pyroxene, mica, quartz and amphibole."

Igneous rocks may be subjected to high heat and pressure, or exposed to fluids that alter their mineral composition. Once their mineral composition changes, the rocks are considered metamorphic, with examples including phyllite, schist, quartzite and marble. Igneous and metamorphic rocks on Earth's surface inevitably erode and break up as wind and water go to work on them. The fragments are transported and form deposits that solidify into new rocks called sedimentary rocks. "Sedimentary rocks are principally composed of minerals present in the rocks that were eroded to form the sediment," Bevins said. 

In general, the process by which rocks are continually recycled and transformed by geological processes is known as the rock cycle.

Some rocks are mono-mineralic, meaning they only contain one mineral. Limestone, for example, is a sedimentary rock made exclusively of the mineral calcite (CaCO3). Glacier ice too, is a type of rock composed of crystals of water.

In 2014, scientists proposed naming a new type of rock derived from plastic pollution: plastiglomerate. A team found that plastic littering a beach in Hawaii had melted and glued natural sediments together, forming rock-like lumps. And like rocks, researchers said those plastiglomerates may forever remain in the geological record and mark the fragment of Earth's history that we inhabit. 

Editor's Note: This story was updated at 10:30 EDT to note that most, but not all, minerals lack carbon (diamond being a notable exception). It was also updated to note that the crystal structure dictates a mineral's physical properties. 

Promethium is one of the 15 lanthanide elements at the bottom of the periodic table. Also known as the rare earths, these metals exhibit a number of useful properties, including strong magnetism and unusual optical characteristics, making them particularly important in modern electronic devices. 

"They are used in lasers; they are part of the screens of your smartphone. They are also used in very strong magnets in wind turbines and electric vehicles," Ilja Popovs, a research and development staff member at Oak Ridge National Laboratory (ORNL) and co-author of a new study published in the journal Nature, told Live Science. 

'Scarce and difficult to study'

Promethium itself, which was discovered by ORNL scientists in 1945, has a few minor applications in atomic batteries and cancer diagnostics. But scientists have a very limited understanding of the element's chemistry, precluding more widespread uses. 

Studying the radioactive element has posed a decades-long challenge, partly due to the difficulty of securing a suitable sample, team member Alexander Ivanov, also a research and development scientist at ORNL, told Live Science.

"Promethium doesn't have a stable isotope — they're all radioactive, meaning that they are decaying [into other elements] with time," Ivanov said. "You get this element through a fission process, so it's scarce and difficult to study."

ORNL is the U.S.' only producer of promethium-147, an isotope of the element with a radioactive half-life of 2.6 years. Using a method developed last year, the researchers separated this isotope from nuclear reactor waste streams, creating the purest possible sample for study.

Related: Atoms squished closer together than ever before, revealing seemingly impossible quantum effects

Then, the team combined this sample with a ligand — a molecule specially designed to trap metal atoms — to form a stable complex in water. The coordinating molecule, known as PyDGA, formed nine promethium-oxygen bonds, giving researchers the first-ever opportunity to analyze the bonding properties of a promethium complex.

However, the analysis itself was no trivial matter. 

"Because promethium is radioactive, once it's decaying, it's getting transmuted into the adjacent element, which is samarium," Ivanov said. "So you will have a tiny amount of contamination in the form of samarium." 

'The last puzle piece'

The team therefore used an extremely specialized, element-specific technique called synchrotron-based X-ray absorption spectroscopy. High-energy photons generated by a particle accelerator bombarded the promethium complex to build a picture of the positions of atoms and the lengths of bonds. Subtle differences in the metal-oxygen bond lengths then allowed the team to focus on the key promethium-oxygen bond, discounting any contaminating samarium.

Crucially, this information enabled a comparison of promethium's properties with other rare earth complexes for the first time. 

"Promethium was the last puzzle piece among those elements," Popovs said. The ligand provided a way to have a stable complex for all of the lanthanides — the same element ratios and the same kind of geometry. That allowed the team to "study the fundamental physical chemical properties of these complexes across the whole series," Popovs explained.

Lanthanides are naturally found as mixtures of elements, so understanding periodic trends such as bond lengths and complex-forming behaviors helps scientists develop new and more efficient methods to separate these valuable metals. 

Now, the ORNL team is studying promethium in water to build a clearer picture of the coordination environment and chemical behavior of this unusual element. 

"Hopefully, the fundamental insights that we're providing will inform other scientists how to design better separation technologies and can perhaps spur more interest in studying it for other applications," Popovs said.

Natural diamonds form in Earth's mantle, the molten zone buried hundreds of miles beneath the planet's surface. The process takes place under tremendous pressures of several gigapascals and scorching temperatures exceeding 2,700 degrees Fahrenheit (1,500 degrees Celsius).

Similar conditions are employed in the method currently used to synthesize 99% of all artificially created diamonds. Called high-pressure and high-temperature (HPHT) growth, this method uses these extreme settings to coax carbon dissolved in liquid metals, like iron, to convert it to diamond around a small seed, or starter diamond. 

However, the high pressures and temperatures are difficult to produce and maintain. Plus, the components involved affect the diamonds' size, with the largest being about a cubic centimeter, or about as big as a blueberry. Besides, HPHT takes a fairly long time — a week or two — to produce even these tiny gems. Another method, called chemical vapor deposition, eliminates some requirements of HPHT, like high pressures. But others persist, like the need for seeds.

The new technique eliminates some drawbacks of both synthesis processes. A team led by Rodney Ruoff, a physical chemist at the Institute for Basic Science in South Korea, published their findings April 24 in the journal Nature. 

Related: Scientists may have pinpointed the true origin of the Hope Diamond and other pristine gemstones

The diamond crucible

The novel method was a long time in the making. "For over a decade I have been thinking about new ways to grow diamonds, as I thought it might be possible to achieve this in what might be unexpected (per 'conventional' thinking) ways," Ruoff told Live Science by email.

To start out, the researchers used electrically heated gallium with a bit of silicon in a graphite crucible. Gallium may seem like an esoteric element, but it was selected because a previous, unrelated study showed that it could catalyze the formation of graphene from methane. Graphene, like diamond, is pure carbon, but it contains the atoms in one layer rather than in the gemstone's tetrahedral orientation. 

The researchers housed the crucible in a home-built chamber maintained at sea-level atmospheric pressure, through which superhot, carbon-rich methane gas could be flushed. Designed by co-author Won Kyung Seong, also of the Institute for Basic Science, this 2.4-gallon (9 liters) chamber could be readied for experimentation in just 15 minutes, allowing the team to rapidly undertake runs with different concentrations of metals and gases. 

Through such tweaking, the researchers figured that a gallium-nickel-iron mixture — coupled with a pinch of silicon — was optimal for catalyzing the growth of diamonds. Indeed, with this blend, the team obtained diamonds from the crucible's base after just 15 minutes. Within two and a half hours, a more complete diamond film formed. Spectroscopic analyses showed that this film was largely pure but contained a few silicon atoms.

The minutiae of the mechanism that formed the diamonds are still largely murky, but the researchers think a temperature drop drives carbon from the methane toward the crucible's center, where it coalesces into diamond. Plus, without silicon, no diamonds form, so the researchers think it may act as a seed for the carbon to crystallize around. 

However, the new method has its own challenges. One problem is that the diamonds grown with this technique are tiny; the largest ones are hundreds of thousands of times smaller than the ones grown with HPHT.  That makes them too small to be used as jewels.

Other potential uses — for example, in more technological applications like polishing and drilling — for the diamonds synthesized with the new technique are unclear. However, because the process involves low pressure, Ruoff said, it might significantly scale up diamond synthesis. 

"In about a year or two, the world might have a clearer picture of things like possible commercial impact," he added.  

The water-battery has a lifetime of over 1,000 charge-discharge cycles, the team reported April 23 in the journal Nature Energy.

One of the most important properties of any battery is the energy density — how much energy the battery contains relative to its size or weight. Lithium-ion batteries have a particularly high energy density and are widely used in electric cars and portable devices. However, the liquid component, known as the electrolyte, typically contains organic chemicals which can catch fire or explode if the system overheats. 

Related: How do electric batteries work, and what affects their properties?

In contrast, water-based batteries are much safer but generally have a lower energy density thanks to the narrow voltage window in which they operate. However, by hacking the chemistry taking place inside the water electrolyte, Li’s team have dramatically boosted both the energy density and the overall performance of aqueous batteries.

Electrolyte solutions are actually a mixture of many different chemicals, each controlling a different aspect of the battery's performance. Additives called mediators help move electrons across the solution by undergoing a series of supporting oxidation and reduction (redox) reactions.

For aqueous batteries, the most common mediator is iodine: through a sequence of individual redox reactions, this halogen element can transfer up to six electrons per cycle, converting iodide (I–) to iodate (IO3–). However, slow reaction rates and unwanted byproducts mean that this additive usually results in a low-energy-density battery.

To improve the efficiency of this mediating redox sequence (and therefore the overall energy density), Xianfeng Li from the Chinese Academy of Sciences, and colleagues developed a mixed halogen electrolyte, containing both I– and bromide (Br–) ions in an acidic solution. Introducing bromine, another halogen element capable of transferring electrons, provided a stepping stone for this difficult chemistry, increasing the reaction rate and suppressing the formation of nuisance byproducts. 

Related: Future electric cars could go more than 600 miles on a single charge thanks to battery-boosting gel

Through detailed electrochemical and spectroscopic analyses, the team demonstrated that the bromide ions participated in the redox reactions alongside the iodide, forming a vital intermediate and boosting the speed and efficiency of the electron transfer sequence.

The researchers then began a series of experiments to evaluate the impact of this “hetero-halogen” electrolyte on the overall performance of several common battery types using different materials as the negative terminals (anodes).

The new electrolyte nearly doubled the energy density compared with standard lithium-ion batteries when used with cadmium anodes, which are typically found in high-energy portable devices such as power tools. . Meanwhile, vanadium systems, which are often attached to power plants and renewable energy generators for grid energy storage, demonstrated particularly long lifetimes, maintaining peak performance over more than 1,000 charge-discharge cycles.

In both cases, the team reported improved energy efficiencies and calculated that the aqueous hetero-halogen system would be cost-competitive compared with current lithium-ion technologies.

The team hopes that this substantial performance enhancement will lead to wider use of water-based batteries as a safer, high-energy-density alternative to existing systems.

We often think of space as a yawning chasm of nothingness between stars, but this apparent emptiness is alive with chemistry as atoms come together and break apart to create stars and planets over millions of years. Understanding how simple organic molecules such as methane, ethanol and formaldehyde form helps scientists build a picture of not only how stars and galaxies are born but also how life began.

However, detecting these basic building blocks of life is no mean feat. Every molecule possesses a unique energy "barcode" — a collection of specific wavelengths of light that the molecule can absorb. At a quantum level, each absorbed wavelength corresponds to a transition between one rotational energy level and another, and every molecule has a different-but-well-defined set of energy levels where these transitions may occur. This barcode of energy transitions is easily measured for samples in the lab, but astrochemists must then hunt out this same energy signature in space.

"When we observe interstellar sources with radio telescopes, we can collect the rotational signal from the gaseous molecules in these regions of space," first study author Zachary Fried, an astrochemist at MIT, told Live Science in an email "Because the molecules in space obey the same quantum mechanical laws as those on Earth, the rotational transitions observed in the telescope data should line up with those measured in the lab."

Related: Scientists made the coldest large molecule on record — and it has a super strange chemical bond

This approach is exactly how Fried and colleagues — part of a research team led by Brett McGuire, an assistant professor of chemistry at MIT — detected 2-methoxyethanol, a 13-atom molecule in which one of the hydrogen atoms of ethanol is replaced with a more complex methoxy (O–CH3) group. This level of complexity is particularly unusual outside the solar system, with only six "species" larger than 13 atoms ever detected. 

"These molecules are typically much less abundant than smaller hydrocarbons that have simpler formation routes," Fried said. "Additionally, the spectral signals of these molecules are distributed over a greater number of transitions, thus making the individual spectral peaks weaker and more difficult to observe."

But it wasn't simply luck that led the team to this discovery; they also used artificial intelligence. The team had previously developed a machine-learning method to model the abundance of different molecular species in different regions of space. "Using these trained models, we can predict which undetected molecules may be highly abundant, and thus strong detection candidates," Fried said.

Methoxy-containing species had previously been detected in a part of the Cat's Paw Nebula, also called NGC 63341, and in IRAS 16293, a binary system in the Rho Ophiuchi cloud complex, located 457 light-years from Earth. As such, the team had a good idea of where to look for the new molecule.

Fried began by measuring the rotational spectrum of 2-methoxyethanol samples in the lab; he recorded a total of 2,172 possible energy signals for the molecule. Then, using the Atacama Large Millimeter/Submillimeter Array (ALMA), a set of 66 radio telescopes in Chile, the team collected readings from both the Cat's Paw Nebula and IRAS 16293 and analyzed the signals for the distinct energy signature of 2-methoxyethanol.

While no corresponding energy traces were detected in IRAS 16293, the team ultimately identified 25 matching signals from the Cat's Paw Nebula and confirmed the presence of 2-methoxyethanol in this star-forming region. 

"This enabled us to investigate how the differing physical conditions of these sources may be affecting the chemistry that can occur," Fried said. "We hypothesized several causes of this chemical differentiation, including variations in the radiation field strength, along with different dust temperatures in these two sources [at different stages] of star formation."

The team hopes the findings may inform future studies to identify other as-yet-undetected molecules in space. 

"The feasibility and efficiency of these pathways can be closely tied to the physical conditions of the interstellar source," Fried said. "By investigating which other species are involved in the formation and destruction of the detected molecules, we can determine other species that may be candidates for detection."

But why does it work? Why does striking a flint rock against a piece of steel start a fire, whereas rubbing two random rocks together doesn't?

All fire-starting methods have a similar goal: generating enough heat to ignite a fuel source.

When scraped together, flint and steel can generate this heat quickly because of the way the iron in the steel reacts with the surrounding air when it's shaved off by the flint, said Peter Sunderland, a fire scientist at the University of Maryland.

This is how a classic pocket lighter works, according to Sunderland. Each flick of the wheel rubs flint against steel, igniting the butane fuel inside and producing a flame.

But understanding exactly why this combination is so effective requires digging into the chemistry of oxidation. Oxidation is when a chemical element or compound combines with oxygen, changing its properties. When this process happens to iron, it's known as rusting. Using flint and steel to start a fire harnesses a side effect of oxidation: heat.

Related: What's the longest-burning fire in the world?

Early humans made tools out of flint because the rock can be shaped into arrowheads and sharp blades. Flint is much harder than steel, so striking the two together shaves off tiny bits of iron from the steel.

Iron oxidizes very easily when it's exposed to the air, but the process usually happens very slowly. A neglected car or a piece of abandoned farm equipment will take many years to become covered in rust, for example.

However, these tiny iron particles from the steel oxidize within fractions of a second, though they wouldn't look rusty to the naked eye. This creates very hot sparks. The process happens so quickly because the bits of iron have much more surface area than a bulk piece of iron.

"What's important is the surface-to-volume ratio," Sunderland told Live Science. With a small iron shaving, "the volume is basically zero, but there's lots of surface area."

So, when a tiny piece of iron is shaved off, many iron atoms are suddenly exposed to the air and can oxidize all at once. The chemical reaction rapidly generates a tremendous amount of energy as heat. And if enough of these burning-hot iron shavings fall into a pile of dry leaves or twigs, they can ignite the kindling and get a fire going.

It can be challenging to get the sparks to turn into a flame, so it's helpful to have something that the sparks can more easily ignite to accelerate the process. Shavings of steel work well, Sunderland said — they'll flame up when sparks land on them. Historically, people used a "char cloth" — a burnt piece of fabric that ignites easily and then slowly smolders, giving the kindling around it time to light.

Before steel was widely produced, humans might have generated sparks by scraping flint against other iron-rich rocks, such as pyrite, better known as fool's gold.

Other fire-starting technologies use similar principles. Magnesium fire starters, a popular off-the-shelf option, take advantage of the fact that magnesium burns very hot. So scraping shavings of magnesium into a pile of tinder and then generating sparks by scraping an iron-containing rod above them can quickly get a crackling fire going.

Matches use a completely different set of chemical reactions, but they have a similar goal: generating a lot of heat quickly to ignite a fuel source.

Sometimes, this process happens accidentally, said Sara McAllister, a research mechanical engineer with the U.S. Forest Service in the Missoula Fire Sciences Lab. For instance, wildland fires can start when someone tows a trailer with a chain dragging behind on the pavement, creating sparks. Or clashing power lines generate sparks that set dry grass ablaze.

"They're all kind of in the same realm: tiny, hot particles that land in dry kindling," McAllister told Live Science.

The new material, dubbed "goldene," could have important applications in carbon dioxide conversion and hydrogen generation, the researchers said.

To make goldene, the team employed a 100-year-old technique used by Japanese iron smiths to isolate single layers of the precious metal. They reported their work in the journal Nature Synthesis on April 16. 

Researchers are particularly interested in two-dimensional materials because of their unusual optical, electronic and catalytic properties. The extremely high surface area of these substances relative to their volume means they behave very differently than chemically-identical bulk solids, and numerous examples of 2D materials have been reported since the discovery of graphene in 2004.

Related: World's thinnest electronic device is 2 atoms thick

However, most of these materials are prepared from nonmetals or mixed compounds, and creating single-atom sheets of pure metals is much more challenging.

"Metals do not like to be lonely," Michael Yeung, a solid-state chemist at the University at Albany, told Live Science in an email. "Because the bonding in metals is delocalized, they readily will bond into themselves and agglomerate. Preparing a single layer is quite a feat because you are fighting against the metal's desire to bond with not only itself but with other sheets."

Previous attempts have run into this problem. Several teams have created a single layer of gold atoms embedded within a supporting solid, such as graphene-coated silicon carbide — "like a sort of 'sandwich' structure, using graphene as a pseudo-bread and the gold as the meat," Yeung said. But extracting the goldene from these complex layered solids proved problematic, with the gold atoms coagulating into nanoparticles as soon as the support was removed.

Shun Kashiwaya, an assistant professor in the Department of Physics, Chemistry and Biology at Linkӧping University in Sweden, and colleagues turned this approach on its head to successfully isolate goldene sheets for the first time.  

They began by creating a layered structure of titanium, silicon and carbon, which they then covered with a surface layer of gold. Over 12 hours, gold particles diffused into the material, replacing the silicon layer with gold and creating a goldene sheet embedded within the solid. However, rather than trying to remove the gold layer, the team carefully etched away all of the surrounding solid, leaving the gold sheet untouched.

They figured out the technique when study coauthor Lars Hultman, a professor in the Department of Physics, Chemistry and Biology at Linkӧping University, was researching chemical etchants. Hultman found a 100-year-old method used by Japanese smiths to etch away carbide residues in steel, Kashiwaya told Live Science. Called Murakami's reagent or alkaline potassium ferricyanide, the solution etched away the surrounding titanium carbide support, without affecting the goldene sheet.

To perfect the method, the team experimented with different reaction conditions and concentrations of the etching solution. Crucially, they found that adding a cysteine as a surfactant, or a chemical which decreases the surface tension of a liquid, stabilized the isolated sheets and prevented the gold atoms from clustering and combining into nanoparticles. 

The freestanding goldene sheets were up to 100 nanometers long and are hundreds of times thinner than ordinary gold leaf.

Kashiwaya and Hultman believe that, due to goldene's enhanced chemical reactivity, it could have important applications in reactions to convert carbon dioxide into fuels such as ethanol and methane and water into hydrogen. They are currently working on improving the synthetic method. 

"We aim to explore goldene's fundamental physical and chemical properties and further develop the synthetic process to increase both the goldene sheet area and yield," Kashiwaya said. "We also envision applying this approach to produce other elemental 2D materials (metallenes) beyond goldene."

Yeung is particularly interested in the preparation of new 2D materials made possible by this method. "The ability to selectively etch what is normally stable means that a bunch of new materials can be made," he said. 

The next step could be creating a single layer of silver using aluminas as the base, Yeung said. 

Atoms or molecules bounce around randomly, collide, and form other molecules. At higher temperatures, atoms collide more and the rate at which atoms become molecules increases. Below a certain temperature, the reaction won't happen at all.

But something very weird happens at the lowest temperatures. In this extreme cold, there is essentially no heat energy, yet chemical reactions happen faster than they do at high temperatures.

The phenomenon is called quantum superchemistry. And it was finally demonstrated last year, more than 20 years after physicists first proposed it.

In that experiment, University of Chicago physicist Cheng Chin and colleagues coaxed a group of cesium atoms at just a few nanokelvin into the same quantum state. Amazingly, each atom did not interact separately. Instead, 100,000 atoms reacted as one, almost instantaneously.

The first demonstration of this weird process has opened a window for scientists to better understand how chemical reactions operate in the strange realm of quantum mechanics, which governs the behavior of subatomic particles. It also may help to simulate quantum phenomena that classic computers struggle to model accurately, such as superconductivity.

But what happens after that, as with so many advances in research, is hard to predict. Chin, for one, has no plans to stop studying this strange form of chemistry.

"No one knows how far we can go," Chin told Live Science. "It might take another 20 years. But nothing can stop us."

A new kind of chemistry

The term "superchemistry" was coined in 2000 to liken the phenomenon to other strange effects, like superconductivity and superfluidity, which emerge when large numbers of particles are in the same quantum state.

Unlike superconductivity or superfluidity, however, "'superchemistry' differs in that it is still barely realized, while these other phenomena have been extensively studied in experiments," Daniel Heinzen, lead author of the 2000 study and a physicist at the University of Texas at Austin, told Live Science in an email.

Heinzen and colleague Peter Drummond, who is now at the Swinburne University of Technology in Australia, were studying a special state of matter known as a Bose-Einstein condensate (BEC), in which atoms reach their lowest energy state and enter the same quantum state. In this regime, groups of atoms begin to act more like a single atom. At this small scale, particles can't be described as being in a given place or state. Rather, they have a probability of being in any given place or state, which is described by a mathematical equation known as the wave function.

In a BEC, just as Satyendra Nath Bose and Albert Einstein's work predicted, the individual wave functions of each atom become a single, collective wave function. Heinzen and Drummond realized that a group of particles with the same wave function is similar to a laser — a group of photons, or packets of light, that have the same wavelength. Unlike with other light sources, the peaks and troughs of a laser's wave are aligned. This allows its photons to stay focused in a tight beam over long distances, or to be broken up into bursts as short as millionths of a billionth of a second.

Related: How do lasers work?

Similarly, Heinzen, Drummond and their colleagues showed mathematically that the atoms in a BEC should behave in ways other groups of atoms don't. Near absolute zero, where there is almost no heat energy, quantum superchemistry means the atoms in a BEC could convert, quickly and all together, to molecules: Atoms A would bond in a flash to form molecules of A2, and so forth.

The process would resemble a phase transition, Chin says, such as when liquid water freezes to ice. And, thanks to the quantum weirdness of these systems, the more atoms condensed in the BEC, the faster the reaction happens, Heinzen and Drummond's calculations predicted.

The 20-year quest

Heinzen and his research group tried to demonstrate the phenomenon with experiments for several years. But they never found convincing evidence that the effect was happening. "And then we kind of dropped it," Heinzen said.

While Heinzen abandoned the quest to demonstrate quantum superchemistry, others were still hunting for ways to turn the wild theory into experimental reality. One of them was Chin, who started working on quantum superchemistry almost immediately.

Chin was a doctoral student studying cesium atoms at cold temperatures when Heinzen and Drummond's superchemistry paper came out. "My research was totally derailed because of this new research," Chin told Live Science. He set out on what would become a 20-year quest to achieve quantum superchemistry in the lab.

It wasn't a straight path, and Chin sometimes took breaks from working toward quantum superchemistry. But he never abandoned his goal.

"Nobody knew if this was going to work out before it happened. But also nobody said it couldn't happen," he said.

After a decade of slow progress, in 2010, Chin and his colleagues figured out how to precisely tune magnetic fields onto a BEC to coax cesium atoms together to make Cs2 molecules.

"That provided the evidence of how to move forward," Chin said.

But to show quantum superchemistry was occurring, his team still needed better ways to cool and control ultracold molecules.

Scientists typically use two techniques to push atoms and molecules to ultracold temperatures. First, lasers cool atoms to millionths of a kelvin above absolute zero. Atoms in the sample absorb photons from a laser tuned to very specific energy, thus reducing the atoms' momentum and the sample's temperature incrementally.

Next, they use evaporative cooling. The atoms in these experiments are trapped by laser light or magnetic fields. Scientists can adjust the traps to let the fastest — and, therefore, hottest — atoms escape. This process further cools the atoms to billionths of a kelvin, where quantum superchemistry is possible.

It was the second step that took Chin and his collaborators the longest to get right. For years, he had used bowl-shaped traps that pushed the atoms together in the middle, which raised the samples' temperature.

Six or seven years ago, his group began using a digital micromirror device to better control the shape of the trap. The result? Flat-bottomed traps, shaped something like petri dishes, where the atoms could spread out and stay ultracold.

Around 2020, Chin's group finally made a BEC of cesium molecules. They were some of the coldest molecules ever made, about ten-billionths of a degree above absolute zero. And while the team suspected quantum superchemistry had occurred, they didn't have proof.

That proof came three years later. By then, they had collected the evidence of two hallmarks of quantum superchemistry. First, the reaction was happening collectively, meaning many cesium atoms became cesium molecules at once. And second, it was reversible, meaning the atoms would become molecules, which would become atoms, and on and on.

For Chin, last year's experiments are just the beginning. They produced two-atom molecules using superchemistry. But Chin thinks three-atom molecules are within reach, and he's excited to see what else might be possible.

Where quantum superchemistry takes us

As is often the case in areas of fundamental research like this one, the experiments have raised new theoretical questions. For instance, in Heinzen and Drummond's theoretical quantum superchemistry system, more than half of all the atoms in a trap would convert into molecules and then go back again. But Chin's group observed that such a conversion happened only 20% of the time. “Much is still to be understood to gain higher efficiencies,” Chin said in an email.

Heinzen suspects collisions between molecules in the dense gas are to blame. Collisions could push molecules into different quantum states, knocking them out of the pool of condensed molecules. He and Drummond had not accounted for that possibility in their theory.

"It was obvious even from the beginning [that collisions were] going to be kind of a negative effect, but in 2000 we had no idea how big it would be," Heinzen said. "We just said, we're ignoring it because we don't know how big."

The experiments also revealed that three cesium atoms were frequently involved in forming a single Cs2 molecule (and leaving one Cs atom left over), which physicists call a three-body interaction. Previous predictions about quantum superchemistry did not include such interactions.

For Chin, that's a hint that he'll need to do some new experiments. If his group can design and perfect experiments to probe these many-body interactions, it could help elucidate the rules of quantum superchemistry.

Despite these open questions, many scientists view quantum superchemistry as a possible tool for better understanding chemical reactions in general. Atoms and molecules in a boiling beaker inhabit wide ranges of quantum states and interact in myriad ways that make them too complicated to study in fine detail experimentally. In contrast, atoms and very simple molecules in BECs are in precisely controlled, well-defined quantum states. So quantum superchemistry could be a way to study reactions in very fine detail.

"[It's] a very appealing regime in terms of advancing our fundamental understanding of chemistry," Waseem Bakr, a physicist at Princeton University who studies ultracold atoms and molecules, told Live Science.

Quantum superchemistry also has scientists excited because it provides precise control over molecular quantum states.

That could be useful for quantum simulation, a cousin of quantum computers. Typically, scientists simulate quantum systems on "classical" systems, such as conventional computers. But many processes, such as high-temperature superconduction, might be better modeled using quantum systems that are governed by the same quantum rules. Quantum superchemistry would give scientists a tool for producing molecules in specific quantum states that would enable those simulations, Bakr said.

Heinzen sees plenty of reasons for scientists to keep exploring the phenomenon he helped dream up more than 20 years ago. While the applications are little more than pipe dreams right now, history has shown that advances in fundamental science can sometimes lead to surprising applications down the road.

"It's not obvious right now," he said. "But it's still really worth doing."

But why is bismuth so strongly repelled from magnets?

According to Eric Riesel, a magnetic materials chemist at MIT, the answer comes down to the type of magnetism exhibited by bismuth. Every material has magnetic properties, determined by a quantum property of the element's electrons known as spin. But, this spin can only point in two directions — up or down — and the combination of all the spins in a material define exactly what type of magnetism the element will exhibit.

"Most people are familiar with ferromagnets (permanent magnets) like iron, where the spins are all aligned with each other, but there are also anti-ferromagnets where the spins are pointed in opposite directions to each other," Riesel told Live Science.

However, there's also another pair of magnetic categories: paramagnetism and diamagnetism. "In paramagnets, when you apply a magnetic field, spins in that material will align with the field in proportion to its strength," he said. "Diamagnets apply a force in the opposite direction to the field, repelling it."

Related: Is it possible to reach absolute zero?

Bismuth is an example of a diamagnetic material, yet this is not the behavior we would expect from the element's electron configuration. The type of magnetism exhibited by a material depends on the arrangement of electrons and their corresponding spins. Electrons circle the nucleus in defined layers called shells, which are further subdivided into levels called the s, d, p and f orbitals.

Typically, diamagnetic materials have a closed shell structure. This means a particular group of orbitals are completely full and the electrons have been forced to pair, with one pointing up and the other down — essentially canceling out the spins. Conversely, paramagnetic materials usually have partially filled orbitals, meaning the electrons are unpaired and can align their spins in the same direction.

Bismuth is in Group 15 of the periodic table. The s, d and f orbitals are all full, but the p orbitals contain three out of a possible six electrons. So bismuth has partially filled orbitals and should behave as a paramagnet. However, its position in row six of the periodic table means bismuth also possesses some unusual heavy-atom properties.

"Chemical elements found after the f-block in the periodic table have their outermost electrons orbiting the nucleus at speeds that are significant fractions of the speed of light," said Ira Martyniak, also a magnetic materials chemist at MIT. "The direct relativistic effect makes the 6s and 6p orbitals contract and reside closer to the nucleus, which gives rise to anomalous physical and chemical characteristics."

These relativistic effects are responsible for many of bismuth's surprising properties, such as its unconventional superconductivity, its very low melting point (520.7 degrees Fahrenheit, or 271.5 degrees Celsius) and the unusual shape of its crystals. The unexpected diamagnetism is no exception.

"Even though bismuth has the unpaired electrons in its 6p orbital, because of relativistic contraction of the 6s and 6p levels, the paramagnetism stemming from the 6p electrons is suppressed and the behavior of bismuth is largely dominated by the closed shells and large size of the atom, leading to strong diamagnetism," Martyniak told Live Science.

Diamagnetic materials have lots of valuable applications, including electromagnetic induction in copper coils (used to generate electricity) and the aluminum tracks of high-speed maglev trains. Bismuth itself is too heavy to be a practical material for general use, but its potent diamagnetism means it is now a common component in superconductors and quantum computing.

BC8, as the superstrong carbon is known, is an eight-atom crystal that would be 30% more resistant to compression than diamonds, according to a new study. Scientists have been trying to synthesize this crystal in the lab, without success. The new simulation reveals that the material can be made only in a narrow range of pressures and temperatures, which might make that synthesis possible in the future, researchers reported in the study, which was published in The Journal of Physical Chemistry Letters in January.

The research also helps to reveal what might be at the hearts of carbon-rich exoplanets, which are predicted to have just the right conditions for the formation of BC8.

Related: 'Mind-boggling' alloy is Earth's toughest material, even at extreme temperatures

"[T]he extreme conditions prevailing within these carbon-rich exoplanets may give rise to structural forms of carbon such as diamond and BC8," study senior author Ivan Oleynik, a physics professor at the University of South Florida, said in a statement. "Therefore, an in-depth understanding of the properties of the BC8 carbon phase becomes critical for the development of accurate interior models of these exoplanets."

In the new research, Oleynik and his colleagues used Frontier, a supercomputer at the Oak Ridge Leadership Computing Facility in Tennessee. They ran simulations of billions of carbon atoms under different pressures and temperatures to understand how these amply available atoms can transform into a material so rare, it's never been observed.

They found that BC8 is likely very stable at very high pressures of 1,250 gigapascals and above. That's well over 12 million times the pressure of the atmosphere on Earth's surface. Theory also suggests, however, that the crystal, once formed, would remain stable at ambient temperatures. BC8's atomic structure is similar to a diamond's, but it lacks diamonds' cleavage planes, the gemstones' weakest points, study co-author Jon Eggert, a scientist at Lawrence Livermore National Laboratory (LLNL), said in a statement.

Armed with their new knowledge of BC8's formation pathways and stability, the researchers are making new attempts to synthesize the material at LLNL's National Ignition Facility. These types of methods involve shocking diamonds twice at upward of 45,000 mph (72,000 km/h) and then compressing them under enormous pressures.

Static electricity is the result of an imbalance between negative and positive electrical charges in an object, according to the U.S. Library of Congress. These charges can amass on an object's surface until they find a way to discharge.

The most common cause of static electricity is a phenomenon known as triboelectricity, Pourya Shamsi, a power electronics engineer at the Missouri University of Science and Technology, told Live Science. When two materials repeatedly touch and then separate, the surface of one material can steal electrons from the surface of the other. This is why rubbing socks on a carpet or running a plastic comb through hair can build up electric charge. In essence, negative electrons are leaving one object for the other. Then, when you touch something, like your cat or dog, you'll get a shock as the extra electrons rapidly leave.

In the case of rubbing a balloon on your shirt, the balloon receives a surplus of electrons, whose negative charge helps the balloon stick to the wall, which is now more positively charged than the balloon, according to the Library of Congress.

The most powerful display of static electricity on Earth is lightning, Shamsi said. Collisions between droplets of rain and ice crystals within clouds can lead huge amounts of static electricity to build up, according to the National Weather Service. Lightning discharges can pack "as much as 5 gigajoules of energy, which is enough to set multiple trees on fire in an instant," Shamsi said.

In comparison, the amount of static charge that might build up on a person is hundreds of billions of times less, reaching about 40 millijoules of energy, Shamsi said. That is about as much energy as a typical LED indicator light might use in one second, according to electronics design firm Cadence.

Related: What makes something fireproof?

However, "even this small amount of energy is sufficient to damage sensitive electronic devices or start a fire," Shamsi said.

Most human-involved static electricity fires start with flammable fuel vapors and gases, Shamsi said. Specifically, "the most common everyday situations for starting a fire would be at gas pumps," Mark Lambert, director of the West Virginia State Fire Training Academy, told Live Science.

Static electricity on a person can discharge as an electric spark — on a pump handle, for instance — that can set fire to flammable material. To prevent fires at gas stations, "touch metal or the car door with your bare hand" before you use the pump, Lambert said. "This will discharge static electricity on your body and will prevent possible fire."

Importantly, "once the gasoline is pumping, do not get back into your vehicle," Lambert said. "This can recharge your body with static electricity."

The liners of truck beds can build up static electricity as well. "You should always remove gas cans from the bed of a truck to fill them at a pump," Lambert noted.

In addition to gas stations, "in industrial settings, static electricity can set fire to fine dusts, including fine wood dust, aluminum dust, and even wheat flour," Shamsi said. Powders and other items moving around inside a facility can lead to a buildup of static electricity on surfaces that can then discharge onto the dust, making it burn. "An average person might not consider aluminum or the bread they are eating as combustible," Shamsi said. "But when both are turned into fine powder, both can combust due to a static electricity discharge."

All in all, "people working with combustible fuels, including hydrocarbons and fine dust, should discharge themselves prior to handling the fuel or entering those environments," Shamsi said.

But blue is a rare color in nature and few naturally occurring organic compounds give living things this color. So why exactly are blueberries blue?

It turns out that scientists recently figured out this conundrum — and it's not the fruit skin.

In a study published Feb. 7 in the journal Science Advances researchers found that tiny, randomly-arranged crystals in the fruit's waxy coating scatter light, giving blueberries their signature indigo appearance.

Blue hues rarely turn up in living things. The majority of examples, such as bluebells, butterflies and tropical frogs, rely on clever trickery to produce this shade (mainly to deter predators). Even blue rocks and minerals, like sapphires and lapis lazuli, are hard to come by.

And blueberries were even more of a mystery. 

"The blue of blueberries can't be 'extracted' by squishing — because it isn't located in the pigmented juice that can be squeezed from the fruit. That was why we knew that there must be something strange about the color," study lead researcher Rox Middleton, a researcher at the University of Bristol in the U.K., said in a statement.

While blueberries contain strong pigments called anthocyanins, these have a deep reddish-purple color, completely different from the indigo shade of the fruit skin. However, like most plants, blueberries are coated in a thin layer of protective wax which acts as a waterproof coating and barrier against infection.

Middleton's team suspected the blue hue must come from outside of the fruit. So they removed a sample of this wax and recrystallized it on a piece of cardboard. To their delight, this created an ultra-thin crystalline coating with blueberry's trademark indigo color. When they looked closely at this layer, they found a random distribution of crystal structures within the wax which scatter blue and UV light to produce the fruit's signature color.

"It shows that nature has evolved to use a really neat trick, an ultrathin layer for an important colorant," Middleton said. "It was even more exciting to be able to reproduce that color by harvesting the wax to make a new blue coating that no-one's seen before."

The discovery opens up exciting opportunities for sustainable and biocompatible blue coatings and colorants. These could be used in everything from sensors, to construction, to automotive paints, the researchers wrote in the study. But the extensive and largely unknown functions of these waxes in plants also means that these new colorants potentially have many other beneficial properties which researchers haven't even begun to explore yet.

The team is now seeing if there are simpler ways to prepare and apply the wax.

"Building all that functionality of this natural wax into artificially engineered materials is the dream!" Middleton said.

It turns out, all elements have magnetic properties. The metals we typically consider magnetic — iron, nickel and cobalt — are a special class of elements known as ferromagnets, which interact particularly strongly with magnetic fields and make permanent magnets.

But there are several other, much weaker types of magnetism, said Michael Coey, a professor emeritus of physics at Trinity College Dublin. Most elements are either paramagnetic or diamagnetic. "With paramagnets, when you apply a magnetic field, you get a very small magnetization in the direction of the field," he said. This means that the element is very slightly attracted to the magnet, but the effect is only temporary and disappears as soon as the magnet is removed.

"For diamagnets, when you apply a magnetic field, you get an even smaller magnetization in the opposite direction to the field," Coey told Live Science. This creates a tiny repulsive force toward the magnet that, again, disappears without the magnetic field. So, under everyday conditions, we would never notice that paramagnetic and diamagnetic materials have any magnetic properties.

Copper is an example of a diamagnetic material, but exactly which category an element falls into depends on the electrons. These negatively charged particles orbit the central nucleus of an atom in defined layers called shells, which are further divided into levels called the s orbital, the d orbitals and the p orbitals.

Related: Why does copper turn green?

For metals in the center of the periodic table, the s orbital is already filled with two electrons, and moving from left to right across the row, the d orbitals gradually fill with a maximum of 10 electrons. As the orbitals fill up, electrons are forced to pair, and this determines the elements' magnetic properties. Elements with more unpaired electrons are paramagnetic, and those with more paired electrons are diamagnetic.

Each electron also possesses a strange quantum property called spin. The direction (up or down) of all of the electron spins in an atom defines the strength of the magnetism. "When different electrons align their spins in parallel [in the same direction], the atom has a magnetic moment," Coey said. "But if the electrons align their spins antiparallel [in opposite directions], the magnetic moment cancels out."

Copper is in the ninth position, so we would expect it to have two electrons in the s orbital and nine in the d orbitals. But unusually, copper takes one electron out of the full s orbital to completely fill up the d orbitals instead. This means all of the d electrons are paired, with equal numbers spinning up and down. Consequently, there is no magnetic moment, so we don't observe any magnetic behavior under normal conditions.

However, this unusual configuration means that copper can interact with magnets in a different and extremely important way. Magnetism is closely linked with electricity — a phenomenon described in physics by Lenz's law.

"In essence, a changing magnetic field will induce a current within a conductor," said Ernesto Bosque, a physicist at the National High Magnetic Field Laboratory in Florida. "Because copper has such a low electrical resistance, currents can flow very easily in [it]."

It's the unpaired s electron that makes copper such an excellent conductor. This effect, known as electromagnetic induction, is central to how we generate electricity today. "A stator is essentially a set of rotating insulated wires that move around a core. This can be used as a motor or a generator," Bosque told Live Science in an email. The same idea also works in reverse: A current passed through coils of wire can generate a magnetic field in a metal core, creating an electromagnet.

Copper's ability to interact with a magnet, despite not being ferromagnetic, is something we rely on every day to power electronic devices, store data on hard drives, and even slow down roller coasters.

Researchers uncovered traces of the Barbenheimer Star after taking a closer look at J0931+0038, a distant red giant star. J0931 was first discovered in 1999 by the Sloan Digital Sky Survey (SDSS) — one of the largest and most detailed astronomical databases of the night sky — but had not been properly analyzed until now. 

In a new study uploaded to the preprint server arXiv on Jan. 4, researchers turned the SDSS telescopes in New Mexico back toward J0931 and captured a detailed spectrum of the star's light, which was later verified by follow-up observations from the Giant Magellan Telescope in Chile. These spectra revealed that J0931 seemingly had an extremely odd metallicity, or chemical composition, with an unusually high concentration of heavy elements. (These results have not yet been peer-reviewed.)

Using the newly acquired data, the research team pieced together how J0931 formed via a process known as stellar archaeology. This revealed that the star was birthed from the supernova remnant of an even larger star — between 50 and 80 times more massive than the sun — that dates back as far as 13 billion years ago, only around 700 million years after the Big Bang.

The metallicity of the parent star (Barbenheimer) was likely equally as weird as that of J0931 before it blew up, which would have been completely different from other known stars in the early universe.

"We've never seen anything like this," study lead author Alex Ji, an astrophysicist at the University of Chicago, said in a statement. "Whatever happened back then, it must have been amazing."

Related: 1st evidence of nuclear fission in stars hints at elements 'never produced on Earth'

J0931's metallicity was strange for three reasons. First, the star had unusually low levels of lighter elements such as magnesium, sodium and aluminium, which are normally more abundant in stars. Second, it had an unusually high amount of midweight elements such as iron, nickel and zinc. And finally, it had an "overabundance" of heavier elements like strontium and palladium, according to the researchers.

"We sometimes see one of these features at a time, but we've never before seen all of them in the same star," study co-author Jennifer Johnson, an astronomer at The Ohio State University, said in the statement.

Most stars have the reverse metallicity of J0931: They have higher levels of lighter elements and lower levels of midweight and heavier elements. This is because stars are made predominantly of hydrogen and helium, which fuse together in the stars' cores to create heavier elements. These new elements, which are much less abundant, eventually fuse into heavier and heavier elements. 

It is therefore hard to explain why J0931 has such and abundance of heavy elements because it doesn't seem to have a high enough concentration of lighter elements to have created them. 

"Amazingly, no existing model of element formation can explain what we see," said study co-author Sanjana Curtis, an astronomer at the University of California, Berkeley. It "almost seems self-contradictory," she said.

J0931's unusual metallicity would have partially been inherited from the ingredients that the Barbenheimer Star spit out when it exploded. This means that the parent star would likely have had a similarly inverted metallicity. This is even stranger, because in the early universe, stars shouldn't have existed long enough to have created such high concentrations of heavy elements, the team said.  

But what's even stranger is that the Barbenheimer Star should have never gone supernova, the researchers wrote. In theory, a star with Barbenheimer's predicted mass should have collapsed into a black hole rather than exploding outward. At the moment, the study team cannot explain why this collapse didn't happen. 

The only way for scientists to learn more about the Barbenhaimer Star and its bizarre composition is to search for other similar stellar oddballs from the early universe to uncover more pieces of this cosmic puzzle.

"The universe directed this movie, we are just the camera crew," study co-author Keith Hawkins, an astronomer at the University of Texas at Austin, said in the statement. "We don't yet know how the story will end."

"Stools are generally not a pleasant smell because they are releasing byproducts of your digestion," Shelby Yaceczko, a clinical dietician at UCLA Health, told Live Science.

Skatole, also known as 3-methylindole, is "one of the compounds in feces that gives it its foul smell," Emma Laing, a clinical professor and director of dietetics at the University of Georgia and a spokesperson for the Academy of Nutrition and Dietetics, told Live Science. Bacteria make this compound when they break down the amino acid L-tryptophan in the gastrointestinal tract, she said. (Oddly enough, the same compound in small concentrations gives a pleasant smell to flowers like jasmine, according to the American Chemical Society.)

Related: Why do some men take so long to poop?

There are more than 10,000 microbial species living in humans and more bacterial cells than human ones. These microorganisms are essential to digestion and largely to blame for feces' odor. Different bacteria emit different gases depending on the types of foods and substances they are breaking down, Laing explained; bacteria in the gastrointestinal tract and the mouth contribute to this process, she said.

Because bacteria break down what we eat, factors such as dietary patterns, alcohol intake, dietary supplements and prescription medication can affect the way poop smells. Sugar alcohols, like sorbitol, are often used in candies and can make poop smell particularly bad. And sulfate-containing foods — like eggs, broccoli, cabbage, cauliflower, onions, legumes and meat — can contribute to the production of sulfur gas, which has a rotten egg smell, during digestion.

Highly processed and sugary foods can be difficult to digest, leading bacteria to produce more gases and stinkier poo, Yaceczko said. And consuming large amounts of alcohol produces smelly stools because it wreaks havoc on the intestines and the digestive process, Laing added.

If you notice a change or worsening in the smell of your stool, it's most likely due to a change in your diet or medication, Laing said. The digestive process eventually adjusts, and the worsened smell is usually temporary, she added.

However, an especially foul smell, like a putrid or rotten odor, that doesn't go away could indicate a serious health problem. Malabsorption diseases, like inflammatory bowel disease or celiac disease, can prevent the body from digesting and absorbing nutrients, which can cause consistently foul odors. A viral or bacterial infection in the gut could also be to blame. And so-called motility disorders, which cause a slower-than-normal emptying of the gastrointestinal tract, give poop a longer time to ferment, thus increasing the stink, Yaceczko said.

If an unusually bad smell persists, especially in combination with symptoms such as diarrhea, blood in the stool, abdominal pain or fever, "a prompt visit to your health care provider is warranted," Laing said.

This article is for informational purposes only, and is not meant to offer medical advice.

Floating ice is "such a fundamental fact of the world, it's hard to truly imagine what the world would be like [without it]," said Brent Minchew, an associate professor of geophysics at the Massachusetts Institute of Technology. 

But did you ever stop to think why ice floats on water, instead of sinking to the bottom? It has to do with the density of water.

Water ice, the solid state of water, floats because it is less dense than its liquid form. Most other substances, by contrast, become denser in the solid phase.

"Water is a very unusual substance," Claire Parkinson, a former climatologist at NASA's Goddard Space Flight Center in Maryland, told Live Science.

Related: Why is ice slippery?  

Ice cubes float because of their molecular structure. A water molecule (H2O) is made of two hydrogen atoms and one oxygen atom. The hydrogen and oxygen atoms share electron pairs, forming covalent bonds. The positive charge of a hydrogen atom is attracted to the negatively charged oxygen atom of another water molecule, and the bond that forms between these molecules is known as a hydrogen bond. 

When water freezes, these hydrogen bonds form a crystal lattice, Minchew told Live Science. Most of the ice on Earth's surface forms repeating hexagonal crystals. There's a lot of empty space within this lattice structure that fills with air, Minchew said, leading to ice's lower density.

This is why icebergs float in the ocean, even though they are between roughly 100 and 165 feet (30 and 50 meters) thick, according to the National Oceanic and Atmospheric Administration. That's a good thing, since floating ice allows life to flourish beneath the frozen surface of lakes and oceans. If ice sank, that would be a problem for the marine and aquatic life currently living in these underwater habitats, Parkinson said. 

Sea ice, which floats on top of the ocean's surface, is also crucial for ocean circulation, according to NASA's Earth Observatory. As it freezes, sea ice exudes salt and makes the water beneath it extremely salty and dense. This dense water created by the sea ice sinks to the bottom of the ocean and pushes up deep water to the surface, helping to circulate ocean water worldwide, Minchew explained. 

The fact that ice floats could have profound impacts on some climate change tipping points. The West Antarctic ice sheet is an extension of ice that connects to land and is Antarctica's biggest contributor to sea level rise. A 2023 study published in the journal Nature Climate Change predicts that the floating ice shelves that make up the West Antarctic Ice Sheet will diminish rapidly over the next century as warming oceans melt the ice shelf from below. 

This is part of a buoyancy-driven feedback of ocean temperatures on sea level rise, Minchew said, "all just because ice floats."

These enriched dust grains are then swept up into newly forming stars and solar systems, eventually becoming part of planets like Earth. The new study shows that the complex chemistry that fuels life doesn’t require an injection of energy or an exotic process to get going.

Galaxies are great at building the fundamental elements. Hydrogen and helium have been around since the first few minutes of the Big Bang. Sun-like stars fuse hydrogen into more helium, and near the ends of their lives these stars turn that helium into carbon and oxygen. Larger stars keep the fusion chain going, producing potassium, nickel, iron and more. And lastly, titanic supernova explosions fill out the rest of the periodic table.

Related: NASA reveals 1st sample collected from potentially hazardous asteroid Bennu to public — and it may contain the seeds of life

Some elements bind together easily and naturally. For example, hydrogen and oxygen are both very common and enjoy binding together, even in the depths of space, making water an incredibly common molecule. But creating a living creature requires far more complex molecules than just water. Now, many of those molecules on Earth are made as byproducts of biological reactions, but for life to get started on our planet billions of years ago, there must have been at least some complexity in that primordial soup to get going.

Astronomers have recently identified complex organic molecules — molecules rich in carbon and oxygen — in many unexpected places. Saturn's moon Titan contains vast seas of hydrocarbons. Dust grains pulled from comets and asteroids are rich in organic molecules. We've even observed traces of organic molecules embedded deep within interstellar gas clouds.

Now, in a new paper, uploaded Oct. 23 to the preprint server arXiv, a team of astronomers is discovering the origins of these organic molecules. Unlike previous work, which looks to higher-energy events and locations as a source of synthesizing new molecules, the team examined whether the conditions of deep space would be enough to create the molecules.

The team ran computer simulations of the chemical relationships between elements found in the depths of space. There, tiny grains of dust get cold enough that they enshroud themselves in a layer of ice. Floating among this dust are carbon atoms, ejected from stellar explosions thousands of light-years away. The team found that the carbon atoms quickly react with frozen water, forming a simple molecule containing carbon, oxygen and hydrogen, designated as carbonous acid. Because this molecule has open electron spots, it is highly reactive and immediately begins combining and reacting with other elements and molecules in the dust.

For example, the reactive carbons can find nitrogen to make the base for cyanides, or oxygen to make carbon monoxide. These can then go on to form methanol, considered the "mother" of organic molecules, the researchers wrote. Other reactions can produce ethanol, methanimine and methanediol, which play a variety of roles in biological chemistry.

In other words, all that's needed to jump-start life is incredibly cold atoms interacting with each other in the vacuum of space.

Now, two scientists are revealing the results of their years spent cataloging "odious materials" from archaeology collections around the U.S. In a study published Oct. 19 in Advances in Archaeological Practice, University of Idaho archaeologist Mark S. Warner and his colleague, chemist Ray von Wandruszka, summarized the 15 years they have spent identifying and testing noxious substances from archaeological artifacts.

Their hunt for the grossest objects lurking in museums began when a large excavation of the 19th-century town of Sandpoint in northern Idaho in 2008 uncovered sealed glass bottles with mysterious contents among the other nearly 600,000 artifacts.

Warner and von Wandruszka teamed up to identify what was inside them. They found examples of creams and ointments, iron tonic, and wood tar in the sealed containers, along with empty bottles labeled “poison”, bullets containing gunpowder, and even a human tooth with a zinc-based filling.

Archaeologists at the site also found a bottle of "Gouraud's Oriental Cream." The creamy white substance turned out to be mercurous chloride, also called calomel, which was used throughout the 18th and 19th centuries for everything from preventing acne to treating yellow fever, until doctors realized that mercury was actually quite poisonous.

From a site in California, the researchers also tested a small jar of ant paste made by Kellogg's in the early 20th century and found that it still contained arsenic. They also found an ampule of toxic, phosphorus-based rodenticides from an old hospital in New England and aluminum phosphide tablets from a school site in Florida.

Some of the odious objects are toxic; others are just gross.

A sealed bottle of malt whiskey from a historic site in Washington state contained urea — an organic compound found in urine. "The bottle was used as a vessel of convenience, in order to avoid a nighttime trip to the outhouse," the researchers wrote in their study.

Not knowing exactly what kind of stuff is on the shelves of archaeological collections can be problematic, the researchers noted in the study. "A broken ampule of phosphide or a leaking bottle of 100-year-old urine may only lead to a nasty cleanup job, but it could be much worse," they wrote.

That's why archaeological collection managers should identify objects that retain their contents and why field workers should receive training for how to handle potentially toxic substances they might find, the researchers said. Once found, having an analytical chemist test the material is ideal.

Most of the icky substance detective work for this project is done via infrared or atomic absorption spectrometry at the University of Idaho's chemistry department by undergraduate students majoring in chemistry or biology, von Wandruszka told Live Science in an email. "The project is tremendous training for students," Warner said.

Warner's and von Wandruszka's work "is a great model for other universities and museums to emulate," Katie Stringer Clary, a specialist in public history and museum studies at Coastal Carolina University who was not involved in the study, told Live Science in an email. "Who knows what other noxious or intriguing items could be uncovered in archaeological collections with further interdisciplinary investigation?"

Warner noted that the team is always on the lookout for new substances to test. "We do this work for free," Warner said. He cautioned, though, that "people should probably touch base with us beforehand regarding the materials they want to test." No one wants an ampule of phosphorus to explode in the mail.

Scientists discovered hints of the new isotope, called nitrogen-9, by smashing beams of oxygen isotopes into beryllium atoms in the U.S. National Superconducting Cyclotron Laboratory. 

If follow-up experiments can confirm its existence, the isotope will set a new record for an atomic nucleus with the highest number of extra protons — moving the number from four to five. The researchers described the strange new isotope Oct. 27 in the journal Physical Review Letters.

Related: Scientists discover 1st 'neutron-rich' isotope of uranium since 1979

The ultra-unstable version of nitrogen decays like a Russian nesting doll, sequentially emitting one or two protons while revealing the next set, Robert Charity, a nuclear scientist at Washington University in St. Louis, said in a statement. 

Protons and neutrons are held together inside atomic nuclei by the strong force, a glue which in stable atoms overpowers the repulsive force of positively-charged protons pushing against each other. But add more protons and this balance eventually tips — moving atoms beyond the so-called "drip line." 

Beyond the drip line atoms become unstable, and decay by chucking out protons or neutrons. Because they exist on the furthest edge of possible atomic nuclei, semi-stable atoms beyond the drip line (which come in the form of rare isotopes) have long fascinated nuclear scientists.

"The existence of such an exotic system is a good test of the quantum mechanics of open or unbound many-body systems," Charity said.

The researchers found the first hints of nitrogen-9’s presence in data from a years-old experiment conducted by the National Superconducting Cyclotron Laboratory. Originally, the scientists smashed oxygen-13 atoms into beryllium in a bid to create another isotope called oxygen-11. 

But lurking among the millions of interactions was another decay signature that pointed to something else. Right on the borderline of statistical significance, the researchers spotted rare atoms of nitrogen-9 popping into existence for just 10^-21 seconds.

To get partial confirmation they had found the weird isotope, the scientists modeled the isotope’s structure, finding that it consisted of a helium nucleus with two protons and two neutrons surrounded by five loosely held protons. After the briefest slice of time the protons decayed, successively escaping the nucleus through a quantum tunnel.

Further experiments will be needed to confirm the discovery. They remain hopeful that, when they do, the isotope will help them to piece together the decay paths more common isotopes take to come into existence.

"The elements we have around us are made via a set of mechanisms that work through intermediates that we do not have around us," Lee Sobotka, a professor of chemistry and physics at Washington University, said in the statement. "These intermediates are unstable and often have highly unusual neutron-to-proton ratios. Our work involves both reconstructing the structure of, and reactions producing, such nuclei."

But let’s just get this out there first: it's not that chemists aren't curious. Since Russian chemist Dmitri Mendeleev invented the periodic table of elements in 1869, which is basically a chemist's box of Lego, scientists have been discovering the chemicals that helped define the modern world. We needed nuclear fusion (firing atoms at each other at the speed of light) to make the last handful of elements. Element 117, tennessine, was synthesised in 2010 in this way.

But to understand the full scale of the chemical universe, you need to understand chemical compounds too. Some occur naturally — water, of course, is made of hydrogen and oxygen. Others, such as nylon, were discovered in lab experiments and are manufactured in factories.

Elements are made of one type of atom, and atoms are made of even tinier particles including electrons and protons. All chemical compounds are made of two or more atoms. Although it's possible there are undiscovered elements left to find, it's unlikely. So, how many chemical compounds can we make with the 118 different sorts of element Lego blocks we currently know?

Big numbers

We can start by making all the two-atom compounds. There are lots of these: N2 (nitrogen) and O2 (oxygen) together make up 99% of our air. It would probably take a chemist about a year to make one compound and there are 6,903 two-atom compounds in theory. So that's a village of chemists working a year just to make every possible two-atom compound.

There about 1.6 million three-atom compounds like H₂0 (water) and C0₂ (carbon dioxide), which is the population of Birmingham and Edinburgh combined. Once we reach four- and five-atom compounds, we would need everyone on Earth to make three compounds each. And to make all these chemical compounds, we'd also need to recycle all the materials in the universe several times over.

But this is a simplification, of course. Things such as the structure of a compound and its stability can make it more complex and difficult to make.

The biggest chemical compound that has been made so far was made in 2009 and has nearly 3 million atoms. We're not sure what it does yet, but similar compounds are used to protect cancer drugs in the body until they get to the right place.

But wait, chemistry has rules!

Surely not all those compounds are possible?

It's true there are rules — but they are kind of bendy, which creates more possibilities for chemical compounds.

Even the solitary "noble gases" (including neon, argon and xenon and helium), which tend to not bind with anything, sometimes form compounds. Argon hydride, ArH+ does not exist naturally on Earth but has been found in space. Scientists have been able to make synthetic versions in laboratories that replicate deep space conditions. So, if you include extreme environments in your calculations, the number of possible compounds increases.

Carbon normally likes being attached to between one and four other atoms, but very occasionally, for short periods of time, five is possible. Imagine a bus with a maximum capacity of four. The bus is at the stop, and people are getting on and off; while people are moving, briefly, you can have more than four people actually on the bus.

Some chemists spend their entire careers trying to make compounds that, according to the chemistry rulebook, shouldn't exist. Sometimes they are successful.

Another question scientists have to grapple with is whether the compound they want can only exist in space or extreme environments — think of the immense heat and pressure found at hydrothermal vents, which are like geysers but on the ocean floor.

How scientists search for new compounds

Often the answer is to search for compounds that are related to ones that are already known. There are two main ways to do this. One is taking a known compound and changing it a bit — by adding, deleting or swapping some atoms. Another is taking a known chemical reaction and using new starting materials. This is when the method of creation is the same but the products may be quite different. Both of these methods are ways of searching for known unknowns.

Coming back to Lego, it's like making a house, then a slightly different house, or buying new bricks and adding a second storey. A lot of chemists spend their careers exploring one of these chemical houses.

But how would we search for truly new chemistry — that is, unknown unknowns?

One way chemists learn about new compounds is to look at the natural world. Penicillin was found this way in 1928, when Alexander Fleming observed that mould in his petri dishes prevented the growth of bacteria.

Over a decade later, in 1939, Howard Florey worked out how to grow penicillin in useful amounts, still using mould. But it took even longer, until 1945, for Dorothy Crowfoot Hodgkin to identify penicillin's chemical structure.

That's important because part of penicillin's structure contains atoms arranged in a square, which is an unusual chemical arrangement that few chemists would guess, and is difficult to make. Understanding penicillin's structure meant we knew what it looked like and could search for its chemical cousins. If you're allergic to penicillin and have needed an alternative antibiotic, you have Crowfoot Hodgkin to thank.

Nowadays, it's a lot easier to determine the structure of new compounds. The X-ray technique that Crowfoot Hodgkin invented on her way to identifying penicillin's structure is still used worldwide to study compounds. And the same MRI technique that hospitals use to diagnose disease can also be used on chemical compounds to work out their structure.

But even if a chemist guessed a completely new structure unrelated to any compound known on Earth, they'd still have to make it, which is the hard part. Figuring out that a chemical compound could exist does not tell you how it's structured or what conditions you need to make it.

For many useful compounds, like penicillin, it's easier and cheaper to "grow" and extract them from moulds, plants or insects. Thus the scientists searching for new chemistry still often look for inspiration in the tiniest corners of the world around us.

This edited article is republished from The Conversation under a Creative Commons license. Read the original article.