For the first time, scientists have discovered nuclear fission occurring amongst the stars, supporting the idea that neutron stars create "superheavy" elements when they collide, which then break down via nuclear fission to birth rare elements. Space.com reports: Nuclear fission is basically the opposite of nuclear fusion. While nuclear fusion refers to the smashing of lighter elements to create heavier elements, nuclear fission is a process that sees energy released when heavy elements split apart to create lighter elements. Nuclear fission is pretty well known, too. It's actually the basis of energy-generating nuclear power plants here on Earth -- however, it had not been seen occurring amongst the stars before now.

The team of researchers led by North Carolina State University scientist Ian Roederer searched data concerning a wide range of elements in stars to discover the first evidence that nuclear fission could therefore be acting when neutron stars merge. These findings could help solve the mystery of where the universe's heavy elements come from. Scientists know that nuclear fusion is not just the primary source of energy for stars, but also the force that forges a variety of elements, the "heaviest" being iron.

The evidence of nuclear fission discovered by [Matthew Mumpower, research co-author and a scientist at Los Alamos National Laboratory] and the team comes in the form of a correlation between "light precision metals," like silver, and "rare earth nuclei," like europium, showing in some stars. When one of these groups of elements goes up, the corresponding elements in the other group also increases, the scientists saw. The team's research also indicates that elements with atomic masses -- counts of protons and neutrons in an atomic nucleus -- greater than 260 may exist around neutron star smashes, even if this existence is brief. This is much heavier than many of the elements at the "heavy end" of the periodic table. "The only plausible way this can arise among different stars is if there is a consistent process operating during the formation of the heavy elements," Mumpower said. "This is incredibly profound and is the first evidence of fission operating in the cosmos, confirming a theory we proposed several years ago."

"As we've acquired more observations, the cosmos is saying, 'hey, there's a signature here, and it can only come from fission.'"

The research was published in the journal Science.

A new study from the University of Warwick found that artificial intelligence can analyze X-rays and diagnose medical issues better than doctors. The BBC reports: Software was trained using chest X-rays from more than 1.5m patients, and scanned for 37 possible conditions. It was just as accurate or more accurate than doctors' analysis at the time the image was taken for 35 out of 37 conditions, the University of Warwick said. The AI could reduce doctors' workload and delays in diagnosis, and offer radiologists the "ultimate second opinion," researchers added. The software understood that some abnormalities for which it scanned were more serious than others, and could flag the most urgent to medics, the university said.

To check the results were accurate, more than 1,400 X-rays analysed by the software were cross-examined by senior radiologists. They then compared the diagnoses made by the AI with those made by radiologists at the time. The software, called X-Raydar, removed human error and bias, said lead author, Dr Giovanni Montana, Professor of Data Science at Warwick University. "If a patient is referred for an X-ray with a heart problem, doctors will inevitably focus on the heart over the lungs," he said. "This is totally understandable but runs the risk of undetected problems in other areas".

An anonymous reader quotes a report from Ars Technica: Thirty years ago, a botanist in Germany had a simple wish: to see the inner workings of woody plants without dissecting them. By bleaching away the pigments in plant cells, Siegfried Fink managed to create transparent wood, and he published his technique in a niche wood technology journal. The 1992 paper remained the last word on see-through wood for more than a decade, until a researcher named Lars Berglund stumbled across it. Berglund was inspired by Fink's discovery, but not for botanical reasons. The materials scientist, who works at KTH Royal Institute of Technology in Sweden, specializes in polymer composites and was interested in creating a more robust alternative to transparent plastic. And he wasn't the only one interested in wood's virtues. Across the ocean, researchers at the University of Maryland were busy on a related goal: harnessing the strength of wood for nontraditional purposes.

Now, after years of experiments, the research of these groups is starting to bear fruit. Transparent wood could soon find uses in super-strong screens for smartphones; in soft, glowing light fixtures; and even as structural features, such as color-changing windows. "I truly believe this material has a promising future," says Qiliang Fu, a wood nanotechnologist at Nanjing Forestry University in China who worked in Berglund's lab as a graduate student. Wood is made up of countless little vertical channels, like a tight bundle of straws bound together with glue. These tube-shaped cells transport water and nutrients throughout a tree, and when the tree is harvested and the moisture evaporates, pockets of air are left behind. To create see-through wood, scientists first need to modify or get rid of the glue, called lignin, that holds the cell bundles together and provides trunks and branches with most of their earthy brown hues. After bleaching lignin's color away or otherwise removing it, a milky-white skeleton of hollow cells remains. This skeleton is still opaque, because the cell walls bend light to a different degree than the air in the cell pockets does -- a value called a refractive index. Filling the air pockets with a substance like epoxy resin that bends light to a similar degree to the cell walls renders the wood transparent.

The material the scientists worked with is thin -- typically less than a millimeter to around a centimeter thick. But the cells create a sturdy honeycomb structure, and the tiny wood fibers are stronger than the best carbon fibers, says materials scientist Liangbing Hu, who leads the research group working on transparent wood at the University of Maryland in College Park. And with the resin added, transparent wood outperforms plastic and glass: In tests measuring how easily materials fracture or break under pressure, transparent wood came out around three times stronger than transparent plastics like Plexiglass and about 10 times tougher than glass. "The results are amazing, that a piece of wood can be as strong as glass," says Hu, who highlighted the features of transparent wood in the 2023 Annual Review of Materials Research.

Meghan Bartels reports via Scientific American: Some sky watchers this month will witness Betelgeuse, one of the brightest and best-known stars in the sky, nearly disappear. Mere seconds later -- despite astronomers' hopes that the star will meet its explosive end someday soon -- it will return, shining just as brightly as ever. Betelgeuse's brief blip of obscurity will mark a cosmic coincidence: an asteroid will block the star from view over a thin strip of Earth's surface. Scientists are hailing this celestial alignment as a once-in-a-lifetime occasion that, they hope, will permit them to glimpse Betelgeuse's ever changing surface of hot and cold patches in the best resolution to date. The opportunity comes courtesy of a sizable asteroid called Leona, which astronomers first spotted in 1891. On its own, Leona is just another space rock cluttering up the asteroid belt between Mars and Jupiter. But at 8:17 P.M. ET on December 11 Leona will slip directly between Earth and Betelgeuse, a red supergiant star that, unlike the asteroid, has been recognized by countless generations of humans around the world. [...]

To understand how special the event is, consider the total solar eclipse that will occur in April 2024. During the climax of the eclipse, viewers across a narrow strip of Earth's surface will see the moon pass directly in front of the sun. Because the two bodies appear as the same size in our sky, the moon will entirely block the visible disk of the sun and expose the faint, wispy halo called the corona, a layer of our home star's atmosphere that scientists otherwise cannot see from Earth. Similarly, the roughly 40-mile-wide Leona appears in the sky as about the same size as the enormous but very distant Betelgeuse. This will allow the asteroid to block all or most of the star's light when the two bodies perfectly align. But whereas Earth experiences a total solar eclipse every 18 months or so, occultations of bright stars such as Betelgeuse are extremely rare, occurring less than once a century [...].

Long-time Slashdot reader schwit1 shared an interesting article from ScienceAlert: Undersea volcanic eruptions account for more than three-quarters of all volcanism on Earth, but rarely do we see the impacts. The Hunga Tonga-Hunga Ha'apai eruption of 2022 was a dramatic exception. Its furious explosion from shallow waters broke the ocean surface and punched through the stratosphere, generating supercharged lighting and an atmospheric shock wave that circled the globe several times.

But there was far more to the fallout than satellite images could possibly capture or observers could report. We know the human toll this explosion took, but now a new study investigating the underwater impacts of the Hunga-Tonga eruption has detailed just how ferociously the explosion tore open the seafloor, ripped up undersea cables, and smothered marine life... The team also compiled a trove of data from ship-based sonar, sediment cores, geochemical analyses, water column samples, and video footage to chart the devastatingly powerful upheaval...

Their analyses show at least 6 cubic kilometers (km3) of seafloor was lost from within the caldera — 20 times the eruptive volume of the 1980 Mount St. Helens eruption — and an additional 3.5 km3 of material was blasted out of the Hunga volcano's submerged flanks... That leaves roughly four-fifths of the ejected material in the ocean; material that was funneled into fast-moving density flows that scoured out tracks 30 meters deep in the seafloor and accumulated 22 meters (72 feet) thick in some places.

"The United States military is preparing to launch its secretive X-37B space plane on a seventh mission in orbit," reports NBC News.

Shaped like a small space shuttle, "It's an itty-bitty spaceplane, not quite 30 feet long and under 10 feet tall," writes the Washington Post, "with a pair of stubby wings and a rounded, bulldog-like nose." Space.com says the launch window for the uncrewed vehicle opens Monday at 8:14 p.m. EST.

From NBC News: For the first time, the X-37B will ride into orbit atop a SpaceX Falcon Heavy rocket. Since its debut more than a decade ago, the X-37B has been a source of intrigue within the space community, mostly owing to the mysterious nature of its activities in low Earth orbit. Despite not knowing its true purpose or location, skywatchers have occasionally spotted and photographed the space plane in the night sky using telescopes... The military is tight-lipped about such operations, but the Space Force said the X-37B missions "are key to ensuring safe and responsible operations in space for all users of the space domain..."
The "U.S. Space Force says that launching on SpaceX's Falcon Heavy rocket will allow testing "in new orbital regimes, experimenting with space domain awareness technologies and investigating the radiation effects to NASA materials."

The Washington Post notes that "The reference about 'space domain awareness' could mean that it will be keeping an eye on other satellites, potentially watching for threats": At least one part of the mission is known. The vehicle will "expose plant seeds to the harsh radiation environment of long-duration spaceflight" in an experiment for NASA. In the past, the Pentagon has also used the X-37B to test some of its cutting edge technologies, including a small solar panel designed to transform solar energy into microwaves, a technology that one day could allow energy harnessed in space to be beamed back to Earth...

If Sunday's X-37B mission is like previous ones, the spaceplane could be in space for a while. Its first flight, which launched in 2010, lasted 224 days.

Every five years America's federal Department of Health updates its dietary guidelines with the latest nutrition science, affecting federal nutrition programs and various other government health initiatives.

Now an anonymous reader shared this report from the Wall Street Journal: Botanists count potatoes as a vegetable. But should Americans? The U.S. Dietary Guidelines Advisory Committee has sparked the question... White potatoes, which come in various colors, are classified as "starchy vegetables." But the committee could uproot potatoes from the vegetable bin and toss them in with a broader category of rice, other grains and carbohydrates as the Departments of Agriculture and Health and Human Services weigh updates to national diet guidelines for 2025.

The scientific debate isn't easy to follow. But it sounds like a half-baked idea to Kam Quarles, chief executive of the National Potato Council, a potato-industry group. The dietary guidelines shape nutrition advice to Americans, as well as what foods are served in school cafeterias. Potatoes, according to Quarles, should be respected as a gateway vegetable. "Kids are far more likely to eat" dishes with other vegetables if potatoes are involved, he said.

Not all parents swallow that a trail of tubers leads to leafy greens. Some complained about a Peppa Pig animated cartoon that featured a potato preaching the nutritional value of vegetables. "By the power of vegetables, I am here," Super Potato said, soaring through the sky, singing, "Fruit and vegetables keep us alive. Always remember to eat your five." The U.K.'s National Health Service, for one, doesn't count spuds toward the U.K.'s recommended five portions of fruits and vegetables a day. "It's a giant spud singing it. You're, like, 'Really? A potato's one of your five a day?'" said Dan Greef, the owner of Deliciously Guilt Free, a sugar-free bakery in Cambridge, U.K. He spent years persuading his two children to eat vegetables. Then, he said, "a drawing of a potato tells you it's fine, and you don't listen to your dad...."

Nutrition researchers say the potato contains helpful nutrients, including potassium and vitamin C, but its health benefits are diminished when it is fried. Nearly half of all U.S. potatoes eaten as food go into frozen products, mostly french fries, the USDA found.
For comparison, the article points out that under U.S. dietary guidelines, "corn on the cob is a starchy vegetable, while cornmeal is a grain."

An anonymous reader quotes a report from STAT: The Food and Drug Administration on Friday approved the world's first medicine based on CRISPR gene-editing technology, a groundbreaking treatment for sickle cell disease that delivers a potential cure for people born with the chronic and life-shortening blood disorder. The new medicine, called Casgevy, is made by Vertex Pharmaceuticals and CRISPR Therapeutics. Its authorization is a scientific triumph for the technology that can efficiently and precisely repair DNA mutations -- ushering in a new era of genetic medicines for inherited diseases.

In a clinical trial, Casgevy was shown to eliminate recurrent episodes of debilitating pain caused by sickle cell, which afflicts approximately 100,000 people in the U.S., a vast majority of whom are Black. The therapy, whose scientific name is exa-cel, is described as a potential cure because the genetic fix enabled by CRISPR is designed to last a lifetime, although confirmation will require years of follow-up. The FDA decision comes three weeks after regulators in the U.K. were the first to clear the drug. Approval in the European Union is expected next year. The FDA is also expected to rule on exa-cel as a treatment for beta thalassemia, another inherited blood disorder, by March 30.

The FDA on Friday also approved another sickle cell treatment, a gene therapy from Bluebird Bio called Lyfgenia. Patients will now have the option of two cutting-edge therapies that provide potentially curative benefits. Scientists Emmanuelle Charpentier and Jennifer Doudna published their first CRISPR paper just over a decade ago. In 2020, the research won the pair a Nobel Prize. Reflecting on the approval of Casgevy, Charpentier told STAT via email that she was "excited and pleased" for what it means for patients and their families.

The Biden administration is threatening to cancel the patents of some costly medications to allow rivals to make their own more affordable versions. The Associated Press reports: Under a plan announced Thursday, the government would consider overriding the patent for high-priced drugs that have been developed with the help of taxpayer money and letting competitors make them in hopes of driving down the cost. In a 15-second video released to YouTube on Wednesday night, President Joe Biden promised the move would lower prices. "Today, we're taking a very important step toward ending price gouging so you don't have to pay more for the medicine you need," he said.

White House officials would not name drugs that might potentially be targeted. The government would consider seizing a patent if a drug is only available to a "narrow set of consumers," according to the proposal that will be open to public comment for 60 days. Drugmakers are almost certain to challenge the plan in court if it is enacted. [...] The White House also intends to focus more closely on private equity firms that purchase hospitals and health systems, then often whittle them down and sell quickly for a profit. The departments of Justice and Health and Human Services, and the Federal Trade Commission will work to share more data about health system ownership.

While only a minority of drugs on the market relied so heavily on taxpayer dollars, the threat of a government "march-in" on patents will make many pharmaceutical companies think twice, said Jing Luo, a professor of medicine at University of Pittsburgh. "If I was a drug company that was trying to license a product that had benefited heavily from taxpayer money, I'd be very careful about how to price that product," Luo said. "I wouldn't want anyone to take my product away from me."

An anonymous reader quotes a report from Motherboard: Researchers have identified previously unknown elements of whale vocalizations that may be analogous to human speech, a new study reports. Sperm whales are giants of the deep, with healthy adults having no known predators. Scientists studying their vocalizations have already picked out key elements of their communication, namely clicks, sequences of which are called codas. Now, researchers led by Gasper Beus from the University of California, Berkeley report the discovery that the acoustic properties of these clicks -- for example, pitch -- are "on many levels analogous to human vowels and dipthongs," which is when one vowel sound morphs into another such as in the word "coin." The researchers even identify two unique "coda vowels" that are "actively exchanged" in conversation between whales, which they term the a-vowel and i-vowel.

The researchers explain in their paper, published as a preprint online this week, that the first clue that so-called spectral properties could be meaningful for whale speech was provided by AI. Beus previously developed a deep learning model for human language called fiwGAN which "was trained to imitate sperm whale codas and embed information into these vocalizations." Not only did the AI predict elements of whale vocalizations already thought to be meaningful, such as clicks, but it also singled out acoustic properties. To follow up on the AI's tip, the researchers analyzed a dataset of 3948 sperm whale codas recorded with hydrophones placed directly on whales between 2014 and 2018. They only analyzed one channel from the hydrophones to control for underwater effects and whale movement, and removed click timing from their visualization to better isolate patterns in the acoustic properties themselves.

These visualizations vindicated the AI's prediction: The whales reliably exchanged codas with one or two formants -- frequency peaks in the sound wave -- below the 10kHz range. The researchers termed these codas "vowels," with single-formant codas being a-vowels and two-formant codas being i-vowels. "This is by analogy to human vowels which differ in their formant frequencies," the authors wrote. They also identified upward and downward frequency "trajectories" in these codas, which they considered analogous to dipthongs in human language. Considering that these coda vowel patterns were very distinct and not intermixed, plus the existence of dipthongs, the researchers argue that whales are controlling the frequency of their vocalizations.

Record-breaking land and sea temperatures, driven by climate breakdown, will probably cause "unprecedented mass coral bleaching and mortality" throughout 2024, according to a pioneering coral scientist. From a report: The impact of climate change on coral reefs has reached "uncharted territory," said Prof Ove Hoegh-Guldberg, from the University of Queensland, Australia, leading to concerns that we could be at a "tipping point."

The upper ocean is undergoing unmatched changes in conditions, ecosystems and communities that can be traced back to the 1980s, when mass coral bleaching first appeared. In a paper published in the journal Science, US and Australian researchers say that historical data on sea surface temperatures, over four decades, suggests that this year's extreme marine heatwaves may be a precursor to a mass bleaching and coral mortality event across the Indo-Pacific in 2024-25.

Mass coral bleaching happens when delicate corals become stressed due to factors including heat, causing them to lose their brown microbial algae, turning them white. At low stress levels, the algae can return to corals over a few months. But many Caribbean reef areas have recently experienced historically high sea temperatures that began one or two months earlier and lasted longer than usual. Crucially, 2023 is the first year of a potential pair of El Nino years, with the warmest average global surface sea temperature from February to July on record. Since 1997, every instance of these El Nino pairs has led to a global mass coral bleaching event.

Particle physicists should begin laying the groundwork for a revolutionary particle collider that could be built on American soil, a committee of scientists wrote in a draft report on the future of particle physics released on Thursday. From a report: The machine would collide tiny, point-like particles called muons, which resemble electrons but are more massive. Muons provide more bang for the buck than the protons used in the Large Hadron Collider at CERN, and would push the search for new forces and particles deeper than ever into the unknown. The siting of such a project, perhaps at the Fermi National Accelerator Laboratory in Illinois, would restore American particle physics to a position of pre-eminence that was ceded to Europe in 1993 when Congress canceled the giant Superconducting Super Collider. But it will take at least 10 years to demonstrate that the muon collider could work and how much it would cost.

"This is our muon shot," the committee, charged with outlining a vision for the next decade of American particle physics, said in a draft report titled "Exploring the Quantum Universe: Pathways to Innovation and Discovery in Particle Physics." The draft is being presented and discussed at a meeting in Washington, D.C., on Thursday and Friday, and at Fermilab next week. The draft report also highlighted a need to invest in next-generation experiments probing the nature of subatomic particles called neutrinos; the cosmic microwave background, relic radiation from the Big Bang; and dark matter, the gravitational glue holding galaxies together. The panel also recommended participating in a future facility in either Europe or Japan, dedicated to studying the Higgs boson, the discovery of which in 2012 was key for understanding how other particles get their mass.

"The size of the universe we now see as 14 billion light-years across was actually smaller than the size of a nucleus" early in cosmic time, said Hitoshi Murayama, a physicist at the University of California, Berkeley, who led the committee. "So our field is actually not just looking for the fundamental constituents, but getting a bigger picture of how the universe works as whole." The committee, formally known as the Particle Physics Project Prioritization Panel, or P5, was tasked by the U.S. Department of Energy and the National Science Foundation to lay out a road map for the future of the field. The three-year process began by soliciting input from the particle physics community at large, and the final report will serve as a recommendation for what national agencies should prioritize over the next decade.

In an exclusive interview with PetaPixel, astronaut Don Pettit reveals the changes that Nikon makes to its firmware especially for NASA. From the report: Galactic cosmic rays are high-energy particles that originate from outside the solar system that likely come from explosive events such as a supernova. They are bad news for cameras in space -- damaging the sensor and spoiling photos -- so Nikon made special firmware for NASA to limit the harm. Pettit tells PetaPixel that Nikon changed the in-camera noise reduction settings to battle the cosmic rays -- noise is unwanted texture and blur on photos.

Normal cameras have in-camera noise reduction for exposures equal to or longer than one second. This is because camera manufacturers don't think photographers need noise reduction for shorter exposures because there's no noise to reduce. But in space, that's not true. "Our cameras in space get sensor damage from galactic cosmic rays and after about six months we replace all the cameras but you still have cameras with significant cosmic ray damage," explains Pettit. "It shows up at fast shutter speeds, not just the slow ones. So we got Nikon to change the algorithm so that it can do in-camera noise reduction at shutter speeds of up to 500th of a second."

Pettit says Nikon's in-camera noise reduction "does wonders" for getting rid of the cosmic ray damage and that "trying to get rid of it after the fact is really difficult." That's not the only special firmware feature that Nikon makes for NASA; photographers who shoot enough photos know that the file naming system resets itself eventually which is no good for the space agency's astronauts. "The file naming system on a standard digital system will repeat every so often and we can't have two pictures with the same number," explains Pettit. "We'll take half a million pictures with the crew on orbit and so Nikon has changed the way the RAW files are numbered so that there will be no two with the same file number." The report notes that NASA started using Nikon film cameras in 1971, shortly after the Apollo era; "in part because Nikon is so good at making custom modifications that help the astronauts." Previously, the agency used boxy, black Hasselblad cameras.

Anna Demming reports via Scientific American: [A]lthough so far there's no way to unscramble an egg, in certain carefully controlled scenarios within relatively simple systems, researchers have managed to turn back time. The trick is to create a certain kind of reflection. First, imagine a regular spatial reflection, like one you see in a silver-backed glass mirror. Here reflection occurs because for a ray of light, silver is a very different transmission medium than air; the sudden change in optical properties causes the light to bounce back, like a Ping-Pong ball hitting a wall. Now imagine that instead of changing at particular points in space, the optical properties all along the ray's path change sharply at a specific moment in time. Rather than recoiling in space, the light would recoil in time, precisely retracing its tracks, like the Ping-Pong ball returning to the player who last hit it. This is a "time reflection." Time reflections have fascinated theorists for decades but have proved devilishly tricky to pull off in practice because rapidly and sufficiently changing a material's optical properties is no small task. Now, however, researchers at the City University of New York have demonstrated a breakthrough: the creation of light-based time reflections. To do so, physicist Andrea Alu and his colleagues devised a "metamaterial" with adjustable optical properties that they could tweak within fractions of a nanosecond to halve or double how quickly light passes through. Metamaterials have properties determined by their structures; many are composed of arrays of microscopic rods or rings that can be tuned to interact with and manipulate light in ways that no natural material can. Bringing their power to bear on time reflections, Alu says, revealed some surprises. "Now we are realizing that [time reflections] can be much richer than we thought because of the way that we implement them," he adds. [...]

The device Alu and his collaborators developed is essentially a waveguide that channels microwave-frequency light. A densely spaced array of switches along the waveguide connects it to capacitor circuits, which can dynamically add or remove material for the light to encounter. This can radically shift the waveguide's effective properties, such as how easily it allows light to pass through. "We are not changing the material; we are adding or subtracting material," Alu says. "That is why the process can be so fast." Time reflections come with a range of counterintuitive effects that have been theoretically predicted but never demonstrated with light. For instance, what is at the beginning of the original signal will be at the end of the reflected signal -- a situation akin to looking at yourself in a mirror and seeing the back of your head. In addition, whereas a standard reflection alters how light traverses space, a time reflection alters light's temporal components -- that is, its frequencies. As a result, in a time-reflected view, the back of your head is also a different color. Alu and his colleagues observed both of these effects in the team's device. Together they hold promise for fueling further advances in signal processing and communications -- two domains that are vital for the function of, say, your smartphone, which relies on effects such as shifting frequencies.

Just a few months after developing the device, Alu and his colleagues observed more surprising behavior when they tried creating a time reflection in that waveguide while shooting two beams of light at each other inside it. Normally colliding beams of light behave as waves, producing interference patterns where their overlapping peaks and troughs add up or cancel out like ripples on water (in "constructive" or "destructive" interference, respectively). But light can, in fact, act as a pointlike projectile, a photon, as well as a wavelike oscillating field -- that is, it has "wave-particle duality." Generally a particular scenario will distinctly elicit just one behavior or the other, however. For instance, colliding beams of light don't bounce off each other like billiard balls! But according to Alu and his team's experiments, when a time reflection occurs, it seems that they do. The researchers achieved this curious effect by controlling whether the colliding waves were interfering constructively or destructively -- whether they were adding or subtracting from each other -- when the time reflection occurred. By controlling the specific instant when the time reflection took place, the scientists demonstrated that the two waves bounce off each other with the same wave amplitudes that they started with, like colliding billiard balls. Alternatively they could end up with less energy, like recoiling spongy balls, or even gain energy, as would be the case for balls at either end of a stretched spring. "We can make these interactions energy-conserving, energy-supplying or energy-suppressing," Alu says, highlighting how time reflections could provide a new control knob for applications that involve energy conversion and pulse shaping, in which the shape of a wave is changed to optimize a pulse's signal.

The Extremely Large Telescope (ELT) under construction in Chile's Atacama Desert will be the world's biggest optical telescope when completed in 2028. With a giant 39.3-meter main mirror and advanced adaptive optics, the ELT will collect far more light and achieve much sharper images than any existing ground-based telescope, revolutionizing the study of exoplanets, black holes, dark matter, and the early universe. Economist adds: But when it comes to detecting the dimmest and most distant objects, there is no substitute for sheer light-gathering size. On that front the ELT looks like being the final word for the foreseeable future. A planned successor, the "Overwhelmingly Large Telescope," would have sported a 100-metre mirror. But it was shelved in the 2000s on grounds of complexity and cost. The Giant Magellan Telescope is currently being built several hundred kilometres south of the elt on land owned by the Carnegie Institution for Science, an American non-profit, and is due to see its first light some time in the 2030s. It will combine seven big mirrors into one giant one with an effective diameter of 25.4 metres. Even so, it will have only around a third the light-gathering capacity of the ELT.

A consortium of scientists from America, Canada, India and Japan, meanwhile, has been trying to build a mega-telescope on Hawaii. The Thirty Meter Telescope would, as its name suggests, be a giant -- though still smaller than the elt. But it is unclear when, or even if, it will be finished. Construction has been halted by arguments about Mauna Kea, the mountain on which it is to be built, which is seen as sacred by some. For the next several decades, it seems, anyone wanting access to the biggest telescope money can buy will have to make their way to northern Chile.