In 1992 John Conway raised a question about the patterns in his famous mathematical Game of Life: "Is there a Godlike still-life, one that can only have existed for all time (apart from things that don't interfere with it)?"

Conway closed his note by adding "Well, I'm going out to get a hot dog now..." And then, nearly 30 years later, a mathematical blog reports: Ilkka Törmä and Ville Salo, a pair of researchers at the University of Turku in Finland, have found a finite configuration in Conway's Game of Life such that, if it occurs within a universe at time T, it must have existed in that same position at time T-1 (and therefore, by induction, at time 0)...

The configuration was discovered by experimenting with finite patches of repeating 'agar' and using a SAT solver to check whether any of them possess this property.
The blogger also shares some other Game of Life-related news:

• David Raucci discovered the first oscillator of period 38. The remaining unsolved periods are 19, 34, and 41.
• Darren Li has connected Charity Engine to Catagolue, providing approximately 2000 CPU cores of continuous effort and searching slightly more than 10^12 random initial configurations per day.
• Nathaniel Johnston and Dave Greene have published a book on Conway's Game of Life, featuring both the theoretical aspects and engineering that's been accomplished in the half-century since its conception. Unfortunately it was released slightly too early to include the Törmä-Salo result or Raucci's period-38 oscillator.

Thanks to Slashdot reader joshuark for sharing the story.

"Scientists have estimated the number of 'small' black holes in the universe," reports Live Science. "And no surprise: It's a lot." Using a new method, outlined January 12 in The Astrophysical Journal, a team of astrophysicists has produced a fresh estimate for the number of stellar-mass black holes — those with masses 5 to 10 times that of the sun — in the universe.

And it's astonishing: 40,000,000,000,000,000,000, or 40 quintillion, stellar-mass black holes populate the observable universe, making up approximately 1% of all normal matter, according to the new estimate.

So how did the scientists arrive at that number? By tracking the evolution of stars in our universe they estimated how often the stars — either on their own, or paired into binary systems — would transform into black holes, said first author Alex Sicilia, an astrophysicist at the International School of Advanced Studies (SISSA) in Trieste, Italy. "This is one of the first, and one of the most robust, ab initio [ground up] computation[s] of the stellar black hole mass function across cosmic history," Sicilia said in a statement....

To arrive at their estimate, the astrophysicists modeled not just the lives, but the pre-lives of the universe's stars. Using known statistics of various galaxies, such as their sizes, the elements they contain, and the sizes of the gas clouds stars would form in, the team built a model of the universe that accurately reflected the different sizes of stars that would be made, and how often they would be created.... [T]he researchers designed a model that tracked the population and size distribution of stellar-mass black holes over time to give them their eye-watering number. Then, by comparing the estimate with data taken from gravitational waves, or ripples in space-time, formed by black hole and binary star mergers, the researchers confirmed that their model was in good agreement with the data.

Astrophysicists hope to use the new estimate to investigate some perplexing questions that arise from observations of the very early universe — for instance, how the early universe became so quickly populated by supermassive black holes — often with masses millions, or even billions, of times greater than the stellar-mass holes the researchers examined in this study — so soon after the Big Bang.

"Three studies released Friday offered more evidence that COVID-19 vaccines are standing up to the omicron variant, at least among people who received booster shots," reports the Associated Press: They are the first large U.S. studies to look at vaccine protection against omicron, health officials said. The papers echo previous research — including studies in Germany, South Africa and the U.K. — indicating available vaccines are less effective against omicron than earlier versions of the coronavirus, but also that boosters doses rev up virus-fighting antibodies to increase the chance of avoiding symptomatic infection.

The first study looked at hospitalizations and emergency room and urgent care center visits in 10 states, from August to this month. It found vaccine effectiveness was best after three doses of the Pfizer or Moderna vaccines in preventing COVID-19-associated emergency department and urgent care visits. Protection dropped from 94% during the delta wave to 82% during the omicron wave. Protection from just two doses was lower, especially if six months had passed since the second dose. Officials have stressed the goal of preventing not just infection but severe disease. On that count, some good news: A third dose was at least 90% effective at preventing hospitalizations for COVID-19, both during the delta and omicron periods, the study also found.

The second study focused on COVID-19 case and death rates in 25 states from the beginning of April through Christmas. People who were boosted had the highest protection against coronavirus infection, both during the time delta was dominant and also when omicron was taking over...

The Journal of the American Medical Association published the third study, also led by CDC researchers. It looked at people who tested positive for COVID-19 from Dec. 10 to Jan. 1 at more than 4,600 testing sites across the U.S. Three shots of the Pfizer and Moderna vaccines were about 67% effective against omicron-related symptomatic disease compared with unvaccinated people. Two doses, however, offered no significant protection against omicron when measured several months after completion of the original series, the researchers found.

MIT, Brigham, and Women's Hospital researchers are working to eliminate many of the headaches associated with treating diabetes. According to Engadget, "They're developing all-in-one devices that measure glucose, calculate the necessary insulin dose and inject you accordingly." From the report: The first device includes the blood-drawing lancet, glucose test strips and an insulin needle. Users would first take a photo of their meal using a smartphone app to estimate the food volume and carbohydrate levels. After that, they'd start the automated process of collecting blood, calculating glucose (again through the app) and delivering the appropriate amount of insulin. The second gadget would only need one needle jab -- it would build the glucose sensor into the insulin needle and inject the appropriate amount of insulin. You'd have to wait five to ten seconds, but you wouldn't have to stick yourself twice.

The technology is still some ways off. While the first device would use parts that were already FDA-approved, it hasn't been tested in humans. The second, meanwhile, uses a new sensor type that will likely require more work to be testable with humans. Scientists have filed patents for both devices and are hoping to work with companies on further development. There's a strong motivation to bring these devices to market, at least. People with diabetes would only need to use one device at meals, and with the hybrid sensor/needle might suffer less pain. That, in turn, could encourage consistent treatment that improves your overall wellbeing.

In 2021, there was an upsurge in peculiar sightings reported, thanks to people with smartphones or other video gear that captured these strange glimmers in the sky. In 2022, UAP will get more attention from both the scientific community and the federal government, experts told Space.com. From the report: One potential major development in 2022 will be UFO detection, according to Mark Rodeghier, scientific director of the Center for UFO Studies in Chicago. "The effort to detect, track and measure the UFO phenomenon in the field, in real time, has recently entered a new phase," Rodeghier told Space.com. "The technology has gotten better, software tools have improved and the current interest in UFOs has attracted new, qualified professionals. "While one can't predict how soon we will gain new, fundamental knowledge about UAP/UFOs, I believe that these efforts are very likely to succeed and set UFO research onto a new foundation of reliable, physical data," Rodeghier added. "And as a consequence, we will have even more evidence -- as if it was needed -- that the UFO phenomenon is real and can be studied scientifically."

One upcoming initiative, called the Galileo Project, will search for extraterrestrial equipment near Earth. It has two branches. The first aims to identify the nature of interstellar objects that do not resemble comets or asteroids -- like 'Oumuamua, the first known interstellar object to visit the solar system. The second branch targets UAP, similar to those of interest to the U.S. government. "The Galileo Project's data will be open to the public, and its scientific analysis will be transparent," said Harvard astronomer Avi Loeb, who is spearheading the project. "The related scientific findings would expand humanity's knowledge, with no attention to borders between nations." The Galileo research team includes more than 100 scientists who plan to assemble the project's first telescope system on the roof of the Harvard College Observatory in spring 2022. "The system will record continuous video and audio of the entire sky in the visible, infrared and radio bands, as well as track objects of interest," Loeb said. "Artificial intelligence algorithms will distinguish birds from drones, airplanes or something else. Once the first system will operate successfully, the Galileo Project will make copies of it and distribute them in many geographical locations."

Currently, there is a lack of coordination among organizations involved in UAP detection equipment, but that may change this year, said Robert Powell, an executive board member of the Scientific Coalition for UAP Studies (SCU) in Austin, Texas. "I believe that will improve as we go into 2022," he said. A number of SCU members are involved with the Galileo Project, and the organization has partnered with several groups, including UFODATA, the UFO Data Acquisition Project (UFODAP) and UAPx. "UFODAP already has a working model that has been sold into the marketplace and is reasonably priced in the $2,000 to $5,000 range, depending on the accessories desired," Powell told Space.com. "This system has already been used by a group known as UAPx to collect data. Our goal is to coordinate these activities in a way such that we use a system with standardized equipment set to collect data." But before that happens, Powell said, the groups need to plot out exactly what that equipment is trying to measure and verify that the system can achieve that goal.

A first-of-its-kind "green" Shell facility in Alberta is emitting more greenhouse gases than it's capturing, throwing into question whether taxpayers should be funding it, a new report has found. Motherboard reports: Shell's Quest carbon capture and storage facility in the Alberta tarsands captured 5 million tonnes of carbon dioxide at its hydrogen-producing plant in its Scotford complex between 2015 and 2019. But a new report from human rights organization Global Witness found the hydrogen plant emitted 7.5 million tons of greenhouse gases in the same timeframe -- including methane, which has 80 times the warming power of carbon during its first 20 years in the atmosphere, and accounts for about a quarter of man-made warming today. To put that in perspective, the "climate-forward" part of the Scotford plant alone has the same carbon footprint per year as 1.2 million fuel-powered cars, Global Witness said.

"We do think Shell is misleading the public in that sense and only giving us one side of the story," said Dominic Eagleton, who wrote the report. He said industry's been pushing for governments to subsidize the production of fossil hydrogen (hydrogen produced from natural gas) that's supplemented with carbon capture technology as a "climate-friendly" way forward, but the new report shows that's not the case. In an email, Shell said the facility was introduced to display the merits of carbon capture technology, but didn't directly respond to the allegation that its hydrogen component emitted 7.5 million tons of greenhouse gases.

After 17 years of relatively smooth sailing, NASA's Neil Gehrels Swift Observatory has entered safe mode after detecting a "possible failure" in one of the six reaction wheels used to change attitude. Engadget reports: While it's not clear exactly what (if anything) went wrong, NASA has halted direction-based scientific observations until it can either give the all-clear or continue operations with five wheels. This is the first potential reaction wheel problem since the Swift Observatory began operations in February 2005, NASA said. The rest of the vehicle is otherwise working properly.

The Swift Observatory has played an important role in astronomy over the past two decades. It was primarily built to detect gamma-ray bursts and detects roughly 70 per day. However, it has increasingly been used as a catch-all observer across multiple wavelengths, spotting solar flares and hard-to-find stars. NASA won't necessarily run into serious trouble if Swift has a lasting problem, but it would clearly benefit from keeping the spacecraft running as smoothly as possible.

nickwinlund77 shares a report from SciTechDaily: UNSW Sydney-led research paves the way for large silicon-based quantum processors for real-world manufacturing and application. Australian researchers have proven that near error-free quantum computing is possible, paving the way to build silicon-based quantum devices compatible with current semiconductor manufacturing technology. [...] [The researcher's] paper is one of three published today in Nature that independently confirm that robust, reliable quantum computing in silicon is now a reality. This breakthrough is featured on the front cover of the journal.

[Professor Andrea Morello of UNSW, who led the work] et al achieved 1-qubit operation fidelities up to 99.95 percent, and 2-qubit fidelity of 99.37 percent with a three-qubit system comprising an electron and two phosphorous atoms, introduced in silicon via ion implantation. A Delft team in the Netherlands led by Lieven Vandersypen achieved 99.87 percent 1-qubit and 99.65 percent 2-qubit fidelities using electron spins in quantum dots formed in a stack of silicon and silicon-germanium alloy (Si/SiGe). A RIKEN team in Japan led by Seigo Tarucha similarly achieved 99.84 percent 1-qubit and 99.51 percent 2-qubit fidelities in a two-electron system using Si/SiGe quantum dots.

The UNSW and Delft teams certified the performance of their quantum processors using a sophisticated method called gate set tomography, developed at Sandia National Laboratories in the U.S. and made openly available to the research community. Morello had previously demonstrated that he could preserve quantum information in silicon for 35 seconds, due to the extreme isolation of nuclear spins from their environment. But the trade-off was that isolating the qubits made it seemingly impossible for them to interact with each other, as necessary to perform actual computations. Today's paper describes how his team overcame this problem by using an electron encompassing two nuclei of phosphorus atoms. The three papers from the UNSW team, Delft team and RIKEN group in Tokyo can be found at their respective links.

An anonymous reader quotes a report from The Guardian: An initial CIA investigation into the mysterious set of symptoms known as Havana syndrome has found that it is unlikely to be the result of a worldwide campaign of attacks by a foreign power against US diplomats and spies. However, two dozen cases, including some of those originally afflicted in Havana in 2016, could not be explained and would be further studied for evidence of a possible attack, according to a senior CIA official who briefed the US press.

"While we have reached some significant interim findings, we are not done," the CIA director, Williams Burns, said in a statement. "We will continue the mission to investigate these incidents and provide access to world-class care for those who need it." Since the original outbreak of the symptoms, which include hearing strange sounds, dizziness, loss of balance, nausea and memory loss, more than 1,000 cases have been studied around the world. The interim findings of a CIA investigation have found that the majority of cases could probably be attributed to a pre-existing medical condition, or environmental factors, or stress, the senior official said. The defense department and an independent panel of experts are conducting their own investigations which have yet to publish reports. A Havana syndrome victims support group said in a statement: "The decision to release the report now and with this particular set of 'findings' seems a breach of faith, and an undermining of the intent of Congress and the president to stand with us and reach a government-wide consensus as to what is behind this," a Havana syndrome victims group said in a statement.

"This report was neither cleared nor coordinated through the interagency and must stand as the assessment of one agency [CIA] alone."

Elon Musk's brain implant company Neuralink is now hiring a clinical trial director, an indication that the company's longstanding goal of implanting chips in human brains is coming closer. Bloomberg: The trial director position would oversee the startup's long-promised human trials of its medical device, according to the listing. Neuralink's brain implant -- which Musk has said already allows monkeys to play video games with their thoughts alone -- is intended to help treat a variety of neurological disorders, such as paralysis. The job description for the position, based in Fremont, California, promises that the applicant will "work closely with some of the most innovative doctors and top engineers" as well as with "Neuralink's first Clinical Trial participants." It also indicates that the job will mean leading and building "the team responsible for enabling Neuralink's clinical research activities," as well as adhering to regulations. Last month, Musk told the Wall Street Journal that Neuralink hoped to implant its device in human brains sometime in 2022.

An anonymous reader quotes a report from The Guardian: Antimicrobial resistance poses a significant threat to humanity, health leaders have warned, as a study reveals it has become a leading cause of death worldwide and is killing about 3,500 people every day. More than 1.2 million -- and potentially millions more -- died in 2019 as a direct result of antibiotic-resistant bacterial infections, according to the most comprehensive estimate to date of the global impact of antimicrobial resistance (AMR). The stark analysis covering more than 200 countries and territories was published in the Lancet. It says AMR is killing more people than HIV/Aids or malaria. Many hundreds of thousands of deaths are occurring due to common, previously treatable infections, the study says, because bacteria that cause them have become resistant to treatment.

The new Global Research on Antimicrobial Resistance (Gram) report estimates deaths linked to 23 pathogens and 88 pathogen-drug combinations across 204 countries and territories in 2019. Statistical modeling was used to produce estimates of the impact of AMR in all locations -- including those with no data -- using more than 470m individual records obtained from systematic literature reviews, hospital systems, surveillance systems, and other data sources. The analysis shows AMR was directly responsible for an estimated 1.27 million deaths worldwide, and associated with an estimated 4.95 million deaths, in 2019. HIV/Aids and malaria have been estimated to have caused 860,000 and 640,000 deaths, respectively, in 2019. While AMR poses a threat to people of all ages, young children were found to be at particularly high risk, with one in five deaths attributable to AMR occurring in children under the age of five. Some of the actions policymakers can take, as mentioned in the report, include "optimizing the use of existing antibiotics, taking greater action to monitor and control infections, and providing more funding to develop new antibiotics and treatments."

A quick and pain-free scan of the human eyeball could one day help doctors identify "fast agers," who are at greater risk of early mortality. ScienceAlert reports: A machine learning model has now been taught to predict a person's years of life simply by looking at their retina, which is the tissue at the back of the eye. The algorithm is so accurate, it could predict the age of nearly 47,000 middle-aged and elderly adults in the United Kingdom within a bracket of 3.5 years. Just over a decade after these retinas were scanned, 1,871 individuals had died, and those who had older-looking retinas were more likely to fall in this group.

For instance, if the algorithm predicted a person's retina was a year older than their actual age, their risk of death from any cause in the next 11 years went up by 2 percent. At the same time, their risk of death from a cause other than cardiovascular disease or cancer went up by 3 percent. The findings are purely observational, which means we still don't know what is driving this relationship at a biological level. Nevertheless, the results support growing evidence that the retina is highly sensitive to the damages of aging. Because this visible tissue hosts both blood vessels and nerves, it could tell us important information about an individual's vascular and brain health. The study was published in the British Journal of Ophthalmology.

Over the past 450 million years, life on Earth has been devastated by at least five mass extinctions, which are typically defined as catastrophes that wipe out more than 75 percent of species in a short amount of time. Many scientists have proposed that we are entering a Sixth Mass Extinction, this time driven by human activity, though debates still rage over the validity and consequences of this claim. From a report: Now, a team led by Robert Cowie, research professor at the University of Hawaii's Pacific Biosciences Research Center, argues that "the Sixth Mass Extinction has begun on land and in freshwater seems increasingly likely," according to a recent article published in Biological Reviews. "We consider that the Sixth Mass Extinction has probably started and present arguments to counter those who would deny this," said the team, which also included biologists Philippe Bouchet and Benoît Fontaine of the Museum National d'Histoire Naturelle in Paris, France, in the article.

"Denying it is simply flying in the face of the mountain of data that is rapidly accumulating, and there is no longer room for skepticism, wondering whether it really is happening," added the authors. Cowie and his colleagues refer to a multitude of studies cataloging the extinction of species across clades, but the article is primarily built around their research into mollusks, an invertebrate family that includes snails, clams, and slugs. This focus counteracts the disproportionate attention that vertebrates, such as birds and mammals, receive in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, among other conservation efforts.

An anonymous reader shares a report: [...] Together, these furry duplicates are normalizing the world of animal cloning -- and they could be ushering in an era of petfluencer immortality. "Someone could clone their pet and replace the original. The world doesn't have to know. They may never know," says Melain Rodriguez, client service manager at ViaGen, which is behind the cloning of all the animals mentioned in this article. "Especially if it's one that looks exactly the same and they can just continue with that pet." (Rodriguez notes that the cloned pets aren't "reincarnations" and will have different personalities than their predecessors.)

The process, however, is complicated and expensive. The price tag for cloning a pet ranges anywhere from $35,000 to $50,000, depending on the animal. "It's very similar to IVF," explains Rodriguez. "The eggs and the embryos are created in a dish, and then they're transferred into the surrogate." She adds that customers often stomach the cost due to the emotions involved: "If you've ever had a wonderful pet that you love so much, it's so hard to lose them. A lot of our clients are in that situation."

Bulletin of the Atomic Scientists to unveil its measure of how close human civilisation is to the edge of extinction. From a report: On 24 October 1962, an American nuclear chemist, Harrison Brown, started to pen a guest editorial for the Bulletin of the Atomic Scientists just as the Cuban missile crisis reached its climax. "I am writing on a plane en route from Los Angeles to Washington and for all I know this editorial ... may never be published," Brown said. "Never in history have people and nations been so close to death and destruction on such a vast scale. Midnight is upon us." With this dire warning, he was referring to the Doomsday Clock, which has been the Bulletin's iconic motif since it was founded 75 years ago by Albert Einstein and some of the University of Chicago scientists from the Manhattan Project. Their work had contributed to making the atomic bomb, but many of them had been outraged when the US used it against Japanese cities.

The image of the clock ticking away to midnight was intended to convey the sense of urgent peril, which Brown felt so viscerally on that 1962 flight to Washington. "He thought the world could end while he was on that flight," said Rachel Bronson, the Bulletin's current president. On Thursday, the Doomsday Clock will be unveiled for the 75th time, and we will find out what way the Bulletin's panel of scientists and security experts will move the minute hand. For the past two years it has been stuck at 100 seconds to midnight. With Russia poised to attack Ukraine, it is hard to imagine the clock being set back, and that means that the experts assess we are in greater danger now than ever. The closest the clock came at the height of the cold war was two minutes to midnight in 1953 after the first detonation of a thermonuclear warhead, a hydrogen bomb. By the time of the Cuban missile crisis, the hands were at seven minutes to, but despite Brown's apocalyptic editorial, the Bulletin decided not to move them forward because the shock of near catastrophe had given Washington and Moscow fresh incentive to work towards risk reduction and arms control.

An anonymous reader shares an excerpt from a report via MIT Technology Review: Biologists at several startups are applying the latest advances in genetic engineering to the age-old problem of baldness, creating new hair-forming cells that could restore a person's ability to grow hair. Some researchers tell MIT Technology Review they are using the techniques to grow human hair cells in their labs and even on animals. A startup called dNovo sent us a photograph of a mouse sprouting a dense clump of human hair -- the result of a transplant of what the company says are human hair stem cells. The company's founder is Ernesto Lujan, a Stanford University -- trained biologist. He says his company can produce the components of hair follicles by genetically "reprogramming" ordinary cells, like blood or fat cells. More work needs to be done, but Lujan is hopeful that the technology could eventually treat "the underlying cause of hair loss."

According to NASA researchers, the power of a massive volcanic eruption that took place on Saturday near the island nation of Tonga was equivalent to around 10 megatons of TNT. "That means the explosive force was more than 500 times as powerful as the nuclear bomb dropped on Hiroshima, Japan, at the end of World War II," reports NPR. From the report: The blast was heard as far away as Alaska and was probably one of the loudest events to occur on Earth in over a century, according to Michael Poland, a geophysicist with the U.S. Geological Survey. "This might be the loudest eruption since [the eruption of the Indonesian volcano] Krakatau in 1883," Poland says. That massive 19th-century eruption killed thousands and released so much ash that it cast much of the region into darkness.

But for all its explosive force, the eruption itself was actually relatively small, according to Poland, of the U.S. Geological Survey. Unlike the 1991 eruption of Mount Pinatubo, which spewed ash and smoke for hours, the events at Hunga Tonga-Hunga Ha'apai lasted less than 60 minutes. He does not expect that the eruption will cause any short-term changes to Earth's climate, the way other large eruptions have in the past. In fact, Poland says, the real mystery is how such a relatively small eruption could create such a big bang and tsunami.

The cocktail of chemical pollution that pervades the planet now threatens the stability of global ecosystems upon which humanity depends, scientists have said. The Guardian reports: Plastics are of particularly high concern, they said, along with 350,000 synthetic chemicals including pesticides, industrial compounds and antibiotics. Plastic pollution is now found from the summit of Mount Everest to the deepest oceans, and some toxic chemicals, such as PCBs, are long-lasting and widespread. The study concludes that chemical pollution has crossed a "planetary boundary", the point at which human-made changes to the Earth push it outside the stable environment of the last 10,000 years.

Determining whether chemical pollution has crossed a planetary boundary is complex because there is no pre-human baseline, unlike with the climate crisis and the pre-industrial level of CO2 in the atmosphere. There are also a huge number of chemical compounds registered for use -- about 350,000 -- and only a tiny fraction of these have been assessed for safety. So the research used a combination of measurements to assess the situation. These included the rate of production of chemicals, which is rising rapidly, and their release into the environment, which is happening much faster than the ability of authorities to track or investigate the impacts. The well-known negative effects of some chemicals, from the extraction of fossil fuels to produce them to their leaking into the environment, were also part of the assessment. The scientists acknowledged the data was limited in many areas, but said the weight of evidence pointed to a breach of the planetary boundary. [...] The researchers said stronger regulation was needed and in the future a fixed cap on chemical production and release, in the same way carbon targets aim to end greenhouse gas emissions. Their study was published in the journal Environmental Science & Technology. "The rise of the chemical burden in the environment is diffuse and insidious," said Prof Sir Ian Boyd at the University of St Andrews. "Even if the toxic effects of individual chemicals can be hard to detect, this does not mean that the aggregate effect is likely to be insignificant."

"Regulation is not designed to detect or understand these effects. We are relatively blind to what is going on as a result. In this situation, where we have a low level of scientific certainty about effects, there is a need for a much more precautionary approach to new chemicals and to the amount being emitted to the environment."

Runaway success and underfunding have led to growing pains for the preprint server. From a report: What started in 1989 as an e-mail list for a few dozen string theorists has now grown to a collection of more than two million papers -- and the central hub for physicists, astronomers, computer scientists, mathematicians and other researchers. On January 3 the preprint server arXiv.org crossed the milestone with a numerical analysis paper entitled "Affine Iterations and Wrapping Effect: Various Approaches." (The Library of Alexandria, for comparison, is believed to have contained no more than hundreds of thousands of manuscripts.) "We're a way for authors to communicate their research results quickly and freely," says Steinn Sigurdsson, a professor of astrophysics at Pennsylvania State University and arXiv's scientific director. Unlike traditional scientific journals, arXiv (pronounced "archive" because the "X" represents the Greek letter chi) allows scientists to share research before it has been peer-reviewed.

When submitting to traditional journals, authors frequently wait half a year or more to publish; papers typically appear on arXiv within a day. Authors often submit manuscripts to arXiv and then subsequently publish them in a peer-reviewed journal, but increasingly, papers are released on arXiv alone. Beyond traditional manuscripts, arXiv also contains white papers, historical overviews and even cheeky April Fools' Day papers. "It's like the backbone for our field," says Alex Kohls, head of the Scientific Information Service at CERN, the world's premier organization for particle physics research, located near Geneva.

"It's not only a tool for physicists and computer scientists -- it has had an impact on the overall scholarly communication process." For instance, arXiv-inspired preprint servers in the life sciences, such as bioRxiv and medRxiv, have proved invaluable for speeding up biomedical research during the coronavirus pandemic. Growth has been explosive. In 2008, 17 years after it went online, arXiv hit 500,000 papers. By late 2014 that total had doubled to one million. Seven years later arXiv has doubled its library again but continues to grapple with its role: Is it closer to a selective academic journal or more like an online warehouse that indiscriminately collects papers? Amid this confusion, some researchers are concerned about arXiv's moderation policies, which they say lack transparency and have led to papers being unfairly rejected or misclassified. At the same time, arXiv is struggling to improve the diversity of its moderators, who are predominantly men based at U.S. institutions.

A team of astronomers has used archival images from a survey telescope to look for Starlink tracks over the past two years. Over that time, the number of images affected rose by a factor of 35, and the researchers estimate that by the time the planned Starlink constellation is complete, pretty much every image from their hardware will have at least one track in it. Ars Technica reports: SpaceX's Starlink Internet service will require a dense constellation of satellites to provide consistent, low-latency connectivity. The system already has over 1,500 satellites in orbit and has received approval to operate 12,000 of them. And that has astronomers worried. Although SpaceX has taken steps to reduce the impact of its hardware, there's no way to completely eliminate the tracks the satellites leave across ground-based observations. [...] In response to complaints from the astronomy community, SpaceX put visors on later generations of Starlink satellites. The research team was able to compare the visibility of these different generations and found that the visors worked -- satellites with visors dropped in brightness by a factor of roughly 4.6 (the precise number depended upon the wavelength). The visibility, however, was still higher than the target set at a workshop that was meant to address this issue.

Because these tracks are small and software already identifies and handles them, they don't have much of an effect on observations. The researchers estimate that, at present, there's only a 0.04 percent chance that a rare event will be missed because it coincides with a track. But because the problem is most acute in twilight observations, it's more likely to impact searches for objects within the Solar System. This would include comets and asteroids -- including asteroids that originated around other stars. But again, the problem is likely to get worse. SpaceX already has approval to increase the number of Starlink satellites to well over 10,000; the authors estimate that at 10,000, every image at twilight will likely contain a Starlink track. SpaceX has indicated it would eventually like to boost the numbers to over 40,000 satellites, at which point all twilight images are likely to have four tracks.

And SpaceX isn't the only company planning on this sort of satellite service. If all the companies involved follow through on their plans, low Earth orbit could see as many as 100,000 of these satellites. Overall, the picture is mixed. The ZTF's main mission -- to pick out rare events caused by distant, energetic phenomena -- is largely unaffected by the growing number of satellite tracks. And because the percentage of events is currently small, tripling the number of satellites won't have a dramatic impact on observations. But a secondary science mission is already seeing a lot of light contamination, and matters are only going to get worse. The findings have been published in the journal Astrophysical Journal Letters.