Astronomers have spotted a galaxy they believe is made of 99.9% dark matter, reports CNN — and it's so faint, it's almost invisible: CDG-2, which is about 300 million light-years from Earth, appears to be so rich in dark matter that it could belong to a hypothesized subset of low surface brightness galaxies called "dark galaxies," which are believed to contain few or no stars.... [Post-doctoral astrophysics/statistics fellow Dayi Li at the University of Toronto was lead author on a study about the discovery, and tells CNN] There is no strict definition of dark galaxies... but their existence is predicted by dark matter theories and cosmological simulations. "Where exactly do we draw the line in terms of how many stars they should have is still ambiguous, because not everything in astronomy is as clear-cut as we like," he said. "To be technically correct, CDG-2 is an almost-dark galaxy. But the importance of CDG-2 is that it nudges us much closer to getting to that truly dark regime, while previously we did not think a galaxy this faint could exist."

To observe CDG-2, the researchers used data from three telescopes — Hubble, the European Space Agency's Euclid space observatory and the Subaru Telescope in Hawaii — along with a novel approach that involved looking for objects called globular clusters. "These are very tight, spherical groupings of very olds stars, basically the relics of the first generation of star formation," Li said. Globular clusters are bright even if the surrounding galaxy is not, and previous observations have shown a relationship between them and the presence of dark matter in a galaxy, Li added. Because CDG-2 appears to have very few stars, there must be something else providing the mass that the clusters need to hold themselves together. Li and his colleagues assume that the source of the mass is dark matter.

The researchers found a set of four globular clusters in the Perseus Cluster, a group of thousands of galaxies immersed in a cloud of gas and one of the most massive objects in the universe. Further observations revealed a glow or halo around the globular clusters, suggesting the presence of a galaxy... Astronomers believe, Li explained, that after the formation of the clusters early in the galaxy's existence, larger surrounding galaxies stripped it of the hydrogen gas required to make more individual stars like our sun. "The material that this galaxy needed to continue to form stars was no longer there, so it was left with basically just a dark matter halo and the four globular clusters." The process, he added, would leave behind a skeleton or ghost of "a galaxy that pretty much just failed." As a result of this formation mechanism, the galaxy only has 0.005% of the brightness of our own galaxy, Li said...

Studying potential dark galaxies is important because they provide nearly pristine views of the behavior of dark matter, according to Neal Dalal, a researcher at the Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, who was not involved with the study.
Robert Minchin, an astronomer at New Mexico's National Radio Astronomy Observatory, told CNN that "it seems likely that other very dark galaxies will be found by this method in the future."

Ancient Slashdot reader alanw shares a report from the European Space Agency (ESA): Last year, an approximately 60 meter near-Earth object captured global attention. For a brief period, asteroid 2024 YR4 became the most dangerous asteroid discovered in the last 20 years. While an Earth impact was soon ruled out, the asteroid faded from view with a lingering 4% chance of striking the Moon on 22 December 2032. Now, that risk has been eliminated. Astronomers have confirmed that 2024 YR4 will not impact the Moon using new observations made by the Near-Infrared Camera (NIRCam) on the NASA/ESA/CSA James Webb Space Telescope. Instead, it will safely pass the Moon at a distance of more than 20 000 km.

An anonymous reader The Guardian: Humanity is heating the planet faster than ever before, a study has found. Climate breakdown is occurring more rapidly with the heating rate almost doubling, according to research that excludes the effect of natural factors behind the latest scorching temperatures. It found global heating accelerated from a steady rate of less than 0.2C per decade between 1970 and 2015 to about 0.35C per decade over the past 10 years. The rate is higher than scientists have seen since they started systematically taking the Earth's temperature in 1880.

"If the warming rate of the past 10 years continues, it would lead to a long-term exceedance of the 1.5C (2.7F) limit of the Paris agreement before 2030," said Stefan Rahmstorf, a scientist at the Potsdam Institute for Climate Impact Research and co-author of the study. [...] The researchers applied a noise-reduction method to filter out the estimated effect of nonhuman factors in five major datasets that scientists have compiled to gauge the Earth's temperature. In each of them, they found an acceleration in global heating emerged in 2013 or 2014. The findings have been published in the journal Geophysical Research Letters.

A recently-revised Senate authorization bill (PDF), co-sponsored by Senate Commerce Committee Chair Ted Cruz, would extend the International Space Station's lifespan from 2030 to 2032 while pushing NASA to accelerate plans for commercial space stations to replace it. Ars Technica's Eric Berger reports: Regarding NASA's support for the development of commercial space stations, the bill mandates the following, within specified periods, of passage of the law:

- Within 60 days, publicly release the requirements for commercial space stations in low-Earth orbit
- Within 90 days, release the final "request for proposals" to solicit industry responses
- Within 180 days, enter into contracts with "two or more" commercial providers for such stations

Cruz is trying to inject urgency into NASA as several private companies -- including Axiom Space, Blue Origin, Vast, and Voyager -- are finalizing designs for space stations. All have expressed a desire for clarity from NASA on how long the space agency would like its astronauts to stay on board, the types of scientific equipment needed, and much more. These are known as "requirements" in NASA parlance.

[...] Cruz and other senators on the committee appear to share those concerns, as their legislation extends the International Space Station's lifespan from 2030 to 2032 (an extension must still be approved by international partners, including Russia). Moreover, the authorization bill states, "The Administrator shall not initiate the de-orbit of the ISS until the date on which a commercial low-Earth orbit destination has reached an initial operational capability." With this legislation, the U.S. Senate is making clear that it views a permanent human presence in low-Earth orbit as a high priority. This version of the authorization legislation must still be passed by the full Senate and work its way through the House of Representatives.

Dustin Destree shares a report from Phys.org: Although plastic particles in the air are increasingly coming into focus, knowledge about their distribution and effects is still limited. Chemical analyses from Leipzig now provide details from Germany for the first time: Around 4% of the particulate matter consists of plastic. Around two-thirds of this comes from tire abrasion. Extrapolated, this means that people in a city like Leipzig inhale approximately 2.1 micrograms of plastic per day through the air, which increases the risk of death from cardiovascular disease by 9% and from lung cancer by 13%. These findings underscore the need to take global action against plastic pollution and to examine air quality and health at the regional level, write researchers from the Leibniz Institute for Tropospheric Research (TROPOS) and Carl von Ossietzky University of Oldenburg in the journal Communications Earth & Environment. "With around two-thirds of microplastics coming from tire abrasion, this shows that action is needed and that the fine dust problem cannot be solved by switching to electric mobility alone. To protect health, it would be important to also take tire abrasion into account when regulating air quality and to set limits for microplastics in the air," demands Prof. Hartmut Herrmann from TROPOS, who led the study.

The study has been published in the journal Communications Earth & Environment.

In a library in Florence, Italy, historian Ivan Malara noticed handwritten notes on a book printed in the 1500s — and recognized the handwriting as Galileo's. The finding "promises new insights into one of the most famous ideological transitions in the history of science," writes Science magazine — since the book Galileo annotated was a reprint of Ptolemy's second-century work arguing that the earth was the center of the universe. Galileo's notes, perhaps written around 1590, or roughly 2 decades before his groundbreaking telescope observations of the Moon and Jupiter, reveal someone who both revered and critically dissected Ptolemy's work. And they imply, Malara argues, that Galileo ultimately broke with Ptolemy's cosmos because his mastery of the traditional paradigm's reasoning convinced him that a heliocentric [sun-centered] system would better fulfill Ptolemy's own mathematical logic.

A start-up called Reflect Orbital "proposes to use large, mirrored satellites to redirect sunlight to Earth at night," reports the Washington Post, "with plans to bathe solar farms, industrial sites and even entire cities in light that could, if desired, reach the intensity of daylight...."

Slashdot noted their idea in 2022 — but Reflect Orbital now expects to launch its first satellite in April, according to the article. "But its grand vision is largely 'aspirational,' as its young founder, Ben Nowack, told me..." Reflect Orbital's Nowack describes a scene right out of sci-fi: An extremely bright star appears on the northern horizon and makes its way across the sky, illuminating a 5-kilometer circle on Earth, then setting on the southern horizon about five minutes later, just as another such "star" appears in the north. To make the night even brighter, a customer could make 10 "stars" appear at once in the north by ordering them on an app. Two such artificial stars are in development in Reflect Orbital's factory. Nowack showed them to me on a Zoom call. The first to launch is 50 feet across, but he plans later to build them three times that size. If all goes according to plan, he'll have 50,000 of them circling the Earth in 2035 at an altitude of around 400 miles.

Nowack plans to start selling the service "in mostly developing nations or places that don't have streetlights yet." Eventually, he thinks, he can illuminate major cities, turn solar fields and farms into round-the-clock operations for any business or municipality that pays for it. He likened his technology to the invention of crop irrigation thousands of years ago. "I see this as much the same thing," he said, arguing that people would no longer have to "wait for the sun to shine."
The article adds that Elon Musk's SpaceX "wants to launch as many as a million satellites to serve as orbiting data centers — 70 times the number of satellites now in orbit." (America's satellite-regulation Federal Communications Commission grants a "categorical exclusion" from environmental review to satellites on the grounds that their operations "normally do not have significant effects on the human environment.")

The public comment periods for the two proposals close on March 6 and March 9.

South Korea has reversed a two-decade policy and approved the export of high-precision map data, paving the way for a fully functional Google Maps in the country. Reuters reports: The approval was made "on the condition that strict security requirements are met," the Ministry of Land, Infrastructure and Transport said in a statement. Those conditions include blurring military and other sensitive security-related facilities, as well as restricting longitude and latitude coordinates for South Korean territory on products such as Google Maps and Google Earth, it said.

The decision is expected to hurt Naver and Kakao -- local internet giants which currently dominate the country's market for digital map services. But it will appease Washington, which has urged Seoul to tackle what it says is discrimination against U.S. tech companies. South Korea, still technically at war with North Korea, had shot down Google's previous bids in 2007 and 2016 to be allowed to export the data, citing the risks that information about sensitive military and security facilities could be exposed. "Google can now come in, slash usage fees, and take the market," said Choi Jin-mu, a geography professor at Kyung Hee University. "If Naver and Kakao are weakened or pushed out and Google later raises prices, that becomes a monopoly. Then, even companies that rely on map services -- logistics firms, for example -- become dependent, and in the long run, even government GIS (geographic information) systems could end up dependent on Google or Apple. That's the biggest concern."

sciencehabit quotes a report from Science Magazine: For decades, planetary scientists have pored over a mystery hidden within the Moon rocks retrieved by Apollo astronauts in the 1960s and '70s. Minerals in the rocks record the imprint of a magnetic field, nearly as powerful as Earth's, that existed more than 3.5 billion years ago and seemed to persist for millions of years. But generating a magnetic field requires a dynamo -- a churning, molten core -- and most researchers believed the Moon's tiny core would have long since cooled off, 1 billion years after it formed. Corroborating that picture are other ancient Moon rocks of about the same age that suggest the field was weak -- leaving planetary scientists baffled.

Now, researchers are proposing a new way to solve the puzzle. A paper published today in Nature Geoscience theorizes that between 3.5 billion and 4 billion years ago, blobs of titanium-rich magma melted episodically just above the core, rising in plumes that drove volcanic eruptions on the surface. By intermittently stirring up the Moon's core, these bouts of melting would have caused the Moon's magnetic field to flicker on in short, powerful bursts. The paper "links a few different concepts that people were thinking about separately, but hadn't actually brought together," says Sonia Tikoo, a planetary geophysicist at Stanford University who was not involved in the study.

Longtime Slashdot reader ArchieBunker shares a report from NBC News: NASA revealed that astronaut Mike Fincke was the crew member who suffered a medical incident at the International Space Station in January, which prompted the agency to carry out the first evacuation due to a medical issue in the space station's 25-year history. The rare decision to cut a mission short and bring Fincke and three other crew members home early made for a dramatic week in space early this year.

In a statement released by NASA "at the request of Fincke," the veteran astronaut said he experienced a medical event on Jan. 7 "that required immediate attention" from his space station crew members. "Thanks to their quick response and the guidance of our NASA flight surgeons, my status quickly stabilized," Fincke, 58, said in the statement. [...] In his statement, Fincke thanked his Crew-11 colleagues, along with NASA astronaut Chris Williams and Russian cosmonauts Sergey Kud-Sverchkov and Sergei Mikaev, who were also aboard the space station at the time and are still in space. Fincke also thanked the teams at NASA, SpaceX and the medical professionals at Scripps Memorial Hospital La Jolla. "Their professionalism and dedication ensured a positive outcome," he said.

Fincke ended his statement by saying he is "doing very well" and still actively involved with standard post-flight reconditioning at NASA's Johnson Space Center in Houston. "Spaceflight is an incredible privilege, and sometimes it reminds us just how human we are," he said. "Thank you for all your support."

Cord Cutters News reports: In a move that has delighted fans of classic science fiction, Warner Bros. Discovery has begun uploading full episodes of the iconic series Babylon 5 to YouTube, providing free access to the show just as it departs from the ad-supported streaming platform Tubi... Viewers noticed notifications on Tubi indicating that all five seasons would no longer be available after February 10, 2026, effectively removing one of the most accessible free streaming options for the space opera. With this shift, Warner Bros. Discovery appears to be steering the property toward its own digital ecosystem, leveraging YouTube's vast audience to reintroduce the show to both longtime enthusiasts and a new generation.

The uploads started with the pilot episode, "The Gathering," which serves as the entry point to the series' intricate universe. This was followed by subsequent episodes such as "Midnight on the Firing Line" and "Soul Hunter," released in sequence to build narrative momentum. [Though episodes 2 and 3 are mis-labeled as #3 and #4...] The strategy involves posting one episode each week, allowing audiences to experience the story at a paced rhythm that mirrors the original broadcast schedule...

For Warner Bros. Discovery, this initiative could signal plans to expand the franchise's visibility, especially amid ongoing interest in reboots and spin-offs that have been rumored in recent years.
Babylon 5 creator J. Michael Straczynski answered questions from Slashdot's readers in 2014.

Long-time Slashdot reader sandbagger offers this summary of the show "for those not in the know... In the mid-23rd century, the Earth Alliance space station Babylon Five, located in neutral territory, is a major focal point for political intrigue, racial tensions, and a major war as Earth descends into fascism and cuts off relations with its allies."

"Global temperatures have been rising for decades," reports the Washington Post. "But many scientists say it's now happening faster than ever before." According to a Washington Post analysis, the fastest warming rate on record occurred in the last 30 years. The Post used a dataset from NASA to analyze global average surface temperatures from 1880 to 2025. "We're not continuing on the same path we had before," said Robert Rohde, chief scientist at Berkeley Earth. "Something has changed...." Temperatures over the past decade have increased by close to 0.27 degrees C per decade — about a 42 percent increase...

For decades, a portion of the warming unleashed by greenhouse gas emissions was "masked" by sulfate aerosols. These tiny particles cause heart and lung disease when people inhale polluted air, but they also deflect the sun's rays. Over the entire planet, those aerosols can create a significant cooling effect — scientists estimate that they have canceled out about half a degree Celsius of warming so far. But beginning about two decades ago, countries began cracking down on aerosol pollution, particularly sulfate aerosols. Countries also began shifting from coal and oil to wind and solar power. As a result, global sulfur dioxide emissions have fallen about 40 percent since the mid-2000s; China's emissions have fallen even more. That effect has been compounded in recent years by a new international regulation that slashed sulfur emissions from ships by about 85 percent.

That explains part of why warming has kicked up a bit. But some researchers say that the last few years of record heat can't be explained by aerosols and natural variability alone. In a paper published in the journal Science in late 2024, researchers argued that about 0.2 degrees C of 2023's record heat — or about 13 percent — couldn't be explained by aerosols and other factors. Instead, they found that the planet's low-lying cloud cover had decreased — and because low-lying clouds tend to reflect the sun's rays, that decrease warmed the planet... That shift in cloud cover could also be partly related to aerosols, since clouds tend to form around particles in the atmosphere. But some researchers also say it could be a feedback loop from warming temperatures. If temperatures warm, it can be harder for low-lying clouds to form.

If most of the current record warmth is due to changing amounts of aerosol pollution, the acceleration would stop once aerosol pollutants reach zero — and the planet would return to its previous, slower rate of warming. But if it's due to a cloud feedback loop, the acceleration is likely to continue — and bring with it worsening heat waves, storms and droughts.
"Scientists thought they understood global warming," reads the Post's original headline. "Then the past three years happened."

Just last month Nuuk, Greenland saw temperatures over 20 degrees Fahrenheit above average, their article points out. And "Parts of Australia, meanwhile, have seen temperatures push past 120 degrees Fahrenheit amid a record heat wave..."

The world is closer than thought to a "point of no return" after which runaway global heating cannot be stopped, scientists have said. From a report: Continued global heating could trigger climate tipping points, leading to a cascade of further tipping points and feedback loops, they said. This would lock the world into a new and hellish "hothouse Earth" climate far worse than the 2-3C temperature rise the world is on track to reach.

The climate would also be very different to the benign conditions of the past 11,000 years, during which the whole of human civilisation developed. At just 1.3C of global heating in recent years, extreme weather is already taking lives and destroying livelihoods across the globe. At 3-4C, "the economy and society will cease to function as we know it," scientists said last week, but a hothouse Earth would be even more fiery. The public and politicians were largely unaware of the risk of passing the point of no return, the researchers said.

The group said they were issuing their warning because while rapid and immediate cuts to fossil fuel burning were challenging, reversing course was likely to be impossible once on the path to a hothouse Earth, even if emissions were eventually slashed. It was difficult to predict when climate tipping points would be triggered, making precaution vital, said Dr Christopher Wolf, a scientist at Terrestrial Ecosystems Research Associates in the US. Wolf is a member of a study team that includes Prof Johan Rockstrom at the Potsdam Institute for Climate Impact Research in Germany and Prof Hans Joachim Schellnhuber at the International Institute for Applied Systems Analysis in Austria.

Last Sunday, Bitcoin had dropped 13% in three days, to $76,790.

By Thursday it had dropped another 21%, to $60,062.

This morning it's at $69,549 — up from Thursday, down from Sunday, but 44% lower than its all-time high in October of $123,742. In short, Bitcoin "is down almost 30% this week alone," reports CNBC: "This steady selling in our view signals that traditional investors are losing interest, and overall pessimism about crypto is growing," Deutsche Bank analyst Marion Laboure said Wednesday in a note to clients. Growing investor caution comes as many of the sensationalized claims about bitcoin have failed to materialize. The token has largely traded in the same direction as other risk-on assets, such as stocks... and its adoption as a form of payment for goods and services has been minimal... While many in the crypto market have previously credited large institutional investors with supporting the price of bitcoin, now it is those same participants who appear to be selling. "Institutional demand has reversed materially," CryptoQuant said in a report on Wednesday.
But not everyone accepts that answer, the Wall Street Journal reported Saturday. "The worst part for some of crypto's permabulls is that they aren't sure what exactly caused the crash": The selloff left many of the market's luminaries — those so well-known that they go simply as "Pomp" and "Novo" and "Mooch" — searching for answers... Ether dropped 24% to $2,052, off 59% from its own high of last year. Both tokens staged furious rallies Friday, but the week remained a historically bad one for crypto. And few seem to know what went wrong. Market theories for the selloff ranged from investors' pivot toward the prediction markets and other risky bets, to widespread profit-taking after a blistering bull run. "There was no smoking gun," said Michael Novogratz, who runs Galaxy Digital, a crypto merchant-banking and trading firm...

"If you ask five experts, you'll get five explanations," said Anthony Scaramucci, who served for 11 days as communications director during Trump's first term and is among the best-known crypto bulls at his firm, SkyBridge Capital.
"No, but seriously: What's going on with bitcoin?" reads the headline at CNN, with a story that begins "Bitcoin is acting weird... " Crypto is notoriously volatile, and it's gone through numerous crashes that are bigger than this one. What's strange is this: Bitcoin's four-month slump has come at a time when, in theory, it had everything going for it.
Economist Paul Krugman points out the price of Bitcoin is now lower than it was before America's 2024 election, when candidate Trump promised to make cryptocurrency "one of the greatest industries on earth."

CNN seems to agree with CNBC that what's behind this new crypto winter is "Mostly doubts that bitcoin is 'digital gold,' after all..."

Thanks to Slashdot reader fjo3 for sharing the news.

Elon Musk told podcast host Dwarkesh Patel and Stripe co-founder John Collison that space will become the most economically compelling location for AI data centers in less than 36 months, a prediction rooted not in some exotic technical breakthrough but in the basic math of electricity supply: chip output is growing exponentially, and electrical output outside China is essentially flat.

Solar panels in orbit generate roughly five times the power they do on the ground because there is no day-night cycle, no cloud cover, no atmospheric loss, and no atmosphere-related energy reduction. The system economics are even more favorable because space-based operations eliminate the need for batteries entirely, making the effective cost roughly 10 times cheaper than terrestrial solar, Musk said. The terrestrial bottleneck is already real.

Musk said powering 330,000 Nvidia GB300 chips -- once you account for networking hardware, storage, peak cooling on the hottest day of the year, and reserve margin for generator servicing -- requires roughly a gigawatt at the generation level. Gas turbines are sold out through 2030, and the limiting factor is the casting of turbine vanes and blades, a process handled by just three companies worldwide.

Five years from now, Musk predicted, SpaceX will launch and operate more AI compute annually than the cumulative total on Earth, expecting at least a few hundred gigawatts per year in space. Patel estimated that 100 gigawatts alone would require on the order of 10,000 Starship launches per year, a figure Musk affirmed. SpaceX is gearing up for 10,000 launches a year, Musk said, and possibly 20,000 to 30,000.

European security officials believe two Russian space vehicles have intercepted the communications of at least a dozen key satellites over the continent. From a report: Officials believe that the likely interceptions, which have not previously been reported, risk not only compromising sensitive information transmitted by the satellites but could also allow Moscow to manipulate their trajectories or even crash them.

Russian space vehicles have shadowed European satellites more intensively over the past three years, at a time of high tension between the Kremlin and the West following Moscow's full-scale invasion of Ukraine. For several years, military and civilian space authorities in the West have been tracking the activities of Luch-1 and Luch-2 -- two Russian objects that have carried out repeated suspicious maneuvers in orbit.

Both vehicles have made risky close approaches to some of Europe's most important geostationary satellites, which operate high above the Earth and service the continent, including the UK, as well as large parts of Africa and the Middle East. According to orbital data and ground-based telescopic observations, they have lingered nearby for weeks at a time, particularly over the past three years. Since its launch in 2023, Luch-2 has approached 17 European satellites.

Elon Musk's SpaceX has acquired his AI startup xAI in an all-stock deal that values the combined entity at $1.25 trillion, ahead of what would be the largest initial public offering in history. SpaceX pegged its own valuation at $1 trillion -- a markup from the $800 billion it commanded in a December secondary stock sale -- and priced xAI at $250 billion based on a recent $20 billion funding round that valued the two-year-old AI company at $230 billion.

SpaceX CFO Bret Johnsen told investors on a call Monday that shares in the combined company would be priced at $527 and that xAI shares would convert into SpaceX stock at a roughly seven-to-one exchange rate. The company is still targeting a June IPO expected to raise as much as $50 billion, surpassing Saudi Aramco's $29 billion listing in 2019.

Musk said the least expensive way to do AI computation within two to three years will be in space. "Global electricity demand for AI simply cannot be met with terrestrial solutions, even in the near term, without imposing hardship on communities and the environment," he wrote. SpaceX filed last Friday for permission to launch up to a million satellites into Earth's orbit. xAI merged with Musk's social media platform X last March in a $113 billion deal, and Tesla announced a $2 billion investment in xAI last week.

"A box full of viruses and bacteria has completed its return trip to the International Space Station," reports ScienceAlert, "and the changes these 'bugs' experienced in their travels could help us Earthlings tackle drug-resistant infections..." Scientists aboard the space station incubated different combinations of bacteria and phages for 25 days, while the research team led by biochemist Vatsan Raman carried out the same experiments in Madison, down here on Earth. "Space fundamentally changes how phages and bacteria interact: infection is slowed, and both organisms evolve along a different trajectory than they do on Earth," the researchers explain. In the weightlessness of space, bacteria acquired mutations in genes involved in the microbe's stress response and nutrient management. Their surface proteins also changed. After a slow start, the phages mutated in response, so they could continue binding to their victims.

The team found that certain space-specific phage mutations were especially effective at killing Earth-bound bacteria responsible for urinary tract infections (UTIs). More than 90 percent of the bacteria responsible for UTIs are antibiotic-resistant, making phage treatments a promising alternative.

"There's one big bright spot in the fight against climate change that most people never think about," reports the Washington Post. "It could prevent nearly half a degree of global warming this century, a huge margin for a planet that has warmed almost 1.5 degrees Celsius and is struggling to keep that number below 2 degrees..." [M]ore than 170 countries — including the U.S. — have agreed to act on this one solution. That solution: phasing out hydrofluorocarbons (HFCs), a group of gases used in refrigerators, air conditioners and other cooling systems that heat the atmosphere more than almost any other pollutant on Earth. Pound for pound, HFCs are hundreds or even thousands of times better at trapping heat than carbon dioxide.

Companies are replacing HFCs with new gases that trap much less heat. If you buy a new fridge or AC unit in the United States today, it'll probably use one of these new refrigerants — and you're unlikely to notice the difference, according to Francis Dietz, a spokesperson for the Air-Conditioning, Heating and Refrigeration Institute, a trade group representing U.S. HVAC manufacturers... But that invisible transition is one of the most important short-term tactics to keep Earth's climate from going catastrophically off-kilter this century. HFCs are powerful super-pollutants, but the most common ones break down in the atmosphere within about 15 years. That means stopping emissions from HFCs — and other short-lived super-pollutants such as methane — is like pulling an emergency brake on climate change.

"It's really the fastest, easiest and, some would say, the only way to slow the rate of warming between now and 2050," said Kiff Gallagher, executive director of the Global Heat Reduction Initiative, a business that advises companies and cities on cutting greenhouse gas emissions. The only other solution that comes close to the speed and scale of slashing HFCs would be dimming the sun, a much more controversial and potentially dangerous option... [P]hasing out HFCs now "would buy us a little bit of time to develop other solutions that maybe take longer to implement," said Sarah Gleeson, a climate solutions research manager at Project Drawdown, a nonprofit that models how much different strategies would slow climate change. It could also keep the planet from crossing dangerous climate tipping points this century.

Researchers at the University of New South Wales are developing a "reverse solar panel" that generates small amounts of electricity at night by harvesting infrared heat radiated from Earth. "In the past, scientists have demonstrated that a 'thermoradiative diode' can convert infrared radiation directly into electricity; when used to convert heat from Earth, they exploit the temperature difference between Earth and the night sky, generating a current directly from heat," notes ExtremeTech. "This approach completely eliminates the need for heat to generate steam, though the resulting capacity is fairly low." From the report: The researchers estimate they could generate only about a watt per square meter, which isn't much. One reason for the low output is that the Earth's atmosphere lessens the heat differential that drives the generative process; in space, though, that's not an issue.

Now, researchers believe that the ability to generate power in the moments between direct sunlight could help power satellites. That could be especially true in deep space, where periods without sunlight can be longer, and sunlight is often weaker; in these situations, losing electricity to heat loss is unacceptable.

Many satellites already use heat to generate electricity, though with a much more rarified "thermoelectric generator" that uses rare, expensive materials like plutonium to create heat. With thermoradiative diodes, the heat source can be the Sun-warmed body of the satellite itself.