“The Great Wall of China is not visible from orbit with the naked eye. It’s too narrow, and it follows the natural contours and colours of the landscape.” So wrote the Canadian astronaut Chris Hadfield from the International Space Station during his five-month tour in 2012-2013. Hadfield’s posting was one of dozens of public statements from astronauts who have attempted, and failed, to see the Great Wall from orbit. The consensus among people who have been to space is unambiguous. The wall is not visible from the International Space Station, was not visible from any Apollo mission, was not visible from the Soviet Salyut and Mir stations, and was not visible to China’s first astronaut, Yang Liwei, who spent 21 hours in orbit on the Shenzhou V mission in October 2003.

The result has produced a small but durable embarrassment for the popular fact that “the Great Wall of China is the only human-made object visible from space.” The claim is one of the most widely-repeated pieces of geographical trivia in modern circulation, taught in textbooks, repeated in documentaries, and frequently invoked in casual conversation. It is wrong on at least three counts. The wall is not visible. It is not the only human-made object. And the claim itself predates the technology that would have been needed to verify it.

What astronauts actually report

According to BBC Sky at Night Magazine’s review of the question, the issue with the Great Wall is straightforward: it is too narrow and too poorly differentiated from its surroundings to be visible at orbital distances. The wall averages roughly 5 to 9 metres in width along most of its length. The International Space Station orbits at approximately 400 kilometres altitude. At that scale, the wall is far below the resolving power of the unaided human eye. The wall is also constructed largely of local materials — stone, rammed earth, brick — that share the colour of the surrounding landscape, eliminating the contrast that would be necessary to pick out a narrow feature against its background.

Yang Liwei was direct about the matter when he returned from orbit in 2003. According to Al Jazeera’s coverage of his post-flight interview, Yang told China Central Television that “the scenery was very beautiful, but I didn’t see the Great Wall.” The statement was politically inconvenient enough that Chinese state media reported it carefully, and the country’s geography textbooks were subsequently revised to remove the claim that the Great Wall was visible from space. The American astronaut Leroy Chiao, then commander of the International Space Station, took what is generally considered the first verifiable photograph of the wall from orbit on 24 November 2004, using a digital camera with a 180mm telephoto lens. A second, more famous Chiao photograph followed on 20 February 2005, taken with a 400mm lens in favourable conditions with snow cover and shadows helping to identify the position of the wall against the landscape. Even with the better lens, only short sections of the wall could be identified, and only after extensive comparison with maps.

The Apollo astronauts addressed an even stronger version of the claim. The original popular framing held that the Great Wall was visible from the Moon, a claim several Apollo crews had the opportunity to test directly. Alan Bean of Apollo 12 famously said: “The only thing you can see from the Moon is a beautiful sphere, mostly white, some blue and patches of yellow, and every once in a while some green vegetation. No man-made object is visible at this scale.” Neil Armstrong, Buzz Aldrin, Michael Collins, Jim Lovell, and Jim Irwin all confirmed the same observation. From lunar distance, Earth is a marble. No surface features of any kind, natural or artificial, can be distinguished.

What is visible from orbit

The interesting part of the story, often lost in the popular framing, is what astronauts can in fact see. According to NBC News’s coverage of the question, which interviewed astronaut Ed Lu of Expedition Seven aboard the ISS, astronauts in low Earth orbit can readily see cities, highways, airports, bridges, large dams, ships at sea, and the wakes of large vessels. At night, the artificial lighting of major cities is visible from orbit as bright patterns against the dark sides of continents. Sufficiently large vehicles — aircraft on runways, container ships — can be made out with the naked eye. The list of human-made objects visible from the International Space Station with no optical aid runs to dozens of categories.

The reason these things are visible and the Great Wall is not has to do with size and contrast, not with the impressive scale or fame of the structure in question. The Great Pyramid of Giza, much shorter than the Great Wall but far wider — about 230 metres on each side — is closer to the threshold of orbital visibility, particularly at low sun angles when the play of light and shadow distinguishes it against the surrounding desert. Astronauts have attempted to see the Pyramid with the naked eye and have produced inconsistent reports. The Great Wall, despite being orders of magnitude longer, is at least an order of magnitude too narrow to compete.

Where the myth came from

The most widely-circulated modern version of the claim is generally traced to a Ripley’s Believe It or Not cartoon published in 1932, which stated that the Great Wall of China was “the mightiest work of man, the only one that would be visible to the human eye from the Moon.” Ripley’s was, at the time, one of the most popular newspaper features in the United States, syndicated to hundreds of papers with a combined readership in the tens of millions. The cartoon planted the claim firmly in mid-20th-century popular consciousness, and from there it propagated through textbooks, encyclopaedias, and casual conversation for the next several decades.

The 1932 cartoon was not the earliest version of the idea. The English antiquarian William Stukeley, in a letter dated 1754 about Hadrian’s Wall and later published in his Family Memoirs (1887), wrote that “this mighty wall of four score miles in length is only exceeded by the Chinese Wall, which makes a considerable figure upon the terrestrial globe, and may be discerned at the Moon.” Stukeley’s remark, written more than two centuries before any human had been to space, is the earliest documented version of the claim. The English journalist and travel writer Henry Norman repeated a similar assertion in his 1895 book on the Far East, calling the wall “the only work of human hands on the globe visible from the Moon.” Both of these earlier sources existed in obscurity until historians traced the popular myth backward. Ripley’s, in 1932, brought the claim out of antiquarian obscurity and into the mass cultural mainstream.

The Ripley’s organisation has, in the decades since, hosted on its own website a careful debunking of the claim that originated in one of its cartoons. The Great Wall, the modern Ripley’s article notes, cannot be seen from the Moon, cannot reliably be seen with the naked eye from the International Space Station, and required favourable conditions and a long telephoto lens for even the most successful orbital photograph of it. The claim that survived in popular culture for seven decades was never tested against orbital observation until orbital observation became possible, and the moment it was tested, it failed.

The post The Great Wall of China is not actually visible from space with the naked eye — astronauts from Apollo to the ISS have confirmed it — and the popular myth that it is predates space travel itself, with the best-known version coming from a 1932 Ripley’s Believe It or Not cartoon appeared first on Space Daily.

Three seconds. That is roughly how long a cheetah needs to go from a dead stop to about 60 miles an hour.  The Cheetah Conservation Fund goes a little further, citing acceleration to a top speed past 110 km/h in just over three seconds.

Numbers like these tend to get pressed into a familiar comparison: the cheetah out-accelerates a sports car. The comparison is not wrong but it often leaves out the fact that the animal sustains this only for about half a minute before it has to stop.

Why the supercar comparison holds, and where it breaks

On the acceleration figure alone, the cheetah genuinely keeps pace with fast machinery. A three-second sprint to 60 mph sits in the same range as a great many high-performance cars, and beats most ordinary ones outright.

For context, a Toyota GR Supra 3.0 can do 0–60 mph in 3.9 seconds, while Car and Driver note that a 2025 Porsche 911 Carrera reaches that speed in 3.1 seconds. Sure, the quickest performance cars are now faster — the BMW M3 Competition xDrive at 2.8 seconds to 60 mph — but that only makes the comparison stranger: a wild animal is operating in the same acceleration conversation as serious modern machinery.

The comparison breaks down on duration. A supercar can hold its top speed for as long as the road and the fuel allow. A cheetah cannot. As put by the Cheetah Conservation Fund, “Prey must be caught within about 30 seconds, as maximum speed can only be maintained briefly”. The engine and the chassis are not the same thing as the fuel tank, and in a cheetah the tank is small.

There is a second wrinkle. The headline top speeds, the 110-plus figures, mostly come from captive or estimated conditions. When researchers actually measured wild cheetahs at work, the picture changed.

What the wild data showed

In 2013, Alan Wilson and colleagues at the Royal Veterinary College published a Nature study that fitted five wild cheetahs in Botswana with custom GPS-and-motion collars and recorded 367 hunting runs. The fastest run they captured was striking but earthbound: a top speed of about 93 km/h, or 58 mph. Most hunts involved only moderate speeds. Note that this figure is the top speed in this sample of wild animals, not the species ceiling.

The more telling number is the average. Most runs in the study were well below that record, with the typical chase topping out around 33 mph. The cheetahs were not maxing out. They were managing.

The 30-second ceiling, and the myth around it

So why does the sprint end so soon? For decades the textbook answer was overheating. The cheetah, the story went, hits a thermal ceiling and has to stop before it cooks itself. That figure, a body temperature of 40.5 C, traced back to a single 1973 treadmill experiment in which cheetahs ran at only about 30 km/h.

The physiologist Robyn Hetem put the problem plainly. Hetem noted that the long-standing overheating theory traced back to that single early study. Her 2013 work on free-living cheetahs measured body temperature minute by minute and found it averaged just 38.4 C when chases ended, well below the supposed limit. The animals stopped, but they were not overheating.

If not heat, then what? That question is not fully settled. Hetem’s own candidate is energy, and she keeps it hedged: the cheetahs “may just run out of energy after 30 seconds of sprinting.” Oxygen debt and the sheer cost of anaerobic effort sit somewhere in that explanation. 

Built for the moment, not the chase

What emerges from the data is a different animal than the speedometer suggests. The cheetah’s gift is not sustained velocity. It is the explosive opening, the burst. Its impressive top speed is something it can reach but rarely needs to hold.

The three-second sprint is real. What the collars added is the part the comparison to cars leaves out: the animal is engineered around a window it cannot hold open for long, and almost everything it does in a hunt is an attempt to finish before that window shuts.

The post A cheetah can go from a standstill to about 60 miles an hour in roughly three seconds, out-accelerating many sports cars, but it can’t hold that speed for long appeared first on Space Daily.

Blue Origin’s New Glenn rocket exploded on its launch pad at Cape Canaveral on the evening of May 28, destroying the vehicle and inflicting heavy damage on Launch Complex 36 during what was meant to be a routine static-fire test. No one was injured, but the loss has grounded the company’s only heavy-lift pad indefinitely — and it landed two days after NASA had publicly tied a piece of its Moon program to exactly this rocket.

The failure happened at roughly 9 p.m. Eastern as the first stage’s seven BE-4 engines fired. The rocket was being readied for the NG-4 mission, scheduled for as soon as June 4 with a payload of Amazon Leo broadband satellites. Amazon has confirmed no satellites were aboard during the test.

The worst pad incident at the Cape in nearly a decade

The fireball at Launch Complex 36 is the most destructive event at Cape Canaveral since SpaceX lost a Falcon 9 during a fueling test at neighboring SLC-40 in September 2016. That pad sat dormant for about 16 months before returning to service in December 2017. A loss of this magnitude, depending on the structural damage, could follow a similar timetable.

Video circulated within minutes. The blast was visible across the Space Coast, with a mushroom cloud rising over Brevard County and debris scattered across the pad. Space Launch Delta 45 later warned that debris could wash ashore along public areas in the days and weeks afterward.

Blue Origin acknowledged an anomaly during the hotfire test within roughly half an hour and said all personnel were accounted for.

Bezos and Isaacman respond

Jeff Bezos addressed the loss publicly that night on X. “All personnel are accounted for and safe,” he wrote, adding that it was too early to know the root cause but the company was already working to find it, and that it would rebuild and return to flight.

NASA Administrator Jared Isaacman — who only two days earlier had named Blue Origin hardware to the agency’s first Moon Base mission — said NASA was assessing near-term mission impacts and would provide timeline updates as information became available.

The choreography is by now familiar from high-stakes commercial space failures: acknowledge the loss, frame it as part of the iterative process, get back to the pad. What is different this time is the dependency stack that has built up around New Glenn over the past two years.

Amazon’s constellation hits a wall

Amazon has 24 launches under contract with Blue Origin for its Amazon Leo broadband constellation, with NG-4 slated to carry the first batch of satellites. The entire manifest is now suspended with no resumption date until LC-36 is rebuilt and New Glenn returns to flight.

Leo is already under FCC-imposed deployment deadlines, and every grounded launch tightens that timeline. Amazon faces uncomfortable questions about whether to diversify away from Blue Origin’s heavy lifter, even as alternatives remain scarce. SpaceX, the only operator with comparable cadence, is a direct competitor to Leo through Starlink.

Smaller commercial customers, including those who have looked at New Glenn for direct-to-device launches, are likely to shift toward Falcon 9 manifests already running near capacity.

The Artemis dependency problem

The explosion’s most consequential ripple reaches NASA’s lunar program. Just two days earlier, on May 26, NASA had announced its Moon Base plan, naming Blue Origin’s Mk1 “Endurance” lander to fly the first privately funded lunar lander mission — Moon Base I — to the Shackleton Connecting Ridge near the lunar south pole, carrying NASA’s SCALPSS and a Lunar Retroreflector Array, targeting no earlier than fall 2026.

Endurance launches on New Glenn. The vehicle that would have carried it is now scattered across LC-36, and the pad it would have flown from is the damaged one.

A program already under strain

New Glenn’s operational record is short and uneven. It first flew in January 2025, reaching orbit but failing to recover its booster. NG-2 in November 2025 carried NASA’s ESCAPADE Mars probes and landed its booster for the first time. NG-3, launched April 19, 2026, landed the booster again but suffered an upper-stage cryogenic leak that stranded an AST SpaceMobile satellite in the wrong orbit. The FAA grounded the vehicle, and Blue Origin only received clearance to resume flights on May 22 — six days before this static-fire failure.

NASA’s broader lunar architecture is not positioned to absorb new delays gracefully. The Blue Moon lander, which NASA is counting on as one of two crewed-landing options, also depends on New Glenn to reach space. A rocket that cannot fly cannot demonstrate the launch reliability the agency wants to see before committing crews to Artemis missions later this decade.

The institutional question

Heavy-lift development is brutally hard. SpaceX absorbed multiple Falcon 9 losses on its way to dominance, and Starship has exploded repeatedly during test campaigns. The industry’s tolerance for these failures has grown because the iterative model has produced results.

What sets this incident apart is the timing. Blue Origin secured a flagship NASA role on May 26; its rocket exploded on May 28. The whiplash exposes a fragility that policymakers have been reluctant to confront: NASA’s Moon plans, Amazon’s constellation, and a meaningful share of upcoming national-security launches all flow through a small number of providers whose hardware can fail catastrophically on a single evening.

Bezos has been here before. Years of test failures and skepticism preceded Blue Origin’s first crewed New Shepard flight in 2021, and the company eventually delivered. The open question now is whether New Glenn can recover on a timeline that preserves its role in NASA’s lunar architecture, or whether the agency quietly rebalances toward SpaceX while the investigation runs.

What comes next

The immediate work is forensic. Blue Origin and the FAA will reconstruct what happened during the hotfire. Pad damage will be assessed and insurance claims filed. Range officials in coordination with Blue Origin are evaluating data to determine the cause.

The longer-term question is institutional. On May 26, NASA framed the Moon Base program as its bet on commercial partners to lower costs and accelerate timelines. That bet now depends on Blue Origin showing that May 28 was an anomaly rather than a pattern — and on how fast LC-36, the only pad built for New Glenn, can be rebuilt.

Blue Origin invested more than $1 billion to rebuild that pad before bringing it back into service in 2021. Whether the company’s investors and NASA’s planners have the patience for another long recovery is a separate question — and one that, after a single Thursday evening, is no longer hypothetical.

The post Blue Origin’s New Glenn exploded on its Cape Canaveral pad on May 28 — and the costliest casualty may be the lunar timeline NASA had bet on it just two days earlier appeared first on Space Daily.

The X-59 is expected to cross Mach 1 for the first time in early June 2026 at about 43,000 feet, not as a speed stunt but as the opening move in a regulatory case NASA has been assembling since the United States restricted routine civil supersonic flight over land in the early 1970s.

The aircraft is built to do something narrower and stranger than fly fast. It is built to make a sonic boom arrive on the ground as a quieter pressure signature, the soft “thump” at the center of NASA’s Quesst mission.

That is why the first supersonic run matters. It begins the part of the program where the airplane stops being a shape on a ramp and becomes a flying argument about what the law should measure.

What happens in early June

NASA says the X-59 team expects the aircraft to fly faster than Mach 1 for the first time during a series of test flights in early June 2026, at approximately 43,000 feet and above 630 mph.

That first step is deliberately conservative. The milestone is to cross the barrier, gather data, and keep widening the flight envelope rather than jump immediately to the full mission profile.

The larger target comes after that. NASA says the aircraft will later fly a “mission conditions” profile at Mach 1.4, about 925 mph, at roughly 55,000 feet, the speed and altitude needed for the eventual community demonstrations over the United States.

The aircraft reached 43,000 feet and roughly Mach 0.95 in April 2026 during subsonic testing, according to NASA’s Quesst updates. Those flights were still short of the sound barrier, but they put the airplane close enough for the next series of tests to matter.

Why the thump matters more than the speed

The X-59 is not a prototype airliner. It is a single-seat research aircraft built by Lockheed Martin for NASA to test whether careful shaping can keep shock waves from merging into the sudden crack people associate with a sonic boom.

That shaping is visible before the aircraft ever leaves the runway. The nose stretches far ahead of the cockpit, the fuselage is long and narrow, and the pilot does not look through a forward windshield in the conventional way.

Instead, the aircraft uses an external vision system that feeds forward views to cockpit displays. NASA accepted that unusual cockpit arrangement because the front of the airplane is part of the acoustic design.

The goal is not silence. NASA has described the target as a quieter sonic thump, with expected levels as low as about 75 perceived loudness decibels, compared with Concorde-style booms above 100 PLdB.

That distinction is the entire program. If the public hears a low thump instead of a sharp boom, regulators may have a measurable noise basis for allowing some future overland supersonic operations.

The rule NASA is really testing

The regulation behind the X-59’s importance is not hidden. The FAA rule at 14 CFR 91.817 generally bars civil aircraft from operating in the United States above Mach 1 except under specific authorization.

In June 2025, the White House directed the FAA to take steps to repeal that prohibition and establish an interim noise-based certification standard, making the X-59’s data more politically useful than it would have been even a year earlier.

The order changed the policy direction, but it did not answer the acoustic question. A rule that allows civil supersonic flight over land still needs a defensible number, a test method, and public-response data regulators can use without relying on optimism from aircraft makers.

That is where Quesst fits. NASA plans to fly the X-59 over selected U.S. communities, collect ground measurements, and survey residents about how they perceive the sound.

The result is meant to be a dataset for U.S. and international regulators, not a sales brochure for one airplane. NASA’s own mission language says the community responses will be shared to help set data-driven acceptable noise thresholds for commercial supersonic flight over land.

The two-phase path to the ground signature

The first phase is about the aircraft itself. Engineers have to understand the X-59’s handling, propulsion, structures, flight controls, and instrumentation before they can make a serious claim about what reaches the ground.

That phase began after the aircraft’s first flight on Oct. 28, 2025, when NASA test pilot Nils Larson flew the X-59 for 67 minutes from Palmdale to NASA’s Armstrong Flight Research Center at Edwards, California.

NASA said that first flight stayed subsonic, reached about 12,000 feet and about 230 mph, and kept the landing gear down, which is common practice for an experimental aircraft on its first outing.

The next phase is acoustic validation. Engineers will use ground recording systems and aircraft measurements to determine whether the airplane’s shock pattern matches the low-boom predictions that justified the shape.

Only after that does the public-response campaign make sense. A community survey is not useful until NASA knows the aircraft is producing the kind of pressure signature the mission was designed to test.

Why this is slower than the old supersonic race

The X-59’s cautious pace looks almost theatrical beside the Cold War supersonic programs. The Soviet Tu-144 made its first flight on Dec. 31, 1968, before Concorde, and first went supersonic on June 5, 1969.

Concorde became the famous survivor of that era, but it never solved the overland boom problem. Its commercial life remained tied largely to oceanic routes, and Air France’s Concorde service ended in 2003 after 27 years.

The Tu-144 story was harsher. It was the first supersonic transport to fly and the first passenger aircraft to go supersonic, but the program was damaged by technical problems, crashes, and a short passenger-service life.

The X-59 has a different clock. NASA is not trying to beat another country to a first flight or sell tickets next season. It is trying to give regulators enough physical and human-response evidence to decide whether the old categorical ban can become a noise standard.

Other companies are moving around the same regulatory opening. Boom Supersonic’s XB-1 demonstrator broke the sound barrier on Jan. 28, 2025, and Hermeus announced in March 2026 that its unmanned Quarterhorse Mk 2.1 had received an FAA Special Airworthiness Certificate in the experimental category.

Those programs matter commercially, but they do not replace the X-59’s specific job. NASA’s aircraft is the one built around the low-boom community-response question.

What success would actually look like

Success is not just the X-59 going supersonic. A conventional fighter can do that, and Concorde did it for decades.

Success is a repeatable pressure signature low enough for ground instruments to record as a thump rather than a boom, then a set of community responses showing how ordinary people react when that sound arrives over their homes.

The selected communities have not been announced. NASA’s published planning for the community campaign describes multiple test locations, daytime operations, repeated surveys, and data meant to capture response across different conditions.

That makes the June 2026 supersonic run an opening measurement, not the verdict. The aircraft still has to fly the mission-condition profile, validate its acoustic signature, and then produce the public-response data regulators can use.

The old rule treated Mach 1 over land as the line that mattered. The X-59 is built to test whether the more important line is not the speed of the airplane, but the shape of the pressure wave that reaches the ground seconds later.

If the aircraft works, the sound under its flight path should not be the crack that made Concorde politically impossible over land. It should be a small atmospheric tap from 55,000 feet, quiet enough that the next argument begins with a number instead of a boom.

Related reading on Space Daily: X-59 QueSST more than the sum of its parts, Taming the boom, and Starbase neighbors take SpaceX to court over cracked walls and booming skies.

The post In early June 2026, the X-59 is expected to cross Mach 1 at 43,000 feet, the first sharp proof point in NASA’s fifty-year attempt to turn an overland sonic boom into a certifiable thump appeared first on Space Daily.

The figure for a single email comes from a 2025 peer-reviewed paper in Communications of the ACM by Pengfei Li, Shaolei Ren, and colleagues at the University of California, Riverside. The paper, titled “Making AI Less Thirsty,” sets out the methodology by which the per-query water footprint of large language models can be estimated. The figure for the 100-word email is approximately 519 millilitres, which is close enough to the volume of a standard bottle of water for the bottle to be the practical comparison. The number includes both the direct water used to cool the data centre’s servers and the indirect water used to generate the electricity those servers consume.

The 519 millilitre figure assumes a single response. Most users do not send a single response. They have conversations.

The same research group estimates that a single sustained conversation with a chatbot, defined as somewhere between ten and fifty exchanges, consumes approximately the same 500-millilitre order of magnitude. The figure scales by a factor of one each time the conversation extends.

Why AI needs water at all

Data centres generate heat. The servers processing AI queries are essentially small radiators running at high intensity for as long as the workload continues. The chips at the heart of contemporary AI training and inference, the high-end graphics processing units manufactured primarily by Nvidia, dissipate between 300 and 700 watts each, depending on the model. A single training run for a large language model uses tens of thousands of these chips simultaneously, for weeks or months at a time. The heat has to go somewhere.

The most common method for moving that heat out of a data centre is evaporative cooling. Water is pumped through pipes that run alongside or directly across the heat-producing equipment, absorbs the heat, and is then exposed to the air. A portion of the water evaporates, carrying the heat into the atmosphere as water vapour. The remaining water cycles back through the system. Approximately 80 per cent of the water drawn into an evaporative cooling system is lost to evaporation. The rest returns to local water systems, sometimes at higher temperatures and with chemical residues from the cooling process.

The newer generation of data centres built specifically for AI workloads are larger, more dense, and more thermally intense than the data centres built for general cloud computing in the 2010s. A single large hyperscale AI campus can now consume more water in a day than a town of ten thousand people uses for everything: drinking, washing, cooking, sanitation, agriculture, and irrigation combined.

This video explains exactly what big tech promised and how AI is doing the opposite of that.

How much, in actual numbers

Google’s most recent Environmental Report, covering the 2024 financial year, sets out the water consumption of the company’s global operations in detail. The combined figure for 2024 was approximately 8.1 billion gallons, of which approximately 95 per cent was used at data centres. The 2024 figure was an 8 per cent increase on 2023. The 2023 figure had been a 17 per cent increase on 2022. The 2022 figure had been a 20 per cent increase on 2021. The cumulative result is that Google’s water consumption nearly doubled between 2021 and 2024, with the company itself naming AI workload growth as the primary driver in successive environmental reports.

Microsoft’s figures are similar in shape, smaller in absolute scale. The company reported water consumption of approximately 1.7 billion gallons in 2022, a 34 per cent year-on-year increase. The growth has continued. The independent investigative reporting on Microsoft’s data centre cluster in West Des Moines, Iowa, where the GPT-4 training runs were conducted in 2022, has documented that a single training run consumed 11.5 million gallons of water in July 2022 and another 13.4 million gallons in August. The same cluster has, in subsequent years, expanded to five separate facilities collectively drawing 68.5 million gallons annually from the West Des Moines municipal water system, more than any other industrial user in the metropolitan area.

Meta consumed approximately 813 million gallons globally in 2023, with 95 per cent of that volume used at data centres. Amazon, which operates the largest cloud infrastructure in the world, does not publish aggregate water consumption figures.

The Lawrence Berkeley National Laboratory’s 2024 Data Center Energy Usage Report, prepared for the United States Department of Energy under the Energy Act of 2020, estimated that data centres in the United States consumed approximately 17.4 billion gallons of water directly through cooling in 2023. The same report estimated that an additional 211 billion gallons of water were consumed indirectly through the electricity required to power the same data centres. The indirect figure is approximately twelve times larger than the direct figure. The report projects that the direct figure could double or quadruple by 2028. The indirect figure scales in the same proportion.

Where the water comes from

The Li and Ren paper projects that global AI demand will require somewhere between 4.2 and 6.6 billion cubic metres of water withdrawal annually by 2027. The lower estimate is approximately the total annual water withdrawal of four Denmarks. The higher estimate approaches half the total annual water withdrawal of the entire United Kingdom. Both estimates assume current trajectories of AI workload growth and current water-efficiency practices. Neither estimate accounts for the possibility that AI demand continues to grow faster than the modelled trajectory.

The water has to come from somewhere. In Microsoft’s 2023 sustainability report, the company acknowledged that approximately 42 per cent of its water consumption that year came from regions classified as “water-stressed” under the World Resources Institute’s standard rating system. Google’s equivalent figure for 2023 was 15 per cent of freshwater withdrawals from regions of “high water scarcity.” Both figures, on the trajectory of the past three years, are likely to increase rather than decrease.

The concrete consequences of those abstract percentages are now visible in specific locations. In September 2024, Google announced it was pausing its planned 200-million-dollar data centre in Cerrillos, near Santiago, Chile, after a Chilean environmental court partially reversed the project’s original 2020 permit. The court ruled that the company had not adequately accounted for the impact on the Central Santiago Aquifer in a country that had been in a continuous drought for fifteen years and had begun rationing residential water in 2022. The project is now under revision.

In Querétaro, Mexico, where 32 new data centres are currently planned, the state suffered its worst drought in a century in 2024, with seventeen of eighteen municipalities affected and the drinking water supply for thousands of families at risk. Microsoft has secured rights to approximately 25 million litres of water annually from a local aquifer that is currently running a 60-million-litre annual deficit. In Uruguay, currently experiencing its worst drought in 70 years, Google’s proposed data centre in Canelones would, in its first operational phase, consume approximately 7.6 million litres of water per day, equivalent to the daily residential water needs of 55,000 people. In Goodyear and Buckeye, Arizona, a 14-billion-dollar data centre project was withdrawn in 2024 after local resident organisations successfully pressed elected officials to deny the necessary rezoning. In Aragón, Spain, multiple data centre projects are advancing in regions where agricultural water rights are already contested.

The pattern, on the available evidence, is that the cooling infrastructure for global AI is being built preferentially in regions where freshwater is cheap, regulatory oversight is loose, and the local population is least positioned to negotiate.

What companies don’t disclose

The figures cited above are the figures the companies have made public. The full water footprint of the AI industry is, by every available assessment, larger than the figures voluntarily disclosed in sustainability reports.

Three specific gaps recur across the disclosure landscape. The first is the gap between water withdrawal, which is the volume drawn from local sources, and water consumption, which is the volume permanently lost to evaporation. Most corporate reports name only one of these figures, and the choice between them can shift the apparent footprint by a factor of three or more depending on which is reported. The second is the gap between direct cooling water and indirect electricity-generation water. Almost no corporate report includes the indirect figure, despite the Lawrence Berkeley estimate that the indirect figure is approximately twelve times the direct one. The third is the gap between aggregate global figures and facility-level figures. A company-wide annual total tells a stakeholder nothing about whether the company’s data centre in a drought-stressed Arizona town is straining the local aquifer.

The reasons for the disclosure gaps are several. Some are methodological: the per-facility water footprint of a data centre depends on cooling technology, local climate, electricity-grid mix, and seasonal demand variation, none of which the company necessarily measures with precision. Some are competitive: detailed facility-level water disclosure could give competitors useful intelligence about a company’s infrastructure plans. Some are reputational: a company that discloses its full water footprint and is then criticised for the size of it is exposed to public-relations risk in a way that a company reporting only aggregate figures is not.

The Li and Ren paper’s contribution to the literature is, in significant part, that it produces credible estimates of the gaps. The figures that the AI industry has not been willing to publish are figures that academic researchers, using publicly available proxies for cooling efficiency and electricity-grid water intensity, are now able to estimate within reasonable bounds.

What is at stake

The global infrastructure for processing AI queries is being built faster than any new technology infrastructure in modern history, on a financing trajectory that McKinsey has projected at approximately 5.2 trillion US dollars by 2030. The physical buildings the trillion-dollar investment is producing are, in their fundamental operational requirements, large industrial-scale evaporative cooling systems with computing equipment inside them.

Each query is small. The aggregate is not.

Half the United Kingdom’s annual water withdrawal, evaporating into the atmosphere from cooling towers across the world’s data centres by 2027, is not a marginal correction to a global water balance that is otherwise stable. Global freshwater scarcity is increasing on every measured trajectory. Approximately one-quarter of the world’s population, by United Nations projections, will face severe water stress by 2030. The water the AI industry is now drawing from aquifers, rivers, and reservoirs, increasingly in the regions least able to spare it, is competing directly with that population.

The technologies the AI industry is developing have, by any reasonable analysis, the potential to contribute to solving some of the same water-management problems they are now exacerbating, through better climate modelling, more efficient irrigation, more accurate weather prediction, and more sophisticated drought response. Whether the contribution arrives at scale faster than the consumption does is the open question that determines whether the trade-off, on the long view, is worth it.

On the present trajectory, the answer is unclear.

What the trajectory will look like by 2027 depends on decisions being made, in board rooms and government offices and local zoning meetings, now.

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In the warm coastal waters off the Gulf of California, a small crustacean about the length of a paperclip swims into the gill slit of a spotted rose snapper, crawls forward into the mouth, sinks its hooked legs into the fish’s tongue, and begins to drink.

Over weeks, the tongue withers from blood loss until the soft tissue is gone. The parasite then settles onto the stump of bone where the tongue used to be and stays there, sometimes for years, while the fish opens and closes its mouth around it to eat. The animal is Cymothoa exigua, the tongue-eating louse, and as The Atlantic reported in 2021, it is the only known animal that destroys an organ of its host and then functionally replaces it.

It is not a metaphor. It is not exaggeration. The fish uses the parasite as a tongue.

What the animal actually is

Despite the name, Cymothoa exigua is not a louse in the insect sense. It is an isopod, a crustacean, the same broad group that gives us woodlice and pillbugs. If you have ever flipped over a damp log and watched a roly-poly curl into a ball, you have met its cousins. The marine ones, including the tongue biter, look like armored grey ovals with seven pairs of spindly legs and small dark eyes set at the front.

An adult female can reach up to several centimeters in length. The males are smaller. As Australian Geographic notes, C. exigua is the most famous of a much larger group. Around 100 species of mouth-attaching cymothoid isopods are known worldwide, spread across roughly eight genera, parasitizing fish from the tropics to temperate waters.

Cymothoa exigua is the celebrity because of what it does once it is inside.

The sequence of events inside the mouth

The life of a tongue biter begins with a deadline. A juvenile, only a few millimeters long, hatches into the open water and has hours, maybe a few days, to find a host before it starves or is eaten. If it gets lucky, it enters a fish through the gill opening, a slit just behind the eye.

Here the biology takes a turn most readers do not expect. Every tongue biter starts adult life as a male, clinging to the gill filaments. A subset later transitions into the female form, and only the females migrate forward to the tongue. The first female to reach the basihyal, which is the proper name for the fish’s tongue, claims the spot. Any male that arrives later stays in the gills and, if he is lucky, mates with her there.

The female grips the tongue with her seven pairs of curved legs, which Smithsonian marine-parasite biologist Jimmy Bernot has described as hooked appendages that latch onto the nub the missing tongue leaves behind. She severs the tongue’s blood vessels and begins to feed. The process is slow, and for the parasite’s own sake it has to be. An adult tongue biter cannot swim. If its host dies, the isopod is stranded and sinks, so keeping the fish alive is the only way the parasite stays alive too.

Weeks pass. The tongue’s soft tissue atrophies. Eventually it is gone, leaving only the bony stub of the basihyal underneath. The isopod then settles onto that stub and grips on.

Why the fish does not die

A fish tongue is not like a human tongue. Human tongues are muscular and mobile and do a dozen jobs at once. A fish tongue, called the basihyal, is closer to a hard pad of bone at the base of the mouth. It helps push food back toward the throat and helps shuttle water across the gills. Strip away the soft tissue and the fish still has the bone underneath. Strip the bone, and the gill apparatus collapses, and the fish dies quickly.

Most parasitized fish keep the bone. The parasite eats the meat off the top and then squats on what is left. As NPR reported in 2021, the fish goes on eating, breathing, and swimming, with a live crustacean wedged in its mouth in place of the tongue it used to have.

This is the part that turns a horror story into a biological puzzle. Many tongue-bitten fish look healthy. Their digestive tracts are full. They grow. They reproduce. The presence of the parasite, as Bernot has noted, can be much less catastrophic than it sounds.

The replacement claim, and the fight about it

The bold version of the story, the one that made Cymothoa exigua famous, comes from work examining spotted rose snappers whose tongues had been completely eroded by the isopod. On the backs of the parasites, researchers found small scrapes and grooves, the kind of wear you would expect if the fish had been pressing the parasite against the roof of its mouth, using it the way it would have used a tongue.

If true, it is a biological first. No other known parasite takes the place of an organ it destroyed. As Bernot has put it, this is the only known instance in the entire animal kingdom of a parasite functionally replacing one of its host’s organs.

Not everyone agrees on how clean the replacement is. Kory Evans, the Rice University fish morphologist whose CT scan of a parasitized wrasse sent the tongue biter viral in 2020, is among the researchers who point out that the bony base of the tongue is usually still intact. By that reading, the tongue is mutilated, not gone. The likely middle ground: the soft tissue erodes, the parasite clamps onto the bone underneath, and the fish then uses the parasite to do at least some of the tongue’s everyday work. Biologists in this camp tend to be unbothered by it. Fish, they point out, are remarkably tough, and there is something almost admirable about one pressing a parasite into service as a tool.

Why evolution would build something this strange

From the parasite’s point of view, eating the tongue is risky. As Forbes summarized in 2024, most successful parasites take only what they need and leave the host’s hardware in working order. Cymothoa exigua does the opposite. It eats the very thing the fish needs in order to feed, which means it eats the very thing keeping its food supply alive.

The likely answer, biologists think, is timing. If the parasite can keep the fish breathing and feeding long enough by acting as a stand-in tongue, the female has time to release a clutch of juveniles into the water. The arrangement is a Hail Mary on both sides. The fish gets a working mouth, more or less. The parasite gets a few more weeks of reproductive life. Neither one is thriving. Both are buying time.

It is, as the Atlantic piece put it, evolution working through tinkering, stumbling, and endless trial and error, often producing something less than ideal. The tongue biter is what biology looks like when it does not optimize, when it just stops at the first solution that does not kill everyone involved.

What it looks like, and where you can find it

Cymothoa exigua lives in the eastern Pacific, primarily in the Gulf of California and surrounding waters. It targets snappers most often. If you catch one of these fish and open its mouth, you may see a pair of small dark eyes looking back at you from where the tongue should be. Nerdist has noted that the resemblance to a science-fiction symbiote is hard to shake. The parasite sits flush with the floor of the mouth, legs hooked into place, body oriented the way the missing tongue would have been oriented.

Other cymothoid species do not stop at the tongue. Some attach to the inside of a fish’s cheek. Some burrow into the gill arches. The entire family sits within the broader story of external parasites, animals that have evolved to live attached to the outside, or in this case the inside-outside, of larger hosts.

The tongue biter is rare enough that most fishermen go their whole lives without seeing one. It is common enough that if you spend long enough at a fish market in Baja or coastal Mexico, eventually a snapper will come up with a passenger.

The reason a fact like this matters

Most parasites are invisible to us. They live inside guts and bloodstreams and behind eyes, and we only learn about them through textbooks and microscope slides. The tongue biter is different because it sits where you can see it, in the most public part of the fish, behind teeth that open and close around a creature that has replaced an organ. It is the rare parasite that performs its weirdness in plain view.

Human tongues, by comparison, are so specific to each of us that the bumps and grooves of a single tongue may be as unique as a fingerprint. The fish has none of that complexity to lose. Its tongue is a stub of bone. That is part of why the swap works at all. You could not do this trick on a mammal. The organ is too important, too vascular, too embedded in too many other systems. A fish tongue is simple enough that a crustacean can stand in for it.

The tongue biter is a reminder that the categories we use, host and parasite, harm and help, body and not-body, leak around the edges once you look closely enough. There is a fish swimming somewhere off the coast of Mexico right now with a small grey crustacean wedged into its mouth, its legs hooked into the bone, its eyes pointed forward. The fish is hunting. It is using the parasite to do it. Both of them have been alive together for months, possibly years, and neither one of them, in any meaningful sense, knows that anything is wrong.

The post A tongue-eating louse called Cymothoa exigua swims into a fish’s gills, latches onto its tongue, drinks the blood until the tongue withers and falls off, and then spends the rest of its life acting as a functional replacement tongue the fish uses normally to eat. appeared first on Space Daily.

A leaf goes into a sloth and, in the worst case, takes a full month to come out the other end. Across marker trials in three-toed sloths, food passage varied between 11 and 30 days, averaging 16. That is the slowest digestion recorded for any herbivorous mammal, and it is the kind of figure that invites the wrong conclusion. Read on its own, a 30-day transit time looks like a flaw, an animal so badly engineered it can barely process its own dinner. Read closely, the slowness turns out to be the strategy itself, working as designed.

The number that looks like a problem

A note on species before going further: there are two main sloth groups, the three-toed (Bradypus) and the two-toed (Choloepus), and they differ in diet, metabolism, and behaviour. Most of what follows draws on three-toed sloths, with the two-toed numbers flagged where they appear.

The sloth eats leaves, which is a difficult living. Leaves are low in calories, tough with cellulose, and laced with plant toxins. To get anything out of them, a sloth ferments them in a large multi-chambered stomach using symbiotic gut microbes, a slow process by nature. The Sloth Sanctuary of Costa Rica, summarising Rebecca Cliffe’s carmine-marker trials, calls it “the longest digestive rate recorded for any mammal and is the key behind understanding why sloths are so slow!” The same page notes the true rate is still debated and that older 50-day estimates were probably measurement artefacts, so the superlative is best read as a strong claim rather than a settled one.

Either way, the digestion is slow because everything about the sloth is slow. The leaf does not move quickly because nothing in the animal moves quickly. To understand why, you have to look at what the metabolism is doing.

What the low burn is actually for

The sloth’s answer to a low-energy diet is to need very little energy. A study by Jonathan Pauli and M. Zachariah Peery at the University of Wisconsin-Madison found the three-toed sloth had a field metabolic rate lower than any non-hibernating mammal on record. They measured 162 kilojoules per day per kilogram, against 410 for koalas and 583 for howler monkeys, two other animals that also live in trees and eat plants.

Pauli was direct about how far the result ran past expectation. “We really expected them to have low metabolic rates,” he said, “but we found them to have tremendously low energy needs.” The three-toed rate came in, in his words, “much lower than their cousins, the two-toed sloths, and the lowest documented for any mammal.” The qualifier matters: lowest documented, measured in one study of 10 three-toed and 12 two-toed sloths in Costa Rica, not a final word on every sloth that has ever lived.

To hold the burn that low, the sloth partly gives up on keeping a steady body temperature, drifting with the ambient air more like a cold-blooded animal. 

Two numbers that make the system legible

Two more figures show how completely the slowness runs across every system. The first is the stomach. Because food moves through so slowly, the sloth is essentially always full. Researchers have documented abdominal contents accounting for up to 37% of a brown-throated sloth’s body mass, more than a third of the whole animal given over to a  loaded gut.

The second is the bathroom trip. A sloth descends to the forest floor to defecate only about once a week, every five to seven days. This is the most dangerous thing it does. On the ground, a slow-moving sloth is exposed to predators it could not outrun, and the descent is metabolically costly. The payoff, when it comes, is large: sloths can lose up to a third of their body weight in a single bowel movement, their stomachs visibly shrinking.

Why take the risk at all, rather than simply going in the canopy? No one really knows. Cliffe has speculated that the behaviour must matter to be worth it. “Whatever is going on,” she suggested, “it’s got to be kind of life or death for survival,” before adding that her own hunch leans toward reproduction. That is a hypothesis, not a finding. The weekly descent remains one of the open questions in sloth behaviour.

Mastery, not malfunction

Set the figures side by side and they stop looking like a list of handicaps. The 30-day leaf, the more-than-a-third-of-body-weight stomach, the metabolism running well below the predicted rate, the weekly descent: these are not four separate problems an unlucky animal has to manage. They are one strategy, expressed through every system at once. Slow intake demands slow digestion, which demands a large always-full stomach, which is only sustainable at a metabolic rate low enough to make the whole arrangement cheap. By the measure that matters in evolution, the arrangement works: sloths are among the more abundant medium-sized mammals across their range in the forests of Central and South America, the slowness carried all the way through from the gut microbes to the once-a-week climb down the tree.

The post A sloth can take up to 30 days to digest a single leaf, the slowest recorded digestion of any mammal — its stomach stays so full that its abdominal contents can account for more than a third of its body weight, and it climbs down to relieve itself only about once a week appeared first on Space Daily.

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SpaceX’s Raptor 3 engine — the powerplant the company has spent the better part of two years marketing as a simpler, more reliable replacement for the troubled Raptor 2 — failed multiple times in its maiden flight during exactly the kind of high-stress maneuver it was designed to handle. The Super Heavy booster’s engines began dropping offline seconds into a planned boostback burn, the stage lost the thrust needed to reverse course, and it fell back through the atmosphere and struck the Gulf at high speed. The Federal Aviation Administration has now grounded Starship pending a mishap investigation.

That sequence is the story. Not the paperwork, not the splashdown of the upper stage, not the Starlink mass simulators that deployed on schedule. The most-watched new rocket engine in the world failed in its debut, and it failed in the precise scenario SpaceX needs it to survive for Starship to ever become operational.

Twenty seconds, then a fall

According to telemetry shown on SpaceX’s own webcast, the boostback burn was scheduled to last about a minute. It ended after less than 20 seconds. Several Raptor 3 engines failed to light cleanly almost immediately after ignition, the booster never built the thrust needed to reverse its trajectory, and it fell back through the atmosphere and struck the water at high speed.

The stage came down inside an FAA-activated Debris Response Area, and the agency confirmed the debris fell inside the hazard zone with no reports of public injury or damage to public property. In its own post-flight statement, the FAA reported that the event caused six departure delays and five airborne holding events, with no diversions — the kind of secondary disruption that has become a recurring concern as Starship cadence grows.

The booster failure was not the only Raptor anomaly of the day. One of the 33 Raptor engines on Super Heavy shut down roughly a minute and 42 seconds into ascent, and one of the six engines on the upper stage also cut out before its planned duration. The FAA’s determination formally classifies the incident as a mishap, triggering a federally supervised root-cause review that SpaceX must complete and have approved before another Starship lifts off from Starbase, Texas.

The Raptor 3 debut

The flight was the maiden outing of Starship version 3, the vehicle’s most substantial revision since the program began. The redesign introduced the Raptor 3 engine, which SpaceX has marketed as a simpler, higher-thrust replacement for the Raptor 2 — fewer parts, fewer welds, fewer of the failure modes that plagued earlier flights. The vehicle reached space and completed most of its stated test objectives, including the deployment of Starlink mass simulators and a soft splashdown of the upper stage in its targeted Indian Ocean zone.

The upper stage, in other words, behaved close to nominally. The booster did not.

Engine-out tolerance has always been part of Starship’s design philosophy. Losing one of 33 engines on ascent is, in principle, survivable. But losing multiple Raptor 3 units in quick succession during a planned, choreographed maneuver — the boostback burn is not an edge case, it is core to every operational Starship profile — suggests something closer to a systemic failure mode in a brand-new engine variant making its first flight. That is a categorically different problem from a single random shutdown.

How long the grounding might last

Recent precedent points toward a relatively fast paperwork resolution if SpaceX can isolate the cause. The FAA declared a mishap on Blue Origin’s New Glenn flight on April 19 after the upper stage malfunctioned during its second burn, stranding an AST SpaceMobile satellite in an unrecoverable orbit. Just over a month later, the agency accepted Blue Origin’s investigation report and cleared New Glenn to resume launches.

That precedent comes with a warning, though. Days after being cleared, New Glenn exploded during a static-fire test on May 28, with images suggesting significant damage to its launch complex at Cape Canaveral. A clean regulatory close-out is not the same thing as a clean return to flight. If SpaceX moves with comparable speed on the paperwork, and if the Raptor 3 issue proves tractable, Starship could be back on the pad within weeks rather than months. The harder question is whether a multi-engine failure mode can be diagnosed, fixed, and revalidated that quickly.

The broader picture for commercial launch oversight

Two of the largest privately developed launch vehicles in the world were grounded for mishap reviews within roughly five weeks of each other this spring. That is a notable data point about where the commercial launch industry sits in 2026: ambitious cadence goals, rapid iteration on new engines and upper stages, and a regulatory regime that is increasingly comfortable resolving incidents quickly when no public harm has occurred.

The FAA has also begun signaling that the stakes are rising. The agency has warned pilots to exercise extra caution against “catastrophic” debris hazards in the airspace around Starship’s corridor, and its own analysis suggests the enlarged hazard areas it approved for Starship could affect more than 13,000 commercial aircraft operations annually. The Flight 12 delays and holding events fit that pattern.

For SpaceX, the timing is awkward. The company has been pushing Starship toward operational deployment of Starlink V3 satellites, lunar Human Landing System work for NASA’s Artemis program, and the eventual Mars architecture that Elon Musk has staked the company’s identity on. Each grounding compresses the schedule, and SpaceX flagged Starship’s path to orbit as a milestone in the IPO prospectus it filed in May.

What the test actually proved

The temptation, after any mishap, is to read the result as binary: success or failure. The flight resists that framing.

The upper stage flew its mission. The mass simulators deployed. The splashdown happened where it was supposed to. For a first flight of a substantially redesigned vehicle with a new engine variant, getting the second stage through its full profile is a genuine technical result.

And the booster, while lost, demonstrated something useful in the negative. The Raptor 3’s behavior under boostback stress is now a known problem rather than an unknown one. That is what test flights are for, even when the FAA paperwork that follows is uncomfortable.

The booster is at the bottom of the Gulf. The data it sent back is not — and that data now defines a specific punch list SpaceX has to work through before Starship can fly operationally. The company has to determine whether the multi-engine dropouts trace to a common cause in the Raptor 3 design itself (combustion stability, turbopump behavior, ignition logic under throttle-up) or to a vehicle-level issue in how the new booster feeds and commands those engines during boostback. Each of those answers carries a different fix and a different timeline. A software or sequencing change could be flight-ready in weeks. A hardware redesign of the engine — the variant SpaceX has barely begun producing at scale — is a months-long problem that would ripple straight into the Starlink V3 deployment schedule and into the Artemis lunar lander milestones NASA is counting on. The next few weeks of the mishap investigation will determine which of those futures SpaceX is actually living in.

The post The Raptor 3 was supposed to be the engine that finally ended Starship’s reliability problem — instead, on its first flight, several of them quit less than 20 seconds into the boostback burn, dropping the booster into the Gulf and grounding the whole program for a federal mishap review appeared first on Space Daily.

On 18 February 1930, a young man named Clyde Tombaugh sat at a blink comparator in Flagstaff, Arizona, and noticed a faint point of light that had shifted position between two photographic plates. The plates had been taken on 23 and 29 January. That shift was Pluto, and the moment it was logged, a clock started running that no living person will see finish.

The discovery was announced publicly on 13 March 1930, a date chosen to coincide with Percival Lowell’s birthday and with Herschel’s discovery of Uranus. Pluto was hailed as the ninth planet. What nobody could mark on a calendar that day was how long the new world would take to go once around the Sun.

What one Plutonian orbit actually looks like from the inside

A single Plutonian year runs to roughly 248 Earth years. That number sits so far outside human timescales that it stops feeling like a year and starts feeling like a span of history.

The orbit is not a tidy circle. According to NASA, Pluto’s oval-shaped path can take it as far as 49.3 astronomical units from the Sun and as close as 30. One astronomical unit is the average Earth-Sun distance, so Pluto swings between roughly 30 and 49 times farther out than we are. The path is also tilted about 17 degrees to the plane the major planets share.

That eccentricity does something strange. NASA notes that from 1979 to 1999, near the closest point in its orbit, Pluto was actually nearer the Sun than Neptune. It reached perihelion, its closest approach, on 5 September 1989. Pluto will not reach the far end of its current lap, aphelion, until around 2114.

Why 2178 is a number worth sitting with

Dated from Tombaugh’s discovery, Pluto will complete its first full observed orbit on Monday, 23 March 2178. The orbital mechanics are precise enough to name the day. Nobody alive when Pluto was found will be alive when it crosses back to where it started.

The interval has already swallowed one of Pluto’s defining facts. The International Astronomical Union reclassified Pluto from planet to dwarf planet in 2006, which means it lost its planetary status without completing a single orbit as a planet. Between the 1930 discovery and that 2006 vote, Pluto had covered only about three-tenths of its journey around the Sun.

There is a quieter coda. When NASA’s New Horizons spacecraft flew past Pluto on 14 July 2015, it carried about an ounce of Tombaugh’s ashes. The man who found the point of light got to ride out to it, decades after his death, before the world he discovered had gone even once around its star.

What the incomplete lap tells us about scale

The flyby reframed Pluto from a smudge on a plate into a detailed world. Alan Stern, the mission’s principal investigator, reflected that “Tombaugh’s discovery was so much more than just the discovery of the ninth planet.” Stern added, “I only wish that Clyde had lived to see all that New Horizons discovered and how stunningly beautiful Pluto is.”

For NASA’s Thomas Zurbuchen, the find opened a wider door. As he put it, “What Tombaugh didn’t know then was that Planet X would launch the era of exploration in the third zone of the solar system.” That zone, the cold reaches beyond Neptune, is now known to hold thousands of icy bodies. Pluto was the first of them anyone saw.

The roughly 248 years Pluto needs for one lap is about as long as the United States has existed. It comfortably contains the entire span from the telegraph to the smartphone. A child born the year Tombaugh squinted at his plates would need to live past 248 to watch Pluto return to the same position, and no human has come close to that age. The first full orbit we have ever tracked is one none of us will witness from start to finish.

The clock that started in 1930 is still running, with more than a century left on it. When it finishes, on 23 March 2178, the people watching will not be the people who started counting.

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Around 2.4 billion years ago, the air over Earth began to change. Microbes in the oceans, the cyanobacteria, had been running a chemical reaction that split water and released oxygen as waste. For a long time that oxygen was mopped up almost as fast as it was made. Then the sinks filled, and it began to build up in the sea and the atmosphere, a gas that was poison to most of the life then living.

This is the Great Oxidation Event, sometimes called the oxygen catastrophe. It is often described as the first mass extinction in Earth’s history, a die-off caused not by an impact or an eruption but by life altering its own planet. The poisoning is well grounded in chemistry. The scale of the die-off is an inference, and a much shakier one, for reasons worth being clear about from the start.

How we know the air changed

The strongest evidence for the timing does not come from fossils. It comes from sulfur.

In rocks older than about 2.4 billion years, sulfur isotopes carry a pattern, known as mass-independent fractionation, that can only form when ultraviolet light reaches sulfur dioxide in an atmosphere with no oxygen and therefore no protective ozone. The signature was identified by James Farquhar and colleagues in a 2000 paper in Science. After roughly 2.4 billion years ago it disappears from the record, and that disappearance is now the most widely used marker for the arrival of free oxygen in the air. A 2023 paper in Nature Communications describes the signal as a fingerprint of an oxygen-free atmosphere, while also noting that reading it is less straightforward than it once seemed.

A second line of evidence sits in the iron. Before oxygen accumulated, the oceans held large amounts of dissolved iron. As oxygen spread, that iron reacted and settled out, laying down the banded iron formations that geologists still mine today.

Why oxygen was a poison

Oxygen is reactive.

In cells that evolved without it, it produces what are now called reactive oxygen species, fragments that damage proteins, membranes and genetic material. Many organisms that dominated the early Earth lacked the defences needed to cope with it.

So as oxygen built up, much of the anaerobic world died back. Some lineages did not vanish so much as retreat, into ocean sediments, deep water and other pockets where oxygen did not reach. Their descendants still live in those anoxic refuges. The microbes that caused the crisis, meanwhile, kept producing the very gas that was lethal to their neighbours.

The cold may have done as much as the oxygen

There was a second effect, and it may have been the more destructive one.

The early atmosphere was rich in methane, a strong greenhouse gas that helped keep the planet warm at a time when the Sun was fainter than it is now. Oxygen destroys methane. As oxygen rose, the methane greenhouse collapsed, and the Earth fell into the Huronian glaciation, a run of ice ages spanning roughly 2.4 to 2.1 billion years ago and among the longest and most severe in the planet’s history. Work by Robert Kopp, Joseph Kirschvink and colleagues, published in PNAS, argued that the spread of oxygenic photosynthesis triggered that near-global freeze. If the reading holds, the organisms that poisoned the air also helped chill the surface.

Two killing mechanisms, chemical and climatic, would have arrived together. Neither leaves the kind of record that lets us count the dead.

What the record can and cannot tell us

This is where the popular story needs handling. The microbial life of 2.4 billion years ago did not leave shelly fossils that can be tallied bed by bed, the way the victims of later extinctions can. As the American Society for Microbiology puts it, working out which lineages were lost has proved difficult precisely because the fossil evidence is so thin. Oxygen as a poison is sound. “The first mass extinction,” with the confidence that phrase carries, is a reconstruction laid over a very sparse record.

The “filled the air” part also needs care. Early oxygen levels were a small fraction of today’s, not a breathable atmosphere, and the rise was neither smooth nor in one direction. A 2021 study in Nature led by Simon Poulton found that oxygen fluctuated for around 200 million years before it became a permanent feature of the air, and a 2017 PNAS study by Ashley Gumsley and colleagues spread the onset and tempo of the change across a long interval rather than a single moment. The name suggests an event. The evidence describes a long, uneven transition.

None of this softens the underlying point. Something in the chemistry of the planet changed, life itself caused it, and a great deal of what was alive could not survive the new conditions.

The same gas that ended their world is the one we now cannot live without. Our own lineage runs through organisms that eventually learned not just to survive oxygen but to use it, turning a planetary poison into one of the great engines of complex life. When that turn happened, and how much was lost along the way, are questions still being dated in the rocks.

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Lay every continent and island on the planet side by side, and the total land area comes to roughly 149 million square kilometres. The Pacific Ocean, by most accounts, is larger than that. You could fit all the world’s land inside it and still have open water left over.

The exact surplus depends on whose figure you use, but the direction of the comparison does not change. The US National Oceanic and Atmospheric Administration puts the Pacific at more than 155 million square kilometres and states plainly that this is larger than the landmass of all the continents combined. Other references run higher.

Why the number is a range

Ask for the area of the Pacific and you will get different answers. NOAA gives more than 155 million square kilometres. Britannica lands near 162 million while explicitly leaving out the South China Sea. Some definitions that draw the southern boundary all the way to Antarctica put it closer to 165 million.

The disagreement is not about the water. It is about where the water stops. An ocean has no fixed edges, so the totals shift depending on whether you count the marginal seas and where you draw the southern boundary against the Southern Ocean. On the largest common figures the leftover area, the part of the Pacific that no continent would cover, is roughly 16 million square kilometres, not far off the size of Russia, the biggest country on Earth. On the smaller figures it is more modest. The continents fit inside the ocean in every version.

The biggest ocean is also a shrinking one

It will not hold the title forever.

The Pacific is ringed by subduction zones, the chain of trenches and volcanoes known as the Ring of Fire, where old sea floor is dragged down into the mantle. Around much of its rim that old crust is being consumed at the trenches, and over geological time this has helped make the Pacific a shrinking basin, even as new crust forms along its spreading centres. The Atlantic, by contrast, fed by the mid-ocean ridge running down its middle, is widening.

On the timescales of plate tectonics, tens of millions of years, the Pacific is the surviving remnant of far older and larger oceans, and it is gradually closing. The size that makes it singular today is a feature of this geological moment, not a permanent fact about the planet.

Where “blue planet” undersells, and where it oversells

By area, the premise is fair. Seen from space the Earth is mostly water, the Pacific most of all, and a single ocean outsizes all the dry ground there is. On that measure “blue planet” is, if anything, an understatement.

By volume, though, the impression reverses. The ocean is wide, but it is not deep, at least not relative to the body it sits on. The Pacific averages around 4,000 metres, and Earth’s radius is about 6,371 kilometres, so even the deepest ocean is a skin over the rock. The US Geological Survey makes the point with a thought experiment. Gather every drop of water on the planet, the oceans, ice caps, lakes, rivers, groundwater and atmosphere, into a single sphere, and that sphere would be only about 1,385 kilometres across. Set against a world nearly 12,800 kilometres wide, it is small. The Woods Hole Oceanographic Institution puts the same idea as a basketball and a ping-pong ball: if Earth were the basketball, all of its water would fit in the ping-pong ball.

The USGS calls the oceans a “thin film” on the surface, and the description is accurate.

Both things are true

So the blue is real and it is enormous in reach, covering more than two-thirds of the surface and, in the Pacific alone, more ground than every landmass put together. It is also shallow, mobile, and slowly rearranging itself as the plates beneath it move.

The figure worth carrying away is the first one, because it is the one that catches people off guard. The largest single feature on the surface of the Earth is not a continent. It is an ocean wider than all of them at once.

The post The Pacific Ocean is so large that all the world’s land could fit inside it, and there would still be room left over, which is why calling Earth a “blue planet” is almost an understatement appeared first on Space Daily.

On 27 May 1843, the Scottish clockmaker Alexander Bain was granted British Patent No. 9745 for what he called an electric printing telegraph: a device that used synchronised pendulums to scan a flat metal surface and reproduce its markings, line by line, at a receiving station over a telegraph wire. The patent describes the basic working principle of a fax machine. Bain had invented one. The same year, Charles Dickens was publishing A Christmas Carol, Queen Victoria was six years into her reign, and Alexander Graham Bell, the eventual inventor of the telephone, was minus 4 years old. The fax machine predates the telephone by more than three decades.

The corresponding window of chronological overlap produces one of the more peculiar facts about nineteenth-century technology. The fax existed from 1843. Abraham Lincoln lived until 1865. The Japanese samurai class, despite the popular impression of belonging to a distant feudal past, was still a recognised legal caste in Japanese society throughout Lincoln’s lifetime and was not formally dismantled until well into the 1870s. There was, therefore, a 22-year window — from 1843, the patent of Bain’s machine, until Lincoln’s assassination in April 1865 — during which a samurai could, in theory, have sent a fax to the sitting president of the United States. As a Truth or Fiction analysis of the popular version of this claim documents, the fact has circulated as an internet meme since July 2021 and the underlying chronology checks out, with the kind of practical qualifications that the word “theoretically” exists to cover.

Alexander Bain’s machine

According to Britannica’s biography of Alexander Bain, Bain’s invention came less than seven years after Samuel Morse had patented the electric telegraph. Bain was a clockmaker who had already patented the world’s first electric clock in 1841, and his fax machine grew directly out of his clockwork expertise. The patent describes a system in which two pendulums, one at the transmitting station and one at the receiving station, are synchronised by an electric clock and made to scan their respective metal surfaces line by line. According to HowStuffWorks’s history of the fax machine, the transmitting station’s metal surface was covered with raised metal type. As the pendulum’s stylus passed over the type, it closed an electrical circuit, sending a pulse down the telegraph wire. At the receiving station, the pulse caused a corresponding stylus to mark a piece of chemically treated paper that had been impregnated with a solution. The marks built up, line by line, into a reproduction of the original document.

Bain’s machine was rudimentary by modern standards. The pendulums drifted out of synchronisation, the printed images were faint, and the transmission speed was slow. But it worked, and the principle was sound. The Englishman Frederick Bakewell improved on it in 1848 with a rotating cylinder, and the Italian Giovanni Caselli took the technology to commercial maturity in 1865 with his pantelegraph, which operated a regular commercial fax service between Paris and Lyon between 1865 and 1870. Several thousand documents were transmitted over Caselli’s system, including business correspondence and the signatures on financial instruments. By the time Lincoln was inaugurated as president in 1861, fax technology was no longer experimental. It was a working communications medium in commercial use in Europe.

Why the samurai had not yet been abolished

The popular image of the samurai as a figure from medieval Japan obscures the fact that the samurai class survived until well into the modern industrial era. The transition began with the Meiji Restoration of 1868, which overthrew the Tokugawa shogunate and restored imperial rule, but the dismantling of the samurai class itself was a gradual process that played out over the following decade. According to KCP International’s overview of the abolition of the samurai class, the relevant landmarks were the 1871 abolition of the han domain system, the 1873 Conscription Ordinance that ended the samurai’s military monopoly by establishing a Western-style national army, and the 1876 Haitōrei Edict that prohibited the samurai from carrying their characteristic two-sword set in public. The 1877 Satsuma Rebellion, led by the disaffected samurai Saigō Takamori, was the last armed resistance to the new order, and its defeat marks the practical end of the samurai as a political force.

For the full duration of Lincoln’s life and presidency, none of this had yet happened. When Lincoln was assassinated at Ford’s Theatre on 14 April 1865, the Tokugawa shogunate was still nominally in power, the samurai were still the legally recognised warrior class, and the Boshin War that would dismantle the old regime was still three years away. The viral meme’s specific date of 1867 is an approximation of when the Meiji process began, rather than when the samurai class actually ended, but the broader point holds: the samurai class as a feudal institution was still intact throughout the Lincoln presidency, and the chronological overlap with the fax-machine patent is real.

What “theoretically” is doing

The word “theoretically” in the popular framing of the fact is doing important work. The fax machine existed. The samurai existed. Lincoln existed. All three overlapped in time. What did not exist, during this same window, was the infrastructure that would have been required for an actual transmission. Bain’s machine, like every 19th-century fax system, required a continuous telegraph wire connecting the sending and receiving stations.

Japan did not have a working domestic telegraph network until 1869, four years after Lincoln’s death. The first transpacific telegraph cable connecting Japan to North America was not completed until 1906. A samurai in Japan attempting to fax Washington in 1864 would have faced the immediate problem that there was no wire connecting his country to anything beyond its shores. The technology of the fax existed. The wires necessary to use it across an ocean did not.

The qualification extends further than people who have not looked into it tend to assume. According to a History.com account of the first transatlantic telegraph cable, the first cable was completed in August 1858, with Queen Victoria sending the inaugural message to President James Buchanan on 16 August, but the cable failed within weeks and went silent. A second attempt in 1865 broke during the laying and was abandoned. The first reliable, continuously-operating transatlantic telegraph cable was not in service until 27 July 1866 — more than a year after Lincoln’s assassination. For the full duration of Lincoln’s presidency, from March 1861 to April 1865, no electric signal could be transmitted across the Atlantic Ocean by any means. All communication between Europe and North America during the American Civil War travelled by ship, taking roughly two weeks each way. A samurai in Paris with full access to Caselli’s pantelegraph and the entire European telegraph network of 1864 would still have been unable to send a fax to Washington. The wire to do so did not exist.

The chronology, in other words, is more concrete than it sounds, and the impossibility of the actual transmission is more concrete still. Bain’s 1843 patent is a real document. The samurai’s continued legal existence through the 1860s is a real fact. Lincoln’s presidency overlapped both. The 22-year window in which all three coexisted is the kind of fact that resists easy mental categorisation, because the popular images of “samurai” and “fax machine” sit in mental boxes that do not normally touch. The boxes touched, briefly, in the middle of the nineteenth century. They just happened to do so on opposite sides of an ocean that, for the duration of the overlap, no electric signal could yet cross.

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What follows is reflection on a long-running piece of research, not advice. We are writers and editors reading the literature, not clinicians, psychologists, or therapists. The study at the centre of this piece is observational, and patterns drawn from one cohort are not prescriptions for any single reader’s life.

In 1938, what became the Harvard Study of Adult Development began with the Grant Study, which followed 268 Harvard sophomores. It was later combined with the Glueck Study, which followed 456 boys from Boston. The study not now includes these mens’ offspring. 

The aim was modest and a little vague: to watch ordinary lives unfold and learn what kept people healthy. Nearly nine decades later, it is still running, now with a broader participant base. 

When the researchers pooled what they had collected and looked for what predicted a good old age, the obvious candidates underperformed.  The study director, Robert Waldinger has put it this way:  “When we gathered together everything we knew about them about at age 50, it wasn’t their middle-age cholesterol levels that predicted how they were going to grow old. It was how satisfied they were in their relationships.”  This is a finding from one cohort, not a universal law of medicine, but within this group the relationship measure carried more predictive weight than the markers people tend to worry about.

The pattern appeared elsewhere in the data too. Participants who reported good relationships were, according to summaries of the work, associated with less heart disease, diabetes, and arthritis.

Still, the direction was consistent enough that Waldinger has summed up the headline plainly: good relationships, in his telling, keep us happier and healthier. That is a confident line, drawn from a largely white, male sample, and worth reading as one researcher’s framing of a correlation rather than a settled verdict on everyone.

Waldinger has described the result as a “surprising finding,” that our relationships and how happy we are in them appear to have “a powerful influence on our health.” Influence, not cause. The study cannot prove the arrow runs only one way, and it doesn’t claim to.

Perhaps the strangest thing about the result is how badly it travels. Waldinger’s 2015 TED talk on the study has been viewed more than 29 million times on Youtube alone, and the message is not complicated: tend your close relationships. Anyone who has let a relationship lapse because work felt more urgent has run the small experiment the study runs at scale. The advice is easy to nod at and hard to act on, partly because it competes with everything louder, salaries, titles, the next achievement.

The study’s limits are worth stating plainly, even while taking it seriously. The original cohorts were men, mostly white, and both groups were unusually narrow slices of mid-century America. The headline is a correlation built on that sample, expanded now to spouses and offspring who now number  well over a thousand, but still rooted in one long, specific thread of lives. What it offers is a clue with unusual staying power, not a formula.

If the question of who you are close to, and how that is going, lands somewhere tender, a qualified counsellor or therapist is a good person to talk it through with.

The quiet implication of the study’s own length is the part that stays. It took the better part of a century, four directors, and decades of near-precarious funding to arrive at an answer many people could have guessed at the start. The difficulty was never in finding it. The difficulty is in believing something that ordinary could be the thing that matters most.

The post In 1938, Harvard researchers began following a group of young men to learn what makes a good life. Almost nine decades on, the strongest finding in their data is not wealth or achievement, but something quieter. appeared first on Space Daily.

On 17 August 2017, two neutron stars in a galaxy called NGC 4993, about 130 million light-years from Earth, completed a spiral inward that had taken them millions of years and ended in a collision lasting fractions of a second. The gravitational waves from that collision reached Earth and were detected by the LIGO and Virgo observatories. Within hours, telescopes around the world had identified the afterglow of the event across the electromagnetic spectrum, from gamma rays to radio waves. The event, designated GW170817, was the first confirmed observation of a neutron-star merger. It also resolved one of the longest-standing open questions in astrophysics: where the universe’s gold comes from.

According to the 2017 paper in Nature by Daniel Kasen of UC Berkeley, Brian Metzger of Columbia, and colleagues, the GW170817 event produced and ejected heavy elements totalling approximately 6 percent of a solar mass — roughly 20,000 Earth-masses of material — including about 200 Earth-masses of gold and nearly 500 Earth-masses of platinum, plus comparable quantities of uranium and other elements heavier than iron. The team’s models, developed over the preceding decade in anticipation of exactly this kind of observation, matched the optical and infrared afterglow of the event with sufficient precision to characterise the composition of the ejected material. The colliding neutron stars had assembled, in the violence of their merger, hundreds of times more gold than exists in the entire mass of Earth.

Why ordinary stars cannot make gold

The elements heavier than iron — including silver, gold, platinum, lead, mercury, and uranium — present a problem for the standard theory of stellar nucleosynthesis. Ordinary stars fuse hydrogen into helium, then helium into carbon, and continue fusing progressively heavier elements all the way up to iron. The process releases energy, which is what makes stars shine. But fusion stops working at iron. Combining iron nuclei into heavier elements requires an input of energy rather than producing one, so ordinary stellar fusion cannot proceed past iron. Some heavier elements form slowly in giant stars via a process called slow neutron capture, or s-process, which can build elements up to bismuth. The heaviest elements, including gold, require something else.

The “something else” turned out to be a process called rapid neutron capture, or r-process. In r-process nucleosynthesis, atomic nuclei are bombarded with so many free neutrons in such a short time that they absorb neutrons faster than they can decay, building up to extremely heavy and neutron-rich isotopes which then beta-decay into stable heavy elements. The conditions required — enormously high neutron densities, sustained for fractions of a second — exist almost nowhere in the universe. For decades, the leading candidates were rare types of supernovae and the collisions of compact stellar remnants. The 2017 detection settled at least part of the question. Neutron-star mergers really do produce heavy elements via r-process nucleosynthesis, and they do so in quantities sufficient to enrich entire galaxies.

What a neutron-star merger looks like

A neutron star is what remains when a massive star runs out of fuel, collapses, and explodes as a supernova, leaving behind a dense core. A typical neutron star contains roughly 1.4 times the mass of the Sun, compressed into a sphere about 10 kilometres across. A teaspoon of neutron-star material weighs roughly a billion tonnes. The density is comparable to that of an atomic nucleus, because the star is essentially a single giant nucleus made of densely-packed neutrons. When two neutron stars exist in a binary system, they slowly lose energy through gravitational wave emission and spiral inward over geological timescales. The final phase of the inspiral, when the two stars are within a few kilometres of each other, can complete in fractions of a second. The GW170817 neutron stars were spinning around each other more than 300 times per second in the final moments before merger.

The collision itself is described in the literature as a kilonova — a term coined by Brian Metzger and colleagues in 2010, who calculated that the light from a neutron-star merger would be approximately one thousand times brighter than a typical nova explosion but much fainter than a typical supernova. According to Lawrence Berkeley National Laboratory’s coverage of the GW170817 detection, the radioactive decay of the freshly synthesised heavy elements in the ejected debris is what makes a kilonova glow. The team’s models had predicted that this glow would be “tinged red if heavy elements were produced,” distinctive enough to identify the kilonova by its colour signature. The 2017 observations matched the predictions in detail, providing the first direct spectroscopic evidence of r-process nucleosynthesis as it happens.

What this means for the gold on Earth

The gold in any wedding ring, any coin, any bar of bullion sitting in any bank vault on Earth, was produced in events like GW170817 that occurred long before the Solar System existed. The Sun and its planets formed approximately 4.6 billion years ago, from a cloud of interstellar gas and dust that had been enriched, over previous billions of years, by the ejecta of supernovae and kilonovae from the prior generations of stars in the Milky Way. The heavy elements in that cloud, including all the gold, had been scattered across hundreds of light-years by the violence of their original production. The cloud collapsed under its own gravity, the Sun formed at the centre, and the remaining material accreted into the planets. Earth inherited its share of pre-existing heavy elements from this enriched cloud.

The Earth as a whole contains roughly 1.6 × 10²¹ grams of gold, most of it in the planet’s core, where it sank during the molten phase of Earth’s early history. The gold accessible at Earth’s surface, and therefore the gold that has been mined throughout human history, represents a small fraction of the total — itself the result of a late veneer of asteroid impacts that delivered fresh heavy elements to the crust after the core had finished forming. Every gold atom in human possession spent billions of years in interstellar space before it became part of Earth, and was produced billions of years before that in the collision of two dead stars somewhere in the early Milky Way or one of its progenitor galaxies.

The 2017 confirmation also left an open question, which is still under active investigation. According to a 2024 analysis by the astrophysicist Ethan Siegel, the rate of observed neutron-star mergers may be too low to fully account for the abundance of gold and other heavy elements in the present-day universe. Other mechanisms — including a rare type of supernova called a collapsar, in which a massive star’s core collapses directly to a black hole, and magnetar giant flares, in which the magnetic fields of highly magnetised neutron stars rearrange catastrophically — may contribute additional r-process production. The 2017 event confirmed that neutron-star mergers produce gold. It did not settle whether they produce all of it. What is settled is that most of the gold on Earth was forged in events of cosmic violence whose like has not been seen near our solar system since long before our solar system existed.

The post Almost all the gold on Earth — every wedding ring, every coin, every gram in every bank vault — was forged in the collision of dead stars billions of years ago, in events so violent that a single one can produce hundreds of Earth-masses of gold, and the heavy elements were then scattered across the galaxy before our sun was even born appeared first on Space Daily.

The fossil record contains the unambiguous evidence of five separate occasions on which most of the species alive at the time died, in geological terms, very quickly. According to the Natural History Museum’s reference on mass extinctions, a mass extinction is conventionally defined as an event in which roughly 75 percent of the world’s species are lost over a short period of geological time — less than 2.8 million years. The Big Five mass extinctions are the End-Ordovician (~445 million years ago, glaciation and sea-level collapse), the Late Devonian (~360-375 million years ago, marine anoxia), the End-Permian “Great Dying” (~252 million years ago, the worst single event in life’s history), the End-Triassic (~201 million years ago, large-scale volcanism), and the End-Cretaceous K-Pg event (~66 million years ago, the asteroid impact that ended the non-avian dinosaurs).

Each of these events removed most of the multicellular biosphere over a span ranging from a few tens of thousands of years to perhaps a million years. Each was caused by some external disruption to the planet’s climate, atmosphere, or oceans: glaciation, marine de-oxygenation, runaway volcanic CO₂, or a large extraterrestrial impact. Each was followed by a long recovery interval, on the order of millions to tens of millions of years, during which surviving lineages diversified into the ecological roles left empty by the extinct species. The current biosphere is largely a product of the most recent of these recoveries. Mammals, including humans, occupy ecological space that became available when the dinosaurs died.

The case for a sixth extinction

The argument that the planet is now in the early stages of a sixth mass extinction has accumulated substantial peer-reviewed support over the past several decades, although it remains contested. The case is built on three observations.

The first is the extinction rate. A 2015 paper in Science Advances by Gerardo Ceballos of the National Autonomous University of Mexico, Paul Ehrlich of Stanford and colleagues looked at the documented loss of vertebrate species since 1900. The team identified 477 vertebrate extinctions in the modern record, against a background rate that would predict approximately 9. Even using deliberately conservative assumptions, including a background rate twice as high as previous estimates, the team concluded that current vertebrate extinction rates are between 8 and 100 times higher than the rate that would prevail in the absence of human activity. Under the background rate, the number of species lost in the past century would have taken between 800 and 10,000 years to disappear, depending on the taxonomic group.

The second is the cumulative loss. A 2022 review published in Biological Reviews by Robert Cowie of the University of Hawai’i at Mānoa and colleagues at the Muséum National d’Histoire Naturelle in Paris extrapolated from invertebrate extinction data, particularly from land snails and slugs, to estimate that Earth may already have lost between 7.5 and 13 percent of its known two million species since the year 1500, or between 150,000 and 260,000 species. The Cowie team argued that previous estimates focusing on charismatic vertebrates had substantially understated the scale of loss, because most of life’s diversity is invertebrate and most invertebrate extinctions are not officially documented.

The third is the cause. Where the previous five mass extinctions were driven by external geological forces, the current acceleration of extinction is the consequence of a single species. Human activity has converted approximately half of the planet’s habitable land surface to agricultural and urban use, raised atmospheric CO₂ concentrations by about 50 percent above pre-industrial levels, acidified the surface oceans by roughly 30 percent, and introduced invasive species, novel chemical pollutants, and direct hunting pressure across nearly every habitat on Earth. The Cretaceous-Paleogene extinction was caused by an event lasting hours. The Permian extinction was caused by a million-year volcanic episode. The sixth extinction, if it is occurring, is being caused by a few centuries of industrial expansion.

The case against

The framing has been challenged in the peer-reviewed literature, most recently by John Wiens of the University of Arizona and Kristen Saban of Harvard. A 2025 paper by Wiens and Saban in PLOS Biology, summarised in CNN’s coverage, examined extinctions at the genus level — a higher taxonomic rank than the species — using data from over 163,000 plant and animal species in the International Union for Conservation of Nature’s database. The team found that 102 genera had gone extinct over the past 500 years, representing less than 2 percent of mammal genera and less than 0.5 percent of all assessed genera. By the 75-percent threshold that defines a mass extinction in the geological record, the current crisis is nowhere close. Most documented extinctions, the Wiens and Saban paper noted, have involved species confined to islands rather than continental ecosystems.

The Wiens and Saban critique does not deny that biodiversity is declining sharply or that human activity is the cause. The point is more specifically about whether the current decline meets the technical definition of a mass extinction. Wiens has argued that the term should be reserved for events that demonstrate a 75-percent species loss, and that calling the current crisis a “sixth mass extinction” overstates what the data so far supports. The dispute is over framing rather than over the underlying observations of accelerating biodiversity loss.

What both sides agree on

The disagreement among biologists about whether a sixth mass extinction has begun should not obscure what is not in dispute. Current extinction rates are far above geological background. The cause is overwhelmingly anthropogenic, including habitat loss, climate change, pollution, invasive species, and direct exploitation. The trajectory of biodiversity loss is accelerating rather than slowing. Many species are functionally extinct in their natural ranges, even when small captive populations or remnant wild populations technically meet the criteria for not-yet-extinct status. The disagreement is about whether what is happening now is best categorised alongside the End-Permian or as a serious but historically distinct biodiversity crisis.

The difference matters for how the situation is communicated and what kinds of policy responses are warranted, but it does not materially change the underlying picture. By either framing, a substantial fraction of Earth’s species are being driven to extinction or to near-extinction over a time interval that is unprecedented in human history and brief by geological standards. The previous five mass extinctions were caused by climate change driven by volcanism, by ocean chemistry shifts driven by tectonic processes, and in one case by a six-mile-wide asteroid hitting the Yucatán. The current crisis is the first in Earth’s history caused by the deliberate and incidental activities of a species that emerged less than half a million years ago and that, on most accounts, has the option of choosing differently.

The post Earth has gone through five mass extinction events in its history, each wiping out the majority of life on the planet — and many biologists argue we are currently in the early stages of the sixth, caused not by an asteroid or a volcanic eruption but by a single species changing the planet’s atmosphere, oceans, and ecosystems faster than other species can adapt appeared first on Space Daily.

At the 1912 Summer Olympics in Stockholm, winners of individual events received medals that were exactly what their name promised. Each was struck in solid gold. They were the last of their kind. 

So what is an Olympic gold medal actually made of, and why did the real thing disappear after a single Games in 1912?

What a modern gold medal is actually made of

The short answer is silver. Under the rules of the International Olympic Committee, a “gold” medal must be at least 92.5 percent silver, the same purity standard used for sterling silver. 

In everyday terms, a recent gold medal carries roughly 500 grams of silver under those six grams of gold. The gold you can see accounts for a little over one percent of the medal’s weight. The thing draped around a champion’s neck is, by mass, a silver disc that has been gilded.

Why the solid version vanished

As you might have guessed, the change came down to cost and scale. Gold is expensive, the Games keep growing, and minting hundreds of solid-gold medals every few years stopped being practical. The 1912 Games offer the clearest illustration of how small the original supply was: just 90 solid gold medals were struck, reserved for winners of individual events.

That arrangement already hints at the compromise. Even in 1912, organisers limited the solid metal to a narrow group. Medals presented to members of winning teams were made of solid silver plated in gold. Team winners were already getting gold-plated silver.

After Stockholm, that became the rule for everyone.

What the 1912 winners actually held

The Stockholm medals were not large. An individual-event gold medal from those Games was only about 26 grams and 36mm in diameter. Compact, dense, and genuinely valuable as metal, they were closer in spirit to a coin than to the broad discs handed out today.

The scarcity has held its value over time. A 1912 Stockholm solid gold medal sold at auction for $35,851 in January 2023. The price reflects what the medal represents rather than the metal alone, but the metal is, at least, real gold all the way through.

Melt value versus what it fetches

For a modern medal, the materials are worth far less than the moment suggests. At recent precious-metal prices, the melt value of an Olympic gold medal sits at around $2,500. The Tokyo gold medals awarded in 2021 were worth roughly $800 in metal at the prices of the day.

The ceiling is another matter. Bobby Eaton, an Olympics memorabilia expert at RR Auction, has handled some of those sales. Greg Louganis’s 1984 springboard diving gold sold for just under $200,000, a figure that shows how far collectible value can run past metal value.

Of course, most athletes never test those numbers, because the value to them is not in the metal at all.

The post Just six grams of gold coat an Olympic “gold” medal, which is otherwise mostly silver — the last solid-gold medals were handed out at the 1912 Stockholm Games appeared first on Space Daily.

About 66 million years ago, an asteroid roughly 10 to 12 kilometres across struck a shallow, sulfur-rich carbonate platform near what is now Chicxulub, on Mexico’s Yucatán Peninsula. It opened a crater close to 180 kilometres wide and marks the boundary at which around three-quarters of species in the fossil record disappear, the non-avian dinosaurs among them.

The worst direct physical destruction was concentrated around the Gulf of Mexico and nearby regions. But that alone does not explain an extinction that reached the far side of the planet. For that, the more important story is what the impact did to the atmosphere, first within hours, then over the years that followed.

The crater was the wound. The atmosphere was the weapon.

The first hours: heat from above

The impact flung molten rock out of the atmosphere on ballistic paths. As those droplets, by then solidified into glassy spherules, fell back across the globe and decelerated, they heated the upper air. Models by Douglas Robertson and colleagues, set out in a 2013 paper in the Journal of Geophysical Research: Biogeosciences, estimated that this produced an infrared pulse at the ground comparable to an oven set to broil for a period after impact.

The heat, in other words, came down out of the sky, far from the crater itself.

Whether that pulse lit the whole world on fire is disputed. Tamara Goldin and Jay Melosh argued in a 2009 paper in Geology that the falling spherules would have shielded the surface from much of their own radiation, shortening the pulse below the threshold needed to ignite wood across the planet. A 2013 modelling study in the same journal found that fires ignited in some directions from the impact but not as a single uniform global firestorm. The heat pulse is well grounded. The claim that it burned the entire biosphere at once is not.

The years after: the sky stayed shut

The longer and, on the available evidence, more lethal effect was darkness and cold.

The rock at the impact site was rich in sulfate and carbonate. Vaporising it threw sulfur into the stratosphere, where it formed light-blocking aerosols, alongside soot from burning vegetation and fine rock dust. With sunlight cut, photosynthesis on land and at the sea surface fell away within weeks. Temperatures dropped for years. A 2014 study in PNAS, drawing on temperature proxies preserved in marine sediments, found evidence of rapid, severe cooling in the immediate aftermath, consistent with an impact winter rather than a slow decline.

This is the part that fits the survival record. The animals that came through tended to be small, able to shelter, burrow or live in water, and able to feed on detritus rather than fresh growth. A filter that spares the burrowers and the scavengers looks less like a blast wave and more like a world that went dark and stopped growing food.

What the newest modelling adds

The relative contributions of sulfur, soot and dust are still being weighed. The most recent reweighting came in 2023, when Cem Berk Senel and colleagues published palaeoclimate simulations in Nature Geoscience, constrained by grain-size measurements from the Tanis K-Pg boundary deposit in North Dakota. They found a larger share of very fine silicate dust, around 0.8 to 8 micrometres across, than earlier work had assumed.

In their simulations that dust lingered in the atmosphere for as long as 15 years, contributed surface cooling of up to about 15 degrees, and held photosynthesis near a standstill for close to two years. The authors are careful with the result. They present the dust as acting together with sulfur and soot, and they note plainly that the exact killing mechanisms remain poorly constrained. This is one study sharpening a debate, not closing it.

Why the distinction matters

The popular image folds a regional catastrophe and a global one into a single instant: the rock hits, the dinosaurs die. The chemical evidence that first tied the extinction to an impact, the iridium layer reported by Luis and Walter Alvarez and their co-workers in 1980, said nothing about how the dying actually happened. The crater told us where. The atmosphere is where the mechanism lives.

Read that way, the premise holds. The impact loaded the sky, with heat in the first hours and with sun-blocking particles for years afterward, and it was the sky that reached every continent.

What remains genuinely open is the accounting. How much of the cooling belongs to sulfur, how much to soot, how much to dust, and how lethal the early heat pulse really was, are questions that turn on fine measurements of boundary sediments like the ones at Tanis. The crater has been mapped for decades. The years that followed it are still being reconstructed.

The post The asteroid that ended the dinosaurs did not just leave a crater, it turned the sky into a weapon, and the worst damage may have come after the impact itself was already over appeared first on Space Daily.

The Amazon is the largest river on Earth by volume of flow, and it reaches the sea by running east, from the foot of the Andes across the width of the continent to the Atlantic. For much of the deep past, the rivers of this region ran the other way. Sediment was carried west and north, toward what is now the Pacific side of the continent and toward the Caribbean, not east toward the ocean the river empties into today.

This is not a story about a single channel flipping overnight. It is a reconstruction, assembled from rock chemistry, fossil pollen, drill cores and numerical models, of a whole drainage system that was reorganised over tens of millions of years as the Andes rose and the eastern lowlands slowly filled with sediment. The broad outline is widely accepted. The timing and the mechanism are still argued over.

What the rocks record

One line of evidence for the older, westward drainage comes from tiny crystals. Grains of the mineral zircon lock in a uranium-lead age when they form, which acts as a fingerprint for the rock they eroded from. Comparing zircon ages in ancient Amazonian sediments with the ages of likely source rocks lets geologists work out which way the rivers that laid them down were running.

Work presented by Russell Mapes and colleagues at the University of North Carolina at the 2006 Geological Society of America meeting reported zircon ages in western deposits that pointed to central and eastern South American sources. The implication is that the sediment had been carried westward, and that in the Cretaceous, before the Andes had risen to any height, rivers drained that way across the continent. This was conference-presented work rather than the field’s strongest peer-reviewed anchor, but it sits comfortably with the wider reconstruction.

A long, low basement ridge through the middle of the continent, the Purus Arch, later split the flow, sending water on its eastern side toward the young Atlantic and water on its western side back toward the rising mountains.

The Andes as a barrier, and a sediment factory

As the Andes grew through the Cenozoic, they did two things at once. They blocked the old westward drainage, and they began shedding large volumes of eroded rock into the lowlands at their feet.

For most of the Miocene, roughly 23 to 10 million years ago, western Amazonia was not a river system at all but a shifting expanse of lakes, swamps and channels known as the Pebas system. It reached its greatest extent around 17 to 15 million years ago, was episodically connected to the Caribbean, and drained north rather than east. The reconstruction of this wetland and its history is set out in a 2022 review in the Botanical Journal of the Linnean Society led by Carina Hoorn, building on a 2010 synthesis she led in the journal Science.

The eroded Andean sediment had to go somewhere. As it filled the foreland basins and the lowlands subsided under the load, the gentle slope of the continent was gradually rebuilt to tilt east. A 2014 modelling study by Victor Sacek, published in Earth and Planetary Science Letters, found that this reorganisation emerged in the simulations across a wide range of assumptions about how fast the Andes rose and how quickly their rock eroded. In his model it could be produced by surface processes alone, Andean uplift, erosion, sedimentation and the flexing of the crust under that load, with mantle-driven dynamic topography a secondary contributor rather than the main driver. The timing turned mainly on how efficiently sediment was carried and how fast the Andes rose. One run placed the formation of the modern basin at about 10.5 million years ago, close to the figure Hoorn’s group has argued for.

When the river turned east

Most reconstructions place the establishment of the through-flowing, east-draining Amazon in the late Miocene, somewhere in the range of about 9 to 11 million years ago. Sediment of clearly Andean origin began reaching the Atlantic shelf and building the submarine Amazon Fan from around 11 million years ago, which is one of the firmer markers for when the river first connected the mountains to the ocean.

That range is not a precise date, and it should not be read as one. The watershed kept rearranging itself afterwards, through the cooler, more variable climates of the past few million years.

What the evidence supports is a window, not a stopwatch.

Two explanations that may not be rivals

There is genuine disagreement about what did the heavy lifting. Sacek’s account leans on Andean uplift, the bending of the crust under sediment load, and the slow infilling of the basins, with the mantle in a supporting role. A 2010 study by Grace Shephard and colleagues in Nature Geoscience put the deeper cause first. As South America drifted west over cold, dense slabs of sinking ocean floor, the resulting flow in the mantle below pulled parts of the continent down and let others rebound, tilting the surface eastward from beneath.

These are not necessarily competing stories. Surface processes and mantle flow can both contribute, and much of the live argument is about their relative weight rather than whether the river moved at all. The degree of marine flooding that reached the Pebas wetland from the Caribbean is contested in the same way, with the available rock and fossil evidence read more than one way.

What the story actually shows

The popular version, that the Amazon ran backwards, compresses a staged, drawn-out reorganisation into a single flip. The more accurate picture is of a continent whose slope was rebuilt by the mountains on its western edge, until the water had no choice but to find the Atlantic.

It is a useful reminder that a river of this size is a relatively recent arrangement, and a temporary one. The Amazon mapped today is the current balance between uplift, erosion and deposition, not a fixed feature of the planet. What remains to be pinned down, through more drill cores and more provenance dating, is the exact timing of the turn and how much of it was driven from the surface and how much from far below.

The post The Amazon’s ancient drainage system once ran the other way, carrying water and sediment westward across South America before the rise of the Andes, shifting land levels, and massive sediment buildup helped turn it into the east-flowing river we know today. appeared first on Space Daily.

Most people would say Venus is Earth’s nearest planetary neighbour. Averaged across its orbit, though, the planet that stays closest to Earth is Mercury. The claim comes from a 2019 commentary in Physics Today by Tom Stockman, Gabriel Monroe and Samuel Cordner, and it has a tidy, faintly irritating quality: it is correct, and it is mostly a point about what the word “closest” is being asked to do.

The usual answer is not wrong so much as it is answering a different question.

Why people say Venus

Venus is the planet whose orbit runs nearest to Earth’s, and the one that makes the closest single approach. When Venus passes between Earth and the Sun, the gap between them can fall to about 38 million kilometres, closer than any other planet comes. Venus is also the planet most similar to Earth in size. So calling it our closest neighbour is reasonable, as long as “closest” means “comes nearest at its nearest.”

The authors point out that even NASA’s own materials have described Venus as our closest planetary neighbour. By the closest-approach measure, that holds.

What the calculation actually shows

The trouble starts with how the average distance between two planets is usually worked out. The common shortcut is to take each planet’s average distance from the Sun and subtract one from the other. For Earth and Venus that gives a small number, and Venus comes out closest on average.

That shortcut quietly assumes the two planets sit on the same side of the Sun. They rarely do. Most of the time the planets are scattered around their orbits, often on opposite sides of the Sun from each other, and the subtraction ignores all of that.

Stockman and his colleagues used two approaches instead. One was a formula they called the point-circle method, which averages the distance across every position each planet can occupy. The other was a simulation that placed the planets in their orbits and stepped forward every 24 hours for 10,000 years, recording which planet was nearest Earth at each step. Over that run, Mercury was Earth’s closest planet about 47 per cent of the time, Venus about 36 per cent, and Mars about 17 per cent.

The part that surprises people

The same calculation produces a stranger result. By this averaging, Mercury is not only Earth’s closest planet on average. It is the closest planet, on average, to every other planet in the solar system, the outer giants included.

The reason is that Mercury hugs the Sun. It never strays far from the centre of the system, so it never gets very far from anything else. A planet on a wide outer orbit spends long stretches on the far side of the Sun from any given neighbour. Mercury, kept close in, avoids those long absences. It wins on consistency rather than on any single close pass.

What it does and does not mean

It does not mean the order of the planets has changed. Mercury is still the innermost planet, and Venus’s orbit is still the one that runs closest to Earth’s. It does not mean Mercury ever comes physically closer to Earth than Venus does at its nearest. Venus still holds the record for the closest approach.

What changed is the answer to one specific question: averaged over a long span of time, which planet is nearest. Not everyone accepts that this is the most useful sense of “closest neighbour,” and the disagreement is mostly about the definition rather than the arithmetic, which is not really in dispute.

There is a practical version of the question too, and it has not changed. For anyone planning a spacecraft, the time-averaged distance is not the figure that matters. What matters is the geometry at launch and the close approaches that open transfer windows, and by that measure Venus and Mars are still the near targets they have always been.

The Mercury result rearranges a piece of trivia. It does not rearrange the solar system.

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