The 2026 rankings, released on September 1, count alumni whose companies took venture capital over a ten-year window. That is a decade of Series A slide decks, closed rounds, missed rents, IPOs, quiet acquisitions and dead cap tables — all funnelled into one number for each school.

Berkeley’s number is bigger than anyone else’s. Again.

What PitchBook actually counted

PitchBook’s 2026 methodology drew on educational and investment data for more than 222,000 venture-backed founders globally. Each founder was tagged to the institution where they earned an undergraduate degree. Every startup they founded that raised venture capital in the ten-year window got attributed back to that school.

So the ranking is not a measure of MBA output. It is not a measure of who runs the best incubator. It is a count of what 22-year-olds from a given campus went on to build in the ten years after commencement, weighted by whether a professional investor was willing to write them a check.

Berkeley: 2,380 undergraduate alumni founders. 2,155 companies. Four years running.

The number in context

Berkeley’s founder count is roughly three times that of the top-ranked Indian institution. IIT Bombay, which came in at 22nd globally, produced 756 founders and 590 companies over the same decade. The University of Mumbai, ranked 74th, produced 339 founders and 316 companies that raised a combined $12.9 billion.

To put Berkeley’s 2,380 in a physical frame: that is roughly the size of an entire graduating class at a mid-sized liberal arts college. Every one of those people started a company that took outside money.

The United States dominates the top 100. Eight Indian institutions made the cut, up sharply from a decade ago.

Why Berkeley keeps winning

Three structural things sit under the number.

The first is scale. Berkeley has a large undergraduate enrollment and admits a substantial computer science and engineering cohort every year. Stanford’s undergraduate body is smaller. When you count raw founder output, a big public university with a strong technical program has a mathematical head start on a small private one.

The second is proximity. The Berkeley campus is a 40-minute BART ride from downtown San Francisco and about the same drive to Palo Alto. Sand Hill Road — the strip of venture capital offices in Menlo Park that has funded roughly half the internet — is inside the same commute radius as a Berkeley student’s dentist.

The third is the compounding effect of alumni networks. A Berkeley undergraduate in 2026 who wants to raise a seed round can find a Berkeley alum inside almost any Bay Area VC firm. According to Johnny Edward, a partner at Grant Thornton Bharat, discussing the IIT rankings, these advantages have compounded over several decades, including selective admissions, alumni networks, incubation infrastructure and investor connections.

Berkeley has had all four of those things, near a working venture capital cluster, for fifty years.

What “venture-backed” actually means

The word matters, because it filters out most companies. A venture-backed startup is one where a professional investor — a firm managing pooled capital from pension funds, endowments and wealthy individuals — has bought equity in exchange for a check, usually starting at a few hundred thousand dollars and often running into tens of millions.

Venture capitalists reject the overwhelming majority of pitches they see. Standard industry rule of thumb: a partner meets with a few hundred companies to fund one. So each of Berkeley’s 2,155 companies represents a founder who convinced a professional skeptic that the business was worth a bet.

That is a higher bar than “started a company.” It is a much higher bar than “had a business idea.”

The female founder number

Berkeley also topped the PitchBook ranking for undergraduate universities producing female founders, according to The Daily Californian’s coverage of the rankings. Women remain a minority of venture-backed founders globally — a persistent gap that has narrowed slowly over the past decade — and Berkeley’s lead in that subcategory is smaller than its lead in the overall count, but it exists.

The same ecosystem effects that drive the overall number seem to be working in the female-founder subcategory: a large undergraduate body, technical majors, proximity to capital, and enough alumni role models that a first-time founder can find someone who looks like her already doing the job.

The Indian surge

The 2026 list is notable not just for Berkeley’s persistence but for how much of the top 100 is now non-American. Eight Indian institutions made the cut, up sharply from a decade ago. Several IITs ranked in the top 50, along with Delhi University, the University of Mumbai at 74th, and BITS Pilani.

The IITs together account for thousands of founders and billions in raised capital, with IIT Delhi leading the Indian cohort in total dollars raised — a gap that Edward attributed to sectoral differences and the impact of a few very large funding rounds.

An IIT-Madras professor and head of the Centre for Research on Start-Ups told The Hindu Business Line that the shift reflects deliberate investment in creating a supportive entrepreneurship ecosystem. Campus incubators, faculty entrepreneurship policies and returning-alumni investors have compounded over the past ten years the way Berkeley’s did over the past fifty.

The public university story

Berkeley is a public university. So is the University of Wisconsin–Madison, which jumped to sixth among American public universities in the same 2026 ranking. So are the IITs, which are federally funded institutions with heavily subsidized tuition.

The pattern matters because the popular story about tech founding usually centers on private universities — Stanford, Harvard, MIT — and expensive coding bootcamps. The PitchBook data tells a different story. Large public universities with strong technical programs and geographic access to capital produce enormous numbers of founders, at a per-dollar-of-tuition rate that private peers cannot match.

California residents pay significantly less in tuition and fees to attend Berkeley as undergraduates than students pay at private institutions like Stanford. Both schools produce startup founders. One does it at a fraction of the sticker price.

What the ten-year window captures

The ten-year window PitchBook used is a specific slice of history. It starts the year after the second wave of mobile-first consumer apps peaked. It runs through the ZIRP-era venture boom of 2020 and 2021, when U.S. venture funding hit a record high, and then through the sharp correction of 2022 and 2023, when funding fell by more than half.

Berkeley’s founders sit inside that whole arc. Some of them started companies at the peak and raised at valuations that no longer exist. Some started in the trough and are only now raising their first serious rounds. The 2,155 number includes both.

It also includes founders who took venture money for companies that are already dead. PitchBook counts the funding event, not the outcome. A startup that raised a $2 million seed round in 2018 and shut down in 2021 still counts toward its founder’s school. So the ranking measures the school’s capacity to produce fundable founders, not the school’s capacity to produce successful companies.

Those are related but different things.

What the number does not say

The ranking is silent on employees hired, revenue generated, or wealth created. It is silent on whether any of these companies produced anything socially valuable. It is silent on the founders who tried and failed to raise, and on the founders who chose not to try — the ones who took steady engineering jobs, went to graduate school, joined the government, taught high school, or built bootstrapped companies that never took outside money.

A university ranked outside the top 100 might still be producing an extraordinary number of small business owners, artists, teachers, doctors, and community builders. PitchBook does not measure any of that. It measures one specific pipeline: undergraduate to venture-backed founder.

Berkeley wins that pipeline. It has for four years.

The compounding decade

Something Rajan said at IIT-Madras hangs over the whole ranking: the ecosystem is doing the biggest thing. A student who arrives at Berkeley in the fall of 2026 walks into a campus where every dorm floor has someone whose older sibling founded a company, whose roommate is interviewing at a seed-stage startup, whose intro CS professor sold a company to Google in 2011. The environmental pressure to try is enormous.

Whether that pressure is healthy is a separate question. The PitchBook ranking simply records that when 22-year-olds leave that campus, they start companies at rates no other university on Earth matches. And ten years from now, when the 2036 ranking is released and someone tallies the founders who received their first venture check between 2025 and 2036, the Berkeley freshmen who moved into their dorms this September will be a large fraction of the count.

The next number is already being written, on Sproul Plaza and in Soda Hall and on the BART platform at Downtown Berkeley station, by students who have not yet decided what they are going to build.

The post For the fourth year in a row, UC Berkeley undergraduate alumni have founded more venture-backed companies than graduates of any other university on Earth — 2,155 startups from 2,380 founders — beating Stanford, Harvard, Cornell and MIT in the 2026 PitchBook rankings. appeared first on The Artful Parent.

The Voyagers are dying slowly, and the mission team is choosing which systems go first.

The plutonium is doing what plutonium does

Each Voyager runs on three radioisotope thermoelectric generators, or RTGs, fuelled with plutonium-238. The isotope has a half-life of about 87.7 years, and heat from its decay is converted into electricity through thermocouples. The system was built for endurance, not permanence. The generators supplied roughly 470 watts at launch and have been producing steadily less power ever since.

Four watts is not much. It is roughly the draw of a small LED nightlight. But repeated year after year on a spacecraft whose available electrical margin is already thin, those watts determine which heaters and science instruments can remain alive.

The engineers have known this constraint was coming for decades. Instruments used for the planetary encounters were retired after their work was finished, and the Voyager team has continued shutting down systems as available power declines. Years ago, the team established an order for retiring the remaining science instruments so that each shutdown could preserve the mission a little longer.

What the cosmic ray subsystem did before it stopped

The instrument switched off on 25 February 2025 had spent decades measuring high-energy particles, including galactic cosmic rays arriving from beyond the solar system. In August 2012, a sharp rise in galactic cosmic rays and a collapse in particles associated with the Sun became important evidence that Voyager 1 was crossing the heliopause. NASA’s account of the discovery makes clear that the final conclusion drew on several kinds of measurements, including later plasma-wave data, rather than the cosmic ray instrument alone.

Voyager 2’s low-energy charged particle experiment measured ions, electrons and cosmic rays across a lower-energy range. It remained productive long after the planetary encounters and continued operating until March 2025. Instruments built for a mission conceived in the 1970s had returned usable science for nearly half a century.

What is still on

After the two shutdowns in early 2025, Voyager 1 still had three operating science instruments. That changed on 17 April 2026, when engineers shut down its low-energy charged particle experiment. NASA’s current instrument-status table now lists two active instruments on Voyager 1: the magnetometer, which measures magnetic fields, and the plasma wave subsystem, which measures electron-density-related plasma waves.

Voyager 2 still has three active science instruments: its magnetometer, plasma wave subsystem and cosmic ray subsystem. The two spacecraft therefore no longer carry identical active instrument sets, but both continue returning measurements from interstellar space.

The distances involved are not really imaginable

By September 2026, Voyager 1 is about 16 billion miles from Earth and moving at roughly 38,000 miles per hour relative to the Sun. Its one-way radio time is now just under 24 hours. NASA says the spacecraft will reach 16.094 billion miles from Earth, exactly one light-day, on 18 November 2026. A command sent from Earth and the confirmation sent back therefore span nearly two days even before engineers begin interpreting the result.

Voyager 2 is more than 13 billion miles from Earth. Together, the two Voyagers are the only spacecraft ever to have operated outside the heliosphere, the protective bubble created by the Sun’s particles and magnetic field. No other operating spacecraft is returning measurements from that environment.

The antenna problem

Even the ground infrastructure can constrain what the mission team does. Deep Space Station 43, the 230-foot antenna at NASA’s Canberra Deep Space Communication Complex, is the only dish with enough signal power to send commands to the Voyagers. Beginning 4 May 2025, it entered a major upgrade period that ran into February 2026, with only limited periods of availability.

That forced the Voyager team to plan ahead. Before the long command pause, engineers tried to revive Voyager 1’s original roll thrusters, whose heaters had been considered inoperable since 2004. The backup thrusters that replaced them had developed residue buildup in their fuel tubes, raising concern that they could eventually become unusable.

The test worked. After allowing for the roughly 23-hour one-way signal time, the team saw the dormant thruster heaters begin warming within about 20 minutes of receiving the command. The hardware had been written off for more than two decades, yet it responded.

A brief history of accidental durability

The Voyagers were not originally expected to spend half a century returning data. Their planetary encounters culminated when Voyager 2 passed Neptune in 1989, after which the spacecraft continued into what became the Voyager Interstellar Mission. Their survival has depended on hardware built in the 1970s and on successive generations of engineers finding ways to stretch declining power and aging propulsion systems.

The contrast with earlier planetary missions is stark. NASA’s history of Mariner 1 records that the spacecraft lifted off from Cape Canaveral on 22 July 1962 but veered off course, forcing the range safety officer to destroy the launch vehicle 293 seconds after liftoff. Mariner 1 ended in the Atlantic. The Voyagers have now been flying for 49 years.

In April 2026, Voyager mission manager Kareem Badaruddin described the choice plainly after another instrument shutdown. NASA/JPL reported that the team remained focused on keeping both Voyagers operating for as long as possible. That is the ethic of the late Voyager mission: giving up one capability to preserve the rest.

What “Big Bang” means at JPL

In 2026, the team also tried a more ambitious power-saving procedure nicknamed “Big Bang.” Rather than retiring another science instrument, engineers reconfigured several spacecraft devices at once so lower-power hardware could take over necessary functions. On 4 August 2026, NASA reported that the procedure had successfully freed power on Voyager 2.

NASA said the change should allow Voyager 2’s three remaining science instruments to keep operating for at least an additional year without another instrument shutdown. Engineers also planned to make a similar swap on Voyager 1. The procedure does not stop the annual power decline, but it gives the team another margin to work with.

The arithmetic remains unforgiving. Radioisotope power continues to fall, and unforeseen failures can arrive before the power budget itself becomes decisive. Every successful conservation measure shifts the deadline; none removes it.

Why the losses feel personal

There is something particular about the pace of the Voyager shutdowns that makes them harder to read as pure engineering news. The spacecraft have outlived many of the people associated with their creation, including Carl Sagan, who chaired the committee that selected the contents of the Voyager Golden Record.

Suzanne Dodd has watched much of the mission’s late-life engineering from unusually close range. JPL announced her as Voyager project manager in 2010, after she had first worked on Voyager in 1984. Her tenure has covered years in which keeping the spacecraft alive increasingly meant deciding which pieces could be surrendered.

The February 2025 shutdown retired Voyager 1’s cosmic ray subsystem, one of the instruments that recorded the dramatic particle changes around the spacecraft’s 2012 passage into interstellar space. Voyager 2’s low-energy charged particle experiment was turned off for power conservation on 24 March 2025. Each shutdown removed a measurement capability that had survived since launch.

Four watts a year, and what it buys

The four-watt annual figure is an approximation used to describe the Voyagers’ continuing electrical decline. On spacecraft already operating with a narrow power margin, however, a few watts can determine whether another heater or science instrument remains available.

The February and March 2025 shutdowns were intended to give the mission roughly another year before another science instrument needed to be retired. When Voyager 1’s LECP was finally shut down in April 2026, NASA again described the move as giving the spacecraft about a year of additional breathing room. The successful Voyager 2 power reconfiguration has now added another margin without immediately sacrificing one of its three surviving science instruments.

These are small numbers against almost 16 billion miles. They are also the numbers that determine how long humanity keeps receiving direct measurements from beyond the heliosphere.

The signal is faint but still arriving

As of September 2026, both Voyagers are still transmitting. NASA notes that by the time Voyager’s radio signal reaches Earth, the power striking a Deep Space Network antenna is only about 10^-16 watts. The antennas have to pull that whisper out of the background noise and recover measurements sent by hardware nearly half a century old.

The spacecraft are still pointed well enough for their high-gain antennas to communicate with Earth. Voyager 1 has not photographed the planet since 1990, when it captured the “Pale Blue Dot” during its final imaging sequence before its cameras were switched off.

No next science-instrument shutdown has been publicly scheduled. The mission team is watching the power budget and using the extra margin created by the 2026 changes. When another shutdown eventually comes, the command will take almost a day to reach Voyager 1, and almost another day will pass before Earth can receive confirmation of what happened.

Four watts a year. A plutonium half-life measured in decades. Two probes still whispering from outside the Sun’s protective bubble, with engineers buying their remaining science one careful watt at a time.

The post On 25 February 2025, engineers at JPL switched off Voyager 1’s cosmic ray subsystem, and on 24 March they shut down Voyager 2’s low-energy charged particle instrument — small mercies bought against a plutonium supply that loses 4 watts a year on each probe. appeared first on The Artful Parent.

The research involved 148 children between the ages of 3 and 7. Using infrared eye-tracking, the researchers watched where the children looked while they decided which rotated object matched the target image, without requiring them to explain how they reached the answer.

The children identified as using the holistic approach solved the problems about twice as fast as those whose gaze patterns suggested a slower, piecemeal strategy. The result offers a more detailed look at how early some familiar forms of spatial reasoning appear.

What mental rotation actually is

Mental rotation is the ability to imagine an object changing orientation without physically moving it. You use a version of it when deciding how a jigsaw piece needs to turn, when orienting a map or when comparing two shapes shown from different angles.

Developmental psychologists study the skill partly because spatial abilities are associated with learning in mathematics, science and reading. Similar-looking letters such as b and d, for example, require children to learn that orientation can matter even when two shapes share many visual features.

That makes the question of how young children solve rotation puzzles important, not simply whether they get the answer right.

The fire truck test

The experimental set-up was deliberately simple. A child viewed a large picture of an everyday object, such as a fire truck, alongside two smaller versions positioned differently.

One small image could be rotated until it matched the large image. The other was a mirror image, meaning ordinary rotation would never make it identical.

The child’s job was to choose the matching one.

An eye-tracker mounted near the screen used infrared light to record where the child was looking during the trial. Instead of relying on a young child to describe a cognitive strategy in words, researchers could examine patterns of fixations, visits and viewing time.

Two ways to solve a puzzle

The eye-tracking analysis revealed two broad patterns.

Some children focused repeatedly on individual parts of an object. Their attention moved among features such as wheels, a ladder or the cab, and they spent more time studying details. The researchers classified this pattern as a piecemeal strategy.

Other children made fewer visits and fixations and spent less time examining individual details. Their pattern was consistent with treating the object as a single unit, the holistic strategy.

Most children in the study fell into the holistic group. That whole-object approach also appears commonly in adult mental-rotation research, although adults can use piecemeal strategies too depending on the task.

Why this changes the timeline

Researchers have long known that young children can answer mental-rotation questions. What has been less clear is what they are doing mentally when they arrive at an answer.

The FIU team, led by Karinna A. Rodriguez, found gaze patterns consistent with the same two broad strategies described in earlier mental-rotation research. Crucially, the majority of children showed the holistic pattern.

That does not mean a three-year-old performs spatial tasks with an adult’s speed, experience or accuracy. It does suggest that an important whole-object problem-solving strategy is already available much earlier than adults might assume.

For early education, that gives familiar activities a little more weight. Puzzles, blocks and tangrams are not merely preparation for spatial reasoning later on. They give children opportunities to practise spatial transformations they are already capable of attempting.

The blocks-and-puzzles evidence chain

The FIU finding fits a broader body of work connecting early spatial skills with mathematics and other areas of learning.

In a University of Delaware and Temple University study, three-year-olds were asked to reproduce six model structures using separate blocks. Children who were better at copying those block structures also tended to perform better on an early mathematics assessment.

That is an association rather than proof that one afternoon with blocks causes stronger maths ability. But it is one part of a consistent reason researchers pay attention to the spatial decisions involved in building, rotating, fitting and comparing objects.

A separate decade-long study examined whether preschool play patterns were associated with mental-rotation performance at age 13. Children classified by their parents as showing more masculine-typical play at age 3.5 scored higher on the later mental-rotation measure than children in the feminine-typical group.

The result held across boys and girls, but the researchers did not show that one style of play caused the later difference. As PsyPost’s report on the study notes, children with stronger early spatial tendencies might also have been more likely to choose spatially demanding play in the first place.

Why eyes can reveal what words cannot

Asking a four-year-old to give a precise account of how they solved a spatial puzzle has obvious limits. A child may know which truck matches without having the vocabulary to describe the sequence of mental operations behind the choice.

Eye-tracking provides another route. Researchers can measure which parts of the image attract attention, how often a child returns to them and how long those visits last.

In the FIU study, those measurements produced two distinct statistical profiles consistent with holistic and piecemeal processing. The comparison with adults comes from earlier research using similar strategy concepts, rather than from an adult control group tested alongside the children.

What this means for a Saturday afternoon

The practical takeaway is modest. Puzzles, blocks, tangrams and other spatial activities give children opportunities to turn, compare, combine and mentally reorganise shapes.

Language can be part of the same experience. Words such as above, below, edge, corner, curved, flat, upside-down and next to give children labels for relationships they are already seeing and manipulating.

A tangram is useful precisely because it can invite both kinds of attention. A child can look at the animal or house as a whole while also deciding which particular triangle or square fits one part of it.

Three-dimensional puzzles, wooden blocks, jigsaws, LEGO, magnetic tiles and pattern games create similar opportunities. None is a magic shortcut to later academic achievement; they are simply accessible ways to practise spatial reasoning.

The letter-flipping connection

The reading connection is more tentative than the spatial-puzzle finding itself.

In their public explanation of the research, Pruden and Rodriguez suggest that children who use a more piecemeal approach to mental rotation may overlap with children who have difficulty discriminating similar-looking letters such as p and q.

That remains a research possibility, not a demonstrated explanation for why a particular child reverses or confuses letters. The eye-tracking study did not establish that a piecemeal strategy causes dyslexia or other reading difficulties.

What the work does offer is a potential research direction: understanding children’s spatial strategies earlier may eventually help researchers study how those strategies relate to later reading development.

The strategy is already there. The practice sharpens it.

The most interesting part of the FIU finding is the shift in perspective. Preschool play is often described as preparation for the cognitive work that comes later, but some of that work is clearly already underway.

A three-year-old turning a wooden triangle before placing it into the right opening is using a basic spatial operation that adults rely on in far more complicated settings. The scale and expertise are different, but the need to imagine how an object changes when it turns is recognisable.

So the next time a child on the rug picks up a puzzle piece, rotates it once and settles it into the right slot, the movement is worth noticing. A small twist of the wrist can reflect a surprisingly sophisticated piece of spatial reasoning already taking shape.

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One of the more striking ideas to emerge from those experiments is that silicon and oxygen dissolved in iron may not stay dissolved forever. In a 2017 Nature study, researchers melted iron-silicon-oxygen alloy at pressures comparable with Earth’s core and found that silicon dioxide, SiO₂, could crystallize as the alloy cooled.

That does not mean scientists have watched silica crystals drifting through the real outer core. It means laboratory results established a physically plausible mechanism, and models built from those results explored what that mechanism could do to the core over geological time.

The density problem at the centre of Earth

Earth’s core is overwhelmingly iron-rich, but pure iron does not quite fit the measurements. A long-standing estimate put the outer core at roughly ten percent less dense than pure iron under comparable conditions, while more recent work has placed the shortfall closer to eight percent. C&EN’s overview of core chemistry traces that problem back to the work of geophysicist Francis Birch in the 1950s.

The missing density is one reason researchers have spent decades testing light elements such as silicon, oxygen, sulphur, carbon and hydrogen. Different mixtures affect not only density but also melting behaviour, heat transport and the convection that helps maintain Earth’s magnetic field.

The problem is that nobody can drill anywhere close to the core. The Kola Superdeep Borehole in Russia reached a little more than 12 kilometres, while the core-mantle boundary begins nearly 2,900 kilometres down. The rest has to be reconstructed indirectly.

What the diamond-anvil experiment actually showed

Diamond-anvil cells make a tiny piece of Earth’s deep interior possible on a laboratory bench. A microscopic sample is squeezed between diamond tips while lasers heat it to thousands of kelvin, allowing researchers to study matter at pressures otherwise found only deep inside planets.

Kei Hirose and colleagues used that approach on liquid Fe-Si-O alloy. Their experiments reached core pressures and revealed a broad range of compositions in which SiO₂ crystallized from the metallic liquid. The researchers then modeled what would happen as an initially hotter Fe-Si-O core cooled through time.

The important distinction is between what was observed and what was inferred. The crystals formed in the experimental samples. Their long-term behaviour inside Earth, their abundance and their contribution to core convection depend on models of the core’s composition and thermal history.

Why calling it quartz snow needs care

SiO₂ is the chemical formula of ordinary quartz, which makes “quartz snow” an appealing shorthand. But silica does not keep the familiar quartz crystal structure when subjected to the pressures of Earth’s deep interior.

A 2026 Geophysical Research Letters study of high-pressure SiO₂, for example, examined stishovite, post-stishovite and seifertite across pressures extending to 160 gigapascals. Those are very different crystal arrangements from the quartz found in a countertop or beach sand.

So the useful part of the analogy is chemical rather than mineralogical: silicon and oxygen can combine into solid SiO₂ under relevant conditions. Whether substantial amounts of that material separate from Earth’s present outer core is a different question.

The part scientists still disagree about

The 2017 result is not the last word. In 2019, a separate team tested Fe-Si-O alloys and found evidence for two immiscible iron-rich liquids rather than straightforward SiO₂ crystallization. Their PNAS study reported that the results suggested SiO₂ would not crystallize from molten Fe-Si-O at the core-mantle boundary.

That disagreement matters because the deep core cannot be sampled directly. Small differences in temperature, oxygen concentration, silicon concentration and phase behaviour can change which process a model predicts.

The safest picture is therefore not one of confirmed silica snow filling the outer core. It is a competition between experimentally motivated models for how silicon and oxygen behave in an iron-rich liquid under extraordinary conditions.

Why precipitation could matter for the magnetic field

Earth’s magnetic field is generated by motion in its electrically conducting outer core. Heat escaping from the core helps drive convection, while the freezing of the solid inner core also releases light elements into the liquid, adding compositional buoyancy.

The 2017 SiO₂ model proposed another possible source of compositional convection. If silica separates from the liquid near the top of the core, the remaining SiO₂-depleted metallic liquid changes composition and density. The study’s calculations found that the resulting buoyancy could have supplied enough energy to help power core convection and an early dynamo.

That is a model result, not a measurement of present-day silica precipitation. But it explains why a seemingly small piece of high-pressure chemistry attracted so much attention: changing which elements remain dissolved in iron changes how the entire core can move.

The outer core certainly does move on surprisingly short observable timescales. A 2026 study summarized by ScienceDaily from European Space Agency material found that a broad region of iron-rich fluid beneath the equatorial Pacific shifted from weak westward motion to strong eastward flow in 2010. The inferred eastward flow has weakened since 2020.

That flow reversal does not prove anything about silica precipitation. It does, however, underline how dynamic the liquid core is despite being hidden thousands of kilometres below the surface.

Hydrogen adds another complication

Silicon and oxygen are only part of the light-element problem. Hydrogen is especially difficult to study because it can escape from iron as experimental samples are decompressed, making recovered material a poor record of what happened under pressure.

A 2017 Nature Communications study tackled part of that problem with high-pressure, high-temperature neutron diffraction. Researchers observed hydrogen entering iron after hydrous minerals released water, supporting the idea that hydrogen could have entered metallic iron very early in Earth’s formation, before other light elements were incorporated through hotter melting processes.

More recently, researchers pushed the estimate further. A 2026 Nature Communications study combined laser-heated diamond-anvil experiments with atom probe tomography and estimated that Earth’s core could contain about 0.07 to 0.36 weight percent hydrogen.

Expressed in a more intuitive way, that is the hydrogen equivalent of roughly nine to 45 oceans of water. The researchers themselves stressed substantial uncertainties in the calculation, so 45 oceans is an upper-end estimate rather than a settled inventory.

A core that is chemically complicated

The familiar four-layer diagram of crust, mantle, liquid outer core and solid inner core is still useful. What it hides is the amount of chemistry happening inside those broad layers.

The outer core can contain several light elements at once. Their solubilities change with pressure and temperature. Some may separate into distinct liquids, some may enter solids as the inner core grows, and some may have been incorporated during the earliest stages of planetary accretion.

Even the boundary between core and mantle is not a simple smooth surface. Seismic observations reveal patches and layers with unusual velocities, but those structures have several possible origins. Partial melting, chemical reactions between core and mantle, accumulated material and changing iron-alloy chemistry can all enter the discussion.

What remains unknown

The concentration of silicon and oxygen in the core is still debated, and that uncertainty feeds directly into the silica-crystallization question. A mixture that crosses the SiO₂ saturation boundary in one model may remain stable or separate into two liquids under another set of assumptions.

The thermal history is uncertain too. How quickly the core has cooled depends on how efficiently the mantle removes heat, while the timing of inner-core growth affects how much thermal and compositional energy has been available to drive the dynamo at different stages of Earth’s history.

That is why a laboratory crystal cannot simply be scaled up into a literal description of what is falling through the core today. The experiment provides a constraint. Seismology, geomagnetism, thermodynamics and later experiments decide how much weight that constraint should carry.

A snow that may exist only under crushing pressure

The image remains extraordinary even with the uncertainty left intact. Under more than a million atmospheres of pressure, a metallic liquid containing iron, silicon and oxygen can cross a chemical boundary as it cools and produce solid SiO₂.

Whether Earth is doing that on a large scale today remains unresolved. What laboratories have already shown is almost as strange: squeeze a speck of iron alloy between diamonds, heat it to planetary temperatures, and chemistry familiar from the surface rearranges itself into forms that could help explain how Earth’s hidden metallic interior has evolved for billions of years.

The post We tend to picture Earth’s core as a solid ball of iron, but laboratory experiments squeezing molten iron, silicon and oxygen to core pressures show tiny crystals of silicon dioxide — the same chemical formula as quartz — can form as the alloy cools appeared first on The Artful Parent.

The study, later published in Infant Behavior and Development, was small. Its finding was not.

The children with sixteen toys behaved the way most parents have watched their own children behave at a birthday party or a holiday morning. They picked something up. They put it down. They picked something else up. They put that down too. Metz described the pattern to TODAY as almost frantic — a kind of shiny object syndrome in miniature, where the mere presence of another option pulled attention off whatever was already in the child’s hands.

What the room actually looked like

The setup was deliberately plain. Age-appropriate sit-and-play items — stacking blocks, a dump truck, the sort of classic toddler equipment that has barely changed in fifty years. Half the children entered a room with four of these toys arranged on the floor. The other half entered a room with sixteen. The play sessions were timed and recorded.

Metz was not measuring joy on a smile-meter. She was measuring duration of engagement with a single toy, and the variety of actions a child performed with it. A child who pushes a truck across the floor once has done one thing. A child who pushes it, loads a block into the bed, drives it under a chair, unloads the block, and then narrates the whole scene has done five.

In the four-toy room, the children did the second thing. In the sixteen-toy room, they mostly did the first, then moved on.

The Harvard toy problem

Metz has a phrase for what drives parents to fill a playroom. “We keep bringing home more and more toys, thinking this is the toy that will get my kid into Harvard,” she told the New York Post. “But then we don’t see the value in their playing because they can’t organize themselves enough to play.”

That last phrase is the mechanism. A toddler brain is still building the skill of settling — of choosing an object, staying with it, discovering what it does. Every additional toy in the room is another interruption to that process, another small pull on attention. The fifteen toys a child is not currently holding are not neutral. They are competitors.

The pattern echoes a broader idea in early-childhood research: attention fragments when competing options stay visible, and a game cannot deepen if the next distraction is already sitting on the rug.

What “twice as long” actually means

Doubling the play duration with a single toy is not a small effect. In toddler research, sustained attention on one object is one of the better early predictors of later focus, language development, and problem-solving. It is the raw material for pretend play, which itself is the raw material for narrative thinking.

When a child has time to sit with a dump truck long enough to notice that the bed tilts, that the wheels spin backwards, that a block fits inside it — that is the point at which the truck stops being an object and becomes a prop. The prop is where imagination begins.

Cut the session short by presenting a shinier option two feet away, and the truck never gets to become a prop. It stays an object. The child moves on.

Why sixteen feels generous and lands as chaos

To an adult, sixteen toys on a floor looks like abundance. To an eighteen-month-old, it looks like a decision tree with sixteen branches and no way to prune it. Executive function — the mental machinery for prioritising, sequencing, and sticking with a choice — is barely online at that age. The prefrontal cortex is still under construction and will keep building well into a person’s twenties.

Metz described what she saw in the sixteen-toy room to Motherly: children took a rapid inventory, touched things in quick succession, and never settled. “That exploration is so fast-paced,” she said, “that they don’t have time to sit and explore all the things a toy can do before they need to move on to the next one.”

The four-toy children did something different at the very start. They also took an inventory. They looked at everything. But then they had time to circle back. “They went and they looked at them all, but then they had time to go back to each toy,” Metz explained. “They sat down and they played with it for twice as long, and they did many more things with it.”

The rotation fix

The study is not an argument for throwing toys away. Metz has been careful to say so in every interview she has given about the work. Her recommendation is structural: keep whatever you own, but only let a small number be visible and reachable at any one time.

“You can have your hundreds of toys if you have a place to store them, so that when a kid has time to play there’s just a smaller number available at the moment,” Metz has explained to Motherly. The published study makes a related point, as ScienceAlert reported: rotating stored toys back into play can offer novelty without the distraction of having too many toys out at once.

The rotation trick works because novelty comes from contrast, not from quantity. A dump truck that has been in a closet for three weeks is a new dump truck when it reappears on Tuesday morning. A child who saw it every day for three weeks stopped seeing it about a week and a half in.

The apartment that made the research

Part of the reason Metz noticed this pattern at all is that she raised twins in a 1,000-square-foot Chicago apartment. There was no spare room for a toy explosion. The constraint became the observation.

“There was just no space,” she has recalled to TODAY. “My kids had everything they could want or need — and lots of these are really great therapist-approved toys — but it’s just too much. They can’t settle down and play.”

Therapist-approved does not equal helpful in bulk. The Montessori tradition has argued something similar for over a century: a limited, curated set of materials, presented one at a time, produces deeper engagement than a well-stocked toy shelf. Metz’s study put a number on the intuition.

What the four-toy children were doing

The interesting question is not why sixteen toys failed. It is what the four-toy children did with the extra minutes. They stacked. They knocked things down. They tried to fit one object inside another. They started to narrate — to themselves, to the toy, to no one in particular.

Some began early forms of pretend play, the kind child development researchers watch for because it correlates with later language and social skills. A block became food. A truck became a bed. The physical object stayed the same. The meaning shifted.

That shift takes time. It cannot happen in the eight seconds a child spends with a toy before glancing at the fifteen alternatives on the rug.

The gift-giving problem

The study has become a fixture in holiday parenting coverage for a predictable reason. Christmas mornings, birthday parties, and grandparent visits tend to produce exactly the sixteen-toy condition Metz created in the lab — often on a single afternoon. The child unwraps, plays for a minute, unwraps again, plays for a minute, and by evening is overstimulated and cranky in a room full of new things.

Parents notice the crankiness and often blame sugar, or overtiredness, or the disruption of routine. Some of that is real. But the research suggests the abundance itself is part of the problem. A brain that cannot settle cannot rest.

Metz’s suggestion in interviews with Motherly and others has been consistent: accept the gifts, then quietly store most of them. Bring them out in ones and twos over the following months. The child gets a slow parade of new things instead of a single overwhelming pile.

Where the finding fits

Metz has been careful to note the limits of her own work. The toys in her study were classic sit-and-play items — the kind that reward repeated interaction. Modern battery-powered toys with lights, sounds, and preset routines may behave differently, because the toy itself is doing more of the entertaining. The child is a passenger rather than an author.

That distinction matters. A toy that does one thing when you press one button teaches the child that toys are for pressing buttons. A wooden block teaches nothing and therefore teaches everything: it can be a tower, a car, a piece of food, a phone, a boat. The open-ended object survives the rotation. The single-purpose object gets boring quickly, no matter how many buttons it has.

The quiet room, twelve minutes in

If you have ever watched a two-year-old at a doctor’s office with a basket of three battered waiting-room toys, you have seen the four-toy finding in the wild. The child does not complain about the selection. The child sits down with a plastic giraffe and, over the course of ten minutes, gives it a personality, a voice, a small crisis, and a resolution.

Bring that same child home to a room with a full toy shelf and the giraffe never gets a name. There is always something else on the shelf, just there, waiting to be picked up and put down.

Metz’s line, delivered to reporter after reporter, has become the take-home for parents who find the research: “Recognise toys for their short-term value and then pass them on.” The dump truck is not a permanent fixture. It is a prop for a season, and the season is shorter than the packaging suggests.

In the Toledo lab, the children with four toys did not know they were part of a study. They only knew that the room was quiet, the floor was uncluttered, and the truck in front of them had not yet given up all its secrets. So they stayed. Twice as long. Which, at eighteen months old, is the closest thing to concentration a person can offer.

The post A 2017 University of Toledo study gave toddlers either sixteen toys or four in a play session, and the children with four toys played twice as long with each one, invented more uses for them, and returned to elaborate on their own ideas. appeared first on The Artful Parent.

That’s not my apology. Mine runs the other direction entirely.

I left work deliberately. After twenty years building a career — advertising, PR, training — I stepped away to be present for my children. My daughter Megan was growing fast, asking harder questions. My son Dylan, who is on the autism spectrum, needed the kind of close, consistent attention that a full schedule was making difficult to give. The decision made sense. I had the circumstances that allowed it, and I made the choice with both eyes open. I didn’t leave because I had to. I left because I thought it was the right thing to do.

What I didn’t anticipate was what would happen to me inside that choice.

It didn’t happen fast. That’s part of why it’s so hard to write about, and why it took so long to notice. There was no moment I can point to and say: that’s when I disappeared. It was more like a slow lowering of the volume. I was still physically there — making breakfast, managing the routines, doing all of it. But I was doing it from somewhere further away than I realized. Over two or three years, I became quieter. Flatter. Shorter with the kids in ways I told myself were just tiredness. Less curious about things that had nothing to do with the house. The version of me that had opinions and projects and a self that existed outside this family was not gone, exactly. She had just gone very still.

I thought this was what sacrifice looked like. I thought the self-effacement was the point.

I wasn’t depressed in a clinical sense — and if any of this sounds familiar in a way that goes beyond ordinary weariness, talking to a therapist is worth far more than anything I could offer here. But what I was experiencing was something research actually documents. A 2012 Gallup study of more than 60,000 U.S. women found that stay-at-home mothers reported more sadness, anger, and diagnosed depression than employed mothers. They also experienced fewer positive emotions day to day — less smiling, less laughing, less of the ordinary lightness that makes a person easy to be around. The conventional narrative frames the stay-at-home choice as the emotionally richer one. The data doesn’t always agree.

None of that means staying home is wrong. It means identity doesn’t politely wait on the shelf while you’re doing other things. It keeps needing to be somewhere.

Dr. Lucia Garcia-Lorenzo, a Professor of Organisational and Social Psychology at the London School of Economics, has spent years studying working mothers and the tensions embedded in the role. “If you put your identity as a mother first, then your career suffers,” she notes, “or if you focus too much on your career, then you may have to outsource care for your children. That tension is never fully resolved.” What I had done — without naming it — was decide the tension didn’t apply to me. I would choose one side entirely and the other side would quiet down.

It did quiet down. That was the problem.

The moment I understood what had happened came from Megan. She was eleven or twelve, and she told me — not to be cruel, not dramatically, just as a statement of fact the way children deliver them — that she missed going to my office and seeing me happy working. Not that she missed me when I worked. She missed seeing me happy. I didn’t say anything right away. I’m not sure I was capable of it. She had been watching the slow change across years and had found the exact words for it before I had.

What she noticed wasn’t that work had taken me away from her. What she noticed was that its absence had taken something from me, and that the smaller version of me left behind was the one she came home to every afternoon. Children have a way of measuring the people in front of them that adults underestimate. They aren’t watching our schedules. They’re watching our faces.

I went back to work. Not the same career — a different role, one I could do from home, that fit the reality of our family’s days. Work that was mine. Something I was accountable for that didn’t involve anyone’s dentist appointment or lunchbox.

The balance took time to find. But what came back — and I felt it before I had words for it — was the sense of having somewhere to return from. When work was done, I was done. I came back to the kids from a defined elsewhere rather than simply being in the house continuously, tracking everything, never fully off. The patience came back. The curiosity came back. I became warmer and more genuinely present in the hours I was with them than I had been during all the hours I was never anywhere else.

Professor Kathleen L. McGinn of Harvard Business School, whose research followed adults across dozens of countries, puts it plainly: “People still have this belief that when moms are employed, it’s somehow detrimental to their children.” Her data says otherwise. Daughters of employed mothers are more likely to work, more likely to hold supervisory roles, and earn higher wages — without evidence that their wellbeing suffers as a result. The belief that a mother’s career costs her children something essential is one the evidence keeps failing to support.

But statistics aside, what I want to say is simpler and more personal than any study: I was not a better mother for stopping. I was a more present one by hours of the day and far less present by everything that actually matters. My children didn’t need me home all the time. They needed me to be there when I was there.

So the apology I owe them — and have, in different ways, started to give — is not for the career years, the agency years, the years when I was building something that had nothing to do with them. It’s for the years I convinced myself that dissolving into full-time motherhood was the selfless choice. It felt like giving. It was, in ways I didn’t see at the time, a long slow retreat from myself. And they could tell. Megan could tell. She was waiting for me to find my way back, and she told me so, at eleven years old, in the most matter-of-fact sentence I have ever heard.

McGinn says she hopes the guilt will eventually fade: “As we gradually understand that our children aren’t suffering, I hope the guilt will go away.” I think the guilt has been pointed at the wrong thing for a long time. Working was never what I owed an apology for. The apology belongs to the years I left myself behind in a house full of people I love, and let them notice before I did.

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The numbers are specific. At 12 months, any screen exposure at all was linked to a 105% greater likelihood of “high” low-registration behaviours nearly two years later. At 18 months, every additional daily hour of TV or DVD viewing raised the odds of high sensation-avoiding and low-registration behaviours by 23%. At 24 months, each extra hour was associated with a 20% jump in the odds of high sensation-seeking, sensory sensitivity, and sensation avoiding by 33 months.

Half the children in the sample were boys. Half were girls. The researchers adjusted for prematurity, caregiver education, race and ethnicity, and how often the child played or walked outdoors with an adult. The association with screen time held.

What “atypical sensory processing” actually looks like at the kitchen table

Sensory processing is the ordinary machinery of a small body deciding what to do with a bright light, a barking dog, the tag inside a shirt, the smell of onions on a wooden spoon. Most toddlers respond in a middle band: they notice, they react in proportion, they move on.

Children outside that band respond in one of three patterns the Drexel team measured with the Infant/Toddler Sensory Profile, a parent-completed questionnaire used to assess small kids’ sensory-processing skills.

Sensation seeking. The child who has to touch every fabric in the shop, smell the crayons, press their face against the cold window, spin until they fall over. They appear to need more input than the room is giving them.

Sensation avoiding. The child who screams at teeth brushing, refuses the seam of the sock, will not enter a room with a hand dryer, tries to control the environment so that the input never arrives.

Low registration. The one that gives the study its quiet heart. A parent calls the child’s name from four feet away and the child does not turn. A dog barks and the child does not startle. The stimulus arrives, and the child is slow to notice it, or does not notice at all.

These patterns exist across the whole population of small children. What the Drexel study did was ask whether early television exposure shifted the odds of a child landing in the “high” range on any of them.

How the study was built

The team pulled data from the National Children’s Study, a federally funded cohort that recruited families between 2011 and 2014. Caregivers were asked, at the 12-month visit, whether their child watched TV or DVDs at all — a simple yes or no. At 18 and 24 months, they were asked how many hours per day, on average, over the past 30 days.

At 33 months, the same caregivers filled out the sensory profile. The researchers then looked backwards, matching earlier viewing to later behaviour.

The paper is careful about what it can and cannot show. It cannot prove that screen time causes atypical sensory processing. It can only show that the two were associated in a large US cohort after adjustment for several measured perinatal and demographic variables. Correlation, not proven mechanism.

The study also looked only at television and DVDs. Smartphones and tablets were not measured, because in 2011 the toddlers in the cohort were largely being handed remote controls, not iPads. The real 2024 exposure figure — with YouTube Kids autoplaying on a phone propped against the high chair — is almost certainly higher than what the data captured.

Why the low-registration finding is the one to sit with

Sensation seeking and sensation avoiding are legible to parents. They come with volume. Low registration is quieter and easier to miss. A child who does not turn when called can look, from across the room, like a good child. An easy child. A child absorbed.

David Bennett, the study’s senior author and a professor of psychiatry at Drexel, explained that children showing this pattern may appear less responsive to environmental changes or slower to react when called. The 105% increased likelihood at 12 months was specifically for this pattern — the child who is slower to register that the world is trying to reach them.

The temporal ordering matters here, but it does not settle direction. Screen exposure was measured first and sensory behaviour almost two years later; however, the study did not measure sensory processing at baseline. The authors explicitly note that parents may allow more screen time for children who already have challenging sensory behaviours.

Why the finding matters for autism and ADHD conversations

Atypical sensory processing is not itself a diagnosis. It is a feature that shows up in several diagnoses, most prominently autism spectrum disorder and ADHD, where it is one of the most reliably observed characteristics. Sensory sensitivities are now part of the diagnostic criteria for autism.

Heffler noted in the Drexel announcement that this association could have important implications for ADHD and autism, given that atypical sensory processing is more prevalent in these populations. She added that future research may explore whether early screen exposure contributes to the sensory brain hyperconnectivity observed in autism spectrum disorders.

The Drexel team is not claiming that television causes autism. In an interview with 6abc, Bennett stopped short of calling screen time a possible cause of autism. What the researchers are asking is whether sensory processing might be a mechanism sitting between early screen exposure and the higher rates of autism-like behaviours observed in other cohorts — a hinge, not a cause.

What screen time is displacing

A one-year-old brain is building itself out of what happens to it. The eyes track a caregiver’s face and learn that faces move in response to sounds the child makes. The hands close on a wooden spoon and learn that objects have weight, that gravity pulls, that the metal end is colder than the handle. A dog barks in the next room and the child looks up, is soothed by an adult, and learns that startling sounds resolve into safety.

An hour of animated video is not neutral in that hour. It is an hour in which the child is not turning their head toward a name, not feeling a wet washcloth on their arm, not watching a caregiver’s mouth shape the word “cup.” Some of what the study captured may be the direct effect of watching a screen. Some may be the effect of not doing the thousand other small things a toddler would otherwise be doing.

The 1,471 children in the Drexel cohort were growing up during a period of increasing screen exposure among young children.

What the American Academy of Pediatrics actually says

The AAP updated its guidance in January 2026, replacing its earlier media policies with an approach that looks beyond a single screen-time number. Its current policy says limits for toddlers and preschoolers might be less than one hour a day, while emphasizing high-quality content and protecting sleep, play, physical activity and reading. It also describes video chatting as an opportunity for back-and-forth interaction.

The gap between recommendation and reality is wide. The Drexel researchers acknowledged in interviews that many parents turn to screens out of exhaustion or a shortage of affordable alternatives. The guidance is not written to shame anyone. It is written to describe what the developing brain appears to need, which is other people.

What the researchers suggest doing

Heffler’s practical recommendation, quoted in the Earth.com coverage: for toddlers already showing atypical sensory behaviours, a period of screen-time reduction combined with sensory processing work delivered by an occupational therapist. Bennett added that parent training and education are the primary levers, especially for children younger than two.

The signs Bennett flagged for caregivers are worth naming plainly. A child who consistently does not want to be held. A child who repeatedly tries to escape noisy environments in a way that becomes stressful for the family. A child who is slow to respond to their name, slow to notice changes in the room around them. Any of these, on their own and on any given day, can be nothing. As a persistent pattern, they warrant a conversation with a paediatrician.

The evidence keeps accumulating

The Drexel paper sits inside a widening body of work. Research published in December 2025 and reported by News-Medical linked infant screen time to slower cognitive processing and higher teen anxiety scores years later. Separately, a large Japanese birth-cohort study, the Japan Environment and Children’s Study, found that among boys, longer screen time at age one was associated with a higher likelihood of an autism spectrum disorder diagnosis at age three — though the same link did not hold for girls.

No single study settles the question. Sensory processing is complicated. Screen time is a stand-in for a hundred other family variables that are hard to measure. Taken together, the evidence supports a cautious approach: minimize the extent to which passive viewing displaces sleep, play and interaction, and favor high-quality, shared media experiences when screens are used.

The children in the National Children’s Study cohort are now teenagers. The one-year-olds whose caregivers ticked “yes” to the DVD question in 2012 are, in 2026, fifteen, and researchers are still working to trace what the early association means.

The post Drexel researchers tracked 1,471 American babies and found those exposed to more television by their second birthday were more likely by 33 months to show atypical sensory behaviours — seeking intense stimulation, avoiding it, or being slow to respond when their name was called. appeared first on The Artful Parent.

The interviewer did not know which group the woman had been assigned to fourteen years earlier. That blindness is the point. These measurements are the closest thing anyone has to an experimental answer to a question that gets asserted constantly and tested almost never: does the place you live change your body?

Why the usual evidence cannot settle it

Hundreds of studies report that people in poorer, less walkable, more fast food saturated neighborhoods carry more weight. Every one of them hits the same wall. Nobody is assigned a neighborhood. People sort themselves. Someone who enjoys walking finds a walkable street. Someone with more money finds better groceries. The place and the person arrive together, and no amount of statistical adjustment fully pulls them apart.

Which is why a housing program built to study employment ended up producing the best available evidence on obesity.

The lottery

From 1994 to 1998 the US Department of Housing and Urban Development ran Moving to Opportunity in Baltimore, Boston, Chicago, Los Angeles and New York. Families with children in selected public housing, in census tracts where at least 40 percent of residents lived below the poverty line, were invited to enter a lottery for a rent voucher. About a quarter of eligible families applied. Of 5,301 volunteers, 4,498 families were randomized.

One group was offered a voucher redeemable only in a tract where fewer than 10 percent of residents were poor, plus short-term counseling on the move. A second group was offered a standard voucher with no restriction on destination and no counseling. A third was offered nothing new.

That second group is what makes the study unusual. It separates the act of moving from the act of moving somewhere less poor.

The measurements described above came an average of 12.6 years after randomization. Height and weight were taken rather than asked. Blood spots went to a certified laboratory for glycated hemoglobin, which reflects average blood sugar over the preceding months. About 84 percent of participants provided height and weight; about 71 percent provided blood.

The split result

Among women in the control group, 58.6 percent had a body mass index of 30 or more, 35.5 percent were at 35 or more, 17.7 percent at 40 or more, and 20.0 percent had a glycated hemoglobin level of 6.5 percent or higher, the American Diabetes Association’s threshold for diabetes.

The group offered the low-poverty voucher sat 4.61 percentage points lower at a BMI of 35 or more, 3.38 points lower at 40 or more, and 4.31 points lower above the diabetes threshold. In relative terms, reductions of 13.0, 19.1 and 21.6 percent.

At a BMI of 30 or more, the standard definition of obesity, there was nothing to report. The estimate was 1.19 percentage points, with a confidence interval running from minus 5.41 to plus 3.02.

The group handed an unrestricted voucher showed no significant difference from the control group on any of the four measures. That is suggestive rather than settled. The authors could not rule out that the unrestricted voucher did as much as the restricted one, and on severe obesity the unrestricted group’s own estimate fell just short of significance. But the gap between the two voucher groups on diabetes came close to significance in its own right, pointing the same way. Moving may not have been the active ingredient. Moving somewhere less poor may have been.

The caveats the authors put in writing

Jens Ludwig and his co-authors were more careful with this result than most of the coverage that followed it.

Fewer than half the families offered the low-poverty voucher, 48 percent, actually used it. The control group did not stand still either. Their average tract poverty rate fell from 53.1 percent at the start to 33.0 percent a decade later, as families moved under their own steam. The gap in neighborhood poverty between the groups was 17.1 percentage points after one year and 4.9 points after ten. The experiment was fading while it ran.

The authors tested several BMI cutoffs without adjusting for multiple comparisons, and said so, noting that their estimates on extreme obesity “may be marginally significant.” That sentence is theirs, in their discussion section. Their diabetes threshold also misses anyone whose diabetes was being successfully treated. And the baseline surveys contained almost no health information, so the study cannot say whether it prevented conditions from starting or helped existing ones ease.

They were equally plain about who was in the room. Participants volunteered. More than 90 percent of the households were headed by a black or Hispanic woman with children, and the sample was heavier than national samples. Care should be taken, they wrote, in applying the findings to populations with different characteristics.

They could not say what caused the effect either. Access to routine medical care was no different between the groups at any follow-up. What did differ was tract poverty, the share of neighbors with college degrees, and how safe and cohesive the women said their streets felt. The mechanism, they concluded, “remains unclear.”

A candidate mechanism, from a very different study

If the experiment cannot name the ingredient, a separate line of work offers one, and it is the opposite of the feature that has dominated policy.

Kristen Cooksey-Stowers, Marlene Schwartz and Kelly Brownell examined all 3,141 US counties using the 2009 USDA Food Environment Atlas. They set two ideas against each other. A food desert is an absence: the share of a county’s population that is both low income and more than a mile from a supermarket, or ten miles in rural areas. A food swamp is an excess: the ratio of fast food outlets and convenience stores to grocery stores.

The two measures turned out to be weakly and negatively correlated, meaning they describe different places. In the correlations, the food desert measure was not significantly associated with obesity. In the ordinary regressions, once food swamps were accounted for, no food desert measure survived. When the authors used an instrumental-variable approach to deal with self-selection, food deserts did come back as significant, but with an effect much smaller than food swamps.

The size of the food swamp effect depended entirely on the method. In the plain regressions it was tiny: a 1 percent increase in fast food restaurants went with roughly a 0.125 percent increase in obesity. Using highway exits per county as an instrument, the coefficients grew several times over. The authors’ own translation is that the plain estimates would imply reducing obesity by around a tenth of a percent, while the instrumented estimates imply something nearer 3 percent.

More interesting than the size is where the effect showed up. It held in counties where people were less likely to drive or use public transit to get to work, and was not significant in counties with above-average driving or transit use. The authors read this as a finding about who is stuck with their surroundings. If you can drive past the convenience store, its presence matters less.

Their limits are real and they list them. The data are a single cross-section, the obesity figures are self-reported, and the highway-exit instrument is imperfect by their own admission, with 1,672 counties having no highway exits at all. Gas stations sell convenience food and cluster near highways but were not counted. They state directly that the design “limited our ability to make causal statements.”

Adding versus subtracting

These two studies were done by different teams, in different decades, with designs that share nothing. Cooksey-Stowers and colleagues do not cite Ludwig and colleagues anywhere in their paper. They nonetheless point the same way, and they point away from the intuition that has driven most of the spending.

That intuition is additive: open a supermarket where there is none. The published abstract of a 2014 pilot study by Steven Cummins, Ellen Flint and Stephen Matthews, which followed the opening of a new supermarket in a Philadelphia food desert, reports that residents’ perceptions of food access improved while their reported fruit and vegetable intake and body mass index did not. That is the paper’s own summary.

What to take from it

None of this is advice you can act on before dinner. Nobody rezones their own street.

What it is good for is calibration, in both directions. The claim that your address determines your weight is too strong. The randomized test found nothing at all at ordinary obesity, and its authors described their severe-obesity finding as possibly marginal. The opposite claim, that body weight is purely a matter of individual willpower operating independently of surroundings, is also too strong, and the housing lottery is why. The women who received a low-poverty voucher were not given a nutrition course, a gym membership or a lecture. Something about where they ended up living did a small amount of work at the far end of the distribution over twelve years.

If there is a usable version, it is narrow, and it is about proximity rather than absence. What sits within easy reach of your door appears to matter more than what is missing from your area, and it matters most to people who cannot easily get past it. Which is a finding about streets and transport. It is not a verdict on anyone’s character, and it is not a reason to think less of your own.

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Strictly speaking, the famous calculation is the mass of the condensed water inside a representative cumulus cloud, not the mass of every molecule of air occupying the same volume. Even with that distinction, the answer is strange enough: hundreds of tons of liquid water can be spread through a cloud without crashing to the ground all at once.

The junior-high question

The story began long before LeMone became an atmospheric scientist. Mental Floss recounts that when she was in junior high, a friend’s father wondered how much a cloud weighed. She kept the question in the back of her mind for years and eventually had the knowledge to work through it.

LeMone’s scientific career focused heavily on the atmospheric boundary layer, clouds, convection and the way the lower atmosphere interacts with Earth’s surface. She also developed a long record of education and public outreach, turning atmospheric science into explanations that nonspecialists could actually use.

That communication problem appears directly in a 2011 KNKX interview, where LeMone described how difficult it can be to explain a highly technical scientific idea to someone without a scientific background.

The cloud-weight calculation is a particularly memorable example because the method is simple enough to follow. You need two approximate values: the liquid-water content of the cloud and its volume.

A marble of water in a living room

Start with water content. Scientists use about half a gram of liquid water per cubic meter as a representative value for a fair-weather cumulus. That is only a tiny amount of water inside each cubic meter of cloudy air.

Half a gram per cubic meter sounds almost weightless.

The surprise comes from the size of the cloud. LeMone’s example uses a cumulus about a kilometer across and roughly cubical. A kilometer by a kilometer by a kilometer gives a volume of one billion cubic meters. The same calculation has since appeared in science explainers describing a typical cumulus as containing roughly 500,000 kilograms of water.

Multiply half a gram by one billion cubic meters and you get 500 million grams. That is 500,000 kilograms of liquid water distributed throughout the cloud.

Why elephants

The arithmetic produces a number that is technically useful but hard to picture. Hundreds of thousands of kilograms do not give most people an immediate mental image.

Elephants do. Using an elephant weighing roughly six tons, the comparison comes out close to 100 elephants. The scale suddenly becomes visible: imagine the mass of a small herd, except divided among countless microscopic droplets across a cubic kilometer of sky.

That comparison is why the calculation has lasted. The number tells you the mass. The elephants make you feel it.

How a hundred elephants stay in the sky

If 100 elephants were somehow concentrated in one object above a field, gravity would bring them down immediately. A cloud behaves differently because its water is divided among enormous numbers of extraordinarily small droplets embedded in moving air.

The important point is not that gravity stops acting on those droplets. It does not. The droplets are simply so small that their terminal fall speeds are tiny because air resistance is large relative to their mass.

The National Weather Service explains that small cloud droplets can remain suspended for long periods, especially when they are in rising air currents. Its training material gives an average cloud-droplet terminal fall velocity of about 1.3 centimeters per second in still air.

Cumulus clouds form in rising parcels of air. Surface heating can make air buoyant, and as that air rises and cools, water vapor condenses into droplets. Continued upward motion can easily compete with the very slow settling speed of tiny cloud droplets.

So the more useful picture is not 100 elephants magically floating. It is hundreds of tons of water divided into tiny particles whose downward motion is slow enough to be offset by the moving air around them.

When the elephants come down

The suspension is temporary. Cloud droplets collide and combine, while other precipitation processes can also make particles grow. As drops become larger, their fall speeds increase until the upward air motion can no longer keep them suspended.

That is when cloud water begins reaching the ground as rain.

A large storm cloud can contain vastly more water than LeMone’s fair-weather example, and a hurricane is on another scale again. ABC News reported LeMone’s estimate of roughly 40 million elephants’ worth of water in a hurricane, using the same basic idea of estimating water content over an enormous volume.

The scale jumps from about 100 elephants in the small cumulus example to tens of millions in the hurricane estimate. At that point, elephants stop being an intuitive unit and become another very large number.

Clouds that do things nobody expected

Clouds and atmospheric plumes are not just collections of water. They can also become laboratories for chemistry that is difficult to reproduce anywhere else.

The January 2022 eruption of Hunga Tonga-Hunga Ha’apai sent material extraordinarily high into the atmosphere. In May 2026, researchers writing in Nature Communications reported unusually strong methane oxidation inside the eruption’s stratospheric plume. They estimated methane oxidation at 900 ± 220 megagrams per day and said the observations suggested at least 330 gigagrams of volcanic methane had been injected into the stratosphere.

The result was unexpected because the researchers found evidence of chlorine chemistry capable of driving methane oxidation high in the atmosphere. It is a much more precise finding than saying the plume simply removed methane from all of the surrounding air.

The atmosphere can also create extraordinary optical effects. National Geographic reported on viral 2015 footage that appeared to show a “floating city” over China. Experts quoted in the article cautioned that they could not be certain the video itself was genuine.

If the imagery was authentic, the experts said a superior mirage, potentially a Fata Morgana, could explain the effect. Layers of air at different temperatures can bend light so that distant objects appear displaced vertically, sometimes giving ships, coastlines or buildings the appearance of floating above the horizon.

The math is the easy part

LeMone’s cloud calculation is memorable partly because the final arithmetic fits comfortably on a sheet of paper. Half a gram per cubic meter multiplied by one billion cubic meters gives 500 million grams, or 500,000 kilograms.

The harder scientific work is deciding which numbers belong in the calculation in the first place. Researchers need defensible measurements of cloud water content, dimensions, temperature, motion and other properties before a simple multiplication can mean anything.

The same principle applies to weather prediction. Forecast skill has improved dramatically over decades, but no single ingredient deserves all the credit. ECMWF attributes its progress to better Earth-system models, finer resolution, improved observations, data assimilation and advances in supercomputing.

A forecast therefore rests on much more than a computer performing arithmetic. It starts with observations from satellites, aircraft, balloons, ground stations and other instruments, then depends on data assimilation and increasingly sophisticated models to turn those measurements into a picture of what the atmosphere is doing and what it may do next.

Questions that wait

Perhaps the most memorable part of LeMone’s story is still how ordinary the original question was. A friend’s father wondered aloud about the weight of a cloud when she was in junior high. LeMone remembered the question for years, then eventually found a way to answer it.

That is one of the useful things about curiosity. A question does not stop being interesting simply because the answer is not immediately available.

The next time a cumulus drifts across a summer sky, the arithmetic is there. About half a gram of liquid water per cubic meter. Roughly a billion cubic meters in the example. Around 500,000 kilograms of water.

About 100 elephants, not packed together but divided into tiny droplets moving inside rising air. Eventually some droplets grow large enough to fall. The cloud changes shape, rain reaches the ground, and an apparently weightless patch of white sky reveals just how much water it had been carrying all along.

The post Peggy LeMone started wondering how much a cloud weighs when a friend’s dad asked her in junior high, and decades later, as a researcher at the National Center for Atmospheric Research, she finally worked out the answer: about 100 elephants. appeared first on The Artful Parent.

The spacecraft themselves had launched from Earth in 1975, but their direct life-detection experiments began on Mars in 1976. NASA has sent increasingly sophisticated spacecraft back to the planet ever since, yet none has repeated Viking’s attempt to detect extant life through a dedicated biological experiment.

What the Viking landers actually did

Each Viking lander carried a robotic sampling arm and a biology package containing three experiments aimed at possible signs of life, alongside a gas chromatograph-mass spectrometer, or GCMS, that searched the soil for organic compounds.

The Labeled Release experiment, led by Gilbert Levin, added nutrients tagged with radioactive carbon-14 to Martian soil and monitored the chamber for radioactive carbon dioxide that could indicate metabolism. The Pyrolytic Release experiment approached the problem from another direction, exposing soil to carbon-containing gases and looking for incorporation of the labeled carbon into material in the sample. The Gas Exchange experiment incubated Martian soil with nutrients and watched for changes in gases above it.

The GCMS asked a related but different question: were organic molecules present in the soil at detectable levels? That distinction became crucial, because Viking’s biological experiments produced chemical responses while the GCMS did not detect the organic material scientists expected to accompany living cells.

The result nobody could settle

The most famous result came from Levin’s Labeled Release experiment. After the labeled nutrients were added, radioactive gas was released from the Martian sample. Control procedures produced differences that Levin regarded as evidence that the response was biological rather than simply chemical.

NASA did not ultimately accept that interpretation as proof of life. Its current Viking mission history describes the biology experiments as having found unexpected and enigmatic chemical activity while providing no definitive evidence for living microorganisms near either landing site.

Levin continued to argue that the Labeled Release experiment had detected microbial activity. In a 2019 Scientific American essay, he described the initial LR result as positive and maintained that the data deserved to be treated as evidence for life. That remained his interpretation, not a settled conclusion accepted by the wider Mars science community.

Nonbiological explanations remained viable, including reactive chemistry in the Martian soil. The absence of detected organics complicated the biological interpretation further. Viking therefore left researchers with something more frustrating than a clean negative result: an experiment that reacted strongly enough to remain interesting but not cleanly enough to establish what caused the reaction.

Why nothing like it has flown since

Whatever role Viking’s ambiguity played in later planning, NASA’s Mars program moved toward a different set of questions. Instead of immediately repeating a direct metabolic test, later missions concentrated on geology, water history, organic chemistry and whether ancient Mars had environments capable of supporting life.

Sojourner characterized rocks and surface conditions in 1997. Spirit and Opportunity investigated evidence that liquid water had altered Martian rocks. Curiosity established that ancient Gale Crater contained a lake environment with conditions that could have supported microbial life. Perseverance has been exploring the ancient river-delta environment in Jezero Crater while collecting and caching rock samples.

Those missions have transformed what scientists know about Mars, but their central experiments are not equivalent to Viking’s. They can investigate habitability, organic molecules, mineral chemistry and potential biosignatures without placing a fresh soil sample into a chamber and asking whether something inside it is metabolizing.

What we’ve learned about extremophiles since 1976

One of the biggest changes since Viking is the expansion of what biologists know about the environmental limits of microorganisms. Researchers now study microbial life in intensely cold, salty, acidic, dry and high-pressure environments that provide useful analogs for thinking about possible habitats beyond Earth.

Mars makes that question especially complicated because its soil contains perchlorate salts. Those compounds can be hostile to organisms at sufficiently high concentrations, yet laboratory work has shown that their presence does not automatically make microbial survival impossible. Experiments reported by Space.com, for example, found that the Arctic permafrost bacterium Planococcus halocryophilus could still grow in a solution containing ten percent perchlorate by mass.

The same work also showed why simple statements about whether a Mars-like environment is “habitable” can be misleading. Survival depended on the type of salt, its concentration and temperature, and surviving an exposure was not the same thing as actively growing in it.

None of that establishes that Mars is inhabited. It does show why a biological possibility cannot be dismissed merely because the planet’s chemistry looks punishing by ordinary human standards.

The clean room problem

Viking’s direct biological experiments came with unusually demanding contamination controls. NASA’s historical account says the landers and aeroshells were enclosed in pressurized bioshields and heat-sterilized in nitrogen at 232 degrees Fahrenheit for 40 hours. Engineers had to ensure thousands of spacecraft components could tolerate that treatment.

That mattered because a terrestrial microbe carried to the landing site could have made a positive biological result extraordinarily difficult to interpret. Planetary protection still matters on modern Mars missions, even though different spacecraft, destinations and scientific goals can require different contamination-control approaches.

The distinction should not be exaggerated into a claim that later missions have already seeded Mars with terrestrial organisms. Reporting published for Viking 1’s 50th anniversary makes the narrower point: researchers value Viking’s stringent sterilization and regard contamination from Earth microbes on more recent missions as a growing concern.

That concern becomes particularly important if a future mission returns another ambiguous biological signal. Scientists would need evidence not only that something appeared alive, but that it was genuinely Martian.

The Viking archives are still working

The landers themselves have been silent for decades. Viking 2’s final data reached Earth in 1980, while Viking 1 continued operating until 1982. The scientific argument they started has lasted much longer.

Preserving those records matters because later discoveries change the context in which old measurements are interpreted. A signal that looked unusual in 1976 can be reconsidered alongside decades of additional knowledge about Mars chemistry, microbial survival and the limits of the instruments themselves.

Later rovers have also complicated the old assumption that organic chemistry on Mars should be simple to interpret. Curiosity has detected an increasingly diverse collection of organic molecules in Martian rock, while Perseverance has examined features that researchers classify as potential biosignatures rather than proof of life. Biological and nonbiological explanations still have to be separated carefully.

That does not retroactively turn Viking’s Labeled Release result into a discovery of life. It means one of the arguments that shaped the original interpretation now sits inside a much richer picture of Martian chemistry.

What a return trip would look like

A modern attempt to detect living organisms would not need to reproduce Viking experiment for experiment. The central lesson of the last half century is that a convincing result would need multiple independent measurements capable of separating biology from unusual geochemistry, backed by strict contamination controls and detailed information about the environment surrounding the sample.

Perseverance has already cached carefully selected Martian samples in sealed tubes, preserving the possibility that some material could eventually be examined with laboratory instruments on Earth. That remains scientifically attractive, although the specific NASA-ESA campaign previously known as Mars Sample Return should no longer be described as a settled active mission. NASA now describes that campaign as a proposed plan, and a 2026 U.S. Government Accountability Office assessment reported that the program had begun closeout activities after being proposed for cancellation.

A direct life-detection lander would answer a different question. Rather than bringing ancient rocks home and examining them for traces of past environments or possible past biology, it would once again put purpose-built instruments on Mars and ask whether evidence of living processes can be detected there now.

The half-century pause

That is what makes Viking unusual even after fifty years of increasingly capable Mars exploration. Its biology package did not merely ask whether Mars once had water, whether carbon-containing molecules were present or whether a rock preserved a potentially biological pattern. It tried to provoke a measurable response from the material beneath the lander.

NASA still maintains an active Astrobiology Program, and the agency’s current life-detection work continues to examine what would count as convincing evidence for extant life. Yet NASA’s own life-detection framework says direct detection of living organisms has not been attempted since the Viking missions.

The question Viking asked therefore remains unusually direct: is anything alive here? In 1976, the answer came back ambiguous enough to sustain an argument for half a century. Mars has been photographed, drilled, driven across and analyzed repeatedly since then, but NASA has not yet put the same direct question to another fresh Martian sample.

The next attempt will have fifty years of chemistry, microbiology and planetary protection experience behind it. The last one began when Gerald Ford was still president and disco was on the radio.

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