Science
Scientists Detect Shape-Shifting Along Earth’s Solid Inner Core
The inner core at the center of the Earth, a ball of iron and nickel about 1,500 miles wide, may not be perfectly solid.
A new study finds evidence that the inner core’s outer boundary has noticeably changed shape over the past few decades.
“The most likely thing is the outer core is kind of tugging on the inner core and making it move a little bit,” said John Vidale, a professor of earth sciences at the University of Southern California.
Dr. Vidale and his colleagues reported their findings on Monday in the journal Nature Geoscience.
That adds to the mysteries about the planet’s center. Geophysicists have previously reported that the inner core does not spin at exactly the same rate as the rest of Earth. They also showed that the pace of rotation changes — the inner core appeared to be spinning slightly faster than the outer layers a couple of decades ago, and now it is spinning slightly slower.
The inner core is the deepest of Earth’s geological layers. The crust — the layer that we live on — is just a few miles thick. Below that, filling up 84 percent of the planet, is the 1,800-mile-thick mantle, which is soft enough in places to flow up and down and generate the forces that push the continents around. Between the mantle and the inner core is the liquid outer core.
Scientists of course cannot cut into Earth and directly observe its insides. Instead, their knowledge is inferred from the vibrations generated by earthquakes that pass through the planet. The speed and the direction of the seismic vibrations change depending on the density and the elasticity of the rocks.
For this study, Dr. Vidale and his colleagues looked at earthquakes in the South Sandwich Islands, a volcanic chain in the South Atlantic Ocean.
So many earthquakes happen there that sometimes a new event is almost identical in magnitude and location to one that occurred years earlier.
The scientists identified more than 100 such “earthquake pairs,” analyzing readings from 1991 to 2004 at two arrays of seismometers more than 8,000 miles away from the islands, one near Fairbanks, Alaska, the other in Yellowknife, Canada.
The analysis originally aimed to improve on earlier work that suggested a slowing of the inner core’s spin. But the scientists did not understand aspects of the signals at the Yellowknife array.
“Basically, the wiggles are different,” Dr. Vidale said.
By coincidence, for some of the pairs, the inner core was in the same orientation during both quakes.
Identical earthquake vibrations passing through the identical part of the Earth should have produced identical seismic signals at Fairbanks and Yellowknife. At Fairbanks, that was true, but at Yellowknife the signals were different.
Because Yellowknife is somewhat closer to the South Sandwich Islands than Fairbanks is, the seismic waves from the islands’ earthquakes did not travel as deeply into the inner core as those reaching Fairbanks. That suggested something had changed near the outer boundary of the inner core.
Turbulent flow in the outer core or gravitational pull from denser parts of the mantle could have deformed the inner core boundary, which might account for the change in the seismic signals, Dr. Vidale said.
“We expect it’s soft because it’s near melting point,” he said. “So it’s no surprise if it deforms.”
The new findings will not be the last on the subject. “The offered interpretation is sound,” said Hrvoje Tkalcic, a professor of geophysics at the Australian National University who was not involved with the research, “although it is not the only possible explanation, as the authors acknowledge.”
In recent years, geophysicists have argued over whether differences in the seismic signals are caused by a change in the rotation rate or by a change in the shape of the inner core. “This study thus reconciles the last debate by proposing a combination of both causes,” Dr. Tkalcic said.
Lianxing Wen, a professor of geosciences at Stony Brook University in New York who in 2006 reported possible changes of shape at the inner-core boundary, remains unconvinced that the inner core spins at a rate different from that of the rest of Earth.
Dr. Wen said the Yellowknife data was inconsistent with that hypothesis. “Ordinarily, such inconsistencies should lead to an abandonment of the original inconsistent interpretation,” he said.
A change in shape, without any change in the rotation rate, was enough to explain the seismic data, Dr. Wen said.
Even Dr. Vidale is not completely convinced he is correct. “We’re pretty sure we were right, but this isn’t a bulletproof paper,” he said. “How sure? I sort of put it at 90 percent.”
Dr. Tkalcic said more data was needed to resolve the question, which “can be achieved by building seismological infrastructure in remote areas of the planet, including the ocean floor.”
Xiaodong Song, a professor at Peking University in China who in the mid-1990s was one of the first to propose that the inner core was spinning at a different speed from that of the Earth’s surface, agreed.
“This new study,” Dr. Song said, “should motivate a new round of exploration into strange behaviors at the heart of the planet.”
Science
Amid E. coli outbreak, California-based Raw Farm voluntarily recalls cheddar cheese
Yes, Mark McAfee is pulling his cheese.
No, he is not happy about it.
The U.S. Food and Drug Administration asked McAfee’s Fresno-based Raw Farm weeks ago to voluntarily withdraw its unpasteurized cheese products from the market as the agency investigates an E. coli outbreak that has sickened nine people in three states — seven of them in California.
The U.S. Centers for Disease Control and Prevention has warned the public not to buy, sell or serve the company’s raw cheddar cheese, which five of those who had an E. coli infection say they ate before their illness.
For three weeks, McAfee refused to abide by the government’s wishes. But on Friday he finally relented, saying he has “involuntarily” recalled seven batches of cheese, even though the FDA has yet to confirm that E. coli has been found in any Raw Farm products. The agency has not issued a formal recall, though it has sent out a warning letter telling customers to avoid Raw Farm products purchased on or after Jan. 4, particularly raw milk cheddar cheese.
“This Voluntary Recall is being performed under protest,” the company wrote in an announcement posted Friday by the FDA. “This Voluntary Recall is performed as a path forward.”
McAfee said he tests every batch of milk that comes out of his milking parlors, and none has been positive for E. coli, salmonella, campylobacter, listeria or any other contaminant that causes human illness. He has shared those results with both the FDA and state regulators, he said.
He said the agency came to his farm and “spent nearly a week” reviewing his tests.
“They were very impressed,” he said.
“There’s no pathogenic bacteria correlating us to anybody,” said McAfee. “What they did was a backdoor move. They said, ‘We’ll just let everybody know we’re concerned,’ and that is enough to have stores kick you out.”
The FDA has not yet responded to requests for comment.
Last month, the FDA and CDC announced an investigation into an E. coli outbreak that since September has sickened nine people in California, Florida and Texas, three of whom have been hospitalized. More than half the cases are children aged 5 or younger. One patient required treatment for hemolytic uremic syndrome, a serious kidney complication.
Genome sequencing of E. coli isolated from each patient found that the strains were closely genetically related, suggesting that all of the ill people were exposed to the same source of infection.
State and local public health officials were able to interview eight patients or their caregivers. All said they’d consumed raw dairy products before falling ill. Two whose illness started in late 2025 said they drank Raw Farm’s raw milk, and five who fell sick in 2026 had eaten the company’s raw cheddar. (The eighth couldn’t recall the brand of the raw milk they drank.)
While testing of retail samples of Raw Farm cheese on sale in March found no E. coli, California has not ruled out the farm as the outbreak’s source given the number of patients who consumed its products before infection, a California Department of Public Health spokesperson said.
“Retail cheese samples collected do not represent all raw cheese products sold by Raw Farm and may have been from different lots of production than those consumed by ill persons,” the agency said in a statement. “CDPH considers Raw Farm raw dairy the source of the outbreak based on this strong epidemiologic data, despite the negative laboratory testing results from a limited sample of retail products.”
Raw, or unpasteurized, dairy has not undergone the heating process that kills harmful bacteria while leaving nutrients largely intact. Raw Farm’s products alone have been associated with at least 239 reported cases of food poisoning since 2006, including a salmonella outbreak in October 2024 that sickened 171 people, according to Bill Marler, a food safety lawyer with Seattle-based MarlerClark.
He said the FDA’s decision to send out a warning letter instead of issuing a recall is “completely normal,” and the agency is very conservative when it comes to food safety.
“It makes sense, under the circumstances, to pull the product from the shelves,” he said of grocery stores. “Hell, if I was a retailer, I would pull it, because the last thing you’d want to do is have the product on the shelf, have it test positive for some E. coli, and have it poison some little kid and who then gets kidney failure.”
Proponents of raw dairy have long insisted that it prevents allergies and promotes beneficial bacteria, claims that are not supported by research. They include U.S. Health and Human Services Secretary Robert F. Kennedy Jr., a longtime fan who celebrated the release of the 2025 “MAHA Report” with a shot of raw milk.
McAfee was among those hopeful that Kennedy’s tenure would usher in a more favorable regulatory environment for raw dairy producers. But despite having been contacted by Kennedy surrogates before Trump’s second inauguration, he’s not heard from them since.
He said the administration has done little to promote raw dairy as part of a revamped food policy that emphasizes meat and whole-fat milk as essential for a healthy diet.
The FDA’s webpage about raw dairy was last updated during the Biden administration, and cautions people to avoid raw milk products and dispels research claiming it is healthy.
“They fired their best people at FDA and hired some good people and weird people and whatever,” McAfee said. “It’s so emblematic of a three-ring circus. The entire freaking administration is showing that through their lack of consistency, the lack of policy adherence, they just do what the hell they want to do.”
What has changed under the new administration is the FDA’s ability to carry out investigations like the one it says it has initiated at Raw Farm. Inspections, lab work and outbreak investigations are among the agency functions most hindered by significant staff reductions that have taken place since Trump took office, industry experts have warned.
The Department of Health and Human Services has lost 18,200 employees since Trump took office, according to the Department of Personnel Management’s Federal Workforce Data tool. More than 3,000 of those losses were at the CDC, and about 4,500 were at the FDA.
Science
Diablo Canyon nuclear power plant gets final go-ahead to run through 2030
The federal Nuclear Regulatory Commission on Thursday renewed Diablo Canyon’s license to operate, ensuring that California’s last remaining nuclear facility will continue to run through at least 2030.
The plant was originally slated to close in 2025, but lawmakers extended the deadline by five years in 2022, citing ongoing need for power from a plant that provides more than 8% of the state’s electricity.
The approval from the body that regulates nuclear reactors and waste marks the final hurdle in Pacific Gas & Electric’s multiyear journey to gather the necessary state and federal permits to keep its facility online.
In December, PG&E received a key permit from the California Coastal Commission by agreeing to give up 12,000 acres of nearby land for conservation in exchange for the loss of marine life caused by the plant’s operations.
Another key step took place in February when the Central Coast Regional Water Board approved waste discharge permits for the plant and granted a certification under the Clean Water Act, the last step required before the Nuclear Regulatory Commission could issue its final approval.
The license renewal from the commission allows the plant to remain running for 20 years, although extending it past 2030 would require additional action from the California Legislature.
“Today’s milestone reminds us that when discipline, science, responsibility and vision all come together, we can build an energy future that is both sustainable and secure,” said NRC Office of Nuclear Reactor Regulation acting Director Jeremy Groom at a signing ceremony.
Already this year some lawmakers and regulators have expressed interest in extending the plant’s life through 2045, citing growing electricity demand and the plant’s central role in helping the state meet its climate goals by providing carbon-free power to the grid.
Groups that oppose the plant want to make sure that doesn’t happen. Last week, the California Coastkeeper Alliance filed a petition asking the State Water Resources Control Board to throw out the facility’s water discharge permit. The group alleged that the Central Coast Regional Water Board illegally allowed the facility to continue operating without technology required under the federal Clean Water Act to protect marine life.
Other groups have petitioned the board to limit Diablo Canyon’s Clean Water Act certificate to 2030, rather than 2045.
Science
Video: How the Artemis Astronauts Plan to Live in Space for 10 Days
new video loaded: How the Artemis Astronauts Plan to Live in Space for 10 Days
transcript
transcript
How the Artemis Astronauts Plan to Live in Space for 10 Days
On the Artemis II mission, four astronauts will work, exercise and sleep in a capsule that is about the size of two minivans for 10 days. In April 2025, National Geographic worked with NASA to film the astronauts at an Orion space capsule model in Houston.
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“Did y’all really get dibs on spots?” “She thinks.” “I know.” “Shotgun.” “Yeah, I basically called shotgun.” “We’re thinking maybe one of the sleeping bags will be kind of laid out, like, around this bend right here. So somebody’s going to have a head maybe over here, and then the feet all the way down there by the ECLSS wall.” “And Dre, don’t forget that I’ve already claimed the tunnel here. Except you’re not supposed to sleep with your head in there because of carbon dioxide. So I’m going to be hanging like a bat, is my plan. But I won’t even know it because there’s no gravity.” “Here, we’ve got both the toilet area and the exercise device on Orion. So this is the flywheel exercise device. We’ll start here. The toilet is right below it. So underneath me right now is the hygiene bay. And then it kind of looks like a rower. So you have a strap here and a hand-held bar or a harness, depending on what type of exercise you’re doing, and the way you use it is actually in this direction. So this is one of the things that we have to think in a 0g environment for, that the person who’s exercising on this will have their head coming up in the direction of the docking tunnel. And if you’re a really tall person — let’s say, the largest Canadian that we have — and you’re assigned to this mission, your head is going to extend all the way toward the docking hatch.” “That space is going to feel bigger on orbit when we’re floating. And then going up to the, again, the forward portion is what’s up now. But going forward and looking down to the deck, while this may be an awkward space to talk about here on Earth, where we have the normal pull of gravity, when we get into weightlessness, those two walls are going to be spaces that we work in, and that we use more than we do here when we’re on Earth.”

By Jamie Leventhal
April 2, 2026
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