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      Will A.I. Be a Bust? A Wall Street Skeptic Rings the Alarm.

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      Jim Covello, Goldman Sachs’s head of stock research, warned that building too much of what the world doesn’t need “typically ends badly.”As Jim Covello’s car barreled up highway 101 from San Jose to San Francisco this month, he counted the billboards about artificial intelligence. The nearly 40 signs he passed, including one that promoted something called Writer Enterprise AI and another for Speech AI, were fresh evidence, he thought, of an economic bubble.“Not that long ago, they were all crypto,” Mr. Covello said of the billboards. “And now they’re all A.I.”Mr. Covello, the head of stock research at Goldman Sachs, has become Wall Street’s leading A.I. skeptic. Three months ago, he jolted markets with a research paper that challenged whether businesses would see a sufficient return on what by some estimates could be $1 trillion in A.I. spending in the coming years. He said that generative artificial intelligence, which can summarize text and write software code, makes so many mistakes that it was questionable whether it would ever reliably solve complex problems.The Goldman paper landed days after a partner at Sequoia Capital, a venture firm, raised similar questions in a blog post about A.I. Their skepticism marked a turning point for A.I.-related stocks, leading to a reassessment of Wall Street’s hottest trade.Goldman’s basket of A.I. stocks, which is managed by a separate arm of the firm and includes Nvidia, Microsoft, Apple, Alphabet, Amazon, Meta and Oracle, has declined 7 percent from its peak on July 10, as investors and business leaders debate whether A.I. can justify its staggering costs.The pause has come early in the A.I. arms race. The tech industry has a history of spending big to deliver technology transitions, as it did during the personal computer and internet revolutions. Those build outs spanned five years or more before there was a reckoning.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Michel Siffre, 85, Dies; Descended Into Caves to Study the Human Mind

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      He was a pioneer in chronobiology, the study of how our bodies understand the passage of time.On the morning of Sept. 14, 1962, reporters and onlookers began to gather around a hole in the ground, far up in the Maritime Alps between France and Italy. A few hours later, workers rigged a rope down into the darkness; soon they pulled out a small, sturdily built man named Michel Siffre.He had been inside the cave, 375 feet down, for 63 days, with only a four-volt lamp for illumination. He wore dark goggles to limit the glare of the sun, and he had to be carried to a waiting helicopter.This was no rescue: Mr. Siffre, a geologist, was conducting an experiment on himself, to see what would happen to his sense of time if he cut himself off from the normal day-night flow of life on the surface.It turns out that a lot could happen: Time as he experienced had “telescoped,” he said. His circadian rhythm of wakefulness and sleep stretched from 24 to about 25 hours. And what felt to him like one month was in fact two on the surface.“After one or two days, you don’t remember what you have done a day or two before,” he told Cabinet, an art and culture magazine, in 2008. “The only things that change are when you wake up and when you go to bed. Besides that, it’s entirely black. It’s like one long day.”Mr. Siffre, who died on Aug. 25 in Nice, was a leading figure in the field of chronobiology, the study of how the human body understands time. Previous scientists had speculated that, contrary to the prevailing idea at the time, our internal clocks are independent of the solar cycle, even as we usually adjust to its influence. Through decades of experiments beginning with that 1962 descent, he proved it.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      There Might Be More Than One Way to Make a Planet

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      Astronomers have found evidence of a process that supports an alternative, more rapid approach to planetary formation, more top down than bottom up.When it comes to making a planet, astronomers have long subscribed to what Cassandra Hall, an astronomer at the University of Georgia’s Center for Simulational Physics, refers to as the “bottom up” approach: The gas and dust swirling around a young star slowly clumps together over millions of years, and its gravity shapes it into a rounded object.But a discovery by Dr. Hall and her colleagues, published in the journal Nature this month, suggests that the picture might be more complex.In a star system 508 light-years from Earth, the researchers found conditions that support an alternative “top down” approach to planet formation, in which the fertile material circling a young star rapidly collapses into a planet. The mechanism, known as gravitational instability, could explain the existence of mysterious, massive worlds known to follow wide orbits around relatively young stars.“There’s never been real, hard evidence of it happening before,” Dr. Hall wrote in an email. “We found it!”The cosmic matter stirring around an infant star is ripe with planet-forming potential. The matter is known as a protoplanetary disk, and its rotation is generally driven by the gravity of its host star. But if that disk gets large enough, it can be influenced by its own gravity, causing the young star system to become unstable. Regions of higher density in the disk emerge in the form of spiral arms, similar to the shape of spinning clouds in a hurricane.“The star would be like the eye of the storm,” said Jess Speedie, a graduate student at the University of Victoria in Canada who led the study under the supervision of Ruobing Dong, an astrophysicist.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      How Does Pregnancy Change the Brain? Clues Are Emerging.

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      As hormones surge, some brain areas shrink in what scientists say may be a fine-tuning that helps mothers bond with and care for their babies.Research is revealing intriguing clues about how pregnancy changes the brain. Studies scanning women’s brains before and after pregnancy have found that certain brain networks, especially those involved in social and emotional processing, shrink during pregnancy, possibly undergoing a fine-tuning process in preparation for parenting. Such changes correspond with surges in pregnancy hormones, especially estrogen, and some last at least two years after childbirth, researchers have found.A new study, published Monday in the journal Nature Neuroscience, adds to the picture by documenting with M.R.I.s brain changes throughout one woman’s pregnancy. It confirms previous results and adds detail, including that white matter fibers showed greater ability to efficiently transmit signals between brain cells, a change that evaporated once the baby was born.“What’s very interesting about this current study is that it provides such a detailed mapping,” said Elseline Hoekzema, a neuroscientist who heads the Pregnancy and the Brain Lab at Amsterdam University Medical Center and has helped lead studies analyzing brain scans of more than 100 women before and after pregnancy.Dr. Hoekzema, who was not involved in the new study, said it showed that along with previously documented “longer-lasting changes in brain structure and function, more subtle, transient changes also occur.”Dr. Ronald Dahl, director of the Institute of Human Development at the University of California, Berkeley, who was not involved in the new study, said the emerging research reflected the key role of hormones in transitions like puberty and pregnancy, guiding neurological shifts in priorities and motivations.“There is that sense that it’s affecting so many of these systems,” he said. The study participant, Elizabeth Chrastil, is a neuroscientist at the University of California, Irvine. She became pregnant in 2019, at 38, after in vitro fertilization. That allowed precise tracking of her pregnancy from the start.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Pollution May Affect the Color of City Birds, Research Shows

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      Recent studies show that certain feather pigments can help neutralize toxic pollution. It means darker, duller birds could have a survival advantage.Some popular city dwellers appear to be losing their colorful allure, and not just the dirty birds.According to a study published this summer in the journal Landscape and Planning that looked at 547 bird species in China, birds that live in cities are duller and darker on average than their rural counterparts. A similar conclusion emerged from an analysis of 59 studies published in March in Biological Reviews: Urban feathers are not as bright, with yellow, orange and red feathers affected most.Often, city birds are covered in grime. But even if you could give them all a good bird bath, chances are their brightness still wouldn’t match that of their country cousins. That’s because of the way pollution, and heavy metals in particular, can interact with melanin, a pigment that makes feathers black, brown and gray.Studies show that melanin can bind to heavy metals like lead. That means toxic chemicals may be more likely to be stored in plumage in darker and duller birds. And that, in turn, can confer a survival advantage.“The more melanin you accumulate, the better able you are to sequester these harmful compounds in feathers,” said Kevin McGraw, a biologist at Michigan State University who studies the colors of animals to understand the costs, benefits and evolution of visual signals.Urban pollution affects avian colors in other ways, too. Research shows that compared with rural plants, city trees store fewer natural pigments called carotenoids, and pollution is the likely reason. Carotenoids are produced by plants, algae and fungi. They’re what makes red peppers red and carrots orange.When leaves are low on these pigments, the effects go up the food chain: Leaf-munching caterpillars become deficient in carotenoids, and so do caterpillar-munching birds.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Time to Say Goodbye to the B.M.I.?

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      The body mass index has long been criticized as a flawed indicator of health. A replacement has been gaining support: the body roundness index.Move over, body mass index. Make room for roundness — to be precise, the body roundness index.The body mass index, or B.M.I., is a ratio of height to weight that has long been used as a medical screening tool. It is one of the most widely used health metrics but also one of the most reviled, because it is used to label people overweight, obese or extremely obese.The classifications have been questioned by athletes like the American Olympic rugby player Ilona Maher, whose B.M.I. of 30 technically puts her on the cusp of obesity. “But alas,” she said on Instagram, addressing online trolls who tried to shame her about her weight, “I’m going to the Olympics and you’re not.”Advocates for overweight individuals and people of color note that the formula was developed nearly 200 years ago and based exclusively on data from men, most of them white, and that it was never intended for medical screening. Even physicians have weighed in on the shortcomings of B.M.I. The American Medical Association warned last year that B.M.I. is an imperfect metric that doesn’t account for racial, ethnic, age, sex and gender diversity. It can’t differentiate between individuals who carry a lot of muscle and those with fat in all the wrong places.“Based on B.M.I., Arnold Schwarzenegger when he was a bodybuilder would have been categorized as obese and needing to lose weight,” said Dr. Wajahat Mehal, director of the Metabolic Health and Weight Loss Program at Yale University.“But as soon as you measured his waist, you’d see, ‘Oh, it’s 32 inches.’”So welcome a new metric: the body roundness index. B.R.I. is just what it sounds like — a measure of how round or circlelike you are, using a formula that takes into account height and waist, but not weight.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Are Some Ultraprocessed Foods Worse Than Others?

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      A new study may offer the biggest clues yet.Name a common condition — heart disease, Type 2 diabetes, cancer, dementia, irritable bowel syndrome — and chances are good that following a diet high in ultraprocessed foods has been linked to it.But the ultraprocessed food category is large and wide-ranging. It makes up an estimated 73 percent of the U.S. food supply, and contains stereotypically “unhealthy” products like sodas, candies and hot dogs as well as seemingly “healthy” ones like whole grain breads, breakfast cereals, flavored yogurts and plant milks.It’s a “hodgepodge of foods,” some of which are likely more harmful than others, said Josiemer Mattei, an associate professor of nutrition at the Harvard T.H. Chan School of Public Health.On Monday, Dr. Mattei and her colleagues published one of the largest and longest studies on ultraprocessed foods and heart health to date. In it, they analyzed the risks of consuming these foods, and teased out the worst offenders.An Overall Risk of Ultraprocessed FoodsThe new study, published in a Lancet journal, included more than 200,000 adults in the United States. They filled out detailed diet questionnaires beginning in the 1980s and early 1990s, and completed them again every two to four years for about 30 years. Most of the participants in the study were white and worked as health professionals. The researchers looked at how the participants’ ultraprocessed food consumption related to their chances of developing cardiovascular disease.After adjusting for risk factors like smoking, family health history, sleep and exercise, the researchers found that those who consumed the most ultraprocessed foods were 11 percent more likely to develop cardiovascular disease and 16 percent more likely to develop coronary heart disease during the study period, compared with those who consumed the least ultraprocessed foods. The highest consumers also had a slightly, but not significantly, elevated risk of stroke.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More

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      Eliyahu Rips, Who Claimed to Find Secret Codes in the Torah, Dies at 75

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      His work provided the basis for the worldwide best seller “The Bible Code,” but he later rejected the book as unscientific.It sounds like a headline ripped from a supermarket tabloid: In 1994, three Israeli researchers claimed to have found a secret code embedded in Genesis, the first book of the Old Testament.But this wasn’t junk science. The paper in which they revealed their findings appeared in an esteemed, peer-reviewed journal. And the academic reputations of the three authors — Eliyahu Rips, Yoav Rosenberg and Doron Witztum — were unimpeachable, especially that of Dr. Rips.A math prodigy born to Holocaust survivors in Latvia, he had received his doctorate from, and spent his career at, Hebrew University in Jerusalem, where he became known for his work in a field called geometric group theory.He had also become convinced that statistical tools and newer, more powerful computers that were becoming available in the 1980s could be used to identify hidden meaning within the Bible, and he teamed up with his two partners to discover them. Their biggest finding was the names of 32 Jewish scholars in the text, along with their birth or death dates; several of the scholars had lived thousands of years after Genesis was written.Their results, reported in the journal Statistical Science, set off a tempest in the worlds of biblical scholarship and statistical analysis. In 1997, Michael Drosnin, a journalist, used the team’s tools to write “The Bible Code,” a global best seller that claimed to find not just rabbis’ birthdays but also predictions about world events, including the assassination of Israeli Prime Minister Yitzhak Rabin in 1995, all embedded in the Torah, or the first five books of the Old Testament. (Mr. Drosnin died in 2020.)The book put Dr. Rips in an international spotlight. Magazine and newspaper profiles proliferated; with his Gandalfian white beard and wide-brimmed hat, he seemed to embody the intersection of science and Jewish mysticism.We are having trouble retrieving the article content.Please enable JavaScript in your browser settings.Thank you for your patience while we verify access. If you are in Reader mode please exit and log into your Times account, or subscribe for all of The Times.Thank you for your patience while we verify access.Already a subscriber? Log in.Want all of The Times? Subscribe. More