How many planets could fit in our solar system?

The answer may surprise you ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏  ͏ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­ ­

October 16, 2026—Do birds love to fly? Plus, the seven planetary health "boundaries" we've crossed, and how to make your spooky decorations more environmentally friendly. —Andrea Gawrylewski, Chief Newsletter Editor TODAY'S NEWS Nazarii_Neshcherenskyi/Shutterstock How many planets could fit in our solar system? The answer may surprise you. | 5 min read  Here are five easy ways you can make your Halloween decorations more wildlife-friendly. | 4 min read  The math world is reeling from a barrage of AI-generated solutions. Could AI crack the algorithms underpinning cryptography next? | 4 min read This year's flu season is starting early. Here's why and what it means for your health. | 4 min read We sat down with sci-fi author Becky Chambers to discuss how she designs believable ecosystems and incorporates science in her new book As You Wake, Break the Shell. | 6 min read A Spain-based amateur astronomer used AI agents to find a previously undiscovered exoplanet lurking in publicly available data. | 3 min read TOP STORIES Galah Cockatoos. Tracielouise/Getty Images Flight Lovers Fish gotta swim and birds gotta fly. But do birds actually like it? For several months each year the pink-and-gray Galah Cockatoos at Avifauna Bird Park in the Netherlands are free to leave their aviaries every day and fly free. And they all did, without fail, for each 20-minute period offered, according to a new study. Plus, after their flight sessions, the Galahs foraged, and scratched and raised their crests more—behaviors the researchers interpreted as signs of “positive excitement resulting from free flight.” Why this matters: For these birds, flight appears to be “an ethological need”: a behavior they’re naturally driven to perform. The results are part of a broader shift in animal-welfare science away from simply preventing suffering and toward designing environments that let animals express the natural behaviors that seem to make them feel good. ​ What the experts say: Does wanting to fly and liking the experience mean the birds feel happy? Animal-cognition scientists are usually hesitant to ascribe feelings or desires based on animals’ behavior, but researchers have become increasingly open to attributing such conscious experiences to animals when the data support it. If birds are capable of conscious experience, says Michael Mendl, an animal behavior researcher at the University of Bristol in England, who was not involved in the study, “the findings would indeed suggest that the birds enjoyed flying.”

INFOGRAPHIC OF THE DAY​ A report released last month showed that we have crossed seven of the nine chemical and physical “boundaries” we need to stay within to keep the planet habitable. Those seven breached levels are at their worst recorded values since scientists first conceived of them in 2009. Each measure is compared against a preindustrial baseline, or the period before humans began burning fossil fuels in earnest—roughly the mid-19th century. Beyond each boundary is a “zone of increasing risk,” in which the odds of moving away from those preindustrial conditions rise. Amanda Montañez; Source: Planetary Health Check 2026. Planetary Boundaries Science Lab, Potsdam Institute for Climate Impact Research, 2026 (data) SCIENCE QUIZ How closely did you read Scientific American this week? Test yourself with today's science quiz. MOST POPULAR STORIES OF THE WEEK OpenAI’s blockbuster math proof isn’t what you think it is | 3 ​min read A unique shape, a 3D einstein tile, has been discovered | 5 min read Feverish after a vaccine? The reason could be your gut microbiome | 2 min read Tiny investment, enormous universe: subscribe to Scientific American for 90 days for just $1 and help keep this newsletter going. Subscribe I can understand why researchers would avoid ascribing animal behaviors to particular emotions—in fact, I support this commitment to neutrality (an important part of observational science!). At the same time, you cannot convince a pet owner that their animal does not feel joy, sadness, playfulness or love. Research has found that a pet owner can “read” a response into an animal companion’s behavior regardless of the animal’s intentions. Yet those projections serve a purpose too—they reveal our own social needs and desires. Please send your favorite pet behavior story, and any other thoughts, comments or feedback on this newsletter to: newsletters@sciam.com. Have a great weekend. —Andrea Gawrylewski, Chief Newsletter Editor

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Week in Science: 3D einstein tile discovered

Plus, more OpenAI math drama                    

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October 16—This week, more drama surrounding OpenAI’s model solving a famous conjecture. The company was accused of replicating the work of other mathematicians, but experts looking at the proof now think the model found a novel way of solving the problem altogether. Plus, a knitting stitch that stops mistakes from spreading, the discovery of a 3D einstein tile and a sobering diagnosis on Earth’s “vital signs.” Think you know science news? Take our Friday quiz to find out. —Emma Gometz, Newsletter Editor Have thoughts or feedback on our coverage? Email newsletters@sciam.com anytime.

Top Stories

OpenAI’s blockbuster math proof isn’t what you think it is Rumors that OpenAI’s “Navier-Stokes” solution stole the work of two mathematicians may have been overblown Joseph Howlett

Mathematicians invented a knitting stitch that stops mistakes from spreading With a little help from knot theory, scientists have invented a “robust knit” to fight laddering Emma Gometz

Travel with Scientific American The Secrets of the Universe and the Pleasures of the Alps Join us on this alpine adventure, led by particle physicist and Scientific American reporter Joseph Howlett. Enjoy an exclusive tour of the world’s biggest particle collider at CERN, ride cable cars through the Swiss Alps, sample world-class wines and cheeses, have one-on-one access to the foremost experts in physics, and more! Spaces are limited; book today!

A unique shape, a 3D einstein tile, has been discovered AI helped uncover a special object that can fill space without repeating patterns Rachel Crowell

Feverish after a vaccine? The reason could be your gut microbiome In a new study, people who had worse fevers after a COVID shot tended to have similar gut characteristics Jackie Flynn Mogensen

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Earth’s ‘life support systems’ are breaking down, climate scientists warn “The climate emergency is already here” Jackie Flynn Mogensen

Lettuce engineered to produce meat proteins Protein-packed leaves might be the key to better meat alternatives Lila Magbilang

An ancient Chinese math puzzle shows how to win at cards, horse races and gerrymandering A stratagem that dates back two millennia leads to a math puzzle that took 30 years to solve Dana Mackenzie

Scientists just voted to redefine how the world keeps time A new system, called the “leap hour,” will allow Earth’s rotation and official time to fall out of alignment by a full hour Emma Gometz

Meet Mark and Sam, the AI agents that ran my errands for a week Meta’s and OpenAI’s new agents can streamline your life. Artificial intelligence researchers helped me test how far to trust them Mary Randolph

Honeybees deemphasize potential ‘misinformation’ in their waggle dances Confident bees work harder to convince their peers of tasty treats Marta Hill

Do women hit a biological ‘cliff’ at menopause? Certain health markers seem to “jump” during menopause, according to a new study, but it’s unclear why Jackie Flynn Mogensen

New ‘First Proof’ exam reveals how AI-powered math is a pay-to-play sport The benchmark confirms that some AIs are becoming exceptional tools for research-level math. But open-source models still struggle Joseph Howlett

Scientists wonder: Is my AI stealing my ideas? Researchers are using AI as a sounding board throughout their work. But concerns are growing that companies may present users’ ideas as those of their models Peter Hall

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