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Today in Science:  “Some metals can heal their own cracks.”

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September 26, 2023: Some metals can heal their own cracks, how bats won the genetic lottery and astronomers grieve the brightening sky.
Andrea Gawrylewski, Chief Newsletter Editor

Totally Metal

For the first time, scientists have observed solid metal mending its own cracks without human intervention, defying fundamental theories of materials science. Researchers were studying how cracks spread across nanoscale pieces of platinum in a vacuum, prodding the metal 200 times per second to watch how fractures spider-webbed across the surface. After 40 minutes, to the surprise of the scientists, the damage started to disappear as the fissures fused back together.
How it works: The self-healing ability appears to arise when the edges of a crack are pressed close enough together for their respective atoms to bond. In certain “sweet spot” areas, irregularities in a metal’s neat, crystalline structure shift when external tension—such as the force exerted by natural wear and tear—is applied. As these irregularities move, they induce a compressive stress that triggers the rebonding effect.
What the experts say: The self-healing effect has been replicated in both copper and platinum, though not yet in steel. The phenomenon is causing materials scientists to rethink what they know about metal. “Under the right circumstances,” says Michael Demkowicz, a materials scientist at Texas A&M University, who co-led the new study, “materials can do things we never expected.”

Bats’ Advantage

A chance mutation might have been the key that opened the sky to bats. A mutation in a particular gene called Ripk4 may have enabled the skin layers between their body and limbs to fuse together to form the flight membrane. Researchers found that the membrane, called the plagiopatagium, grows from the side of the fetus’s body and merges with its limbs. This pattern held across all the species the researchers studied, indicating that this type of wing formation evolved a single time for all bat species.
Why this is cool: In humans and laboratory mice, mutations to Ripk4 can alter the skin to create webbed structures like feet and cleft lips, among other issues. But about half of all living bat species have cleft palates—a feature that may be tied to bat echolocation.
What the experts say: “The bat wing is a crazy amalgam of derived and novel anatomical elements,” says study author Karen Sears, a biologist at the University of California, Los Angeles. “Evolution is unpredictable, and development is often modified in ways that we cannot, or do not, anticipate,” she says.
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More News
• Anti-government rhetoric sows public distrust, write Marek N. Posard and Caitlin McCulloch, both scientists at the RAND Corporation. Conspiracy theories of governmental cover-ups will particularly damage research into unidentified anomalous phenomena (a new term for UFOs), they say. “If UAP information gets caught up in debates over antigovernment conspiracies, that’ll put the entire area of research—and the movement to make data more transparent—at risk.”  | 5 min read
Pilots look at an image of the first “flying saucer” reportedly sighted in 1947. Credit: Bettman/Getty Images
More Opinion
According to a recent study, the astronomical observatory least contaminated by light pollution is a lodge in Namibia that hosts several telescopes rented to amateur astronomers. Two thirds of all major observatories have seen a 10 percent increase in sky radiance over natural levels (read more details in this study). It’s shocking how bright we humans are making our skies.
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—Andrea Gawrylewski, Chief Newsletter Editor
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