上海后花园419

LOS ANGELES ­— Insights into a black hole paradox may come from a down-to-Earth source.

Superconductors, materials through which electrons can move freely without resistance, may share some of the physics of black holes, physicist Sreenath Kizhakkumpurath Manikandan of the University of Rochester in New York reported March 7 at a meeting of the American Physical Society. The analogy between the two objects could help scientists understand what happens to information that gets swallowed up in a black hole’s abyss.
When a black hole gobbles up particles, information about the particles’ properties is seemingly trapped inside. According to quantum mechanics, such information cannot be destroyed. Physicist Stephen Hawking determined in 1974 that black holes slowly evaporate over time, emitting what’s known as Hawking radiation before eventually disappearing. That fact implies a conundrum known as the black hole information paradox (SN: 5/31/14, p. 16): When the black hole evaporates, where does the information go?

One possible solution, proposed in 2007 by physicists Patrick Hayden of Stanford University and John Preskill of Caltech, is that the black hole could act like a mirror, with information about infalling particles being reflected outward, imprinted in the Hawking radiation. Now, Manikandan and physicist Andrew Jordan, also of the University of Rochester, report that a process that occurs at the interface between a metal and a superconductor is analogous to the proposed black hole mirror.

The effect, known as Andreev reflection, occurs when electrons traveling through a metal meet a superconductor. The incoming electron carries a quantum property known as spin, similar to the spinning of a top. The direction of that spin is a kind of quantum information. When the incoming electron meets the superconductor, it pairs up with another electron in the material to form a duo known as a Cooper pair. Those pairings allow electrons to glide easily through the material, facilitating its superconductivity. As the original electron picks up its partner, it also leaves behind a sort of electron alter ego reflecting its information back into the metal. That reflected entity is referred to as a “hole,” a disturbance in a material that occurs when an electron is missing. That hole moves through the metal as if it were a particle, carrying the information contained in the original particle’s spin.

Likewise, if black holes act like information mirrors, as Hayden and Preskill suggested, a particle falling into a black hole would be followed by an antiparticle coming out — a partner with the opposite electric charge — which would carry the information contained in the spin of the original particle. Manikandan and Jordan showed that the two processes were mathematically equivalent.
It’s still not clear whether the black hole mirror is the correct solution to the paradox, but the analogy suggests experiments with superconductors could clarify what happens to the information, Jordan says. “That’s something you can’t ever do with black holes: You can’t do those detailed experiments because they’re off in the middle of some galaxy somewhere.”

The theory is “intriguing,” says physicist Justin Dressel of Chapman University in Orange, Calif. Such comparisons are useful in allowing scientists to take insights from one area and apply them elsewhere. But additional work is necessary to determine how strong an analogy this is, Dressel says. “You may find with further inspection the details are different.”

THE WOODLANDS, Texas — A new map of flat, light-colored streaks and splotches on the moon links the features to a few large impacts that spread debris all over the surface. The finding suggests that some of the moon’s history might need rethinking.

Planetary scientist Heather Meyer, now at the Lunar and Planetary Institute in Houston, used data from NASA’s Lunar Reconnaissance Orbiter to make the map, the most detailed global look at these light plains yet. Previous maps had been patched together from different sets of observations, which made it hard to be sure that features that looked like plains actually were.
Astronomers originally assumed that the light plains were ancient lava flows from volcanoes. But rocks brought back from one of these plains by Apollo 16 astronauts in 1972 did not have volcanic compositions. That finding led some scientists to suspect the plains, which cover about 9.5 percent of the lunar surface, came from giant impacts.

Meyer’s map supports the impact idea. Most of the plains, which are visible across the whole moon, seem to originate from debris spewed from the Orientale basin, a 930-kilometer-wide bowl in the moon’s southern hemisphere that formed about 3.8 billion years ago.
“It looks like there’s just a giant splat mark,” Meyer says. About 70 percent of the lunar plains come from either Orientale or one other similar basin, she reported March 22 at the Lunar and Planetary Science Conference. “What this is telling us,” she says, “is these large basins modified the entire lunar surface at some point.”
The map also shows that some small impact craters up to 2,000 kilometers from Orientale have been filled in with plains material. That’s potentially problematic, because planetary scientists use the number of small impact craters to estimate the age of the lunar surface. If small craters have been erased by an impact half a moon away, that could mean some of the surface is older than it looks, potentially changing scientists’ interpretations of the moon’s history (SN: 6/11/16, p. 10).

China’s first space station, Tiangong-1, is expected to fall to Earth sometime between March 31 and April 1. No fooling.

Most of the 10.4-meter-long station will burn up as it zooms through Earth’s atmosphere. But some parts will survive and reach the ground, according to the European Space Agency’s Space Debris Office. No one can be sure where or when those pieces will hit. Even within hours of the station reaching the atmosphere, the final hit zone predictions will cover thousands of kilometers. ESA predicts that any latitude between 42.8° N (so as far north as Chicago) and 42.8° S (down to Tasmania) is fair game. The geometry of the station’s orbit means that the edges of that zone are more likely to be hit than the equator.
Much of that area is oceans or uninhabited. “The personal probability of being hit by a piece of debris from Tiangong-1 is actually 10 million times smaller than the yearly chance of being hit by lightning,” according to ESA. (If you’re wondering, the annual chance of getting zapped in the United States is 1 in 1,083,000.)
Launched in 2011, Tiangong-1 — which means Heavenly Palace — was visited twice by Chinese astronauts, in 2012 and in 2013. The craft was supposed to last only two years, and China put it into sleep mode after the second visit to prepare to steer it back to Earth for a controlled reentry. But in March 2016, the Chinese space agency announced that they had lost contact with the craft and expected it to reenter the atmosphere sometime in 2017
Reentry is unlikely to be dangerous, but it will look cool. The disintegrating space station will blaze through the sky like a fireball. ESA and the Chinese space agency are running daily updates on the station’s location, so check back to see if it will be visible where you are.

PHOENIX — A new, breathable material that can also block biological or chemical threats could offer comfortable protection for people working in contaminated environments or dangerous military zones.

The bottom layer of the material, described April 3 at the Materials Research Society spring meeting, features carbon nanotube pores embedded within a flexible synthetic polymer film. These pores are just a few nanometers across — too small for bacterial or viral cells to squeeze through, but wide enough for sweat to escape.
The top layer offers further protection. It is made of another, spongy polymer that normally allows water and other molecules to pass through. But when the polymer comes into contact with G-series nerve agents — the family of toxic chemicals that includes sarin gas — it flattens into a dense sheet that seals over the carbon nanopores underneath. The polymer can be restored to its original state by soaking it in a high-pH chemical broth.

Both layers together are still less than half the thickness of a sheet of paper, and could be laid over fabrics without putting the wearer at risk of overheating. That’s an improvement over the typical protective gear that’s permanently sealed against contaminants, said study coauthor Francesco Fornasiero, a chemical engineer at Lawrence Livermore National Laboratory in California.

In early testing, the material completely blocked out dengue virus cells, as well as 90 percent of the chemical diethyl chlorophosphate, used as a stand-in for toxic nerve agents. The researchers are working to make the material even more impervious to dangerous chemicals, Fornasiero said.

About 50 million years ago, a monitor lizard in what is now Wyoming perceived the world through four eyes. Saniwa ensidens is the only known jawed vertebrate to have had two eyelike photosensory structures at the top of the head, in addition to the organs we commonly think of as eyes, researchers report April 2 in Current Biology.

The structures are called the pineal and parapineal organs. Among animals alive today, only the jawless fish called a lamprey has both structures. But many modern reptiles have a so-called third eye, the pineal organ.
The researchers examined fossils collected 150 years ago by Yale University students. Scans of the fossils using a technique called X-ray computed tomography revealed spaces in the skull for both the third and fourth eye.

What the ancient lizard did with these organs isn’t known, but some modern vertebrates use the amplified photosensitivity they glean from the pineal glands to navigate. S. ensidens may have been able to perceive polarized light and use the angle of the sun like a compass, as some modern lizards do. Or it may have navigated using Earth’s magnetic field, much like some amphibians and migratory birds.

There’s a great future in plastics.

A new kind of plastic can, when exposed to the right chemicals, break down into the same basic building blocks that it came from and be rebuilt again and again. The recyclable material is more durable than previous attempts to create reusable plastics, researchers report inthe April 27 Science.

Designing plastics that can be easily reused is one line of attack against the global plastic waste problem. Only about 10 percent of plastic ever made gets recycled, according to a 2017 study in Science Advances. But the material is so cheap and useful that hundreds of millions of tons of it keeps getting churned out each year.
A major impediment to plastic recycling is that most plastics degrade into molecules that aren’t immediately useful. Transforming those molecules back into plastic or into some other product requires many chemical reactions, which makes the recycling process less efficient. And while biodegradable plastics have become popular in recent years, they break down only if the right microbes are present. More often than not, these plastics end up lingering in landfills or floating in the ocean. Creating plastics that could be broken down into their building blocks and reused without additional processing and purifying could help reduce the pollution buildup.

But designing such a plastic polymer is a balancing act, says Michael Shaver, a polymer chemist at the University of Edinburgh who wasn’t part of the study. Polymers are long chains of small molecules, called monomers, that link together like beads on a string. Monomers that need extreme temperatures or too much chemical coaxing to join up into polymers might not be practical building blocks. And resulting polymers need to be stable up to a high enough temperature that, say, pouring hot coffee into a cup made of them won’t destabilize the chains and make the plastic melt into a sticky puddle.
Polymer chemist Jianbo Zhu and his colleagues at Colorado State University in Fort Collins set out to solve this challenge. The team had had some luck in the past creating a polymer that could be broken down into its starting molecules. But the resulting plastics created by their lab and others on the same track were too soft and temperature-sensitive to have much practical use.
This time, Zhu and his colleagues modified one of their previous creations, a small ringed molecule, by adding another ring in a way that braced the molecule into a particular conformation. That rigidity helped the monomers quickly link together at room temperature into polymer chains that are heat-stable.
Then, when exposed to certain mild chemicals or high enough heat, the polymers degraded back into monomers. The researchers were able to repeat this cycle several times, showing that, in theory, the polymer could be infinitely recyclable.

While each monomer is locked into a particular conformation, not all of them have the same shape even though they’re made from the same chemical recipe. Mixing two different conformations of monomers created an even stronger plastic, says Zhu.

“This is probably the best system out there,” Shaver says.

Still, it’s not perfect yet: Zhu and his colleagues plan to tinker with the monomer design more in the future to make the resulting plastic a bit less brittle. Eventually, they hope to commercialize the product.

As opioid-related deaths rise in the United States, so has the role of synthetic opioids — primarily illicit fentanyl, mixed into heroin or made into counterfeit pills (SN Online: 3/29/18). In 2016, synthetics surged past prescription opioids and were involved in 19,413 deaths, compared with 17,087 deaths involving prescription opioids, researchers report May 1 in JAMA. The study is based on data from the National Vital Statistic System’s record of all U.S. deaths.

“Synthetic opioids are much deadlier than prescription opioids,” says emergency physician Leana Wen, Health Commissioner of Baltimore, who was not involved in the study. Fentanyl, for example, is about 50 to 100 times more potent than morphine. The illicit origins of many synthetic opioids make the public health response more difficult, she says. “We can track prescriptions; it’s much harder to track illegally trafficked drugs.”

Clearwing moths may not look all that dangerous, despite having largely see-through wings like bees and wasps. But some fly like fierce insects best left well alone.

Four clearwing species from Southeast Asian rainforests aren’t perfect mimics of local bees and wasps. Yet the resemblance looked much stronger when entomologist Marta Skowron Volponi of the University of Gdansk in Poland and her husband, nature filmmaker Paolo Volponi, spent days at a time poised with a video camera on riverbanks to capture the flight patterns. Four clearwing species occasionally showed up, including a shaggy Aschistophleps that turned out to be a species new to science.

That newly named A. argentifasciata and two other species flew in slow, zigzaggy paths that resembled the meanderings of local stingless bees. (This kind of bee is not great for snacking birds because it bites fiercely.) Another clearwing moth flew distinctly faster with broader turning sweeps instead of zigzags, much like a wasp.

Behaving like something that stings or bites may be an advantage for moths that forgo the cover of night and fly in daylight with its abundance of hungry birds and other predators that hunt by sight. Even imperfect body mimics get convincing in the air, Skowron Volponi and her colleagues report May 2 in Biology Letters.

Jupiter’s icy moon Europa may have been spitting into space for at least 20 years. Analyzing old Galileo mission data suggests that the NASA spacecraft flew through a plume of water vapor from the moon during a 1997 flyby, researchers report May 14 in Nature Astronomy.

“We now have very compelling support for the idea that Europa does possess plumes,” says study coau
Whether the moon, Jupiter’s fourth largest, has such geysers has been a lingering mystery. One of the most tantalizing results from Galileo, which orbited Jupiter from 1995 to 2003, was evidence that Europa harbors a deep ocean of liquid water beneath an icy shell. Then in 2012, data from the Hubble Space Telescope revealed high concentrations of charged hydrogen and oxygen atoms, or ions, over Europa’s southern hemisphere, a potential sign of water vapor escaping into space (SN: 1/25/14, p. 6).

The putative plumes have played peekaboo ever since (SN Online: 1/11/18), continuing to intrigue astronomers hoping to search the moon’s water for signs of life.

Jia and colleagues examined data from Galileo’s closest Europa flyby, which brought the probe within 206 kilometers of the moon’s surface. Over one spot near the equator, the spacecraft detected sudden changes in its magnetic field and plasma instruments. Using up-to-date computer simulations, the team showed that these changes are best explained by Galileo flying through an active plume. Radiation from Jupiter’s magnetic field would have split water molecules into oxygen and hydrogen ions, and those particles, in turn, would have changed the direction of the magnetic field and the density of plasma within the plume. That spot is also near where Hubble picked up a second sign of escaping water vapor
in 2014 (SN Online: 9/26/16) .
Galileo found no other signs of plumes during its 10 other Europa flybys, which were farther away from the moon. That suggests that any plumes are relatively small, extending not much higher than 200 kilometers above the surface. It’s also unclear if Europa plumes would be spewing constantly or be turning on and off.

Jia is working on magnetic field and plasma instruments for two future missions to Jupiter and its moons: the 2022 European JUICE mission and NASA’s Europa Clipper spacecraft, also planned for the early 2020s. The Clipper spacecraft will make much lower flybys over Europa, skimming as low as 25 kilometers above the surface. The new Galileo results should help in planning those flight paths, he says.

NASA will host a live discussion of these findings at 1:00 p.m. EDT on May 14. You can watch on various platforms, including NASA Television, Facebook Live and YouTube.

Planetary scientist Cynthia Phillips of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who worked on Galileo as a graduate student but was not involved in the new analysis, says it’s exciting that scientists are using new tools on the old mission data.

“During Galileo, we’d always known there was something weird during this flyby,” she says. But she is still holding out for visual confirmation of the plumes. “Pictures, or it didn’t happen.”

Sluggish memories might be captured via RNA. The molecule, when taken from one sea slug and injected into another, appeared to transfer a rudimentary memory between the two, a new study suggests.

Most neuroscientists believe long-term memories are stored by strengthening connections between nerve cells in the brain (SN: 2/3/18, p. 22). But these results, reported May 14 in eNeuro, buoy a competing argument: that some types of RNA molecules, and not linkages between nerve cells, are key to long-term memory storage.
“It’s a very controversial idea,” admits study coauthor David Glanzman, a neuroscientist at UCLA.

When poked or prodded, some sea slugs (Aplysia californica) will reflexively pull their siphon, a water-filtering appendage, into their bodies. Using electric shocks, Glanzman and his colleagues sensitized sea slugs to have a longer-lasting siphon-withdrawal response — a very basic form of memory. The team extracted RNA from those slugs and injected it into slugs that hadn’t been sensitized. These critters then showed the same long-lasting response to touch as their shocked companions.

RNA molecules come in a variety of flavors that carry out specialized jobs, so it’s not yet clear what kind of RNA may be responsible for the effect, Glanzman says. But he suspects that it’s one of the handful of RNA varieties that don’t carry instructions to make proteins, the typical job of most RNA. (Called noncoding RNAs, these molecules are often involved in manipulating genes’ activity.)

But even the few scientists who question whether the strength of nerve cell connections is the key to long-term memory storage don’t necessarily buy Glanzman’s ideas. The fact that untrained slugs become more sensitive to touch after RNA injection is “amazing,” says biochemist Tomás Ryan of Trinity College Dublin, who wasn’t part of the study. “But it doesn’t go far enough to say that the memory has been transferred.”