SAN DIEGO — Marijuana use during teenage years may change the brain in key decision-making areas, a study in rats suggests.

“Adolescence is a dangerous time to be insulting the brain, particularly with drugs of abuse,” study coauthor Eliza Jacobs-Brichford said November 7 at the annual meeting of the Society for Neuroscience.

Jacobs-Brichford and colleagues gave adolescent male and female rats a marijuana-like compound. Afterward, the researchers found changes in parts of the brain involved in making decisions.
Normally, many of the nerve cells there are surrounded by rigid structures called perineuronal nets, sturdy webs that help stabilize connections between nerve cells. But in male rats that had been exposed to the marijuana-like compound in adolescence, fewer of these nerve cells, which help put the brakes on other cells’ activity, were covered by nets. Drug exposure didn’t seem to affect the nets in female rats.

“Males look more susceptible to these drugs,” said Jacobs-Brichford, a behavioral neuroscientist at the University of Illinois at Chicago.

There’s something big lurking beneath Greenland’s ice. Using airborne ice-penetrating radar, scientists have discovered a 31-kilometer-wide crater — larger than the city of Paris — buried under as much as 930 meters of ice in northwest Greenland.

The meteorite that slammed into Earth and formed the pit would have been about 1.5 kilometers across, researchers say. That’s large enough to have caused significant environmental damage across the Northern Hemisphere, a team led by glaciologist Kurt Kjær of the University of Copenhagen reports November 14 in Science Advances.
Although the crater has not been dated, data from glacial debris as well as ice-flow simulations suggest that the impact may have happened during the Pleistocene Epoch, between 2.6 million and 11,700 years ago. The discovery could breathe new life into a controversial hypothesis that suggests that an impact about 13,000 years ago triggered a mysterious 1,000-year cold snap known as the Younger Dryas (SN: 7/7/18, p. 18).
Members of the research team first spotted a curiously rounded shape at the edge of Hiawatha Glacier in northwest Greenland in 2015, during a scan of the region by NASA’s Operation IceBridge. The mission uses airborne radar to map the thickness of ice at Earth’s poles. The researchers immediately suspected that the rounded shape represented the edge of a crater, Kjær says.
For a more detailed look, the team hired an aircraft from Germany’s Alfred Wegener Institute that was equipped with ultra-wideband radar, which can send pulses of energy toward the ice at a large number of frequencies. Using data collected from 1997 to 2014 from Operation Icebridge and NASA’s Program for Arctic Regional Climate Assessment, as well as 1,600 kilometers’ worth of data collected in 2016 using the ultra-wideband radar, the team mapped out the inner and outer contours of their target.

The object is almost certainly an impact crater, the researchers say. “It became clear that our idea had been right from the beginning,” Kjær says. What’s more, it is not only the first crater found in Greenland, but also one of the 25 or so largest craters yet spotted on Earth. And it has held its shape beautifully, from its elevated rim to its bowl-shaped depression.

“It’s so conspicuous in the satellite imagery now,” says John Paden, an electrical engineer at the University of Kansas in Lawrence and a member of the team. “There’s not another good explanation.”

On the ground, the team hunted for geochemical and geologic signatures of an asteroid impact within nearby sediments. Sampling from within the crater itself was impossible, as it remains covered by ice. But just beyond the edge of the ice, meltwater from the base of the glacier had, over the years, deposited sediment. The scientists collected a sediment sample from within that glacial outwash and several from just outside of it.

The outwash sample contained several telltale signs of an impact: “shocked” quartz grains with deformed crystal lattices and glassy grains that may represent flash-melted rock. The sample also contained elevated concentrations of certain elements, including nickel, cobalt, platinum and gold, relative to what’s normally found in Earth’s crust. That elemental profile points not only to an asteroid impact, the researchers say, but also suggests that the impactor was a relatively rare iron meteorite.
Determining when that iron meteorite slammed into Earth is trickier.
The ice-penetrating radar data revealed that the crater bowl itself contains several distinct layers of ice. The topmost layer shows a clear, continuous sequence of smaller layers of ice, representing the gradual deposits of snow and ice through the most recent 11,700 years of Earth’s history, known as the Holocene. At the base of that “well-behaved” layer is a distinct, debris-rich layer that has been seen elsewhere in Greenland ice cores, and is thought to represent the Younger Dryas cold period, which spanned from about 12,800 to 11,700 years ago. Beneath that Younger Dryas layer is another large layer — but unlike the Holocene layer, this one is jumbled and rough, with undulating rather than smooth, nearly flat smaller layers.

“You see folding and strong disturbances,” says study coauthor Joseph MacGregor, a glaciologist with Operation IceBridge. “And below that, we see yet deeper, complex basal ice.” Radar images of that bottommost ice layer within the crater show several curious peaks, which MacGregor says could represent material from the ground that got incorporated into the ice. “Putting that all together, what you have is a snapshot of an ice sheet that looked fairly normal during the Holocene, but was quite disturbed before that.”

Those data clearly suggest that the impact is at least 11,700 years old, Kjær says. And the rim of the crater appears to cut through a preexisting ancient river channel that must have flowed across the land before Greenland became covered with ice about 2.6 million years ago.

That time span — essentially, the entire Pleistocene Epoch — is a large range. The team is working on further narrowing the possible date range, with more sediment samples, simulations of the rate of ice flow and possibly cores collected from within the crater.

The date range does include the possibility that the impact occurred near the onset of the Younger Dryas. “It’s the woolly mammoth in the room,” MacGregor says.
Planetary scientist Clark Chapman of the Southwest Research Institute in Boulder, Colo., notes that “there are plenty of roughly circular landforms on Earth of many different sizes, most of which are not impact craters.” Still, he says, the paper presents several lines of evidence that strongly support the conclusion that the object is a crater, including the shocked quartz and the topography.

As for the idea that a crater may have formed within the last couple of million years, Chapman says, it’s “quite unlikely.” Such strikes are rare in general, he adds, and asteroids barreling into Earth are far more likely to land somewhere in an ocean. “[And] it would be at least a hundred times less likely that it could have happened so recently as to have affected the Younger Dryas.”

Regardless of when the crater formed, it is “a straight-up exciting discovery,” MacGregor says. “And we’re just happy not to have to keep it a secret anymore.”

Losing one variety of gut bacteria may lead to type 2 diabetes as people age.

Old mice have less Akkermansia muciniphila bacteria than young mice do, researchers report November 14 in Science Translational Medicine. That loss triggers inflammation, which eventually leads cells to ignore signals from the hormone insulin. Such disregard for insulin’s message to take in glucose is known as insulin resistance and is a hallmark of type 2 diabetes.

Researchers have suspected that bacteria and other microbes in the gut are involved in aging, but how the microbes influence the process hasn’t been clear. Monica Bodogai of the U.S. National Institute on Aging in Baltimore and colleagues examined what happens to mice’s gut bacteria as the rodents age. The mice lose A. muciniphila, also called Akk, and other friendly microbes that help break down dietary fiber into short-chain fatty acids, such as butyrate and acetate. Those fatty acids signal bacteria and human cells to perform certain functions.
Losing Akk led to less butyrate production, Bodogai’s team found. In turn, loss of butyrate triggered a chain reaction of immune cell dysfunction that ended with mice’s cells ignoring the insulin.

Treating old mice and elderly rhesus macaques with an antibiotic called enrofloxacin increased the abundance of Akk in the animals’ guts and made cells respond to insulin again. Giving old animals butyrate had the same effect, suggesting that there may be multiple ways to head off insulin resistance in older people in the future.

DENVER — Three jugs placed as offerings in a roughly 3,600-year-old tomb in Israel have revealed a sweet surprise — evidence of the oldest known use of vanilla.

Until now, vanilla was thought to have originated in Mexico, perhaps 1,000 years ago or more. But jugs from the Bronze Age site of Megiddo contain remnants of two major chemical compounds in natural vanilla extract, vanillin and 4-hydroxybenzaldehyde, said archaeologist Vanessa Linares of Tel Aviv University in Israel. Chemical analyses also uncovered residues of plant oils, including a component of olive oil, in the three jugs.
“Bronze Age people at Megiddo may have used vanillin-infused oils as additives for foods and medicines, for ritual purposes or possibly even in the embalming of the dead,” Linares said. She described these findings at the annual meeting of American Schools of Oriental Research on November 16.

Vanillin comes from beans in vanilla orchids. About 110 species of these flowers are found in tropical areas around the world. The chemical profile of the vanillin in the Megiddo jugs best matches present-day orchid species in East Africa, India and Indonesia, Linares said.

Extensive Bronze Age trade routes likely brought vanillin to the Middle East from India and perhaps also from East Africa, she suggested.

“It’s really not surprising that vanillin reached Bronze Age Megiddo given all the trade that occurred between the [Middle East] and South Asia,” says archaeologist Eric Cline of George Washington University in Washington, D.C. But no evidence exists of trade at that time between Middle Eastern societies and East Africa, says Cline, who did not participate in the Megiddo research.
Vanilla orchids or their beans probably reached Megiddo via trade routes that first passed through Mesopotamian society in southwest Asia. However Bronze Age Middle Easterners ended up with those products, discoveries at Megiddo challenge the idea that vanilla use originated only in Mexico and then spread elsewhere, Cline says.

The vanillin-containing jugs at Megiddo came from a tomb of three “highly elite” individuals who were interred with six other people of lesser social rank, said archaeologist Melissa Cradic of the University of California, Berkeley, a member of the current Megiddo research team. Excavations uncovered the tomb in 2016, Cradic also reported at the ASOR meeting.

Primary burials in the tomb consist of an adult female, an adult male and an 8- to 12-year-old boy. Elaborate types of bronze, gold and silver jewelry were found on and around the three skeletons. Exact replicas of several pieces of jewelry appeared on each individual.

The tomb lies in an exclusive part of Megiddo near a palace and a monumental city gate.

“We can’t definitively say that these three people were royals,” Cradic said. “But they were elites in Megiddo and may have belonged to the same family.”

The next NASA Mars rover will hunt for signs of ancient life in what used to be a river delta, the agency announced on November 19.

The rover is expected to launch in July 2020 and to land on Mars around February 18, 2021. It will seek out signs of past life in the sediments and sands of Jezero crater, which was once home to a 250-meter-deep lake and a river delta that flowed into the lake.
“This is a major attraction from our point of view for a habitable environment,” said Mars 2020 project scientist Ken Farley of Caltech in a news conference discussing the site. “A delta is extremely good at preserving biosignatures.” Any evidence of life that may once have existed in the lake water, or even evidence that came from the river’s headwaters and flowed downstream, could be preserved in the rocks that are there today.

The 2020 rover’s design is similar to that of the Curiosity rover, which has been exploring a different ancient crater lake, Gale crater, since 2012 (SN: 5/2/15, p. 24). But where Curiosity has an onboard chemistry lab for studying the rocks and minerals in its crater, Mars 2020 will have a specialized backpack for sample storage. A future mission will pick up the cached samples and return them to Earth for more detailed study, possibly sometime in the 2030s.

“The samples will come back to the best labs — not the best labs we have today, but the best labs we will have then,” said science mission directorate administrator Thomas Zurbuchen of NASA headquarters in Washington, D.C.

Mars 2020 will also use a souped-up version of Curiosity’s landing system called Sky Crane, in which a hovering platform lowers the rover onto the ground with a cable. Mars 2020’s version will include a navigation system that will help it avoid hazards on the ground, like cliff faces and boulders.
Jezero crater is within striking distance of another site on scientists’ wish list. That region, called Midway, is just 28 kilometers away from Jezero and contains some of the most ancient rocks on Mars. At the final landing site selection workshop in October, scientists floated the idea of visiting both sites in one mission, a feat seen as ambitious but achievable. But a decision on that will have to wait until after the rover is safely on Mars, Farley said.

For the first time, humans have built a set of pushy, destructive genes that infiltrated small populations of mosquitoes and drove them to extinction.

But before dancing sleeveless in the streets, let’s be clear. This extermination occurred in a lab in mosquito populations with less of the crazy genetic diversity that an extinction scheme would face in the wild. The new gene drive, constructed to speed the spread of a damaging genetic tweak to virtually all offspring, is a long way from practical use. Yet this test and other news from 2018 feed one of humankind’s most persistent dreams: wiping mosquitoes off the face of the Earth.

For the lab-based annihilation, medical geneticist Andrea Crisanti and colleagues at Imperial College London focused on one of the main malaria-spreading mosquitoes, Anopheles gambiae. The mosquitoes thrive in much of sub-Saharan Africa, where more than 400,000 people a year die from malaria, about 90 percent of the global total of malaria deaths.

To crash the lab population, the researchers put together genes for a molecular copy-and-paste tool called a CRISPR/Cas9 gene drive. The gene drive, which in this case targeted a mosquito gene called doublesex, is a pushy cheat. It copies itself into any normal doublesex gene it encounters, so that all eggs and sperm will carry the gene drive into the next generations. Female progeny with two altered doublesex genes develop more like males and, to people’s delight, can’t bite or reproduce.

In the test, researchers set up two enclosures, each mixing 150 males carrying the saboteur genes into a group of 450 normal mosquitoes, males and females. Extinction occurred in eight generations in one of the enclosures and in 12 in the other (SN: 10/27/18, p. 6).

This is the first time that a gene drive has forced a mosquito population to breed itself down to zero, says Omar Akbari of the University of California, San Diego, who has worked on other gene drives. However, he warns, “I believe resistance will be an issue in larger, diverse populations.” More variety in mosquito genes means more chances of some genetic quirk arising that counters the attacking gene drive.

But what if a gene drive could monkey-wrench a wild population, or maybe a whole species, all the way to extinction? Should people release such a thing? To make sense of this question, we humans will have to stop talking about “mosquitoes” as if they’re all alike. The more than 3,000 species vary considerably in what they bite and what ecosystem chores they do.

The big, iridescent adults of Toxorhynchites rutilus, for instance, can’t even drink blood. And snowmelt mosquitoes (Ochlerotatus communis) are pollinators of the blunt-leaved orchid (Platanthera obtusata), ecologist Ryo Okubo of the University of Washington in Seattle said at the 2018 meeting of the Society for Integrative and Comparative Biology.
Estimating what difference it would make ecologically if a whole mosquito species disappeared has stirred up plenty of speculation but not much data. “I got pretty fed up with the hand-waving,” says insect ecologist Tilly Collins of Imperial College London. So she and colleagues dug through existing literature to see what eats An. gambiae and whether other mosquitoes would flourish should their competitor vanish.

So far, extermination of this particular mosquito doesn’t look like an ecological catastrophe, Collins says. Prey information is far from perfect, but diets suggest that other kinds of mosquitoes could compensate for the loss. The species doesn’t seem to be any great prize anyway. “As adults, they are small, not juicy, and hard to catch,” she says. The little larvae, built like aquatic caterpillars with bulging “shoulders” just behind their heads, live mostly in small, temporary spots of water.
The closest the researchers came to finding a predator that might depend heavily on this particular mosquito was the little East African jumping spider Evarcha culicivora. It catches An. gambiae for about a third of its diet and likes the females fattened with a human blood meal. Yet even this connoisseur “will readily consume” an alternative mosquito species, the researchers noted in July in Medical and Veterinary Entomology.

Collins also thinks about the alternatives to using genetically engineered pests as pest controls. Her personal hunch is that saddling mosquitoes with gene drives to take down their own species is “likely to have fewer ecological risks than broad-spectrum use of pesticides that also kill other species and the beneficial insects.”

Gene drives aren’t the only choice for weaponizing live mosquitoes against their own kind. To pick just one example, a test this year using drones to spread radiation-sterilized male mosquitoes in Brazil improved the chances that the old radiation approach will be turned against an Aedes mosquito that can spread Zika, yellow fever and chikungunya.

Old ideas, oddly enough, may turn out to be an advantage for antimosquito technologies in this era of white-hot genetic innovation. Coaxing the various kinds of gene drives to work is hard enough, but getting citizens to sign off on their use may be even harder.

For three years, a team of scientists kept a big secret: They had discovered a giant crater-shaped depression buried beneath about a kilometer of ice in northwestern Greenland. In November, the researchers revealed their find to the world.

They hadn’t set out to find a crater. But in 2015, glaciologists studying ice-penetrating radar images of Greenland’s ice sheet, part of an annual survey by NASA’s Operation IceBridge mission, noticed an oddly rounded shape right at the northern edge of Hiawatha Glacier. If the 31-kilometer-wide depression is confirmed to be the remnant of a meteorite impact — and the team has produced a wealth of evidence suggesting that it is (SN: 12/8/18, p. 6) — the discovery is exciting in and of itself. It’s rare to find a new crater, let alone one on land that has retained its perfect bowl shape.

“This is just a straight-up exciting discovery that starts with this wonderful element of serendipity,” says team member Joseph MacGregor, a glaciologist with Operation IceBridge.

But the crater — let’s call it that, for the sake of discussion — may have also reignited a debate over a controversial hypothesis about a mysterious cold snap known as the Younger Dryas. This cold period began abruptly about 12,800 years ago and ended just as abruptly about 11,700 years ago. For more than a decade, a small group of researchers, unconnected with the group behind the new discovery, has suggested that a cosmic impact triggered the cooling (SN: 7/7/18, p. 18).
Proponents of the Younger Dryas impact hypothesis say that the remnants of a comet exploded in Earth’s atmosphere and that the airbursts sparked wildfires across North America. Soot and other particles from the fires blocked out the sun, causing the cold snap, which has been blamed for everything from the extinction of the mammoths to the disappearance of a group of people known as the Clovis.

Most scientists reject that an impact was responsible, refuting the idea that there were vast wildfires at the time or that the Clovis people even disappeared. Another big objection: the lack of a smoking gun, a crater dating to the onset of the Younger Dryas.
The “mammoth in the room,” therefore, is whether the Greenland crater might be that smoking gun. But a large, recent impact would be extremely unlikely, given the rarity of such impacts on Earth, particularly on land, says planetary scientist Clark Chapman of the Southwest Research Institute in Boulder, Colo., who was not involved with the discovery.

Indeed, one sticking point is that there are no direct dates for the newly discovered crater, because it is still buried beneath all that ice. The radar data offer only tantalizing clues to the age, suggesting that the crater is between 2.6 million and 11,700 years old.

That’s a huge time range, but the proponents of the hypothesis are convinced that this crater is what they’ve been waiting for. “I think it’s transformational in terms of convincing a lot of skeptics,” says James Kennett, a geologist at the University of California, Santa Barbara.
There’s another big sticking point when it comes to linking this crater to the impact hypothesis: Instead of a fragment of a comet, the discoverers think the Hiawatha impactor was an iron meteorite. That determination is based on measurements of platinum and other elements in glacial outwash, sediments carried by meltwater from beneath the ice. An iron meteorite impact would probably not produce the kinds of explosive airbursts that could ignite continent-scale wildfires, says Michail Petaev, a geochemist at Harvard University.
Petaev and colleagues previously found a hint that an iron meteorite might have smacked into Greenland about 13,000 years ago. In 2013, his group examined Greenland ice cores and found a strange platinum anomaly dating to right before the Younger Dryas. The ratio of platinum to iridium measured in the ice cores points to an iron meteorite, the team reported.

Despite the platinum data, the impact hypothesis proponents hold firmly to the idea that the Hiawatha impactor was a comet. Because little is known about comet compositions, Kennett says, a comet might well have been the source for the platinum found in the glacial outwash and the ice cores. But Petaev maintains that the observed platinum ratios just wouldn’t occur in a comet, which is made of the primitive stuff of the universe. Instead, he says, those ratios require the cycles of melting and recrystallizing that form iron meteorites, the ancient cores of asteroids or planets.
Glaciologist Kurt Kjær of the University of Copenhagen, who led the team that identified the crater, and his colleagues don’t want to weigh in on the Younger Dryas debate. “We can’t prove it,” Kjær says. “But we can certainly not disprove it.”

Instead, the crater’s discoverers are planning to collect more sediments from the glacial outwash, and perhaps even drill directly into the crater to retrieve sediment cores that can be dated. And there may be other craters lurking beneath Greenland’s ice, or even Antarctica’s — perhaps more easily identifiable once you know what to look for, says MacGregor.

Asked whether the team has actually identified any other round shapes of interest, he pauses. Then MacGregor says, cryptically, “stay tuned.”

Mysterious particles called neutrinos constantly barrel down on Earth from space. No one has known where, exactly, the highest-energy neutrinos come from. This year, scientists finally put a finger on one likely source: a brilliant cosmic beacon called a blazar. The discovery could kick-start a new field of astronomy that combines information gleaned from neutrinos and light.

It began with one high-energy neutrino spotted on September 22, 2017, by the IceCube observatory, a giant particle detector with thousands of sensors buried deep in the ice at the South Pole. Alerted by IceCube, astronomers soon spotted a flare from a blazar about 4 billion light-years away. The neutrino had come from the same area of the sky. With that matchup in time and space between the neutrino and the blazar’s light, scientists in 2018 pegged the blazar as the particle’s probable source (SN: 8/4/18, p. 6).

“People have been hoping for this kind of discovery for decades,” says astrophysicist Meg Urry of Yale University.
Blazars are active regions at the centers of galaxies that spew jets of high-energy matter and light toward Earth. Both the Earth-orbiting Fermi Gamma-ray Space Telescope and the Major Atmospheric Gamma Imaging Cherenkov, or MAGIC, telescopes in the Canary Islands reported that the blazar was violently flaring up in gamma rays, a type of high-energy light, at about the same time the neutrino was detected.

After combing through old data, IceCube researchers found evidence of even more neutrinos from near the blazar’s location in the sky. With those extra neutrinos, the researchers were finally convinced that the blazar birthed neutrinos.
Not only did the detection hint at the source of at least some high-energy spacefaring particles, it also taught physicists a few things about blazars. Scientists weren’t sure what kinds of particles blazars emit, but the detection reveals that the jets contain protons. That’s because scientists know that any neutrino from a blazar would have to be produced in combination with protons.

The discovery, scientists say, could invigorate a nascent field, dubbed multimessenger neutrino astronomy, to reveal secrets of the cosmos, whether from blazars or other sources. Now, says astrophysicist Kohta Murase of Penn State, “we can use neutrinos as very important probes” to learn more about the objects that spit them out. For example, researchers might spot neutrinos from a collision of two neutron stars, like the one detected by the Advanced Laser Interferometer Gravitational-Wave Observatory, LIGO, in 2017 (SN: 11/11/17, p. 6). IceCube didn’t see any neutrinos from that event, but astrophysicists are hopeful that future neutron star smashups will produce a neutrino bounty.

Before scientists are fully confident that blazars can blast out high-energy neutrinos, researchers need to spot more of the wily particles, Murase says. To improve detection, an upgrade to IceCube will make the detector 10 times bigger in volume and should be ready by the mid-2020s, says Francis Halzen, leader of IceCube and an astrophysicist at the University of Wisconsin–Madison. If all goes well, the tiny particles may soon be revealing secrets from new corners of the cosmos.

Cleaning up ocean pollution is no simple task, as an effort to fish plastic out of the Pacific Ocean is revealing.

In September, scientists launched a 600-meter-long boom meant to herd plastic debris from the great Pacific garbage patch into a net (SN Online: 9/7/18). The trash accumulation, which is twice the size of Texas, swirls in waters between California and Hawaii.

But some scientists worry the system, designed by a Dutch organization called Ocean Cleanup, could harm marine wildlife. Others aren’t convinced it will even work. Four months in, some of those concerns appear to be founded: Wind and currents have pushed trash into the rig, but the setup hasn’t kept the trash corralled as planned. Now part of the rig has broken off, and the device is being towed back to shore for repairs and design tweaks.
Whether the system will eventually help remove garbage from the Pacific remains to be seen. But it’s not the only option for reducing how much plastic is dumped in the oceans — now at some 5 trillion pieces, per some estimates. Here are a few other approaches seeing success.

1. Meet Mr. Trash Wheel and friends
   It’s easier to collect trash from rivers and streams than from the open ocean. Baltimore has deployed three giant waterwheels that trap river plastic before it flows into the harbor.
   The first installation, adorned with googly eyes and dubbed Mr. Trash Wheel, debuted in 2014, followed by Professor Trash Wheel in 2016 and Captain Trash Wheel in 2018. Collectively, the wheels so far have removed more than 680,000 kilograms of trash.

Mr. Trash Wheel wasn’t immediately successful, though, says Adam Lindquist, director of Baltimore’s Healthy Harbor Initiative. A waterwheel installed in 2008 didn’t work well. He suggests that the Ocean Cleanup group, in tweaking its device, could also see improvements — though clearing plastic from the ocean is certainly a bigger job than cleaning a river, he says.

2. Snag it on land
   Collecting debris as it’s washed onto beaches is another way to tackle the plastic problem. “Lots of published papers show the ocean spits out trash really quickly,” says Marcus Eriksen, an environmental scientist and cofounder of the 5 Gyres Institute based in Los Angeles.

The U.S. National Oceanic and Atmospheric Administration’s Marine Debris Program, for example, has collected more than 450 tons of garbage from the Alaska shoreline since 2006.

3. Rise of the bans
   Using less plastic in the first place is the most straightforward way to cut down on ocean pollution. Many cities and 127 countries have imposed regulations on single-use plastic, such as grocery bags or plastic straws, according to a December report from the U.N. Environment Program.

These restrictions can make a difference. In 2010, thousands of volunteers collecting and tallying garbage along the California coast found that 7 percent of the trash consisted of plastic bags. In 2017, after multiple California cities imposed plastic bag bans or restrictions, the bags made up less than 2 percent of trash gathered.

Bans can also fight debris that the Ocean Cleanup’s system won’t snag — microplastics, tiny fragments that can harm the health of people and other animals. The United States banned microbeads in personal care products starting in 2017; the European Union has voted to enact a similar ban by 2020.

4. Rethink the cycle
   Plastic can take decades or even centuries to break down, so some scientists are working on alternatives that are easier to recycle. For example, a type of recyclable plastic described in Science in 2018 can be broken down into component pieces and rebuilt again and again (SN: 5/26/18, p. 12). But if recyclable plastic ends up in a landfill or in the ocean, those special properties won’t matter.

“There’s a really big gap between what can be recycled in a perfect world, and what actually gets recycled,” says Miriam Goldstein, the director of ocean policy at the Center for American Progress, a research and lobbying organization in Washington, D.C. Bridging that gap isn’t as simple as telling people to use less plastic, she says. “You cannot opt out of single-use plastics in most of the country,” and lots of products are designed in ways that make them challenging to properly recycle.

That’s one reason why an approach called extended producer responsibility is gaining popularity — essentially, holding companies that make plastic products responsible for the cost of proper disposal. “If you’re going to make anything, you need to think of the recovery,” Eriksen says. Putting a financial burden on the producer provides an incentive for designing products that are easier to recycle or reuse. One example: using just one type of plastic instead of combining plastics that would then need to be separated for proper recycling.

The fishing industry also needs incentives to join in the cleanup, Eriksen says. Surveys of detritus that washes ashore suggest that a substantial portion is left by fishers. Giving them a financial reason to retrieve old nets and buoys could help keep our oceans clean.

Quantum physics has earned a reputation as a realm of science beyond human comprehension. It describes a microworld of perplexing, paradoxical phenomena. Its equations imply a multiplicity of possible realities; an observation seems to select one of those possibilities for accessibility to human perception. The rest either disappear, remain hidden or weren’t really there to begin with. Which of those explanations pertains is debated by competing interpretations of the quantum math, pursued in a field of study known as quantum foundations.

Numerous quantum interpretations have been proposed — and an even greater number of books have been written about them. Two of the latest such books offer very different perspectives.
Philip Ball, in Beyond Weird, argues that much of the famous quantum weirdness lies in the popular descriptions of it, rather than in the math itself. Adam Becker’s What is Real? insists that the traditional “Copenhagen interpretation” is misguided; he extols the work of several physicists who reject it. Becker writes with exuberance and self-assuredness, often focusing on the personal stories of the scientists he discusses. Ball’s approach is less personal but more conversational, although he does not try to evade the sticky technicalities that illustrate and partially explain the quantum mysteries.
Ball contends that many of the analogies and illustrations used by popularizers (and physicists) to convey the weirdness of quantum theory (like a particle being in two places at once) are actually misleading. With less flamboyant phrasing, in Ball’s view, quantum physics can seem less perplexing, even almost understandable.

Without fully endorsing it, Ball gives a fairly sound presentation of the Copenhagen interpretation, based on the ideas of the Danish physicist Niels Bohr. Bohr held that quantum reality cannot be described apart from the experiments designed to probe it. A particle has many possible locations before you experimentally observe it; once observed, the location is established and the other possibilities vanish. And an electron will seem to behave as a particle or wave, depending on what sort of experimental apparatus you use to observe it.

Bohr expressed these truths by a principle he called complementarity — mutually exclusive concepts (such as wave or particle) are required to explain reality, but both concepts cannot be observed in any individual experiment. Bohr’s elaborations on this idea are famously convoluted and expressed rather obscurely. (When asked what is complementary to truth, Bohr replied, “clarity.”)

Bohr’s lack of clarity has led to many misinterpretations of what he meant, and it is those misinterpretations that Becker criticizes, rather than Bohr’s actual views. Becker’s main argument insists that the Copenhagen interpretation embraces the philosophy known as positivism (roughly, nothing unobservable is real, and sensory perceptions are the realities on which science should be based), and then demonstrates positivism’s fallacies. He does a fine job of demolishing positivism. Unfortunately, the Copenhagen interpretation is not positivistic, as its advocates have often pointed out. Bohr’s colleague Werner Heisenberg said so quite clearly: “The Copenhagen interpretation of quantum theory is in no way positivistic,” he wrote. And the philosopher Henry Folse’s 1985 book on Bohr’s philosophy thoroughly dispelled the mistaken belief that Bohr’s view was positivistic or opposed to the existence of an underlying reality.

Becker’s book commits many other more specific errors. He says Heisenberg found his famous uncertainty principle “buried in the mathematics of [Erwin] Schrödinger’s wave mechanics.” But Heisenberg despised wave mechanics and did his work on uncertainty wholly within his own matrix mechanics. Becker claims that physicists Murray Gell-Mann and James Hartle “had long been convinced that the Copenhagen interpretation had to be wrong.” But Gell-Mann and Hartle are on record stating that the Copenhagen view is not wrong, merely limited to special cases and not general enough to tell the whole quantum story.

Becker’s book does offer engaging discussions of the physicists who have questioned Bohr’s ideas and proposed alternate ways of interpreting quantum physics. But he allows the opponents to frame Bohr’s position rather than devoting any effort of his own to examining the subtlety and depth of Bohr’s philosophy and arguments. And Becker fails to address the important point that every quantum experiment’s results, no matter how bizarre, are precisely what Bohr would have expected them to be.

Becker does not engage deeply with the more recent body of work on quantum foundations, an area where Ball excels. Ball especially favors the perspective on quantum physics offered by the notion of quantum decoherence. Very roughly, the decoherence process dissipates various possible quantum realities into the environment, and only those versions of reality that are robustly recorded in the environment present themselves to observers. It’s of course much more complicated than that, and Ball admirably conveys those complications even at the occasional expense of clarity. Which puts his account closer to the truth.