Clumps of dark matter may be sailing through the Milky Way and other galaxies.

Typically thought to form featureless blobs surrounding entire galaxies, dark matter could also collapse into smaller clumps — similar to normal matter condensing into stars and planets — a new study proposes. Thousands of collapsed dark clumps could constitute 10 percent of the Milky Way’s dark matter, researchers from Rutgers University in Piscataway, N.J., report in a paper accepted in Physical Review Letters.
Dark matter is necessary to explain the motions of stars in galaxies. Without an extra source of mass, astronomers can’t explain why stars move at the speeds they do. Such observations suggest that a spherical “halo” of invisible, unidentified massive particles surrounds each galaxy.

But the halo might be only part of the story. “We don’t really know what dark matter at smaller scales is doing,” says theoretical physicist Matthew Buckley, who coauthored the study with physicist Anthony DiFranzo. More complex structures might be hiding within the halo.

To collapse, dark matter would need a way to lose energy, slowing particles as gravity pulls them into the center of the clump, so they can glom on to one another rather than zipping right through. In normal matter, this energy loss occurs via electromagnetic interactions. But the most commonly proposed type of dark matter particles, weakly interacting massive particles, or WIMPs, have no such way to lose energy.

Buckley and DiFranzo imagined what might happen if an analogous “dark electromagnetism” allowed dark matter particles to interact and radiate energy. The researchers considered how dark matter would behave if it were like a pared-down version of normal matter, composed of two types of charged particles — a dark proton and a dark electron. Those particles could interact — forming dark atoms, for example — and radiate energy in the form of dark photons, a dark matter analog to particles of light.
The researchers found that small clouds of such dark matter could collapse, but larger clouds, the mass of the Milky Way, for example, couldn’t — they have too much energy to get rid of. This finding means that the Milky Way could harbor a vast halo, with a sprinkling of dark matter clumps within. By picking particular masses for the hypothetical particles, the researchers were able to calculate the number and sizes of clumps that could be floating through the Milky Way. Varying the choice of masses led to different levels of clumpiness.

In Buckley and DiFranzo’s scenario, the dark matter can’t squish down to the size of a star. Before the clumps get that small, they reach a point where they can’t lose any more energy. So a single clump might be hundreds of light-years across.

The result, says theoretical astrophysicist Dan Hooper of Fermilab in Batavia, Ill., is “interesting and novel … but it also leaves a lot of open questions.” Without knowing more about dark matter, it’s hard to predict what kind of clumps it might actually form.

Scientists have looked for the gravitational effects of unidentified, star-sized objects, which could be made either of normal matter or dark matter, known as massive compact halo objects, or MACHOs. But such objects turned out to be too rare to make up a significant fraction of dark matter. On the other hand, says Hooper, “what if these things collapse to solar system‒sized objects?” Such larger clumps haven’t have been ruled out yet.

By looking for the effects of unexplained gravitational tugs on stars, scientists may be able to determine whether galaxies are littered with dark matter clumps. “Because we didn’t think these things were a possibility, I don’t think people have looked,” Buckley says. “It was a blind spot.”

Up until now, most scientists have focused on WIMPs. But after decades of searching in sophisticated detectors, there’s no sign of the particles (SN: 11/12/16, p. 14). As a result, says theoretical physicist Hai-Bo Yu of the University of California, Riverside, “there’s a movement in the community.” Scientists are now exploring new ideas for what dark matter might be.

The first 117 elements on the periodic table were relatively normal. Then along came element 118.

Oganesson, named for Russian physicist Yuri Oganessian (SN: 1/21/17, p. 16), is the heaviest element currently on the periodic table, weighing in with a huge atomic mass of about 300. Only a few atoms of the synthetic element have ever been created, each of which survived for less than a millisecond. So to investigate oganesson’s properties, scientists have to rely largely on theoretical predictions.
Recent papers by physicists, including one published in the Feb. 2 Physical Review Letters, detail some of the strange predicted properties of the weighty element.

1. Relatively weird
   According to calculations using classical physics, oganesson’s electrons should be arranged in shells around the nucleus, similar to those of xenon and radon, two other heavy noble gases. But calculations factoring in Einstein’s special theory of relativity, which take into account the high speeds of electrons in superheavy elements, show how strange the element may be. Instead of residing in discrete shells — as in just about every other element — oganesson’s electrons appear to be a nebulous blob.
2. Getting a reaction
   On the periodic table, oganesson is grouped with the noble gases, which tend not to react with other elements. But because of how its electrons are configured, oganesson is the only noble gas that’s happy to both give away its electrons and receive electrons. As a result, the element could be chemically reactive.
3. Solid as a rock?
   Oganesson’s electron configuration could also let atoms of the element stick together, instead of just bouncing off one another as gas atoms typically do. At room temperature, scientists expect that these oganesson atoms could clump together in a solid, unlike any other noble gases.
4. Bubbling up
   Protons inside an atom’s nucleus repel one another due to their like charges, but typically remain bound together by the strong nuclear force. But the sheer number of oganesson’s protons — 118 — may help the particles overcome this force, creating a bubble with few protons at the nucleus’s center, researchers say. Experimental evidence for a “bubble nucleus” has been found for an unstable form of silicon (SN: 11/26/16, p. 11).
5. Neutral territory
   Unlike oganesson’s protons, which are predicted to be in distinct shells in the nucleus, the element’s neutrons are expected to mingle. This is at odds with some other heavy elements, in which the neutron rings are well-defined.

For Oganessian, these theoretical predictions about the element have come as a surprise. “Now it’s up to experiment,” he says. Predictions about the bizarre element could be put to the test once a facility for creating superheavy elements, under construction at Oganessian’s lab in Dubna, Russia, is up and running later this year.

AUSTIN, Texas — If alien microbes crash-land on Earth, they may get a warm welcome.

When people were asked how they would react to the discovery of extraterrestrial microbial life, they give generally positive responses, researchers reported at a news conference February 16 at the annual meeting of the American Association for the Advancement of Science.

This suggests that if microbial life is found on Mars, Saturn’s icy moon Enceladus (SN: 5/13/17, p. 6) or elsewhere in the solar system, “we’ll take the news rather well,” said Michael Varnum, a social psychologist at Arizona State University in Tempe. What’s more, the tone of news reports announcing potential evidence for intelligent aliens suggests people would welcome that news, too.
Varnum and colleagues asked about 500 online volunteers — all in the United States — to describe how they would react if they learned scientists had discovered alien microbes. Varnum’s team analyzed each response using software that determined the fraction of words indicating positive emotion, such as “nice,” and negative emotion, like “worried.” The program also scanned for reward- and risk-focused words, such as “benefit” and “danger.”
People generally used more positive and reward-oriented words than negative and risk-oriented ones to describe their anticipated reactions. The same held true when participants were asked how they expected everyone else to take the news.
In another study, Varnum’s team asked about 500 U.S.-based volunteers to read one of two newspaper articles. One from 1996 reported the discovery of evidence for fossilized Martian microbes in a meteorite (SN: 8/10/96, p. 84). In the second, researchers announced in 2010 that they had created a synthetic bacterial cell in the lab (SN: 6/19/10, p. 5).
Both groups responded favorably to the articles, but the people who read about Martian microbes had a more positive reaction. This suggests that while people feel good about discoveries of any previously unknown life-forms, they are particularly keen on finding aliens, Varnum says.

But “any finding that comes from one population — like Americans — you have to take with a grain of salt,” Varnum says. He and his colleagues now hope to gather responses from participants of different cultures, to compare how people across the globe would take the news of alien microbes.

Psychologist and SETI researcher Douglas Vakoch, who heads the nonprofit organization Messaging Extraterrestrial Intelligence in San Francisco, suggests researchers also gauge reactions to different scenarios of alien microbial discovery. The Martian meteorite described in the 1996 article “has been on Earth for a long time and nothing bad has happened,” says Vakoch, who wasn’t involved in the work. “That’s a really safe scenario.” But, he wonders, are people as gung-ho about the prospect of finding live microbes on other planets or aboard meteorites?

And what if the aliens were intelligent? “If you find intelligent life elsewhere, [you] know that you’re not the only kid on the block,” says Seth Shostak, an astronomer at the SETI Institute in Mountain View, Calif. Knowing that human intelligence isn’t so special after all could provoke a much different emotional response than finding mere microbes “like pond scum in space,” Shostak says.

To get a sense of how people would feel about finding intelligent aliens, Varnum analyzed reports that the interstellar asteroid ‘Oumuamua could be an alien spaceship (SN Online: 12/18/17). The news articles took a largely positive angle. So the broader public might also take kindly to the discovery of little green men, Varnum says.

Tap — gently — the plump rear of a young Nessus sphinx hawk moth, and you may hear the closest sound yet discovered to a caterpillar voice.

Caterpillars don’t breathe through their mouths. Yet a Nessus sphinx hawk moth, if disturbed, will emit from its open mouth a sustained hiss followed by a string of scratchy burplike sounds. “Hard to describe,” says animal behaviorist Jayne Yack of Carleton University in Ottawa, who urges people just to listen to it for themselves.
This newfound noise from young Amphion floridensis may startle birds or other would-be predators not expecting something as generally quiet as most caterpillars to erupt in sound.

The discovery marks the fourth sound-producing mechanism in caterpillars that Yack and colleagues have found. Some caterpillars use their spiracles, respiratory pores along the flanks, to toot sounds. Caterpillars take in oxygen and release waste carbon dioxide through these pores. These gases, which don’t depend on the caterpillar version of blood to travel throughout the body, move through a branching air duct system of increasingly tiny pipes. Two other kinds of caterpillar noises involve mouthparts rubbing against each other. But none of those noisemakers are involved here, researchers report online February 26 in Journal of Experimental Biology.

Instead, the new anatomical studies and computer modeling suggest that these caterpillars speak by pulling air in through their mouths and into their guts and then releasing it. The rush of air inward could create the first hissing part, and outrushes could make the string of scratchy burps. There’s no sign of a special sound-making flap in the gut, but air whooshing through a constriction could make noisy turbulence. That could give a caterpillar voice its own version of teakettle squeals. In miniature, of course.

A complex coral reef full of nooks and crannies is a coastline’s best defense against large ocean waves. But coral die-offs over the next century could allow taller waves to penetrate the corals’ defenses, simulations suggest. A new study finds that at some Pacific Island sites, waves reaching the shore could be more than twice as high as today’s by 2100.

The rough, complex structures of coral reefs dissipate wave energy through friction, calming waves before they reach the shore. As corals die due to warming oceans (SN: 2/3/18, p. 16), the overall complexity of the reef also diminishes, leaving a coast potentially more exposed. At the same time, rising sea levels due to climate change increasingly threaten low-lying coastal communities with inundation and beach erosion — and stressed corals may not be able to grow vertically fast enough to match the pace of sea level rise. That could also make them a less effective barrier.

Researchers compared simulations of current and future sea level and reef conditions at four sites with differing wave energy near the French Polynesian islands of Moorea and Tahiti. The team then simulated the height of a wave after it has passed the reef, known as the back-reef wave height, under several scenarios. The most likely scenario studied was based on the Intergovernmental Panel on Climate Change’s projections of sea level height by 2100 and corresponding changes in reef structure.

Under those conditions, the average back-reef wave heights at the four sites would be 2.4 times as high in 2100 as today, the team reports February 28 in Science Advances. That change would be largely due to the decrease in coral reef complexity rather than rising sea levels, the simulations suggest. Coastal communities around the world will likely see similar wave height increases, dependent on local reef structures and extent of sea level rise. The finding, the researchers say, shows that conserving reefs is crucial to protecting coastal communities in a changing climate.

As a physics reporter and lover of mathematics, I won’t be celebrating Pi Day this year. That’s because pi is wrong.

I don’t mean that the value is incorrect. Pi, known by the symbol π, is the number you get when you divide a circle’s circumference by its diameter: 3.14159… and so on without end. But, as some mathematicians have argued, the mathematical constant was poorly chosen, and students worldwide continue to suffer as a result.

A longtime fixture of high school math classes, pi has inspired books, art (SN Online: 5/4/06) and enthusiasts who memorize it to tens of thousands of decimal places (SN: 4/7/12, p. 12). But some contend that replacing pi with a different mathematical constant could make trigonometry and other math subjects easier to learn. These critics — including myself — advocate for an arguably more elegant number equal to 2π: 6.28318…. Sometimes known as tau, or the symbol τ, the quantity is equal to a circle’s circumference divided by its radius, not its diameter.

This idea is not new. In 2001, mathematician Bob Palais of the University of Utah in Salt Lake City published an article in the Mathematical Intelligencer titled “ π is wrong!” The topic gained more attention in 2010 with The Tau Manifesto, posted online by author and educator Michael Hartl. But the debate tends to reignite every year on March 14, which is celebrated as Pi Day for its digits: 3/14.
The simplest way to see the failure of pi is to consider angles, which in mathematics are typically measured in radians. Pi is the number of radians in half a circle, not a whole circle. That makes things confusing: For example, the angle at the tip of a slice of pizza — an eighth of a pie — isn’t π/8, but π/4. In contrast, using tau, the pizza-slice angle is simply τ/8. Put another way, tau is the number of radians in a full circle.

That factor of two is a big deal. Trigonometry — the study of the angles and lines found in shapes such as triangles — can be a confusing whirlwind for students, full of blindly plugging numbers into calculators. That’s especially true when it comes to sine and cosine, two important functions in trigonometry. Many trigonometry problems involve calculating the sine or cosine of an angle. When graphed, the two functions look like a series of wiggles, shaped a bit like an “S” on its side, that repeat the same values every 2π. That means pi covers only half of an S. Tau, on the other hand, covers the full wiggle, a more intuitive measure.

Pi has become so embedded in mathematics that it could be hard to excise. A more practical approach may be to introduce tau as a teaching tool alongside pi, rather than a replacement. Education is where tau’s impact is most likely to be felt: Professional scientists and mathematicians can comfortably handle the factors of two that crop up with pi in equations.

You might argue that multiplying by two isn’t that hard, even for students. But it isn’t the arithmetic that concerns me. Trigonometry is notorious for creating a divide between the math-fluent and math-phobic. But helping more people understand and enjoy mathematics isn’t some pie-in-the-sky fantasy. Everyone is capable of doing math. We just need to work smarter, and speak more clearly, to help those who struggle.

So here’s to June 28 — Tau Day.

BOSTON — The bond between parent and child is powerful enough to override fear. New research shows that if a parent sits with a young child during a potentially scary situation, the child isn’t as afraid of it later.

The study is in line with research suggesting that during particular stages of development, a strong connection with a caregiver tamps down activity in the amygdala, the brain structure that helps process fear and spurs the fight-or-flight response.
“Fight or flight is pointless if you are tiny,” said developmental neuroscientist Nim Tottenham of Columbia University, who presented the work March 26 at a Cognitive Neuroscience Society meeting. For young kids, the bond with a caregiver not only helps ensure survival but also makes kids feel safe, enabling them to approach the world with confidence, Tottenham said. “Attachment is a strategy that has worked very well; it trumps everything.”

Kids from ages 3 to 5 were shown two shapes — a green triangle and a blue square. Just the square was accompanied by a loud, fingers-on-the-chalkboard kind of noise. Some kids had a parent sitting next to them while they saw the shapes; others sat with a researcher. After the parents left, kids chose which door to go through to get a present: one with the scary blue square on it, the other with the innocuous green triangle.

Kids paired with the experimenter avoided the door with the blue square. But kids who had sat next to a parent showed a slight preference for that door, even though they knew they would collect the same present from behind either door.

Stephen Hawking, a black hole whisperer who divined the secrets of the universe’s most inscrutable objects, left a legacy of cosmological puzzles sparked by his work, and inspired a generation of scientists who grew up reading his books.

Upon Hawking’s death on March 14 at age 76, his most famous discovery — that black holes aren’t entirely black, but emit faint radiation — was still fueling debate.

Hawking “really, really cared about the truth, and trying to find it,” says physicist Andrew Strominger of Harvard University, who collaborated with the famed scientist. Hawking “was deeply committed, his whole life, to this quest of understanding more about the physical universe around us.”

After earning his Ph.D. in 1965 at the University of Cambridge, Hawking continued studying cosmology there for the rest of his life. Due to a degenerative illness, amyotrophic lateral sclerosis, or ALS, Hawking gradually lost control of his body, requiring a wheelchair and eventually a voice synthesizer to speak. Yet his desire to uncover nature’s secrets remained boundless.
In one of the most significant realizations of his career, Hawking reported in 1974 that black holes emit a faint glow of particles. This effect arises from quantum mechanics, which states that a sea of transient particles and antiparticles pervades all of space. These “virtual” particles usually annihilate in an instant, but if one of those particles is lost inside a black hole’s boundary, or event horizon, its partner can escape, producing what’s now known as Hawking radiation (SN: 5/31/14, p. 16).

As a result, black holes can gradually evaporate and disappear. This led to a still unresolved paradox: Throw an encyclopedia into a black hole and the information will eventually be lost. But according to quantum mechanics, information can never be destroyed.

Many solutions have been proposed for this problem, but none has stuck. In 2016, Hawking and colleagues proposed a path toward a solution: Black holes might have “soft hair,” low-energy particles that would retain information about what fell inside (SN: 2/06/16, p. 16). Hawking’s collaborators, including Strominger, are still working on the research. Standing at the interface between two seemingly incompatible theories — quantum mechanics, which describes the very small, and the general theory of relativity, which describes gravity — the quandary and its resolution may eventually help reveal a unified theory of quantum gravity.

Hawking made many other contributions, including studies of spacetime curvature during the Big Bang and the possibility that mini black holes might have formed in the universe’s infancy. Despite their groundbreaking nature, Hawking’s ideas remained largely theoretical, says Harvard theoretical astrophysicist Avi Loeb. Hawking radiation, for example, has never been directly detected. “That’s, unfortunately, why he didn’t get the Nobel Prize,” Loeb says.
Yet Hawking achieved a level of fame uncommon among scientists. He excelled at making abstruse science digestible to the public. With his books, most notably the best-selling A Brief History of Time, first published in 1988, Hawking inspired countless future scientists and science lovers (including the author of this article). Theoretical cosmologist Katie Mack of North Carolina State University in Raleigh first opened the book when she was about 10 years old. “I found it so fascinating at the time,” she says. “I found out that Stephen Hawking was called a cosmologist and so I said I wanted to be a cosmologist.” Hawking similarly motivated dozens of her colleagues, Mack says.

Hawking remained active in research even in the last months of his life. A paper on which he is a coauthor, which was updated in the weeks before his death, considered the physics of multiverses, the possibility that a slew of other universes exist in addition to our own.

A funeral was held for Hawking on March 31. Later this year, his ashes will be interred in Westminster Abbey in London, where they will rest alongside the remains of other famous British scientists, including Isaac Newton and Charles Darwin.

While the data was amassing, suddenly there came a tapping,
As of something gently rapping, rapping at LIGO’s door.

The source of a mysterious glitch in data from a gravitational wave detector has been unmasked: rap-tap-tapping ravens with a thirst for shaved ice. At the Advanced Laser Interferometer Gravitational-Wave Observatory, or LIGO, in the desert of Hanford, Wash., scientists noticed a signal that didn’t look like gravitational waves, physicist Beverly Berger said on April 16 at a meeting of the American Physical Society.

A microphone sensor that monitors LIGO’s surroundings caught the sounds of pecking birds on tape in July 2017, Berger, of the LIGO Laboratory at Caltech, said. So the crew went out to the end of one of the detector’s 4-kilometer-long arms to check for evidence of the ebony birds at the scene.

Sure enough, frost covering a pipe connected to the cooling system was covered in telltale peck marks from the thirsty birds. One raven, presumably seeking relief from the desert heat, was caught in the act. Altering the setup to prevent ice buildup now keeps the ravens from tapping, evermore.

After a two-day delay, the planet-hunting TESS telescope successfully launched into a clear blue sky at Cape Canaveral, Fla., at 6:51 p.m. EDT on April 18.

TESS, the Transiting Exoplanet Survey Satellite, is headed to an orbit between the Earth and the moon, a journey that will take about two months. In its first two years, the telescope will seek planets orbiting 200,000 nearby, bright stars, and identify the best planets for further study. TESS’ cameras will survey 85 percent of the sky by splitting it up into 26 zones and focusing on each zone for 27 days apiece.

TESS launched on a SpaceX Falcon 9 rocket. A previous launch attempt on April 16 was scrubbed so that SpaceX could run more tests on the rocket’s guidance, navigation and control system. SpaceX recovered the rocket’s first stage booster on an autonomous drone ship and hopes to reuse the rocket on a future launch.