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When a star gets too close to a black hole, sparks fly. And, potentially, so do subatomic particles called neutrinos.

A dramatic light show results when a supermassive black hole rips apart a wayward star. Now, for the second time, a high-energy neutrino has been spotted that may have come from one of these “tidal disruption events,” researchers report in a study accepted in Physical Review Letters.

These lightweight particles, which have no electric charge, careen across the cosmos and can be detected upon their arrival at Earth. The origins of such zippy neutrinos are a big mystery in physics. To create them, conditions must be just right to drastically accelerate charged particles, which would then produce neutrinos. Scientists have begun lining up likely candidates for cosmic particle accelerators. In 2020, researchers reported the first neutrino linked to a tidal disruption event (SN: 5/26/20). Other neutrinos have been tied to active galactic nuclei, bright regions at the centers of some galaxies (SN: 7/12/18).
Discovered in 2019, the tidal disruption event reported in the new study stood out. “It was extraordinarily bright; it’s really one of the brightest transients ever seen,” says astroparticle physicist Marek Kowalski of Deutsches Elektronen-Synchrotron, or DESY, in Zeuthen, Germany.

Transients are short-lived flares in the sky, such as tidal disruption events and exploding stars called supernovas. Further observations of the brilliant outburst revealed that it shone in infrared, X-rays and other wavelengths of light.

Roughly a year after the flare’s discovery, the Antarctic neutrino observatory IceCube spotted a high-energy neutrino. By tracing the particle’s path backward, researchers determined that the neutrino came from the flare’s vicinity.

The matchup between the two events could be a coincidence. But when combined with the previous neutrino that was tied to a tidal disruption event, the case gets stronger. The probability of finding two such associations by chance is only about 0.034 percent, the researchers say.

It’s still not clear how tidal disruption events would produce high-energy neutrinos. In one proposed scenario, a jet of particles flung away from the black hole could accelerate protons, which could interact with surrounding radiation to produce the speedy neutrinos.

‘We need more data … in order to say that these are real neutrino sources or not,” says astrophysicist Kohta Murase of Penn State University, a coauthor of the new study. If the link between the neutrinos and tidal disruption events is real, he’s optimistic that researchers won’t have to wait too long. “If this is the case, we will see more.”

But scientists don’t all agree that the flare was a tidal disruption event. Instead, it could have been an especially bright type of supernova, astrophysicist Irene Tamborra and colleagues suggest in the April 20 Astrophysical Journal.

In such a supernova, it’s clear how energetic neutrinos could be produced, says Tamborra, of the Niels Bohr Institute at the University of Copenhagen. Protons accelerated by the supernova’s shock wave could collide with protons in the medium that surrounds the star, producing other particles that could decay to make neutrinos.

It’s only recently that observations of high-energy neutrinos and transients have improved enough to enable scientists to find potential links between the two. “It’s exciting,” Tamborra says. But as the debate over the newly detected neutrino’s origin shows, “at the same time, it’s uncovering many things that we don’t know.

The pandemic has entered a murky stage, and social norms are quickly shifting, something I’ve thought a lot about lately. Many people are testing at home, or not at all. Here in Vermont, where I live, you can pick up a type of PCR test that can be taken at home. But state officials both here and elsewhere are no longer carefully monitoring the results of these tests, which means that the actual spread of coronavirus in the U.S. population remains unclear (SN: 4/22/22).

For a few weeks, rumors of a stealth COVID-19 wave have been circulating both in the media and on my Twitter feed. Now cases and hospitalizations are rising, as are the levels of coronavirus in wastewater. That suggests that more cases, and ultimately deaths, could follow.
Even with rising caseloads and a vaccination rate that has flatlined at about 66 percent of the eligible population, the American public has largely begun to move on from the COVID-19 crisis. People are shedding their masks, eating out, attending concerts, traveling to far-flung locations, having large, indoor weddings and doing all the social things that people tend to do when left to their own devices.

The 2,600-person White House Correspondents’ Association dinner late last month is a case in point. Just as host Trevor Noah prophesied, many of those in attendance have since tested positive for COVID-19, including U.S. Secretary of State Antony Blinken and reporters from NBC, ABC, the Washington Post, Politico and other media outlets. And those who almost certainly knew better — cue White House Coronavirus Response Coordinator Ashish Jha — nonetheless made an appearance.

Myriad quirks related to human behavior undoubtedly underpin these arguably poor choices. The Decision Lab website has a list of the biases and mental shortcuts people use to make decisions. The one that caught my eye is social norms. This particular quirk outlines what behaviors people deem appropriate in a given situation.

I started thinking about social norms while writing a feature on how to get people in the United States to eat less meat when the practice is so, well, normal (SN: 5/11/22). Social norms, my research informed me, vary with the group one is hanging out with and one’s environs. “We rapidly switch our perspective depending on the context of the situation we find ourselves in,” writes marketing expert John Laurence on the Decision Lab site.

I might have found this idea of rapid switching suspect had I not recently experienced the phenomenon. My husband’s Disney-phile brother and his wife had been planning a family reunion in Disney World in Florida since the start of the pandemic. And I, a curmudgeonly sort not prone to feeling the magic, long ago agreed to go on the condition that other people do all the planning. And so it was, after multiple COVID-related postponements, that my kids, my husband and I landed in Orlando on a blisteringly hot April day.

Disney normal, I soon learned, bore little resemblance to Vermont normal. This was obvious immediately from people’s attire. All around me parents and kids dressed in coordinated outfits and matching Mickey Mouse ears. (Apologies to my kids — your mom missed the fashion memo.)
Social norms almost certainly arose to foster cohesion among our earliest ancestors, who needed solidarity to hunt large prey, share limited resources and ward off predators and enemy tribes. In-group norms also provide humans with a sense of belonging, which research suggests is vital for our overall health. A meta-analysis of more than 3.4 million people followed for an average of seven years showed that the likelihood of dying during the study period increased by 26 percent for participants who reported feeling alone (SN: 3/29/20).

Not surprisingly, then, one of the strongest drivers of human behavior is to seek out belonging. At Disney, that quest means blocking out the reality that exists just outside the fiefdom. Wars, climate crises, political fighting and the like have no place within those magical walls. Nor do reminders of a global health crisis that, according to the latest World Health Organization estimates, has thus far killed nearly 15 million people worldwide.

Within Disney’s walls, throngs of mostly maskless tourists packed onto iconic rides and into restaurants. When halfway through our trip, a Florida judge ruled that masks could not be mandated on public transit, nary a mask was to be seen on buses shuttling people to the Magic Kingdom and Epcot Center. And everywhere, all the time, people seemed to be coughing, sniffling or blowing their noses.

As a science reporter covering COVID-19, I certainly knew that I should keep my mask on. And yet, my resolve soon faltered. My kids pointed out that no one else was masking, not even my typically rule-following relatives. Donning my mask meant confessing that I was not reveling in the sparkle and glitz and magic and making all too obvious to my beloved extended family that I did not, in fact, belong. I kept my face covering in my pocket.

Humans’ tendency toward conformity is not all bad. In a now classic study from the 1980s, researchers investigated how to reduce water consumption in drought-prone California. Signs at the University of California, Santa Cruz asking students to turn off the shower while soaping up led to only 6 percent compliance. So researchers recruited male students to serve as norm-setting role models. These role models would hang out in the communal shower until they heard another student come in, and then soap up with the water off. When one role model soaped with the shower off, roughly half of the unwitting students also began turning off their faucets at soaping time. Compliance jumped to 67 percent when two role models followed the sign.

But conformity can also distort how we make decisions. For instance, in the summer of 2020, when the pandemic was still new, researchers asked 23,000 people in Mexico to predict how a fictional woman named Mariana would decide whether or not to attend a birthday party. Most participants believed Mariana should not attend. But when they read a sentence suggesting her friends would attend or that others approved of the party, their predictions that Mariana would also go increased by 25 percent, researchers reported in PLOS ONE.

My decision to conform to Disney normal ended predictably — with a positive COVID-19 test. After weeks of coughing and sleepless nights, though, my frustration is less directed at myself than at political leaders who so blithely ignore both epidemiology and human behavior research and tell us to live like it’s 2019. It’s not. Nor is it 2020 or 2021. It’s the murky year known as 2022. And the rules of behavior that bolster our social norms — such as role models who refrain from large, indoor, unmasked gatherings, and leaders who uphold mask mandates on public transit to protect the most vulnerable — should reflect this liminal space.

A molar tooth from Southeast Asia probably belonged to a member of a cryptic group of Stone Age hominids called Denisovans, researchers say.

If so, this relatively large tooth joins only a handful of fossils from Denisovans, who are known from ancient DNA pegging them as close Neandertal relatives.

Analyses of the tooth’s internal structure and protein makeup indicate that the molar came from a girl in the Homo genus. She died between the ages of 3½ and 8½, paleoanthropologist Fabrice Demeter of the University of Copenhagen and colleagues say.
A Denisovan molar that dates to at least 160,000 years ago was previously found on the Tibetan Plateau (SN: 12/16/19). The newly discovered tooth strongly resembles that other molar, indicating that the new find is probably Denisovan too, the team reports May 17 in Nature Communications. Before the Tibetan Plateau tooth, all known fossils from the mysterious hominids had been found in Siberia.

Estimated ages of sediment and fossil animal bones in Tam Ngu Hao 2, or Cobra Cave, in Laos place the tooth found there between 164,000 and 131,000 years old.

It’s possible that the Cobra Cave tooth represents a Neandertal or someone with Denisovan and Neandertal ancestry (SN: 8/22/18), Demeter says. His group hopes to extract DNA from the fossil, which could clarify its evolutionary status.

It now appears that at least five Homo species, including Denisovans, inhabited Southeast Asia between roughly 150,000 and 40,000 years ago, Demeter says. Others include Homo sapiens, Homo erectus (SN: 12/18/19), Homo luzonensis (SN: 4/10/19) and Homo floresiensis (SN: 3/30/16), also known as hobbits, he contends.

Still, some researchers regard Denisovans as one of several closely related, ancient Homo populations rather than a distinct species (SN: 6/25/21). Whatever evolutionary ID Denisovans actually held, the Cobra Cave tooth adds to suspicions that the hominids inhabited Southeast Asia’s tropical forests as well as Central Asia’s cold mountain ranges and Siberia.