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Time Travel Theoretically Possible Without Leading To Paradoxes, Researchers Say - NPR
In the peer-reviewed journal article, University of Queensland physicists say time is essentially self-healing. Changes in the past wouldn't necessarily cause a universe-ending paradox. Phew.
A dog dressed as Marty McFly from Back to the Future attends the 25th Annual Tompkins Square Halloween Dog Parade in 2015. New research says time travel might be possible without the problems McFly encountered. Timothy A. Clary/AFP via Getty Images "The past is obdurate," Stephen King wrote in his book about a man who goes back in time to prevent the Kennedy assassination. "It doesn't want to be changed." Turns out, King might have been onto something. Countless science fiction tales have explored the paradox of what would happen if you do something in the past that endangers the future. Perhaps one of the most famous pop culture examples is Back to the Future, when Marty McFly went back in time and accidentally stopped his parents from meeting, putting his own existence in jeopardy. But maybe McFly wasn't in much danger after all. According a new paper from researchers at the University of Queensland, even if time travel were possible, the paradox couldn't actually exist. Researchers ran the numbers, and determined that even if you make a change in the past, the timeline would essentially self-correct, ensuring that whatever happened to send you back in time would still happen. "Say you travelled in time, in an attempt to stop COVID-19's patient zero from being exposed to the virus," University of Queensland scientist Fabio Costa told the university's news service. "However if you stopped that individual from becoming infected that would eliminate the motivation for you to go back and stop the pandemic in the first place," said Costa, who co-authored the paper with honors undergraduate student Germain Tobar. "This is a paradox an inconsistency that often leads people to think that time travel cannot occur in our universe." A variation is known as the "grandfather paradox" in which a time traveler kills their own grandfather, in the process preventing the time traveler's birth. The logical paradox has given researchers a headache, in part because according to Einstein's theory of general relativity, "closed time-like curves" are possible, theoretically allowing an observer to travel back in time and interact with their past self and potentially endangering their own existence. But these researchers say that such a paradox wouldn't necessarily exist, because events would adjust themselves. Take the coronavirus patient zero example. "You might try and stop patient zero from becoming infected, but in doing so you would catch the virus and become patient zero, or someone else would," Tobar told the university's news service. In other words, a time traveler could make changes but the original outcome would still find a way to happen. Maybe not the same way it happened in the first timeline; but close enough so that the time traveler would still exist, and would still be motivated to go back in time. "No matter what you did, the salient events would just recalibrate around you," Tobar said. The paper, "Reversible dynamics with closed time-like curves and freedom of choice," was published last week in the peer-reviewed journal Classical and Quantum Gravity. The findings seem consistent with another time travel study published this summer in the peer-reviewed journal Physical Review Letters. That study found that changes made in the past won't drastically alter the future. Best-selling science fiction author Blake Crouch, who has written extensively about time travel, said the new study seems to support what certain time travel tropes have posited all along. "The universe is deterministic and attempts to alter Past Event X are destined to be the forces which bring Past Event X into being," Crouch told NPR via email. "So the future can affect the past. Or maybe time is just an illusion. But I guess it's cool that the math checks out."
Flu Season Was Weirdly Mild In Southern Hemisphere. Scientists Want To Know Why : Goats and Soda - NPR
So far this year, flu infections are way down in the Southern Hemisphere. Scientists want to know why — and what it means for the Northern Hemisphere as their flu season looms.
People wait for a flu vaccine in May in Manaus, Brazil. The flu season had a surprisingly low count of influenza cases in the Southern Hemisphere, and researchers are trying to figure out the role coronavirus precautions might have played. Andre Coelho/Getty Images This year's flu season in the Southern Hemisphere was weirdly mild. A surprisingly small number of people in the Southern Hemisphere have gotten the flu this year, probably because the public health measures put in place to fight COVID-19 have also limited the spread of influenza. That makes public health experts hopeful that the U. S. and other northern countries might be spared the double whammy of COVID-19 and a bad flu season this winter. Still, they warn against complacency and say people still need to get vaccinated against the flu. "Because influenza surprises us. Viruses surprise us," says Kanta Subbarao, director of the World Health Organization's Collaborating Centre for Reference and Research on Influenza in Melbourne, Australia. "We are sort of seeing very little influenza activity in the Southern Hemisphere, but that doesn't allow me to predict that that will be the case for the Northern Hemisphere." The tropics around the globe's equator can haveflu year-round. The temperate zones of the north and south, in contrast, see cases of seasonal influenza rise and peak during the winter. That means doctors in the Southern Hemisphere typically start seeing flu in May or June. The number of infections there is greatest in July or August. In the Northern Hemisphere, cases start to rise in the fall and peak between December and February. That's why, as COVID-19 started spreading earlier this year, public health officials in the southern parts of the world worried that their health care systems would soon be overwhelmed. Just when they were expecting to see the normal burden of hospitalizations of seasonal flu, this new respiratory illness could be upon them. "The countries took it very, very seriously," says Sylvain Aldighieri, the incident manager for COVID-19 with the Pan American Health Organization. "They bought more vaccine, they vaccinated more people during the pre-flu season." Then they waited for influenza to cases to start rising as usual. They waited ... and waited ... and waited. "Now we are well advanced during the flu season in the south, and we have not seen any spike, any upsurge of flu," Aldighieri says. Flu hasn't totally disappeared, but it's way down. For example, he says, consider 3,391 clinical samples that were taken from patients with an acute respiratory illness during a three-week period in the middle of winter in Chile. "Zero were positive for influenza," Aldighieri says, explaining that he'd normally expect to see hundreds test positive for flu. Chile isn't alone. Other countries are having a similar experience. "Based on what we've seen in the Southern Hemisphere, and I would say this is true of all through the Southern Hemisphere South America, Africa, Australia, New Zealand, all across this region there's been very little influenza activity," Subbarao says. No one can say for sure what's responsible for this unusual flu season, but it seems likely that all the changes in people's movements and behaviors, because of COVID-19, must have played a major role. "The restriction on travel is a big, big element," says Subbarao, who notes that the mask-wearing, hand-washing and social distancing would also be expected to prevent flu transmission. Flu researchers say that watching this all play out on the global scale is absolutely fascinating from a scientific point of view, but that no one can rest easy when it comes to influenza, especially in these days of the COVID-19 pandemic. "We don't know why this is happening. It's a good thing; we're going to assume it's all of the control measures, but we don't need a major flu epidemic on top of this," says Stacey Schultz-Cherry, a flu researcher at St. Jude Children's Research Hospital in Memphis, Tenn. "This is one of those years that it is more important than ever to get your flu vaccine." Scientists usually decide what will go into next year's flu vaccine by studying the strains that are currently circulating and using that data to make predictions. Even though flu cases are oddly low so far, they'll still be able to do that, Schultz-Cherry says. "I think if it had disappeared completely, we'd be in a very different ballgame. But it hasn't there's still flu out there," she says, emphasizing that this is exactly why people need to stay vigilant and get vaccinated. Aldighieri adds, "If the Northern Hemisphere doesn't implement measures comparable to the south, the Northern Hemisphere will be at risk to have a combined epidemic, COVID-19 and influenza." Already in the U. S., more than 175,000 people have died of COVID-19. The Centers for Disease Control and Prevention says that in a typical flu season, tens of thousands of people in this country die of influenza.
Ancient 'Terror Crocodiles' Preyed On Dinosaurs - NPR
A new study reveals there were multiple species of Deinosuchus, the giant crocodylians that lived 75 million years ago. They were among the largest predators in the ecosystem and ate dinosaurs.
A new study of Deinosuchus or "terror crocodiles," led by Adam Cosette, offers a fuller picture of the ancient creature from head to tail. Cossette said Deinosuchus had large, robust teeth, ranging from six to eight inches long, as shown in the photo. Adam Cossette Enormous "terror crocodiles" once roamed the earth and preyed on dinosaurs, according to a new study revisiting fossils from the gigantic Late Cretaceous crocodylian, Deinosuchus. The research, published in the Journal of Vertebrate Paleontology, reiterates that Deinosuchus were among the largest crocodylians ever in existence, reaching up to 33 feet in length. New in this study is a look at the anatomy of the Deinosuchus, which was achieved by piecing together various specimens unknown until now, giving a fuller picture of the animal. Adam Cossette, a vertebrate paleobiologist at the New York Institute of Technology College of Osteopathic Medicine at Arkansas State University, led the study that corrected some misunderstandings about the Deinosuchus. "Until now, the complete animal was unknown," Cossette said. "These new specimens we've examined reveal a bizarre, monstrous predator with teeth the size of bananas." Past studies on cranial remains and bite marks on dinosaur bones led paleontologists to believe the massive Deinosuchus were an opportunistic predator, according to the press release. Fossil specimens now make it clear that Deinosuchus did indeed have the head size and jaw strength to have its pick of prey, including large dinosaurs. "Deinosuchus was a giant that must have terrorized dinosaurs that came to the water's edge to drink," Cossette said. University of Iowa vertebrate paleontologist Christopher Brochu, the study's co-author, said another important realization from the paper is that there were several species of Deinosuchus that roamed North America between 75 and 82 million years ago. The study notes Deinosuchus hatcheri and Deinosuchus riograndensis lived in the west, from what is now Montana to northern Mexico. Deinosuchus schwimmeri lived in the east from New Jersey to Mississippi. "Some of them were separated by a seaway that at one point cut North America in half from what's now the Gulf of Mexico up to the Arctic Ocean," Brochu said. "And that may have driven what we call speciation. There might have been one ancestral dinosaur form in North America, and then the seaway cut that population in half and on one side it evolved in one direction, the other side in a different direction." Despite the nickname "terror crocodiles," Brochu said Deinosuchus were more closely related to alligators than to crocodiles but "didn't look like either one of them." Deinosuchus had a snout that was long and broad, with the front appearing inflated unlike any other living or extinct crocodylian. On the tip of the snout is a large pair of holes. Researchers are still unsure of their function. Both Brouchu and Cossette assert this paper disproves the idea that crocodylians are living fossils, or in other words, animals which never evolved. "There's this concept out there that crocodylians are unchanging forms," Brochu said. "That they appear way back in the distant past and haven't changed since the days of the dinosaurs. That is simply not true." If you look at the modern species of crocodylian, Cossette explained, there are just a handful and they all look and act very similar. But if you look at the fossil record there is diversity of size, shape, diet and lifestyle. "Most people think crocodiles haven't changed in 75 million years," Cossette said. "This study shows that the ancestors of today's American alligator didn't look anything like them." "Crocodiles are actually these incredibly dynamic creatures that have experienced incredible evolutionary histories, have lived in places that modern crocodiles don't live, done things that modern crocodiles don't do and have grown to sizes that modern crocodiles never achieve. That I think is the cool part [of the study], at least for me," Cossette added.