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."
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.
In Colombia, Tax-Free Holidays Lead Critics To Decry 'COVID Friday' - NPR
Seeking ways to boost to its economy, Colombia has set aside three tax-free shopping days this summer. Critics fear they could become super spreader events for the coronavirus.
Shoppers browse at an electronics store in Bogotá, Colombia, on June 19. Shoppers flocked to Colombian shopping malls to take advantage of a day without value added tax, which triggered Black Friday-style shopping frenzies. Nathalia Angarita /Bloomberg via Getty Images After imposing one of the tightest coronavirus lockdowns in Latin America, Colombia is now searching for ways to jump-start its economy. One experiment is a series of tax-free shopping days, but critics fear they could turn out to be super-spreader events. At a time when the country is facing a spike in COVID-19 cases, urging Colombians to flock to stores and malls "sends an erroneous message," said Bogotá Mayor Claudia López. Sales tax in Colombia is a whopping 19%, so it was a big deal when the government designated three days this summer as tax holidays. The idea is to convince Colombians who had largely been confined to their homes for the past three months to venture out and open up their wallets. They did just that on Friday, June 19, the first of the three tax holidays. At many stores, mobs of shoppers turned out in a Black-Friday-like frenzy. Retail sales jumped five-fold, according to the Colombian government, prompting President Iván Duque to declare the event a roaring success. But the crowds were so large that social distancing went out the window and officials had to close down 86 stores nationwide. Bogotá city official Luis Gomez went into one crowded electronics store and personally ordered customers to leave. "People need to understand that it's not worth risking their lives for a discount," he told reporters. Colombia has registered more than 2,500 deaths from COVID-19, according to tracking by Johns Hopkins University. That is far fewer than neighboring Brazil, Peru and Ecuador. Still, the virus is surging in Latin America and health officials in Colombia say it's no time to slack off. Indeed, the shopping spree came just as Colombia registered its highest daily rate of new infections and deaths. That prompted López, the Bogotá mayor, to label the spending free-for-all "COVID Friday." She suggested the tax holidays should be for online shopping only. Guillermo García, a Bogotá lawyer who stayed home for the tax holiday, said it makes no sense for the government to first promote extreme caution through tight lockdown measures, only to then turn around and promote crowding in the name of boosting the economy. "I think all the sacrifices we made over the past three months will be lost," he said. So far, there are no plans to cancel the two remaining tax holidays scheduled for July 3 and July 19.