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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Are Black Holes Two-Way Streets?
15 May 2008 (All day)
Black holes are just about the least friendly places in the universe. According to Einstein's theory of general relativity, they're so powerful that they warp space and time, and they've condensed so much matter and energy into a tiny point called a singularity that nothing, not even light, can escape. Getting sucked down a black hole should be a one-way trip. But is it?
Stephen Hawking thought so. Back in the 1970s, the eminent physicist hypothesized that a black hole eventually--over time scales lasting trillions of years--would evaporate into nothingness. The problem for Hawking's idea was that it clashed with quantum mechanics, of which one of the primary tenets is that information cannot be lost. Hawking could not reconcile the conflict, and a few years ago he recanted his position on information loss.
Now, physicists from Pennsylvania State University in State College have shown that Hawking was right to change his mind. Delving into a cousin of quantum mechanics called quantum gravity, Abhay Ashtekar and colleagues Victor Tavares and Madhavan Varadarajan calculate that singularities cannot exist. According to relativity, a singularity is essentially a frontier where spacetime ends. As such, nothing should be able to escape it. But complex calculations by Ashtekar's team show that singularities are not allowed by quantum gravity. That means that although the center of a black hole may be very, very dense, it's not so dense that it traps information forever. "Quantum spacetime doesn't end at a singularity," Ashtekar says.
The findings, reported in the 20 May issue of Physical Review Letters, are good news for quantum mechanics, because they support the idea that information cannot disappear permanently. But, by calling singularities into question, they spell trouble for relativity. If black holes are not singularities, then the continuum of spacetime described by Einstein must be only an approximation, says Ashtekar. That's not necessarily a bad thing. "[It] opens the door to a lot of new explorations," Ashtekar says. "They may lead to physics beyond Einstein."
The team's work is particularly fascinating because it provides a mathematical basis for actually looking into black holes, says astronomer Kimberly Weaver of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Black holes are such mysteries that this may be the only way we're going to be able to know what's going on inside them," she says. Weaver says astronomers will be looking for evidence that black holes evaporate. If so, "we might be able to see information coming out, and that would be really exciting."