The Sky at Night - Stephen Hawking on Black Holes
Stephen Hawking on Black Holes:
The programme looks at the latest understanding of black holes, featuring an interview with Stephen Hawking. Black holes are one of the greatest mysteries in the universe. They behave in a way that is contrary to laws of physics and one has never actually been seen. However, the recent detection of gravitational waves, as predicted by Einstein, proves that black holes exist and provides a way to investigate their remarkable behaviour and properties.
Stephen Hawking made headlines back in January 2016 when he told the world he'd found a possible solution to his black hole information paradox. Or in other words, he'd come up with a potential explanation for how black holes can simultaneously erase information and retain it.
Our original understanding of black holes, according to Einstein's generally theory of relativity, is that everything that crosses the event horizon - the boundary of a black hole - is lost forever. Even light can't escape its clutches, which is why black holes are called black holes (and also why it's impossible for us to actually see one).But then in the 1970s, Hawking proposed that radiation actually can escape from a black hole, because of the laws of quantum mechanics. Put very simply, he suggested that when a black hole swallows one half of a particle-antiparticle pair, the other particle radiates away into space, stealing a little energy from the black hole as it leaves.
Because of this, eventually, black holes can disappear, and the only remaining trace would be the electromagnetic radiation they emitted - which is known as 'Hawking radiation'.The problem is that, according to Hawking's best calculations, that radiation would contain no useful information about what the black hole ate - the information swallowed up would have been lost forever. And that doesn't gel with our understanding of modern physics, which states that it's always possible to reverse time. In theory, at least, processes in the Universe will look the same if they're running forwards or backwards.
