8 Things You've Always Wanted To Know About Black Holes

5. Hawking Radiation And Other Short Stories

Stephen Hawking has basically spent that last 40 odd years creating problems for himself when it comes to black holes.

In 1974, he theorised that black holes give off Hawking radiation due to quantum fluctuations at the event horizon. The problem here is that the theory of Hawking radiation also suggests that the black hole will eventually die, but if a black hole dies, then that means that the information (that's the general term for the values of any matter) that it has spent its lifetime hoovering up simply disappears. This is a big no-no in physics as nothing can ever be destroyed, only transformed, and is known as the information paradox.

After 30 years of trying to solve his own paradox with all sorts of sci-fi theories involving shooting information off into other universes, Hawking eventually conceded that information does in fact leak back out of black holes. However, this information would have to be in a mangled up beyond recognition in order to obey the second law of thermodynamics which states that entropy can only ever increase or remain the same.

This, however, created another paradox known as the firewall paradox which would mean that the event horizon of a black hole, with all that escaping information, would essentially be a fiery death trap, something that violates general relativity.

This is where "apparent horizons" come into it. Apparent horizons trap light, much like event horizons, but they can fluctuate, providing an escape route for information, solving the firewall and information paradoxes.