There are some things in the universe that you simply can’t escape. Death. Taxes. Black holes. If you time it right, you can even experience all three at once.
Black holes are made out to be uncompromising monsters, roaming the galaxies, voraciously consuming anything in their path.
And their name is rightly deserved: once you fall in, once you cross the terminator line of the event horizon, you don’t come out. Not even light can escape their clutches.
But in movies, the scary monster has a weakness, and if black holes are the galactic monsters, then surely they have a vulnerability. Right?
In the 1970s, theoretical physicist Stephen Hawking made a remarkable discovery buried under the complex mathematical intersection of gravity and quantum mechanics: Black holes glow, ever so slightly, and, given enough time, they eventually dissolve.
Wow! Fantastic news! The monster can be slain! But how? How does this so-called Hawking Radiation work?
Well, general relativity is a super-complicated mathematical theory. Quantum mechanics is just as complicated.
It’s a little unsatisfying to respond to “How?” with “A bunch of math,” so here’s the standard explanation: the vacuum of space is filled with virtual particles, little effervescent pairs of particles that pop into and out of existence, stealing some energy from the vacuum to exist for the briefest of moments, only to collide with each other and return to nothingness.
Every once in a while, a pair of these particles pops into existence near an event horizon, with one partner falling in and the other free to escape.
Unable to collide and evaporate, the escapee goes on its merry way as a normal non-virtual particle.
Here’s the thing: I don’t find that answer especially satisfying, either.
For one, it has absolutely nothing to do with Hawking’s original 1974 paper, and for another, it’s just a bunch of jargon words that fill up a couple of paragraphs but don’t really go a long way to explaining this behavior.
It’s not necessarily wrong, just…incomplete.
One way or the other, as far as we can tell, black holes do dissolve. I emphasize the “as far as we can tell” bit because, like I said at the beginning, generality is all sorts of hard, and quantum field theory is a beast.
Put the two together and there’s bound to be some mathematical misunderstanding.
But with that caveat, we can still look at the numbers, and those numbers tell us we don’t have to worry about black holes dying anytime soon.
A black hole with the mass of the sun will last a wizened 10^67 years. Considering that the current age of our universe is a paltry 13.8 times 10^9 years, that’s a good amount of time.
But if you happened to turn the Eiffel Tower into a black hole, it would evaporate in only about a day. I don’t know why you would, but there you go.
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