Eli5 What is “Hawkings Radiation”?

Question

This was partially inspired by the event horizon post, I’ve heard of Hawkings radiation recently but don’t understand it, any help?

In: Physics

Answer 1

Ok you hear a lot about virtual particles its nonsense but sometimes its useful nonsense. When it comes to Hawking Radiation I think its not useful nonsense.

So quantum fluctuations. They are a thing becaue we can’t say a quantum field is on zero energy state, you know there is always a bit of uncertainty. It averages out to zero. Think of it like waves of particles and waves of antiparicles they cancel each other to make the fields zero. (Note that regular fluctuations dont really make particles.)

So Nick Lucid from the Science Asylum made a great video about it with a pretty good analogy.

Imagine quantum fluctuations as a wave, it is a wave so it’s not that hard. Now imagine this wave is a string waving. There are frequencies that the string likes and dislikes. It likes frequencies that fill the string with whole periods. These are the natural frequencies of the string. Now pinch a point on the string. Its now a fixed point so there are only a certain number of frequencies left for the string.

A black hole does something similar to quantum fluctuations. It creates a fixed point so the waves that all came together to cancel in front of the black hole no longer cancel on the other side of the black hole as some of the waves are messed up by the black hole. So particles can pop into existence. This doesn’t necessarily happen on the edge of the event horizon but somewhere near the black hole.

Hawking Radiation can be any particle but its almost always photons. It’s easier to escape from a back hole if you travel at light speed. The light is really not gonna be localised though, its almost always super large radio waves. These carry away a tiny bit of energy from the only available source which is the balck hole itself.

So as HR happens the back hole gets lighter and the event horizon shrinks. HR gets faster as the black hole gets smaller and after an unreasonably large amount of time the black hole explodes.