Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: chris on 12/05/2017 04:02:13

Title: How does Hawking radiation cause a reduction in a black holes mass?
Post by: chris on 12/05/2017 04:02:13

Barry, in Australia, has been in touch to ask:

How does Hawking radiation cause a reduction in a black holes mass? If, as I've read, it is caused by virtual particle pairs forming just outside the event horizon one of which is swallowed and one of which escapes wouldn't this cause a slight gain in mass? Please help me understand.

What do you think?

Title: Re: How does Hawking radiation cause a reduction in a black holes mass?
Post by: jeffreyH on 12/05/2017 12:22:33

Think about what would normally happen with the spontaneous appearance of a particle, anti-particle pair. They annihilate immediately. Being separated by the barrier of the event horizon this cannot happen. It all depends upon what happens to each particle.

Title: Re: How does Hawking radiation cause a reduction in a black holes mass?
Post by: PmbPhy on 12/05/2017 22:44:57

Quote from: jeffreyH on 12/05/2017 12:22:33

Think about what would normally happen with the spontaneous appearance of a particle, anti-particle pair. They annihilate immediately. Being separated by the barrier of the event horizon this cannot happen. It all depends upon what happens to each particle.

One particle escapes while the other is captured by the black hole. The entire energy is zero. The particle that escapes has positive energy while the one that's captured has negative energy. The negative energy decreases the total amount of energy in the black hole and the mass decreases according to the mass equivalence of that energy.

Title: Re: How does Hawking radiation cause a reduction in a black holes mass?
Post by: jeffreyH on 12/05/2017 23:56:23

Now that is interesting Pete. That is the best explanation I have heard.