Hawking Radiation: violate laws of conservation?

[simon009988]

I was thinking, when virtual particles come into exsistance and then one particle go into a black hole and the other gets emmited as hawking radiation and so the particles are no longer virtual and become "real" particles. Does this violate the laws of thermodynamics, and so is the mass/energy of the entire universe growing over time because of hawking radiation?

 

[Mk]

Don't virtual particles last for an infinitesimally small amount of time?

Wikipedia
Virtual particles are often popularly described as coming in pairs, a particle and antiparticle, which can be of any kind. These pairs exist for an extremely short time, and mutually annihilate in short order. In some cases, however, it is possible to boost the pair apart using external energy so that they avoid annihilation and become real particles. This is one way of describing the process by which black holes evaporate.
The restriction to particle-antiparticle pairs is actually only necessary if the particles in question carry a conserved quantity, such as electric charge, which is not present in the initial or final state. Otherwise, other situations can arise. For instance, the beta decay of a neutron can happen through the emission of a single virtual, negatively charged W particle that almost immediately decays into a real electron and antineutrino; the neutron turns into a proton when it emits the W particle. The evaporation of a black hole is a process dominated by photons, which are their own antiparticles and are uncharged.

Noted scientists, such as Stephen Hawking, have postulated that radiation emitting from black holes are the likely result of particle pairs where one has fallen into the event horizon of the black hole. The other, without a pair to annihilate it, travels away in the form of emitting radiation.

 

[GOD__AM]

The energy is conserved because the black hole loses mass equal to the particle that escaped. The anti-particle that gets pulled into the black hole annihilates it's opposite particle inside the black hole decreasing the mass there.

Thats how I understand it, but I'm far from an expert.

 

[simon009988]

The energy is conserved because the black hole loses mass equal to the particle that escaped. The anti-particle that gets pulled into the black hole annihilates it's opposite particle inside the black hole decreasing the mass there.

so does that mean when particles fall into a black hole they keep their identity as what ever particle they were and wait for an antiparticle? When the particles annihilate inside the black hole how can the energy escape from the annihilation from within the black hole?

 

[GOD__AM]

When the particles annihilate inside the black hole how can the energy escape from the annihilation from within the black hole?

It can't. The energy was released in the form of the real particle that escaped from the pair creation. Any annihilation taking place inside the black hole is un-observable as that energy cannot escape the event horizon.

 

[Claude Bile]

Does this violate the laws of thermodynamics, and so is the mass/energy of the entire universe growing over time because of hawking radiation?

On the contrary, without Hawking radiation, the second law of thermodynamics would be violated.

Consider a scenario whereby a disordered object falls into a black hole. As soon as the object passes the event horizon, the disorder is lost to the universe, causing entropy to decrease (a violation of the 2nd law of thermodynamics). Hawking's theory ensures that the disorder lost when an object falls into a black hole is returned to the universe via Hawking radiation, thus preserving the second law of thermodynamics.

This is how I understand it from what he has written in some of his literature.

Claude.

 

[simon009988]

On the contrary, without Hawking radiation, the second law of thermodynamics would be violated.
Consider a scenario whereby a disordered object falls into a black hole. As soon as the object passes the event horizon, the disorder is lost to the universe, causing entropy to decrease (a violation of the 2nd law of thermodynamics). Hawking's theory ensures that the disorder lost when an object falls into a black hole is returned to the universe via Hawking radiation, thus preserving the second law of thermodynamics.
This is how I understand it from what he has written in some of his literature.
Claude.

but doesn't a black hole have the maximun entropy physically possible

 

[NateTG]

I was thinking, when virtual particles come into exsistance and then one particle go into a black hole and the other gets emmited as hawking radiation and so the particles are no longer virtual and become "real" particles. Does this violate the laws of thermodynamics, and so is the mass/energy of the entire universe growing over time because of hawking radiation?

I think the best answer is that that particular explanation for Hawking radiation involves 'local' violations of the conservation laws. I believe that there actually other explanations for black hole radiation, but I'm not an expert in the field.
The Uncertainty Principle indicates (among other things) that the so-called conservation laws can be bent locally, for example, that it's possible to have a particle pop into existence spontaneously as long as an equal amount of mass, charge, and spin pops out of existence a short time later. I'm not going to get into interpretation issues, but you might think of it as a particle - un-particle pair, or as a particle skipping forward or backward in time. Now, it's concievable that the vacuum around a black hole borrows some mass from the vacuum, and then ends up taking the mass out of the black hole.
And, it turns out that according to the best theories we have, there will be a net flow of mass or energy out of the black hole due to this phenomenon. I don't know nearly enough to explain the particulars of the calculation, but it's out there on a variety of web sites.

 

[Claude Bile]

but doesn't a black hole have the maximun entropy physically possible

It was not the entropy of the black hole that was in question, it was the entropy of the rest of the universe.

Claude.

 

[simon009988]

It was not the entropy of the black hole that was in question, it was the entropy of the rest of the universe.
Claude.

but won't the entropy of the entire universe including the black hole have a net rise in entropy when things do fall in

 

[Claude Bile]

Yes, but the relationship between the properties of the black hole and its entropy was not well understood before Hawking. The theory of Hawking radiation went some way to resolving the original conundrum.

Claude.