The Core

Do virtual particles produce energy out of nothing?

The vacuum is defined to have zero energy. Therefore yes, the virtual particles violate the law of energy preservation. But the particles disappear again directly after (e. g. eighty attoseconds for a photon of orange light) and give the energy back to the vacuum.

And what if one virtual particle falls into a black hole?

If one particle of a pair of virtual particles falls into a black hole and the other one doesn't they can't react back to energy and the escaping one becomes a real particle leaving behind a lack of energy in the vacuum. Somehow this "hole" in the vacuum energy has to be filled again - even in quantum physics the law of energy preservation can't be disobeyed for a longer time. So this "hole" draws energy from that black hole. But what kind of energy does a black hole without any spin or charge have? It's mass! Thus a black hole loses some of its mass after Einstein's famous formula E = mc².

Maybe you have noticed that that's no proof that the energy has to originate from the black hole. In fact we can't really prove it without a lot of quantum physics (It depends on the tunnel-effect). You just have to swallow it as being true. Another, yet similar, way to explain the black hole's loss of mass is that the particle that gets sucked into the black hole gains a negative mass and thus the mass of the black hole decreases...

Is that called Hawking radiation?

Ring around a suspected black hole in galaxy NGC 4261. Date:Nov.1992. Courtesy of Space Telescope Science Institute.

You've got it! If one virtual particle falls into the black hole and the other one escapes, it escapes as Hawking radiation from the black hole. This radiation shows the same allocation as black body radiation. This assumes that black holes do have a temperature too. In fact this was proven by Bekenstein in 1972, before Hawking discovered that black holes also emit temperature radiation. As you see the radiation only seems to come from the inside of the black hole. In reality it originates just outside the black hole.

"Black holes aren't black - After Hawking they shine!"
Presented by Angie, Matthias and Thorsten
Team C007571,ThinkQuest Internet Challenge 2000.
Last modified: 2000-08-02.