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jaketodd

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Thanks,

Jake

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- Thread starter jaketodd
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- #1

jaketodd

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Thanks,

Jake

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==========

Of course I may be wrong, as it seems to me that particles and anti-particles would have an equal chance of entering the hole, thus negating each other instead of anything in the hole. What am I missing?

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jaketodd

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George Jones

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==========

Of course I may be wrong, as it seems to me that particles and anti-particles would have an equal chance of entering the hole, thus negating each other instead of anything in the hole. What am I missing?

This comes up often; see

When virtual matter-antimatter pairs are created, the probability that the antimatter particle has positive energy is equal to the probability that the matter particle has positive energy, i.e., both probalilities are 1/2.

Hawking radiation does not come about because antimatter particles sometimes fall into black holes; it comes about because negative-energy particles (both matter and animatter) sometimes fall into black holes. Some popular-level treatments of black holes obscure this, and even sometime get this completely wrong.

Sometimes it is difficult to give accurate non-mathematical descriptions of processes that involve advanced physics. This is particularly true for Hawking radiation - it is very hard to see the correspondence between the non-mathematical description involving virtual matter-animatter pairs and the actual mathematical description.

Steve Carlip is a physicist who tries hard to make physical concepts clear, both for laypersons and for experts. You should read his non-mathematical description of Hawking radiation, which is more challenging than most non-mathematical descriptions, but which also is more accurate than most non-mathematical descriptions. If you have questions about his description, just post them.

What happens, very roughly, is this. Energy is associated with time and spatial momentum is associated with space. When an matter-antimatter pair of virtual particles is created *outside* the event horizon, they can become a little bit separated in the time that the Heisenberg uncertainty principle allows them to live. Tidal forces caused by the curvature of spacetime help them to separate, and, sometimes, the negative-energy particle (which could be either matter or anitimatter) wanders over the event horizon and into the black hole. Inside the event horizon, the roles of time and space coordinates get interchanged. Thus, according to what I wrote above, the roles of energy and spatial momentum get interchanged. What was negative energy becomes a negative spatial component of a local (for an observer inside the horizon) momentum vector. Only a virtual particle can have negative energy, while any particle, real or virtual, can have a negative component of spatial momentum.

Bottom line: the whole process can become a real process. In this real process, an observer outside a black hole "sees" the black hole hole swallow a negative-energy particle while emiitting a positve energy particle (the other member of the matter-antmatter pair). The balck hole radiates.

Regards,

George

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- #6

George Jones

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From the link that I gave,

Steve Carlip said:Note that this doesn't work in the other direction -- you can't have the positive-energy particle cross the horizon and leaves the negative- energy particle stranded outside, since a negative-energy particle can't continue to exist outside the horizon for a time longer than h/E. So the black hole can lose energy to vacuum fluctuations, but it can't gain energy.

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