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I understand some parts of the theory, I've read from here https://phys.libretexts.org/Bookshelves/Astronomy__Cosmology/Supplemental_Modules_(Astronomy_and_Cosmology)/Cosmology/Carlip/Hawking_Radiation

What exactly is negative energy and how is it different from the "negative" or "positive" we use when talking about an electron or a proton? Why can negative energy only exist inside the blackhole?

Qmechanic
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Leon Raj
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  • I'm no kind of expert, but afaik it's not clear that negative energy is exactly anything (except for a solution to a model that doesn't purport to mean anything except for the predictions that it makes). Put another way, there are circumstances that can make the whole concept of energy not very well defined, but in those circumstances, if you pretend that something can have energy anyway, and that energy can be negative, you can make useful predictions. – g s Jul 23 '23 at 05:44
  • from your link, meaning of negative energy " The partner can then escape to infinity, and since it carries off positive energy, the energy (and thus the mass) of the black hole must decrease." In general if a body emits positive energy, it loses energy and that loss is called negative energy. – anna v Jul 23 '23 at 05:46
  • Hi Leon Raj. Welcome to Phys.SE. To reopen this post (v2) consider to only ask 1 question per post. – Qmechanic Jul 23 '23 at 05:50
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    Hi Leon. Your question is a duplicate of Black holes and positive/negative-energy particles. – John Rennie Jul 23 '23 at 06:08
  • For more on this see An explanation of Hawking Radiation – John Rennie Jul 23 '23 at 06:09
  • @JohnRennie thanks for the links, I think I'm getting a better picture of the concept, though I still have some troubles, but I'll get through. – Leon Raj Jul 23 '23 at 06:28
  • There is no "negative energy". A black hole spends its gravitational energy on creating a pair of particles. One particle falls to the black hole, so a half of the spent energy is returned. If the other particles flies away, its energy is not returned to the black hole, so the black hole becomes lighter. – safesphere Jul 24 '23 at 16:03
  • The "explanation" in the link in the question is wrong: "Sometimes one member of a pair crosses the horizon, and can no longer recombine with its partner" - This cannot happen, on our watch, because, in the coordinates of an external observer, nothing ever crosses the horizon. In general, any paper that mentions "crossing the horizon", as observed form outside, can be safely thrown to a recycling bin. – safesphere Jul 24 '23 at 16:20

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