i am trying to understand hawking radiation. in wikipedia, it states:(adsbygoogle = window.adsbygoogle || []).push({});

"In order to preserve total energy, the particle which fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process the black hole loses mass, and to an outside observer it would appear that the black hole has just emitted a particle."

please explain why the particle which falls into the BH must have negative energy. thanks.

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# Another hawking radiation question

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