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When a photon tries to leave a black hole, it is redshifted until the wave length is infinite and the photon disappears(?).

Could this also happen the other way round, that a (non existent) photon with an infinite wave length is blueshifted into existence by a massive object? If that's true could this explain the background radiation?

I mean that we see radiation within our galaxy that comes from the outside, but does not really exists outside, because on the outside the wave length of this radiation is infinite.

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    $\begingroup$ I think you are looking for Hawking radiation: en.wikipedia.org/wiki/Hawking_radiation $\endgroup$ – user1937198 Mar 12 at 21:41
  • $\begingroup$ @user1937198, I'm looking for the opposite of hawking radiation. If heavy objects can pull photons into existence, that would mean that black holes become more massive by them self. $\endgroup$ – Cosinus Mar 13 at 11:36
  • $\begingroup$ @Cosinus - Infinite blueshifts (which is what is needed to give a finite wavelength to an infinitely long-wavelength photon) are only found inside black holes. But that means their effects cannot propagate outside the event horizon. The most general cause of particles appearing like this is the Unruh effect, but it still obeys energy conservation. $\endgroup$ – Anders Sandberg Mar 13 at 12:37
  • $\begingroup$ @AndersSandberg, I'm not sure about that such things can only happen behind the event horizon, because when a bullet is shot into the sky it's kinetic energy will at some point be infinitely low it depends on the initial velocity when or if that happens. Equivalent to photons, the altitude when the frequency of a photon hits zero, depends on the initial frequency. (Or doesn't it?) $\endgroup$ – Cosinus Mar 13 at 13:28
  • $\begingroup$ @AndersSandberg, about the energy conservation, when a photon can get redshifted out of existence, the reverse must also apply in some way too. But maybe my understanding of photons is just wrong, when I think about potential energy of empty space $\endgroup$ – Cosinus Mar 13 at 13:34

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