It is known since Hawking that an observer "a rest" at some far distance of a black hole sees a thermal radiation emitted by the black hole. The mass of the black hole diminishes while it emmits the thermal flow of particles.(adsbygoogle = window.adsbygoogle || []).push({});

For a free falling observer there is no thermal radiation. So, for him the mass of the black hole may not diminish; it may remains constant.

However, the mass should be a well defined observable for both observers, so that they should agree with their observed value of the mass.

Can someone help to understand this paradox ?

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# Is the mass of a black hole diminishing for a free falling observer ?

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