Eur. Phys. J. Plus (2021) 136: 1063
https://doi.org/10.1140/epjp/s13360-021-02062-y

Regular Article

The black hole energy and the energy of the other universe

Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-970, João Pessoa, PB, Brazil

^b jansen@fisica.ufpb.br

Received: 7 August 2021
Accepted: 11 October 2021
Published online: 24 October 2021

Abstract

Frames adapted to Kruskal and Novikov coordinate systems are used to compute the energy of the Schwarzschild black/white hole. It turns out that no regularization procedure is necessary if the right hypersurface of simultaneity is used. The importance of using a hypersurface that is consistent with the observers who “measure” the energy is discussed. The effect that the wormhole throat may have on the total energy inside this hypersurface is also discussed; the result shows that this energy becomes the famous $M{c}^2$ only when the throat pinches off completely. The energy of the other universe is calculated. It is shown that, because of reflections at the time and the radial axes of the Kruskal and Novikov frames with respect to the Schwarzschild frame, it is not possible to obtain the energy in both universes “simultaneously.”