The physical nature of the event horizon in the Schwarzschild black hole solution

This study explores the relationship between the Schwarzschild metric and alternative metrics used to describe the gravitational field of a black hole in free space. While it is well-established that an infinite number of coordinate systems can be employed in general relativity, we demonstrate that the black hole solution is unique when expressed in a physically meaningful (proper) coordinate system. Notably, this coordinate system differs from the Schwarzschild metric due to the distinction between the true physical distance R and the Schwarzschild coordinate distance r. Consequently, the event horizon, commonly associated with the Schwarzschild solution, is shown to be a coordinate artefact of the chosen covariant metric tensor rather than a coordinate-invariant physical feature. As a result, no boundary prevents outgoing photons from escaping the black hole’s vicinity. This finding challenges the mainstream interpretation but remains fully consistent with general relativity. Moreover, it is supported by numerical modelling of light rays near a black hole. By reconsidering the existence of event horizons, this work offers potential resolutions to long-standing issues in black hole formation theories and the emission of electromagnetic and gravitational waves from black holes.

Graphical abstract