Can gravity be repulsive?

TL;DR

This paper explores the possibility of gravitational repulsion near black holes, revealing that a freely falling test particle can appear to be repelled by a black hole from the perspective of an external observer, challenging conventional understanding.

Contribution

It demonstrates, inspired by Hilbert's observation, that gravity can appear repulsive in certain relativistic scenarios near black holes, a novel insight into gravitational behavior.

Findings

A freely falling particle can appear repelled by a black hole to an external observer.

The paper provides explanations for this relativistic gravity phenomenon.

It challenges the traditional view of gravity always being attractive.

Abstract

General Relativity has had tremendous successes on both theoretical and experimental fronts for over a century by now. However, the theory contents are far from being exhausted. Only very recently, with gravitational wave detection from colliding black holes, have we started probing gravity behavior in the strongly non-linear regime. Even today, black hole studies keep revealing more and more paradoxes and bizarre results. In this paper, inspired by David Hilbert's startling observation, we show that, contrary to the conventional wisdom, a freely falling test particle feels gravitational repulsion by a black hole as seen by an asymptotic observer. We dig deeper into this relativistic gravity surprising behavior and offer some explanations.