The Many Definitions of a Black Hole

TL;DR

The paper explores the diverse definitions of black holes across physics fields, arguing that this diversity fosters progress and interdisciplinary understanding despite potential translation challenges.

Contribution

It analyzes various black hole definitions, discusses their implications, and argues that the lack of a universal definition can be beneficial for scientific progress.

Findings

Diverse definitions are prevalent across physics disciplines.

The lack of a single definition facilitates varied research approaches.

Translating results between fields requires careful interpretation.

Abstract

Although black holes are objects of central importance across many fields of physics, there is no agreed upon definition for them, a fact that does not seem to be widely recognized. Physicists in different fields conceive of and reason about them in radically different, and often conflicting, ways. All those ways, however, seem sound in the relevant contexts. After examining and comparing many of the definitions used in practice, I consider the problems that the lack of a universally accepted definition leads to, and discuss whether one is in fact needed for progress in the physics of black holes. I conclude that, within reasonable bounds, the profusion of different definitions is in fact a virtue, making the investigation of black holes possible and fruitful in all the many different kinds of problems about them that physicists consider, although one must take care in trying to translate results between fields.