Is Quantum Gravity Necessary?

TL;DR

This paper explores whether gravity must be quantized or if it can remain fundamentally classical, discussing theoretical challenges and proposing experimental tests to determine its true nature.

Contribution

It reviews the theoretical difficulties of mixed classical-quantum gravity models and suggests experimental approaches to test the classicality of gravity.

Findings

Theoretical arguments against classical-quantum models are strong but inconclusive.

Proposes experimental tests exploiting nonlinearity in classical-quantum coupling.

Highlights the importance of experimental evidence in resolving the quantum nature of gravity.

Abstract

In view of the enormous difficulties we seem to face in quantizing general relativity, we should perhaps consider the possibility that gravity is a fundamentally classical interaction. Theoretical arguments against such mixed classical-quantum models are strong, but not conclusive, and the question is ultimately one for experiment. I review some work in progress on the possibility of experimental tests, exploiting the nonlinearity of the classical-quantum coupling, that could help settle this question.