Can we ever detect the graviton?

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2024-10-21 04:00:04

A graviton $G$ is a theoretical quantum of the gravitational field, which presumably exists if gravity can indeed be quantized. There remains an important question regarding this fundamental particle: Can we ever detect a single graviton?

Sadly, the answer is almost certainly not. This question occupied renowned physicist Freeman Dyson for some time, which puts us in good company. Let us explore some of the reasons why graviton detection is so elusive.

Rothman, T., and S. Boughn. “Can gravitons be detected?” Foundations of Physics 36 (2006): 1801–1825. 10.1007/s10701-006-9081-9 arXiv:gr-qc/0601043

Dyson, F. “Is a graviton detectable?” International Journal of Modern Physics A 28.25 (2013): 1330041. 10.1142/S0217751X1330041X

To demonstrate why the graviton is so difficult to measure, let’s first look at the Compton scattering differential cross-section $d\sigma/d\Omega$. This involves the scattering of a photon $\gamma$ off an electron $e^{-}$ given by

where $\lambda$ is the photon’s wavelength and $p$ is the electron’s momentum. The final wavelength and momentum after scattering are denoted by primes. The likelihood of scattering is given by the Klein-Nishina formula