Gravity Particles Should Be Everywhere. So why are they Impossible to Find?

Quick Overview

Detecting the graviton appears fundamentally impossible through current experimental paradigms, as proposed methods either require detectors sensitive beyond the Planck length, leading to inevitable black hole formation, or demand colliders vastly larger than anything feasible to overcome gravity's extreme weakness.

Key Points: Freeman Dyson speculated in 2012 that the universe conspires to make graviton detection impossible, either practically due to outlandish experimental requirements or fundamentally due to black holes or the quantum vacuum. Detecting a single graviton using a LIGO-like interferometer requires measuring a length difference of the order of a single Planck length, which Heisenberg uncertainty dictates necessitates creating a black hole with the measuring apparatus. To produce gravitons via particle collision, a collider the size of 3 light years in diameter would be needed to reach the billion Joule energy required to match gravity's coupling strength to other forces, contrasting with the LHC's millionth of a Joule collision energy. The cross-section for a graviton-electron interaction is proportional to the square of the Planck length, making absorption detection extremely unlikely, even if solar emissions (4 per meter squared per second) or emissions from neutron stars were utilized. The Gertsenshtein effect, where a strong magnetic field transforms gravitons into detectable photons, is shut down by vacuum polarization, which causes spontaneous creation of matter-antimatter pairs in the required strong magnetic field. Neutrino noise poses a massive obstacle; any feasible graviton source interacting with matter produces $10^{34}$ times more neutrinos than gravitons, making signal distinction practically impossible.

Context: The video explores the challenge of confirming the quantum nature of gravity by detecting the graviton, the hypothesized quantum particle of gravity, which is necessary to unify quantum mechanics with Einstein's general relativity. This pursuit involves examining methods proposed for detecting gravitons, contrasting them with successful detection techniques for other fundamental particles like photons, and referencing the skeptical analysis provided by physicist Freeman Dyson in his 2012 Poincare prize lecture.