# A New Link Between Quantum Physics and Gravity Source: https://www.youtube.com/watch?v=912vQr6ulNk Recap page: https://rapidrecap.app/video/912vQr6ulNk Generated: 2026-02-03T16:55:07.872+00:00 --- ## Quick Overview A new paper suggests a method to link quantum physics and gravity by recalculating quantum corrections in general relativity, arguing that for nonlinear theories like GR, one must average the product of the metric tensor and its derivatives, not the product of the averages, which potentially makes quantum corrections significant on galactic scales due to the cosmological constant. **Key Points:** - Einstein's general relativity is strictly wrong because it does not account for quantum effects, even though quantum particles create gravitational fields. - Previous calculations showing quantum gravity effects were too small to measure by a factor of 10 to the 20, rendering them experimentally unreachable. - The new paper proposes that because general relativity is nonlinear, the average of the product of the metric tensor and its derivatives must be taken, rather than the product of the averages. - The authors find that while quantum corrections remain tiny in the solar system, they can become large on the scales of galaxies due to a contribution from the cosmological constant. - First author Ben Kau states that on cosmological scales, there is a "clear difference between the particle trajectories predicted by the quantized new equations and those obtained from unquantized general relativity." - The presented work is not a full theory of quantum gravity but a formalism linking such a theory to observations, requiring an input describing the quantum state of space and time. - The reviewer rates the paper a three out of ten, finding it formally correct but questioning the claim of a clear difference at large distances based on the provided text. **Context:** The video discusses a new physics paper attempting to bridge the 90-year gap between Einstein's General Relativity (GR) and quantum mechanics, a problem known as quantum gravity. GR accurately describes gravity on large scales but lacks quantum effects, which are necessary because quantum particles generate gravity. The core challenge has been that theoretical quantum corrections to GR are calculated to be far too small to ever be experimentally tested. ## Detailed Analysis The fundamental issue addressed is that Einstein's general relativity is incompatible with quantum physics because it fails to incorporate quantum effects, despite the known fact that quantum particles generate gravitational fields. While physicists have sought a theory of quantum gravity for decades, predicted quantum corrections to classical motion are typically too small, by factors like 10 to the 20, to be measured. The new paper introduces a crucial modification stemming from GR's nonlinearity: the equations for particle motion involve products of the metric tensor and its derivatives. The authors assert that one must calculate the average of this product directly, rather than calculating the average of the metric and then squaring it, which is the standard approach when treating the metric quantum mechanically. Applying this new technique reveals that although solar system corrections remain negligible, on the scales of galaxies, the cosmological constant introduces a contribution to the quantum corrections that can become significant. First author Ben Kau suggests this difference in particle trajectories at large scales offers an alternative perspective on puzzles like dark matter, although the resulting equation does not directly match Modified Newtonian Dynamics (MOND). The presenter notes this is not a complete theory of quantum gravity but a formalism that requires an input regarding spacetime's quantum fluctuations, leading the reviewer to assign a modest score due to insufficient quantification of the results. ### The Problem with General Relativity - Einstein's masterwork is strictly wrong because it does not have quantum effects - Quantum effects are needed because quantum particles create a gravitational field - Physicists have sought a theory of quantum gravity for 90 years ### The Scale of Quantum Effects - Quantum fluctuations of spacetime effects are calculated to be a factor 10 to the 20 too small to be measured - General relativity is nonlinear, meaning products of the metric tensor and its derivatives are involved in equations ### The New Approach - The authors insist on taking the average of the product of the metric and its derivatives, not the product of the averages - This recalculation changes how quantum contributions are derived ### Galactic Scale Implications - Quantum corrections remain tiny in the solar system - On scales of galaxies and beyond, the cosmological constant makes a contribution that can become large ### Connection to Cosmology - The new quantized equations predict a clear difference in particle trajectories versus unquantized GR on large scales - This difference relates to puzzles like dark matter and modified gravity theories like MOND ### Reviewer Assessment - The work is a way to link quantum gravity to observations, not a complete theory - The paper rates a three out of ten because the authors should have made more effort to quantify results, and the reviewer is unconvinced about the claimed large-distance difference.