Bee Hossenfelder called attention to an interesting paper in this post: A newly proposed table-top experiment might be able to demonstrate that gravity is quantized http://backreaction.blogspot.com/2015/10/a-newly-proposed-table-top-experiment.html Here's the paper: http://arxiv.org/abs/1510.01696 Optomechanical test of the Schrödinger-Newton equation André Großardt, James Bateman, Hendrik Ulbricht, Angelo Bassi (Submitted on 6 Oct 2015) The Schrödinger-Newton equation has been proposed as an experimentally testable alternative to quantum gravity, accessible at low energies. It contains self-gravitational terms, which slightly modify the quantum dynamics. Here we show that it distorts the spectrum of a harmonic system. Based on this effect, we propose an optomechanical experiment with a trapped microdisc to test the Schrödinger-Newton equation, and we show that it can be realized with existing technology. 13 pages, 4 figures, 1 table, 1 page of supplemental material ====comment==== If I understand correctly, the Schrö-Newt equation would hold if gravity were FUNDAMENTALLY semiclassical. And therefore NOT needing to be quantized. Quantum matter would produce a kind of classical probability distribution of gravitational forces--in the non relativistic limit. So if this equation can be experimentally REFUTED this would indicate that gravity is not fundamentally semiclassical and that a quantum theory of gravity is definitely required.