The unification of quantum mechanics and general relativity is arguably the biggest question of modern physics.  One of the approaches to answering this question is the class of theories known as semiclassical gravity, which are nonlinear theories that are more closely aligned to general relativity than standard quantum mechanics.  Although semiclassical gravity has a number of disadvantages when compared to other branches of quantum gravity – mainly string theory and loop quantum gravity - they are formulated with no free variables, meaning that the theories can be conclusively, experimentally tested. Therefore, even if these theories prove not to reflect fundamental reality, they provide inroads to bridge the gap between quantum gravity theories and the current experimental knowledge.

This presentation will outline the principles of semiclassical gravity and discuss some of the experimental and theoretical work being done on the subject.