Einstein’s theory of general relativity, where gravity is caused by the curvature of space-time, is awesome. It has been confirmed to an incredible level of precision, extending to fifteen significant figures in some cases. One of its most amazing predictions is the existence of gravitational waves: small disturbances in space-time that travel freely. These very waves are now detected regularly by the LIGO/VIRGO experiments.
But we know that general relativity is incomplete. It works well when the quantum effects of space-time are small, which is almost always the case. But when the quantum effects of space-time become large we need a better theory: a theory of “quantum gravity”.
Since we don’t yet know the theory of quantum gravity, we don’t really know what space, and time, are. We have several candidate theories for quantum gravity, but none of them is generally accepted. Nevertheless, based on the existing approaches, we can speculate what might happen with space and time in a theory of quantum gravity. Here, I have collected the ten most mind-boggling speculations for you:
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