For the John Templeton Foundation, I wrote about the challenging quest to reconcile our classical understanding of space and time with the principles of quantum gravity.
It is difficult to imagine a world without space and time. If something exists, Aristotle said, then it must exist somewhere. Our entire understanding of causality relies on the notion that some things happen before other things. So how do you talk about whether anything preceded the beginning of time? Despite these difficulties, physicists and philosophers are starting to work out how to think — conceptually, mathematically, and scientifically — about the mind-bending implications of quantum gravity, a set of hypotheses that attempt to bridge the chasm between seemingly incompatible physical descriptions of the universe at its largest scales (in general relativity) and at its smallest (in quantum field theory).
Nick Huggett and Christian Wüthrich are philosophers of science with deep experience analyzing the two leading attempts at a comprehensive description of quantum gravity. Huggett, who is based at the University of Illinois at Chicago, has spent years working on string theory, while Wüthrich, based at the University of Geneva in Switzerland, has focused on loop quantum gravity. Over the past several years they have been organizing gatherings of professors, postdocs, and students of philosophy and physics to learn about the leading theories of quantum gravity. They’ve been discussing whether quantum gravity indeed implies a world without space and time, and if so what it might mean: If the theories imply a basic reality that includes elements that are not part of space and time, how do our space-and-time-bound observations fit into it? And how can we make sense of (or even begin to describe) parts of reality outside space and time?