Deriving Dimensions

Deriving Dimensions
P. Coddington/Univ. of Adelaide

It seems like the most obvious physical fact: The universe has four dimensions--three spanning space and one ticking away time. But the ultimate theory of gravity should explain why the universe is four-dimensional and how those dimensions arose, say researchers trying to unify the theories of quantum mechanics and relativity. Now, calculations in the 24 September PRL show that when all possible microscopic contortions of spacetime are added together, a large-scale four-dimensional universe can emerge.

For nearly 80 years physicists have struggled to reconcile the prevailing theory of gravity with quantum mechanics. According to Einstein's general theory of relativity, mass and energy warp spacetime. The undulations then affect the trajectories of passing objects, producing the effects we call gravity. In Einstein's theory, spacetime is a stretchy, dynamical entity.
(focus.aps.org)