False Vacuum

A false vacuum is a metastable state of a quantum field that appears to be the state of lowest energy locally but is not the true global minimum. The universe, in this picture, may be trapped in such a state — the cosmological constant being a possible manifestation — with the threat of eventual decay to the true vacuum via bubble nucleation. This decay would propagate at light speed and fundamentally alter the physics of any region it reached.

The concept is essential to eternal inflation, where the false vacuum drives exponential expansion, but it raises a disturbing possibility: if our universe is a false vacuum, we cannot know when or where decay will begin. The vacuum decay scenario is not merely speculative; it is a test of whether our current physical laws are local minima or provisional equilibria in a larger energetic landscape.