Ending it all: the threat to the entire universe

It has been called "the ultimate ecological catastrophe", but even these strong words fail to convey the true horror and finality of a grim kind of natural disaster known to physicists as "vacuum decay".

Forget pandemic viruses that wipe out humanity, asteroid strikes that devastate life on Earth and even black holes that devour the planet. Vacuum decay leaves the entire universe not only lifeless, but without any hope of life for ever more.

Vacuum decay, which is happily only a theoretical prospect, occurs when part of the universe is knocked into a more stable state than it exists in today. This creates a bubble of "true vacuum" that expands at the speed of light. As the bubble grows, it reduces the energy locked up in the vacuum of space and rewrites the laws of nature.

In 1980, the late Harvard physicist Sidney Coleman published calculations that showed for the first time that vacuum decay was eternally terminal. He wrote: "One could always draw stoic comfort from the possibility that perhaps in the course of time the new vacuum would sustain, if not life as we know it, at least some structures capable of knowing joy. This possibility has now been eliminated."

Theory. So enticing, so disappointing.