What We Cannot Know: Explorations at the Edge of Knowledge

by Marcus du Sautoy

There are several mechanisms for this decay, each depending on one of the fundamental forces. Each mechanism has a characteristic signature which helps physicists to understand which fundamental force is causing the decay. Again it’s energy considerations that control which is the most likely force at work in any particle decay. The strong nuclear force is usually the first to have a go at decaying a particle, and this will generally decay the particle within 10–24 of a second. Next in the hierarchy is the electromagnetic force, which might result in the emission of photons. The weak nuclear force is the most costly in energy terms and so takes longer. A particle that decays via the weak nuclear force is likely to take 10–11 seconds before it decays. So by observing the time it takes to decay, scientists can get some indication of which force is at work.