Depends entirely on the particle. A free neutron might have a half life of around twenty minutes. These pentaquark particles, well, nanoseconds are too long t

Depends entirely on the particle. A free neutron might have a half life of around twenty minutes. These pentaquark particles, well, nanoseconds are too long to describe, by about ten orders of magnitude. Some of the heavy elements assembled in colliders are described as decaying so quickly that one side of the nucleus is coming together even as the other side is disintegrating, a sort of brief wave of existence traveling at nearly the speed of light across this thing that has been forced together and wants to fly apart.