A shake is an informal unit of time equal to 10 nanoseconds. It has applications in nuclear physics,
helping to conveniently express the timing of various events in a nuclear explosion. The typical time required for one step in
the chain reaction (i.e. the typical time for each neutron to cause a fission event which releases more neutrons) is of order
1 shake, and the chain reaction is typically complete by 50 to 100 shakes.
