Yoctosecond

Yoctosecond is a unit of time in the International System of Units (SI) equal to 10^-24 seconds. It is formed by applying the prefix yocto to the second; the symbol is ys. The prefix yocto (symbol y) denotes 10^-24 and was introduced in 1991 as part of an expanded set of prefixes.

Compared with other SI time units, a yoctosecond is far shorter than the better-known attosecond (10^-18 s) and zeptosecond (10^-21 s). One yoctosecond equals 10^-24 seconds.

The unit is mainly used in high-energy physics and discussions of processes at subatomic scales. Direct measurement on this scale is beyond current experimental capability; durations at this scale are inferred from theory and from energy scales via the uncertainty principle.

In particle physics, lifetimes on the order of 10^-25 to 10^-24 seconds are discussed; the decay time of the top quark is about 5×10^-25 s, roughly 0.5 yoctosecond.

Related time units include the attosecond and the zeptosecond.