View your list of saved words. (You can log in using Facebook.)
In the theory of special relativity, the slowing down of a clock
as perceived by an observer in relative motion with respect to
that clock. Time dilation becomes noticeable only at speeds
approaching that of light and has been accurately confirmed by
the apparent increased lifetime of unstable subatomic particles
traveling at nearly the speed of light and by the precise timing
of atomic clocks carried on airplanes. See alsoLorentz-
FitzGerald contraction. This entry comes from Encyclopædia
Britannica Concise. For the full entry on time dilation, visit
Britannica.com.