And so everyone using celestial navigation needs a version of time that is related to how fast the whimsical horizon is delivering up new stars. Allegedly a clock that's one second off from UT1 can produce a quarter-mile navigational bungle. Enter the atomic clock. Atomic clocks, which were invented in the 1970s, simply measure the jiggling of dependable atoms such as hydrogen or cesium. These little atoms should jiggle steadily for centuries, the theory goes.
Problem is, the apparatus that counts the jiggles bothers the atoms and contaminates time.
Which is why timekeeping institutions manage vast herds of clocks, locked in special chambers. Defective and hurried though it is, the UTC interval is popular. When the television news comes on at 6 every night, you're seeing UTC in action. When the check you write clears before the deposit does, you're feeling it. The UTC interval is also reproduced in good clocks.