Stock exchanges use atomic time to log trades down to the microsecond, preventing fraud and ensuring a fair "first-come, first-served" system.
The best modern atomic clocks are so stable that they wouldn't lose or gain a single second in —a span of time longer than the age of the universe. Atomic Clock
Scientists use these clocks to detect tiny changes in gravity (General Relativity) and to search for dark matter. Precision Limits Stock exchanges use atomic time to log trades
Cesium atoms are sprayed into a vacuum chamber and hit with microwaves. Precision Limits Cesium atoms are sprayed into a
If the microwave frequency is exactly right, the atoms change states.
GPS satellites carry atomic clocks. Because radio signals travel at the speed of light, even a billionth of a second of error could result in your GPS being off by several miles.