Atomic Clock В«Edge ESSENTIALВ»

Cesium atoms are sprayed into a vacuum chamber and hit with microwaves.

Since 1967, the International System of Units (SI) has defined one second as exactly 9,192,631,770 oscillations of the radiation produced by this transition in a cesium-133 atom. Why It Matters

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.

If the microwave frequency is exactly right, the atoms change states.

You likely interact with atomic clocks every day without realizing it:

High-speed data transfers and cellular networks require perfectly synchronized "stamps" to ensure packets of data arrive in the correct order.