Atomic clocks display time according to the frequency of cesium atoms changing from a positive to a negative electrical state. Cesium is an atomic element that vibrates as it changes its electrical charge. A detector counts the number of atomic electrical switches, and at a preset frequency, adds a second.
The atoms are funneled down a tube and exposed to radio waves, which must be tuned at precisely 9,192,631,770 cycles per second. The frequency causes the cesium atoms to vibrate, which triggers the change in the electrical charge. At the end of the tube is a detector that counts the number of atoms that have switched.
The detector sends this information back to the radio wave generator, helping to fine tune the frequency of the waves. At the same time, the information goes to other electronic parts that use it to change the time on the display.
Since this method of marking time is so precise, a cesium atomic clock can only lose 0.03 nanoseconds per day. It would take roughly 100 million years to lose an entire second. This type of high-tech timekeeping is needed for high-speed electronic communications, to run electrical grids and to keep the Global Positioning System accurate.