Eli5 – How do satellites tell the time?

Question

A friend of mine told me they measure with nuclear decay to tell time on satellites but I don’t understand what TF that means

In: 7

Answer 1

Not quite. Most modern clocks use something which vibrates at a specific frequency. Computers use a digital peizo crystal which is not very consistent. Modern watches use a quartz crystal which is fairly but not perfectly consistent. Atomic clocks use the resonant frequency of charges in the energy states of cesium. This is so consistent that we have decided to define the length of a second based on it.

No nuclear decay is involved.