Atomic clock

An atomic clock is a special type of clock that tells really, really, REALLY accurate time. It uses something called an atom, which is a tiny particle that makes up everything around us. An atom has a tiny center, called a nucleus, that is made up of even tinier particles. An atomic clock uses this tiny center to tell time.

The way it works is that scientists take a special kind of atom that's very good at keeping time, called a "cesium" atom. They use special machines to hold the atoms in place and keep them from moving around too much. Then, they zap the atoms with a special burst of energy to make them start vibrating. When the atoms start vibrating, they create a special kind of wave that moves at a really regular pace, like a metronome.

Scientists then count how many times this wave goes up and down in a second. They use this number to tell the time. Because the cesium atoms vibrate at a very regular pace, the atomic clock can tell time very precisely. It's so accurate that it can stay correct for thousands of years without being off by even one second!

This is really useful for all kinds of things like making sure that GPS satellites are sending the right signals to your phone, or measuring how fast things are moving in space. That's why scientists use atomic clocks to help them do all kinds of important things.