Time 6

The trick to measuring time is to find something repetitive that always takes the same amount of time. We just guessed at first. we said hey I think that the sun is there for the same amount of time each day so we used that to tell time with. Of course it wasn’t’. then we used the stars. And of course they weren’t quite right either, now the second is defined by the radiation emitted by caesium atoms. Which in another hundred years or so we will discover is not quite right either. To be more precise Now the SI (the people who define these sorts of things) has declared that a second is 9,192,631,770…well let me explain exactly what the periodic thing that caesium does is. Ok first you have all the electrons right? And they are in their little orbital. Have I ever explained about spin? Well it’s a property of electrons and protons and stuff BUT they don’t really spin. This confused me for a long time. Anyway electrons only have two ‘spins’. They can either spin up or spin down. And if you take a ceasium atom and look at the electrons on its lowest energy level you will it (they?) flip spin in a very period way. In fact 9,192,631,770 flips occur in our traditional second. So now this is what we use to define a second.