ELI5: How does GPS use satellites?

Imagine you're playing hide-and-seek, but instead of people hiding, it's you. And instead of your friends finding you, it's satellites way up in space!

How do they do it?

• We have lots of satellites circling the Earth, like friendly helpers watching from above. These are GPS satellites.

• Your phone (or your car's navigation system) has a special receiver. Think of it like a listening ear.

• When you want to know where you are, your phone "listens" for signals from the satellites. Each satellite sends out a signal that says "Hi! I'm satellite number 1, and this is when I sent this message!"

• Your phone receives these messages. By knowing when each message was sent and when it was received, your phone can figure out how far away it is from each satellite. It's like knowing how long it took for your friend to yell "Marco!" and for you to hear "Polo!". The longer it takes, the further away they are.

• Your phone needs signals from at least four satellites to figure out your exact location. This is because it uses a method called trilateration. Imagine drawing circles around each satellite, with the radius of the circle being the distance calculated in the previous step. The place where all the circles intersect is where you are!

• Your phone then shows your location on a map, so you know where you are and where to go.