How does GPS know exactly where you are on Earth?

GPS knows exactly where you are on Earth by using special signals from satellites that are high up in space.

Imagine you have a toy phone and it talks to four toy satellites floating above your bedroom. Each satellite sends out a message saying, “I’m here!”, but the message takes a little time to reach your phone. By counting how long it took for each message to arrive, your phone can figure out how far away each satellite is.

It’s like playing hide and seek with four friends who are all in different corners of the room. Each friend tells you how many steps it took them to reach you. You use that information to guess where you must be hiding, right in the middle of the room!

Your phone does this same trick with satellites, but instead of steps, it uses time and speed of the signal to calculate your position.

When all four satellite messages come together, your phone knows exactly where you are on Earth, just like knowing where you are when you hear how far away each friend is.