How Does Your Phone Know Exactly Where You Are?

Your phone talks to satellites floating in space. These satellites send down radio signals like tiny beacons. Your phone measures how long it takes for each signal to arrive. Since the signals travel at the speed of light, your phone can figure out how far away each satellite is. By looking at four different satellites, your phone draws imaginary circles around itself. Where these circles cross over is exactly where you are standing.

Imagine three friends telling you how far they are from you. You walk in a circle around them until you find the spot that matches all their distances. That point is your home. Four satellites give an extra check to make sure the clock inside your phone is ticking perfectly.