How Does Your Phone Know Which Way Is Up?

Your phone has two super small helpers inside it. One is an accelerometer that feels gravity like a pendulum. If you hold your phone flat, gravity pulls down. If you turn it sideways, gravity seems to pull to the side. The other helper is a gyroscope that feels like your inner ear when you spin around.

The accelerometer tells the phone which way is "down" toward the earth. The gyroscope tells the phone how fast it is turning and in what direction. When you walk to the store, the phone counts your steps by feeling the little bumps up and down. These tiny tools help apps know if your screen should be tall or wide.