Built into the thin case of every iPhone is a micro-thin 3-axis gyroscope that can detect when the iPhone is pointed up, down, sideways or at any angle in between. Combined with the iPhone's built-in compass and accelerometer, this can make the iPhone a compact virtual reality device, able to adjust the screen depending on where you are pointing it. A basic free app called Gyroscope can illustrate how the chip inside the iPhone reacts to your movements. To have a bit more fun with the gyroscope, try using one of the interactive games available from the iPhone's App Store.

Using the Gyroscope App

Step 1

Download the Gyroscope app by Acrossair. When you launch the app, it displays a moving gyroscope with three numbers on the top of the screen: Roll, Pitch and Yaw.

Step 2

Lay the iPhone on a flat surface like a table. The Roll and Pitch both display "0" degrees. Rotate the iPhone on the table and the Yaw changes depending on how far you rotate it. If you are pointing the iPhone south and move it to point west, the Yaw will change from "0" to "90" degrees. If you point it east, it changes to "-90" degrees.

Step 3

Lift the top of the iPhone from the table and let the bottom continue to rest. This changes the Pitch. Holding the iPhone perpendicular on the table changes the pitch to "90" degrees.

Step 4

Hold the iPhone flat on the palm of your hand. Rotate your wrist to the left or right, or just lean from side to side, and the Roll changes. If you hold the iPhone on its side perpendicularly to the horizon, the Roll displays either "90" or "-90" degrees, depending on which way you tilt it.

Gyroscope-Based Apps

Step 1

Download a game or other app that uses the iPhone's gyroscope in its design. Racing games like Real Racing 2 HD, first person shooting games like Shooting Showdown (free), as well as astronomy apps like Planets (free) and GoSkyWatch Planetarium all use the iPhone's gyroscope.

Step 2

Launch the gyroscope-based app and hold it in front of your face. Turn to the left or right. Tilt the iPhone up or down. As you move, the app's screen changes so you look up at the sky, down at the floor or around the virtual room. The astronomy apps use the gyroscope and compass to show you the stars and planets where the iPhone is pointing.

Step 3

Look at the app's options to see if the gyroscope is enabled by default. If the app's description states that it uses a gyroscope or virtual reality, it is normally turned on by default, however some games may require that you turn it on before the feature is enabled.