How Motion Control Works

Lights, Cameras, Action

No keyboard or controller required.
No keyboard or controller required.
Enamul Hoque/Rod Steele/Getty Images

Here's another possibility: What if Moses' magnificent rod really was nothing more than a walking stick? Perhaps all that hidden, sea-parting machinery merely activated when the bearded prophet made the appropriate motions.

Again, the sort of technology capable of parting the sea is a little bit beyond even our modern age -- but machines that respond to our movements? Why those are all around us.

Visit the local grocery store, where you'll notice a little motion detector that uses a simple form of radar to know when to activate the door. That motion detector emits microwave radio energy (or ultrasonic sound waves), which bounces back off the floor and returns to the sensor. Walk in front of its motion detector and those energy waves will rebound a little earlier -- right off your body. The detector registers a change in the time it takes for the waves to return, so it opens the doors to let that changer through.

Your motion controls an automatic door. The same radar technology turns on security floodlights when someone walks by or trips a home security alarm when a sufficiently large object moves through a room. Light-based systems have a beam of light or a laser beam that spans the space between a light source and a sensor. Break that beam with your movements and the alarm blares.

The Xbox 360's Kinect sensor represents an even more remarkable motion-detection system. The gadget relies on an infrared projector and a sensor to visualize even a dimly lit man cave of a gaming room in 3-D. Once the Kinect system maps out the room, it moves on to the humans.

The Kinect detects and tracks 48 points on each player's body and maps them to a digital reproduction of that player's body. Even a casual shrug of the shoulders -- or the dramatic raising of a mystical Old Testament rod -- becomes a control input.

So there you have it: three key ways that motion-control systems allow us to boss around gadgets and programs with our body movements. Any or all of them could conceivably give Moses' rod the power to activate a sea-parting super machine.

Of course, Moses also turns the rod into a snake at one point. You're on your own figuring that trick out.