You may remember this gadget from your childhood toy chest, where it lived in the dregs beside a wad of knotted string. The more industrious among you may have spun it on the floor like a top or danced it across a string before banishing it to the shadows.
But gyroscopes -- gyros for short -- are more than mere forgotten toys. Unlike the faceless Mr. Potato Head of your childhood, this little device plays a vital role in some of the most complex machinery on Earth -- or in orbit around it. An airplane's autopilot system depends on gyros to keep the craft level, and control moment gyroscopes (CMGs) help to make sure that the International Space Station and the Hubble Space Telescope are facing the right direction as they spin around the planet.
It all comes down to a physical property known as precision, the cone-shaped motion of a spinning body's axis. Once you start a gyroscope spinning, its axle continues to point in the same direction.
The article "How Gyroscopes Work" goes into greater depth on precision -- and includes some helpful illustrations -- but you can think of it in terms of simple directional awareness. We know the sun rises in the West, so no matter how lost you manage to get during the night, you'll at least know which direction is which come dawn. Gyros allow us to create machines capable of measuring or maintaining orientation in a physical space, a handy ability to have when your plane is, say, engulfed by clouds.
How does this factor into motion control and Moses' fabulous rod? Well, just look to the iPhone 4, Wii Motion Plus and the PlayStation Move. These smartphones and game controllers depend in part on tiny gyros that enable a device to detect movements relative to a fixed point -- such as your gaming console or the smartphone in your hand.
So just imagine the bearded Hebrew prophet raising a Wii controller instead of a stick and you get the general idea.