by Shannon K'doah Range and Jennifer Mullins
Gravity Probe B has made one of the most sophisticated and accurate gyroscopes in the world to measure the shape and motion of local spacetime. Yet, their gyroscopes have much in common with the simplest toy tops that children have played with for centuries.
The spinning top retains its balance through a physical phenomenon called "precession". Without this phenomena, there would be no toy tops or Gravity Probe B.
In early times, people discovered the spinning top, a toy with a unique ability to balance upright while rotating rapidly. Ancient Greek, Chinese and Roman societies built tops for games and entertainment.
The Maori in New Zealand have used humming tops, with specially-crafted holes, in mourning ceremonies. In 14th century England, some villages had a large top constructed for a warming-up exercise in cold weather. Tops were even used in place of dice, like the die in the contemporary fantasy game Dungeons & Dragons.
It was not until the late 18th and early 19th centuries that scientists and sailors began attempting to use spinning tops as a scientific tool.
At that time, sailors relied on sextants for navigation, measuring the angle between specific stars and the horizon. This method was limited, however, if choppy seas or fog obscured the true horizon, or clouds obscured the stars.
Serson, an English scientist, noted in the 1740's that the spinning top had a tendency to remain level, even when the surface on which it rested was tilting. He suggested that sailors could use it as an artificial horizon on ships. Unfortunately, when Serson went to sea to test this idea the ship sank and everyone was lost.
A French scientist in the 19th Century, Fleuriais, created a top that was continuously powered by air jets blowing into mini-buckets on the rim of the wheel - a process that has been used for thousands of gyros since.
The first modern gyroscope was designed in 1810 by G.C. Bohnenberger. It was made with a heavy ball instead of a wheel, but since it had no scientific application, it faded into history.
In the mid-19th century, the spinning top acquired the name, "gyroscope," though not through its use as a navigation tool. French scientist Leon Foucault had experimented with a long, heavy pendulum in an attempt to observe the rotation of the Earth. The pendulum was set swinging back and forth along the north-south plane, while the Earth turned beneath it.
Foucault corroborated the observation by using a spinning top in a similar manner. He placed a wheel, rotating at high-speed, in a supporting ring in such a way that the axis of the spinning wheel could move independently of the ring. In fact, the supporting ring moved over the course of a day, as it was connected to the surface of the rotating Earth. The axis of the wheel remained pointed in its original direction, confirming that the Earth was rotating in a twenty-four hour period.
Foucault named his spinning wheel a "gyroscope", from the Greek words "gyros" (revolution) and "skopein" (to see); he had seen the revolution of the Earth with his gyroscope.
Fifty years later (1898) Austrian Ludwig Obry patented a torpedo steering mechanism based on gyroscopic inertia. It consisted of a little bronze wheel weighing less than 1.5 pounds that was spun by an air jet (like Fleuriais').
In the early 20th Century, Elmer A. Sperry developed the first automatic pilot for airplanes using a gyroscope, and installed the first gyrostabilizer to reduce roll on ships.
While gyroscopes were not initially very successful at navigating ocean travel, navigation is their predominant use today. They can be found in ships, missiles, airplanes, the Space Shuttle, and satellites.
Gravity Probe B
Last Updated: 7 February 2011