The purpose of the Gravity Probe B (GP-B) experiment is to test two effects predicted by the general theory of relativity. This theory, established in 1916 by Albert Einstein, provides a geometrical framework for gravity, one of the four known forces in the universe. This view of gravity uses a metric to describe the curvature of space and time. Far from massive bodies, this metric reduces to that for euclidean space. In 1960, Leonard I. Schiff, using the general theory of relativity, predicted two new relativistic effects which cause an orbiting gyroscope to slowly precess. The first effect, known as the geodetic effect, is caused by the orbital motion of a gyroscope about the static mass of the Earth. The second effect, known as the frame dragging or gravitomagnetic effect, is caused by the rotation of the massive Earth. Frame dragging causes a slow rotation of the Earth's local space-time framework. The Gravity Probe B experiment will measure the size of these two deviations from flat space-time.