Introduction

There are several types of precession phenomena which are of interest in relativity: the Thomas Precession occurs when a gyroscope suffers a non-gravitational acceleration; geodetic precession is usually considered as due to motion of the gyroscope through a gravitational field as the gyroscope falls freely through the field; Lense-Thirring Precessing is usually considered as due to dragging of the local inertial frame of an orbiting gyroscope due to the rotation (angular momentum) of the mass source that is keeping the gyroscope bound in orbit. In this lecture we shall show how all these precession phenomena can be considered to be "gravitomagnetic" in origin. In general relativity, gravitomanetism arises from the space-time cross terms in the metric tensor, the $g_{0i}$ terms. I shall explore the simplest cases of gyroscopic precession here by transforming to a frame of reference whose origin falls along with the gyroscope, but which does not rotate. We shall see that in this frame of reference all precessions are gravitomagnetic in origin.