Lunar Laser Ranging, Gravitomagnetism and Frame-Dragging

During the past century Einstein’s theory of General Relativity gave rise to an experimental triumph, however, there are still aspects of this theory to be measured or more accurately tested. One of the main challenges in experimental gravitation, together with the direct detection of gravitational waves, is today the accurate measurement of the gravitomagnetic field generated by the angular momentum of a body. Here, after a description of frame-dragging and gravitomagnetism and of the main experiments to detect these relativistic phenomena, we show that the fundamental tests of General Relativity performed by Lunar Laser Ranging do not, however, include a measurement of the intrinsic gravitomagnetic field generated by the angular momentum of a body. Dedicated to John Archibald Wheeler, a master of physics of the XX century and father of the renaissance of General Relativity