Does anyone know the reference and when the results of this was first published? My apologies, but my scientific literature searching skills are limited to biological science. I can't help wondering if given the state of the technology of the early 70s whether this might not have been actually a little beyond them - a bit like those early experiments to prove relativity detecting small changes than their instruments were calibrated to read accurately. I was reading this link http://sunearth.gsfc.nasa.gov/eclipse/SEhelp/ApolloLaser.html Perhaps it is gilding the lily to impress the rubes but... "The reflectors are too small to be seen from Earth, so even when the beam is precisely aligned in the telescope, actually hitting a lunar retroreflector array is technically challenging. At the Moon's surface the beam is roughly four miles wide. Scientists liken the task of aiming the beam to using a rifle to hit a moving dime two miles away...... Once the laser beam hits a reflector, scientists at the ranging observatories use extremely sensitive filtering and amplification equipment to detect the return signal, which is far too weak to be seen with the human eye. Even under good atmospheric viewing conditions, only one photon is received every few seconds." Call me stupid, but if you take the an original beam dispersed to 4 miles wide, of which only about 1 foot squared is available to be reflected back, and that 1 foot square is dispersed on the way back to 4 miles wide, not including any slight imperfections in the retroreflector adding a slight angle. On top of which the 2.3-6 seconds the earth will be rotating away - so that the beam will be being reflected back to a different position on the earth's surface from where it was sent. In sum, I am a little doubtful if in the early 70s they have the equipment that could detect and amplify this one photo every few seconds. It would be interesting to read the original publication - if they actually published in a peer reviewed journal.