Luna programme became the first probe to achieve a soft landing on another planetary body. It returned five black and white stereoscopic circular panoramas, which were the first close-up shots of the Lunar surface. "Luna 10" (March 1966) became the first artificial satellite of the Moon. "Luna 17" (November 1970) and "Luna 21" (January 1973) carried the Lunokhod vehicles, which roamed around on the Moon's terrain. Another major achievement of the Luna programme, with "Luna 16" (September 1970), "Luna 20" (February 1972) and "Luna 24" (August 1976), was the ability to collect samples of lunar soil and return them to Earth. The
Dynamics of the celestial spheres individual unmoved mover would be required to insure each individual motion in the heavens. While stipulating that the number of spheres, and thus gods, is subject to revision by astronomers, he estimated the total as 47 or 55, depending on whether one followed the model of Eudoxus or Callippus. In "On the Heavens", Aristotle presented an alternate view of eternal circular motion as moving itself, in the manner of Plato's world-soul, which lent support to three principles of celestial motion: an internal soul, an external unmoved mover, and the celestial material (aether). In his "Planetary Hypotheses", Ptolemy (c.90–168) rejected the