The wonders of the night sky, the Moon and the Sun have fascinated mankind for many millennia. Ancient civilizations were particularly intrigued by several brilliant ‘stars’ that move among the far more numerous ‘fixed’ (stationary) stars. The Greeks used the word πλαντηζ, meaning wandering star, to refer to these objects. Old drawings and manuscripts by people from all over the world, such as the Chinese, Greeks and Anasazi, attest to their interest in comets, solar eclipses and other celestial phenomena.

The Copernican–Keplerian–Galilean–Newtonian revolution in the sixteenth and seventeenth centuries completely changed humanity's view of the dimensions and dynamics of the Solar System, including the relative sizes and masses of the bodies and the forces that make them orbit about one another. Gradual progress was made over the next few centuries, but the next revolution had to await the space age.

In October of 1959, the Soviet spacecraft Luna 3 returned the first pictures of the farside of Earth's Moon (Appendix F). The age of planetary exploration had begun.