If you think it’s hard to find a needle in a haystack, just consider the problem of “finding” the planet Pluto. It is the outermost planet of our solar system, almost forty times as far from the sun as the earth! It is so faint that a good-sized telescope is necessary to even see it. Yet, somehow it was discovered. How was it done?

There are two sets of laws that help man obtain knowledge of the sizes of planets and their distances. Kepler’s laws of planetary motion made it clear that the orbits of the planets around the sun were not quite circles.