we could not yet be sure about where we were in the sole oar system. we didn t know how far apart the planets were from each other, how far we were from the sun. in 1716 in edmond haley s lifetime, that part of earth was very much a mystery. here s what he figured out, the planet venus, second from the sun, a nearly twin planet to earth, every so often the orbit of venus and the orbit of us line up in such a way that we can actually see venus between us and the sun. we re third from the sun, venus is second from the sun, and we can see it once in a really, really rare while as it scoots between us and the sun that we both go around. our boy edmond haley predicted that if we measured that, if we counted how much of time it took for this movement of venus across the sun, which we can see, we could figure out how far we are from the sun and how far we are from other planets and how far those other planets are from the sun. we could figure out how big the whole kit and caboodle is.