Of all the giants on whose shoulders we stand, Aristarchos of Samos, the ancient Greek all-rounder, has proved to be especially tall: no one else (not even Einstein, to mention an iconic figure) has ever discovered anything (of like importance) that took so long to dawn on the rest of humanity. His achievement was extraordinary: with nothing more than the naked eye and the mind of a genius, he got to know the sun’s distance better than anyone else before, and he put the earth in motion around the sun for the first time in human awareness. The present book examines what history has spared of him and invites the reader to relive astronomy’s greatest moment.
Even if we didn’t have the benefit of Poseidonios’ or Aetios’ words to tell us, we could still find what Aristarchos really thought by reasoning like this: He proposed heliocentrism and then was faced with the question of why we can’t see any stellar parallax. Indeed, if the earth moves, we should see the stars shifting their positions from each other. So, why do we not? There are two answers: one is that they are all at the same distance from us, studding the sphere of the fixed stars; the other is that they are exceedingly far away and their shift is too small to be seen. (Actually, this is what happens.) Now, which of these options would Aristarchos favour? The answer is in the myriad figure: had he believed that there was such a thing as a sphere of fixed stars, a much shorter distance would have been enough to account for null star shifts. Yet, the very fact that he placed the stars a myriad times farther away than the sun and that this figure links parallax to human vision, as we shall see, proves that he had infinity in mind.