[Originally posted 15 February 2007]
e men of Galilei, why stand ye gazing up into the heavens? So an opponent of Galileo is said to have preached—the reference is to Acts 1:11—in opposition to his astronomical discoveries. Galileo’s tiny telescope was not even as good as the binoculars my father used when I was six or so to show me the rings of Saturn and the moons of Jupiter, but with it he turned the world upside down, as Martin Luther put it. Mountains on the moon, spots on the sun, the phases of Venus—these things may seem commonplace now, but they were revolutionary at the beginning of the seventeenth century. They weren’t in the Bible, or Aristotle, or any other authority from antiquity, and they suggested ideas that challenged the common sense notion of the world that then prevailed.
That the solid earth we stand on might be hurling at some inconceivable speed through space is counter-intuitive, to say the least. But if we accept it—and the idea was by no means new when Galileo started peering through his primitive telescope—might not the other bodies we see be worlds as well? The moon, Venus, Jupiter? Could they be inhabited? And why hadn’t the authorities, either religious or secular, said anything about all this? And if God wasn’t up there sitting above the sphere of the fixed stars, keeping everything in motion, turning the cosmic mechanism with a gigantic crank—well, then, where was he?
In the end Galileo, and Kepler, and Newton, and those that followed them would crack the tiny medieval cosmos open like an egg, revealing the splendor of the universe we know today. More than that, as time and distance commingle, we get to look back in time, and see the universe as it was. It’s been one hell of a trip from the tube Galileo looked through to the massive arrays of mirrors here on earth and the Hubble out in space, but he was there at the beginning, and he helped to start it all.