Pale Blue Dot - Carl Sagan [9]
Since scientists are people, it is not surprising that comparable pretensions have insinuated themselves into the scientific worldview. Indeed, many of the central debates in the history of science seem to be, in part at least, contests over whether humans are special. Almost always, the going-in assumption is that we are special. After the premise is closely examined, though, it turns out—in dishearteningly many cases—that we are not.
Our ancestors lived out of doors. They were as familiar with the night sky as most of us are with our favorite television programs. The Sun, the Moon, the stars, and the planets all rose in the east and set in the west, traversing the sky overhead in the interim. The motion of the heavenly bodies was not merely a diversion, eliciting a reverential nod and grunt; it was the only way to tell the time of day and the seasons. For hunters and gatherers, as well as for agricultural peoples, knowing about the sky was a matter of life and death.
How lucky for us that the Sun, the Moon, the planets, and the stars are part of some elegantly configured cosmic clockwork! It seemed to be no accident. They were put here for a purpose, for our benefit. Who else makes use of them? What else are they good for?
And if the lights in the sky rise and set around us, isn’t it evident that we’re at the center of the Universe? These celestial bodies—so clearly suffused with unearthly powers, especially the Sun on which we depend for light and heat—circle us like courtiers fawning on a king. Even if we had not already guessed, the most elementary examination of the heavens reveals that we are special. The Universe seems designed for human beings. It’s difficult to contemplate these circumstances without experiencing stirrings of pride and reassurance. The entire Universe, made for us! We must really be something.
This satisfying demonstration of our importance, buttressed by daily observations of the heavens, made the geocentrist conceit a transcultural truth—taught in the schools, built into the language, part and parcel of great literature and sacred scripture. Dissenters were discouraged, sometimes with torture and death. It is no wonder that for the vast bulk of human history, no one questioned it.
It was doubtless the view of our foraging and hunting ancestors. The great astronomer of antiquity, Claudius Ptolemaeus (Ptolemy), in the second century knew that the Earth was a sphere, knew that its size was “a point” compared to the distance of the stars, and taught that it lay “right in the middle of the heavens.” Aristotle, Plato, St. Augustine, St. Thomas Aquinas, and almost all the great philosophers and scientists of all cultures over the 3,000 years ending in the seventeenth century bought into this delusion. Some busied themselves figuring out how the Sun, the Moon, the stars, and the planets could be cunningly attached to perfectly transparent, crystalline spheres—the big spheres, of course, centered on the Earth—that would explain the complex motions of the celestial bodies so meticulously chronicled by generations of astronomers. And they succeeded: With later modifications, the geocentric hypothesis adequately accounted for the facts of planetary motion as known in the second century, and in the sixteenth.
From there it was only a slight extrapolation to an even more grandiose claim—that the “perfection” of the world would be incomplete without humans, as Plato asserted in the Timaeus. “Man … is all,” the poet and cleric John Donne wrote in 1625. “He is not a piece of the world, but the world itself; and next to the glory of God, the reason why there is a world.”
And yet