some social situations, there is the sense that we are central, important. Other social groups, of course, don't have that view. But it is generally those with privilege and status, especially in ancient times, who became the scientists, and there was a natural projection of those attitudes upon the universe.
So, for example, Aristotle provided powerful arguments, none of them instantly dismissible, that the heavens moved and not the Earth, that the Earth is stationary and that the Sun, the Moon, the planets, the stars, rise and set by physically moving once around the Earth every day. With the exception of this kind of motion, the heavens were thought to be changeless. The Earth, while stationary, had all the corruption of the universe localized here.
Up there was matter, which was perfect, unchanging, a special kind of celestial matter that is, by the way, the origin of our word 'quintessential.' There were four essences down here, the imagined four elements of earth, water, fire, and air, and then there was that fifth element, that fifth essence out of which the heaven stuff was made. And that's why the word 'quintessential'-'fifth essence'-comes about. It's interesting to see a kind of linguistic artifact of the previous worldview still present in the
Now, in the fifteenth century, Nicolaus Copernicus suggested a different view. He proposed that it was the Earth that rotated and that the stars were in effect motionless. He proposed moreover that in order to explain these apparent movements of the planets against the background of more distant stars, the planets and the Earth, in addition to rotating, revolved around the Sun. That is, the Earth was demoted. You know the phrase- another linguistic artifact-
Copernicus, by the way, felt his idea to be so dangerous that it was not published until he was on his deathbed, and even then it had an outrageous introduction by a man named Osiander, who was worried that it was too incendiary, too radical. Osiander wrote, in effect, 'Copernicus doesn't really believe this. This is just a means of calculating. And don't anybody think he's saying anything contrary to doctrine.' This was an important issue.
Aristotle's views had been accepted fully by the medieval church-Thomas Aquinas played a major role in that- and therefore by the time of Copernicus a serious objection to a geocentric universe was a theological offense. And you can see why, because if Copernicus were right, then the Earth would be demoted, no longer
And then came the still more unsettling possibility, the idea that the stars were distant suns and that they also had planets going around them and that, after all, you can see thousands of stars with the naked eye. Suddenly the Earth is not only
And then there was the hope that, well, at least maybe our galaxy was at the center of all the other galaxies, all those many billions of other galaxies. But modern views have it that there is no such thing as a center of the universe, at least not in ordinary three-dimensional space, and we are certainly not at it.
So those who wished for some central cosmic purpose for us, or at least our world, or at least our solar system, or at least our galaxy, have been disappointed, progressively disappointed. The universe is not responsive to our ambitious expectations. A grinding of heels can be heard screeching across the last five centuries as scientists have revealed the noncentrality of our position and as many others have fought to resist that insight to the bitter end. The Catholic Church threatened Galileo with torture if he persisted in the heresy that it was the Earth that moved and not the Sun and the rest of the celestial bodies. It was serious business.
Now, at the same time, another of the Aristotelian precepts was challenged. That was the idea that except for the moving of crystal spheres into which the planets were embedded, nothing changes up in the heavens. In 1572 there was a supernova explosion in the constellation Cassiopeia. A star that had previously been invisible suddenly became so bright that it could be seen by the naked eye. The Danish astronomer Tycho Brahe noticed it. Well, if nothing changes up there, how is it that suddenly a star appeared-I mean suddenly, in a period of a week or less, from invisibility to something easily seen-and then stayed for some months before fading away? Something was wrong.
Just a few years later, there was an impressive comet, the Comet of 1577, and Tycho Brahe-decades after Copernicus- had the presence of mind to organize an international set of observations of that comet. The idea was to see if it was down here in the Earth's atmosphere, as Aristotle had insisted it must be, or up there among the planets. Part of the reason that Aristotle had insisted that the comets were meteorological phenomena was his belief in an unchanging heaven.
So Brahe thought, if the comet is close to the Earth, then two observers far from each other will see it against different background stars. This is called parallax, which you easily can demonstrate by simply winking your eye, first the left and then the right, with a finger propped up about a foot in front of your nose. The finger seems to move as you blink.
Brahe reasoned that if the comet was very far away, then the two observers who were far apart would see it in almost exactly the same part of the sky. You could determine how far away it was by how much it moved between those two different vantage points, how much the parallax was. And Brahe determined it was surely farther away than the Moon and, therefore, up there, in the planetary realm, and not down here, where the weather is. That was another upsetting discovery for the institutionalized Aristotelian wisdom.
Now, as science has progressed, there have been-one after another-a series of assaults on human vainglory. One of them, for example, is the discovery that the Earth is much older than anyone had expected. Human history goes back only a few thousand years. Many people believed that the world was not much older than human history. And there was no sense of evolution, no sense of vast vistas of time. And then the geological and pa-leontological evidence began to accumulate, making it very difficult to see how the geological forms and the fossils of now- extinct plants and animals could have come into being, unless the Earth were enormously older than the few thousand years that had been projected. That is a battle still being fought. In the United States, for example, there are people who are called 'creationists,' the more radical of whom insist that the Earth is less than ten thousand years old. The shorter the age of the Earth, the greater the relative role of humans in the history of the Earth is. If the Earth is, as we certainly know it to be, 4,500 million years old and the human species at most a few million years old, probably less than that, then we have been here for only an instant of geological time, for less than one one-thousandth of the history of the Earth, and therefore in time, as in space, we have been demoted from the central to an incidental aspect.
And then evolution itself was still a further disquieting discovery, because at least it had been hoped that humans were separate from the rest of the natural world, that we had been specifically put here in a way different from petunias, let's say. And yet Darwin's historic work showed that we were very likely related in an evolutionary sense with all the other beasts and vegetables on the planet. And there remain many people who are enormously offended by this idea.
This sense of offense has-I'm only speculating-deep psychological roots. Part of it is, I believe, an unwillingness to come to grips with the more instinctive aspects of human nature. But I believe it is essential to understand this if we wish to survive. I think ignoring that, imagining all humans are rational actors in the present phase, is enormously dangerous in an age of nuclear weapons. I think the discomfort that some people feel in going to the monkey cages at the zoo is a warning sign.
Then, in the early part of this century, there was still another such assault, which came with special relativity. Because one of the central points of special relativity is that there are no privileged frames of reference, that we are not in an important position or state of motion. There is nothing privileged about the velocity that we have or the acceleration that we have; the universe can be understood precisely if it is true that we do not have a special frame of reference.
Now, it's certainly true that there is something special about our position in time. The universe has changed. A microsecond after the Big Bang, it was quite different from how it is right now. So no one maintains these days that there is not something special about our epoch in the sense that the universe itself evolves. But in terms of position, velocity, and acceleration, there is nothing privileged about where we are. This insight was obtained by a
