Even in ancient Greek society, philosopher-scientists engaged in heated debate about the origin, composition, and structure of our universe.
We are delighted to present this week’s show on the ancient cosmos, the first of eight episodes in our new and exciting cosmology series, A Philosophical Guide to the Cosmos.
Cosmology—the study of the universe, how it was formed, and what laws govern its evolution—has exploded in the last few decades. But it’s not a new area of human inquiry. In fact, theories about the origin, nature, and structure of the cosmos go back thousands of years.
That’s not to say that ancient cosmologies were anything like our modern scientific theories of the cosmos. Many were more like creation myths or legends. However, in ancient Greece, thinkers like Anaximander, Aristotle, and Ptolemy, to name just a few, developed fairly sophisticated theories about the cosmos based on empirical observations. They looked up to the heavens, saw how the stars moved across the sky, how the sun rose and fell each day, and they developed rational explanations for what they observed.
We ultimately ended up rejecting most of these explanations, but not for a very long time. The cosmological picture inherited from Aristotle and Ptolemy was the dominant one in the west till the seventeenth century. This was the picture that placed an unmoving Earth at the center of a finite universe, with the sun and the other planets revolving around it in concentric circles called “celestial spheres.” Enclosing our universe was the sphere of "fixed stars," also called the "firmament." This marked the divide between the earthly and the heavenly realms. Indeed, the ancients had no sense of solar systems beyond our own, nor of the incredible number of galaxies stretching out into the vastness of space.
Despite inaccuracies in their theories, the Greeks were able to make many accurate astronomical predictions. For example, they could predict eclipses. They also figured out that the Earth was spherical. Considering the tools they had at their disposal, this is very impressive.
But do these ancient theories deserve to be called ‘scientific’? The fact that we have rejected most of them should not persuade us to answer this question in the negative. After all, the history of science is full of wrong ideas. It is only by rejecting bad ideas, and proposing new and improved theories that we make progress in science. The theories we accept now are the best we have, given the cognitive and technological tools currently at our disposal, but they are not immune to revision. This is what separates science from dogma.
Unfortunately, though, that ended up being the fate of ancient cosmology—it became dogma, once the Roman Church got its hands on it. No doubt, that is a big part of the story of why it remained the dominant view of the cosmos for so long. The Aristotelian geocentric model placed humanity at the center of the universe. Everything literally revolved around us, which supported the idea that we were God’s highest creation, that this was all made for us. Besides, the Bible said that the Earth didn't move, and that was the ultimate authority on God's universe. For these reasons, this picture of the cosmos was conferred the status of immune to revision. It was not to be questioned. Anyone who dared to raise doubts about it did so at great risk of punishment, even death. Bruno, an Italian cosmologist who followed Copernicus, was tried for heresy and burned at the stake in 1600 for proposing an alternative picture of the cosmos—an infinite universe lacking any center. A few decades later, Galileo was spared that fate, though he was placed under indefinite house arrest for his heretical Copernican views.
There’s a story we hear about the Scientific Revolution. It ushered in the demarcation of the disciplines. Whereas before there was no clear distinction between science, philosophy, theology, and so on, the Scientific Revolution marks a major shift where science and religion come apart and forever stay apart. No doubt, there is truth to this, but it glosses over some important facts.
Take Newton, the Scientific Revolution’s brightest star, if you’ll pardon the pun. Read his most important writings and you might be surprised to see how the scientific and the theological are completely integrated. For example, he claims that the “Supreme Being” is necessary for the motion of the planets, that without God, nothing in the natural world could account for their movement.
Newton’s talk of a “Supreme Being” is not worlds apart from Aristotle’s talk of an eternal “unmoved mover,” the ultimate cause of all motion in his geocentric universe, though Newton’s language has stronger religious connotations than Aristotle’s. It could be argued that Newton’s appeal to a supreme being was motivated by his religious beliefs in a way that simply is not true for Aristotle, who was, after all, a polytheist. The point is that, while it’s the case that no self-respecting scientist today would ever attribute anything to a “Supreme Being” as part of their cosmology, the separation between science and religion happened incrementally, and not overnight, as the term "revolution" suggests; and the revolution's heroes were sometimes more religious than their ancient predecessors.
The glossy story about the Scientific Revolution also does not give enough credit to ancient cosmologists as true scientists. Of course, their theories later became church dogma, but they are not at fault for that. What is important to note is that their methods—observing natural phenomena and using mathematics and logic to offer reasonable explanations—and the results they achieved—being able to make reliable predictions—go to the very heart of science. Did they get it right? No. But do we have it all right now? That’s highly unlikely. Only time will tell.
Our guest on this week’s show is renowned theoretical physicist Carlo Rovelli, a true intellectual who understands the value philosophy has for science. Check out this interview with him where he talks about his philosophy of science and his views about certainty.
To learn more about A Philosophical Guide to the Cosmos, our eight-episode cosmology series, or to listen to any of the shows, click here.