Theories of Space and Time from Aristotle to Einstein (Part I): From Aristotle to Galileo

Vishnya Maudlin, Ph.D. Professor
New York University, USA

We require, at the minimum, that theories account for the relevant facts. There are two types of facts: 1) facts that are based on observation, so-called empirical facts, and 2) conceptual/philosophical facts that are based on theories or preconceptions about the sort of world we live in. The difference between them is the type of reasoning that leads us to believe them. The road to scientific progress is paved by, on the one hand, collecting more accurate observations and, on the other hand, by careful examination of given conceptual/philosophical views. Shortcomings in either of these two areas impede scientific advancement. If we talk about astronomical theories, the relevant facts to be explained and predicted are primarily astronomical events. There were good reasons to hold on to the Aristotelian picture of the universe, which was dominant from 300 BCE until 1600 AD. Those reasons, as well as the whole Aristotelian picture, were replaced only when better observational evidence was obtained by Galileo using a telescope, and better theory by Kepler reexamining the preconceived notion that the heavenly bodies always move in uniform circular motion. The new observational evidence that reinforced belief in Copernicus’ heliocentric system, as well as Kepler's explanation of the planetary orbits in terms of ellipses, opened a way for a new physical basis for the heliocentric system: the new theory of motion and the universe governed by forces.