Seeing is believing, but we do not see with our eyes only. We look at the world with the aid of inherited images that we may strive to improve but that we do not work to replace unless something dramatic occurs. The traditional Earth-centred system was confirmed not just by the everyday experience of seeing the Sun rise and set, but by the high-powered geometry that was embodied in Ptolemy’s Almagest, the result of centuries of diligent observation and detailed computation. Anyone who opens that great classic today cannot fail to be impressed by the mathematical sophistication that is displayed on virtually every page. Better still, those who use the Ptolemaic methods to determine the position of the planets find that they work. Indeed, elementary astronomy is still presented from the standpoint of a motionless Earth, and we learn to calculate where Venus or Mars will be in the night sky on the assumption that the celestial vault revolves once every twenty-four hours. We know, of course, that this is a fiction, but it remains a convenient fiction. It would not merely be pedantic, but foolish, to correct people who say that the Sun moves from east to west by pointing out that it is really the Earth that rotates from west to east. If you doubt this, try playing the rigorous astronomer at the next cocktail party. You may well discover that people are neither impressed nor amused.
Galileo the Copernican
by William R. Shea
We See Through a Glass Darkly
The fact that Galileo became aware of the importance of the theological difficulties that were at the forefront of the concerns of the Jesuits long after he had seen mountains on the Moon tells us much about his intellectual stance. He was a mathematician by training and, as such, enjoyed a relative freedom from the Aristotelian philosophy and the thomistic theology of his period. He trusted the science of optics and was willing to accept the telescope as a way of extending our vision of the world. Whereas he peered through the telescope without blinking, many of his contemporaries still squinted and kept at least one eye on the Bible or Aristotle’s Physics.
William R. Shea
Galileo Professor of History of Science, University of Padua
A graduate of the University of Cambridge and a Former Fellow of Harvard University, Professor Shea taught at the University of Ottawa, McGill University in Montreal, and the University of Strasbourg before taking up his appointment in Italy in 2003. He was Chairman of the Standing Committee for the Humanities of the European Science Foundation, an association of 65 major research councils from 22 countries in Europe, and he belongs to several academies including the Academia Europaea, the Royal Society of Canada, and the Royal Swedish Academy of Sciences. He is Past President of both the International Union of the History and Philosophy of Science and the International Academy of the History of Science. He is the author, co-author or editor of 30 books including Galileo’s Intellectual Revolution, and The Magic of Numbers and Motion: The Scientific Career of René Descartes, and over 145 scholarly articles that have appeared in 10 languages. His book on Blaise Pascal, Designing Experiments & Games of Chance. The Unconventional Science of Blaise Pascal, won the Library Association Award as one of the outstanding academic books of 2003; Galileo in Rome: The Rise and Fall of a Troublesome Genius, written with Mariano Artigas (Oxford University Press, 2003) is translated into German, Spanish, Korean and Japanese. His latest book, written with Mariano Artigas, Galileo Observed: Science and the Politics of Belief, was published by Science History Publications in October 2006.