Moving Heaven and Earth (Icon Science): Copernicus and the Solar System - Softcover

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John Henry is a senior lecturer in Science Studies at Edinburgh University. He is the author of Knowledge is Power.

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1. You'd Have to be Crazy to Say the Earth Moves

Death and taxes are often said to be the only certainties, but there’s something else. The Earth certainly doesn’t seem to be moving. No matter what the scientists tell us about the way the Earth rotates on its axis, so that someone standing at the equator is moving around the centre of the Earth at a speed of over a thousand miles per hour, it all seems perfectly still. We all believe whatwe are told about the Earth’s revolutions around the Sun, covering a distance of about 584 million miles in a year (which is another 66,000 mph or more), but we are taking it on trust – we can’t feel ourselves moving.

Those of us who have read a little further, or who have watched more programmes on Discovery Channel, or who once bumped into a friendly astronomer, might also have learned that we, together with the Sun, are circlingaround the centre of our galaxy at an even more unimaginable speed – roughly 350,000 mph – and that the galaxy itself is whizzing through space on a trajectory resulting ultimately from the Big Bang that created our universe (see the ‘Glossary’ section at the end of this book). But we cannot feel any of this.

It’s not just a question of how it feels either. If our senses don’t tell us the Earth is moving, it is also true that, for technical purposes, it actually makes sense to assume the Earth is stationary. If you look in a textbook on navigation, for example, you’ll see it assumes that the Earth is stationary, and that all the heavenly bodies are revolving around the Earth. The authors of such manuals probably know better than you or me that the Earth is perpetually performing a series of complex motions, but they also know that you don’t need to know this to steer your boat by the stars. On the contrary, it makes things simpler if you assume the Earth is still and only the stars, and your boat, are moving. Therefore, it is wrong to assume that technical demands must inevitably lead us to a belief in the motion of the Earth. They don’t.

So how on Earth did we ever come to believe in the motion of the Earth? If our senses and our common sense tell us that the Earth is not fast but steadfast, and if it is a requirement of a practically useful technical art like navigation that the Earth be considered stationary, why and how did we ever come to believe that the Earth is whizzing through space with such phenomenal speeds? If we just set aside for a minute what we have taken on trust since we were schoolchildren, the idea that the Earth is moving just seems totally crazy. It can’t really be moving, can it?

Yes it can, and what’s more we now all believe that anyone who denies the motion of the Earth must be a crank or a fool. So how has it come about that it is now crazy to deny what actually seems to be a crazy idea? The short answer is that we all now recognise the intellectual power and authority of science. Even if we don’t know much about the details, we know that a moving Earth is bound up with the latest astronomical and cosmological ideas, which in turn are bound up with well-established theories of modern mathematical physics. We also have a strong sense, even if we can’t follow the technical demonstrations, that this same edifice of mathematical physics has led to most, if not all, of the high technology that is now such an indispensable part of our lives. It is part of our scientific worldview that the laws of nature are so all-pervasive and so interconnected with one another that to reject the claim that the Earth moves would somehow have to entail not only, say, a denial that we ever landed men on the Moon, but also that television sets work.

But, of course, there hasn’t always been this kind offaith in the power and pervasiveness of scientific knowledge.Like everything else, our modern worldview has its history and its historical origins. If it is possible at all to pinpoint a single initial source from which the modern physical sciences developed and spread out, explaining more and more aspects of our world as they did so, and leading to more and more technical innovations, the most likely contender for the starting point would be Nicolaus Copernicus’s (1473–1543) claim that the Earth is in motion.

One of the main aims of this book is to explain how it was that a highly technical astronomical theory, far beyond the mathematical competence and the understanding of all but a very few people, came to have such far-reaching repercussions. Along the way we will come to see why it was Copernicus’s claim (first published in the middle of the 16th century) that was to have this seismic impact, rather than one of the various earlier suggestions that the Earth might be in motion.