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Aristarchus’ notion that the earth revolved around the sun was ridiculed at the time but it became important 1700 years later. Mikolai Kopernik (1473-1543), the Polish astronomer, used this ancient precedent as a shield to protect him from the charge of blasphemy in defending his belief in the same principle.
Kopernik was a beneficiary of the new age of print. Books had been coming off the presses in Europe for 30 years and Kopernik availed himself of them greedily. Travelling as a young man to Italian universities, he came home to Poland with his familiar Latinized name Copernicus. He wrote a book that was as congruent with the religious climate as a Lutheran at a wet T-shirt competition. De Revolutionibus - the snappy title of Copernicus’ book in which he outlined his sun-centred cosmogony - sailed close to the theological wind.
The Church promoted a literal reading of the Bible and the Bible stated that the earth was still and central within the heavens. Copernicus’ work had implications about the size of the universe that his contemporaries found difficult to swallow. His theory implied the existence of stars the size of the entire orbit of the earth. Distance scales like these were vast and frightening to his peers. Faced with a revised picture of the universe, the unhappy science community reviled Copernican cosmology. The book was published only at the very end of Copernicus’ life and his publisher attempted to defuse potential papal wrath by a disclaimer. Citing an ancient Greek precursor (Aristarchus) took some of the heat off Copernicus; the Ancient World was gaining ascendancy in this early stage of Renaissance Europe. It was cool to be following Greek example in the early sixteenth century.
The Copernican model of the solar system was a series of nine concentric rings with the sun at the centre. In practice he added lots of detailed complexities to this basic scheme. Curiously, although this system was a major step forward in the history of cosmology, it fitted observation less well than its ptolemaic precursor.
Tycho Brahe (1546-1601) was the greatest astronomical observer of the sixteenth century. He was abducted by a rich, childless uncle as a young child, witnessed a total eclipse of the sun when he was 14 and lost most of his nose in a duel as a youth. He was not drawn at all to Copernican theory. If Tycho was an over-arching empiricist, he was certainly balanced by his young collaborator, Johannes Kepler (1571-1630). Kepler, a neo-platonist and Tycho, a pragmatic observer, were as well suited as a fish and a ferret in cocktail frocks. Both slightly odd, even more curiously matched, they quarrelled constantly, yet produced good science.
Kepler used Ockham's razor to shave some of the stubble from the entrenched ptolemaic system when he realised that the 'common sense’ assumption - that the orbits of the planets were circular - was mistaken. The planets kept appearing in unexpected positions. Calculating with elliptical (oval) orbits, the mismatch between observation and prediction that infected Copernicus' sun-centred universe was cured. This allowed astronomers to predict the motions and positions of stars and planets to a much greater degree. Kepler was the first scientist to use the language of mathematics to describe his work. This notation was taken up rapidly because of its power to make precise quantitative descriptions. Kepler's cosmology is as good as you get with the naked eye. The next major advance in astronomy came through new technology.
The apocryphal story about Galileo Galilei (1564-1642) dropping balls from the leaning tower of Pisa almost certainly never happened, but Galileo did develop the telescope, see mountains on the moon, discover sunspots, devise a pendulum clock. What can you say about Galileo? Well, the earth moved for him. Eppur si muove ("Yet it does move'), he is alleged to have muttered on being bundled from one ineffectual house arrest to another for the crime of holding and teaching Copernican doctrine.
It requires an imaginative leap to see why a sun-centred universe with a rotating earth should raise so much dust. In a pluralist society, many clashing views should be sustainable with no injury to the culture as a whole. Mid seventeenth century Italy had a complex and re-grouping power structure. The Roman Church drew much of its authority from a literal interpretation of the Bible. If the Bible was found to be unreliable on some counts, would the whole edifice come tumbling down? The Church continued to deny Copernican theory until 1922.
Galileo understood something about moving bodies that had not been understood before. Through experiment he realised that objects in free fall are subject to an equal force of acceleration whether they are heavy or light (excluding air resistance). If a light aerodynamic object is dropped at the same time as a heavy aerodynamic object, they will hit the ground at the same time. Objects like feathers fall more slowly because of their shape, not because of their weight. In terms of what we recognise to be the fundamental forces of nature today, perhaps this last accomplishment was the first step towards modern science.
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