This weeks guest blogger, Patricia Fara, discusses some problems she faced when deciding how to begin her most recent book, Science: A Four Thousand Year History. She lectures on the history of science at Cambridge University, where she is Senior Tutor of Clare College. Her other successful books include Newton: The Making of Genius (2002), Sex, Botany and Empire (2003) and Pandora’s Breeches: Women, Science and Power in the Enlightenment (2004).

Lewis Carroll knew how difficult it can be to tell a story. ‘Where shall I begin, please your Majesty?’, asked the White Rabbit. Alice listened for the answer. ‘Begin at the beginning,’ the King said, gravely, ‘and go on till you come to the end: then stop.’

To write Science: A Four Thousand Year History, I had to decide when science began. This is no trivial question, but gets right to the heart of what science might be. Looking back at the past, it is possible to pick out ideas and discoveries that later became incorporated within today’s global scientific enterprise. But at the time, they contributed to other goals – finding an auspicious time for religious festivals, winning wars, vindicating biblical prophecies, making a living.

Separating science from superstition is not always easy. When early astronomical observers looked up into the heavens, they saw seven planets circling around the Earth. The Sun and the Moon were the most obvious, but they also identified five others – Saturn, Jupiter, Mars, Venus and Mercury (the next one to be discovered, Uranus, was only spotted at the end of the eighteenth century). Finding planets, and working out how they move across the sky, demands skills that are important for modern science. On the other hand, the first sky-watchers were not primarily interested in how the universe operates, but instead were trying to relate the patterns of the stars to major events on earth, such as famines, floods or the death of a king.

So it seems wrong to call them scientists. But does it make sense to disparage their conclusions? Modern astronomy rests on a foundation of data collected by expert star-gazers who were also astrologers. Their observations were generally sound, even if their theories have since been rejected. Many scientists find it hard to accept that their own expertise is rooted in beliefs which they dismiss as magic. For those who pledge their faith in progress, magical mumbo-jumbo has been eliminated by scientific reason: magic and science are clearly polar opposites, and any notion that they might share common origins is sacrilegious. But this comforting view is not always easy to reconcile with the historical facts.

Consider Isaac Newton. He believed so firmly in the Greek idea of a harmonic universe that he divided the rainbow into seven colours to correspond with the musical scale. Before then, although opinions varied, artists mostly showed rainbows with four colours. It is, of course, impossible to make any objective decision about the correct number, because the spectrum of visible light varies continuously: there is no sharp cut-off between bands of different colours, so how you think about a rainbow affects how you see it. Be honest – can you tell the difference between blue, indigo and violet?

Since Newton has become an iconic scientific genius, it would seem strange to say that he did not practise science. On the other hand, modern scientists denigrate many of his activities as ridiculous, or even antithetical to science. In addition to his preoccupation with numbers and biblical interpretation, Newton carried out alchemical experiments, poring over ancient texts and careful recording his own thoughts and discoveries. This was no mere hobby: Newton regarded alchemy as a vital route to knowledge and self-improvement, and he incorporated his findings within his astronomical theories.

The example of Newton illustrates how hard it is to pin down exactly when science began. One possibility is to look for the first scientists. But the word scientist was not even invented until 1833, and even then was slow to catch on. Both Michael Faraday and Charles Darwin refused to let themselves be labelled with the new term, but a history that excludes them would seem strange. The most popular starting date is 1543, when Nicolas Copernicus suggested that the Sun and not the Earth lies at the centre of our planetary system. However, there are several objections to this choice, not least that it excludes the Islamic sages whose ideas were so significant in Renaissance Europe, and also the Greeks, whose theories remained influential well into the eighteenth century. So some historians decide choose to begin with the geometer Thales of Miletus, who lived on the Turkish coast around 2500 years ago, and successfully predicted an eclipse. But picking him results in leaving out all of his important predecessors, such as the Egyptians and the Babylonians.

For Science: A Four Thousand Year History, I decided to start with the Babylonians, whose way of thinking about the universe still affects modern science. Instead of counting in tens and hundreds, they used a base of sixty, which is why there are 360 degrees in a circle. Their complex mathematical techniques and detailed star observations enabled them to predict celestial events – and because their knowledge of the skies was inherited by later observers, it now forms the basis of astronomy as well as structuring everyday life. Thanks to the Babylonians, weeks have seven days, hours have sixty minutes, and minutes have sixty seconds. The next time you look at a digital clock, remember that it has more in common with a clay tablet than you might think.