We've all heard about the superstitious ancient Chinese who thought that a solar eclipse was the result of a dragon trying to eat the sun. They banged on their pots and pans to scare the dragon off - and it worked every time. What we don't often hear is that the ancient Chinese - indeed the ancients in general - were actually very good at observing, recording and predicting both lunar and solar eclipses.
The Chinese records of eclipses go back to somewhere between 1350 and 1050 BC. The ancient Chinese work Chunqiu, which chronicles the events from 722 to 481 BC, provides records of 36 eclipses. From 400 BC onwards, the Chinese began to make more accurate records; the official history of the Liu-Song dynasty (420-434), the Songhu, provides us with many scientifically lucid accounts of eclipses.
The Babylonians, who until 100 years ago were seen as a totally superstitious folk, were astonishingly scientific in their approach to recording eclipses. Their astronomers kept systematic records, carefully estimating the magnitude and time of occurrence. The most famous Babylonian record is of the solar eclipse of 15 April 136 BC. As inscribed on a tablet at the British Museum, it reads: "Year 175 (Seleucid), intercalary 12th month, day 29. At 24 degrees after sunrise, solar eclipse. When it began on the south-west side, in 18 degrees of day in the morning, it became total. Venus, Mercury, and the Normal Stars were visible. Jupiter and Mars, which were in their period of disappearance, became visible in its eclipse . . . Time interval of 35 degrees for onset, maximal phase and clearing."
So, superstitious or not, both the Babylonians and the Chinese did their scientific duty. Without their records we would not be able to confirm the dates of many key historical events - including the birth of Christ. Where would the millennium celebrations be then?
Muslim traditions relate that a solar eclipse occurred immediately after the death of the Prophet Mohammad's infant son, Ibrahim. His followers thought that even the heavens were mourning the loss of the prophet's son. But the prophet admonished them by saying that there was no connection between the two events. The eclipse did not have any particular meaning; it was simply an accident of the arrangement of Earth and Moon.
The study of eclipses was a standard feature of Muslim astronomy. One of the most important categories of astronomical literature for the historian of science is the Islamic zijs, or astronomical handbook with text and tables. Most Muslim astronomers, from about the eighth to the 12th centuries, produced their own zijs, containing data on solar and lunar eclipses with detailed recordings of local time and magnitudes. The purpose of these tables was not just to test the reliability of contemporary eclipse data but also to determine the difference in longitude between selected cities. Astronomers would first predict when and where an eclipse would occur and then assemble parties of observers to take measurements and record details. The most famous result of such measurements is the zijs of the 11th-century Cairo astronomer ibn Yunus. For centuries it was the standard handbook on astronomical data.
So eclipses had been explained and understood centuries before Copernicus. In Europe, eclipses, along with rainbows and thunderbolts, continued to be a source of superstition till the tail-end of the 17th century. But with Descartes and his geometry (which showed how the rainbow is just a matter of reflection and refraction of sunlight in raindrops) and Ben Franklin and his kite (demonstrating that lightning is just a huge electric spark), common sense finally arrived. In the complacent, secular 18th century, eclipses were nothing more than big popular attractions. A print from 1735 shows all of Paris looking into pans of water for a safe view of the spectacle, and no one is prophesying the end of the world.
Which throws interesting light on our own times. It is not just the mindless hype associated with the coming solar eclipse that is hard to swallow, but also the constant stream of prophesies of doom. We are confident that all those ancient civilisations were superstitious for taking eclipses seriously as portents; but I cannot think of any time in history when so many nutty cults dominated so much of human consciousness.
There is one slightly odd but very significant feature of solar eclipses that does tend to bring out the truly irrational in most of us: the perfect fit of the moon's disc over the sun. If the moon were any further away from the Earth, then it would appear smaller against the sun and no eclipse would be total. If it were any closer, the sun would be totally hidden behind it, and the corona would not be visible. No one has worked out mathematically just why the moon should have such an exact fit. Is it simply a strange accident that provides us with the maximum effect? Or is there more to it than meets, or rather does not meet, the eye?
