Eclipse: The science and history of nature's most spectacular phenomenon. J. McEvoy P.

historical records were systematically kept for the first time. Alternatively, as legend has it, Nabonassar destroyed all the records of the previous kings of Babylon so that the reckoning of the Chaldean dynasty would begin with him. This new beginning was so effective that, centuries later, Ptolemy, the Greek astronomer and geographer, could only begin his historical account of the Babylonian kings from this date, even suggesting that the era began at midday on 26 February 747 BC.

      This day also marks an important beginning in the history of astronomy, because from here on the Chaldeans recorded highly accurate astronomical observations on a regular basis. Though it is true that the motive for these records was still mainly astrological, the observations became increasingly what can only be described as scientific.

      THE ECLIPSE ARCHIVE FROM BABYLON

      The astronomical texts, records of observations and predictions, reveal that through centuries of pre-eminence under the Chaldean dynasties, and even during later periods of decline, celestial observations continued to be made at Babylon on a regular basis and with little change of pattern. Modern scholars estimate that the programme lasted almost eight hundred years, until after the time of Christ. The most recent surviving astronomical text dates from AD 75, an almanac prepared from contemporary observations. Thus, from 750 BC to AD 75, there exists an archive of what the observers of Babylon saw in the heavens and recorded on clay tablets.

      To put this achievement into perspective, consider an equivalent project to make similar observations at Windsor Castle, starting at about the time of the castle’s construction in the early thirteenth century. This was the time of Richard the Lionheart and the Magna Carta. If the continuity of the Windsor ‘archives’ were to match Babylon’s, the skywatching would still be going on today, as the twentieth century gives way to the twenty-first. The observations would have continued through the reign of the Plantagenets and the War of the Roses, Elizabeth and the Spanish Armada, the Civil War and the Restoration. Perhaps in the late seventeenth century the observations would have been taken over by the Astronomer Royal, and examined by Isaac Newton and Edmond Halley. During Victoria’s reign the project would no doubt have been supervised by Prince Albert, science enthusiast and overseer of great civic works. Finally, in the twentieth century, astronomer-priests would get deferments from the Great War, survive the blitz of the Luftwaffe and even the celebrations marking the dawn of the new millennium.

       Figure 2.3. A Babylonian cuneiform text: an astronomical diary from 164 BC (British Museum).

      British Museum, London

      The priests and scholars responsible for this remarkable coordinated programme have been called the Babylonian watch-keepers. Their main motive for skywatching at Babylon was no doubt astrological; they generalised the observations to produce almanacs that were used for astrological predictions. Nevertheless, as the centuries passed and mathematical models were applied to reproduce past observations and predict future movement of celestial bodies, the cult of astrology came more and more to resemble astronomy.

      DISCOVERIES OF LATE BABYLONIAN ASTRONOMY

      Another aspect of the Chaldeans’ astronomy was their ability to use their extensive catalogue of celestial observations. While the watch-keepers continued to search the heavens for omens, astronomers were able to develop a mathematical theory from their study of the records. Their analysis of the records of ancient observations suggested the possibility of creating models of the movement of the Sun and the Moon. From these models, astronomers would then be able to predict future astronomical phenomena. Once they had seen this possibility, the Chaldeans realised that they needed better accuracy in their observations. As early as 1000 BC their scribes had recognised eighteen constellations, groups of stars forming recognisable patterns in the sky. By 500 BC these constellations were systemised and identified, singly or sometimes in pairs, with the twelve lunar months as the Moon, Sun and the planets moved through the sky. For example, the second month of the Babylonian year, corresponding to mid-April to mid-May, had symbols of both Taurus and the Pleiades; the third month, Gemini and Orion; and the twelfth month, Pisces and Pegasus.

      In order to introduce firm delineations for the purposes of astronomical diaries and observations, the ecliptic path along which the Sun moves was divided into twelve equal parts of 30°. This was called the zodiac, from the word for ‘animal’ – most zodiacal figures are animals or people. The first evidence of the use of this zodiac in a diary is from 464 BC, and by about 400 BC the zodiacal constellations had been clearly defined, beginning with Aries for the first month, corresponding to mid-March to mid-April. This system of zodiac constellations has lasted essentially unchanged to the present day, both for the science of astronomy and the pseudoscience of astrology.