Parallel paths to celestial wisdom

The sky in ancient pre-telescopic times was in essence indistinguishable from the sky today. In addition, when we go back historically a mere few thousand years, the mental capability of our ancient predecessors was in essence indistinguishable from the abilities of today's readers of journals, watchers of television and members of modern civilisation. But our ancestors, unburdened as they were by many modern concerns, had more time to observe the celestial changes and to ponder their significances.

How did the ancients make use of the sky? Did they first turn to theological pursuits and worship the Sun, Moon, planets and stars? Or were their early thoughts astrological, arising from their growing conviction that the movements of the celestial bodies against the stellar background influenced their lives, if not deterministically, at least in a probabilistic fashion? Or did they approach the heavens in a practical way, using the seven moving bodies as clock and calendar markers and navigational aids, the results echoing our divisions of hours and months, the timing of, say, Easter and Christmas, and the usefulness of the cardinal points north, south, east and west? Maybe the sky was a guide to the most suitable times for hunting and gathering, sowing and reaping, travelling and staying close to home. And, turning to modern science, when did our ancestors start trying to understand what was actually going on, as opposed to simply observing and recording?

Today, the study of the deep resonance between early cosmic themes and human thought is known as archaeoastronomy. It is a relatively new academic discipline that owes much to such ground-breaking books as The Dawn of Astronomy by J. Norman Lockyer (1894) and Stonehenge Decoded by Gerald S. Hawkins (1965). Students take degrees in archaeoastronomy; there are professors of it. But what faculty to put them in?

When we investigate the remains of such wonderful monuments as the Egyptian pyramids, the royal palace at Persepolis, the Caracol at Chichen Itz and Stonehenge, do we regard them as the precursors of today's telescopes? Are we looking at primitive scientific instruments, used to measure the rising, setting and transiting positions of astronomical objects in order to set the start of years or the timings of celebrations? If so, archaeoastronomers were primitive scientists. But maybe these edifices were temples, parliament buildings, funeral monuments or sports halls. The subject then becomes part of the humanities. The guiding forces behind the construction of these monuments might thus have been cultural, mythological, theological or astrological. Even today, we happily spend much more money (and time) on these pursuits than on scientific endeavours.

As with all historical interpretations, we have to be careful not to take today's intellectual baggage back with us in time. Today we look on the Sun as a typical star, a nearby handy guide to the intricacies of stellar astrophysics. We do not need the Sun to act as a watch or a calendar. Dawn, noon, sunset, full moon, the equinoxes and solstices often pass unnoticed and are of little importance as regulators of our everyday lives. Today's Sun is mainly irrelevant to our daily chores, only reminding us (too infrequently) to search for the tanning lotion and dark glasses.

But ancient civilisations were much more dependent on the Sun as a provider of heat, light, life and time markers. The role of the full Moon as a "streetlight" was also extremely significant in those far-off days. The progress of the month and the year influenced early lives much more significantly and practically than they do now.

It is thus easy to envisage how the Sun and the Moon could be deified. The solar influence on the seasonal variation of daylight and temperature, and the variability of the lunar disc as it waxes and wanes, linked both heavenly bodies with terrestrial life and death, growth and decay. It was a small step from the perceived significance of the Sun and the Moon to an astrological belief that the planets also influenced events on Earth.

Ancient observers quickly realised that the planetary positions were not random. Soon, astrological concerns motivated rulers to sanction and encourage rigorous observations of the sky, in the hope that future movements of celestial bodies could be predicted and their supposed consequences alleviated.

Astronomical markers became important in navigation, too, both on land and at sea. And the influence of the Sun and Moon on the times and heights of tides made the study of their movements of considerable importance to maritime trade. All civilised societies required calendars, and history is replete with attempts to marry together solar and lunar calendars and regulate work practices by dividing months into weeks and days into hours.

David Kelley and Eugene Milone have taught an undergraduate course on archaeoastronomy at the University of Calgary in Canada since 1976. It attracts three types of relatively mature students. Some have a background in astronomy, others in archaeology, and the rest are new to both subjects.

The course needed a textbook, so Kelley and Milone wrote one. Exploring Ancient Skies aims to cover the entire spectrum of the subject - scientific, geographical, mythological and historical - and to underline many of the interpretive problems. It succeeds superbly. I will turn to it time and again, not only for reference but also for enjoyment. Students, scholars and researchers will benefit hugely from the intellectual rigour and expertise of the authors. It is only a shame that the vast majority of intended readers will find the book well beyond their means.

Kelley and Milone stress the diversity of their subject, the many varieties of archaeoastronomy. Some aspects are only approachable via archaeological remains, for example Stonehenge - if only one could talk to the builders and see the monument before it was desecrated by decay and vandalism! Others benefit from early written and sculpted codices. Archaeoastronomy can even be approached via anthropology. Here, careful discussions with extant primitive tribes can lead to finding links with the astronomical practices of the distant past.

The book's scope is vast. The authors successfully give each geographical region a coverage proportional to its relative importance. Unlike in many earlier works on archaeoastronomy, the Mediterranean region does not dominate and the legacies of Mesoamerica are given due recognition. It is profusely illustrated and much care has been taken with the production of the descriptive figures. There is also a 50-page reference section and a thorough index.

The conclusion is that all ancient civilisations found a use for astronomy to a greater or lesser extent. In many instances astronomically related ideas were spread between cultures; this intellectual diffusion was encouraged by trade, warfare, conquest and general adventuring and inquisitiveness. But in other cases different cultures approached astronomy independently. It is fascinating to see how these parallel pathways often lead to similar conclusions and associations.

David Hughes is professor of astronomy, Sheffield University.