Early Astronomy

As surviving records and artifacts make abundantly clear, many early cultures took a?keen?interest in the changing nighttime sky. But unlike today, the major driving force behind the development of astronomy in those early societies was probably neither scientific nor religious. Instead, it was decidedly practical. Seafarers needed to navigate their vessels, and farmers had to know when to plant their crops. In a real sense, then. human survival depended on knowledge of the heavens. The ability to predict the arrival of the seasons, as well as other astronomical events, was undoubtedly a highly prized, perhaps jealously guarded, skill.

The human brain’s ability to perceive patterns in the stars led to the “invention” of constellations as convenient means of labeling regions of the nighttime sky. The realization that these patterns returned to the night sky at the same time each year met the need for a practical means of tracking the seasons. Widely separated cultures all over the world built elaborate structures to serve, at least in part, as primitive calendars, but often early experts on astronomy enshrined their knowledge in myth and ritual, sometimes turning sites used for astronomical observation into places for religious ceremonies.

Perhaps the best-known such site is Stonehenge located on Salisbury Plain in England. This ancient monument, which today is one of the most popular tourist attractions in Britain, dates from the Stone Age. Researchers believe it was an early astronomical observatory of sorts-not in the modern sense of the term (a place for making new observations and discoveries pertaining to the heavens)–but rather a kind of three-dimensional calendar or almanac, enabling its builders and their descendants to identify important dates by means of specific astronomical events. Its construction apparently spanned a period of about 17 centuries, beginning around 2800 B.C. Additions and modifications continued to about 1100 B.C, indicating its ongoing importance to the Stone Age and, later, Bronze Age people who built, maintained, and used Stonehenge. The largest stones weigh up to 50 tons and were transported from many miles away.

Many of the stones are aligned so that they point toward important astronomical events. For example, the line joining the center of the inner circle to the so-called heel stone, set off some distance from the rest of the structure, points in the direction of the rising Sun on the summer solstice (the longest day of the year). Other alignments are related to the rising and setting of the Sun and the Moon at other times of the year. The accurate alignments (within a degree or so) of the stones at Stonehenge were first noted in the eighteenth century, but it was only relatively recently– in the second half of the twentieth century, in fact–that the scientific community began to credit Stone Age technology with the ability to carry out such a precise feat of engineering. While some of Stonehenge’s purposes remain uncertain and controversial, the site’s astronomical function seems well established. Although Stonchenge is the most impressive and the best preserved, other stone circles, found all over Europe, are believed to have performed similar functions.

The early Chinese also observed the heavens Their beliefs attached particular importance to omens” such as comets, which are seen in the night sky only occasionally, and “guest stars”-stars that appeared suddenly in the sky and then slowly faded away-and they kept careful and extensive records of such events. Twentieth-century astronomers still turn to Chinese records to obtain observational data recorded during the Dark Ages (roughly from the fifth to the tenth century AD.), when turmoil in Europe largely halted the progress of Western science. Perhaps the best-known guest star was one that appeared in AD.1054 and was visible in the daytime sky for many months. We now know that the event was actually a supernova-the explosion of a giant star-which scattered most of its mass into space. It left behind a remnant that is still detectable today, nine centuries later. The Chinese data are a prime source of historical information for supernova research.?

1.As surviving records and artifacts make abundantly clear, many early cultures took a?keen?interest in the changing nighttime sky. But unlike today, the major driving force behind the development of astronomy in those early societies was probably neither scientific nor religious. Instead, it was decidedly practical. Seafarers needed to navigate their vessels, and farmers had to know when to plant their crops. In a real sense, then. human survival depended on knowledge of the heavens. The ability to predict the arrival of the seasons, as well as other astronomical events, was undoubtedly a highly prized, perhaps jealously guarded, skill.?