Chapter 2: Early Astronomy

An image of Stonehenge.

Mysterious rings of upright stones dot the hills and dales of England. The most famous is a monument called Stonehenge, which many people know only as a ring of giant stones standing silently in an ancient field. Few people realize that other prehistoric structures abound in the nearby landscape. For example, a broad "avenue" lined by earthen banks leads out of Stonehenge across the plains for about ½ kilometer (1/3 mile) toward the northeast. What was the purpose of such enigmatic features? In the Middle Ages, people believed that King Arthur's magician, Merlin, built them. Others attributed them to ancient wise men called Druids. In the 1720s, a lone scholar named William Stukeley visited many of the ancient monuments and made careful drawings of these prehistoric wonders. Stukeley was the first person to record a curious fact. The avenue leading from the center of Stonehenge points exactly toward the spot on the horizon where the Sun rises on the longest day of summer.

What could the alignment at Stonehenge mean? More than a century later, in the 1890s, English astronomer Norman Lockyer noticed that other ancient monuments were oriented according to astronomical principles as well. Lockyer rediscovered Stukeley's work and then synthesized it with his own observations to conclude that Stonehenge was a prehistoric astronomical temple designed specifically for ceremonies on the longest day of summer. According to Lockyer, ancient people from various parts of the world who lived from 3000 B.C. to 1000 B.C. knew of subtle astronomical cycles. For example, they knew how to construct calendars accurate enough to reliably plant crops from year to year. They knew of the variations in the motions of the planets among the stars. Some cultures were even able to discover that the constellations had subtly changed their shapes and positions over the centuries.

Archaeologists and other scientists of the day ridiculed Lockyer's ideas, arguing that ancient people could not have gained such extensive knowledge. Today, most scientists agree with Lockyer. Ancient architects in various cultures sometimes used astronomical knowledge to locate and orient buildings and monuments. We should avoid two tendencies when speculating about ancient cultures. The first is to assume that such people were unsophisticated because they had primitive technology. Remember that the brain function and language skills of humans have not changed for many thousands of years — the people who built Stonehenge were just like us. The second danger comes when we ascribe modern motives to ancient cultures. Stonehenge was not an observatory in the modern sense of the word. It almost certainly had a ceremonial and spiritual function as well. We can only make educated guesses at the intentions of the builders since they left no written language.

Building Stonehenge was a terrific undertaking! The circular embankment and solstice avenue were built around 2500 B.C. During the time that followed from 2100 B.C. to 1500 B.C., workers dragged the huge stones from quarries as far as 380 kilometers (240 miles) away and erected them to form the famous structure in the center of the ring. Archaeologists think that Stonehenge's purpose gradually shifted from precise observation to ceremony; by medieval times, its original function had been forgotten. Why would ancient people go to such enormous trouble to build this monument? Why would they take such an interest in the sky and astronomy? The sky serves as a map, a clock, and a calendar. The "cycles of the sky" have been important to every culture throughout history.

Stonehenge is just the biggest and most famous example of many stone circles that have been found across northwestern Europe. Also called megaliths, these structures were built around 3000 B.C. and after, in the Late Neolithic and Early Bronze Ages. There are over 1000 in the United Kingdom alone. Most of these stone circles were built for ceremonial purposes and seem to have no obvious astronomical function. However, statistical methods applied to many stone circles find an excess of alignments associated with the positions of the Sun and Moon. Stonehenge was not unique in having an astronomical purpose.