Ancient astronomers achieved remarkable feats that were built on many thousands of years of watching the sky. How did they accomplish so much without using the technology we have available today? Welcome to the study of archeoastronomy.
Ancient astronomers had different tools—and different goals—than do modern astronomers. Yet despite these differences, we also have a rich heritage coming to us from ancient astronomy. Ancient astronomers made remarkable discoveries and achieved remarkable feats that were built on many thousands of years of watching the sky. Perhaps the most famous example from ancient astronomy is Stonehenge.
Watch lecture 1 from the series The Remarkable Science of Ancient Astronomy, and follow along with the summary below.
- Stonehenge is a monument located on the Salisbury Plain, in south- central England, just under a 2-hour drive from London. The basic structure is a set of standing stones set in a circle that surrounds a horseshoe-shaped set of standing stones.
- The central set of stones consists of 5 pairs of very tall stones topped by a horizontal stone, called a lintel. Each of these so-called trilithons have the lintel stone pegged to the vertical stones with a mortise-and-tenon joint, which has a knob sticking out of the top of the standing stone that fits into a hole in the lintel so that the lintel cannot easily fall off. The tallest stone reaches 24 feet from the ground; the biggest stones weigh 40 tons.
- The horseshoe of trilithons is surrounded by a circle of stones. The basic circle originally consisted of 30 standing stones, each topped by 2 lintels to form a continuous ring running around the top. The stones in the circle are made of a sandstone rock type called sarsen.
- Each of the stones has been pounded into a roughly rectangular shape. This shaping of stones is rare among stones at other contemporaneous stone circles around the British Isles. Many of the original stones have fallen down or been taken away.
- The immediate vicinity of Stonehenge has a complex array of remains that go far past the basic monument. Centered on the monument is a circular ditch with a radius of 180 feet. The chalk dug out from the ditch was heaped into a bank running just inside the ditch. The ditch doesn’t form a complete circle; there are sections to the south and to the northeast that form openings into the central area.
- The opening toward the northeast forms part of a long linear feature called the avenue, which is defined by 2 parallel ditches running out from the circular ditch around the monument. This avenue goes perfectly straight for 2000 feet before veering to the right and ultimately running down to the River Avon.
- At the start of the avenue, where it touches the circular ditch, is a now-fallen dressed, or cut, rock known as the Slaughter Stone. This name invokes an image of ritual sacrifice, and people imagined the victim laid out on the stone.
- Just a bit outside the ditch, just off-center in the avenue is the upright Heelstone, which is famous because it defines the astronomical alignment of Stonehenge; that is, on the morning of the June solstice, the longest day of the year, if you’re at the center of Stonehenge, you’ll see sunrise over the Heelstone.
- There are many more stones and pits within the central ditch area, including a circular array of 56 pits called the Aubrey Holes. Nearly on top of these Aubrey Holes are 4 undressed stones that define a rectangle called Station Stones, 2 of which are surrounded by small ditches.
- Close around the basic stone circle are 2 more rings of holes that are irregularly spaced, and the center of the whole circle has a stone called the Altar Stone, which is now fallen and lying mostly buried under a lintel fallen from a trilithon.
- Stonehenge and its surroundings were made by a culture of Neolithic farmers known as Beaker people. They flourished throughout the British Isles and western Europe from the Late Stone Age to the Early Bronze Age. Stonehenge was built in stages, from roughly 3100 B.C. to 1600 B.C.
- The larger area surrounding Stonehenge is filled up with contemporaneous monuments that are dominated by burial mounds of many types. And there are a variety of other circles, or henges, throughout the area.
- Stonehenge was built with only primitive tools. Archaeologists find many broken antler tips inside the pits and ditches. These were the tools used to dig in the ground.
- Perhaps the most impressive point about the construction is that the extremely heavy stones were transported tremendous distances to be brought to Stonehenge. The big sarsen sandstones were dragged 18 miles from Marlborough Downs to the north. The smaller bluestones were dragged, and perhaps floated by raft, from quarries in Wales about 150 miles away.
THE ARCHAEOASTRONOMY PARADIGM
- The word “archaeoastronomy” can generically refer to the study of astronomy as it was practiced in ancient times. But there is also a much more specific meaning having to do with how ancient peoples built monuments aligned to the stars.
- The basic paradigm of archaeoastronomy is that ancient peoples incorporated astronomy into their old temples and other structures by pointing to a particular direction on the horizon where something significant happens.
- Such directional symbolism is universal in all cultures. The reasons are widely varied, but they always exist, always go back to the astronomy, and often are charged with strong cultural traditions. For most ancient peoples, these alignments are a common way to interact with the sky. But the astronomical origins might have been partly lost on the common folk.
- The basic setup of archaeoastronomy is that some now-ancient building is pointing at some direction on the horizon. This pointing might use some obvious main axis of the building plan, or the architecture can somehow indicate a position for an observer to stand, plus some stone marking a direction to look. The position for the observer to stand could be given by the center of a circle, a throne, a statue, or the top of a grand staircase. The direction to look might be marked as down some central axis, along a wall, perpen- dicular to a wall, or by some distant stone.
- The astronomically significant direction on the horizon is usually one of the 4 cardinal directions or one of the 4 solstitial directions. The 4 cardinal directions are north, east, south, and west.
- The 4 solstitial directions are toward either sunrise or sunset on the dates of either the summer solstice or the winter solstice. These solstitial directions are the Sun’s extreme north during summer and the Sun’s extreme south during winter. The days of the solstices are close to June 21 and December 21 every year. For people in the Southern Hemisphere, summer and winter have to be reversed.
- In addition, there is a lot of talk about the Moon’s equivalent extreme rise and set directions. Also, in rare cases, the significant direction can be toward the rise of some bright star.
- Halfway between the solstice dates, the Sun will equally illuminate both hemispheres, and these dates are called the equinoxes, which are close to every March 21 and September 21. There’s nothing special that happens on the days of the equinox, but the solstices are when things turn around—both the sunrise changes and the season changes.
- With the seasonal cycle being so critical for all ancient peoples, it’s plausible that these would be commemorated in stone and architecture. In all, archaeoastronomy is looking at the nearly universal commemoration of the 8 cardinal and solstitial directions, rarely including star-rise directions, in the monuments and myths of ancient cultures.
ARCHAEOASTRONOMY AT STONEHENGE
- If you stand at the center of Stonehenge on June 21, you can see through a gap between 2 upright stones, under their lintel, with the Heelstone viewed in the middle just poking up above the distant horizon, and that is where the solstice Sun rises.
- This basic astronomical alignment was recognized from antiquity, but it was only in 1965 that this alignment started a worldwide obsession with Stonehenge. This began with the publication of astronomer Gerald Hawkins’s best-selling book, Stonehenge Decoded
If you stand at the center of Stonehenge on June 21,
you can see through a gap between 2 upright stones, under their lintel,
with the Heelstone viewed in the middle just poking up
above the distant horizon, and that is where the solstice Sun rises.
THE REMARKABLE SCIENCE OF ANCIENT ASTRONOMY
- On the back of the book, the blurb pushed one of the strong selling points—that all of the many astronomical calculations were made with a “computer.” The public was intrigued by the recovery of long-lost ancient wisdom. This book launched storms of protests from archaeologists. It also launched the whole field of archaeoastronomy.
- Hawkins’s computer work confirmed the alignment on the solstice sunrise. But he also proposed a series of other alignments and claimed that Stonehenge is an analog computer to predict eclipses. This led to the view that Stonehenge was a marvelous astronomical observatory that was millennia in advance of the rest of the world in science.
VIEWS OF STONEHENGE
- Starting in 1965 with Gerald Hawkins, the astronomical alignments and the eclipse computer were widely taken to be the critical components of Stonehenge, to the exclusion of most else. With this, astronomers were telling us that Stonehenge was just one big astronomical observatory and computer. The fusion of the 2 themes was that some mystic Druid astronomer-priests ruled their society and built Stonehenge for their own astronomical observatory.
- In the last century, modern pagans invented a new religion centered at Stonehenge. These neo-Druids dress up in white robes, sometimes with fake beards, and parade around Stonehenge carrying large staffs. These groups model their rituals on what they imagine was done by ancient peoples, but there’s no connection to or basis with the real Iron Age Druids of Britain.
- On the summer solstices from 1974 to 1984, Stonehenge became the venue for a free festival, featuring rock bands and free drug use. These hippies would get into gang fights with motorcycle gangs. The British police finally suppressed this in 1985, but the hippies fought back, in what became known as the Battle of the Beanfield, with arrests of 537 people.
- All of this rebranding of Stonehenge became absurd in 2003, when a British medical journal ran an article claiming that the monument design was intended to model female genitalia. The authors were a pair of Canadian gynecologists.
- Through all this, archaeologists were telling us that Stonehenge and all the tombs and burial mounds in the area were just part of a huge Neolithic burial grounds. It seems that we’re fated to have every special interest group picturing Stonehenge according to their own interests. But the real picture for Stonehenge archaeoastronomy is much more complex, detailed, and confident.
QUESTIONS TO CONSIDER
- What do you identify as the archetypical exemplars for ancient astronomy? In other words, what are the most famous discoveries, the most exciting astrolocations, the most important topics, and the greatest astronomers of antiquity?
- In old times, for a relatively small number of scholars, ancient astronomy is various lines of theory and observations that we might call science. But these are not the concerns of the vast majority of astronomers or ordinary people throughout ancient times. What were the primary concerns of working ancient astronomers? What do you think were the primary concerns and sky interactions for commonplace people?
From the lecture series The Remarkable Science of Ancient Astronomy
Taught by Bradley E. Schaefer, Ph.D.