Ancient Astronomy — Part 1
What is the role of astronomy in everyday life, and what was its role for ancient cultures? Imagine yourself being transplanted to the African Savannah 40 or 50,000 years ago. In the cradle of humanity, as a hunter-gatherer, living by your wits on the Savannah, what use would you make of astronomy? Clearly, you would need to hunt or grow crops that would sustain you, you would need to know how to get back to your encampment by the end of the day so as not to be prey for the wild animals, and you would want to keep track of time. You could plan the seasons and your abodes for the winter and summer, or understand how long a pregnancy cycle would last, or what the cycles of life would mean fitting into the cycles of the sky around you. Ancient people cared about astronomy, and this was almost built into their DNA because they watched and learned from the sky. It was essential in their everyday lives in ways that it simply isn’t anymore. We’ve immunized ourselves from the night sky, because most of us live in cities or suburbs, and I myself, rarely see a truly dark sky.
But let’s imagine what someone in tune with the sky, living by their widths, and looking at that pristine dark sky unaltered by city lights, would’ve seen thousands of years ago. They would have used the sky to keep time, to track the seasonal cycle, they would have watched the lunar cycle as the most prominent object in the night sky, and they would have monitored the phases of the moon. What would they have made of these phenomena? Remember the ancient cultures, the sky, and astronomy were not just a subject in a textbook. The sky was a map, a calendar, and a clock. An example of the importance of the sky to ancient astronomers comes from the gorgeous cave paintings at Lascaux and Altamira, in Southern France and Spain. Unfortunately, these cave paintings are so fragile, that most of these caves have now been sealed off and cannot be visited by the public. However, the paintings exist online and you can see the gorgeous animals they drew, that they hunted. But also the pattern of dots, which in the sum of all these paintings, show clear signs they were keeping a lunar calendar to mark time in their ancient cultures.
If we go around the world looking at how astronomy was used by various different cultures, who didn’t communicate with each other, we see variations that are quite specific. For example, in equatorial regions where the seasonal cycle is simply not very obvious, there are no four seasons as we have in temperate Northern climes. Time is kept in a different way. Another common feature of ancient cultures is something called a gnomon, which is a Greek word representing stick. It is at simplest a stick, which cast a shadow from the sun as the sun rises and sets. If you trace out the path of that shadow and then trace the envelope of that shadow over a seasonal cycle, you can turn it into a calendar, and thus be able to predict the time of year. Perhaps the most iconic structure from prehistory, that tells us about astronomy and culture is Stonehenge in the United Kingdom.
Stonehenge sits on the Salisbury Plain, on a plateau with no towns and forests, nothing nearby, rises out of the planes. These two concentric circles of stone, pillars, the largest of which weigh 150 tons. Remarkably, the culture that built this, imported these stones from as much as 500 miles away. Still, there’s speculation as to why and how they brought the stones from so far away, and why they positioned Stonehenge exactly where it was, there was perhaps an astronomical reason. Five thousand years ago, Stonehenge started life as an urban work and closure, and it wasn’t until around 2600 BC, that the first stones arrived. These were blue stones, dragged all the way from west Wales. The bluestone circle was taken down 200 years later in 2400 BC. It was at this point that the greatest building projects in ancient Britain got underway, the first of the huge sarsen stone trilithons were erected. The bluestones were then slotted into the center of the ring, hinting at symbolic importance. Then another outer circle of blue stones was added. Before the massive circle of sarsen stone trilithons enclosed the whole thing, this was the heyday of the monument and it lasted for about 500 years until around 1900 BC. Over the next 4,000 years, Stonehenge fell into a long slow decline. Neglect, theft, and time producing the iconic structure we’re left with today.
In work dating back to the 1950s, archaeoastronomer’s have investigated the alignments of the stones at Stonehenge and decided that it represents an exquisite calendar, not just a solar calendar but an eclipse predictor able to predict patterns in the sky occurring on near-century timescales. This is a monumental piece of work built over one and a half millennia. Just think of how many generations of coherent activity of this early culture were required to create Stonehenge!
