Why astronomy? This seems like a silly question, but it's not. In the modern age, stars play a lesser role for us than they did the ancient people of Earth. We do not know when the formal study of the stars and planets began. People use to think it began with the Egyptians, but we know now from thousands of mesolithic monuments that astronomy was a well-developed science long before Egypt. The study of the stars and the relationship of the sun and the moon were vital to ancient people. They told time by the stars; they navigated by them, and the stars were their calendars. Although we like to think of the first calendars being solar or lunar, the first calendars were also stellar. The rising and setting of the stars were far more accurate in predicting seasons and time than the sun and moon. The stars were so important to the ancients, the many of our myths are stellar related.
If you can imagine for a moment the night sky. If you are way out in the country, you would notice several things more than in the city. In the city, we know if the moon is out and we can see a few bright stars and planets. In the country, you notice the Milky Way. It stands out in a swath across the sky. And you notice stars, thousands and thousands of them. The stars seems to move around and arc overhead, the moon and planets with them. But if you were to go out night after night, the moon would be in a different postion with relation to the background stars. So would some of the planets. And each night, a bright star that you had picked out would rise later and later each evening. You would quickly notice that everything in the night sky is in motion. As you can see from this picture, it is almost impossible to pick out constellations by some shape. We know the shapes of some of the star patterns, like the belt and rectangle of Orion or the Large and Small Dippers. What seems to stick out to you is that some of the stars are much brighter than the others.
Humans recognize things easily, but they also convey that information to others. To do this through language, they use a mnemonic, or a story attached to what they saw, heard, or experienced to remember and help others remember the information. Stars are sometimes grouped in memorable patterns. This star constellation is familiar to most as Orion, the Hunter. All over the world, people tell constellation stories. All over the world, they also made viewing areas oriented toward the rising or setting of star groups. Although we don't know for sure what all the standing stones were used for, it is obvious that many were oriented toward the rising sun or moon or stars.
In England, there are figures that were cut into the chalk downs in the south. One is of a horse, two are of men. This one, called the "Long Man", holds two rods. Many have speculated about their function, but when you realize that the man is aimed up a hill and looks south, you can see that the setting of Orion happened over his head at mid-winter over 4000 years ago. It is unclear whether the man was a Green Man, a hunter, a farmer or a pigrim. If you've every cloud-watched, you know how compulsive humans are with making up stories about figures. Much of mythology is about the night sky.
You've probably heard the question, "what's your sign?" The zodiac consists of constellations that are on the same path as the sun and the moon and the planets called "the plane of the ecliptic." In the Solar system, the planets also pass around the sun in the same path. This led to a long history of mapping the sun, moon, and planets as they appeared to pass before certain star groupings. Many of the bright stars in this path happened to be at regular intervals. So, it was possible to mark out the night sky into seasons. Aldebaran is a very bright star in the a group called Taurus, a mnemonic created by ancient peoples to remember the group as a bull. It was a very dominant constellation in winter. The last viewing of Aldebaran at night happened right before spring. On almost the exact opposite of this equatorial ring of stars, was Antares (anti-Taurus), a summer constellation. When Antares could no longer be viewed at night, winter had come. In the North, Antares was part of the wolf of Ragnarok, or the passing of the world into ice. In the south, Antares became a scorpion, or Scorpio. A mid-winter star that was very bright was Regulus. Regulus was made into the heart of a lion, or Leo. When the sun passed into Leo, it was summer.
The stars appear to move because Earth is moving. From Earth, the sun and the moon both appear to be passing around the sky against a backdrop of moving stars. The background of stars is called "the celestial sphere" upon which everything appears to move in very regular intervals. When the sun is in the sky, we cannot see anything else except the moon. during a full solar eclipse it is possible to see the stars, but only as we can see them at dawn or sunset. Moving around this backdrop of stars, the sun and the moon appear to be at the same place during the year or month. But it is not perfect, which making keeping time very interesting.
Here, in my Star Gazer program, I have made a screen shot of a map of the night sky as it would have appeared in 1970 BCE, just before the time of Stonehenge. I have the major star marked in blue, the planets and points on the sphere marked in yellow and the Milky Way is a pink outline. Here, the sun is rising in Leo, so it is summer. The map says that it is July 24. There is a full moon just setting on the right. We see the Milky Way as a bridge across the sky. There were many aspects the the ancients could track: the orientation of the galaxy, the positions of the sun and moon, the positions of the planets, and the orientation of the stars and their positions. The most important of these was: the galaxy's orientation, the cycle of the sun and moon, and the season's changing based on the stars. The orientation of the galaxy is in another article. What we see at most sites like Stonehenge is the tracking of the sun and moon. They move at different speeds though the sky, so if we are to mark when they are in the same position at a full solar eclipse, they will not be back in that exact position for 56 years. They are close at one-third of that time, roughly nineteen years. They are close at odd times, of five, eight and eleven years. The full Metonic cycle of 56 years is exactly the number of posts that surrounded Stonehenge, a coincidence that made people take a deeper look at the monument as part of an ancient astro-calendar.
Here we are three months later, with a full moon. The orientation of Stonehenge is SW, in the direction of this clump of stars around the moon. I've overlayed a map of Stonehenge proper with the Avery Circle (56 posts) and you can see that the orientation of the monument is toward the setting of Sirius (the brightest star.) You can pull apart almost any myth about the world's creation or ending and find a stellar mnemonic about the seasons. From Hercules to Ragnarok, from Zodiac Signs to the Axis Mundi, Stonehenge and the Serpent, we are still culturally swimming in ancient astronomy.
The Babylonians loved the number four and tried to divide up the night sky into quadrants. However, there is no evidence to support the Egyptians or the Minoans or Stonehenge peoples dividing everything into four. Four seasons easily becomes six when we look at star dates. The Egyptians had six seasons. This is a modern calendar. If we back it up, we can see that the Egyptians began their year with the heliacal rising of Sirius, or the point when it is first visible just before dawn. This was in June (North, now Aug 1) when the Nile also flooded from the melting snows and heavy rains to the south. Calendars also depended on latitude, climate, and age. Because there is a slight movement of the Solar system through the galaxy, what was once the Pole star or the Equinox constellation changes over a long time. This movement is called "precession of the equinoxes" or "polar drift."
Please continue for more ancient astronomy!