Before the Pyramids: Cracking Archaeology's Greatest Mystery by Christopher Knight, Alan Butler
Authors: Christopher Knight, Alan Butler
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winter solstice, in 3500 BC was also where Sirius rose ahead of it. As Sirius reached around 4° it stood over the centre of the avenue between the henges, like a guiding light – and a few hours later the Sun did the same thing.
If Orion’s Belt is a famous group of stars, Sirius is even more famous. This is partly because it is the brightest star in our skies and has been so for as long as human beings have walked the Earth. The importance of Sirius in a mythological sense cannot be underestimated and it appears in the folktales, and even the religion, of almost all ancient civilizations. It was of the greatest relevance to the ancient Egyptians and to the people of Mesopotamia, and was doubtless just as important to the henge builders of ancient Britain.
If we look at figure 12 we can see how, in the night sky, a direct line taken across Orion’s Belt to the south will lead to Sirius – indeed, Sirius has often been located using this technique – together with other parts of the night sky that were, historically, considered important for ritual reasons or for navigation.
So far so good, but the presence of both the midwinter Sun and rising Sirius immediately led us to realize something that had been puzzling for years; how did our ancient ancestors reconcile the differences between days marked out by the Sun and days as perceived by the stars – because they are distinctly different.
For most of us today, time is a simple matter of consulting a wrist-watch or our diaries. The new day begins at midnight and the next year is simply when the clocks strike 12 at midnight on 31 December. In reality these are arbitrary approximations – albeit very useful ones.
Figure 12. Orion’s Belt lining up towards Sirius
Time recording is based on astronomical observation of the movements of the Earth, and is torturously complicated. Days actually vary in length slightly, but a mean solar day is taken as having 24 hours of 60 minutes, split again into 60 seconds – giving a total of 86,400 seconds to the day. However, if we watch any star such as Sirius, it will return to the same point in the sky in 86,164 seconds (236 less than the solar day). This is called a sidereal day. It occurs because the stars are actually stationary and their apparent movement is due to the Earth’s rotation on its axis. The solar day is longer because it also takes into account the planet’s movement around the Sun, which makes one turn of the Earth seem to take longer.
In one orbit of the Sun (a year), all those 236-seconds difference between the sidereal and mean solar days add up to exactly one extra day. So there are 365 sunrises in a year but 366 star rises.
It is clear that the Neolithic astronomers of Britain fully understood this difference. If we take the gap in any one of the Thornborough henges in the southeast and view it, day-by-day across a year, from the centre of the henge, this is what we would notice. For the Sun to rise to the same point over the gap in the henge on two successive occasions would take 365 days. Meanwhile the star Sirius would have risen 366 times before returning to the same point.
Figure 13. The spin of the Earth
This apparently mysterious state of affairs would, no doubt, have fascinated these early astronomers and, in any case, their virtual obsession for the number 366 had shown us long ago that they were quite conversant with a year made up of sidereal days – which has no modern name but which we call a ‘star year’. The importance of this realization cannot be understated, and once again the super-henges had served to confirm our predictions regarding the methods and knowledge of the ancient British astronomers.
A Sirius Henge
However, the presence of Sirius appearing in the southeastern gap at the winter solstice seemed to confirm that the three henges might well have been constructed as a faithful reproduction of Orion’s Belt. After all, Orion’s Belt in the sky points directly to
If Orion’s Belt is a famous group of stars, Sirius is even more famous. This is partly because it is the brightest star in our skies and has been so for as long as human beings have walked the Earth. The importance of Sirius in a mythological sense cannot be underestimated and it appears in the folktales, and even the religion, of almost all ancient civilizations. It was of the greatest relevance to the ancient Egyptians and to the people of Mesopotamia, and was doubtless just as important to the henge builders of ancient Britain.
If we look at figure 12 we can see how, in the night sky, a direct line taken across Orion’s Belt to the south will lead to Sirius – indeed, Sirius has often been located using this technique – together with other parts of the night sky that were, historically, considered important for ritual reasons or for navigation.
So far so good, but the presence of both the midwinter Sun and rising Sirius immediately led us to realize something that had been puzzling for years; how did our ancient ancestors reconcile the differences between days marked out by the Sun and days as perceived by the stars – because they are distinctly different.
For most of us today, time is a simple matter of consulting a wrist-watch or our diaries. The new day begins at midnight and the next year is simply when the clocks strike 12 at midnight on 31 December. In reality these are arbitrary approximations – albeit very useful ones.
Figure 12. Orion’s Belt lining up towards Sirius
Time recording is based on astronomical observation of the movements of the Earth, and is torturously complicated. Days actually vary in length slightly, but a mean solar day is taken as having 24 hours of 60 minutes, split again into 60 seconds – giving a total of 86,400 seconds to the day. However, if we watch any star such as Sirius, it will return to the same point in the sky in 86,164 seconds (236 less than the solar day). This is called a sidereal day. It occurs because the stars are actually stationary and their apparent movement is due to the Earth’s rotation on its axis. The solar day is longer because it also takes into account the planet’s movement around the Sun, which makes one turn of the Earth seem to take longer.
In one orbit of the Sun (a year), all those 236-seconds difference between the sidereal and mean solar days add up to exactly one extra day. So there are 365 sunrises in a year but 366 star rises.
It is clear that the Neolithic astronomers of Britain fully understood this difference. If we take the gap in any one of the Thornborough henges in the southeast and view it, day-by-day across a year, from the centre of the henge, this is what we would notice. For the Sun to rise to the same point over the gap in the henge on two successive occasions would take 365 days. Meanwhile the star Sirius would have risen 366 times before returning to the same point.
Figure 13. The spin of the Earth
This apparently mysterious state of affairs would, no doubt, have fascinated these early astronomers and, in any case, their virtual obsession for the number 366 had shown us long ago that they were quite conversant with a year made up of sidereal days – which has no modern name but which we call a ‘star year’. The importance of this realization cannot be understated, and once again the super-henges had served to confirm our predictions regarding the methods and knowledge of the ancient British astronomers.
A Sirius Henge
However, the presence of Sirius appearing in the southeastern gap at the winter solstice seemed to confirm that the three henges might well have been constructed as a faithful reproduction of Orion’s Belt. After all, Orion’s Belt in the sky points directly to
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