Obelisks

Video Transcript

Last time in Musings on Nature, I talked about sundials and their place in history. Today I’m going to be talking about Obelisks - their meaning, and their mathematics, and their cultural origins.

Obelisks – I have been producing them for about 25 years in various materials. However mankind has been creating them for well in excess of 5,000. The clean lines of the obelisk, they had metaphysical properties.They were a single finger of light coming down from the heavens, but the main feature from them is that the shadow casting component allowed the time to be calculated. I guess it was a stick in the ground that allowed you to work out when the sun is at its highest. The angle of the sun producing the shortest shadow – that is midday. And from that moment on they started to use the shadow and the passage of the shadow as a means of calculating and dividing up the day. It was a very elemental sundial.

Obelisks can tell the time

We actually create them now to tell the time, show Midsummer's Day, the spring and autumn equinox, and Midwinter’s Day.And indeed any date non-related in between. Very simply, the height of the sun touching the top of the shadow, top of the obelisk, and casting the shadow. Midsummer, it’s going to be at its very highest; and midwinter it’s going to be at its longest.And it's basic trigonometry, and, uh, it creates a very elegant and reassuring passage of time.

Working out the world

In ancient history, when there was not as much clutter going on in our lives, this, this rudimentary information would have been something that people would have developed, and it formed the basis of an understanding of the heavens. And it was also the method by which navigation, the, the concept of the height of the sun: a Chaldean priest, 300 BC called Berossus in Egypt used a stick in the ground, elementary trigonometry to work out latitude, and at the same time, on the same day many hundreds of miles away a shadow, and the length of a shadow down a well using trigonometry on the same day, and because of the distance in between he was able to calculate the circumference of the Earth. Don’t try this at home without a calculator.

But he did it effectively in isolation, and came up with a very accurate estimate of the circumference of the earth. 1,500 years later we were still daring to think that the world was flat.

It's all in the tip

But it's the tip of the shadow that is the time-telling moment, and by placing a stone at the end of that shadow and watching it, even in the time that I have been talking now, it would have moved a few inches. It is a constantly dynamic, changing piece of sculpture.

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