In my last post I talked about archaeoastronomy, a fascinating blend of astronomy and culture. Since the Sun and Moon are the dominant features in our sky it’s not surprising that their movements are the focus of many ancient monuments. Reading around the subject a little more I was intrigued to discover that another less well-known celestial phenomenon, the zodiacal light, may also have influenced Ancient Egyptian art, and even the shape of at least one of their pyramids.
Dark skies
Many people today have never seen or even heard of the zodiacal light. It’s a subtle feature that is only visible in a night sky free of light pollution, but that wasn’t an issue for the Ancient Egyptians – it would have been clearly visible in their clear and dark desert nights. It’s a cone-shaped whitish glow that extends from the horizon high up into the sky along the ecliptic, the path that the sun appears to follow through the sky. The ecliptic passes through the constellations that are the signs of the zodiac, hence the name, ‘zodiacal light’.
The ghostly glow is about the same brightness as the Milky Way and appears in the west soon after dark or in the east an hour or so before dawn, which is why it’s also known as the ‘False Dawn’. In the northern hemisphere it is best visible near the spring equinox for the evening version and the autumn equinox for the morning one, vice versa in the southern hemsisphere, because at that time of year the ecliptic is most perpendicular to the horizon.
So what is the cause of this mysterious-looking spectacle? It’s nothing less than sunlight reflecting off dust grains orbiting in the inner solar system, believed to be the remains of the 4 billion-year old solar nebula from which our Earth and all the other planets formed. A glimpse far back ito the dawn of our solar system.
Crowns and Pyramids
And where do the Ancient Egyptians come into this story? One example is the argument by some scholars that the shape of one of the Pharoah’s crowns, the White Crown of Upper Egypt, which appears in much of their art, was inspired by the zodiacal light’s slightly inclined and curved triangular shape. Other have argued that the so-called ‘Bent Pyramid’, coated in pale-coloured limestone and unusual due to ta change in the inclindation of its slope part way upt was designed to represent the zodiacal light through its shape and colour.
1. ES0/Y. Beletsky https://www.eso.org/public/images/zodiacal_beletsky_potw/
2. https://commons.wikimedia.org/wiki/Category:White_crown#/media/File:MentuhotepII.jpg (Public Domain)
3. ESO/H.H. Heyer https://www.eso.org/public/images/vlt-mw-potw/