In Shelley's Prometheus Unbound, the Earth speaks these wonderful words:
I spin beneath my pyramid of nightBeautiful words, but beautiful too that the poet has fixed in his mind's eye a geometry that was first imagined by astronomers in the ancient Near East.
Which points into the heavens, dreaming delight,
Murmuring victorious joy in my enchanted sleep;
As a youth lulled in love-dreams faintly sighing,
Under the shadow of his beauty lying,
Which round his rest a watch of light and warmth doth keep.
Night as a pyramid! A long, skinny cone of darkness. A wizard's cap of shadow cast by the Earth into the illuminated space near the Sun.
Those ancient astronomers conceived of that cone of darkness and used it to explain eclipses of the Moon.
As I watched the eclipse Monday night I tried to imagine the shape of night, as long and skinny as a rapier. And the Moon, as typically happens twice a year, on course to collide with that pyramid of shadow, which at the Moon's distance is a bit less than three times as wide as the Moon. That pyramid of shadow under which he Earth, like a youth lulled by love-dreams, drowsily spins.
Every object in the solar system wears a conical shadow pointing away from the Sun. Even the helmeted head of a spacewalking astronaut wears a wizard's cap of darkness one hundred feet long. The solar system is as prickly as a hedgehog with spines of darkness.
(This post originally appeared in December 2010.)