Monday, March 07, 2005

Night has a shape

posted by Chet at 1:42 PM UTC

Earth wears its shadow like a tall, skinny wizard's cap. The cap fits snugly on the brow of the spinning Earth along the line of twilight and dawn, and reaches out to a vertex three times further than the Moon. If the Earth were a grapefruit, the apex of night would be 60 feet away -- a tall, skinny wizard's cap, indeed!

Everything outside of the conical shadow is bathed by the light of the Sun.

Percy Bysshe Shelley saw the shape of night in his mind's eye and turned it into one of the most beautiful astronomical images in all of poetry. In Prometheus Unbound, the Earth speaks these lines:

I spin beneath my pyramid of night
Which points into the heavens, dreaming delight,
Murmuring victorious joy in my enchanted sleep;
As a youth lulled by love-dreams faintly sighing,
Under the shadow of his beauty lying,
Which round his rest a watch of light and warmth doth keep.

Every object in the solar system wears a conical shadow -- every planet, every moon, every grain of dust. The solar system is as prickled with nights as a porcupine is prickled with spines