Monday, March 05, 2007

The shape of night

Saturday evening we just squeaked into the show for the total eclipse of the Moon. The eclipse was already at totality as the Moon rose. Over there across the Atlantic, in deep night, they got to see the Moon slip into the Earth's shadow.

Clouds on our horizon obscured the best part of the affair -- the dusky colors of totality, the Moon lit by a faint wash of sunlight refracted into the shadow by the Earth's atmosphere. The color of an eclipsed Moon is hard to predict exactly, since it depends on such things as the amount of dust in Earth's atmosphere. We did get to watch as the Moon drifted out of the Earth's shadow and resumed its fullness.

The Earth's shadow is a long thin cone pointing away from the Sun -- as long and thin as a fencer's rapier -- about twice as wide as the Moon at the Moon's distance from Earth. Whenever I watch a lunar eclipse, I never fail to think of these wonderful lines the Earth speaks in Shelley's Prometheus Unbound:
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 in love-dreams faintly sighing,
  Under the shadow of his beauty lying,
Which round his rest a watch of light and warmth doth keep.