Everyone knows the Sun sets in the West... but as the Sun sets, the 
night rises. I’m in an airliner at 11,000 m. /36,000 ft. Below, there 
is a soft, even layer of cloud; on the ground, people will be talking 
about "overcast", but up here it’s "undercast". The sun descends 
below the sky-horizon behind me... and a clearly delineated band of 
darkness begins to spread upward ahead of me. Night is rising in the 
East. We are flying into the Earth’s shadow, which at this altitude 
has a neat and definite edge -- on one side, pale light; on the other, 
evening. As the planet turns, as we fly in the direction of its 
turning, the band of darkness grows wider and wider, the terminator 
climbing up the bowl of the sky. Strangely, the leading edge is a 
narrow, darker band, while the night sky following it is slightly 
lighter. However, the edges gradually soften and blur, and soon there 
is only twilight dimness ahead, and a lingering glow fading behind. I 
cannot tell now whether the softly rippled surface below is ocean or 
cloud; I only know it is not land because, if it were land, I would 
be able to see lights.  Overhead, one by one, the stars become 
visible. Then I look down again, and there are no more clouds below, 
and the lights of human endeavor shine up at the stars.