Earth's Terminator

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If you've ever been on a mountain, or even at a high elevation, then you might have seen Earth's terminator. On the moon, the terminator is the light between night and day. The same is true on Earth, but the only way we Earthlings can see it other than being in space is to look the direction away from the sun, just after sunset, from a high elevation. What you will see is something like the image above, which I took on June 18, 2004, from Kitt Peak in Arizona.

The dark blue just at the telescopes is night in Earth's atmosphere -- the shadow of the Earth itself cast upon the atmosphere. The bands of color immediately above it is where sunset is occuring in the atmosphere due to the Sun setting below Earth, as seen from that location in the atmosphere. This is also known as the "Belt of Venus."