See the shadow of the Earth rise under the Belt of Venus

Most people in the world are taken in by the brilliance of the sunset. Suckers. Turn around in the opposite direction — and instead of looking at the sunset, you can watch the shadow of the Earth rise under the Belt of Venus.

You have to hand it to the Victorians. They excelled at coming up with restrained, yet slightly suggestive, names for things. As the sun set in the west, they turned to the east and noticed a bright pink band of glowing light slightly above a dark purplish band along the eastern horizon. They fluffed their bustles and and polished their monocles and called it The Belt of Venus, and then tittered behind their hands for a while. Cheeky scamps.

The patch of light pink sky and the relative darkness beneath it are the result of two phenomena. The first is the tendency of our atmosphere to scatter visible light. This is a good thing. It's one of the reasons it's possible for us to brighten our rooms with sunlight even when it isn't shining directly at us. The make-up of our atmosphere scatters blue light particularly well, which means a lot of it is filtered out when the sun sets. The increased distance rays from the sun travel through the atmosphere increase the amount of blue light is scattered all around, while the orange and red light makes it to the viewer. That reddish light keeps going through the atmosphere, past the viewer, to the far eastern part of the sky and then, probably, out into space again. But since the atmosphere does scatter some red light, some of that light shoots back to the viewer, making the eastern part of the sky glow pink.

What's that band of darkness that creeps up underneath? That's the curve of the Earth getting in the way of the sunlight. As the sun goes farther and farther down, the planet gets in the way and casts a shadow on the horizon. This is why it's such a better show than a sunset. You get to see the sunlight in the sky all day, but how often do you get the shadow of the entire Earth play out over the horizon?

Top Image: The Brocken Ina Glory

Via Sky and Telescope and ATopics.