Summer Solstice

StarDate: June 20, 2010

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If you just can't wait to greet summer, then you need to get up pretty early tomorrow. That's because the season arrives at 6:28 a.m. Central Daylight Time -- the moment of the summer solstice here in the northern hemisphere.

The solstice marks the Sun's northernmost point in the sky for the entire year. After tomorrow, it'll start to head south -- a motion that it'll continue until the winter solstice in December.

The Sun isn't really moving, though -- Earth is.

Our planet is tilted on its axis, so as we orbit the Sun, the axis tilts in different directions relative to the Sun. Right now, the north pole is dipping toward the Sun, so it's bathed in constant sunlight. At the same time, the south pole is tilted away from the Sun, so it's in total darkness.

For those of us here in the north, the Sun rises and sets farthest north along the horizon for the year -- well to the north of due east and west.

One other effect of our planet's up-and-down nodding as seen from the Sun is a change in the length of the day. In the northern hemisphere, we're seeing the longest days of the year, with the days getting longer as you head farther north. In Miami, for example, it's almost 14 hours from sunrise to sunset. But in Seattle, it's a full 16 hours. And in Anchorage, the Sun will be in the sky for more than 19 hours. In fact, it won't get fully dark at all -- twilight will tint the Alaskan sky throughout the short night.

Script by Damond Benningfield, Copyright 2010

For more skywatching tips, astronomy news, and much more, read StarDate magazine.

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