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Summer Solstice

StarDate: 
June 20, 2016

The Sun is at a standstill right now. Oh, it’s still orbiting the center of the galaxy at an impressive clip — about half a million miles per hour. And it’s still moving across the sky as Earth turns on its axis. But the points along the horizon at which the Sun rises and sets aren’t changing.

The reason is that today is the summer solstice. It’s a point in Earth’s orbit that marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere.

We have seasons because Earth is tilted on its axis. At the June solstice, the north pole tilts toward the Sun, bringing more sunlight to the northern hemisphere. Six months later, at the December solstice, the south pole tilts sunward, giving the northern half of the globe shorter days and longer nights.

Between the solstices, the Sun moves north and south in the sky. As a result, its rising and setting points move north and south as well. At some times of year, if you have a good way to mark these points, you can see the difference from day to day.

But the Sun appears to “stand still” along the horizon for a few days either side of the solstice. In fact, solstice means “Sun stands still.” At the June solstice, the Sun is farthest north for the year, so it rises and sets to the north of due west. Just how far north depends on your latitude.

Incidentally, the summer solstice is also the longest day of the year, so there’s plenty of sunlight as we head into summer.

Script by Damond Benningfield

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