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Spring Equinox

March 20, 2015

Sunrise at the north pole will experience a brief interruption early today — a total solar eclipse. The Moon will pass in front of the Sun, causing a small glitch at the start of a “day” that’ll last more than six months.

Daytime is just getting started at the north pole because today is the March equinox — the beginning of spring in the northern hemisphere.

We have seasons because Earth is tilted on its axis. As Earth orbits the Sun, the poles take turns nodding toward the Sun. The south pole nods sunward in December, and the north pole in June. But neither pole tilts sunward on the equinoxes.

Because of this change in perspective, each pole sees six months of night followed by six months of daylight — or close to it. Because Earth’s orbit is slightly stretched out, there’s a slightly longer “day” for the north pole than for the south.

And that day is extended even more by the way we mark sunrise and sunset. Officially, sunrise occurs at the moment the first bit of the solar disk peeks above the horizon, with sunset coming only when the entire Sun drops below the horizon.

What’s more, Earth’s atmosphere acts as a lens, “bending” the Sun’s light. That means the Sun is in view for a while even when it’s physically below the horizon. These effects add extra hours to the long Arctic day.

According to the U.S. Naval Observatory, the Sun rose at the north pole on Wednesday afternoon, and won’t set until September 25th — more than six months later.


Script by Damond Benningfield, Copyright 2015

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