Long Summer
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If this summer felt like it dragged on longer than three months, it did. In fact, every summer pulls the same trick. Hi, I'm Dave Thurlow from the Mount Washington Observatory and this is The Weather Notebook. In the Northern Hemisphere, summer is always the longest season of the year. It lasts about 93 and 1/2 days. Winter, believe it or not, only lasts 89 days. Autumn and spring fall in between. How can this be?

It took several thousand years to solve the mystery. As far back as 2000 B.C., people measured the passing seasons at places like Stonehenge, so they must have realized that seasons weren't all the same length. The fact that ancient astronomers thought the earth was the center of the universe, kept them from understanding why.

Then in 1500, Nicolas Copernicus observed that all the planets, including Earth, revolved around the sun. This caused quite a theological stir, but it still didn't solve the puzzle. A few years later, another brilliant scientist, Johannes Kepler, finally solved the puzzle of the seasons.

Kepler discovered that the earth's orbit around the sun isn't a perfect circle. Instead, it's slightly egg-shaped, with the sun a bit off center. Because of this, the earth swings through its orbit faster when it's closer to the sun. The closest approach happens--ironically--in January. This closer proximity doesn't warm things up but it does help winter to pass a little bit quicker than spring and summer in the Northern Hemisphere. So wherever you are, if your not a fan of winter, at least it's shorter than summer.

Today's contributing writer is Bob Henson. Please visit weathernotebook.org for more. Thanks to Subaru and the National Science Foundation.