We are officially in Autumn. A time when the leaves change colors, the air cools, and we can bring out the warmer clothing. Changing from one season to another is a very interesting topic and mainly comprises of two big factors. The first being the sun and its distance away from the earth (~93 million miles), and the second is the orientation of the Earth.

Weather is truly driven by the uneven heating of the Earth, where the north and south poles are extremely cold, where as the equatorial regions are quite warm. In the mid-latitudes, where we live in the United States, these different air masses collide and create very interesting weather phenomenon. But the true testament to the varying seasons comes by the fact that the Earth is not sitting straight up.

The Earth does not sit up and down, its actually tilted. Along the axis, the Earth is tilted by 23.5°. An interesting number, does that remind you of some specific locations? The Tropic of Cancer and the Tropic of Capricorn happen to lie 23.5° north and south of the equator, latitudinal. Click here to take a look at the “tilted” Earth.

Due to this tilt, there are seasonal differences. If we did not have this “oddity” then the weather would most likely be the same year round.

Now, when it comes to the changing of seasons and when they officially begin, it all depends where the sun’s rays are focused. Summer begins when the suns rays are focused on the Tropic of Cancer, which is 23.5° north of the equator. Since the sun is warming up the northern hemisphere more than the southern hemisphere at that time, we are enjoying warmth, while the folks way down south are beginning their wintry phase. During the summer, the suns rays gradually zero in on the equator, where at that time Autumn would begin. Farther into the year, once the sun’s beams travel to the Tropic of Capricorn (23.5° south of the equator), winter starts up for us. Finally, Spring begins as the rays focus again on the equator. For a visual of this yearly cycle, you can click here.

Overall, it’s all because of two big factors, the suns energy and the fact that the Earth is a bit “tilted.” This is what makes the weather so fascinating and ever-changing.

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