Ask Todd: Sun movement during season changes

10:50 PM, Sep 6, 2012   |    comments
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Tonya asks: "Why does the sun seem to move when the seasons are getting ready to change? I live at the foot of Clinch Mountain and the sun has started coming down the mountain instead of coming up over the whole valley."

The sun seems to move across the sky because the Earth is rotating, but it's actually the Earth's tilt on its axis which causes the seasons to change.

During summer, the northern hemisphere is tilted toward the sun, with the highest sun angle centered over the Tropic of Cancer at 23 1/2 degrees north latitude. The sun focuses on and warms the northern hemisphere.

In fall, neither hemisphere is tilted toward the sun, and as a result, neither hemisphere has extreme heat or cold. The sunlight focuses on the equator.

During winter, the northern hemisphere is tilted away from the sun. Sunlight focuses on and warms the southern hemisphere.

And during spring, neither hemisphere is tilted toward the sun. Just like in fall, both hemispheres usually do not have extreme heat or cold.

If it weren't for the Earth's tilt, we wouldn't have seasons at all.

If the Earth were not tilted, the same amount of sun would fall on all parts of the Earth each day of the year.

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