Parallelism of the Earth's Axis

Notice how the earth's axis is always pointing in the same stellar direction (that is, toward the same star).  In short, the axis is always parallel to itself.  This phenomena accounts for the change seasons because the intensity and duration (that is, the amount) of solar radiation received on any part of the earth's surface varies throughout the year.

[Please note that it has nothing to do with the fact that one hemispehere is closer to the sun in the summer than in the winter.]

The earth's north pole points at Polaris or the North Star. Click here to learn how to find Polaris in the night sky.

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