Environment and Ecology

The Earth’s Environment

Why does the Earth have seasons?

Although many people believe that the Earth has seasons depending on our planet’s distance from the Sun, that is not the case. The Earth’s four seasons are due to one main factor: the Earth’s inclination on its axis (23.5°) in relation to the plane of the Sun. For example, when the geographic North Pole is tilted toward the Sun, it is summer in the Northern Hemisphere and winter in the Southern Hemisphere; when the direct rays of the Sun are overhead at the Equator, and day and night are of equal length in the Northern and Southern Hemispheres, it is called the equinox—both of which occur in the respective spring (vernal equinox) and fall (autumnal equinox) of both hemispheres. And finally, when the geographic North Pole is pointed away from the Sun (at the 23.5° angle), it is winter in the Northern Hemisphere and summer in the Southern Hemisphere.


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