GED Science: Seasons

The tilt of the earth on its axis, and the position of the earth relative to the sun help explain the seasons we experience on earth.  The earth is tilted on it’s axis 23.5 degrees.  This tilt means that the northern and southern hemispheres on earth experience different seasons at a particular time.  The hemisphere that is tilted more directly toward the sun will experience summer, and the hemisphere that is tilted away from the sun will experience winter.  In the diagram below, the southern hemisphere would be experiencing summer (sun rays are more direct), while the northern hemisphere would be experiencing winter.


The tilt of the earth remains constant.  However, as the earth revolves around the sun in a counterclockwise direction, the portion of the earth that is tilted toward the sun changes. You can see this phenomenon in the diagram below showing seasons labeled for the northern hemisphere:


The diagram above shows key positions of the earth and the sun.  These positions are called solstices, and equinoxes.  Solstices occur in the summer or winter, and reflect the day when the sun appears directly overhead at specific earth latitudes called the Tropic of Cancer or the Tropic of Capricorn.  Equinoxes occur in the fall or spring, and reflect the day when the sun appears directly overhead at the equator.  The diagram below shows the solstices and equinoxes, labeled for the northern hemisphere:


It is a misconception that seasons are caused by the distance of the earth from the sun; that at longer distances, we experience winter, while at shorter distances, we experience summer.  The seasons are the direct result of the angle at which the sunlight hits the earth with different positions of the sun and the earth relative to each other.  How directly the sunlight hits the earth determines the temperatures we experience, as well as the length of the day that we experience.


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