Seasons

Reason for the Seasons

Because Earth's surface is curved, different parts of the Earth's surface receive different amounts of the Sun's energy.

Earth's orbit is an ellipse, or an elongated, closed curve. Because the Sun is not centered in the ellipse, the distance between the Sun and the Earth change during the year.

The tilt of Earth's rotation axis, combined with Earth's motion around the Sun causes the seasons to change.

• The hemisphere tilted toward the Sun receives more daylight hours than the hemisphere tilted away from the Sun.

• Earth's tilt cause the Sun's radiation to strike the hemisphere at different angles.

• The hemisphere tilted toward the Sun received more total sunlight than the hemisphere tilted away from the Sun.

Solstice- day when Earth's rotation axis is the most toward or away from the Sun.

• June (Winter) solstice is in June 20/21 in the southern hemisphere.

• December (Summer) solstice is December 21/22 in the southern hemisphere.

Equinox- day when Earth's rotation axis is leaning along Earth's orbit, neither toward or away from Sun.

• March (Autumn) equinox is March 20/21 in the southern hemisphere.

• September (Spring) equinox is September 22/23 in the southern hemisphere.