earth, in geology and astronomy: The Change in Seasons

The change in seasons is caused by the tilt of the earth's axis to the plane of its orbit, making an angle of c.66.5°. When the northern end of the earth's axis is tilted toward the sun, the most direct rays of sunlight fall in the Northern Hemisphere. This causes its summer season. At the same time the Southern Hemisphere experiences winter since it is then receiving indirect rays. Halfway between, in spring and in autumn, there is a time (see equinox) when all parts of the earth have equal day and night. When the northern end of the earth's axis is tilted away from the sun, the least direct sunlight falls on the Northern Hemisphere. This causes its winter season.

Sections in this article:

• Introduction
• The Origin of the Earth
• The Change in Seasons
• Rotation and Revolution
• The Astronomical Earth
• The Earth's Core
• The Earth's Mantle
• The Earth's Crust and the Moho
• The Geologic Earth
• Bibliography

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