The earth’s revolution refers to the movement of the earth around the sun. It takes the earth about 365¼ days to make one complete trip around the sun. This movement of the earth is what creates the seasons and our year.
Photo: The earth’s revolution around the sun (source: NASA).
Earth’s Revolution – the Year
Our concept of the year is based on the earth’s revolution around the sun. One actual solar year is 365¼ days. A calendar year is 365 days. Every four years we have a leap year. A leap year is 366 days long. February gets an extra day (29 days instead of the usual 28 days). This extra day is an adjustment for the extra ¼ of a day in the solar year.
The earth’s axis is not straight up and down. The earth has a tilt of 23½ degrees. This tilt is called the earth’s inclination.
Combined with the earth’s revolution this produces seasons on the earth.
As the earth travels around the sun, sometimes the North Pole is tilted toward the sun. When this happens, the Northern hemisphere experiences summer. The Northern hemisphere receives the most sunlight (longer days and stronger sunlight).
At other times, when the North Pole is tilted away from the sun, the Northern hemisphere experiences winter. The Northern hemisphere now receives the least sunlight (shorter days and weaker sunlight).
The seasons are reversed in the Southern hemisphere.
Improving Your Reading and Thinking Skills
Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.
How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.