Key Idea: The orientation of earth's axis of rotation with respect to the sun changes as the earth moves around the sun.

Students are expected to know that:

  1. The earth moves in a nearly circular path around the sun over the course of one year, approximately 365 days.
  2. The earth’s axis of rotation is tilted about 23.5° relative to a line that is perpendicular to the plane formed by earth’s circular path around the sun.
  3. As the earth moves around the sun and it rotates on its axis, its axis always points to the same place in the sky.
  4. Since the earth’s axis is tilted relative to the plane of its path around the sun and the angle at which it is tilted does not change as the earth moves around the sun over the course of a year, the orientation of the earth with respect to the sun changes gradually and continually over the year.
  5. Changes in the orientation of the earth with respect to the sun can be described by changes in the angle formed by a line between the north pole and the center of the earth and the line from the center of the sun to the center of the earth. This angle continually changes as the earth moves along its path around the sun. The angle is largest on the same day in late December each year, when the north pole is tilted away from the sun (90° + 23.5° = 113.5°) and is smallest on the same day in late June each year, when the north pole is tilted toward the sun (90° - 23.5° = 66.5°).
Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID
Number
Knowledge Being Assessed Grades
6–8
Grades
9–12
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CL097002

If the earth's axis of rotation is pointed toward the sun at one time of the year, it is pointed the same amount away from the sun six months later.

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CL144001

The angle between the earth’s axis and a line between the center of the earth and the center of the sun changes gradually every day of the year.

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CL091002

The shape of the earth's path around the sun is slightly elliptical (nearly circular).

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CL147001

On the first day of winter, the north pole is tilted 23.5° away from the sun, and each day of the rest of the winter the north pole tilts a little more toward the sun.

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CL146001

On the first day of spring, the north pole is not tilted toward the sun or away from the sun, and each day of the rest of the spring the north pole tilts a little more toward the sun.

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CL094002

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CL095001

On the first day of spring in the northern hemisphere, the north pole is not tilted toward or away from the sun.

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CL149001

The earth's axis is always tilted 23.5° from the line perpendicular to the plane of the earth's path around the sun.

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CL092002

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CL145001

The angle between the earth’s axis and the plane of the earth’s orbit around the sun does not change at all during a year.

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