Key Idea: Changes in the orientation of earth’s axis with respect to the sun over a year causes the length of daytime to be longer in the northern hemisphere when the north pole is tilted toward the sun and longer in the southern hemisphere when the south pole is tilted toward the sun.

Students are expected to know that:

  1. As the earth rotates on its axis, every place on the earth spends some part of the day in sunlight and some part of the day in darkness.
  2. The more time a place on the earth is in sunlight, the more daytime (and less nighttime) that place will have.

Late June:

  1. Because the northern hemisphere is tilted 23.5° toward the sun and the southern hemisphere is tilted 23.5 degrees away from the sun in late June, more of the northern hemisphere is in sunlight than is the southern hemisphere in late June.
  2. In late June, the farther north a place is from the equator, the more time it will be in sunlight and the more hours of daytime it will have. The farther south a place is from the equator, the less time it will be in sunlight and the fewer hours of daytime it will have. Places on the equator spend half of the day in sunlight and half of the day in darkness and therefore experience 12 hours of daytime and 12 hours of nighttime.

Late March and late September:

  1. In late March and late September, the sun is directly over the equator, so half of the northern hemisphere and half of the southern hemisphere are in sunlight at any given time. This means that every place on earth experiences 12 hours of daytime and 12 hours of nighttime.

Late December:

  1. Because the southern hemisphere is tilted 23.5° toward the sun, and the northern hemisphere is tilted 23.5 degrees away from the sun in late December, more of the southern Hemisphere is in sunlight than is the northern hemisphere in late December.
  2. In late December, the farther south a place is from the equator, the more time it will be in sunlight and the more hours of daytime it will have. The farther north a place is from the equator, the less time it will be in sunlight and the fewer hours of daytime it will have. Places on the equator spend half of the day in sunlight and half of the day in darkness and, therefore, experience 12 hours of daytime and 12 hours of nighttime.
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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CL110002

Of three places in the northern hemisphere that are at the same latitude but different longitudes, when the north pole is pointed toward the sun all three places receive the same number of hours of daylight.

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CL135002

On a day when the north pole is not tilted toward or away from the sun, all places receive the same number of hours of daylight but not the same intensity of sunlight over the course of the day.

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CL111002

Of two places in the northern hemisphere at the same longitude and different latitudes, the place that is the farthest north will have a longer daytime in May but not in February.

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CL112002

During a day in August, of the north pole, the south pole, and the equator, the north pole has the greatest number of hours of daylight.

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CL148001

For two places at different latitudes and different longitudes, the place that is farther north of the equator has more hours of daylight in July.

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CL109002

Of three places in the northern hemisphere that are at the same longitude but different latitudes, when the north pole is pointed toward the sun the place closest to the north pole receives the greatest number of hours of daylight.

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CL113002

During a day when the earth’s axis is not tilted at all toward or away from the sun, all places on earth would have an equal number of hours of daylight on that day.

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CL136002

All places on earth have the same number of hours of daylight on September 21, but not on June 21 or August 21.

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