# PRISMS: Phenomena & Representation for Instruction of Science in Middle School

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This is a representation reviewed for the following learning goal:

The rotation of the Earth on its axis every 24 hours accounts for the night-and-day cycle. To people on Earth, this turning of the planet makes it seem as though the sun, moon, planets, and stars are orbiting the Earth once a day.

## Summary

This interactive, animated photograph of the Earth spinning on its axis during one of the equinoxes shows the day/night line. The animation can be stopped, forwarded, reversed, or tilted so one can see the Earth from above the North or South Pole. It addresses the part of the key idea about the rotation of the Earth on its axis every 24 hours accounting for the night-and-day cycle. The animation is likely to be comprehensible to middle school students.

Limitations:
The resource does not depict the sun, moon or stars or show the motion of the Earth with respect to these bodies.

Suggestions to improve effectiveness:
The user may wish to connect the rotation and the 24-hour day-night cycle. Discussions based on observations of the apparent motions of the sun and stars throughout the day/night may help.

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## Detailed Review

### Description

The representation is an animation of the Earth spinning on its axis on one of the equinoxes. The photograph shows the day/night line. The rotational motion of the Earth is sped up to show a 24 hour rotation in only seconds. The animation can be stopped and forwarded or reversed just one small step at a time. There is also a lever so one can tilt the Earth to see a view from above the north pole or tilt it so the view is from above the south pole.

• Resource Copyright Owner: McDougal Littell
• Type of Resource: application/x-shockwave-flash

## Content alignment

The resource does not specifically address the actual substance of the learning goal but could be used to specifically address it.

### Explanation

The resource shows that the rotation of Earth on its axis every 24 hours accounts for the night-and-day cycle. Questions within the accompanying text imply that this rotation accounts for the day-and-night cycle. This resources does not address apparent motion of the sun, moon, planets, and stars as seen from Earth.

## Scope

The resource addresses the indicated part of the learning goal:

### Explanation

[The rotation of the Earth on its axis every 24 hours accounts for the night-and-day cycle.] To people on Earth, this turning of the planet makes it seem as though the sun, moon, planets, and stars are orbiting the Earth once a day.

## Sophistication

The resource correctly reflects the level of sophistication of the learning goal.

### Explanation

The resource generally reflects the correct level of sophistication for middle school students. The term "equinox" does not need to be emphasized for this learning goal.

## Notes for Teachers

The resource does not necessarily direct students toward the key idea, but this can be addressed through discussion of what the representation depicts is happening during a 24 hour cycle. The user may wish to have students identify where and when selected points on the Earth experience daytime and nighttime.

## Quality of instructional support

Does the representation accurately represent relevant aspects of the learning goal and/or brings out limitations that are not accurate?

Yes—The representation accurately represents relevant aspects of the learning goal and brings out inaccuracies, if there are any.

The representation correctly shows the Earth turning, and supporting text describes that one rotation takes 24 hours to complete.

Is the representation likely to be comprehensible to students?

Yes—The representation is likely to make the learning goal comprehensible to students.

The position of the sun is not specifically stated in the resource, but it is instead assumed that students will know where the sun is located based on which portion of the Earth that is lit. The animation contains no reference to passing time, so that students may not connect the rotation to the length of the 24-hour day that is noted in the text.

Does the representation make clear which aspects of the real thing are represented and which are not?

No—The representation does not make clear which aspects of the real thing are represented and which are not.

The representation does not indicate that the purple axis is actually invisible. The representation also does not depict the sun, moon or stars or show the motion of the Earth with respect to these bodies.

Useful

## Notes to teachers

Have students make their own observations of the apparent motions of the sun and stars throughout the day/night and use this resource to discuss why they think these objects appear to orbit the Earth. This resource should be used in conjunction with other resources that show the apparent motion of the sun, stars, etc. through Earth's sky.

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