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What's Wrong With It?

Models are used to illustrate things that are a different size. Models can be used to illustrate something that is very small, very large, or difficult to observe. The Earth is an example of something that a model is used to help understand. Because the Earth is too large to observe, maps and globes are used as models. There are, however, problems involved with using maps or globes.

Look closely at the two photographs below.

Raised relief globe

Flat surface globe

 

What differences are seen when the two globes above are compared?

How is the raised relief globe a more accurate model than the flat surface globe?

Look close-up at the photograph of the raised relief globe below.

Why is this globe not a good model?

 

Possible model problems:

Each globe is an attempt to show the placement and size of continents in relationship to the entire Earth. When you look closely at the raised relief globe, you see an attempt to demonstrate differences in elevation. Mountains are shown as being raised well above the Earth's surface. While it is true that mountains are higher than the average surface of the Earth, the scale does not match the globe. At this scale, when compared with the enormous size of the entire earth, even Mt. Everest would appear flat!

Maps as models:
When you look at a map, you observe relationships between parts of the Earth. Many maps are designed to allow you to place them on a wall. These large maps are very convenient models to use when observing the entire Earth. The major problem with maps as a model is that the objects are distorted.

Remember that the Earth is really round. When you flatten it out into map form, it stretches out the poles, and these areas appear larger than they really are. In the flat map above, Greenland appears to be about the same size as North America. It is, however, actually much smaller!

The flat map above shows elevation. You see the raised bumps indicating height. The oceans have depressions that show their depths. Like the raised relief globe discussed earlier, these elevation areas are not to scale. Even on a large wall map, all mountains would appear flat compared to the entire Earth surface.

Review science safety rules here.

Get the plug-ins: Get Adobe Acrobat Reader , and Get Quicktime Player. (The Quicktime plug-in is needed to play sounds and movies correctly.)

Want to share photos of you or your friends doing this activity? Send it in an e-mail with the following information:

  1. The title of the activity
  2. The URL (Internet address)
  3. Your name.

Remember that no pictures can be used that show student faces or student names on it. 

Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE 7th grade science core.


Updated October 24, 2008 by: Glen Westbroek

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