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Module 4: How the Students See It

D. Classification Skills

In the planetarium we classify all sorts of things:

stars, planets, nebulae, star clusters, galaxies, and subclasses of these objects.

How do students perceive our descriptions of the way these objects are classified?

Egocentric example:

Distinguish an asteroid or small moon from a planet by virtue of its roundness or lack thereof.

Concrete level example:

Earth is in the solar system and in the galaxy at the same time.

Formal level example:

A high school senior might well be able to understand how astronomers classify galaxies, nebulae, and clusters, and then subclassify these into various types (e.g. open or globular clusters)

The different levels of classification reasoning are demonstrated in the solutions to the following problem.

Students of various ages were given 6 pictures of galaxies and

asked to classify them any way they wished.

For each student response, what is the reasoning level that the student is using.

1. “Basically, there are two kinds of galaxies; spirals and non-spirals.

The spirals might be seen face-on or sideways, and the non-spirals might be either elliptical or irregular in shape.”

2. “The pictures in the bottom row are all spirals and the pictures in the top row are not spirals.

Also, the ones here (on left) are skinny, the middle ones are egg shaped, and the ones here (on right) are rounded.”

3. “In order from nicely shaped galaxies towards more squiggly galaxies.”

4. Regarding these galaxy groupings:

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