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Comets and asteroids
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Reality 1:

Comets are part of the solar system. Scientists believe they come from one of two locations within the solar system: the Kuiper belt and the Oort cloud. The comets that we see often every 100 years come from the Kuiper belt, and comets that we see rarely every few thousand years come from the Oort cloud.


Reality 2:

Although comets and asteroids are both tiny bodies that orbit in the solar system, their composition is different. Asteroids are mostly rock with some ice, while comets are mostly ice with some rock.


Reality 3:

Comets do not always have tails. They develop a fuzzy, shell-like cloud called a coma, and one, two, or three tails when near the Sun. Comets have no coma or tail when far away from the Sun.


"Myths vs. realities: Comets" contains common misconceptions about comets. The misconception is presented as the “myth” and an explanation of the true concept is the “reality.” Teachers should be aware of the misconceptions students harbor because they impede students' ability to see the “big picture” in the various sciences; hamper students' ability to apply science principles meaningfully to everyday life; and diminish students' ability to appreciate the links among science concepts and generalizations.

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How to use in the classroom

This resource aids teachers in identifying and remedying student misconceptions about comets. The best way to learn how students think is to ask them. Below are two strategies that can be employed to identify your students' misconceptions concerning comets. The first is an individual writing activity that allows students to think independently. The other is a group activity that allows students to share their ideas verbally.

An individual writing activity. To prepare for a study of comets, explain that you are interested in finding out what your students already know about this topic before you start. Ask students to write down what they know about comets and why they know it. For example, they may say comets are not part of the solar system because they travel beyond the orbit of the outer planets. Collect their papers and compile a list of misconceptions the students display in their writing.

The next day, start your unit by explaining that it is common for people both children and adults to have misconceptions about their world. Explain that you have a list of misconceptions that you would like to discuss with the class. You can read the misconceptions that appear on Myths vs. realities as well as the ones compiled from the students' papers. Ask the students to comment on the misconceptions and discuss the reality of the situation. If your students have misconceptions about comets that we haven't included on our list, you can send them to us through the Contact us section of this Web site, and we'll add them to our list. You may want to make special mention of any new misconceptions the students revealed, and let them know you'll submit them to us for addition to our list.

A group activity. Begin your study of comets by explaining to students that sometimes the ideas they have about this topic may not be entirely true, and that you are going to try to identify these ideas. Explain that some of these ideas are very hard to remove, and that even their parents may have some of these misconceptions Tell the students that you will read a statement (either a myth or a reality) and they must decide whether it is true or false. Ask them to explain their decision in writing.

Once students have written their responses, discuss their thoughts and the accuracy of the statement. Be sure to establish some ground rules concerning student responses to the thoughts of their peers. Remind them that almost anyone can hold these misconceptions, but they need to be identified and removed before true learning can begin. Ask students if they have any other misconceptions that are not covered in the activity, so you can submit them to us for addition to our list through the Contact us section of this Web site. It might help students feel more invested in the activity.

Related materials

Amazing Space resources by topic: Comets and asteroids