Astronomers, like other scientists, often use inference to help explain observations. If the path of a moving object changes, it can be inferred that a force has acted upon the object. In terms of stars and galaxies, that force is gravity. In this activity, you'll make inferences concerning hidden magnets based upon the way their magnetic force field influences a moving steel bearing.
Several small magnets
1. Work in teams of two. Use scissors to cut a rectangle of graph paper that fits within the inner lid of a shoebox.
2. Press out the paper, making sure that it is smooth. Secure it in place with tape.
3. One team member then places magnets on the upper surface of the shoebox lid. Position the magnets randomly and secure with tape. Don’t let the other team member see where you place these "unseen forces."
4. Next, turn the lid over so the positions of the magnets cannot be seen. Prop the lid against a thick textbook, producing a gentle slope.
5. The team member who didn't place the magnets is challenged to uncover their positions. The strategy involves letting a steel ball-bearing roll down the slope of the lid. Any changes in the path of the bearing are used to make inferences about the location of the magnets.
6. As evidence is collected, the team member marks their assumed positions on the graph paper. When the activity is finished, turn the lid over and verify the positions.
7. Once completed, team members exchange roles and repeat the activity.