Activity from Nadia Paes and Kate Sloyan (November 2002) at:
http://www.eso.org/outreach/eduoff/catchastar/cas-projects/uk_nt7_1/

Objective: The following group activity involves three short experiments that help to demonstrate how low the probability of an asteroid collision with Earth actually is.

Materials:

1. Steel ball bearing
2. 2 large magnets
3. Sandpaper
4. A meter rule
5. A flat even surface