11. Non-Stop Top with Built-in Light Show
$14.99 at amazon.com
This battery-powered top has a motor with an eccentric weight inside that keeps it spinning until the battery runs out. Matt Moses, who just earned his Ph.D. in mechanical engineering at Johns Hopkins, asks these questions when showing it to students:
- "Would the top work if you spun it on a frictionless surface?
- "Suppose you were in orbit inside the International Space Station. If you spun it in midair, would it still work?
- "If the weight inside were not eccentric—that is, if it were perfectly balanced on the motor—would the top still work?
- "Does the weight spin in the same direction the top is spinning in or in the opposite direction?”
12. Giant Microbes
From $8.95 at giantmicrobes.com
These fuzzy replicas of human cells, viruses and bacteria include the common cold (rhinovirus), neurons, and red and white blood cells. “The large size and kid-friendly plush help students visualize microscopic structures,” says Emory’s Shepard.