How can I teach orbits and gravity using asteroids?

Question

Accepted Answer

Asteroids show how gravity shapes paths around the Sun, how resonances with Jupiter deliver meteorites, and how gravity assists and deflection work.

Asteroids and meteorites provide real examples for teaching about gravity and orbits.

Basic orbits. Explain that asteroids orbit the Sun because the Sun's gravity pulls them inwards while their motion carries them sideways. A string-and-ball demonstration, swinging a soft ball on a string in a circle, shows the need for an inward force; if the string is let go, the ball flies off in a straight line. Use this carefully in open space.

Elliptical orbits. Use two drawing pins and a loop of string to draw ellipses. Show that asteroids and comets often have more stretched orbits than planets, which is why some cross Earth's path.

Kepler's laws. For older pupils, explore how objects move faster when closer to the Sun. Compare the orbital periods of Earth, Mars, asteroids and Jupiter.

Resonances. Explain that where an asteroid's orbital period is a simple fraction of Jupiter's, such as one third, regular tugs from Jupiter build up and stretch its orbit. This is how many asteroid fragments are pushed into Earth-crossing paths and become meteorites. A swing analogy helps: small pushes at the right moment build up a large motion.

Fireball orbits. Show orbits calculated from camera networks for meteorite falls. Most trace back to the asteroid belt, the evidence that meteorites come from asteroids.

Deflection. Discuss how DART changed an asteroid moon's orbital period by about 32 minutes, and why a small push applied years in advance can make a big difference.

How can I teach orbits and gravity using asteroids?

More about for teachers