Making Maths: Planet Paths

Challenge Level: Challenge Level:1

We know that the planets move around the sun in elliptical paths. BUT, when viewed from Earth over a long period of time, the movement of each planet traces out a path that is much more interesting! This happens because the place we are looking from (the Earth) is also moving. Earth not only orbits the sun, but also spins around its own axis.

Planets


Do these shapes look familiar? If you've ever used a Spirograph you'll notice that these sorts of looping designs can be made by spinning a small circle around the inside of a larger circle.

So, dig out that Spirograph from the back of the cupboard and see if you can draw the planet paths.

If you can't get hold of one, try making your own. All you need is a small plastic lid and a large plastic lid. It's best if the small lid is made from soft plastic so it's easier to poke holes in it. Put a rubber band around the small lid to help it grip onto the inside of the big lid - otherwise it just slips (and will make you cross).

Lids


Cut a circle of paper to fit inside the big lid. Ask an adult to poke a few holes in the small lid so that a pen tip will just reach through to trace a line on the paper. (Take care!)

Now carefully move the small lid around inside the big lid, letting it spin as it goes. Keep going around and around until you return to the start of your line.