Spinning Earth

Spinning Earth And Ocean Marble

Can you keep your ocean-marble on the spinning cardboard-earth for three whole rotations!? A fun way to model the spinning earth and learn about how spin effects weather.

Suitable for kids aged 6+ with parental supervision.

Young children will need an adult to help make the model earth, it requires cutting thick cardboard and measuring. No assistance should be needed for the actual spinning of the cardboard earth.

You Need:
  • Large piece of thick cardboard
  • Push pin
  • String
  • Blutak
  • Scissors
  • Pencil
  • 60cm ruler
  • Foil
  • Marble
What to do:
  1. First you need to make your model cardboard earth by cutting a 40cm diameter (approx.) circle from the thick piece of cardboard.
  2. An easy way to draw a circle of this size is to tie one end of a 20cm length of string to a pencil, and fasten the other end to the cardboard with a push pin. Then, with the string taught, draw your perfect circle by moving the pencil all the way around the push pin. Using your scissors, cut along the pencil line so you are left with a large cardboard disc.
  3. If you havent already, push a push pin into the centre of the cardboard disc. The pointy end of the push pin should come all the way through and out the other side of the cardboard.
  4. Use a blob of blutak to cover the sharp end of the push pin, and then add a small piece of scrunched foil to ensure there are no accidental pin pricks.
  5. Now for the fun! Place the cardboard disc flat on a table or other smooth surface. The metal, flat part of the push pin should be facing down on the surface (the pointy, blutak/foil end up). Then spin.
  6. How fast, or slow, can you spin your model earth? When you have your earth spinning drop the marble onto the disc (near the centre), how long does the model marble ocean stay on the earth before it flies off? Adjust the speed of the spin to keep the marble on for the longest time. Can you keep your marble ocean on the model earth for three whole rotations?

Why is it so?

The earth is spinning. Day and night is caused by the earth spinning on its axis, alternately facing, and then turning its back, on the sun. It takes 24 hours for the earth to make one whole rotation. Not only is it spinning on its axis, it is also moving (or orbiting) around the sun hence the four seasons. The earth is spinning at a pretty good speed for us. If it were spinning too quickly, centrifugal forces would push the oceans right off the surface of the earth. Just like if you spin your model cardboard earth too quickly, the marble ocean flies off. Luckily, gravity is holding everything in place, including the oceans. If you spin your cardboard earth too slowly, again the marble ocean will come off. The challenge is to get your cardboard earth to spin at just the right speed so the marble stays put for thee rotations. The earths spin also effects the weather: wind conditions and directions, ocean currents, and rainfall.