Make your own Diver! | The Mary Rose
Make your own Diver!
Arts and Crafts | 13 Mar, 2020 | Museum Blogger
A fun science project for all the family!

You aren't allowed to dive on the Mary Rose wreck site, but you can still experience the fun of diving with your own Cartesian Diver!

To do this activity you will need;

First you need to make your diver. Make a 4-5 brick tall column of Lego bricks, and add some modelling clay to the bottom. This is to ensure your diver remains upright, and is able to sink to the bottom of the bottle. Add enough clay to ensure that the top of the column is just at the water’s surface, and it should be fine. Don’t worry if it sinks at first, as long as it returns to the surface it’ll be fine!

Fill the plastic bottle to the top with water, and pop in your diver. Screw on the cap really tightly, and you’re ready to go!

TOP TIP! Don’t use a bottle with a nozzle you can open to drink through – the next step will get VERY messy VERY quickly.

The top of your diver should be inside the cap of the bottle. Squeeze the bottle, and the diver will sink to the bottom. Release the sides, and the diver will return to the surface!

How does this work?

When you put the Lego bricks together, air got trapped inside them, although it is not completely air tight.

Since air is less dense than water, it is easier to squeeze, so when you squeeze the bottle, the water is forced inside the bricks, squeezing the air into a smaller area. The extra density inside the bricks makes the diver less buoyant, causing it to sink. When the pressure is released, the air expands again, forcing out the water and making it float.

This is an old scientific experiment known as the Cartesian diver, first described in 1648.