How to Make a Cartesian Diver
Many people start learning about the fun of fluid dynamics and pressure changes with simple experiments, such as the cartesian diver. You can experience these experiments, or share the experience, by reproducing them with a few simple steps and simple items.
Instructions
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1
Fill the bottle almost completely with water. Keep the lid off, as you may have to retrieve the dropper. While you're at it, you might want to fill a bowl or sink with water deep enough for the dropper.
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2
Submerge the dropper, then let a small amount of it surface and squeeze the top of the bulb so that there's only a small bubble of air in the top. Float the dropper in the bottle or sink. If it doesn't float, let it have more air. If it floats too well, it might have too much air. Make sure that it's barely buoyant.
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3
Place the dropper into the bottle, making sure to fill the bottle as completely as possible before you seal it with the dropper inside.
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4
Make the diver fall by squeezing the bottle, forcing the air inside to compress by increasing the pressure in the bottle and the volume of water inside of the dropper.
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Tips & Warnings
You can make a cartesian diver out of anything that will hold a small amount of air inside of a tip. Pen lids weighted at the open end work well, as do test tubes (also weighted) and a variety of common objects. You shouldn't be afraid to experiment.
