A scuba diver in a bottle! A fun experiment to set up and investigate density, diving and more.
Explore the science of Cartesian divers and density while having fun with this cool toy you can make. This experiment is named after Rene Descartes (1596-1650), a French scientist and mathematician who used the diver to demonstrate gas laws and buoyancy.
Squeezing the bottle causes the diver to sink because the increased pressure forces water up into the straw compressing the air inside. This reduced volume decreases the density, of the diver causing it to sink. Releasing the squeeze allows the water to come back out and the diver floats back to the top.
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Real world STEM application:
How do fish float and sink in water?
They have a small air bubble pocket inside their bodies. When they squeeze the bubble with their muscles, it makes the it smaller. The fish becomes more dense, and it sinks. When the fish relax the muscle, the air bubble gets bigger, the fish becomes less dense and he floats upward.
This is the same idea used to raise and lower a submarine. Water is pumped into tanks inside the submarine to make it sink. Water is pumped out of the tanks to make it rise.