Exhibit: Slow Bubbles

Pump air into the cylinder and watch the bubbles rise.  Bubbles rise through the oil at different speeds.  Whenever they meet, the smaller one always ‘eats’ the larger one!  Bubbles rise because the pressure underneath them is greater than the pressure above.  This buoyancy is much greater than the weight of the air in the bubble, so they rise.  The silicone oil in this exhibit is chosen to offer a lot of drag so the large bubbles travel slowly and smoothly.  If you blow a big bubble after a smaller one, the larger one will catch up, squeeze it into a bell shape and then move inside.