concept

Boyle's law

For a fixed amount of gas at constant temperature, volume is inversely proportional to pressure: double the squeeze and you halve the gas. It sounds dry, but it is exactly what happens inside a diver's chest. A 6-litre lung filled at the surface, taken to 30 metres on Earth — near four atmospheres — is down to about 1.5 litres, which is precisely the residual volume the chest cannot fold below. Deeper than that, the gas wants to be smaller than the ribcage geometrically allows, and something else must fill the gap or the pulmonary vessels tear.