6 Enrichment: the ear at heights

• The pressure on the two sides of the eardrum is normally equal.
• When we rise quickly (in a lift, aeroplane or climbing a mountain), the outside pressure decreases, and the higher pressure inside the middle ear pushes the eardrum outward, producing a feeling of tension.
• Swallowing or chewing opens the Eustachian tube and equalises the pressure.

Why don't we feel the huge atmospheric pressure (more than 10 tonnes per square metre)? Because the pressure of the fluids inside our bodies equals the outside pressure, so the forces on the surfaces of the body are balanced.