What is balance?

Balance is what keeps us upright, although we tend to take it for granted unless we are standing on a swaying bus or crossing a narrow bridge. But how do we know when we are upright? The answer lies in our ears in three small tubes called semi-circular canals. These canals are filled with liquid and they act very much like a spirit level. When we tip them the liquid flows to one side and bumps against special nerves which immediately send message to the brain, telling it how far we should move to regain our balance.

There are three of these canals in each ear, although they have nothing to do with our hearing. Once canal is concerned with twisting movements, one with sideways movements, and one with backward and forward movements.