Читать книгу Deeper into the Darkness онлайн

49 страница из 184

Once a diver has descended to a depth of 10 metres, the weight of the surrounding water in which they are immersed is conveniently exactly equal to the weight of the whole atmosphere that presses down upon us whilst we are standing on land at sea level. On the surface, the weight of the atmosphere (atmospheric pressure) is called one atmosphere or one bar. So, adding the 1 atmosphere weight of the atmosphere itself to the 1 atmosphere weight of water at 10 metres produces a pressure (water pressure) of 2 bar (or 2 atmospheres): at 10 metres, the water pressure is exactly double the air pressure we experience on the surface. The doubled weight of water and atmosphere above the diver will compress the volume of any air spaces such as lungs to half its normal size if an aqualung is not used.

To combat this ‘squeeze’ as the old hard-hat divers called it, at a depth of 10 metres a diver’s aqualung feeds them air at twice atmospheric pressure, that is at 2 bar. The delicate equilibrium between the air pressure in the lungs and the surrounding water pressure is maintained.