Optimist, Pessimist, Chemist!

There is a well know saying about people believing a glass is half full (optimist, look on the bright side) or half empty (pessimist). Chemist is a similar word to optimist and pessimist, so it is funny to compare a chemist's opinion. The chemist defines the water as half and includes the percents of the major gasses found in the air, which is assumed to be a homogenous (evenly distributed particles) mixture, with double the pictured percents in the atmosphere.