Thermal Lift

“Lift”, rising air. It is an exercise in relativity: a sailplane typically sinks 200 feet per minute (about 2 mph) through the air that surrounds it. If that air is moving upwards faster than 2 mph, the glider rises relative to the ground. In the early 1920s, glider pioneers were doubtful that consistent large upward currents of 2 mph could reliably develop in the atmosphere and be exploited by pilots. Perhaps soaring was only for the birds, slow and maneuverable as they were. Once they tried, they soon found out that useful lift is quite common and it is a rare day that a glider cannot do at least a little soaring.