Kármán line

Etymology
, who calculated this limit.

Noun

 * 1)  The altitude at which the atmosphere becomes too thin to support aerodynamic flight.

Usage notes

 * This is treated as the border between the Earth's atmosphere and outer space. It is defined as a static altitude of 100km (62 mi) above sea level (ASL) on Earth by the Fédération Aéronautique Internationale; the U.S. government (NASA, USAF, FAA) treats this as a static altitude of 50 mi (80km) ASL. The actual altitude is dynamic and not static, and depends on atmospheric conditions. Where both the 100km and 80km limits are used at the same time, the 100km limit is the Karman line and the 80km line is the McDowell line.