Kármán line

The Kármán line, or Karman line, lies at an altitude of 100 kilometres (62 mi; 330,000 ft) above the Earth's sea level, and commonly represents the boundary between the Earth's atmosphere and outer space. This definition is accepted by the Fédération Aéronautique Internationale (FAI), which is an international standard-setting and record-keeping body for aeronautics and astronautics.

The line is named after Theodore von Kármán (1881–1963), a Hungarian-American engineer and physicist. He was active primarily in aeronautics and astronautics. He was the first to calculate that around this altitude, the atmosphere becomes too thin to support aeronautical flight, because a vehicle at this altitude would have to travel faster than orbital velocity to derive sufficient aerodynamic lift to support itself. The line is approximately at the turbopause, above which atmospheric gasses are not well-mixed. The mesopause atmospheric temperature minimum has been measured variously at 85 km or 100 km, which puts the line at or near the bottom of the thermosphere.

In the final chapter of his autobiography Kármán addresses the issue of the edge of outer space:

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