<P> The Kármán line, or Karman line, lies at an altitude of 100 km (62 mi; 330,000 ft) above Earth's sea level and commonly represents the boundary between 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 . </P> <P> The line is named after Theodore von Kármán (1881--1963), a Hungarian American engineer and physicist, who was active primarily in aeronautics and astronautics . He was the first person to calculate that the atmosphere around this altitude becomes too thin to support aeronautical flight, since 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 to vary from 85 to 100 km, which places the line at or near the bottom of the thermosphere . </P>

Where does the atmosphere end and space begin