What is the Kármán line?
The Kármán line is an imaginary boundary 100 kilometers above sea level, widely used as the edge of space. It is named after Hungarian-American engineer Theodore von Kármán.
Theodore von Kármán studied how high an aircraft could fly. As altitude increases, the air becomes so thin that a plane would need to fly extremely fast to generate enough lift. Von Kármán calculated that at around 80 to 100 kilometers, that speed would be close to orbital speed, meaning a vehicle would be in orbit rather than flying like a plane.
In the 1960s, the Fédération Aéronautique Internationale adopted 100 kilometers as a convenient, round number for the boundary of space. It is used to define who has flown to space in international records and in many legal discussions.
A debated line
Some scientists argue that the real boundary is closer to 80 kilometers, because satellites can briefly dip that low without immediately falling. The United States has generally used 50 miles, about 80 kilometers, to award astronaut status. The debate gained attention as private companies began suborbital space tourism.
Did You Know?
Theodore von Kármán also co-founded NASA's Jet Propulsion Laboratory in California.