Where is the Kármán line?
The Kármán line sits 100 km above sea level and is the most widely used boundary of space. NASA and the US Air Force use 80 km instead, so there is no single agreed answer.
The atmosphere does not stop anywhere. It thins gradually and keeps thinning for hundreds of kilometres, so any boundary is a decision rather than a discovery.
The 100 km figure is named after Theodore von Kármán, who estimated roughly the height at which an aircraft would need to fly so fast to generate lift that it might as well be in orbit. The Fédération Aéronautique Internationale adopted the round number.
The United States awards astronaut wings above 50 miles, about 80 km, and some researchers argue that is the better physical boundary.
See it happen
Space & OrbitsFalling foreverSource: Kármán line