The Kármán line is a limit 62 miles (100 kilometers) above average sea level that borders the Earth's atmosphere and the beginning of space. However, defining exactly where space begins can be quite complicated and depends on who you ask. This is because the Earth's atmosphere does not abruptly end, but rather becomes increasingly thin at higher altitude, meaning that there is no definitive upper limit. There is no easy distinction between “space” and “not space”, partly because the Earth's atmosphere doesn't just fade away, but it gradually gets thinner and thinner over about 600 miles.
However, despite now having his name associated with the limit of space, von Kármán himself never really published this idea. The Air Force, NOAA and NASA generally use 50 miles (80 kilometers) as a limit, and the Air Force gives astronaut wings to flyers who exceed this mark. The government has been reluctant to accept a specific height; people who fly above an altitude of 60 miles (100 km) usually get astronaut wings from the Federal Aviation Administration. In his new study, McDowell thoroughly analyzed data describing the orbital paths of some 43,000 satellites, which he collected from the North American Aerospace Defense Command (NORAD), which monitors aerospace space in the United States and Canada.
Kármán made the necessary calculations and then rounded up the answer to that memorable figure of 100 kilometers (62 miles). In addition to the space limit line, the name von Kármán is associated with a series of engineering equations, laws, constants and aerospace designs, as well as with some awards in this field. In fact, if the Air Force specified the Kármán line as the defining limit of space, it would strip the wings of astronauts from some of the first pioneering test pilots. Traveling beyond the confines of the Earth's atmosphere would take you about 6,000 miles (10,000 km) above the Earth's surface to the top of the highest layer (opens in a new tab) of the Earth's atmosphere, the exosphere.
In the early 1960s, Haley applied the von Kármán criteria (orbital forces that exceeded aerodynamic forces) more specifically, determining that the real limit of space was about 52 miles (84 km) above the ground, according to McDowell. Now, now that Virgin Galactic appears to be about to launch paying passengers on suborbital trajectories, many people are wondering if those lucky space tourists will earn their astronaut wings. Von Kármán's original work emerged from a debate at a conference, but the first comprehensive publications on the limits of space were made by Andrew Gallagher Haley, the world's first professional in space law.
