Drydon/NASA
Space, as a famous Starfleet captain once said, is the final frontier. But where is the actual frontier? There are no customs posts as you leave Earth, and 50 years after the Outer Space Treaty, there is still no internationally agreed definition of where space begins. With growing interest in tourist trips to the edge of space, it seems like a good time to try to nail this down.
In the 1950s the renowned aerodynamicist Theodore von Kármán threw his hat in the ring. …