Where is the Karman Line?

The Kármán Line is a widely accepted, though not universally agreed upon, boundary of space. According to the Fédération Aéronautique Internationale (FAI), it sits precisely at 100 kilometres (54 nautical miles; 62 miles; 330,000 feet) above sea level - but as with many things in science, legal definitions, and dinner-table debates, the reality is a bit more complicated (and a lots more mathematical).
    Despite being named after Theodore von Kármán, who calculated that conventional aircraft would become physically incapable of generating enough aerodynamic lift at 83.8 km (52.1 mi), the modern Kármán Line is more of a convenient estimate than a scientifically rigid boundary. The atmosphere doesn’t suddenly end at 100 km - it just keeps getting thinner, which makes defining an exact cut-off completely arbitrary. This has led to continued arguments among scientists, engineers, and the occasional space-obsessed pub-goer over where, precisely, space actually begins.

Legal and regulatory shenanigans
The Kármán Line exists largely for legal and regulatory reasons. Most international organisations, including the United Nations, have adopted it (or something close) to distinguish aircraft from spacecraft, which fall under different sets of laws. However, there is still no globally agreed-upon legal definition of the boundary between a country’s airspace and outer space. This means if you’re planning on launching yourself upwards at breakneck speeds, the question of when you officially become an astronaut might depend on whose rulebook you’re using.

Where does space begin (and earth end)?
Terms like “the edge of space” and “near space” are thrown around loosely - sometimes referring to high-altitude balloons, supersonic jet flights, or even the altitudes where the sky turns a deep shade of black. But when discussing space in an official sense, things become murkier.

Andrew G. Haley, in his book Space Law and Government (1963), offered a delightfully precise-yet-vague take on the Kármán Line:

“The line represents a mean or median measurement. It is comparable to such measures used in the law as mean sea level, meander line, tide line; but it is more complex than these. In arriving at the von Kármán jurisdictional line, myriad factors must be considered – other than the factor of aerodynamic lift. These factors have been discussed in a very large body of literature and by a score or more of commentators. They include the physical constitution of the air; the biological and physiological viability; and still other factors which logically join to establish a point at which air no longer exists and at which airspace ends.”

In simpler terms: it’s complicated.

Von Kármán weighs in:
In his autobiography, von Kármán explained how he arrived at the notion of a boundary between airspace and outer space. He noted that while aerodynamic lift still carried 98% of an aircraft’s weight at 38,500 metres (126,000 feet), by the time one reached 91,440 metres (300,000 feet), the situation reversed - there was simply no air left to contribute lift. At this altitude, only inertia (or as space scientists call it, Kepler force) kept a vehicle aloft. Thus, he proposed that this transition point could serve as a jurisdictional boundary: below it, nations could claim sovereignty; above it, space would be free for all.
    Earth’s atmosphere doesn’t just stop at 100 km - it stretches far beyond, becoming progressively thinner. If one were to include the thermosphere and exosphere as part of the atmosphere, the “edge of space” might have to be redefined at around 10,000 km (6,200 mi) up. But from a practical standpoint, the Kármán Line is based on a balance between aerodynamic lift and orbital mechanics.
    Aircraft stay airborne by generating lift from their wings, which requires forward motion through sufficiently dense air. The higher they go, the faster they need to travel to generate that lift. At a certain altitude, this required speed becomes so great that the vehicle is essentially an orbiting spacecraft rather than a flying aircraft.

    Von Kármán discussed these aerodynamic limits in a 1956 paper, calculating the speeds and altitudes where aircraft could still function without melting from aerodynamic heating. His findings indicated a crucial transition point at roughly 275,000 feet (52.08 mi; 83.82 km). However, the term “Kármán Line” wasn’t actually coined until 1959, when Andrew G. Haley used it in a paper, basing the altitude on von Kármán’s earlier work. He acknowledged that this limit was theoretical and could shift. In other words, it's an inexact boundary - and moves in any case, so why rely on it?

Unreliable boundaries
In fact, not everyone agrees on the FAI’s 100 km boundary. For example, the U.S. military and NASA have long considered the boundary of space to be 80 km (50 mi). In 2005, NASA even changed its astronaut qualification criteria so military and civilian personnel would be judged by the same standard.
It's also possible that NASA preferred the lower measure in order to have more 'real' astronauts for the PR and representation of their agency. there are even a few jet pilots who qualify as astronauts simply because they flew high enough for a moment or so. Never forget that the US is a capitalist nation first.

    The point is, is an imposed thing and rather made up than not - like a lot of lines drawn between people in the world, we do not have to accept them being placed where we're told they go - and isn't this how freedom works?