Where does outer space end and begin? It is a frequent question whose simplest answer is the Kármán line, But the matter becomes complicated when trying to establish an exact point where the border between the planet and the vacuum of outer space is.
Where is the Kármán line?
We often look at the planet as an orb with well-defined boundaries, but when studied in depth, it is not so simple. By definition we know that Kármán line marks the boundary between the Earth’s atmosphere and outer space, although the real question is where such a limit is located.
The line is named after the Hungarian-American aeronautical engineer Theodore von Kármán, who during the 1950s dedicated himself to searching for the limit of the . But it was not until 1975 that the term ‘Kármán line’ was formally established by lawyer Andrew G. Haley, the first to delve into matters of space law and who became interested in the matter given that the Kármán line would also mark the end of that of nations and therefore, the laws would not be applicable crossing the threshold.
As a good aeronautical engineer, Kármán calculated that the limit of the atmosphere would rise approximately 100 kilometers above average sea level. In this way, the altitude would be consistent with engineering calculations where orbital forces exceed aerodynamic forces. In this part of the planet, the density of the atmosphere is so thin that aircraft would have to reach a force comparable to the Earth’s orbital speed to continue in flight, an impressive speed that is impossible for ships with wings and propellers, one of the reasons why they do not reach such heights.
Years later, the International Aeronautical Federation () accepted the limit stipulated by Kármán. Today this institution and many others point out that the Kármán line, that is, the limit between the atmosphere and space, is 100 kilometers above average sea level. But there is no clear consensus and there are those who claim that the limit would be a little lower.
The atmosphere is not so simple
The Earth’s atmosphere is not a simple bubble of gases that covers the planet, each of its layers is essential to maintain the balance of life. But such complexity also applies to its formation and completion; the atmosphere does not end abruptly, but rather becomes thinner at higher altitudes and therefore, it does not have a completely defined upper limit.
It is precisely this characteristic that has put meteorologists, physicists and engineers in a dilemma to determine where exactly the atmosphere ends and outer space begins. Although the International Aeronautical Federation establishes that the Kármán line rises 100 kilometers above the surface of the average sea level, what do other institutions say about it?
According to the Administration, the Kármán line rises 80 kilometers above average sea level. Added to this calculation is the US military, which has also placed the edge of the planet at the same altitude as NASA. But the atmosphere fades in such a complex way that even today the issue is under discussion and the world’s most important institutions on exploration and space law are trying to reach an agreement.