Recently the Billionaire Space Race culminated with both Jeff Bezos and Richard Branson, doing what I can tell without any dispute, "going up" and "coming down". The claim that either of them actually reached space however is hotly debated, with astrophysicist Neil deGrasse Tyson telling (paraphrased from this article)

First of all, it was suborbital...If you don't go fast enough to reach orbit you will fall and return to Earth...It's okay if you want to call it 'space,' just because average humans haven't gotten there before and it's a first for you. That's why it takes eight minutes to get into orbit and three days to reach the moon...So I don't see it as 'oh, let's go into space'. No. What you are going to have is a nice view of the Earth

According to CNN, Neil deGrasse Tyson says that neither Richard Branson nor Jeff Bezos has actually been put into orbit.

Of course, we got Elon Musk chiming in and trolling Bezos (I can't find the original one I saw so I am not sure if this is the real one).

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So where exactly does the Space start according to Governments and governmental agencies? Specifically speaking is there any legal definition of Outer Space in law.

[Edit I am citing NdT and Elon to only show there is a dispute/debate. Their opinion need not be legally considered]

My research

At the Legal Sub-committee meeting of 2018 UN COPUOS, United Nations the Committee for the Peaceful Use of Outer Space, some member states considered that a definition of where air space ends and outer space begins, was important because of space tourism and other activities extending to space. However, others including the US under Bush Administration pointed out that we have done quite well without such definitions and this has caused no problems so far.

Historically, it’s been difficult to pin that point at a particular altitude. In the 1900s, Hungarian physicist Theodore von Kármán determined the boundary to be around 50 miles up, or roughly 80 kilometers above sea level. Today, though, the Kármán line is set at what NOAA calls “an imaginary boundary” that’s 62 miles up, or roughly a hundred kilometers above sea level.

The Federation Aeronautique Internationale (FAI), which keeps track of standards and records in astronautics and aeronautics, also defines space as beginning a hundred kilometers up. It is, after all, a nice round number.

But the Federal Aviation Administration, the U.S. Air Force, NOAA, and NASA generally use 50 miles (80 kilometers) as the boundary, with the Air Force granting astronaut wings to flyers who go higher than this mark. At the same time, NASA Mission Control places the line at 76 miles (122 kilometers), because that is “the point at which atmospheric drag becomes noticeable,” Bhavya Lal and Emily Nightingale of the Science and Technology Policy Institute write in a 2014 review article.


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    What I don't understand is why NdGT makes such a big deal about actually orbiting. The definition of space is one dimensional (meters above sea level)(the actual value being the subject of debate) and not about orbiting or not.
    – Sandy
    Commented Aug 1, 2021 at 22:16
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    @user57467 Technically, we live on a rock that's in space, so we don't have to do anything to get there. We're already there. Commented Aug 2, 2021 at 13:43
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    @DonBranson But we're not in outer space.
    – Stef
    Commented Aug 2, 2021 at 14:24
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    @Sandy: As an educator, Neil deGrasse Tyson is concerned with correcting people's misconceptions about space, and people have a lot of misconceptions about getting into orbit — including the idea that the "hard part" of orbital space flight is getting high enough off the ground, and then you can effectively just floating around. See also Randall Munroe's article correcting the same misconception. Commented Aug 2, 2021 at 14:29
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    "Orbit" and "orbiting" are about your velocity, whereas "space" is variously defined by altitude/elevation. They are two different things with no direct relationship to each other. Neither Bezos nor Branson came close to being orbital. Commented Aug 2, 2021 at 15:43

2 Answers 2


Where does outer space legally start?

International law does not define the edge of space, or the limit of national airspace according to footnotes 2 and 3 of the Kármán line's Wikipedia entry.

Footnote 15, referencing the book International Law: A Dictionary by Boleslaw Adam Boczek, offers this:

The issue whether it is possible or useful to establish a legal boundary between airspace and outer space has been debated in the doctrine for quite a long time. … no agreement exists on a fixed airspace – outer space boundary

  • Ugh i wished i had read that last line earlier... so how do countries say "hey you have entered my airspace and you are no longer in outer space" or is the issue of airspace delimitation handled case-by-case? Commented Aug 2, 2021 at 15:23
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    @AdilMohammed: Practically speaking, if it has wings, it's an airplane and the airspace question is relevant. The Space Shuttle would be a difficult case with that definition, had it ever landed outside the USA. But it obviously was in space when over other countries.
    – MSalters
    Commented Aug 2, 2021 at 16:13
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    @AdilMohammed: I've heard it as a matter of being in orbit or not. Note that the ISS is in near earth space not outer space.
    – Joshua
    Commented Aug 2, 2021 at 17:51
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    @MSalters I have heard that 'technically' the country's airspace sovereignty extends to many altitudes, but practically it's only just as much as high as their anti-satellite guns can shoot. Not sure about the "wings" part, I read that space shuttles too have special wings. Need to look more into it Commented Aug 2, 2021 at 18:49
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    @Adil Mohammed There is no international agreement on the vertical extent of sovereign airspace (although this is an uncited claim)
    – user35069
    Commented Aug 3, 2021 at 13:35


According to the Fédération Aéronautique Internationale who are generally considered the record-keeping body on such matters, the Kármán line is where space begins and is rounded off to 100km above the Earth’s surface.

Of course, this is a Sorites paradox definition because there is no line where Earth’s atmosphere ends. The ground is definitely inside it (even at Mt Everest) and the Moon is definitely outside it. So, somewhere between those two.

In law, these sorts of category laws sued can be resolved in two ways: the legislation can define a hard border, such as a set age for voting or drinking, or it can leave it to be decided on a case-by-case basis, such as reasonableness.

The various “outer space” treaties do not actually define outer space. However, most regulatory bodies including the UN accept the FAI definition: if it flies below that, it’s an aircraft, above that, it’s a spacecraft.

Of course, it’s much easier to get things into space than to get them in Earth orbit. Space is just a matter of going up. Orbit requires going around and is much harder, breaking the axiom of “what goes up, must come down.”

Of course, if you want to get really pedantic, you’re not in space until you reach the heliopause, which both Voyager 1 & 2 have achieved or, if you’re really serious, intergalactic space.

As for what constitutes “achievement” both my kids have ribbons for rugby league although neither played beyond the age of 14. I could get them to jump tomorrow and give them astronaut’s wings.

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    "most regulatory bodies including the UN accept the FAI definition: if it flies below that, it’s an aircraft, above that, it’s a spacecraft." Could you cite/name the bodies. the main reason I kept Karman line in the research part and not in the main part, was because I thought it was probably only a scientific definition not a legal one. Also +1 for last line Commented Aug 1, 2021 at 17:16
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    This answer drifts around to a lot of stuff without clearly addressing the legal question.
    – user3392
    Commented Aug 2, 2021 at 0:10
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    @BenCrowell because theres no true legal answer? Space isn't something that is legally defined in the form of legislation or treaties, its something that several independent bodies (FAI, US government, NASA etc) define for their own requirements and other people accept.
    – user28517
    Commented Aug 2, 2021 at 3:04
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    "the Kármán line is where space begins and is rounded off to 100km above the Earth’s surface" – If by "rounding off" you mean "von Kármán computed the value to be 83.82 km / 52.08 mi, the US decided to round this off to 50 miles, the FAI decided to round it up to 100 km". Personally, I wouldn't call 83.82->100 "rounding off". Commented Aug 2, 2021 at 9:44
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    @JörgWMittag I’m an engineer and that’s exactly what rounding off means.
    – Dale M
    Commented Aug 2, 2021 at 12:24

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