Is there an accepted definition of "space"

Pretty often I’ll hear things said like “so-and-so was the first reptile in space” or something. I hear it so often, quoted as part of a fact, that it suggests that there is some definition of where space begins that everyone has agreed upon. Unforunately, I’ve never heard this definition.

Perhaps if I knew this I could figure out the difference between Alan Sheppard (sp?) and John Glenn’s achievements … one was the first American in space, the other was the first American to…?

Also, if I knew this I could figure out what the first man-made object in space was. I think it is an artillery shell fired from Germany Kaiser Wilhelm Geschutz during the First World War, but I’ve never heard anyone say that. It’s just that the cannon is said to be “transatmospheric” which sounds to me like sending its projectile in space.

What I’m looking for is a quantitative definition, if any exists. Space may very well begin where the atmosphere stops, but that doesn’t tell me much, given that atmosphere charts never have a line on them that says “atmosphere stops here”; they usually just seem to extend upwards indefinitely into lower and lower pressures.

Any similarity in the above text to an English word or phrase is purely coincidental.

The final frontier.

I’ve heard it defined as 50 miles above sea level, but also a mere 100,000 feet. Leaving the definitions aside, think of it as the point where there is not enough atmosphere to produce any measurable lift or drag, and where the sky turns black and you can see the stars in daytime.

By the way, Alan Shepard was the first American in space, John Glen was the first American to orbit the earth. But before either of them, Yuri Gagarian, from the Sobviet union, did both.

I think I would define space as, “the universe,” thus all things are in space. Maybe what you are looking for is outer space, which is commonly defined as, “beyond the atmosphere of earth.”

“There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences.”
~P.J. O’Rourke~

Yeah, I figured Gagarin had both bases covered so I didn’t ask about him.

And I think I had Glenn and Shepard mixed up … I knew Shepard was first but for some reason I thought he orbited the earth without going into space … don’t know how he would’ve done that, in retrospect.

I like the qualitative defintions, but it seems like the atmosphere creates measurable drag at some pretty extreme altitudes. I thought it was atmospheric drag, for example, that brought down Skylab, which seems like it should’ve been way out there.

Yes, Unclebeer, I was really looking for the definition of outer space. I usually just leave off the “outer”.

But if we accept 100,000 feet as “space,” Col. Kittinger beats 'em all.

Wait a minute, Mjollnir. Did they fire the poor Colonel out of the Paris Gun? Just kidding. Was he one of the X-15 pilots? I’m just surprised since I don’t recall his name. Or was he maybe an X-1 pilot? SR-71? Piper Cub?

World’s highest parachute jump at just over 102,000 feet from a balloon.

And back to the definition of outer space. I have found another common definition of outer space that says it is anywhere outside of the solar system. So I guess the floor is re-opened for debate.

“There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences.”
~P.J. O’Rourke~

The only definition I had heard was by someone named von Karman: the altitude where planes lose aerodynamic lift.

A web search revealed the following site:

Space Law, Masters thesis at the Stockholm University Faculty of Law: The Swedish Law on Space Objects, from 1996.
© 1996 Daniel Granqvist

Quand les talons claquent, l’esprit se vide.
Maréchal Lyautey

Hey! I say we put the limit at 100km. I might even be able to remember that. “Uh, yeah, dat’s it, it’s 100,000 feet. No, that’s too low. Must been 100,000 yards. But it got made up by some Swede guy, so it musta been 100,000 hectares or joules or something.”

Okay, so I’m gathering that there isn’t a single accepted definition for space. Which means that all those people, in very un-Straight Dopish fashion, were using a vague term without defining it. For shame!

I wish I had more facts but –

I just finished reading a book about the X-15 program entitled The Edge of Space, IIRC, by Milt Thompson (one of the X-15 pilots). Several of the pilots in the program were awarded astronaut status because their flights exceeded a certain height, but the specific altitude required was never stated. The maximum altitude achieved was 300,000 feet or so, I believe, and they routinely flew over 100,000 feet without being honored that way, so it was (duh!) somewhere in between.

Of course, being designated an astronaut may not be the most scientific method of determining where space begins. One other salient point was that the X-15 holds the record for the highest flying airplane. Although other vehicles have flown higher (the space shuttle on its return, for example), craft that fly higher than 350,000 feet are considered spacecraft by the record people. And, curiously, it is the second highest X-15 flight that set the record. The highest flight did not exceed the previous record by the required 10%. In fact, the author made a point of the fact that the record could be exceeded someday, but only once, since any new record height would be less than 10% from the 350,000 foot limit.

Finally, the X-15 routinely flew beyond the limit of aerodynamic control of the aircraft and had a reaction control system for operation outside the atmosphere. The speeds and altitudes that it operated in were only exceeded by the space shuttle, which, BTW, owes a great deal to the X-15 research. In terms of available thrust and size and weight the X-15 was in the same league as the Redstone rocket that Alan Shephard used in his sub-orbital flight.

“If ignorance were corn flakes, you’d be General Mills.”
Cecil Adams
The Straight Dope

Dictionary of Technical Terms for Aerospace Use
Edited by Daniel R. Glover, Jr.
NASA - Lewis Research Center, Cleveland, Ohio


  1. Specifically, the part of the universe lying outside the limits of the earth’s atmosphere.

  2. More generally, the volume in which all celestial bodies, including the earth, move.

“There is only one basic human right, the right to do as you damn well please. And with it comes the only basic human duty, the duty to take the consequences.”
~P.J. O’Rourke~

Pluto: According to Tom Wolfe’s book The Right Stuff, the X-15’s were forbidden to fly above a certain altitude because that would have made them “space” craft, and that would have raised the hackles of certain political factions that wanted NASA (or was it still NACA back then?) to be “first Americans into space”.

Of course, the “edge” of space is just a matter of opinion. I think it could be argued that the German V2’s got into space, couldn’t it? They certainly got beyond the realm of aerodynamic control.

Incidentally, while we’re talking about The Right Stuff, recent evidence from the recovery of Liberty 7 strongly suggests that Grissom did not blow his hatch “in a panic” (as he has been accused of – and as Wolfe’s book faintly implied). The evidence now seems to show that it was an off-kilter impact with the water that caused the hatch to pop off. Most significant is that there is no sign that a pyrotechnic charge was ignited.

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The X Prize ( ) also uses 100km as the limit. They are awarding a 10-million dollar prize for a privately funded reusable vehicle that can carry three people to this altitude.

Note that it doesn’t have to be an orbital flight. To enter an orbit requires a 7km/sec (roughly Mach 25)[1] speed in addition to a high enough altitude. Alan Shepard’s flight was not an orital flight - he went over 100km altitude but fell right back down. John Glenn’s flight was orbital, as was Yuri Gagarin’s.

[1] Of course you can’t use the Mach scale in space, but if this speed was attained in the atmosphere the Mach number would be about this much.