Comments on: Where Is Space?

By: Gap Gen

Gap Gen — Fri, 11 Jan 2013 13:28:18 +0000

Actually, in reference to the galaxy mass thing, there are tons of mass definitions depending on when you take the cut off (or even stuff like measuring the maximum orbital velocity of stars around the galactic centre), and to complicate things theorists who make model galaxies prefer different values to people who interpret telescope observations of real galaxies. For example, observers often use the radius inside which half the light from the galaxy is contained, whereas theorists often don’t include stars in their models, so they can’t do that; meanwhile, observers can’t see dark matter, so measuring mass based on that is great for theorists and awful for observers.

By: Gap Gen

Gap Gen — Fri, 11 Jan 2013 13:07:09 +0000

Well, as Hentzau says, there’s no clear line where that happens, and the limit where you can’t tell the difference between the atmosphere and interplanetary space is partly dependent on how good your measurements are. There are a lot of annoying things like that in space stuff – I’ve sat through a very boring discussion about the best way to define the mass of a galaxy, because again they just kind of fade into nothing as you go further out.

By: A different Joe

A different Joe — Fri, 11 Jan 2013 03:30:35 +0000

That’s what they define as the boundry of space? I would have assumed it would be the height in which the gas composition ceased to thin and became uniform with the surrounding void. I ‘is are’ suprised.

By: Josh

Josh — Thu, 10 Jan 2013 09:07:52 +0000

Interesting post! My only contribution: “is are” is grammatically fine in this context.

By: Hentzau

Hentzau — Wed, 09 Jan 2013 14:08:18 +0000

Well, I’m not seriously going to go into the physics of balloons, but they generate lift through being filled with lighter-than-air gases like helium, and it’s the interaction of the surrounding atmosphere with the balloon telling it to get the hell out of here that makes the balloon go up. The further up the balloon goes the thinner the air gets, meaning there is less atmosphere telling the balloon to get to fuck, and meaning you need bigger and bigger balloons to produce the same amount of lift at higher altitudes.

Now, I think the record for an unmanned balloon flight is around 50-60km, and that balloon was absolutely huge (like, a couple of times the size of a zeppelin) to the point where I imagine you start to run into significant problems with the weight of the balloon fabric itself. That’s going to work together with the thinning atmosphere to produce a theoretical limit, although I have no idea where that limit would be.

By: innokenti

innokenti — Wed, 09 Jan 2013 13:37:21 +0000

Or the occasional crazed Austrian at around 40km…

Ehem. Just how high can balloons go? Theoretically and practically.