# Hollow tube from earth into outer space **URL:** \ **Category:** Factual Questions\ **Created:** [October 13, 2011, 1:00pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524 "2011-10-13T13:00:27Z")\ **Posts on this page:** 16\ **Page:** 2
**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\ **Post date:** [October 14, 2011, 7:55am UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/21 "2011-10-14T07:55:04Z")
> [@h4ckys4ck](#): > > But if I suck the straw the water comes out. Doesn’t space suck a bit? Space doesn’t suck - the earth blows. [QUOTE=Ludovic] I’ve been meaning to ask something like this. What would happen if we built this, and then pumped out the air from the bottom? Would it refill from the scant atmosphere in semi-outer space to the same pressure as before the pumping, or would it only refill to the pressure in the outer atmosphere? [/QUOTE] The straw would collapse from the external pressure, like trying too hard to suck a thickshake up a weak straw. Si ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [October 14, 2011, 8:15am UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/22 "2011-10-14T08:15:02Z")
> [@si\_blakely](#): > > The straw would collapse from the external pressure, like trying too hard to suck a thickshake up a weak straw. If a 100-mile cylinder was strong enough to remain standing, there’s a good chance that it’s strong enough to withstand 1 atm of air pressure. Interestingly, one of the possibilities for building a supertall structure (tens of kilometers) is to make it inflatable. Sort of the opposite approach to what’s proposed here. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [October 14, 2011, 12:13pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/23 "2011-10-14T12:13:44Z")
> [@Little\_Nemo](#): > > It would end up the same pressure as the outside atmosphere is. Gravity would keep pulling air down and that would keep air flowing into the open top until the pressure inside the tube was the same as the pressure outside the tube. > > I don’t know how long this would take (it’s going to depend on how high your tube is) or what the mixture of gases will be inside the tube. This assumes that the top of the straw is below the top of the atmosphere. If the top of the straw is well above the “top” of the atmosphere, then once it’s been evacuated, it should remain so indefinitely. I realize that the “top” of the atmosphere is a fuzzy thing, but if for example the straw is a couple thousand miles tall, I would expect very few atoms of earth’s atmosphere to be lofted in over the top edge of the straw. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [October 14, 2011, 5:23pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/24 "2011-10-14T17:23:05Z")
> [@Machine\_Elf](#): > > This assumes that the top of the straw is below the top of the atmosphere. If the top of the straw is well above the “top” of the atmosphere, then once it’s been evacuated, it should remain so indefinitely. I realize that the “top” of the atmosphere is a fuzzy thing, but if for example the straw is a couple thousand miles tall, I would expect very few atoms of earth’s atmosphere to be lofted in over the top edge of the straw. The question did refer to there being some atmosphere at the top so I went with that assumption. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 14, 2011, 5:27pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/25 "2011-10-14T17:27:38Z")
The thing is, there really isn’t a top of the atmosphere. It just sort of gradually diminishes. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [October 14, 2011, 5:55pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/26 "2011-10-14T17:55:08Z")
What if you build a giant straw on an infinite plane on an infinite treadmill? ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [October 14, 2011, 7:01pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/27 "2011-10-14T19:01:26Z")
> [@Chronos](#): > > The thing is, there really isn’t a top of the atmosphere. It just sort of gradually diminishes. Sorry if I wasn’t clear. When I said “some atmosphere at the top” I meant some atmosphere at the top of the tube. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 14, 2011, 8:39pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/28 "2011-10-14T20:39:27Z")
Right, that’s related to what I was saying. The pipe can’t extend to the “top of the atmosphere”, since there is no well-defined top, so there will still be some traces to leak in at the top of the pipe. ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [October 14, 2011, 8:59pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/29 "2011-10-14T20:59:04Z")
> [@Chronos](#): > > Right, that’s related to what I was saying. The pipe can’t extend to the “top of the atmosphere”, since there is no well-defined top, so there will still be some traces to leak in at the top of the pipe. That’s true, but nevertheless the pressure at 100 km would be called a hard vacuum by any scientist. Even intergalactic space has some amount of free gas, but no one calls that part of an atmosphere. So although we can’t draw a hard boundary, we can name an altitude which is effectively outside the atmosphere. Traditionally, [100 km](http://en.wikipedia.org/wiki/K%C3%A1rm%C3%A1n_line) marks the boundary between the atmosphere and space. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 14, 2011, 9:48pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/30 "2011-10-14T21:48:04Z")
So suppose the tube is 100 km tall, 1 m in diameter, and initially a hard vacuum. Can anyone here estimate how quickly the tube will come up to atmospheric pressure? Say within 0.1%? ---
**Author:** ![Dr.Strangelove](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr.strangelove/32/6613_2.png) [@Dr.Strangelove](https://boards.straightdope.com/u/Dr.Strangelove)\ **Post date:** [October 14, 2011, 10:31pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/31 "2011-10-14T22:31:33Z")
> [@ZenBeam](#): > > So suppose the tube is 100 km tall, 1 m in diameter, and initially a hard vacuum. Can anyone here estimate how quickly the tube will come up to atmospheric pressure? Say within 0.1%? That would require an integral which I don’t have time to do now, but I can set an approximate lower bound. Surface pressure is about 101.325 kPa, or 101325 kg/(m_s^2). Multiply by the area of the tube (0.785375 m^2) to get 79578 kg_m/(s^2), and then divide by 9.8 m/s^2 to get 8120 kg of air in the tube. Flow through an orifice is equal to f = C_A_sqrt(2p(P1-P2)) C is a flow coefficient, or about 0.8 for this setup A is the area of the opening, or again 0.785375 m^2 p is the air density, or about 0.000000019131 kg/m^3 at 100 km P1 the pressure inside the tube, or 0 Pa P2 is the pressure outside, or 5 Pa Do the math and you get 2.748e-4 kg/s. Divide into the 8120 kg and you get 29548762 seconds, or nearly a year. Of course things will go more slowly as time goes on. I’ll take a guess and say about 10 years to get to 99.9% density. I’m sure I’m within a factor of 2, at any rate… ETA citations: [http://physics.bu.edu/~py502/lectures3/l07.pdf](http://physics.bu.edu/~py502/lectures3/l07.pdf) > **[Atmospheric Pressure](http://homeclimateanalysis.blogspot.com/2010/03/atmospheric-pressure.html)** > > Our extreme greenhouse argument has reached the point where we need a relationship between atmospheric pressure and altitude. Those of you ... > **[Orifice plate](https://en.wikipedia.org/wiki/Orifice_plate)** > > An orifice plate is a device used for measuring flow rate, reducing pressure or restricting flow (in the latter two cases it is often called a restriction plate). > An orifice plate is a thin plate with a hole in it, which is usually placed in a pipe. When a fluid (whether liquid or gaseous) passes through the orifice, its pressure builds up slightly upstream of the orifice but as the fluid is forced to converge to pass through the hole, the velocity increases and the fluid pressure decreases. A ... > **[SOHIBSLOT - Situs Judi Slot Online Dan Bandar Toto Togel Terpercaya](https://gasho.org)** > > sohib slot merupakan platform situs judi slot online dan juga bandar toto togel terpercaya dengan hadiah 4d terbesar 9,9jt dan bet paling murah 100 rupiah, sohibslot juga menyediakan rtp slot langsung dari provider pragmatic play dan pg soft ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 15, 2011, 1:32pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/32 "2011-10-15T13:32:40Z")
Thanks **Dr. Strangelove**. I really had no feel for if it would fill up in a few years like you showed, or if it would take thousands or more. ---
**Author:** ![hibernicus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/hibernicus/32/2802_2.png) [@hibernicus](https://boards.straightdope.com/u/hibernicus)\ **Post date:** [October 15, 2011, 5:36pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/33 "2011-10-15T17:36:15Z")
> [@ZenBeam](#): > > Thanks **Dr. Strangelove**. I really had no feel for if it would fill up in a few years like you showed, or if it would take thousands or more. Just to be clear, Dr Strangelove’s answer is for the case where the tube is not open to atmosphere at the bottom, only at the top, where there is hardly any atmosphere available. Is that what you meant? It would fill much more quickly from the bottom. ---
**Author:** ![user\_hostile](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/user_hostile/32/474_2.png) [@user\_hostile](https://boards.straightdope.com/u/user_hostile)\ **Post date:** [October 15, 2011, 6:07pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/34 "2011-10-15T18:07:11Z")
> [@Dr.Strangelove](#): > > That would require an integral which I don’t have time to do now, but I can set an approximate lower bound. > > Surface pressure is about 101.325 kPa, or 101325 kg/(m_s^2). Multiply by the area of the tube (0.785375 m^2) to get 79578 kg_m/(s^2), and then divide by 9.8 m/s^2 to get 8120 kg of air in the tube. > > Flow through an orifice is equal to > f = C_A_sqrt(2p(P1-P2)) > C is a flow coefficient, or about 0.8 for this setup > A is the area of the opening, or again 0.785375 m^2 > p is the air density, or about 0.000000019131 kg/m^3 at 100 km > P1 the pressure inside the tube, or 0 Pa > P2 is the pressure outside, or 5 Pa > > Do the math and you get 2.748e-4 kg/s. Divide into the 8120 kg and you get 29548762 seconds, or nearly a year. > > Of course things will go more slowly as time goes on. I’ll take a guess and say about 10 years to get to 99.9% density. I’m sure I’m within a factor of 2, at any rate… > > ETA citations: > [http://physics.bu.edu/~py502/lectures3/l07.pdf](http://physics.bu.edu/~py502/lectures3/l07.pdf) > [Home Climate Analysis: Atmospheric Pressure](http://homeclimateanalysis.blogspot.com/2010/03/atmospheric-pressure.html) > [Orifice plate - Wikipedia](http://en.wikipedia.org/wiki/Orifice_plate) > [SOHIBSLOT - Situs Judi Slot Online Dan Bandar Toto Togel Terpercaya](http://gasho.org/rotron%20pages/orifice%20flow%20calculation.htm) Now the question is: How can I use this to win a bar bet? ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [October 15, 2011, 8:26pm UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/35 "2011-10-15T20:26:30Z")
> [@hibernicus](#): > > Just to be clear, Dr Strangelove’s answer is for the case where the tube is not open to atmosphere at the bottom, only at the top, where there is hardly any atmosphere available. Is that what you meant? It would fill much more quickly from the bottom. Yes, I meant open only at the top. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [October 16, 2011, 1:27am UTC](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524/36 "2011-10-16T01:27:54Z")
> [@Consensus](#): > > Vacuum doesn’t suck, it’s the pressure that wants to expand. You wouldn’t say that if you’d tried living in one.:mad: [Previous page](https://boards.straightdope.com/t/hollow-tube-from-earth-into-outer-space/599524.md?page=1)