Will a Siphon Function on the Moon?

  • Context: Undergrad 
  • Thread starter Thread starter Steve B
  • Start date Start date
  • Tags Tags
    Vacuum
Click For Summary

Discussion Overview

The discussion revolves around the functionality of a siphon on the Moon, particularly in a vacuum environment with gravity present. Participants explore the principles behind siphoning, including the roles of atmospheric pressure and gravity, and whether a siphon could operate effectively in such conditions.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants assert that a siphon requires atmospheric pressure to function, suggesting that in a vacuum, the liquid would not flow as expected.
  • Others question how a liquid could exist in a vacuum, noting that even if surface pressure is zero, pressure increases with depth, similar to atmospheric pressure.
  • One participant proposes that gravity could maintain the liquid in a tub even in a vacuum, while surface tension might also play a role.
  • Another participant discusses the concept of negative pressure, explaining that it can allow for liquid transport in certain conditions, such as in trees, but raises concerns about embolisms in typical siphon setups.
  • There is mention of specialized siphons that might work under specific conditions, despite the general failure of typical siphons in a vacuum.
  • Some participants express confusion about the concept of negative pressure and its implications for siphoning liquids.

Areas of Agreement / Disagreement

Participants do not reach a consensus; multiple competing views remain regarding the mechanics of siphoning in a vacuum and the definitions of pressure involved.

Contextual Notes

Limitations include assumptions about the behavior of liquids in a vacuum, the definitions of pressure, and the conditions under which siphons might operate effectively. The discussion does not resolve these complexities.

  • #31
cjameshuff said:
No. The bottle collapses because of the external air pressure and the lack of countering pressure from inside. As I've said before, there is no pressure from a vacuum.




Again with the reverse airlock, and with structures collapsing. Can you describe just what, exactly, a "reverse airlock" is? And what could possibly cause a container containing nothing, surrounded by nothing, to collapse? What is the source of the forces on its walls causing it to collapse, when there's nothing on either side of them?




As I've explained in detail, no, it wouldn't. It takes no structural integrity to hold a vacuum in vacuum. None. The forces on the walls of the structure are precisely zero, no matter the changes in volume you make.




What does "Irrelevant to it becoming void" mean?
You'd change its volume, yes. That's not theory, it's reality, there's numerous ways of making structures that change in volume. The part you keep missing is that when vacuum is concerned, it doesn't matter what the volume is.

It is as tyroman said. Air pressure will support the fluid in the connecting tube and allow that tube to rise to a greater height before breaking the fluid column, but it acts on both ends of the tube, and has nothing to do with moving fluid through the siphon.


You are not making sense in your observations; “there is no pressure from a vacuum”. I did not state there is pressure in a vacuum, I am pointing out the fact that putting a capsule in vacuum is a structural dependent action. And if you don’t understand that let me break it down. If you vacuum a capsule you could keep vacuuming until it implodes. But besides that, to siphon liquid is not dependent on air pressure. The definition also states to immerse a tube. Look up siphon in the oxford dictionary then we can have a discussion about how to siphon water in a vacuum.
And to answer your question” What is a reveres airlock” to have an airlock in space is to exit a spacecraft without compromising the air in the space craft. so to have a reverse airlock I thought would be to exit a vacuum without compromising the vacuum.
And to say a vacuum is not pressure dependent is silly in this context because its put forward there is a capsule involved and that pressure would be relevant even though I didn’t say it is pressure dependent. You stated “ The bottle collapses because of the external air pressure and the lack of countering pressure from inside”
I’m sorry but this would make pressure relevant..
 
Physics news on Phys.org
  • #32
threadmark said:
You are not making sense in your observations; “there is no pressure from a vacuum”. I did not state there is pressure in a vacuum,

You stated a container in vacuum would implode if the volume of vacuum inside it were increased by drawing a liquid out with a siphon:

threadmark said:
if you want to siphon the fluid out of the bath tub into the vacuumed room, it’s not a problem. But if you try to siphon the fluid out of the room it’s impossible because there is no space to fill the void. The vacuum is proportionate to the volume of the room. if you take something out you increase the volume. if you increase the volume whilst in vacuum the room would implode.


threadmark said:
I am pointing out the fact that putting a capsule in vacuum is a structural dependent action.

That statement has no meaning. The phrase "is a structural dependent action" does not make sense.


threadmark said:
And if you don’t understand that let me break it down. If you vacuum a capsule you could keep vacuuming until it implodes.

What could cause a container in vacuum to implode? Implosion implies that an inward force is being applied to the structure of the container...by stating that this would happen, you are claiming that a vacuum exerts pressure.


threadmark said:
And to answer your question” What is a reveres airlock” to have an airlock in space is to exit a spacecraft without compromising the air in the space craft. so to have a reverse airlock I thought would be to exit a vacuum without compromising the vacuum.

That's just an airlock, there's nothing reversed about it.


threadmark said:
And to say a vacuum is not pressure dependent is silly in this context

No, it's just another meaningless phrase. Those words do not have meaning when put together in that way.
Freezing is pressure dependent, boiling is pressure dependent, vacuum is a state of zero pressure and absence of matter...it depends on nothing.


threadmark said:
because its put forward there is a capsule involved and that pressure would be relevant even though I didn’t say it is pressure dependent. You stated “ The bottle collapses because of the external air pressure and the lack of countering pressure from inside”
I’m sorry but this would make pressure relevant..

This was in response to a remark you made about sucking water from a plastic bottle. You're not in vacuum, the bottle is not in vacuum, the fact that the bottle collapses is entirely irrelevant to the discussion about siphons in vacuum.

You seem extremely confused about pressures and vacuum in general. The question you asked in another thread, "Isn’t the act of a vacuum to exert all possible mass whilst maintaining the structure the vacuum resides in?", simply makes no sense...to start with, mass isn't something that's exerted, and a vacuum doesn't exert anything. Once again, a vacuum is just an absence of matter. Aside from relatively tiny effects like photon pressure and the Casimir effect, a vacuum exerts precisely zero force...there's nothing there to exert force. There's nothing there to change properties based on volume, there's no pressure. You don't need "space to fill the void".

Out in the open here on Earth, reducing pressure in a container with insufficient structural strength to support the outside atmospheric pressure will cause the container to implode. Put it in a vacuum chamber, and you can draw a vacuum in even the flimsiest container without it imploding. If that vacuum chamber can support an atmosphere of external pressure, it doesn't matter how many vacuum pumps you hook up to it or how good they are, it won't implode. Once the air has been removed, the interior is a vacuum, and that's that.
 

Similar threads

  • · Replies 17 ·
Replies
17
Views
5K
Replies
31
Views
6K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
10
Views
11K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 11 ·
Replies
11
Views
7K
  • · Replies 21 ·
Replies
21
Views
5K
  • · Replies 10 ·
Replies
10
Views
4K