# Vacuum Tube

## Main Question or Discussion Point

If you have a tube with no air in it, making the the tube a vacuum. And stuck one end in space and the other end in the earth's ocean. Then Opened both ends. Would it suck all the water out into space? If not what would happen?

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turbo
Gold Member
What do you think will happen? Do you have an educated guess?

What do you think will happen? Do you have an educated guess?
I don't know that's why I asked... But if i had to make an educated guess I would say no.

turbo
Gold Member
OK, what do you think would happen to the pressure gradient in the tube?

I don't know much about Physics. But I just want to know what would happen.

I read about pressure gradient and what I take from it, that the water would not go up it because the pressure from the atmosphere would keep it down. Would that also keep down air and other gases if that's the case?

turbo
Gold Member
Is there a chance that the pressure gradient in the tube might approximate the pressure gradient in the atmosphere outside the tube? If you don't think so, please explain your reasoning.

Well if the tube is sealed with no air inside of it. Thus creating a vacuum in the tub. A vacuum has much less pressure than the atmosphere's pressure. As soon as you open it , the water should rush into the tube. I just don't know if the water will go all the way up it into space, or just stop from the pressure adjusting to the atmosphere's pressure. Please correct me with the answer if I am wrong.

turbo
Gold Member
Well if the tube is sealed with no air inside of it. Thus creating a vacuum in the tub. A vacuum has much less pressure than the atmosphere's pressure. As soon as you open it , the water should rush into the tube. I just don't know if the water will go all the way up it into space, or just stop from the pressure adjusting to the atmosphere's pressure. Please correct me with the answer if I am wrong.
I am not going to give you the answer. Think it through. What will happen to the pressure differential along the length of the tube from the ocean to space?? You can figure this out.

rcgldr
Homework Helper
At some point in the tube the pressure will become low enough that the water turns into a vapor. Clearly the pressure at the bottom of the tube will be the same as the water at that depth, once everything stabilizes. After a stable state is reached, I'm not sure how high past sea level the liquid water in the tube would go before turning into vapor. If it goes higher at all, then the pressure gradient in the tube is steeper inside the tube where there's liquid water. I'm don't know about the pressure gradient of steam versus air.

Well the only part that's confusing me is that on the other end of the tube is space, which is also a vacuum.

The atmosphere is also exposed to a vacuum on its upper surface. To make it easy for you the atmosphere exerts a pressure of roughly 15 lbs/in^2 (sorry I don't have the metric equivalent handy). This means it will raise a column of water to a height so that he base of the column exerts that pressure.