If a pipe extended from just above the ocean floor to outside the atmosphere, would water be sucked up it by the vacuum beyond the atmosphere? If a hole was made in the pipe, above sea level, how would that affect the flow of water? Would it stop it completely?
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14$\begingroup$ Consider all the oceans to be covered with a lot a pipes, where one end of them is inside the oceans while the other is outside the atmosphere. If water had to flow in one pipe(as asked in the question), it should flow throw all of them in this case. Now, a wise reader would notice that the pipes themselves are useless in this demonstration(forget about the Capillary action) and they can be removed; which means Earth's water should be flowing into space at the moment! $\endgroup$– AliCommented Jul 2, 2013 at 19:19
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$\begingroup$ @Ali - I like that reasoning more than many of the other answers... $\endgroup$– JoeCommented Jul 2, 2013 at 22:14
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$\begingroup$ @Ali But then where has the atmosphere gone? If it's between the pipes, then its depth will be increased due to all the space taken by the pipes. If it's inside the pipes, then the vacuum is gone and the water is no longer sucked up at all. $\endgroup$– MattSCommented Jul 4, 2013 at 6:39
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1$\begingroup$ @MattS The atmosphere is inside the pipes. But one end of the pipes is in vacuum. If the vacuum is going to suck them, it should suck them all! $\endgroup$– AliCommented Jul 4, 2013 at 10:20
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$\begingroup$ @Ali But this demonstrates a fundamental misunderstanding of the problem. In the original problem, the atmosphere is NOT inside the pipe - the pipe contains a vacuum. If the atmosphere is in the pipe, and the pipe is long enough to reach the vacuum of space, it really doesn't change anything. Earth's atmosphere is always against the vacuum of space, and yet isn't sucked off. The vacuum only sucks water up the pipe when the pipe is void of any atmosphere (or, at least, as much atmosphere are would usually be filling the space of the pipe). $\endgroup$– MattSCommented Jul 9, 2013 at 22:17
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4 Answers
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No, the water would not be sucked up.
Even if you take a pipe with vacuum, closed the top and dipped the open end of that pipe in water then the water would only rise 10 meters. After that the 'pull' from your vacuum is in balance with the force of gravity acting on a 10 meter water column.
Maybe needless to say: The top of the atmosphere is way higher than 10 meters.
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$\begingroup$ Is this dependent on the diameter of the pipe? $\endgroup$ Commented Jul 2, 2013 at 17:30
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9$\begingroup$ No. Not unless you make a really thin pipe where other forces come into play. (e.g. the way some trees get their water up). The key factor is the downward force of a column of water. If you make the pipe wider both forces (down and up) grow equally. $\endgroup$– HennesCommented Jul 2, 2013 at 17:32
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$\begingroup$ Just to add a name to the 'really thin pipe' effect I referred to: Capillary_action $\endgroup$– HennesCommented Jul 3, 2013 at 8:35
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Ask yourself this: why doesn't the vacuum of space just suck away our atmosphere? The reason is because of the earth's gravity, which pulls on the gas envelope around the planet to keep it in place. The phenomenon we call 'air pressure' is also the result of this.
The tube will only fill until its contents are being pulled down by gravity with the same force as the rest of the atmosphere. If the straw starts out with air in it, then the air in the straw will be pulled exactly as hard as any other column of air that size, and so the water will not move at all. If there is no air in it, only about 10 meters of it will fill (like Hennes said), only until the amount of extra water in the tube weighs the same amount as an equivalent area of the atmosphere does.
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$\begingroup$ Aye. I came back to add some more detail to my post. But the information in this answer does that nicely. $\endgroup$– HennesCommented Jul 3, 2013 at 8:33
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From what I understand, vacuums such as space don't actually "suck" or "pull" at all.
When a box of compressed air is introduced to a vacuum, the air molecules are actually being pushed by the other, higher-pressure air molecules into the low-pressure region of space. This means that, with regards to your question, there is a limit to how high the water can rise. This is determined by the force of air pushing down on the water to force it up the tube, balanced with the force of gravity pulling the water back down.
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$\begingroup$ +1: Hi frr171. Welcome to Physics.SE. We really encourage nice answers from new users :) $\endgroup$ Commented Jul 3, 2013 at 12:28
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What is a difference between a pipe let's say 1m wide, and the whole atmosphere, which is a "pipe" as well, just "extremly extremly wide"? Nothing. Therefore your pipe would not do anything.
