# Is an endless siphon possible? **URL:** \ **Category:** Factual Questions\ **Created:** [October 2, 2011, 4:48am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331 "2011-10-02T04:48:54Z")\ **Posts on this page:** 19\ **Page:** 2
**Author:** ![Princhester](https://avatars.discourse-cdn.com/v4/letter/p/3e96dc/32.png) [@Princhester](https://boards.straightdope.com/u/Princhester)\ **Post date:** [October 2, 2011, 11:22pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/21 "2011-10-02T23:22:31Z")
> [@beowulff](#): > > You are misunderstanding how syphons work. “Gravity” doesn’t have very much to do with them. Other than cause the air pressure that drives them, you mean? 😉 ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [October 2, 2011, 11:29pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/22 "2011-10-02T23:29:12Z")
> [@CalMeacham](#): > > My favorite one was two finely-supported circuklar plates that pivoted amost frictioonlessly about their centers. They were placed with their centers far apart, but with sthe surfaces of the plates very close together, then in a bath of water. The idea was that surface tension would make the water climb the gap between the plates, which would make that side heavier, so the plates would turn in that direction (one clockwise, one counterclockwise), which starts the process over, so that you get perpetually counter-rotating plates. Well, I can see one reason why this might be your favorite - it sounds like it should work! Not that I seriously think somebody has thought up a real free energy machine and then everybody who has investigated it has made mistakes and come to the incorrect conclusion it doesn’t work. I think the underlying problem is my insight. But - can you help me see why this doesn’t work? The comments about surface tension at the lower end of the gap should not apply, as there are no gas interfaces down there. But I don’t get what else would explain it… ---
**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 3, 2011, 12:05am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/23 "2011-10-03T00:05:09Z")
The surface tension which is drawing up the water in the first place also acts as a “glue” that holds the wheels together and prevents them from turning. ---
**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\ **Post date:** [October 3, 2011, 10:49am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/24 "2011-10-03T10:49:58Z")
> [@Napier](#): > > Well, I can see one reason why this might be your favorite - it sounds like it should work! > > Not that I seriously think somebody has thought up a real free energy machine and then everybody who has investigated it has made mistakes and come to the incorrect conclusion it doesn’t work. I think the underlying problem is my insight. But - can you help me see why this doesn’t work? The comments about surface tension at the lower end of the gap should not apply, as there are no gas interfaces down there. But I don’t get what else would explain it… On further thought, a better way of looking at this might be that the force per length on the wheel surface is the same anyplace the wheel passes between water and air. It makes a capillary column rise where the column is narrow because that same force per length acts on a narrower column, which weighs less per that same length. But the wheel doesn’t experience an imbalance. Chronos, how close is that to your meaning? ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [October 3, 2011, 3:27pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/25 "2011-10-03T15:27:31Z")
> [@I\_am\_Snake](#): > > The sum of the gravity on the 4 foot side would be pulling the water in the one foot side, because there would be less force on it. The spiral side has 4x the water as the straight side. Each new foot of water you siphon up moves 4 feet of water on the spiral side 1 linear foot, but only 1/4 of a foot vertically. So the energy you get back from the falling water is exactly the same as the energy you put into the rising water. This, of course, assumes no friction losses of any kind. Which, in an “perpetual motion” discussion is kind of silly since anything can be a perpetual motion machine if you assume no losses. ---
**Author:** ![Rhythmdvl](https://avatars.discourse-cdn.com/v4/letter/r/85f322/32.png) [@Rhythmdvl](https://boards.straightdope.com/u/Rhythmdvl)\ **Post date:** [October 3, 2011, 3:43pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/26 "2011-10-03T15:43:19Z")
On this Board, we obey the [laws of thermodynamics](http://www.youtube.com/watch?v=Xy0UBpagsu8&feature=player_detailpage#t=7s)! ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 3, 2011, 4:07pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/27 "2011-10-03T16:07:30Z")
> [@Napier](#): > > On further thought, a better way of looking at this might be that the force per length on the wheel surface is the same anyplace the wheel passes between water and air. It makes a capillary column rise where the column is narrow because that same force per length acts on a narrower column, which weighs less per that same length. But the wheel doesn’t experience an imbalance. > > Chronos, how close is that to your meaning? I was thinking it had to be something like that. The same thing could be done with two almost parallel, slightly conical disks (like cymbals), so they can be close on one side, and apart on the other, and there doesn’t have to be counter-rotation or gluing effect. But of course, for some reason it still won’t work. Now writing this, I go back to **Chronos** ’ earlier comments on the wet cloth, and I’m thinking somehow that the forces that draw water into the close gap through capillary action are also resisting having that side sink into the water, through surface tension maybe. Maybe gravity is just fighting capillary effect and reaching an equilibrium at the close gap? ---
**Author:** ![DHMO](https://avatars.discourse-cdn.com/v4/letter/d/ecc23a/32.png) [@DHMO](https://boards.straightdope.com/u/DHMO)\ **Post date:** [October 3, 2011, 5:50pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/28 "2011-10-03T17:50:57Z")
A Water Treatment professional weighing in here: The pressure at the bottom of a column of Water is a function of the _height_ of the column, alone. The diameter of the container, and its shape, have no bearing on the pressure. A tube with a cross-section area of one square inch and 33 feet high will have a pressure at the base of 14.7 pounds per square inch. A tank with a cross-section area of 100 square feet and 33 feet high will have a pressure at the base of 14.7 pounds per square inch. You may curl and twist the tube all you like, but the pressure at the base will be the same, regardless of the shape or volume of the container. The premise of the OP is that there is a mostly U-shaped tube, with one leg slightly shorter than the other. The longer leg is submerged in the vessel of water, and the shorter leg is slightly above the surface of the water in the vessel. The tube reaches some maximum height above the surface, which is common to both legs. The pressure at the base of the leg which does not quite reach the surface will be less than the leg immersed in the water, no matter how much volume, or weight, is in the shorter leg. Water will flow out the longer leg, into the vessel, and suck the water up the shorter leg, to be replaced by air drawn into the tube through the small gap between the free end and the water’s surface. The discussion on capillary action, likewise, is flawed as a method to cause a perpetual siphon. The force of attraction between the water and the walls of the capillary tube are determined by the diameter of the tube, and the wetting factor for the particular variety of glass with water. The narrower the tube, the stronger the force drawing water into the submerged end. It is capillary action which draws water from the roots to the highest branches in the crown of the tallest trees, after all. But, in the case of trees (and plants, generally) evaporation and transpiration take water out at the leaves, which drives the capillary “pump.” The problem here is that, however you arrange the “perpetual siphon,” the “free” end where the water is supposed to come out experiences the _same force_ drawing water in as the end immersed in the vessel. And, since by the definition of the problem, the lower outlet of the free end is higher than the immersed end, any flow would be reverse what is required. ---
**Author:** ![Aemilius](https://avatars.discourse-cdn.com/v4/letter/a/a9a28c/32.png) [@Aemilius](https://boards.straightdope.com/u/Aemilius)\ **Post date:** [July 7, 2013, 10:31pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/29 "2013-07-07T22:31:20Z")
Permanent magnets are getting stronger all the time (5 Teslas currently). This may be possible now but if not, it won’t be long until it is… [The Cole Siphon](http://scienceforums.com/topic/27421-the-cole-siphon/) ---
**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:** [July 7, 2013, 10:53pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/30 "2013-07-07T22:53:44Z")
That’ll only be “continuous” in that it’ll continue to run so long as the water level in the starting reservoir is at a higher potential than the water in the ending reservoir. In other words, just like any other siphon. Adding magnets to the apparatus won’t change that fact, no matter how strong the magnets are. The only thing that might change would be that you might have to substitute a combined gravitational-magnetic total potential for the gravitational potential of a standard siphon. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [July 7, 2013, 10:55pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/31 "2013-07-07T22:55:10Z")
You seem to be getting your head handed to you pretty well over there. Why do you need a second set of scoffers to tell you your perpetual motion machine won’t work? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 7, 2013, 10:55pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/32 "2013-07-07T22:55:33Z")
> [@Aemilius](#): > > Permanent magnets are getting stronger all the time (5 Teslas currently). This may be possible now but if not, it won’t be long until it is… [The Cole Siphon](http://scienceforums.com/topic/27421-the-cole-siphon/) Your magnet could be infinitely powerful, and it still wouldn’t work. Hint: What’s the other pole of the magnet doing? ---
**Author:** ![eltro102](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@eltro102](https://boards.straightdope.com/u/eltro102)\ **Post date:** [July 7, 2013, 11:41pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/33 "2013-07-07T23:41:34Z")
> [@beowulff](#): > > Your magnet could be infinitely powerful, and it still wouldn’t work. > Hint: What’s the other pole of the magnet doing? ((water is diamagnetic, meaning it gets repelled no matter what pole)) ---
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [July 7, 2013, 11:41pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/34 "2013-07-07T23:41:39Z")
This reminds me of Robert Boyle’s flask, a self-flowing device that works with certain liquids. Plenty of videos online that demonstrate it, but it doesn’t work perpetually. ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 7, 2013, 11:47pm UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/35 "2013-07-07T23:47:07Z")
> [@eltro102](#): > > ((water is diamagnetic, meaning it gets repelled no matter what pole)) Precisely, which explains why the syphon won’t work. ---
**Author:** ![Aemilius](https://avatars.discourse-cdn.com/v4/letter/a/a9a28c/32.png) [@Aemilius](https://boards.straightdope.com/u/Aemilius)\ **Post date:** [July 8, 2013, 1:14am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/36 "2013-07-08T01:14:28Z")
_Exapno Mapcase "You seem to be getting your head handed to you pretty well over there. "_ Actually, it’s the other way around… The Administrator/Science Instructor/Mathematician has already signed off on the principle. The only thing we disagree on is whether the magnet is doing work by maintaining the depression on the surface of the resevoir. He says it is… I say it isn’t, any more than a refrigerator magnet does work. > **[Work (physics)](https://en.wikipedia.org/wiki/Work_(physics))** > > In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, for a constant force aligned with the direction of motion, the work equals the product of the force strength and the distance traveled. A force is said to do positive work if when applied it has a component in the direction of the displacement of the point of application. A force does negative work if it has a component opposite to the direction of the displac... ---
**Author:** ![Aemilius](https://avatars.discourse-cdn.com/v4/letter/a/a9a28c/32.png) [@Aemilius](https://boards.straightdope.com/u/Aemilius)\ **Post date:** [July 8, 2013, 1:23am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/37 "2013-07-08T01:23:28Z")
_Chronos “That’ll only be “continuous” in that it’ll continue to run so long as the water level in the starting reservoir is at a higher potential than the water in the ending reservoir.”_ Starting resevoir? Ending resevoir? There’s only one resevoir in the schematic… What are you talking about? ---
**Author:** ![Aemilius](https://avatars.discourse-cdn.com/v4/letter/a/a9a28c/32.png) [@Aemilius](https://boards.straightdope.com/u/Aemilius)\ **Post date:** [July 8, 2013, 1:28am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/38 "2013-07-08T01:28:45Z")
_Exapno Mapcase “Why do you need a second set of scoffers to tell you your perpetual motion machine won’t work?”_ Do you know really know the difference between a perpetual motion machine… [https://en.wikipedia.org/wiki/Perpetual\_motion](https://en.wikipedia.org/wiki/Perpetual_motion) and a siphon… [http://en.wikipedia.org/wiki/Siphon](http://en.wikipedia.org/wiki/Siphon) It doesn’t sound like it. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [July 8, 2013, 1:34am UTC](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331/39 "2013-07-08T01:34:09Z")
Perpetual Motion Machines exist, and work, and they are for real . . . In the form of the endless discussions, suggestions, and designs for Perpetual Motion Machines that have existed, perpetually working, since at least as far back as Da Vinci, I should think. If only we could harness all the energy to useful purpose! Problem is, these machines necessarily only run in circles. 😛 [Previous page](https://boards.straightdope.com/t/is-an-endless-siphon-possible/598331.md?page=1)