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Author Topic: How do Trees Really lift Water to their Leaves?  (Read 244865 times)

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #75 on: 04/05/2005 09:03:35 »
The soft tube collapsing at relatively low elevation levels during the bench top experiments does not reflect the properties of the tough nylon tube now used. It simply will not collapse unles it is heated, which it is not during the experiments.

RE: taking one tube out of the bottle. There is a huge difference in taking the tubes out at a relatively low height. I.E. below the 33 feet limit. When tubes are removed at this height there is a siphoning effect that can be initiated. When over the 33 feet limit, the whole experiment behaves differently, in the the water will now remain suspended in the tubes, rather than flowing out as one would expect to happen. So I guess the elasticity of water does not significantly increase under the 33 feet limit.

Incidentally, I cant remember what happens when one tube is removed as it is usually removed when the bead of water has broken and the levels returned to 33 feet with vacuum above the levels. So I can't honestly answer this question, but will test it next time I use the experiments.

with regards to your other point on the levels not changing significantly as the tube is raised.
One possible explanation for this is that the tube elongates, due to the weight of water plus the weight of the nylon tube maybe.

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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #76 on: 04/05/2005 10:17:53 »
If that is the case the stability of the bead is an interesting effect to do with syphonish things, as this would require the bead of water to be somehow attached at the top...  although I would like to see the exact setup before being sure.

Maybe next time I come home to visit my parents I could pop over to Paignton on my way back to the train and have a look?

However even if this is the case your setup isn't a good model of the structures in a plant and even if it was it wouldn't explain the majority of what is happening due to energy concerns.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #77 on: 04/05/2005 10:52:42 »
Dave, when I came to you In Brixham, I asked if you would be in a position to repeat my experiments. After visiting your website, I believe you are in a better position to do this than anyone else, with your connections at Chaossience.
I Would like to ask, if you would consider taking this experiment to your next demonstration, and I would be willing, (wrong word) Delighted to come and offer assistance, and provide your team with the tubing, etc.
How do you feel about this?
Respectfully   Andrew K Fletcher

http://www.chaosscience.org.uk/pub/public_html//index.php?topic=Events&menu=Events_
From your site:
Our events normally take the form of a room full of experiments each with at least one demonstrator, getting people involved and explaining what is happening.
We also run and help with various other events in Cambridge and will go into local schools


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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #78 on: 04/05/2005 12:07:02 »
I would want to understand what was going on really well before taking it anywhere near kids, boiling lots of water is a hassle and we don't often have anywhere which is over 10m high in the venues...

I would be interested to see it though.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #79 on: 04/05/2005 12:13:57 »
A spiral staicase is a great place to conduct the experiment and many schools have several floors, presenting ideal locations.

The boiling water is not a problem as this can be done at home, taking the cool pre-boiled water along for the experiment. I even take along the coil of tubing, pre-filled with the boiled water and the saline solution in the centre, as this saves time at the School. But more water can be taken along for repeating the experiments.



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Offline NakedScientist

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Re: How do Trees Really lift Water to their Leaves?
« Reply #80 on: 09/05/2005 18:26:47 »
I'm going to move this thread to the 'cells' forum shortly, so look out for it there...

TNS
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #81 on: 10/05/2005 10:30:21 »
Why are you moving the thread? As this is a physics discussion, Can you please enlighten me why you believe it belongs on the cells forum?

Andrew
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #82 on: 10/05/2005 14:11:29 »
Although most of the discussion has been on physics, the question is actally biology, and a lot of the evidence is microscopic.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #83 on: 10/05/2005 14:31:21 »
I beg to differ David, None of my experimental models are microscopic. And yes, most of the discussion is on physics. The movement of fluids, fluid dynamics.

A Decisive Step: 1889–1924
The crucial period for our current views on the mechanism of water transport in plants were the years between 1889 and 1896. As a cornerstone we have a monumental book, Eduard Strasburger´s Über den Bau und die Verrichtungen der Leitungsbahnen in den Pflanzen (On construction and function of the conduits in plants) written in 1891. Strasburger, who is mostly remembered for his outstanding contributions to plant cytology, gave an encyclopedic compilation of old and recent work done on pathways and mechanisms of water transport in the plant body. As Sir Francis Darwin stated in 1896: "It is difficult to praise too highly this great effort of Strasburger´s".

Strasburger himself was an adherent of the school of physics and provided some strikingly efficient demonstrations of water being lifted to considerable heights without any involvement of living cells (Figure 1). He showed that woody stems with their lower end immersed in concentrated solutions of copper sulfate or picric acid and severed by a cut made below the surface of the liquid, will readily suck the solution up. Immediately upon contact, the poisonous fluid kills all living cells in its way, but the copper or the acid arrive in the transpiring leaves and kill them as well. The uptake of the solution and the loss of water from the dead leaves may continue for several weeks, and new solutions of a different color may be lifted in a dead stem.

http://www.plantphys.net/images/ch04/we0401a.png


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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #84 on: 10/05/2005 14:39:04 »
We have been through this before, but this is true of the xylem and water will be drawn up a dead tree, but not of the Phloem which is a complex bi-directional sugar and mineral transport system, not the downwards only pipe that is needed for your theories.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #85 on: 10/05/2005 15:28:38 »
There goes your precious leaf generated tension theory.

All of the cells were killed by the acid / copper sulphate solution. All of them! That means the phloem and the xylem. Yet the flow to the leaves remained functional for 3 weeks. Explain that using the cohesion theory!

There goes any connection whatsoever with living plant cells.

All we are left with is some dead inanimate tubular conduits and pits, “sounds like my tubular experiment more than some wonderful mystical suction from dead leaves”? Add some salts at the top of the tree from the decay / breakdown of the leaves, which will alone generate flow according to my theory.

 I know, I have repeated the experiments with liquidised leaves, tea, milk, urine, etc etc. anything denser than water will initiate this flow and the sooner scientists accept that this flow will occur wherever there is a denser solution above a less dense solution the better.

But to hide this thread from the view of people who are interested in physics and fluid dynamics is nothing short of censorship at best!

The truth of the matter is that this new paradigm looks a damned site more likely than anything that has gone before it! And it has already generated a lot of interest.

Are you afraid that it is becoming too popular? And feel the need to suppress it  by confining it to the cells, behind bars so to speak?

This theory is innocent and should not spend one night in the cells!
Andrew K Fletcher  


"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
« Last Edit: 10/05/2005 15:41:54 by Andrew K Fletcher »
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #86 on: 10/05/2005 15:39:07 »
Andrew

With physics it is always a good idea to keep an eye on where the energy is going,
So just answer me this...
98% of the water that goes up the tree is evaporated, so for every 100kg of water going up the tree at the most 2kg of water comes back down.

lifting 100kg of water 100m takes 10 000J

dropping 3kg of water and sugar 100m releases 300J

where does the other 9700J come from?
 

Offline rosy

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Re: How do Trees Really lift Water to their Leaves?
« Reply #87 on: 10/05/2005 15:51:05 »
quote:
But to hide this thread from the view of people who are interested in physics and fluid dynamics is nothing short of censorship at best!

...and *that* is nothing short of paranoia at best.
It is a slightly odd feature of this site that it doesn't have a more general "plants" section but no-one doubts that your results physically occured in your tube experiments, that the weight of the solution is causing the flow.
Anyone interested in how plants work will be interested in cells too, and will be looking at that part of the website too.
If you're that worried you could always post a new thread solely about the physics of your demos... maybe even with a little more explanation of how your ideas accord with things like the principle of conservation of energy (unless you're ruling that out too? I haven't worked that out).
You could even explain the principles by which (on about page one) you reckon you can get water at the top of your loop given that the water in it must be a negative pressure.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #88 on: 10/05/2005 16:22:31 »
The beauty of this simple experiment is that it shows circulation of fluids through conduits. Inside the dead tree that is still lifting water and evaporating it from the leaves, all we have is the knowledge that circulation must be taking place because the leaves are still  transpiring moisture and that has to have come from the soil!

If only 1 gram of denser saline solution was returned in either a xylem or a phloem, this circulation would effortlessly lift / circulate many thousands of times its own volume, providing the tree with ample water to continue its evaporation. However, when the tree has been killed, the production of sugars will come to an end eventually and the minerals will find their way down to the lower part of the tree, ending the circulation at the end of the three week period, leaving only heat generated density changes to continue.

The cohesion theory needs to show this erroneous one-way lift of water. My theory requires the water to circulate. If you could set up the experiment you would see how important this is.

1 gram triggers this flow, never mind 2kgs.

Yesterday evening at 11.25pm, I set up an experiment with a 4 metre length of tube, open at both ends and filled with boiled water. At the time I am posting this, no cavitation has occurred, meaning that the water inside the tube requires only that the tubes be held in a vertical position, as they would predominantly be if they were inside a tree. This alone raises a serious question about your energy analogy.

So unless you are referring to the 10 000J as the suns energy, it does not relate to the experiments. 1 gram can cause many thousands of times its own volume to circulate vertically, and this will inevitably cause horizontal or diagonal circulation, depending on the route with the least resistance.

All that is needed is to show how the water circulates. Note the word circulates, as it is important. The term lift relates to your current line of thinking.


quote:
Originally posted by daveshorts

Andrew

With physics it is always a good idea to keep an eye on where the energy is going,
So just answer me this...
98% of the water that goes up the tree is evaporated, so for every 100kg of water going up the tree at the most 2kg of water comes back down.

lifting 100kg of water 100m takes 10 000J


dropping 3kg of water and sugar 100m releases 300J

where does the other 9700J come from?



"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #89 on: 10/05/2005 16:28:50 »
Rosy, you don't have to be a genius to see that the cells forum is hardly visited by anyone, wereas the general science section is visited by most of the people who use the forum.

Nevertheless I thank you for seeing the logic in the experiments and for not doubting their validity as viable repeatable experiments.

Andrew

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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #90 on: 10/05/2005 16:33:56 »
You are right you can cause lots of water to circulate without using much saline in your experiment, this is because you are not increasing the average height of water in the system - the energy required to lift the water on the up side is exactly the same as the energy released  dropping the water on the down side. You are just moving it from one bottle at the bottom to the other.  This means that all the weight of the saline has to do is overcome friction.

However a tree is not circulating at least 98% of the water!!!

98% of the water going up the xylem leaves from the leaves (you quoted this figure several pages ago) it isn't coming back down so the energy to lift it up is not released by water going down the tree.

So where is this 97J/kg coming from in your model?
 

Offline NakedScientist

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Re: How do Trees Really lift Water to their Leaves?
« Reply #91 on: 10/05/2005 17:10:43 »
Oh, alright then, I'll move it to Physics instead !

TNS
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #92 on: 10/05/2005 17:29:02 »
I have tried to convince you that the diameter or even the number of upward flowing water beeds does not equate to the volume of water or the diameter of tube in the return flow.

I have stated before, that you can have a larger bore tube on one side of the loop and a smaller bore tube on the other side, the balance is equal and the water is held in suspension.

I have tested this using a twin tube on one side and a single tube on the other, at 3 metres height. The balance on both sides is equal with no net flow either way. Only when a tiny amount of salt solution is added to the single tube side, or for that matter the double tube side does the circulation begin.

At the top of the tree the bore sizes change as the branches taper of to twigs, meaning that the return flow will inevitably be in a smaller tube to start with. As the water evaporates from the fine bore tubes, it is left with the return flow being directed down tubes of a similar size, or if that pathway cause back pressure, the flow will find a new route, causing more tubes to form.

So if you can picture a large volume of water being drawn through smaller tubes and that this reduced but denser volume flowing down through the smaller tube is sufficient to generate the pull of higher volumes of less dense solution in larger or even multiple tubes rising up, it simply does not require the energy input you are presuming it needs to flow. All I keep asking is that you repeat the experiments, or let me repeat the experiments and you will see exactly what I am talking about.

Hand the experiment over to the people at your homepage and ask them to form an opinion about whether this is relevant to plants and trees. I have not yet failed to convince all that have witnessed the experiments.

You also mention about the heights that fluids have to continuously attain, if I am not mistaken by your post. There is another force at play in this experiment, and that is the increased head of water generated in the rising side of the tube. The Brixham experiment dos not exactly reflect the fact that all of the multi-conduits inside a trees structure are inside one big conduit, and the roots are not exactly open as my tubes are.
Enclosing my experiment inside a tube filled with water would produce a net increase in the head of water, showing how trees can grow higher than the original water levels. It also shows to perfection how dew exudes from grass in the morning and how water exudes from a cut stem, previously believed to be some mystical force generated by the roots, known as root pressure.


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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #93 on: 10/05/2005 17:46:18 »
Chris,

Why does it have to be moved? We have agreed that it crosses the boundaries of Biology, Physics and even Chemistry.
It also crosses the medical and physiology boundaries, geology and palaeontology and even evolutionary boundaries.
If this is not general science then what is?

I would love to have a chat with you on the phone, if this is possible let me know. My number is: 01803524117
Andrew
 

Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #94 on: 10/05/2005 17:56:10 »
If you connect a large tube and a small tube together in teh way you suggest it will work, however water is not being gained or lost from the tubes, so the flow in litres/second will be the same in the big tube as the small tube, the velocity in the big tube will just be slower.

The down bottle fills up by the same amount as the up bottle empties doesn't it?

If the up pipe is 12mm and the down pipe is 6mm, to test this colour the saline red and the water in the up bottle blue you will see that when the red drops all the way down the pipe the blue will lift up about 1/4 as far as the saline drops. so you have lifted 4times as much water 1/4 of the distance as the saline dropped - so overall water has just moved from one bottle to another.

A tree lifts water to it's leaves ans 98% of it evaporates, your model lifts water to the top then all of it comes back down. The two are not equivalent at all!!!


I am the people at my homepage so that won't really help - and at no point have I argued with the results of your experiments just your interpretations of them, so doing the experiments wouldn't necessarily help, although I would be happy to come and see yours at some point when I am in Devon and not too busy.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #95 on: 10/05/2005 18:08:57 »
NO David, if the tree is killed and the flow continues for another three weeks, it definately is not the tree that is lifting the water!

But you are missing my point with regards to this flow in a tree. The very nature of the trees construction enables transpiration to take place. I would not even know where to start trying to make an artificial tree. But killing the tree and the water / sap inside it is still flowing for 3 weeks is a vertual artificial tree.

If saline solution were to be some how introduced at the top of the tree once it has stopped flowing after the three weeks, we should observe fresh circulation due to the initiation of said flow and return system. Obiously, we would have to refil the tree to its previous levels of water to replace the losses from the falling levels of water inside the tree.

Give me a date, and I will drive to Cambridge and give a demonstration for all to see.

Andrew



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Offline moth

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Re: How do Trees Really lift Water to their Leaves?
« Reply #96 on: 11/05/2005 10:07:08 »
Andrew, I too met you in Brixham with CHaOS (yes we are ganging up on you ;-), so have had some time to think about your idea.

I believe your experiment works, but i mostly disagree with the conclusions you draw from it and the arguments you use to explain it. I also disagree with your dismissal of the other princples involved.

I imagine that there could exist a tree which transpired very little, but instead used your salt-siphon principle to create a vertical conveyor-belt of water to transfer chemicals between its roots and leaves. Dilute solution would rise up one set of tubes while an equal flow of denser, more concentrated solution would fall down another set of tubes, and at either end living cells could maintain the concentration difference by extracting solutes at the bottom and injecting them at the top. I'm sure this does some violence to a biologist's understanding of trees (and i know it doesn't match mine), but as a physicist i am happy with it in principle.

I consider it an interesting and clever idea, but don't believe it has much to do with how real trees actually work. The key flaw is that the salt-siphon cannot explain transpiration. Your idea requires almost equal up and down flows, while transpiration means that (vastly) more water flows up than down.

You rubbish root pressure, saying that if it worked then jets of water would squirt from the roots of felled trees. I don't think that follows. Water is almost incompressable at the pressures we are discussing, so it is entirely possible for the roots to contain water at a significant pressure without causing them to squirt when cut as the water would need to expand only a tiny amount to completely relieve the pressure. What i would expect as evidence for the existence of root pressure is for roots to gently ooze liquid for some time after they are cut. Indeed this is what i have observed: when I have cut limbs from trees during the spring and summer i have often seen liquid flow from around the edges of the wounds (where the current year's phloem and xylem are). To be clear, i'm not prepared to swear root pressure is all there is, but i don't find you dismissal of it convincing.

Osmosis is a complex, subtle and powerful phenomenon. It is quite possible that the widespread explanations of it are faulty, and yet osmosis really happens. I found this paper which discusses the many ways of analysing osmosis: newbielink:http://arxiv.org/abs/physics/0305011 [nonactive]

Your recent answers to Dave's questions about the energy budget refer to differing sizes for up and down tubes. This is strikingly similar to a perpetual motion machine I invented when i was 14. It works like this: construct a siphon from a short fat tube and a long thin tube connected at the top. Place the bottom ends in buckets and fill the system with water. As there is a greater weight of water in the fat tube it will pull water up the thin tube, so transfering water from the lower bucket to the higher one. I hope you can see why this doesn't work, and why your replies don't answer Dave's question.

I don't buy your dismissal of the 'conected water column powered by evaporation at the top' idea, but i want to do some calculations before i post on that subject.

You seem to attack most things simply by saying they are implausible. This is not an argument that holds any weight with me. If you want any acceptance of your idea you will have to start making sense in terms of accepted scientific priciples. Our discussion in the E=mc^2 thread suggests that you are not prepared to do this, but i still hope you will. It is as if we are speaking different languages. I have not managed to learn yours from your postings here, so if we are to be able to communicate you must learn mine.

I would be interested in seeing your experiment, but even if it works exactly as you say it does it wont change my opinions of your explanation of it. Mostly i am just curious about the details of your method, and would rather see it for my self than through your discription.

I suggest this thread remain in General Science - the subject is a mix of biology and physics with a hint of chemistry. The discussion has lacked biologists so far and could certainly benefit from their input, but while Dave and I continue to examine the physical basis of Andrew's theory it would be out of place in the Biology section.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #97 on: 11/05/2005 10:53:07 »
One other point I would like to add is that if the Brixham experiment was inside the trunk /sleeve of a tree, it would be able to support the column to much greater heights, furthermore it would add another interesting force to the equation. It would generate an increase in the head of the dilute solution, picture an inverted U tube with clean water on one side and a small amount of concentrated solution in the other, the water levels will change, pushing the dilute solution up and out of the opposing tube, and the resting place of each side of the fluids level will be much higher in the dilute side than the side with the salt added.

This is the mechanism for water to exude from a cut stem and this is why it has been erroneously attributed to root pressure!

I look forward very much to showing you the experiments.

Andrew


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Offline daveshorts

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Re: How do Trees Really lift Water to their Leaves?
« Reply #98 on: 11/05/2005 11:34:23 »
I believe that if you cut a stem right off (at the right time of the year) it will exude sap - I know a dandelion does, wouldn't this preclude your explanation as you have just cut off your inverted U tube?

I don't think that root pressure allways explains the whole pressures involved (apart from anything else if it is being powered by osmosis it is an energy intensive process and would waste a lot of sugar if it were used it for transpiration), but it certainly exists.
 

Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #99 on: 11/05/2005 11:52:06 »
Ill be AFK for a few days, will catch up when I come back home.

RE: Tubular differences, try to see that the increase in tension of the fluids pulling the sap through ever smaller tubes, forcing the excess out through the leaves as transpired pure water. The forces generated by the falling solutes in other areas of the tree are more than enough to cause water to be drawn up and evaporated.

Remember also. When I first came up with this theory all those years ago, I did not have the Brixham Experiment to show the principles. In fact the experiment was built to show the forces and flow rates generated by this liquid pulley system \ Not siphon effect.

At the time, I also believed in the thirty three feet limit, but gave the experiment a go anyway, believing that the cohesive force in the experiment would easily exceed the adhesive forces in the capped tube experiment previously used to determine the height that water can be drawn up with a pump, as in Galileo's problem at The Grand Duke of Tuskany's Palace.

As I carefully drew the water beyond the 33 feet limit, I knew in my heart that this was and is a very important part of fluid mechanics and fitted beautifully with my hypothesis. When I added the salt to the one side to see if it would draw water from one bottle to the other, over the thirty three feet limit, I was ecstatic to say the least.

My colleague,  Adrian VanZweden, who was top in Physics at his University In Holland and had worked for many years as an water engineer at South West Water, sat on a step with his hands on his head shaking it, saying this is not possible, This cannot be happening, after previously stating that the experiments could not work according to current Physics literature. Adrian and I have conducted the experiments many times, and he was there also at the Brixham experiment, along with John Russell, pictured in the news article with my wife Jude.

Moth, thank you also for seeing the logic in leaving the thread in the General Science section.

Sincere regards

Andrew
 

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Re: How do Trees Really lift Water to their Leaves?
« Reply #99 on: 11/05/2005 11:52:06 »

 

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