How do Trees Really lift Water to their Leaves?

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #200 on: 29/10/2008 09:26:07 »
BTW, Andrew, a competent Engineer would know how any black box he uses will work because he couldn't risk it failing to perform as he expects when tested. You have been using a black box all the time but have no idea what is going on inside. You're no Engineer. There goes another group of workers who you have denigrated.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #201 on: 29/10/2008 10:23:47 »
Sophie You are forgetting one very important observation which you must consider.

The flow from one vessel to another both at ground level therefore at = pressures, yet clearly visible in the Brixham video as being far superior to the flow rates observed in trees. Adhesion as you state is responsible for sticking the water to the inside of the tube, Cohesion evident in the flow from one vessel to another is clearly not relying on adhesion. Once the bead of water is severed by cavitations the water flows from the tube ends and empties it if they are removed from the water at ground level. Adhesion clearly is not as important for suspending the water. When the water bead collapses and the tube endings remain in the water at ground level. The water falls back to the 10 metre level. The space above it being vacuum as was shown in the original problem of the pump by Galileo and co.

Your last post appears to be stating the obvious again regarding adhesion in the tube and this is where I fear we may have had crossed lines. I was relating to your capped end tube all along. I see no point in stating the obvious. One could go on to argue that the cord used to raise the rope exerts a constricting pressure and the downward pulling on the cord over a pulley block exerts an upward motion to the tube and the airÖÖ. pressure exerts a positive pressure outside the tube and on the water in the reservoirís at ground level. Why complicate a simple successful experiment when all this is obvious to the observer? This may be required for a patent application, but surely not for a simple tubular experiment?

Nevertheless. I melted the end of a 130 CM length of the same tubing used in the Brixham experiment, Blew down so the molten end formed a bulb as you suggested, filled it with tap water making sure no bubble were present, held it up and noted that water did not flow out of the end as expected. Applied a very moderate centrifugal force by holding the closed end and gently rotating it to find with little to no force water flowed from the end as expected.

Next: Repeated the same with previously boiled / degassed water and found that there may have been slight (if any) increase in resistance to the bead of water failing. The tube was at no point rotated the tube differently to force the bead of water to break and the tension could not have been any where close to that observed in the Brixham Experiment at 24 meters. One could argue that the air flowing passed the open end increased the tension on the water inside the tube, but trust me on this, I did the experiment to see for myself if adhesion could support the water in a 6 mil bore nylon tube, not to make it fail but to try to make it work.

Again I must state that there is little to no point repeating the same experiment with a longer length of tubing as the force exerted by the column of suspended water will easily cause the water to be pulled from the tube.

It may interest you to know that when the U tube is performed lower than 10 metres and the ends of the tubes are removed from the water, the water flows out and will not remain in the tubes. I look forward very much to your comment on this observation too.
 
Andrew K Fletcher

Albert Einstein
One had to cram all this stuff into one's mind for the examinations, whether one liked it or not. This coercion had such a deterring effect on me that, after I had passed the final examination, I found the consideration of any scientific problems distasteful to me for an entire year.
« Last Edit: 29/10/2008 10:45:28 by Andrew K Fletcher »
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #202 on: 29/10/2008 10:44:40 »
If you were a thinker instead of a sheep you would engage your brain before opening your mouth. Again you attack me. It is I that has trashed the bull that you have been teaching not you that has trashed my experiments. Worth remembering that don't you think?
Any moron can keep churning out the same written literature without questioning it.

Albert Einstein
Humiliation and mental oppression by ignorant and selfish teachers wreak havoc in the youthful mind that can never be undone and often exert a baleful influence in later life.


BTW, Andrew, a competent Engineer would know how any black box he uses will work because he couldn't risk it failing to perform as he expects when tested. You have been using a black box all the time but have no idea what is going on inside. You're no Engineer. There goes another group of workers who you have denigrated.

Albert Einstein
Education is what remains after one has forgotten everything he learned in school.
« Last Edit: 29/10/2008 10:49:00 by Andrew K Fletcher »
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #203 on: 29/10/2008 11:34:20 »
I have just read your last outburst, which I will ignore.
I was about to post the following reply when I read it.You will notice that I am trying to be constructive.:

Quote
I see no point in stating the obvious
It may appear obvious to you but nothing is 'just obvious' in Science. If you have an incomplete model in your mind of what is going on then you can't explain this.
The reason that you don't explain it must be because you can't.
You are doing to me exactly what you claim that Science teaching is doing to children.
What you are saying. effectively, is "You just have to accept this obvious fact". If it isn't obvious to me then are you going to shout at me as if I were a naughty / thick child or are you going to try to help me with my obvious misconception?
Which should I do if I were trying to get an idea across to a child who didn't get what I was saying?

Some comments:
Quote
Cohesion evident in the flow from one vessel to another is clearly not relying on adhesion
Do you have a cohesion meter and an adhesion meter to tell you this? What justification for this statement? (we are not dealing with a chain or wire made up of a solid substance)

Quote
I was relating to your capped end tube all along.
But I was, 'all along', asking you to draw a distinction between the two situations - yours and mine.

Quote
One could go on to argue that the cord used to raise the rope exerts a constricting pressure

Precisely. The weight of the rope will pull down on the pulley. The rope is a solid and, despite being able to distort a little (become a bit narrower and longer), the 'constricting pressure' is balanced by the molecular forces which are there - the properties of a solid. If you were to hang a length of chewing gum (a very plastic substance) over the pulley the gum would stretch and get thinner because it would flow. Water flows, too, but more easily, so you would expect the same if you didn't provide the tube outside it which could provide some extra forces.

Quote
I melted the end of a 130 CM length of the same tubing used in the Brixham experiment
Well, you did try.  It worked as expected.  During your whirling phase, it is not surprising that water flowed out - the tube could flex and bubbles would have been admitted into the bottom, allowing air in.  Also, the opening at the bottom would not have been horizontal so there would have been a pressure differential (Hydrostatic - not atmospheric) across the inverted surface of water - that would start a water flow - you can see this happen with an inverted bottle of water, too where the water flows (gloops)  out quicker if the bottle is not exactly vertical. If you had suspended the tube motionless and tapped the sides I would expect the same sort of thing to happen. It was worthwhile trying but you were not in a position to see what was actually going on inside the tube. If you were to try the same thing with your U tube, I think the water would fly out even quicker with such rough handling (see the last comment on this post for the reason).

Quote
Again I must state that there is little to no point repeating the same experiment with a longer length of tubing as the force exerted by the column of suspended water will easily cause the water to be pulled from the tube.
That presupposes your original ideas are correct and that the inside of the top of the tube was as smooth as the top of the looped U tube.
There are many problems associated with implementing the closed tube experiment and I can see how the continuous loop provides both a much smoother surface and a better chance of eliminating bubbles. That is a practical and not a fundamental difference between the two experiments. Very easy to draw the wrong conclusions about the actual mechanisms at work.

Quote
It may interest you to know that when the U tube is performed lower than 10 metres and the ends of the tubes are removed from the water, the water flows out and will not remain in the tubes
That is precisely what I should have expected to happen. It's an unstable situation. Unless the two arms of the tube are precisely the same length then there will be a hydrostatic pressure differential across them causing water to flow. Once it has started, the difference increases further and the flow will increase.  If the tubes are kept in small reservoirs, such as in your original videos, the levels will self-adjust. This, of course, explains why, when you added a more dense liquid to one side, the levels started to change; the hydrostatic pressures are not equal. If you were to raise the side with the salt in, you would find a new position in which the flow would be zero. (Until diffusion of the salt solution into the freshwater side started to change things).

To sum up, I can see nothing in your last post which proves or justifies further you explanations. Half way through you, yet again, beg the whole question by making the assumption all over again.
All you have described fits in perfectly with conventional theory.
I think I have identified the crux of our differences  enough times. Are you really not capable of answering my one small point about the way the molecules must be working 'at the top' IN BOTH CASES?


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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #204 on: 29/10/2008 12:33:10 »
It was Einstein not me that wrote those quotes attacking his own experience in the education system.

To sum up:

1 the experiments at Brixham were roughly handled over a relatively prolonged period of time, due to the person at the top of the cliff lowering the tube rather than holding it steady, yet the bead of water remained intact as shown in the unedited actual time footage. More experiments have been done many times and recorded showing this bead of water to be a lot more robust than you are imagining it to be. I knew you would argue that gently rotating the smaller capped tube would not represent the longer tube. But surely you can comprehend how much tension there is in a u tube suspended to 78 feet = two columns of water pulling on each other. The tension BTW should be the same throughout the water column, because as you state each moecule must act on it's neighbouring molecules. A further experiment was conducted at a greater height than 24 metres. The water inside the tube was observed to boil without heat.






I have just read your last outburst, which I will ignore.
I was about to post the following reply when I read it.You will notice that I am trying to be constructive.:

Quote
I see no point in stating the obvious
It may appear obvious to you but nothing is 'just obvious' in Science. If you have an incomplete model in your mind of what is going on then you can't explain this.
The reason that you don't explain it must be because you can't.
You are doing to me exactly what you claim that Science teaching is doing to children.
What you are saying. effectively, is "You just have to accept this obvious fact". If it isn't obvious to me then are you going to shout at me as if I were a naughty / thick child or are you going to try to help me with my obvious misconception?
Which should I do if I were trying to get an idea across to a child who didn't get what I was saying?

Some comments:
Quote
Cohesion evident in the flow from one vessel to another is clearly not relying on adhesion
Do you have a cohesion meter and an adhesion meter to tell you this? What justification for this statement? (we are not dealing with a chain or wire made up of a solid substance)

Quote
I was relating to your capped end tube all along.
But I was, 'all along', asking you to draw a distinction between the two situations - yours and mine.

Quote
One could go on to argue that the cord used to raise the rope exerts a constricting pressure

Precisely. The weight of the rope will pull down on the pulley. The rope is a solid and, despite being able to distort a little (become a bit narrower and longer), the 'constricting pressure' is balanced by the molecular forces which are there - the properties of a solid. If you were to hang a length of chewing gum (a very plastic substance) over the pulley the gum would stretch and get thinner because it would flow. Water flows, too, but more easily, so you would expect the same if you didn't provide the tube outside it which could provide some extra forces.

Quote
I melted the end of a 130 CM length of the same tubing used in the Brixham experiment
Well, you did try.  It worked as expected.  During your whirling phase, it is not surprising that water flowed out - the tube could flex and bubbles would have been admitted into the bottom, allowing air in.  Also, the opening at the bottom would not have been horizontal so there would have been a pressure differential (Hydrostatic - not atmospheric) across the inverted surface of water - that would start a water flow - you can see this happen with an inverted bottle of water, too where the water flows (gloops)  out quicker if the bottle is not exactly vertical. If you had suspended the tube motionless and tapped the sides I would expect the same sort of thing to happen. It was worthwhile trying but you were not in a position to see what was actually going on inside the tube. If you were to try the same thing with your U tube, I think the water would fly out even quicker with such rough handling (see the last comment on this post for the reason).

Quote
Again I must state that there is little to no point repeating the same experiment with a longer length of tubing as the force exerted by the column of suspended water will easily cause the water to be pulled from the tube.
That presupposes your original ideas are correct and that the inside of the top of the tube was as smooth as the top of the looped U tube.
There are many problems associated with implementing the closed tube experiment and I can see how the continuous loop provides both a much smoother surface and a better chance of eliminating bubbles. That is a practical and not a fundamental difference between the two experiments. Very easy to draw the wrong conclusions about the actual mechanisms at work.

Quote
It may interest you to know that when the U tube is performed lower than 10 metres and the ends of the tubes are removed from the water, the water flows out and will not remain in the tubes
That is precisely what I should have expected to happen. It's an unstable situation. Unless the two arms of the tube are precisely the same length then there will be a hydrostatic pressure differential across them causing water to flow. Once it has started, the difference increases further and the flow will increase.  If the tubes are kept in small reservoirs, such as in your original videos, the levels will self-adjust. This, of course, explains why, when you added a more dense liquid to one side, the levels started to change; the hydrostatic pressures are not equal. If you were to raise the side with the salt in, you would find a new position in which the flow would be zero. (Until diffusion of the salt solution into the freshwater side started to change things).

To sum up, I can see nothing in your last post which proves or justifies further you explanations. Half way through you, yet again, beg the whole question by making the assumption all over again.
All you have described fits in perfectly with conventional theory.
I think I have identified the crux of our differences  enough times. Are you really not capable of answering my one small point about the way the molecules must be working 'at the top' IN BOTH CASES?

By the way, bubbles being admited into the bottom of the whiling tube will not alter the adhesion at the top of the tube with a mere two rotations will it? How do those bubbles travel from the opend end to the top of the capped tube while it is generating centrifugal force towards the ends of the pipe? What really happens in the tube is that the weight of the water exerts too much force on the molecules stuck to the top of your domed capped tube ending.


« Last Edit: 29/10/2008 12:47:54 by Andrew K Fletcher »
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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Offline neilep

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Re: How do Trees Really lift Water to their Leaves?
« Reply #205 on: 29/10/2008 13:16:19 »
Glad to see everyone is being so cordial, courteous and gracious   [;)] [;D]

Men are the same as women, just inside out !

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #206 on: 29/10/2008 14:13:24 »
Thank you Neil!
Andrew:
You need to refomat your post. The quote includes some of your own words at the bottom, I think.

Your original post did not discuss how the space at the top had formed. Are you suggesting that the gap at the top of the tube was a vacuum? In which case , when you removed your 'extra force', the water would have gone back up to the top (as Galileo et al have found). If the gap remained, then it was full of air. This air can only have got there as bubbles from the bottom, out of solution or via a leak in your 'sealed end.  It must have come from somewhere.
Quote
The tension BTW should be the same throughout the water column,
Just not true. If you take a chain (of finite mass) and hang it up. The tension between the bottom two links is equal to the weight of the bottom link. The tension between the top two links is equal to the weight of the whole chain - less the top link weight.  How can the bottom link 'know' how many links there are above it? If there were more  tension acting on the bottom link than its weight then  it would move upwards. (Newton's First Law of Motion applies, as always)

How can you pontificate about this topic if you make a simple error like that? Some serious rethinking is needed, I fear.

I wouldn't mind betting that Einstein made a point of learning, thoroughly,  all about Newtonian Physics before he started leading off that it was inadequate or wrong. He never treated anything as 'obvious'.
I can sympathise with him regarding his view that his education was lacking. HE, as it proved later, was actually very clever  and was probably frustrated at his teachers not even approaching him in ability and he never did suffer from an understated ego.  Andrew - you are no Einstein.
I am just a humble proponent of a system which seems to work very well and is very consistent (except at its esoteric edges) - because the people who have constructed it are are lot more clever than you or I. But I do my best to avoid skating around difficult points - unlike you, who still refuse to address one pivotal question which I need not repeat, surely.

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Offline JimBob

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Re: How do Trees Really lift Water to their Leaves?
« Reply #207 on: 29/10/2008 15:07:25 »
Y
Glad to see everyone is being so cordial, courteous and gracious   [;)] [;D]


And we could always determine the outcome of this by, oh, say broadswords. No light sabers - this is an age of enlightenment.

The mind is like a parachute. It works best when open.  -- A. Einstein

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #208 on: 29/10/2008 15:16:39 »
Keyboards at dawn, I think. Or any other time in the 24hr cycle.

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #209 on: 29/10/2008 15:16:54 »
Can you feel the tension?

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paul.fr

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Re: How do Trees Really lift Water to their Leaves?
« Reply #210 on: 29/10/2008 15:54:37 »
Glad to see everyone is being so cordial, courteous and gracious   [;)] [;D]



Well im only reading this topic for the insults. Although i do find in upsetting when two grown men (ok, one may or may not be a woman..oh and i discount BC because he is a chemist) yadda yadda yadda...

Lokk, just get on with slagging eachother off, i have popcorn ready you know!

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #211 on: 29/10/2008 16:07:13 »
All I want is an answer and all will be clear folks.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #212 on: 29/10/2008 16:12:14 »
You know Sophie, you must be correct. I must be a complete idiot for showing you that water can be placed under tension when you refuted it. But where does that leave you?

Tension is brewing
Of course every molecule in the columns is under tension. Each and every single one of them. The downward pull from gravity on the water must also have an effect on the walls of the stiff nylon tubing, but not sufficient to account for the water springing up the tube when the ends are removed from the water container at ground level.

Add a pinch of salt to one side and water is drawn up under tension. Not because of pressure changes either. 1 grain of salt will trigger this flow! How can you account for this in pressure changes?  Surely this flow is responsible for generating the pressures and not the other way around. What drives the circulation before a heart forms? Gravity is a good starting place! This is not the same as a siphon. I keep trying to explain that there is a huge difference between a siphon flow and a density flow. Thought experiment. Coloured salt solution added to upward flow side of a siphon in sufficient quantity to generate a density flow in the upward flowing side. Here we have a downward density flow in the same side as an upward flowing siphon flow. Seen it done it!

Do I have a laboratory and unlimited funds to go with my cohesion and adhesion measuring device? Perhaps an entire university behind me even as you do?

You avoid most of my questions and ignore most of my answers and concentrate on what is happening to the molecules inside the tube? I do not understand what you want from me other than for me to become a verbal punch bag that is?
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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Offline Bored chemist

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Re: How do Trees Really lift Water to their Leaves?
« Reply #213 on: 29/10/2008 19:16:13 »
Fascinating, but I'd sooner see you answer Sophie's question.
 
Please disregard all previous signatures.

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #214 on: 29/10/2008 19:31:02 »
I did try to deal with all the issues in your last post. Did I avoid any of them?
I am surprised that you don't think the behaviour of molecules is relevant to the way substances behave. To my mind that is a crucial issue upon which all other things in this topic must hinge. Any explanation just has to include the molecular consideration or we are back in the middle ages.

Have you given some thought to my chewing gum idea? Is that not relevant to the situation with water?

One grain of salt will cause a flow? Of course it will. The solution around it is more dense and will drop through the fresh water, albeit quite slowly. It would be a real surprise if it stayed there or went up.

What is 'surely' about the flow generating the pressure? You can measure a pressure difference with out needing any flow. As I suggested, try raising the salty side and you will get a balance point (equalise the pressure difference) with no flow. Why do you muddle up cause and effect so often? What do you suppose started the flow in the first place? Everything needs energy from somewhere to make it happen. Where does the energy come from for your flow if not from the salt having been lifted, by some means or another and gaining Gravitational Potential.

How about my question regarding the space that you saw above the column of water? Did it stay there? Was it air? How did it get there?  There is an interesting practical question here.

The fact that an open-bottomed U tube doesn't stay full is very well explained in terms of small pressure difference. You have not replied to my general comments about your latest trials. I think they were mostly good-willed comments??

What is a "density flow"? It is not a term in common use.

I fully believe you saw what you saw but the girl saw the tooth fairy's money too. Was she right to believe in the tooth fairy? She could have found the real cause by the appropriate experiment - staying awake all night- or asking someone who knows.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #215 on: 31/10/2008 09:27:02 »
Ok let me ask you to state what you know about the Brixham experiment.
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #216 on: 31/10/2008 18:27:50 »
There's no point in going into too much detail but what it has actually 'proved', rather than what you have 'seen in it' is as follows. Water, under reduced pressure, will not boil instantly. It exhibits cohesion and adhesion. The forces of adhesion and cohesion, as a pair, sustain a siphon process when you increase the density of the liquid on one side of a U tube.
That, in itself, makes the Brixham Experiment well worthwhile having been done. It is a surprising result but reasonable with hindsight. There is, elsewhere, work which shows and measures the 'dynamic (temporary) tensile strength' of water under negative pressures.
You have not yet answered my objections /  questions regarding the results of your recent single tube experiment. They are the same questions that I would have asked myself if I had done the work myself - I was not trying to give you a hard time about it.

Your explanation and the undefined terms you use (such as density flow,  for instance) are not the only ones possible.

My explanation uses conventional and well tested ideas and tries to use as much of the existing knowledge as possible.

If you really had a convincing package of explanations for the phenomenon then you should be able to reconcile your ideas with such fundamental questions as mine regarding how the molecules behave at the top. You have still not managed to answer this in any depth. You just cannot ignore the problem or dismiss it as obvious - it isn't.

Remember - you are the one who is introducing a new idea and rejecting the established one. The burden of proof lies with you. That is, if you want it to be taken seriously.
Are you still not prepared to discuss the molecular situation and the nature of the forces all through the water?
Rather than just getting upset that your ideas haven't been accepted without argument, you need to substantiate them better.

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Offline _Stefan_

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Re: How do Trees Really lift Water to their Leaves?
« Reply #217 on: 01/11/2008 01:52:50 »
I'd really like to see Andrew answer whether the column of water would remain intact if the tube were removed.
Stefan
"No testimony is sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavors to establish." -David Hume

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #218 on: 01/11/2008 10:08:36 »
SophieCentaur.

Thank you for your reply

However, you have not stated anything I have not already stated other than mentioning the adhesion of water to the inside of the tube, which to me at least was obvious. In other posts, I have mentioned this, as soft walled tubes collapse when tension is applied. Again it is obvious that the water is still stuck to the tube and that the tension is pulling on those molecules which in turn pull on the tube. One could also argue that the adhesion inside the tube, coupled with the applied tension lowers the pressure inside a soft-walled tube to the point where atmospheric pressure pushes the tube in and that it does so because air molecules are in contact with the outside of the tube. I have also stated time and time again that the water resists the tendency to boil over the 10 metre mark, even adding when you take the experiment considerably higher than 24 metres the water boils as would expect it to. Even stating that adhesion in certain previous experiments was the reason for failure when cohesion in an unbroken column of water succeeds. Somewhere, I have also stated about my friend Adrian Van Sweden, a brilliant physicist, and former water engineer from South West Water sat on a step with his hands covering his face saying this is not possible after witnessing my experiments. He added water cannot exist in a negative pressure environment but here it is. Why have I not been taught this?

Remember what I said about working with a siphon over 10 metres
As you lower one vessel it stretches the water on the side that you are lowering causing cavitation and eventual failure. It does not induce a flow from one vessel to another. This is worth considering because had it ever have done so it would have been in the literature by now, as many engineers, plumbers, pipe fitters, boilermakers, fire fighters, irrigation experts, have all entertained this problem.

The spinning Z tube where water is injected at the centre of the Z causes the water to cavitate when sufficient tension has been applied. As water passes over the elbows of the Z tube rotating clockwise it induces tension that can be measured accurately.

Hindsight is an easy word to say after an event, but a difficult word to comprehend before an event.   

The 6 mil bore tubing capped and swung around gently caused the water to empty from the tube without any deliberate whipping or flexing in the tube. I wanted this experiment to succeed by the way as I have to admit there was a chance it could have, albeit slim. Even using degassed, pre-boiled water it made little to no difference. The spinning Z tube on the other hand confirms the huge tensile strength of water and as the Z tube is of a very small size, adhesion provides the stability of the injected water preventing it from necking. In a soft tube this necking is illustrated. In a solid walled tube not so obvious.

This is why IBT is important for varicose veins shrinking and oedema being drawn from the surrounding tissue back into the circulation. The density flow through the arteries induces the tension in the veins causing the fluids to pull the veins in as the pressure is relieved that causes them to bulge.

Studying trees on the other hand is more difficult due to the rigidity of the tubes, except in the stages of tube production just beneath the bark. This is where pressures and adhesion count in the liquids before they become solid tubes. The pressure in the liquid caused by the gravity induced downward flow resulting from solute free evaporation at the leaf enables a flow without tubes under a positive pressure, essential for maintaining the inside diameter of the forming tubular cells. And lignifications strengthen the walls around the flow by attracting and hanging on to the molecules of resin suspended in the sap. So here lies the answer to yours and Stefanís valid question about whether a flow can exist without tubes. In fact circulation in all creatures begins long before any tubes are formed.   

Andrew K Fletcher
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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #219 on: 01/11/2008 10:52:12 »
Why do you bother to include comments about trees and IBT in your reply?
The fact that you can observe certain effects does not justify your explanations of one simple effect. You just cloud the issue.

You will notice a scattering of posts from other members amongst our dialogue. They all include the same basic question as mine regarding the basics of what happens at the surfaces of the tubes, in molecular terms.

I assure you that we are not all 'ganging up' on you about this. You should take it as a sign that the question really does need answering.

You keep doing exactly what you complain that teachers of Science do. You expect us to believe in something and refuse to look outside your particular model. Just consider, for a moment, that you could be wrong in this particular aspect of what you (think you) understand.

You went to the trouble of experimenting with the single tube - that's good. But why don't you reply to my queries about experimental details? I am a pretty experienced experimenter and my points are valid.

Please stop repeating your anecdotes and answer the main question. I will then stop asking it.
« Last Edit: 01/11/2008 17:17:40 by sophiecentaur »

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Re: How do Trees Really lift Water to their Leaves?
« Reply #220 on: 01/11/2008 18:33:06 »
If you have something to add about molecular behaviour in tubes then spit it out man. You appear not to be asking a question but to be implying you know the answer to your own question so get on with it.

I mentioned the tubular growth in trees because I was asked how this flow system could be there without tubes. The reference to soft walled tubes was required to explain how a flow could cause tubes to form with the flow maintained inside them once they have formed.

Perhaps you would like to explain why water inside the tube does not conform to the phase diagram of water to people viewing this thread too?
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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #221 on: 01/11/2008 21:44:53 »
I'll spit it out, 'man'.

If the water is to stay in contact with the top of your U tube or my single tube, the molecules at the very top must be attracted to the top or they will move away from it. They must behave in exactly the same way. How can they tell whether they are at the top of your tube or at the top of my tube? They have no brains and no eyes. The same forces must be acting on them. Can you suggest why they should behave any differently? Are you suggesting that no force is needed in your U tube where a force is needed in my tube?
The answer to this question must contain no mention of trees or sick people or how bad Science teaching is.

We can't get anywhere near your flow system until you justify  something far more fundamental.

You won't answer my perfectly understandable questions about your latest experiment. Why not? Does it threaten your integrity or don't you understand them?

I haven't mentioned your Xylem tubes for ages. I am not interested in your tubes until we get the first bit sorted out. Is it really too hard for you?

I have to explain nothing - you are the one who is making the claims.
I just need some valid justifications for your new opinion - not paranoia.

This is a Science Forum. Why don't you treat it as such? Please apply some logic.
 
« Last Edit: 01/11/2008 21:46:47 by sophiecentaur »

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #222 on: 01/11/2008 23:27:07 »
Andrew
I suggest you try reading through this article and some of the references in it.
www.lps.ens.fr/~caupin/fichiersPDF/CRPhys_2006_7_1000-1017.pdf

You may find it instructive. If you can read it and understand what it says, it will tell you a lot of what you need to know about trees, the conditions under which tension in water becomes relevant and how cavitation occurs.
Basically, some of your ideas work for trees but they won't work for firemen.
Before anyone thinks they have found something new, it is a good idea for them to trawl through the literature.
Your 'revolutionary' ideas are very fragmented and seem to contain a lot of half-understood notions. Your very worthwhile experiment on the cliffs has been a bit wasted because of your interpretation of the results.

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Re: How do Trees Really lift Water to their Leaves?
« Reply #223 on: 02/11/2008 16:39:04 »
Sophie, before I read the link provided, I have gone back over the Siphon thread to try to understand what your problem with the Brixham Experiment is. Which incidentally is far from wasted! The results from the many experiments conducted, some of which I have not included in this forum, produce the results that they were intended to produce. The problem with being a lateral thinker is one tends to processes problems as a whole, and not segmented so that each can be understood.

You say water would move away from the inside of the tube. As water is already compressed by gravity, where is it going to move to? It can't move down the tube because it is linked to other molecules balancing the downward pull equally on the opposite side of the U tube. It canít flow out because this would require cavitations to form, again to break the cohesive bond. It canít flow up because of gravity, It canít collapse the tube because the wall is strong enough to resist the decompression. If molecules move away from the wall, more molecules must replace it because each molecule acts upon its neighbours. Cavitations will inevitably combine to form larger vapour bubbles and this will cause the water columns to fall back to the level at which atmospheric pressure can sustain them @ 10 metre mark, so although the molecules cannot determine which experiment they are in, we must take into account at all times that each molecule is linked to another inside the tube, so deciding the fate or purpose of a single molecule or groups of molecules that are part of a huge volume of molecules in the same experiment is a little difficult to consider to say the least.

I have now read the lengthy paper you linked to and found it to be a report on the progress of science relating to cohesion, adhesion, tension, surface tension and cavitations in water and other various liquids, dealing with ancient science and more modern science approaches to the problems of cavitations in water. Most of which was familiar to myself, and some of which I have included in the two threads, including the spinning tubes, stretched water, etc.  Nevertheless, I have not seen this paper before and it does include at least two experiments that I have not heard of before. So thank you for posting the link and for taking the time to look at the experiments.

The terminology I use may not always be in accordance with writing a convincing academic argument and I agree with you on this at least, but if you compare what I have stated to what you have provided in the PDF file we are not far from the mark at all.

Throughout the paper you provided, there is no mention of timescales for cavitations to develop in degassed water, although nucleation is mentioned in relation to impurities in water, I suspect the main seed points are indeed between the water/tube interface. I cannot see another experiment that could show timescales for cavitations other than inside a living plant or tree. The U tube gives us prolonged stability of water under negative pressure and tension allowing us to see cavitations developing through the opaque tubing. There must be clearer tubing produced that could allow us to look more clearly at the forming cavitations.

Deionised water previously boiled will enable the Brixham experiment to easily exceed the 24 metre mark and give us prolonged stability.

I thought the inclusion of particles entering the experiment to cause the nucleation was interesting also. And had not considered this.



The following history event shows how a tiny bubble of gas causes the Huygens experiment, (similar to yours), fails from the paper you provided the link to.


4.1. Pull
A straightforward way to stretch a liquid is to pull directly on it. The pull can be generated by the own weight of the liquid. This is how Huygens made the first experimental observation of negative pressure in 1662, and published his work in 1672 [49]. A tube open at one end is filled with water purged of air, and inverted over a water bath. If the air above the bath is evacuated, water remains suspended in the inverted tube. The pressure at the top of the water column of height h is Psat − ρgh, where ρ is water density, and g the acceleration of gravity. As soon as a bubble of air is injected in the tube, it rises and the water column falls. This experiment was presented to the Royal Society of England, and repeated on water and mercury by several physicists, including the famous Hooke and Boyle,
who reached −0.2 MPa in mercury. The phenomenon was later re-discovered by Donny [23] and Reynolds [47,48]. Details are given by Kell [50]. As Reynolds used a 2.3 m-long tube wetted with water before being filled with mercury, he obtained the most negative pressure for water with this method: −0.3 MPa [48]. Hayward, who thought that the method was invented by Donny [23], re-used it to study different liquids [51]. Another way to pull a liquid is to mechanically increase its volume with a bellow for instance. One can also put the liquid under pressure before warming it up, and eventually releasing the pressure. These techniques have been widely used to make bubble chambers where high energy particles are detected because they trigger cavitation in the metastable liquid (see Ref. [53] for a review); however, volatile liquids with a low surface tension were preferred to water. But the bellow method was used by Hayward to design a water pump with a suction lift of 17 m, corresponding
to a pressure of −0.17 MPa [52]; much higher liquid columns exist in tall trees (see Section 7.1).
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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #224 on: 02/11/2008 19:46:25 »
Saying that you are thinking laterally doesn't prove that you are right.
You have brought up many issues which are very interesting and have changed my views about the behaviour of water under negative pressure.
BUT  the model which is in your head is still flawed. It cannot hope to describe what is going on if you say, for instance, that you have negative pressure up there but gravity is still Pushing the water against the tube. How is that consistent?
A truly valid model has to deal with all the little nitpicking details which you choose to ignore. You cannot be so selective about what you do and don't accept about convention without total rigour. Your explanations for what happens in your experiment just would not extend to other situations - even to a single tube. Your brief experiment was not detailed enough. You won't even answer my reasonable queries about it. You are too confident of your model to submit it to scrutiny. Do you not see how important it is to make clear what was in the void at the top of the tube? If it is air then there must be a leak. If there is water vapor or a vacuum then the void would vanish when pressure increases again. What happened? Can you remember? It is NOT irrelevant if your interest is truly scientific. There is nothing glamorous about pressing on and ignoring these queries and objections.
I despair of ever getting answers to these and the other questions which I and others have asked. If you want to be groundbreaking you have to be totally thorough.

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Re: How do Trees Really lift Water to their Leaves?
« Reply #225 on: 02/11/2008 22:20:56 »
The void vanishes each time when the tube is lowered back to ground level due to the compression of the atmosphere. Sorry for not including this as did not realise this was what you were asking. A direct question always helps.
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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #226 on: 03/11/2008 10:27:00 »
I'm sorry; were the following extracts not direct enough?

Quote from my post of  29 Oct:
Your original post did not discuss how the space at the top had formed. Are you suggesting that the gap at the top of the tube was a vacuum? In which case , when you removed your 'extra force', the water would have gone back up to the top (as Galileo et al have found). If the gap remained, then it was full of air. This air can only have got there as bubbles from the bottom, out of solution or via a leak in your 'sealed end.  It must have come from somewhere.
Quote from my post of 29 Oct (later):
How about my question regarding the space that you saw above the column of water? Did it stay there? Was it air? How did it get there?  There is an interesting practical question here.


My comments referred to the single tube - to avoid confusion. It was clearly in that context.  Your last answer seems to refer to the high level U tube experiment. You see, I think that you really don't want the single tube to work because it would go against your theory. However, if you can clear up this problem then I would take that back, of course.

Did you also not read my direct statement that you were wrong when you wrote the tension is the same throughout the column? That needs an explanation from you, I think.

I also made a direct comment, earlier, using chewing gum as a metaphor for water at the top of a tube. No comment about that, either; was it irrelevant?

I just saw this statement from you whilst I was revisiting past posts:
"Stop thinking of water as water, start thinking of it as a solid."
Were you joking?  Can that be taken seriously? At what point do we have to treat a bowl of water as a bowl of solid? You could freeze it - but I don't think that's what you meant. When does a water molecule, at room temperature, know how to treat its neighbours differently? When is it part of a solid and when is it part of a liquid?
 

Can I recap on your recent single tube experiment? As I understand it you used a single tube, less than 10m long and whirled it around to simulate a longer tube. You noticed cavitation at the top whilst it was revolving and this cavitation disappeared when you stopped.  IS this correct?
What was the actual length and at what speed did you rotate the tube? How did you see the effects?

I'm not sure but I got the impression that you repeated this with a U tube and the water ran out. This is what you'd expect because of asymmetry.

Last comment, for now: Could you please define what Density Flow means? I can't find it anywhere apart from in your writings.

« Last Edit: 03/11/2008 12:32:32 by sophiecentaur »

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #227 on: 03/11/2008 13:56:20 »
Sorry but I just spotted this in your last post.
Quote
You say water would move away from the inside of the tube. As water is already compressed by gravity, where is it going to move to? It can't move down the tube because it is linked to other molecules balancing the downward pull equally on the opposite side of the U tube. It canít flow out because this would require cavitations to form, again to break the cohesive bond.

I was 'indoctrinated' into mechanics when at School, along with Newton's Laws. Forces add vectorially (would you not agree?).
At the top of the tube (when it is >10m, to keep the diagram simple), we have cohesive forces, acting towards all the nearby water molecules and the weight of the molecule, acting downwards. Nothing is being 'compressed by gravity', the molecule is just being pulled downwards by its own weight. The other molecules are all pulling away from it. These all produce a resultant force which acts away from the wall. Unless this force is canceled by an equal and opposite adhesion force, the molecule will move away from the wall. It can only stay where it is when the forces are balanced. Can you possibly disagree with that?
When this molecule moves away, it, of course, would let all the other molecules move - they are under tension- and they can flow out of the bottom of the tube as long as there is an unbalance in the forces.
Unless you have adhesion - not just a bit, but of equal value to balance the other forces involved - the bead will part company with the wall. If you don't agree with that then you need to go away and learn the basics of how forces work.
Needless to say, this applies to any shape of container, be it U tube, or an upside down Poseidon in the well known film.
You don't have to pick me up on this example because, in that case, the adhesive forces are not enough AND cavitation will occur. But that isn't the point of the argument.  The point is that, if the column stays up, it must involve both 'strong' adhesion and a delay in cavitation.

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Re: How do Trees Really lift Water to their Leaves?
« Reply #228 on: 03/11/2008 14:22:12 »
A density flow is what it says it is. Density flow is the movement of a denser solution acted upon by gravity from an elevated point towards the ground, which in turn induces a return flow. So it is a flow and a return flow system. This simple density flow is what drives a non-pumped domestic hot water system. The heat source alters the density of the water causing it to rise. The copper coil inside the hot water tank causes the water to become denser as it transfers the heat from the tube to the water inside the tank, causing it to flow back down to the source of heat, where the circulation process continues. A self circulation heating system operates by the force created by the density difference between the hot and cold fluid.



 A video on Youtube shows the flow through a clear glass vase. Watching it you could easily miss the point that for a downward flow of denser solutes, there must be a return flow to the surface, water molecules will always move to where molecules have moved from, just the same as they would when molecules move away from the inside of the pipe.

Your post asking about the void related to the single capped tube. I said that water flowed out of the tube when the experiment was performed, so could not have returned to fill up the void.

Damn, just realised a mistake with that capped experiment.  Maybe if we have a single capped end of tube and the open end in a vessel rather than being exposed to the air will assist the water to resist the centrifugal force longer. This would require affixing the bottle in some way to the end of the tube to prevent it from flying off.

There was no point swinging round a U tube in the same way because water would not remain in it. Again however if the both ends of the tubes were in a container and it was swung round it may prove interesting.

The chewing gum analogy necking, I did mention that as one molecule moves away from the wall of the tube another will replace it providing of course that the cavitation is not sufficient to cause the bead of water to fail.

Popping out so will get back to this on return
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Re: How do Trees Really lift Water to their Leaves?
« Reply #229 on: 03/11/2008 15:51:28 »
OK on the term 'density flow'. In a hot water (convection) system, the energy comes in the form of thermal energy. To keep it going you need to keep the energy flow by maintaining a temperature difference.

Quote
The heat source alters the density of the water causing it to rise.
That's schoolboy howler number one. Water will not rise unless it is pushed. There are no strings pulling it up. What pushes it? It is the more dense cold water which displaces it.
Andrew, if you are not thorough with well known matters like that then how can you hope to make any worthwhile advances in Science?

Quote
Your post asking about the void related to the single capped tube. I said that water flowed out of the tube when the experiment was performed, so could not have returned to fill up the void.
So what was in the space over the water? If there was a permanent 'void' at the top then it must have been AIR! That means either a leak into the top or bubbles floating up from the bottom. I wish you could explain exactly what happened. It certainly casts doubt on the experiment.

Quote
water molecules will always move to where molecules have moved from,
Here's another cause and effect problem. The more dense solution displaces the less dense. Why? Because the more dense is pulled down harder than the less dense and pushes it out of the way. When you add the solution, you increase the overall pressure at the bottom of the container.
How does that apply to molecules as they move from the surface when water evaporates? You imply that you would get 'strings of water' leaping up into the air.

Quote
I did mention that as one molecule moves away from the wall of the tube another will replace it
And where does this molecule come from?  Does there have to be a flow? Do you inject them into the top? Get your model sorted out; it really is dodgy. Or are you only considering the situation when you have enough gum flow to allow the molecules to come from the other side? You are implying that there is a minimum speed at which this would work. Any slower and the gum will 'neck'. My diagram applies to the gum just the same as the water. Are you arguing with the basics of force vectors?
« Last Edit: 03/11/2008 19:03:32 by sophiecentaur »

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #230 on: 03/11/2008 19:04:15 »
Sophie. Why do you mock?  In my density flow tube, we clearly see one side of a soft walled tube pulled in and one side bulging out. We clearly see water leaving one vessel into another and the same goes for a closed loop of tubing.

Your statement that water will not rise unless it is pushed may need a little edit, else you will have the entire cohesion tension fringe of science after you. They state as one molecule leaves a leaf (scuse the pun)  another is pulled behind it to replace it and this believe it or not is largely accepted science and all science has to offer with regards to the ascent of sap in tall trees, perhaps you should take a leaf out of their books?

And yes there are strings pulling on the fluid, strings of particles linked together just like RD suggested in his chain analogy. Using food colouring we can see how the flow occurs, we do not see a uniform full bore flow but a considerable amount of turbulence as some of the coloured salt solution is flowing down the return flow side of the inverted U tube which rolls in a circular motion as salt free water is drawn past it. Fascinating to watch by the way and well worth studying. It shows how molecules pull on each other too. What do you suggest might be pushing water out of the top of a giant sequoia towering well over a hundred metres? Root pressure? Magic?

The central heating system shown was merely to illustrate that a downward flow will result in a return flow. But more to the point to coin one of your phrases; ĎHow do molecules of water know they are in a U tube, a central heating system, a single upright capped tube, a tree or indeed a human í? Why should we expect that an upward flow or downward flow inside a tree will not produce a return flow? Schoolboy stuff this, but before the education system gets in their way!

And let us not forget your meniscus example where adhesion is pulling the water up at the edges, or have you forgotten this argument already?

I have not said there is a minimum flow at which this will work. I have said that we have an excellent opportunity to study cavitation in this model due to itís stability and this is the first time the speed at which cavitation takes place in water suspended in a meta-stable state. There is another thing I would like to add. It would appear that cohesion is taking place in the upward flowing leg of the suspended tube. I may certainly have missed some cavitations forming in the 24 meterís of water filled tubing on the down flow side, but suspect that the saline flows, which represents the phloem in trees is repairing the voids? Or is the positive pressure evident by the outflow from the bottle at ground level sufficient to prevent them from occurring in the down flow side? Even the bench top model produces cavitations over time.

The rotating tube failed because the open end allowed all the water to come out of the tube emptying it completely so unable verify if there was void in it or not.

To conduct a 24 meter single tube experiment would be a pain in the back side. Have you ever tried filling a six mil bore tube with water and making sure there are no bubbles in it, that is capped at one end? I have, and will not be attempting to fill a 24 meter one.


OK on the term 'density flow'. In a hot water (convection) system, the energy comes in the form of thermal energy. To keep it going you need to keep the energy flow by maintaining a temperature difference.

Quote
The heat source alters the density of the water causing it to rise.
That's schoolboy howler number one. Water will not rise unless it is pushed. There are no strings pulling it up. What pushes it? It is the more dense cold water which displaces it.
Andrew, if you are not thorough with well known matters like that then how can you hope to make any worthwhile advances in Science?

Quote
Your post asking about the void related to the single capped tube. I said that water flowed out of the tube when the experiment was performed, so could not have returned to fill up the void.
So what was in the space over the water? If there was a permanent 'void' at the top then it must have been AIR! That means either a leak into the top or bubbles floating up from the bottom. I wish you could explain exactly what happened. It certainly casts doubt on the experiment.

Quote
water molecules will always move to where molecules have moved from,
Here's another cause and effect problem. The more dense solution displaces the less dense. Why? Because the more dense is pulled down harder than the less dense and pushes it out of the way. When you add the solution, you increase the overall pressure at the bottom of the container.
How does that apply to molecules as they move from the surface when water evaporates? You imply that you would get 'strings of water' leaping up into the air.

The moecule I mentioned was a water molecule, so presumably it would have come from the water inside the tube.

Quote
I did mention that as one molecule moves away from the wall of the tube another will replace it
And where does this molecule come from?  Does ther have to be a flow? Do you inject them into the top? Get your model sorted out; it really is dodgy. Or are you only considering the situation when you have enough gum flow to allow the molecules to come from the other side? You are implying that there is a minimum speed at which this would work. Any slower and the gum will 'neck'. My diagram applies to the gum just the same as the water. Are you arguing with the basics of force vectors?
« Last Edit: 03/11/2008 19:08:01 by Andrew K Fletcher »
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Re: How do Trees Really lift Water to their Leaves?
« Reply #231 on: 03/11/2008 19:48:35 »
We have a U tube filled with degassed water to add stability. Adhesion must apply to the entire length of wetted inside of the strong nylon tubing. I agree so far at least. The molecules are all happily stuck fast to the tube. Still with you here so far. It can be as strong as you like and I am entirely happy with this and indeed it is perfectly logical and obvious. In fact I would go so far as to say the water stuck to the inside of the tube forms itís own water tube. This provides an environment for water to flow either way in this suspended tube providing it is below 10 meters. If we pull both ends out of the water below 10 meters water flows out one side and the other side is emptied out of same side as it is pulled around by the out-flowing water, just like a syringe draws water from a vessel. So the water molecules involved in adhesion do not prevent free movement through the tube, but do prevent the water inside from necking, as in your chewing gum analogy. Above the 10 meter mark we do not have gravity pushing down and the atmosphere, which in turn pushes down on the water in the open vessel that in turn forces water up the tube or in this case assists it to stay there below the vacuum / void point.

So there is an attraction to the wall of the tube and molecules should align to the tube to form adhesion by using the opposite polarity to the nylon tube molecules-whether this is relevant at the moment Iím not sure. Nevertheless water can flow out either side of the tube, so adhesion does not prevent the outflow in the U tube. So cohesion must be the main stabilising force. What I hope I have said here is that although the water is stuck to the inside of the tube, water can move freely it does not arrest the water column so cannot be responsible for holding the open ended water filled tubes that we have exposed to the atmosphere by removing them from the water. So why does the water not flow out? What explanation other than the elasticity of water which is related directly to the cohesion of water will account for the water rapidly rising up the exposed tubes forming a level a considerable distance from the ends of the tubes?   
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Re: How do Trees Really lift Water to their Leaves?
« Reply #232 on: 03/11/2008 21:03:32 »
Andrew. You are in your own little Science Cloud Cuckoo Land, I'm afraid. Three is just no point in continuing with this. You are not even aware of how much Science you are rejecting.
Over and out.

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Re: How do Trees Really lift Water to their Leaves?
« Reply #233 on: 03/11/2008 23:08:44 »
You can't have it both ways either the water is stuck to the tube or it is not. But only the molecules closest to the tube count. The rest of the water does not come into contact with the tube so relies on cohesion and is therefore free to flow either way but not without having an affect on the molecules next to those that are flowing. The question is really why don't you repeat the damned experiments and draw your own informed conclusions, rather than summising what you think must be happening?

By the way cloud Cuckoo land is way above 24 meteres vertically. And unlike the cohesion tension theory you et al adhere to, it does not suck.
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Re: How do Trees Really lift Water to their Leaves?
« Reply #234 on: 05/11/2008 11:02:03 »
I'm sorry but your last post, as they all tend to, consists of a non-logical, circular argument. I just can't cope with it any more.
Thoroughly examine what you have said.

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Re: How do Trees Really lift Water to their Leaves?
« Reply #235 on: 05/11/2008 15:42:32 »
Sophie I don't know how to put it into words that you can understand. Trying to say that even if the molecules are stuck to the tube it does not prevent freeflow from the tube as observed below 10 meters, if that makes sense. So adhesion while important is simply not as important as the cohesion in water molecules which is why the Brixham experiment works. My work is logical and has convinced a lot of professional people at professor level. 
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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #236 on: 05/11/2008 19:22:47 »
Of course the water can flow - it's a liquid. But what you ignore constantly is that, if there is no adhesion then it will leave the wall (it will flow away from the wall). You talk about water 'flowing in' to to make up the space but where will it come from? From which side? It will merely form a neck because each of your down tubes pull it in different directions. You are surely not suggesting that there is enough velocity in the flow to keep it moving, are you. It doesn't have to flow to work, in any case - you say.
Don't you see the very basic inconsistency in your version of what goes on at the top?
Give it some serious thought.
A rope can be as strong as you like but if you don't tie it on, it comes adrift. The molecules at the interface are the only thing which can keep the water in place up there - if you detach them, the column will pull apart due to necking.
Are you saying that a smooth bore metal tube >10m would work also? It is known to have lower adhesion to water than  water cohesion, remember.
Let's face it, you have assumed that the single tube will not work on the grounds that you believe you have an explanation how the U tube works. That is a totally circular argument and can't prove anything. You are totally locked into this misconception and have given no justification for it.
You have yet to answer a lot of my objections to your basic Science statements - like the tension in the column being the same. Any comments?
There - you've started me off again - blast.
« Last Edit: 05/11/2008 19:27:47 by sophiecentaur »

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #237 on: 06/11/2008 08:58:58 »
I did reply to your question about tension being the same throughout the columns of water on both sides. Tension is applied to every single water molecule. This dragging effect was realised by Professor H.T.Hammel, ever wrote a paper on it relating to how current understanding of osmosis is totally wrong. Dissolved solutes apply the tension as they move from one point to another due to the effects of gravity and in doing so cause the whole of the liquid to move in the direction of flow. One would think that the bead of water breaks because the tension is greater in the area that breaks. But this is not entirely accurate. Cavitations take place along the column of water rather than just at the top. It is the tiny cavitations that join together that eventually cause the columns to separate and the levels to return back to the 10-meter mark.

When I conducted these experiments, I did so because everyone else had assumed there was no point because of historic experiments with water in tubes. Clearly they were wrong. The experiment you keep trying to justify is the very same experiment that has failed for 300 years. Modifying it slightly may as you say improve the possibility of prolonging it before it collapses, and as it is your idea then it is you that should test it. As I have said it is a pain filling a closed loop tube with a liquid. But having thought about this it could prove easy to do with a smaller tube inserted inside the 6 mil tube to push water in under pressure right to the end, withdrawing the inner tube as the water is injected. The tube would need to be relatively stiff to be able to push it right to the closed end of the 6 mil bore 24 meter tube.

The justification I have given to the U tube experiment is that it clearly does work, even when scaled down.

Remember. The U tube experiment was relating to the shape of vessels in nature. Trees do not have tall tubes that flow up to the top and end, they have circular vessels that entertain a circulation, something worth remembering.

A lot of people are reading this thread, would anyone else like to add their thoughts on whether a single capped tube would cause water to remain inside at 24 meters or even above 10 meters? The end of the tube should be globe shaped or rounded and smooth. Are there any schools or colleges interested in performing this experiment in the name of science?
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #238 on: 06/11/2008 14:38:56 »
So you are saying that the force on the bottom link of a hanging chain is the same as that on the top link?
What about the weight of the chain? This is the most elementary mechanics and doesn't need to refer to Prof Hammel or osmosis. That is just a smokescreen.

What you say about tension is merely an unsubstantiated statement - not a reasoned argument. Solutes will tend to fall because they are more dense. A stone will do the same thing in water.

You have no proof that the U tube is any different from the single tube because you have not done a control experiment. Yes, it would be a pain but, without it, you have not proved a difference. You are the one who needs to prove it - not me; those are the rules, I'm afraid. Old ideas are "Innocent until proved guilty."

You can't seem to deal with my 'necking' / adhesion argument and what would happen at the top if it weren't for adhesion so I presume you have no answer.

I would have to decline your kind offer to demonstrate your ideas to a bunch of innocent Schoolkids because your whole methodology is flawed. They could really do without that sort of influence until they are equipped with some logical thinking skills.
"In the name of Science"?? What Science? Science is consistent - or aims to be so. You have introduced an inconsistent idea which is not proven. You just get upset when it is not accepted.
Give me a good, logical, argument which refutes the logic of how the column of water would not stay up there unless stuck to the tube. And would it work in a metal U tube?

We have already accepted that your experiment worked. That is an interesting and surprising result. It's your explanation which is not acceptable because it does not stand the logic test. The one doesn't follow from the other.

And 'scaling down' is not valid because you have not scaled the ambient pressure. Can you argue with that?

Quote
Remember. The U tube experiment was relating to the shape of vessels in nature. Trees do not have tall tubes that flow up to the top and end, they have circular vessels that entertain a circulation, something worth remembering.
Can you repeat that in a way that makes sense, please? Tubes don't flow. Which are the circles? What does "entertain circulation" mean?

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #239 on: 06/11/2008 21:27:34 »
Put another way: The sap that flows in the tree is not on a one way trip to atmospheric liberation, it circulates around the tree evaporating water from it to the atmosphere, just the same as we do not excrete blood unless wounded, a tree does not excrete sap but evaporates solute free water from the sap.
Can see I missed some words from the last post now sorry.

I know this conversation has become heated at time. I just want to say that I am grateful for your thoughts even if at times I appear to be unhappy with some of your less than civil comments. The original explanation for the tubular experiment was written for students at Junior and secondary level in order to introduce the concept of a flow and return mechanism, without clouding it and making it too complicated for them to understand it. I still feel I did a good job regarding this and had no problem convincing both students and teachers with the experimental model and indeed the flow and return argument in trees.

I am beginning to take on board that a more detailed explanation is required for eventual publication, and as you say the need to test a single tube, a metallic tube, a plastic tube filled with mercury etc etc. I am also beginning to understand, thanks to you and others why a simple explanation may prove too problematic for people to grasp the behaviour of stretched fluids without seeing it for themselves, again thank you for enlightening me on how this is interpreted by others.


Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #240 on: 06/11/2008 22:52:37 »
That's OK as far as it goes Andrew.
I see that you are totally convinced that your Science is correct.
It is not 'too problematic' for me to understand what you are saying. It is 'too problematic' for me to accept it. There's a big difference.
As I have said several times. Your experiment show evidence of a phenomenon which is novel but your explanation is just too naive. I don't need to see it for myself. I believe you saw what you saw.
I also believe in well founded Science. Results, in general, agree very well with the established theories.  You, apparently don't understand these theories or you would be looking for an explanation for your phenomenon amongst them, rather than making up your own incomplete one.
Science tries not to be a matter of opinion; we try to base it on rigorous logic. When someone brings up an objection, for instance, based on vectorial addition of forces the objection has to be answered with rigour. You have chosen not to consider how this shows flaws in your explanation. If you explanation were correct, you could explain such an apparent anomaly.
You seem to be leaving this dialogue, assuming that you are, in fact right and ignoring objections.
Please don't have the temerity to object to conventional Science teaching on the grounds that we tell kids to believe things "because we say so". That is just what you have been trying to do -and with far less justification and track record. If a student objects to any of the standard Science I present them with, I am in a position to justify it right up to the wire. I would not dream of belittling them merely on the grounds that they have 'interpreted it' wrong. I will give them a full and rigorous explanation after having worked, if necessary, for a long time to reconcile their ideas.
I see you regard yourself as a heroic figure, battling against the massed ignorance of the Science establishment.In fact you are a Don Quixote, tilting at Scientific Windmills and failing to see what is actually going on around you.
Please try to read some established texts. They cannot all be wrong in every respect so they may just be more right than you are about this topic - if only you could understand what they are really saying.
It's never to late for some independent learning and self education. I do it every day.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #241 on: 07/11/2008 14:04:00 »
Transpiration-Pull http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/X/Xylem.html

In 1895, the Irish plant physiologists H. H. Dixon and J. Joly proposed that water is pulled up the plant by tension (negative pressure) from above.

As we have seen, water is continually being lost from leaves by transpiration. Dixon and Joly believed that the loss of water in the leaves exerts a pull on the water in the xylem ducts and draws more water into the leaf.

But even the best vacuum pump can pull water up to a height of only 34 ft or so. This is because a column of water that high exerts a pressure (~15 lb/in2) just counterbalanced by the pressure of the atmosphere. How can water be drawn to the top of a sequoia (the tallest is 370 feet high)? Taking all factors into account, a pull of at least 270 lb/in2 is probably needed.

The answer to the dilemma lies the cohesion of water molecules; that is the property of water molecules to cling to each through the hydrogen bonds they form.


When water is confined to tubes of very small bore, the force of cohesion between water molecules imparts great strength to the column of water. Tensions as great as 3000 lb/in2 are needed to break the column, about the value needed to break steel wires of the same diameter. In a sense, the cohesion of water molecules gives them the physical properties of solid wires.

Because of the critical role of cohesion, the transpiration-pull theory is also called the cohesion theory.
Some support for the theory

    * If sap in the xylem is under tension, we would expect the column to snap apart if air is introduced into the xylem vessel by puncturing it. This is the case.
    * If the water in all the xylem ducts is under tension, there should be a resulting inward pull (because of adhesion) on the walls of the ducts. This inward pull in the band of sapwood in an actively transpiring tree should, in turn, cause a decrease in the diameter of the trunk.

         * The rattan vine may climb as high as 150 ft on the trees of the tropical rain forest in northeastern Australia to get its foliage into the sun. When the base of a vine is severed while immersed in a basin of water, water continues to be taken up. A vine less than 1 inch in diameter will "drink" water indefinitely at a rate of up to 12 ml/minute.

      If forced to take water from a sealed container, the vine does so without any decrease in rate, even though the resulting vacuum becomes so great that the remaining water begins to boil spontaneously. (The boiling temperature of water decreases as the air pressure over the water decreases, which is why it takes longer to boil an egg in Denver than in New Orleans.)
    * Transpiration-pull enables some trees and shrubs to live in seawater. Seawater is markedly hypertonic to the cytoplasm in the roots of the coastal mangrove, and we might expect water to leave the cells resulting in a loss in turgor and wilting. In fact, the remarkably high tensions (on the order of 500Ė800 lb/in2) in the xylem can pull water into the plant against this osmotic gradient. So mangroves literally desalt seawater to meet their needs.

Problems with the theory

When water is placed under a high vacuum, any dissolved gases come out of solution as bubbles (as we saw above with the rattan vine). This is called cavitation. Any impurities in the water enhance the process. So measurements showing the high tensile strength of water in capillaries require water of high purity ó not the case for sap in the xylem.

So might cavitation break the column of water in the xylem and thus interrupt its flow? Probably not so long as the tension does not greatly exceed 270 lb/in2.

By spinning branches in a centrifuge, it has been shown that water in the xylem avoids cavitation at negative pressures exceeding 225 lb/in2.

Sequoias can successfully lift water 358 ft (109 m) ó which would require a tension of 270 lb/in2.
However, such heights may be approaching the limit for xylem transport. (The tallest tree ever measured, a Douglas fir, was 413 ft. high.) Measurements close to the top of the tallest living sequoia (370 ft high) show that the high tensions needed to get water up there have resulted in:

    * smaller stomatal openings, causing
    * lower concentrations of CO2 in the needles, causing
    * reduced photosynthesis, causing
    * reduced growth (smaller cells and much smaller needles).
« Last Edit: 07/11/2008 15:23:31 by Andrew K Fletcher »
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #242 on: 07/11/2008 15:43:30 »
Facts quoted above, from others, could well be true.
It is your interpretation of them that is flawed.
Merely posting yards of interesting botanical information does not detract from the fact that your Science is wrong.
As usual, you have no answers to the more searching questions.
Give my regards to Sancho Panza.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #243 on: 07/11/2008 17:08:50 »
Whatever
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #244 on: 07/11/2008 23:20:51 »
Interestingly, nowhere in your recent long post do you quote anyone denying the effects of adhesion. Nor do you quote anyone even hinting at your U tube theory.
It's just a re run of the previous stuff about the cohesion in water being very high, on occasions. A bit pointless as I have already agreed that the evidence for cohesion is compelling.
It's your personal interpretation that needs explaining and justifying.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #245 on: 08/11/2008 09:13:11 »
1.  No tree to my knowledge has a cap on the top.
2.   Circulation in a tree flows predominantly down in the phloem from source to sink. Source being leaves, sink being lower than the leaves.
3.   Evaporation from the leaf cannot take place without a change in density in the sap that flows through the leaves. It is bad science to ignore this fact!
4.   The model we are debating while interesting is merely an experiment that was designed to show the power of a flow and return system that benefits from gravity, not to reflect the perfect anatomy of a tree.
5.   I have never denied adhesion is important. The fact that I never mentioned it by name, but did mention it by including that a soft walled tube necks as the tension is applied, based on observations with other experiments using soft walled tubes, and further mentioning it in the varicose veins study again a soft walled tube behaving in exactly the same way as my experiments is not the bad science you purport it to be. I have said that adhesion relies on cohesion but cohesion does not rely on adhesion, including that even when water is stuck to the side of a water filled conduit, it does not arrest the flow of water through the conduit. Yet in a single upright tube capped at the top this is what will happen and water inside the tube will be pulling down against the top of the rounded capped tube. Adhesion inside the vertical single tube will enable cohesion to be pulling inwards and downwards. Adhesion is not therefore a force, the force is the body of water on the molecular bonding between the water / tubular interface.
6.   And what if? What if I jump through your hoop, conduct your experiment and prove it one way or another? What have I accomplished? Who is going to listen? Does this mean it will become accepted?
7.   Or does it mean that you et al will find yet another reason to continue to believe in the leaf sucking cohesion tension impossibility of the first degree?  Come on here, play devils advocate for an hour or so and see through their smoke and mirrors theory. Leaves cannot suck water up a tree, no matter what spin is put on the theory it is still completely and utterly flawed.

The longer last post did provide you with evidence towards answering your many questions. It relates to the strength of cohesion, includes adhesion in exactly the same way I included my mention in the necking of tubes, It includes the vine experiment showing water boiling at ground level due to the tension applied in the stem, proving that tension occurs throughout the column of water as I had said it would do. And observed it doing as tiny vapour cavitations formed along the length of suspended tube, and go back into the water when the tube is lowered.

It mentions also the spinning / centrifuging of branches to test the cohesion which reflects the tubular experiment I swung round carefully. Although this needs to be done again with a water filled bottle on the end of it to produce a compared tension. Remember the tube used will easily withstand the crushing force.

I do not see many people rushing forward to defend the existing theory. Many thousands of people have read this thread now. Why do you think this is so? And finally the required tension of a giant sequoia at 270 pounds per square inch. Impressive tension that. If it is in place someone should have measured it by now?


Ulrich Zimmerman.
The Cohesion Theory considers plant xylem as a 'vulnerable pipeline' isolated from the osmotically connected tissue cells, phloem and mycorrhizas living in symbiosis with plant roots. It is believed that water is pulled exclusively by transpiration-induced negative pressure gradients of several megapascals through continuous water columns from the roots to the foliage. Water under such negative pressures is extremely unstable, particularly given the hydrophobicity of the inner xylem walls and sap composition (lipids, proteins, mucopolysaccharides, etc.) that prevents the development of stable negative pressures larger than about −1 MPa. However, many plant physiologists still view the Cohesion Theory as the absolute and universal truth because clever wording from the proponents of this theory has concealed the recent breakdown of the Scholander pressure bomb (and other indirect methods) as qualified tools for measuring negative pressures in transpiring plants. Here we show that the arguments of the proponents of the Cohesion Theory are completely misleading. We further present an enormous bulk of evidence supporting the view that Ė depending on the species and ecophysiological context Ė many other forces, additional to low tensions, can be involved in water ascent and that water can be lifted by a series of watergates (like ships in staircase locks). http://www3.interscience.wiley.com/journal/118760238/abstract?CRETRY=1&SRETRY=0
I have asked Ulrich if he would like to take a look at this thread and add a comment.
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #246 on: 08/11/2008 09:46:41 »
In case you hadn't noticed, the reason I keep asking the same question is because you have not answered it yet.
You have just replied with more acres of stuff from other people and with second hand arguments which don't deal with the issue.
My question is, and has always been, to you personally.
Like a cabinet minister under tight interviewing, you have still not answered it. I have no strong opinions about the stuff you have just written about. I just want to know, in terms of the actual science, how you can still insist on the difference between your U tube, which you have tried and my single tube, which you haven't tried.
Not one of your references deal with that.
Your replies would only need to be a couple of paragraphs long if you were to stick to the issue.

Yes, there have been thousands of visits to this and the 'siphon' thread. The only recent contributions, however, have asked you to answer my question. You still haven't.

Perhaps an honest reply would be that you don't understand enough of it to explain the phenomenon thoroughly. There would be no shame in that.

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #247 on: 08/11/2008 11:23:31 »
Your experiment idea is a test of adhesion, and yes I do understand why you feel this may be strong enough to support the water. But this experiment has been conducted my many people over many years using many different materials, all of who have failed just like the great philosophers of science did over 300 years ago. If it were to succeed what then? Would this change my own experiment one bit? Not a chance, because as I have said and will say again the experiment performed as it was expected to perform and water was observed to flow around it from one vessel to another. The fact that you have a problem with what goes on at the molecular level inside a U tube compared to the inside of a capped end tube is fascinating but hardly going to destroy my own observations whichever way it goes is it?

You keep trying to throw a protective shield around students steering them from what you see as heretical science. But then fail to address the flaws in the accepted science.

Adhesion inside the tube is an obvious stabilising force preventing the water from pealing away from the walls of the tube. The downward force of the column of water pulls on the water molecules in the opposite side of the loop of tubing, which in turn balances out the opposing force enabling the water to become stretched by the weight of the two columns of water. The water inside your capped tube can only be stretched to the point that the water is able to stick to the capped end of the tube.  We are talking about 6 mil bore tubing here, not some micro-bore capillary tubing.

I have not tested the experiment with metal tubing, and do not have access to a 48 meter length of unblemished metal tubing do you know where one could be found? Remember soldered joints will provide nucleation sites so canít be used.

You have failed to answer my questions on paragraphs six and seven. I would like you to answer them if you feel you can. Is there going to be an opened door at the end of it and if so can I have it in writing please.
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with

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lyner

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Re: How do Trees Really lift Water to their Leaves?
« Reply #248 on: 08/11/2008 19:02:47 »
Quote
Your experiment idea is a test of adhesion, and yes I do understand why you feel this may be strong enough to support the water.

"MAY BE"??? I am saying, with better logic than any single one of your own 'original' ideas, that the adhesion has to be equal or greater than cohesion for your U tube or a single tube to work. If you can't understand my reasoned argument for that then that is your problem.

Quote
You keep trying to throw a protective shield around students steering them from what you see as heretical science. But then fail to address the flaws in the accepted science.
The problem is that your 'Science' is not even complete enough to be heretical.
I would protect them from what you have said so far in the same way that I would urge them to take care when reading adverts for snake oil and lunatic political parties.

Yes, I would say that any theory which ignores the simplest bit of vectorial force addition was nonsense. You do not even realise that what you are saying fails in this respect. You are implying that
"Forces Add Vectorially Except at the Top of a U Tube. In this situation we can ignore that particular bit of Science". 
Is that  supposed to be serious Science?
Describing the adhesion as a 'stabilising force' is to show that you don't understand the whole basis of vector addition. Why not use the proper terminology - which keeps bridges and planes up in the air and allows people to do Physics, Engineering and Chemistry with great success. This is not new Science and it is really not open to debate - certainly not by someone who seems not even to understand it. (Do you understand the 'triangle of forces' and what it implies in this context?)


Paras 6 and 7: I would fully expect the single tube to behave the same as the U tube but, as you say, it is more difficult to implement. It is you who claim that it wouldn't work on grounds which just demonstrate that you don't understand the basics.

You can buy long rolls of annealed copper tubing (10 mm microbore) in very long lengths. You would find it difficult to do the same experiment, though. I guess you would have to detect the amount of water suspended in it by weighing it. Adhesion between water and metals being what it is, I should expect the 10m limit would apply, so you could prove it one way or another with 21m of tube.
Smoke and mirrors? Can you show in a rigorous way how any aspect of modern Science is just Smoke and Mirrors? This is another of your Windmills.
Where do you get your ideas about the Science establishment. You put me in mind of Jude the Obscure, who was rejected by the Establishment in the Distant University City because he had tried to educate himself and had actually GOT IT WRONG. He was the only one who was surprised at what happened.
Give a Scientist, who is worthy of the name, a good reason to think that an existing theory is wrong and  he will bust a gut trying to PROVE it is wrong. He won't rant and rave that the system is flawed and that everyone is being horrible to him. He will scrutinise the new idea and try, in an informed way, to get the right answer.
 Clearly, you think your education in Science gave you a bad deal; that's sad but, unlike after a war, it is the losers who try to write the history. Mine certainly gave me a very good deal and I learned a lot throughout my life; it continues. What I did learn at a very early age is that if you can't answer a question you admit it and ask for help.

Quote
The fact that you have a problem with what goes on at the molecular level inside a U tube compared to the inside of a capped end tube is fascinating but hardly going to destroy my own observations whichever way it goes is it?
Do you actually read what I have written?
My idea does not attempt to destroy your observations - it successfully destroys your INTERPRETATION of them. Can you find, anywhere in this or the Siphon thread, a comment of mine which casts doubt on your observations?
Do you really want to ignore what happens at the molecular level and how the most basic bit of mechanics applies? It's a bit too rigorous and hard-fact for you, perhaps.

What you are basically saying is that you are right because you say so and the whole of Science is out to get you and your teachers were rubbish.
That's an opinion but proving the Science is a bit more involved than that.
« Last Edit: 09/11/2008 10:56:14 by sophiecentaur »

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Offline Andrew K Fletcher

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Re: How do Trees Really lift Water to their Leaves?
« Reply #249 on: 10/11/2008 09:14:42 »
Ive found a supplier of 50 meter micro-bore copper tubing, cost £88.62 including VAT.
http://www.mytub.co.uk/product_information.php?product=309455

Maybe your school might be interested in testing both models? I can supply the school with the plastic pipe for free.

RE Smoke and Mirrors and Snake Oil Salesmen. First of all Proper snake oil from the water snake has some very interesting properties. The problem arose when Westerners jumped on the bandwagon selling inferior products that used the success of the original oils to market their own oils. Either way someone gets paid. I get paid nothing for this research. So the innuendo you implied is unwarranted.

On BBC Radio 2 this morning a Professor was talking about new Statins, based on speculative trials, he was deliberately trying to increase the market share for what he implied was a new wonder drug. It allegedly reduces the risk of stroke and heart attacks in people who do not have a problem with stroke or heart attacks. His company has identified that the entire human race should be medicated with this new wonder drug and the National Health should but canít afford to pay the many hundreds of millions of pounds required to get the whole of the UK popping pills.

He referred to NICE in an obscured way saying that they advise the use of statins in certain cases. This was very deceptive of such a high ranking academically qualified professional. Not a single mention of any contraindications ether, one would have thought there may be some if a large scale study over say 10 years or more had been conducted. After all Statins are known to have contra indication.

Will you be advising your students against listening to the real snake oil sales-people?
Quote
"Doctors unhappy : http://news.bbc.co.uk/1/hi/health/7326870.stm
Dr Peter Trewby, a consultant physician at Darlington Hospital who has studied how willing patients are to take preventative medicines like statins, believes we are already prescribing too many statins.
He said: "We are turning healthy people into patients, we are medicalising people and making them worry about their health unnecessarily.
"I would take a statin if I had a heart attack but I certainly wouldn't take on otherwise."
Many GPs have told The Investigation they feel that they are being pressurised to prescribe statins to patients some of whom have almost no chance of benefiting.
Dr Stephen Fox, a GP from Leigh in Lancashire became so worried by the level of side effects he was seeing in his elderly patients that he is asked the NHS if there was any research evidence on statins and the over-75s.
He was told there was none.
He said "At some point you have to ask where is the line going to be drawn - does absolutely everybody have to be on these?"
Lunatic political parties attack countries that are unable to defend themselves, blow them to bits with high tech weapons massacre men women and children that have no interest in war or politics in the name of Oil, Sorry "weapons of mass distraction"!
 
« Last Edit: 10/11/2008 09:39:52 by Andrew K Fletcher »
Science is continually evolving. Nothing is set in stone. Question everything and everyone. Always consider vested interests as a reason for miss-direction. But most of all explore and find answers that you are comfortable with