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I wish you could tell me the difference between the top of a U tube and the top of a single tube. Particularly if the tube had a 'domed' top. Assume that the vertical height is greater than the 10m , conventional, limit.The molecules need to stick to the top surface whether it's a U or just the top of the tube.On the attached diagram, the region in the upper section of both the single vertical and the U tube are under exactly the same conditions. How is the water supposed to stick to the top of one yet not to the other? How do the molecules 'know' that they are in different bits of apparatus so that they can behave differently? A loop of string stuck to the top of either curve would pull away from the upper surface just as easily. Whatever the tension may have been, the liquid would not 'stick' to the top any easier for either case.Can't you see my problem?
The video link about the ocean circulation was readily dismissed by yourself. That video shows clearly how a sinking denser ocean water can cause a dragging effect on water from the equator pulling up warm less dense water thousands of miles.
For anyone who doesn't know exactly 'how trees work' or has their own ideas about it, I suggest you take a look at this link. It is a Google Book review and does not show all the pages but there is plenty of evidence which you can read of a well thought out bit of Science which takes the magic out of the mechanisms used by plants to raise water.The main point about it, as far as I am concerned, is that it depends upon the Xylem tubes being extremely thin. Cavitation is always a problem and can stop the process.The mechanism does not rely on 'flow' or inverted U tubes. It is described and explained in terms which make sense and do not go against any established ideas.
I am, basically, a reductionist. If there is a theory which explains a phenomenon and it doesn't involve needlessly new complications then I tend to find it acceptable. Science, in general, looks to explain the World with a minimum of 'laws'. The book in that link manages to give explanations for the phenomena involved with tree sap movement which don't need to introduce any new 'fanciful' ideas. Actual numerical values are quoted and that always reassures me that someone knows what they are talking about. The effect of adhesion and cohesion, taken together is considered and there is a very reasoned discussion of the actual forces involved and the requirement for tubes of the sort of size that Xylem uses. No magic and nothing actually new - just an intelligent approach which uses values drawn from elsewhere in Science.
I mention cavitation because that is something which couldn't be dealt with if the cavities were large.
Your question about how molecules know where they are has been ignored because molecules cannot know where they are. If you could re-word your question so it makes more sense, maybe I can understand where you are coming from better.
As you said earlier, the tension must be acting on all the water, so why do you expect it to be acting closer to the wall?
The walls of the tube cannot collapse and account for the changes in water level when the open ends of the tube are pulled out of the container filled with water.
and each is as strong as each other until the water parts company with the glass
We'll have to leave it at that then. When you learn some Science rather than a list of partially related instances, you may realise what I am talking about.We usually find that people without respect for qualifications are those who have very few of their own.
Is it just my imagination, or is Andrew obsessed with trees?Perhaps he was a dog in a previous incarnation
Successfully operating a siphon in a vacuum, using an exotic ionic liquid that can handle the extreme conditions.http://www.youtube.com/watch?v=8F4i9M3y0ew