[lyner]

Well in excess of the Earth’s escape velocity, yet unable to escape from the Earth’s influence proves my point really.

But Science usually likes a bit more of a nuts and bolts explanation. Of course the presence of the Earth is relevant. The details of 'how' are what makes Science interesting, surely.

then as it falls it creates a dragging effect on each of the water molecules

? The force is due to PRESSURE difference. Atmospheric pressure acts on the surface of each of the reservoirs. It is this pressure that supports the column of water. This was discovered by  Torricelli, yonks ago.
http://en.wikipedia.org/wiki/Evangelista_Torricelli
One atmosphere will support about 10m of water at sea level.
When you introduce even a small amount of more dense liquid on one side of your tubes the pressure is a tiny bit greater at the bottom of that tube. The pressure at the top of the tube will consequently be a bit less than at the top of the other tube and water will flow to equalise the pressure. If, instead of two shallow troughs at the bottom, you had two deep jars, the situation would balance out with a slightly higher level in the jar at the bottom of the  tube with the solution in it.
By injecting salt into the top of the system you are introducing more energy into the system - the energy coming from your muscles. There is nothing magical or unknown about this. You are not getting any 'free' gravitational energy.
The effect of fresh water flowing onto the top of salt water is seen at the sea locks at the ends of the Panama Canal; the gates swing open (equal  hydrostatic pressures each side) when the fresh side is still higher than the salt side and fresh water pours out into the sea. This is what is happening at the top of your loop.

Yours is a pretty demo but doesn't demonstrate anything new to Science. remember, there is very little actual ENERGY transfer involved. It has not been 'hitherto overlooked', it hasn't been utilised because it doesn't actually supply any appreciable amount of energy.

As you imply, when plants do this, the energy source is probably from the evaporation (transpiration) of the water from the leaves. This produces a change in concentration of salts in the sap which achieves what the plant needs.

[Andrew K Fletcher]

http://www.thenakedscientists.com/forum/index.php?topic=1982.0

This topic has been covered in depth here and might answer your questions better than beginning again.

[lyner]

I have read the thread and I can see that each contributor seems to have his own idea as to the 'sole' reason for the rising sap phenomenon. Plants must use more than one mechanism to achieve their end.

First, I have to say that using the words 'suction'  or 'tension' where bulk liquid is concerned goes against established Scientific ideas. Nothing wrong with that, of course, if the 'heretical' words are the only ones which will explain what's going on. Surface tension is much too weak a force to be considered as a candidate.
The simple inverted loop model can be explained perfectly well in terms of Pressure (a good, healthy, concept which works everywhere else). You just can't have 'tension' or 'suction' in fluids. It's always excess pressure on one side which makes liquids flow. I needn't repeat my explanation.

The problem seems to be how to explain lifting higher than the 10m limit. It strikes me that the complex structure of the Xylem is capable of combining both hydrostatic lift and osmotic pressure (which works horizontally as well as vertically) in a distributed mechanism. Water which has been pushed to a reasonable height by hydrostatic pressure  in one u tube can then be moved sideways to another inverted u tube by osmosis. This starts the process again and the final height is not limited by to 30m. You can either visualise it as a set of small, discrete vertical then horizontal motions. The energy comes from the overall loss of latent heat of evaporation when the leaves transpire.

If you can devise an experiment which demonstrates, unequivocally, the presence of your 'tension' in water and cannot be explained in terms of conventional hydrostatic pressure then I would be very interested to hear of it.

[Andrew K Fletcher]

So anyone got a problem with gravity providing us with a mushroom shaped cloud from an atomic detonation?

Any other likely explanation to offer?

Have read all of the other explanations and not a single mention of gravity among them. Odd how we take gravity for granted ain't it ?

[lyner]

Any mention of convection involves an implication of gravity. Are we also required to include basic kinetic theory in order to justify the idea of expansion of a gas when the temperature is raised? We have to be allowed to talk in shorthand at times. Later, it may be necessary to  go in more deeply.

[Andrew K Fletcher]

Talking in shorthand leads to dangerous assumptions, poor science and erroneous literature!

To ignore gravity as the force that provides us with the shape of the mushroom cloud could lead many people into believing that gravity is a weak force, when in fact if gravity was a more weaker force than the powerful explosion of a nuclear weapon, we might expect to see far more spectacular results from a detonation. When what we do see is a blast that is far weaker than a volcanic eruption, which of course, any such eruption is a direct result of the immense power of gravity providing us with instability at times and thankfully some stability on the Earth’s surface!

We cannot talk about the atmosphere providing us with the suppressing blanket over a nuclear explosion without first considering that it is gravity that provides us with every single event that occurs here on Earth, in space and on every single solar system out there! When we split the atom to cause the explosion we break the atoms away from the force of gravity, and as we can see this is fortunately but a temporary situation as the status quo is rapidly returned in the wake of the explosion. And as we can see by the shape of the cloud that forms we are presented with a spectacular example of how powerful gravity really is!

Without gravity the people that create the bomb would not even exist to begin with! Without gravity there would not be a nuclear force because there would be no atoms to split! There would be no minerals, chemicals, metals, machines, or even thoughts on how to build a nuclear weapon. Without gravity there is not even nothing!

Andrew K Fletcher

[CZARCAR]

sez mushroom but not nuclear?