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Some Scientific Problems (Geophysics)
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Brian Ambrose



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So, both our scientific consultants, Chas and Bri, agree that in a closed system, given enough time, all that will be left for inspection is a) liquid water at the bottom and b) saturated air at the top.


No... I (we) agreed that in a closed system with a constant temperature etc. etc. there would be water and 'saturated' air in equlibrium. These are not the conditions on earth over a billion years or even one day, since temperatures and other conditions are constantly changing and causing moist air to dump its load as rain, etc. etc.
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Mick Harper
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No... I (we) agreed that in a closed system with a constant temperature etc. etc. there would be water and 'saturated' air in equlibrium.

AE says that when people are defending a paradigm they often cite one example plus 'etc etc'. This generally means they either don't know or have very little confidence in 'the other reasons'. So temperature it is. Please run a laboratory closed system for a billion years, varying the temperature ever so slightly (but making sure every molecule spends at least several hundred million years within the optimal range) and tell me if the air becomes saturated or not.

These are not the conditions on earth over a billion years or even one day, since temperatures and other conditions are constantly changing and causing moist air to dump its load as rain, etc. etc.

Ah so! Another reason just edges in. While you are doing the above experiment (you can vary the temperature a bit if you want) let us know if the not-very-saturated air keeps dumping water on a sufficient scale as to defy overall the physical laws about evaporation. Where's Brian when you need him?
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Chad


In: Ramsbottom
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Brian Ambrose wrote:
It cannot be right that a container full of water could be vapourised simply by making the container 1% bigger - unless you maintain the vacuum by removing the gas.

I see now how the process is self limiting.

Initially there is no water surface and no empty space. But as the volume increases, the water pressure drops (as it expands into the increased volume) and will (once the pressure drops sufficiently) start to boil.

At this point the released water gas, takes up more volume than the same number of molecules in liquid form. The pressure in the vessel consequently increases, stopping the boiling process and creating equilibrium.

Thanks Bri.
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Mick Harper
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No ganging up, you two.
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Chad


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Sorry Mike... err... Mick.

AE says that when people are defending a paradigm they often cite one example plus 'etc etc'

Could get away with just one etc... pressure.

Please run a laboratory closed system for a billion years, varying the temperature ever so slightly (but making sure every molecule spends at least several hundred million years within the optimal range) and tell me if the air becomes saturated or not.

If the laboratory closed system contains constantly shifting masses of water and air, whose temperature and pressure are anything other than homogeneous, you will not get an homogeneously saturated volume of air, but one where evaporation and condensation take place in ever shifting locations.

In fact your billion year old world is not an homogeneous closed system, but in fact, a series of interconnected stills...

It's all just moonshine.
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Mick Harper
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You're overlooking the one point that everybody has been overlooking since the birth of time (or the Royal Society whichever came first). Take three identical hermetically-sealed boxes, a hundred metres by a hundred metres by a hundred metres. We fill the first one half-full with water and keep everything at a constant and wait for equilibrium. What will find when we open the box? As Mickey Miles used to say.

PS I have taken note that the two of you have now produced just two factors, temperature and pressure. And even these required a little ...um... pressure. My AE antennae are slightly quivering.
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Chad


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What will find when we open the box?

Depends whether it's sat there in isolation, or connected (via very large ducting) to numerous similar boxes whose temperature and pressure are constantly changing.
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Mick Harper
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Chad, please answer the question. No careful ignoral at this important stage. Just assume the box is a closed system. Use your scientific imagination to presuppose whatever this means for present purposes.
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Brian Ambrose



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We fill the first one half-full with water and keep everything at a constant and wait for equilibrium. What will find when we open the box? As Mickey Miles used to say.


You seem to assume that leaving it long enough will somehow 'saturate' the air. It won't. There will be some humidity but there's no way of knowing how much without knowing the temperature - and probably a bunch of other stuff too. The point is that the humidity will change if the temperature changes.
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Mick Harper
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All right, Brian, tell me what conditions are required to ensure that saturation will be reached.
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Brian Ambrose



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Well, I've been unclear what you mean by 'saturation' from the start - 100% humidity is not, if I recall correctly, actually fully saturated air. I suppose the inside of a steam-room is closer to that, so maybe the conditions you need will be similar to that required for a steam-room (ie lots and lots of heat and water, I'm guessing probably more than would ever regularly occur naturally).

Edited quickly to add, and as soon as you switch off the power to the steam-room, the humidity will go down.
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Chad


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Mick Harper wrote:
Chad, please answer the question. No careful ignoral at this important stage. Just assume the box is a closed system. Use your scientific imagination to presuppose whatever this means for present purposes.

O.k.... your big box could possibly have reached hydrological equilibrium.... but this is not a good analogue.

The Earth has never had the opportunity to reach equilibrium, because of its annoying habit of constantly rotating and presenting an ever-changing face to that big burny thing in the sky.

We can forget all the etceteras (even pressure) the Sun alone is enough to prevent equilibrium.

If you increase the size of your box to something approaching the volume of the Earth (to about ocean depth) together with its atmosphere... and subject its internal contents to the sorts of constantly changing (Sun induced) variations in temperature that are daily occurrences here on Earth... I doubt you box would ever reach equilibrium either.

To ignore the Sun is... well... careful ignoral.
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Mick Harper
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Please, Chad, start acting as an AE-ist. It is you that is in careful ignoral mode. I am specifically not trying to mimic the earth at this stage (though when I do you will be welcome to comment).

Please PLEASE just stick with Stage One for the moment, the closed box. Do you both agree (or not) that this completely closed system with a constant supply of optimal conditions (from my point of view) will reach an equilibirum position and that equilibirum position will tend to be where the exchange of evaporation and condensation will be at a minimum and that minimum position will tend to be where the air is saturated (whatever that means) rather than not.

PS Really try to be helpful. I promise you a nice surprise (which might not work) at the end.
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Chad


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O.k. At this stage, under these conditions your box has reached the point where the air cannot take on any more moisture.
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Mick Harper
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You sound peeved but remember what I asked for

Take three identical hermetically-sealed boxes, a hundred metres by a hundred metres by a hundred metres. We fill the first one half-full with water and keep everything at a constant and wait for equilibrium. What will find when we open the box? As Mickey Miles used to say.

While we await Brian's no doubt equally reluctant agreement, you can move on to the second box. This is the same as Box One but this time you can introduce any conditions you feel best mimic the real world. But please, Chad, stick to the laboratory model. It's a box, a big box to be sure, 100 by 100 by 100 metres, but still a box. We still want to know what has happened when you open the box (after a very decent interval) in terms of liquid, air, moisture etc etc but you are free to enter any equilibirum caveats.

Remember, keep being helful!
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