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wsieber, in what way would thermodynamics 'rely' upon ergodics? Can you give us a specific example that would illustrate the necessity of such reliance? ("Those of us" = laymen and otherwise literary, but not necessarily science-oriented folk) Thanks.
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Carpal Tunnel
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"Those of us"
That includes me. Yes, pls, Herr Sieber.
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old hand
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old hand
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specific example : Boiling of water is a classic phenomenon determined by thermodynamics: At a given atmospheric pressure, the water boils at a predictable temperature(*), wherever and whenever the experiment is done. On the other hand, e.g. a living organism is not thermodynamically controlled: its behavior depends on its previous history, and is not entirely predictable.
(*)for nitpickers: this is valid once an equilibrium state is reached.
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Carpal Tunnel
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Well, thank you very much, ws. It simply seems like physics to me--the boiling of water. What would the predictable boiling of water under specific conditions have to do with the ergodics example of troy provided: the tossing of many heads in a row?
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Carpal Tunnel
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note there was a * next to boiling water.
you might know, most manufacters warn about overheating water in a microwave oven.
when water is heated, it tends to 'move' and as it moves over small flaws in a finish (of a pot or cup) 'bubbles of steam' break out. (it moves on a molecular level, and watched, you can see eddies of movement!)
but if you microwave water in a super smooth vessel (a brand new glass beaker) it can super heat.. that is, it can reach 220 or 225 degrees (hotter than boiling) with no evidence! the smooth sides/bottom of the vessel doen't offer any places for the fast moving molocules to snag on, and 'burst into bubbles' (of steam)--so the steam stays trapped in the water, super heating it.
when you move the cup, you can slosh the super heated liquid,and break the surface tension.. then it can 'explode' --with a gush of steam, that releases the excess heat, and splashes the water.
so, its quite possible to heat water (under normal pressure) to a super hot liquid.. but normally (one good wash with a nylon scrubby) steam will start to expand and 'erupt' gently (in the form of bubbles) from water at 212 degrees F.
since mirco waves have become common, there have been more that several occations when super heated water has injured people.. (i don't really know if that is ergodic example or not.. but boiling water isn't as 'predictable' as you might think!)
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Carpal Tunnel
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How very, very interesting, of troy.
And this must be somehow related:
I froze a bottle of beer--not quite frozen, that is, but cooled it down quite a lot for just over an hour. Upon taking the bottle of beer out of the freezer and popping the top off what appeared to be just very cold liquid beer, suddenly the contents began to turn to slush. It was the most remarkable phenomenon--and I watched the slush literally become created inch by inch thereby making it impossible to pour the beer.
Somehow I think the bubbles/boiling slush/freezing tales must be related.
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Similarly, water can be supercooled and will not turn to ice while it is moving. Running water in northern streams in wintertime is a perfect example.
i had a friend wh9o worked in an ice-making plant in DC many years agol He said that they cooled water in big vats with paddles roiling the water, and when the paddles were removed the ice formed instantly with a big thump. The vats were square but had tapered sides so the ice would have a place to go when it expanded.
Also, something interesting. Water, like most solids and liquids, tends to shrink in size (up to a point.) And that point is 4 degrees Celcius. If you cool water below that down toward zero C, which is the freezing point, it actually expands slightly in volume.
This is why definitions for volume/weight based on water specify that the water be at 4 Celsius. That way all scientists have the same amount of water in a given volume when doing experiments.
TEd
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re:Also, something interesting. Water, like most solids and liquids, tends to shrink in size (up to a point.) And that point is 4 degrees Celcius. If you cool water below that down toward zero C, which is the freezing point, it actually expands slightly in volume.
yeah, every homeowner knows that! water expands when frozen and bursts the pipes!
super cooled and super heated liquids are strange things, as are non newtonian fluids. (these are fluids that don't generally follow newtons 'laws')
for example.. take a bowl of water (or a pitcher) stir (whirl) it at high speed. (with a mixer/in a blender) and the liquid get 'thrown' to the sides, and upwards.. it moves rapidly in responce to the whirling blades.
now take egg whites.. and watch them.. they don't get flung to the sides, they will (at low speed) climb up the beaters blades (right up to opening for beater to attach to the motor if you are not careful!) STP (oil treatment) does the same thing! (which is why its suppose to be good for your engine.. unlike oil/water/most liquids, it too clings to moving parts, and is not 'flung away' --it adds this cling property to your oil, making it 'cling better' and coat the moving parts with oil better.
i have no idea how well it works in an engine, but its works like a champ in a bowl with a hand mixer!
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addict
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of troy, m'dear - Do we even *want to know why you were using a hand mixer on a bowl of STP? 
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how did you entertain your kids on rainy days of summer? a used hand mixer (price $1 cause it only worked on low) was great fun for mixing non food items..
another cool--but messy-- non newtonian fluid is a slurry of corn starch and water.. (technically its not really a liquid, but a solution of corn starch in water)...
but the important thing is this:
when under stress, corn starch molicules align themselves at right angles to the stress..
which in lay man's terms means--if you smack (really hard, really fast!) your hand into a pie plate filled with a cup fo cornstarch slurry, you don't get covered with the slurry!
as you hit it, it becomes hard (rock hard! use an open hand, not a fist!) but seconds later, as your hand just sits there (not smacking) it is no longer 'stressed' and your hand just sinks in.. --and gets covered with corn starch slurry..
we bought lots of old rotary dial phones too, to take apart, and 'play' with. my son still has and uses a rotary phone he build for himself (mounted on a block of wood) it looks strange, (it has a toggle switch for reciever up/down) and the handpeice hangs on the side)
one year we made 'salt rising bread' by cultivating a salt (brine) tolerant yeast--that was rather aromatic..
the kids liked when we did super saturated solutions.. (and make rock candy, and rock salt)
we were always doing crazy projects/experiments.
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