Why we need to think before we build

[Penners]

Probably - to get the job done before the rain started and his trades all went home.

He was, of course, the world's first arkitect

 

[tom.harrigan]

NT wrote:

"Variations are normal for dynamic equilibria"

Then backed up his argument with the example of his house being centrally heated and a lightbulb.

Lets ignore for the moment that neither system is in equilibrium with anything, as they are both powered. Let's ignore the fact that the temperature of the house is being controlled by a machine. Let's _pretend_ that equilibrium and steady state are the same thing for a moment. Even in this unreality, the notion that adjusting a thermostat or switching on a light are examples of a "variation in dynamic equilibria" seems preposterous to me.

T

 

[NT]

NT wrote:

"Variations are normal for dynamic equilibria"

Then backed up his argument with the example of his house being centrally heated and a lightbulb.

Lets ignore for the moment that neither system is in equilibrium with anything, as they are both powered.

Being powered has nothing to do with whether an equilibrium is present. If heat is flowing into and out of the building at the same time, temp is stable, and heat can flow both ways, we have dynamic equilibrium.

http://en.wikipedia.org/wiki/Steady_state

Many chemical reactions that are dynamic equilibria rely on heat input.


The example I gave could be improved on, but the notion that dynamic equilibria can never change is an inherently unworkable one. At some time in the life of the universe every present dynamic equilibrium changed, and every one will change at some very distant point in the future. Permanence can not be part of the definition of a dynamic equilibrium, if it were, none would exist. They can and do change.

Let's ignore the fact that the temperature of the house is being controlled by a machine.

I dont think that makes any difference, presence or absence of machine control is not part of the definition.


Lets try a better example. The sun heats an incandescent object in a triple glazed glass container. Solar concentration is used. Now we have a dynamic equilibrium when we have a steady state, which occurs at times. We all know that equilibrium point will shift in time, and frequently.

Now lets add control to the system, such that from 11am to 2pm a screen partially obscures incoming solar radiation. When the screen activates, the system heads toward a new temperature point. When this temp is steady state, the system is also in dynamic equilibrium. Moving from one dynamic equilibrium point to another will occur sometimes.

Many powered chemical reactions reach dynamic equilibrium, and it is simple enough to then move that reaction to another equilibrium point.


NT

 

[tom.harrigan]

I suggest you actually read the wikipedia link you so kindly gave to back up my argument and highlight your error.

http://en.wikipedia.org/wiki/Steady_state

I really have nothing to add to it.

T

 

[biffvernon]

Fascinating, I'm sure, but just to bring us back to the start of this thread

Current sea ice conditions: August 16, 2007

Arctic sea ice has now surpassed all previous records for the lowest absolute minimum extent. Satellite measurements recorded the previous record, 5.32 million square kilometers (2.05 million square miles), on September 20–21, 2005. As of this morning, the extent was 5.26 million square kilometers (2.02 million square miles).

Sea ice extent for August 16, 2007,(left) compared to previous single-day record

 

[Nemesis]

Thanks Biff.

I won't ask if we should worry.


(Wiki as a reliable source - discuss.)

 

[Lime]

(Wiki as a reliable source - discuss.)

It isn't, is it?

 

[Nemesis]

Or - it is isn't it?

http://technology.timesonline.co.uk/tol/news/tech_and_web/article1637535.ece

 

[biffvernon]

The bit that I wrote is reliable.

(says I )

 

[NT]

I suggest you actually read the wikipedia link you so kindly gave to back up my argument and highlight your error.

http://en.wikipedia.org/wiki/Steady_state

I really have nothing to add to it.

T

I did, obviously. This has got a bit silly.

NT

 

[tom.harrigan]

Oh dear! If you don't understand the difference between an equilibrium and a steady state then that's the end of the matter. The wikipedia entry is crystal clear.

 

[NT]

I do - and as you say, wiki is pretty clear. If you have something of substance please present it, otherwise we're done.

 

[tom.harrigan]

So, "Arctic sea ice has now surpassed all previous records for the lowest absolute minimum extent." I know that fills some people with glee, particularly those that revel in disaster for humanity. However, those without vested interests in impending doom (whether emotional or financial) might be forgiven for asking when these records actually began? As fas as I can tell, they are referring to satellite records which began only 30 years ago, just as we were emerging from the great Global Cooling scare.

Furthermore, there is ample evidence that the arctic was warmer not so long ago: http://www.washingtontimes.com/article/20070814/NATION02/108140063

It's not my intention to dampen some peoples evident enthusiasm for disaster, just that I wish they expressed it in a more balanced way. Then we might be more readily convinced.

T

P.S.

I have it on good authority that it's actually just a dynamical steady-state equilibrithingy, so I'm not worried.

 

[Lime]

"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."

:lol: :lol: :lol: :lol:

How very true!

 

[Nemesis]

Heavens - how sad to find oneself in the apparently minority category of open minded amongst the scornful people who seem to be overtaking this site at the moment.

It used to be the case we could appreciate information posted without getting our knickers knotted, but it seems now we have so many grumpy old men crawling out of the woodwork (even if some may be young in years) it's quite revealing.

Thanks Biff, keep at it.* I enjoy being kept up to date. Keeps me feeling young.

* Posting I mean - not being a GOM.

 

[Penners]

"The object of life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."

That sounds like a logical impossibility to me. :wink:

 

[Moo]

I've found both sides of the argument very interesting but continue to be open-minded (or muddle-headed?) about the issue.

 

[Nemesis]

Of course Moo, if it's true we are heading for disaster then I bet those denying it will be the first to scramble for the lifeboats.

 

[Moo]

Does that mean that those who are prophesying disaster won't?

 

[Nemesis]

No as they will be safe on the moral high ground.

8)