Monday, August 02, 2010

Boiling An Egg

Thermodynamics is a fascinating exercise. We had an instructor who would be writing formulas on the blackboard while he was lecturing, and would work his way around all four sides of the room, requiring us to move our seats to keep up with him. When he got back to where he started he would indignantly ask who had been writing on his blackboard.

To say that he was intelligent would be understating things. He would pause in his lecture from time to time and scribble on the blackboard for a minute, erase it with an apology to us, and continue the lecture. I finally asked him what that was about and he admitted that lecturing rather bored him and so he worked differential equations in his head while doing so. The blackboard work was when he reached a part he couldn’t do in his head. Yeah, the part of a freaking differential equation that he couldn’t do in his head, while lecturing on thermodynamics.

Anyway, what started this train of thought was “global warming” and San Diego experiencing its coldest July in 77 years. I did not put the term in quotes due to not thinking that our planet is heating up; our planet is absolutely heating up. I put it in quotes because the term doesn’t describe what is happening with sufficient accuracy; what’s happening is actually even worse than that, our planet is gaining heat content.

That’s where my courses in thermodynamics comes in: temperature and heat are not the same thing. The temperature of something does not tell you how much heat it has. They are certainly related, and temperature can provide a clue to heat content, but it is by no means definitive.

Temperature is a measurement of state, while heat is a quantity of energy.

Let’s boil an egg. When the water comes to a boil it has reached 212 degrees, but the egg is not yet cooked. Leave the fire on and the water keeps boiling, but the temperature never increases; water at atmospheric pressure can never exceed that temperature. It is still absorbing energy in the form of heat from the fire, though, because in due course the egg gets cooked. (Not entirely valid, but it works for the purpose of illustration.)

So, yes, our planet is warming up as heat is taken from the Sun and not radiated back to space due to greenhouse gasses but, much more serious, our planet’s heat energy content is increasing.

Back to the egg-boiling exercise. When the pot was first put on the fire, the water was still and calm. There was no movement in the water at all. Then one little bubble appeared on the bottom and rose to the top. Then a few more bubbles appeared. Then a whole bunch of them. The more heat energy that was added to that water by that fire, the more agitated the water became, until it was a seething cauldron of violence. (This one is valid.)

Our atmosphere is that pot of water, and we are the egg.

The rest should be obvious, and I almost hate to follow that delicious little line with explanation, but as our atmospheric heat energy content increases the temperature of it is not the main issue. Sure, that pot of water got hotter, but look at what happened to its physical state!

Overall our atmosphere is warmer but that is not necessarily obvious, nor is it the critical issue. The issue is that the atmosphere is more energetic, and therefor more violent; the jet stream swings both farther North and farther South, the hot parts are hotter and the cold parts are colder, the dry parts are drier and the wet parts are wetter, all of the parts move around, and everything is more violent.

So to talk about a "global warming" crisis raises little alarm; people actually like warm weather, after all, and they can always point to San Diego having its coldest July in 77 years. It might be a little more productive to say that our planet is experiencing a "heat energy crisis."

The bottom line is that the egg gets cooked if we don’t do something.

2 comments:

bruce said...

That's like explaining the difference between mass and weight. I always have mass, weight depends on gravitational pull - here I weigh... none of your business, but on the moon it would be a lot less, on Jupiter it wuold be a lot more and just floating around in space, essentially nothing.

Does greenhouse gases contribute to global warming? No doubt it does, as well as pollution and so on being problems as well. Natural phenomina also change weather patterns, such as El Nino. Does the overall global warming make smaller, more localized changes, or increase/decrease naturally occurring ones? I don't see why not.

I don't like the "oh my god the sky is falling" [no pun intended] mentality of the greeners, nor the close-mindedness of the nay-sayers. But ther eis work to do on it, and everybody (globally) has to be onboard.

But I still don't like Al Gore. Sorry.
Ok, I'm not sorry.

Barbara B. Solbrig said...

I think I live with people like that professor....

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