Letters posted here are associated with the following article:

96
Letters
Tuesday, July 7, 2009 12:00 AM

Life is out of whack

It may drive ecologists crazy to talk about a balance in nature. But it's more necessary than ever

The letters thread is now closed.

View:
Wednesday, July 8, 2009 01:10 PM

pwoxby

Well, a charging battery is certainly a system and it is just as certainly not tending towards equilibrium.

Not internally, because it's being acted on by a force external to it. It's tending towards equilibrium with the charging system.

As I said: you, sir, are clueless. You trot out this claptrap without any understanding of what you're talking about.

Beat it kid, and stop trying to get my goat.

Wednesday, July 8, 2009 01:13 PM

pwoxby

The second law is indeed a universal law of physics.

Now you're contradicting yourself, because you've stated several times that it's not.

But the second law as you understand it leads to a clear paradox when applied to a system as simple as a car battery.

There is no paradox, as I've clearly shown. It's your sheer inability to understand thermodynamics. I've flunked out hundreds of your kind, sonny.

Wednesday, July 8, 2009 01:16 PM

pwoxby

If you're really determined to be humiliated, just keep it up. I can assign grad students to post under my handle who would be delighted to have chunks of you in their stools.

Wednesday, July 8, 2009 01:24 PM

Wow you got me pegged

His alarm goes off at 6:30am,

Make that 9:30-10. I'm unemployed atm, but I do have a little freelance gig going.

and he hits snooze.

Yup!

Due to a thunderstorm, the electricity goes out, and he wakes up an hour later to a flashing 1:00 on his clock. "That's a logical fallacy!" he exclaims, wagging his finger at the alarm clock.

You know, I actually could do something like that, I can be pretty weird when I wake up. It would probably be something more like, "The chocolate gnome can't cause that reaction in the multiple, so there's no way it's 9:30 right now."

Determined to continue his day, he goes to get ready for work. While showering, the soap slips out of his hands and hits the floor. "That's a logical fallacy!" He resumes washing.

Getting colder. By the time I'm in the shower, my conscious brain is working, so I'd never make that mistake.

On his way to work, a construction sign makes him take a detour, which will make him later than he told his boss he would be in. "That's a logical fallacy," he cries, wagging his finger at the construction workers, who stare at him blankly through his window.

Not really, because that wouldn't be a fallacy. I get now why you don't understand how utterly I demolished your "arguments." You probably don't even know what I was talking about.

And on and on we go, with the logical fallatio.

Oooh, a sex joke, nice comeback.

I didn't make up the begging the question, special pleading, appeal to emotion, or the red herring, by the way. You should look those up, and maybe tighten up your reasoning a bit. I admit that I made up the middle-school fallacy, for our amusement, if not yours.

I could have just said that you're doing everything you can to avoid addressing the science in any way whatsoever, and left it at that. My way was just a bit more fun, is all.

Your entire argument consists of, "NUH UH! NUH UH! NO NO NO NO INFINITY I WIN! HEY LOOK OVER THERE! WHAT'S THAT ON YOUR SHIRT? BOOP!"

There, was that easier for you to understand?

Wednesday, July 8, 2009 01:25 PM

pwoxby

When a dead battery (i.e., a battery in a state of maximum entropy) is charged, the entropy can only decrease.

Which are you talking about, the battery or the charging system or both?

You need to be specific. You also need to consider everything involved in the proposed operation. A system involving a charging battery necessarily includes the charging system - the battery can't charge itself. Dr. Map has already pointed out several times that you need to pay attention to what you're doing.

Try it again, witling. This time try to get it right.

Wednesday, July 8, 2009 01:34 PM

@pwoxby

You're in trouble now. Dr. Map's grad students can be pretty merciless.

Try whining.

Wednesday, July 8, 2009 01:36 PM

Godot

Hey, no fair. I'm doing this for extra credit. Find your own carrion.

Wednesday, July 8, 2009 01:39 PM

pwoxby

Well, a charging battery is certainly a system and it is just as certainly not tending towards equilibrium.

It's not a system, idiot. It's only part of the system. What did you do with the battery charger, moron? Isn't that part of the system?

Speak up junior, I haven't got all day to waste on you.

Wednesday, July 8, 2009 01:42 PM

@walter_map

I bet he's crunchy and tastes good with ketchup. Leave me a few scraps when you're done with him.

Wednesday, July 8, 2009 05:05 PM

@ walter_map

As I have now written a detailed answer to the question about the charging car battery that addresses many of your points, I will simply post it for your consideration.

To resolve the apparent paradox about the entropy of a charging and discharging battery, I am going to expand the system to include two water tanks at different elevations, the upper one of which is full of water, a turbine-generator that can be reversed to be a motor-pump, a pipe from one tank to one end of the turbine-generator, and a pipe from the other tank to the other end of the turbine-generator. Electrical wires connect the turbine-generator to the fully discharged battery. The tanks are sized so the potential energy of the water in the filled upper tank matches the energy storage capacity of the battery. Friction and resistance losses will be taken to be zero, so no heat will be generated. Not incidentally, the whole system of the battery, tanks, pipes, wires and turbine-generator is isolated.

Now we will let all the water from the upper tank flow through the turbine-generator and into the lower tank. The electricity generated fully charges the battery. Next we will configure the turbine-generator to function as a motor-pump. When this is done the battery discharges running the motor that pumps all the water from the lower tank back up to the upper tank. To preempt the objection that this is a perpetual motion machine, let me interject that I have stipulated that there are no friction or resistance losses. This is an idealized, fully reversible process, a concept which is commonly used in thermodynamic analysis.

We can see that with the water tanks on one side and the battery on the other side we have the thermodynamic analog of a seesaw. When the upper tank is full the water is as far from hydrostatic equilibrium with the lower tank as it can be. In this system it is in a state of minimum entropy. While the water is flowing into the lower tank it is approaching a state of hydrostatic equilibrium, its entropy is increasing and it is doing the useful work of running the turbine-generator. On the battery side, the electrical energy from the turbine-generator is charging the battery, moving it away from chemical equilibrium and decreasing its entropy.

When the battery is fully charged it is as far from chemical equilibrium as it can be and is in a state of minimum entropy. As it discharges it approaches a state of chemical equilibrium, its entropy is increasing and it is doing the useful work of running the motor-pump. On the tank side, the water is being pumped from the lower to the upper tank, moving it away from hydrostatic equilibrium and decreasing its entropy.

Note the beautiful symmetry in the thermodynamics of this idealized, reversible system. Energy, of course, is conserved. That's the first law of thermodynamics. But we see that, no matter which direction the reversible system is moving, an entropy change on one side of the system is balanced by an opposite entropy change on the other side of the system. The entropy of an isolated, reversible system is conserved. This is not the second law of thermodynamics. I stipulated that friction and resistance losses would be taken to be zero. This idealization cannot apply to any real physical system. So no real isolated physical system is reversible which rules out perpetual motion machines.

If the entropy of an isolated, reversible system is conserved but no physical system can be reversible, then we come to the second law of thermodynamics which simply states, in the context of this example, that the entropy of our isolated system can only increase. That means that friction and resistance losses will eventually dissipate the battery until the battery is fully discharged and the water is all in the lower tank. Both the battery and the water will be in their highest entropy states, states of equilibrium. What about the first law? Where will all the original energy go? In a word, heat. Those friction and resistance losses generate heat. The resulting increase in thermal energy will balance the decreases in potential energy and chemical energy in accordance with the law of conservation of energy.

The qualification that the second law applies to isolated systems can now be fully appreciated. This qualification simply means that when the entropy of a system does decrease, the entropy of a system somewhere else has to increase and that the increase will be inevitably more than the decrease (in magnitude).

Finally, let's return to that troublesome statement: "The second law of thermodynamics guarantees that any system, including ecological systems, will always tend towards equilibrium." As I look out my window I see a tree that is converting water, carbon dioxide and light into the polysaccharide commonly known as cellulose. The local system of tree, ground, and air is moving away from chemical equilibrium and its entropy is decreasing. But with the second law, I confidently know that the entropy of a system somewhere else is increasing to more than compensate the entropy decrease. And where is that other system? It's 93 million miles away at the center of the solar system. Thermodynamically, the sun is a radiative energy source whose increasing entropy ultimately sustains all of the localized decreasing entropy systems we call life. And ecosystems, being collections of various life forms, naturally resist a tendency towards thermodynamic equilibrium, a condition colloquially known as death.

Most Active Letters Threads

740

The commendably missing element from Obama's speech

There was no pretense that human rights is our goal, or the likely outcome, in escalating the war
688

Obama's exceedingly familiar justifications for escalation

The "new" approach to Afghanistan touted by White House officials seems quite old
370

America's regression

It's almost impossible to find a nation with as many torture advocates as the U.S. has.
329

Yes, it's Obama's war now

An uninspiring speech sells a dubious policy, but progressives who feel betrayed have only themselves to blame
322

Do Obama officials know what his Afghanistan plan is?

What explains the completely contradictory statements from key aides on a central plank of the war strategy?

View all »

Letters Help

Currently in Salon