Forget "Conserve Energy." Instead, "Slow the Increase of Entropy!"

Jolb

It bugs me when I see the phrase "conserve energy" in eco-friendly contexts. Even though it's clear what they mean: don't leave your lights on or burn gasoline needlessly, it is physically nonsense and serves to confuse people (like Gomar) who haven't studied physics.

Energy is always conserved. Conservation of energy is basically the core principle of all physics. When people mention energy "leaving a system," they just mean that the energy moves from the "system" portion of the universe to another portion of the universe--the universe always conserves energy.

What keeping the lights on or burning gasoline does is transfer energy from a very ordered (and therefore useful) state, like electrical potential energy or chemical energy, into a disordered state, like heat. We know this in physics as an increase in entropy.

My favorite example is the sun-earth system. The sun and the earth are in thermal equillibrium--as much energy that shines on the earth in one day is radiated away from the earth in one day. (I guess this is at least 99% accurate.) The fact that the Sun sustains life on Earth is due to the fact that the photosphere Sun is at a much higher temperature than the surface of the Earth. Therefore, the energy from the sun that arrives on earth is in a much more ordered form: short wavelength photons in the visible spectrum. Each photon carries more energy than the photons that leave the earth, which are in the infrared. Thus the number of photons that leave the earth, R, is much higher than the number that arrive on earth, A. Since there are many more possible ways to radiate R photons than A photons, the energy leaving earth has higher entropy than the energy arriving on earth.


I have heard the term "negentropy" before, a portmanteau of "negative" and "entropy". I think "Save Negentropy" is what the eco-friendly crowd should teach kids, so that they don't get a false impression of physics.

Who's with me?

Pengwuino

Why? That's ridiculously nitpicky, especially when you're talking about a public service message that has real implications to consider.

Jolb

I think it's good for the government to be physically accurate in the information it releases. For example, the US government has decided it's mandatory for all foods to come with a measurement of kilocalories and detailed chemical analyses. Why not just a food-pyramid type of health guideline?

In addition, the use of the word "energy" causes non-physics students to become terribly confused. Check out this gem of an argument from another post:
Clearly Mr. Gomar doesn't understand what "energy" really means. He seems to think burning gasoline produces energy from nothing.

If the vocabulary were changed so that we didn't use "energy" to refer "convertible low entropy energy," people wouldn't be nearly as confused. (Also, I think the FDA should do away with "Calories" and call them what they really are: Kilocalories.)

russ_watters

It isn't nitpicky, it's wrong:

Conserve
b. To use carefully or sparingly, avoiding waste: kept the thermostat lower to conserve energy.
http://www.thefreedictionary.com/conserve

Jolb

My favorite dictionary is Merriam Webster:

You're referring to 1, I'm referring to 3. It's pretty clear that in the phrase "Conservation Law," the reference is to 3.

I see that "conserve" may refer to 1, i.e. use your houses lights sparingly or use gasoline sparingly. However, that does not mean "destroy energy sparingly," and the connotation with destruction is clear in m-w's definition. "Conserve energy" is intended to mean "transfer energy from one form to another sparingly". No energy is destroyed, as per definition 1. And when it's transferred from one form to another, the only thing we can say for certain is that entropy increased while energy remained constant.

I find it obnoxious that you resort to calling someone "wrong" in a semantic debate. Obviously my point is about semantic clarity--there are no absolute rights or wrongs in linguistics. If instead of saying "Slow the increase of entropy," I used the phrase "Gobbeldy the jabberwocky," the phrase is not wrong, so long as you understand what it refers to, and so long as what it refers to is correct.

The phrase "Conserve energy" is confusing because its reference is ambiguous: either def. 1 or def 3. Using Def 3 in that statement is physically nonsense, because in that case, it doesn't express that people shouldn't waste--conservation of energy is automatically satisfied even with human waste. Def 1 is closer to the truth, but it still has the connotation that energy can be "destroyed." A clearer nomenclature would alleviate widespread confusion.

Drakkith

Yet you clearly do understand what the message "Conserve energy" is saying (as does pretty much all of the public) and still complain about it? That's nitpicky. And also ignoring the fact that they aren't using YOUR chosen definition, but another equally valid one instead. The amount of people confused by the use of "Conserve energy" is probably orders of magnitude less than the amount that would be confused by saying "slow the increase of entropy".

Consider that energy, being the ability to do work, is capable of being conserved in the sense that once we use it, we can't get it back thanks to increasing entropy. So we are losing the ability to do work, hence energy.

russ_watters

Yes. You're using the wrong definition for the context. Yes. Yes. You misunderstand again: you missed the word "or". "Wasteful or destructive." One can waste electricity or destroy rainforests. No it isn't. As you said, you referred to #3, but when someone says "conserve energy", they mean "don't waste energy". They mean #1. The person reading/hearing doesn't get to pick the definition, the person saying/writing the statement does. You are misunderstanding what is being said: you are applying the wrong definition.
Ironically, that's completely wrong. When a person says something specific and clear, in keeping with an obvious and accepted definition of a word and another person interprets it in a way that was not intended, that's wrong. Wrong, for two reasons:

1. You've flipped speaker and listener, so your example does not apply.
2. You are purposely choosing an unintended definition. What gets me here is that not only are you wrong, you know you are wrong and are being purposely argumentative!

And of course:
3. In your inapplicable case, you aren't wrong, but you are talking gibberish. One is not entitled to make up words that they are saying in a conversation any more than they are entitled to make up definitions of words they are listening to. I've never misunderstood. I always have known that "conserve water" and "conserve energy" were both referring to "don't waste". Know you know too, so next time you hear it won't make the same error in understanding what was meant.

russ_watters

No, that's being purposely wrong and argumentative. Nitpicky is when you are right and correcting someone else's small error (and being argumentative).

That's nitpicky!

Either way, it isn't physics. So thread locked.