Thermodynamics 101: Entropy

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I’ve gotten a reply from a well-known Democrat in these parts that shows that the true believes in Global Warming really don’t understand what temperature and heat really are. (link)

As a favor to that particular reader, and readers everywhere, I will take some time to explain some very difficult concepts. These concepts are critical to understanding why the Greenhouse Effect is nonsense. (link)

I’m drawing this lesson from a brief reading of Wikipedia’s entry on entropy. You’re certainly welcome—and encouraged—to read the article, as well as find a good textbook on Thermodynamics that should contain several great examples and exercises to help you learn the concept.

Don’t be surprised if this concept is difficult to understand! In terms of physics, it’s still a relatively new idea, being discovered in the mid-19th Century. However, if you think carefully, you will come to understand the concept quite well.

In physics, we talk a lot about energy. Energy comes in different forms, and energy is transferred from one object to another. We know that energy is conserved, except in tiny edge cases that don’t matter in the big world (as opposed to the quantum world of particles and photons.) We can measure the energy before, and measure the energy after, and know that the two quantities must equate each other. What happens in between is irrelevant.

I want you to imagine a bag of marbles. Now, if I tightly tie the bag of marbles together so that they can’t move around, and throw them at a target of some sort, the kinetic energy of those marbles will almost completely be transferred to the target. This is because the marbles don’t “lose” any of the energy in plastic deformation (as long as they don’t crack or break up). The marbles can’t shuffle around in the bag very much, so we don’t see much energy being lost there either.

If you took the same bag of marbles, and allowed them to move around freely in the same bag, then threw it at the target, you’d notice that less energy was transferred. See, the marbles end up bouncing around in that bag during the collision, and a lot of energy is spent moving marbles back and forth rather than transferring energy to the target. This wasted energy is Entropy.

The problem with Entropy is that it’s useless. You can’t restore order to a disordered system. Well, not easily. It takes a lot of work applied in very smart ways to get in there are straighten things out. Even then, you can only straighten things out a little bit.

Temperature is almost an exact measurement of Entropy. All this bouncing around and moving around randomly is what it means to be warm. Cold systems have more order, while hot systems have less. It’s hard to picture this, but imagine a bunch of atoms bouncing around inside some chamber. If they are moving slowly, then the pressure they exert from bouncing off the sides of the chamber is small. If they move around quickly, then the pressure increases. This is how, ultimately, energy is measured—by watching for changes in volume and pressure to a substance. In mercury thermometers, you can see the mercury rise and fall. In other thermometers, like bi-metallic ones, the metal stretches or shortens. In resistive thermometers, the resistance of the substance increases or decreases.

Now, Entropy can be analyzed and interpreted in a variety of ways. What you will discover is that two properties of Entropy emerge:

  1. Entropy never decreases, unless outside work is applied. (When you include the external work in the system, entropy still increases.)
  2. “Hot” stuff transfers entropy to “cold” stuff, increasing the overall entropy WITHOUT changing the total energy of both systems. Or, another way to look at it is that “cold” stuff sucks entropy out of “hot” stuff.

Further mathematical and theoretical analysis will lead you to conclude that those two points are really two faces of the same physical law, the law we call the Second Law of Thermodynamics.

Those who “get” the Second Law understand that entropy is wasted energy and know how it behaves. Those who don’t “get” the Second Law don’t understand what entropy is or don’t believe that it is irreversible.

To draw this back to the Greenhouse Effect, too often people state that the CO2 layer “retains”, “reflects” or “absorbs” heat from the ground. When they discuss temperatures this way, they are not thinking of Entropy, and so their mental model of the system is patently absurd. When you treat heat transfer like energy transfer, then you will likely come to the wrong conclusion.

If you don’t trust what I have said, then you are free to either research for yourself or find the closest physicist and see what they have to say about it. Science isn’t politics, and trying to mix the two destroys science.

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19 Responses to “Thermodynamics 101: Entropy”

  1. tensor Says:

    This wasted energy is Entropy.

    Jonathan, as you’ve already been reminded in another thread, entropy is not energy. Thus, your claims here make no sense.

    Cold systems have more order, while hot systems have less.

    Not necessarily. The temperature depends on the amount of energy the system has as heat, which means a high-energy system has a greater chance of being a high-temperature system. You’re confusing energy with entropy again.

    This is how, ultimately, energy is measured—by watching for changes in volume and pressure to a substance.

    Temperature measurements help as well. E.g. the Ideal Gas Law, PV=nRT, where P is pressure, V is volume, n is the amount of gas, T is the temperature, and R is the gas constant. Note that the product PV results in a unit of energy, so the energy of the gas is a product of the pressure and temperature, but also of the temperature and amount of gas.

    I think the root of your confusion of entropy with energy results from the need to avoid all of those pesky temperature measurements, which clearly show the earth warming over time.

    “Hot” stuff transfers entropy to “cold” stuff, increasing the overall entropy WITHOUT changing the total energy of both systems. Or, another way to look at it is that “cold” stuff sucks entropy out of “hot” stuff.

    Wrong, wrong, wrong, wrong. Isentropic energy transfer is possible. Hot stuff transfers energy to cold stuff. The sun transfers heat to the earth; the earth transfers heat to space. If we place an insulator (greenhouse gas) between the surface of the earth and space, we will retain heat in the earth.

    It’s a very simple model, and the data we’ve gathered support it. All of your flailing here doesn’t change that. But you’ve now admitted you don’t understand basic thermodynamics, so you’ve destroyed the credibility you originally claimed to have.

    Not to mention having produced a lot of hot air. :-)

    • Jonathan Gardner Says:

      I think it’s important that readers don’t get sucked into your cloud of confusion. You are adding things to the arguments without refuting existing things. You are trying to make the argument so complicated that no truth can be seen. This may be called the “Chewbacca Defense” in logical circles. It’s a shame you are resorting to such tactics.

      Let’s walk back a bit and address the question at hand: Does the Greenhouse Effect exist? The answer is “no”. There is nothing in TD that can ever give you any hope of showing how heat can flow from cold to hot or how heat can be stored when the system is exchanging heat with other systems. You can’t refute this because trying to refute this is the same as trying to override the 2nd Law of Thermodynamics. Go ahead and try to describe the Greenhouse Effect in any way that doesn’t violate the 2nd Law. You can’t do it without saying something simple like “CO2 increases the insulation of the atmosphere.”

      What data do you have to support your claims of a warming earth or that increasing CO2 increases the insulation of the atmosphere? The data you claim exists doesn’t exist. Dr. Jones lost it, or never had it, or invented it, but we all agree he lied about it because he admitted it, not just in his emails that he thought were private, but on national television interviews. I cannot emphasize this enough: SHOW ME THE DATA.

      Actual measurements of the effects of CO2 show that increasing CO2 decreases the insulation of the atmosphere slightly. I’ve already pointed to the paper that suggest this.

      No amount of investigation into what is actually going on at the atomic level is going to change the measurements we see. That’s because the measurements cover everything noteworthy. Experimental physics trumps theoretical physics. We cannot say the measurements are wrong because they are never wrong as long as they are done properly. If theory and measurement contradict each other, we throw away theory, not measurements. At least, that’s the way it should be.

  2. demo kid Says:

    There is nothing in TD that can ever give you any hope of showing how heat can flow from cold to hot or how heat can be stored when the system is exchanging heat with other systems. You can’t refute this because trying to refute this is the same as trying to override the 2nd Law of Thermodynamics.

    Radiation, radiation, radiation. You have not refuted this, and this is precisely what is at the heart of the “greenhouse effect”. Are you denying the role of radiation here?

    Go ahead and try to describe the Greenhouse Effect in any way that doesn’t violate the 2nd Law.

    See above, Jonathan.

    But how many other ways do you want people to describe this to you? If you cannot grasp a simple concept like radiation, you don’t know the principle which is at the heart of climate change…

    • Jonathan Gardner Says:

      Radiation, radiation, radiation. You have not refuted this

      All interactions between molecules is via radiation, whether by virtual or “real” photons. That’s how the EM force is transferred.

      TD doesn’t need to account for every possible way that two molecules can interact, it only needs to know that every interaction obey the other, more basic laws of physics such as conservation of mass, momentum, and energy. This is why you can be completely ignorant of convection vs. conduction vs. radiation and still get the right answers when using TD.

      What I have refuted is that the colder layer of gas cannot heat the warmer surface of the earth. That’s the 2nd Law of Thermodynamics, and anyone who claims cold heats hot or entropy decreases over time cannot claim to be built on solid physical principles.

      I am perfectly capable of grasping the simple concepts such as “heat does not flow from cold to hot” and “violating the 2nd Law of Thermodynamics means your theories are completely broken.”

  3. tensor Says:

    SHOW ME THE DATA.

    Well, after several pompous failures to lecture us mere mortals on the science, you deign to look at mere data. As always, your timing is impeccable. From the current issue of Scientific American, via their on-line service:

    A new report from the U.S. National Oceanic and Atmospheric Administration lists 10 indicators that global warming is happening: rising humidity; rising sea-surface temperature as well as heat stored in deeper waters; shrinking sea ice, glacier and springtime snow cover; rising temperatures over land and sea; and rising sea levels.

    All point to a rapidly warming world. And all are based on actual observations, from satellites high in the sky to meteorological stations in the middle of a Kansas cornfield.

    You can debate how bad global warming will be or what to do about it, but it’s hard to deny it’s happening anymore. The physics of greenhouse gases trapping heat are clear.

    That article has a lot of links for you to read and enjoy — and hear! –, so we’ll understand if you don’t have time to post on this topic for awhile. Meanwhile, some mopping-up, as it were:

    There is nothing in TD that can ever give you any hope of showing how heat can flow from cold to hot or how heat can be stored when the system is exchanging heat with other systems.

    The Earth transfers heat to the Sun all of the time, via radiation. This mechanism includes heat emitted from the surface of the Earth, and the Sun’s own radiation, reflected back via the albedo of the Earth. The net transfer of energy is from the Sun to the Earth, of course, but radiative energy can (and does) “flow” from a cold place to a hot one. (Why you imagined this well-known scientific fact had anything to do with your claims escapes me.)

    Assuming “TD” is your abbreviation for ‘thermodynamics’, one of the main purposes of this science is to explain how heat can be stored when the system is exchanging heat with other systems. In the case of the Earth, it explains very well how the radiant heat from the Sun is trapped by man-made greenhouse gasses, thus warming the Earth.

    And finally, thanks for the laughs:

    I think it’s important that readers don’t get sucked into your cloud of confusion. You are adding things to the arguments without refuting existing things. You are trying to make the argument so complicated that no truth can be seen. This may be called the “Chewbacca Defense” in logical circles. It’s a shame you are resorting to such tactics.

    Tell us again, O Worthy Heir to Sadi, how entropy equals energy — but heat does not!

    • Jonathan Gardner Says:

      Can you point me to the data? It’s nice that SA happens to claim a bunch of things, several of which I already know are wrong. I’d like to see the actual recorded data.

      The Earth transfers heat to the Sun all of the time, via radiation.

      That violates the 2nd Law of Thermodynamics. Heat cannot flow from cold to hot.

      Sarcasm doesn’t help your case.

  4. demo kid Says:

    Hopefully this will get through about the different between radiation and other types of heat transfer:

    With a large enough set of mirrors, could you focus the rays of the Sun to heat a point to a temperature higher than the surface of the Sun?

    • Jonathan Gardner Says:

      That sounds like an interesting experiment. Why don’t you try it and see what happens?

      You might want to, as part of your experiment, try retaining the heat with CO2. I mean, if CO2 is such a wonderful greenhouse gas, it should be no problem to create something hotter than the sun.

      • demo kid Says:

        Nice dodge. Answer the question.

      • Jonathan Gardner Says:

        Ok, this is getting absurd. You think I’m dodging the question by asking you to go ahead and try your experiment. This is what science is all about—try it out for yourself and see what results you get.

        Here’s a hint: Instead of using mirrors, why don’t you get a really big magnifying glass and focus it on a point. See how hot that point gets. If you think CO2 is a wonderful insulator, you can use something encased in a chamber full of CO2.

      • demo kid Says:

        Ok, this is getting absurd. You think I’m dodging the question by asking you to go ahead and try your experiment. This is what science is all about—try it out for yourself and see what results you get.

        I think you have no idea. I’m not asking you to do an experiment; I’m asking what would happen known, verified scientific principles. Given the solar constant is around 1.4kW/m2 for all solar energy (note units in power over area, without temperature), I’d need very large mirrors to do what I’ve proposed, making a real experiment impractical.

        Still, you should be able to tell me if it is possible, given your extensive physics background.

      • Jonathan Gardner Says:

        Here, let me help you understand, with the aid of my extensive background in physics.

        The 2nd Law of Thermodynamics states quite clearly that heat does not flow from cold to hot without added work. That means you cannot use heat from the sun to heat something hotter than the sun.

        If you’d like to find a violation of this law, you are strongly encouraged to demonstrate the violation through an actual experiment. Musings and math equations aren’t going to convince any physicist that the law is flawed.

      • demo kid Says:

        The 2nd Law of Thermodynamics states quite clearly that heat does not flow from cold to hot without added work. That means you cannot use heat from the sun to heat something hotter than the sun.

        Wrong answer. Where, perchance, is the temperature of the Sun included in the solar insolation value of 1.4kW/m2?

        Not to mention that you still haven’t explained how the Sun “knows” that something is warmer, and then decides to turn off its radiation in that particular direction…

      • Jonathan Gardner Says:

        Really, this is getting absurd.

        The sun doesn’t have to know anything. The laws of TD account for everything you can think of.

  5. tensor Says:

    That violates the 2nd Law of Thermodynamics. Heat cannot flow from cold to hot.

    You’re denying that the earth radiates energy, and that some of this energy is intercepted by the sun? Really? demo kid is right: you don’t understand radiative energy transfer — or you’re pretending not to, all the while lecturing the rest of us on heat transfer!

    (I clearly stated there was no net transfer of energy from the earth to the sun, a point you seem to have missed.)

    Can you point me to the data? It’s nice that SA happens to claim a bunch of things, several of which I already know are wrong. I’d like to see the actual recorded data.

    Then go ask some scientists — the ones you keep accusing of misleading us, good luck with that — or read their papers in peer-reviewed journals. (Y’know, actually gain some knowledge of the very area in which you have claimed expertise.) That you dismissed Scientific American‘s (!) summation of this “actual recorded data” simply shows how dishonest your entire line of pseudo-scientific nonsense really is.

    What a strange world you inhabit: NOAA’s research is worthless, ditto Scientific American‘s articles, while entropy equals energy, and your model of global warming lacks radiative energy input. (At this point, your groundless claim that Scientific American‘s materials are “wrong” simply bolsters their credibility.)

    Sarcasm doesn’t help your case.

    Maybe not, but it does help me to weather your strident and misleading proclamations about the science you clearly do not understand.

    • Jonathan Gardner Says:

      You’re denying that the earth radiates energy, and that some of this energy is intercepted by the sun?

      No, I never denied such a thing.

      You’re confusing energy and heat again. Really, the two are very, very different.

      Then go ask some scientists

      The scientists refuse to share their data. Phil Jones, the one that collected the data that showed the hockey stick, “lost” his data. The NASA and NOAA summaries never include the raw data, and whatever access people do have to the raw data suggests that either they are making things up or they are using shoddy practices to get the results they want. Hansen of NASA was found to be on the take—receiving grants to demonstrate particular results. You should really take some time to read rebuttals and hard evidence that the skeptics have. It would help you understand at least how to counter their arguments.

      Show me the data. Demand to see the data yourself. Stop taking the word of people who are being paid millions to produce specific results and start questioning science.

      Oh, and show me a scientist that has ever been correct about anything. You don’t have to go very far back to see “bad” science, or at least articles and studies that proclaimed something we today know is wrong. SA may try to do the best they can, but at the end of the day, they are no smarter than anyone else.

      Please, do educate me.

      I’ve already shared my sources. It’s up to you to read them. Trust me, I’ve already read your sources.

      E=mc^2

      Or, more relevantly, Sadi Carnot.

      You’re right, why bother researching science after Einstein and Carnot had their say? I mean, why would we possibly want to test their theories with actual experiments? I’m going to let the high energy particle physicists know that you said “E = mc^2” and so they don’t need to even turn the LHC at CERN on because whether or not the Higgs Boson exists doesn’t matter in the light of “E = mc^2”.

      On the other hand, I’m sure glad that science has progressed since Carnot. His theories were good but a bit incomplete.

      You do realize, of course, that the entire profession of physics research is based on trying to overturn prevailing theories. It’d be like the top Global Warming experts finding ways to show that AGW doesn’t exist, or evolutionists trying to find evidence of creation. This, of course, boggles your mind, because you’re used to science being a memorization contest to please the teacher and get a good score on the test. You’ve forgotten, or maybe never learned, that real science is found in questioning the status quo and finding new ways of thinking and overturning the old ways.

      The most famous theories of physics survived because their advocates were willing to take the time to convince the skeptics, and were willing to do any experiment that might overthrow their own theory. Why not the same level of scrutiny with AGW?

  6. tensor Says:

    The NASA and NOAA summaries never include the raw data…

    Don’t know much about how science works, do we? The reason for that is the huge number of measurements required to obtain a defensible result. Any “summaries” which included such huge data sets would be unwieldy, to say the least.

    But please, tell us what assertions Scientific American got wrong, and how you know.

    … suggests that either they are making things up or they are using shoddy practices to get the results they want.

    Care to support that broad smear with some examples?

    Stop taking the word of people who are being paid millions to produce specific results and start questioning science.

    Every scientist I have ever met will want to know about these fabulous job opportunities, because they don’t get paid “millions” of roubles, let alone dollars. Please show us NOAA’s salary tables!

    You should really take some time to read rebuttals and hard evidence that the skeptics have.

    Please, do educate me. Provide some links. (But, save us some time, and do not refer me to any results paid for by oil companies, or other polluters. We want to avoid the conflict of interest of which you have here accused others.)

    Oh, and show me a scientist that has ever been correct about anything.

    E=mc^2

    Or, more relevantly, Sadi Carnot. (Have you made his acquaintance yet?)

    You don’t have to go very far back to see “bad” science,

    You don’t have to go ‘back’ at all: http://www.dissentfromdarwin.org/

    …or at least articles and studies that proclaimed something we today know is wrong.

    You are correct. Science advances by collecting more data, and refining (or overturning) old ideas. In Sadi Carnot’s time, “caloric” was an invisible fluid, liberated from matter by grinding or slicing. He showed how heat was not an inherent property of matter.

    There’s a difference between innocent ignorance and careful, studied, applied ignorance. I suggest you learn this.

  7. tensor Says:

    You’re confusing energy and heat again. Really, the two are very, very different.

    Jonathan, when the rays from the sun fall upon your skin, why does your skin feel warmer?

    I mean, why would we possibly want to test their theories with actual experiments?

    Einstein’s equation of matter with energy was very thoroughly tested, by the Manhattan Project. (It was found to be exactly correct.) Sadi Carnot’s concepts have fared very well; the science and engineering based upon them have been tremendously successful, from the smallest two-stroke motor to the most powerful jet engine. If you really believe these theories have not been tested and validated, then you’ve admitted to an even greater ignorance about science than you’d previously demonstrated, and that is a huge — albeit wholly negative — accomplishment.

    I’m going to let the high energy particle physicists know that you said “E = mc^2″ and so they don’t need to even turn the LHC at CERN on because whether or not the Higgs Boson exists doesn’t matter in the light of “E = mc^2″.

    Please do. I rather suspect the “high energy particle physicists know” all about the equation of matter with energy, and that it in fact forms the basis of their research. (Tell us what results you get.)

    You do realize, of course, that the entire profession of physics research is based on trying to overturn prevailing theories.

    Well, it’s based upon the rigorous acquisition, verification, and publication of scientific knowledge in peer-reviewed archival journals. Sometimes, as you’ve indicated, such new knowledge will “overturn prevailing theories”, as Sadi Carnot did when he showed that “caloric”, an invisible fluid released by the rending of matter, was not the answer to heat-transfer problems. Scientists have a huge incentive to do this, because, like Carnot and Einstein, it will mean enormous accomplishment in their chosen field. But it’s a bit much to make this (admittedly large) motivation the sole basis for “the entire profession of physics research.”

    It’d be like the top Global Warming experts finding ways to show that AGW doesn’t exist, or evolutionists trying to find evidence of creation.

    Good scientists will follow the evidence wherever it leads. Creationism is a dead end, because it does not explain anything, whereas evolution does explain observed traits in species. If the thousands of temperature-recording instruments across the biosphere started to show measurable declines in the earth’s temperature, the “top Global Warming experts” who are honest would revise their theories to suit.

    The most famous theories of physics survived because their advocates were willing to take the time to convince the skeptics, and were willing to do any experiment that might overthrow their own theory. Why not the same level of scrutiny with AGW?

    The correct theories are the ones validated by the data. Your claims about how science works are very odd indeed.

    With a large enough set of mirrors, could you focus the rays of the Sun to heat a point to a temperature higher than the surface of the Sun?

    The Earth transfers heat to the Sun all of the time, via radiation. This mechanism includes heat emitted from the surface of the Earth, and the Sun’s own radiation, reflected back via the albedo of the Earth. The net transfer of energy is from the Sun to the Earth, of course, but radiative energy can (and does) “flow” from a cold place to a hot one.

    demo kid and I had similar motivations for these statements. We wanted to know if you understood the concepts of temperature and radiative heat transfer. Your answers again confirm that you do not.

    BTW, screaming “SHOW ME THE DATA” like some three-year-old does not impress any adult. You’ve already made sweeping, groundless accusations against the characters of the scientists who have collected said data. It takes little imagination to envision you rejecting any data you don’t like on the same basis.

    • Jonathan Gardner Says:

      Jonathan, when the rays from the sun fall upon your skin, why does your skin feel warmer?

      Because heat is transferred from the sun to your skin.

      Your claims about how science works are very odd indeed.

      I know my claims sound odd to you. Again, you are of the mindset that science is a set of memorized facts, while I am of the mindset that science is a process to discern truth from error by invalidating theories.

      I know you are of this mindset because you said “correct theories”. No theory is complete nor correct. In order to prove a theory correct, you would have to observe all possible phenomena, which is more than the entire set of phenomena that occurs in the lifetime of the observable universe. Then you’d have to ensure that every phenomena is in strict accordance with the theory. Such a task is impossible to even contemplate.

      Instead, the best we can do is say things like, “Based on what we know about, this theory appears to be correct.” But we must also append the statement: “Other theories account for the same phenomena we have observed, even if no one has thought of them yet, and are also just as correct as this theory.” A good scientist will also list all the pending experiments that could potentially invalidate the theory, and enthusiastically encourage people to attempt these experiments, in addition to experiments already performed.

      You’ve already made sweeping, groundless accusations against the characters of the scientists who have collected said data.

      When a scientist is shown to have a conflict of interest (as in the case of Dr. Hansen of NASA), when a scientist admits to manipulating the data (as Dr. Jones did on national TV), and when scientists would rather destroy their data than reveal it (as the CRU at East Anglia did), there are hardly any baseless accusations you can make against the character of such people. Such people are not to be trusted, and every statement they make is to be questioned.

      What we have in the Global Warming community is a bunch of sincere scientists following the lead of a handful of corrupt scientists. These corrupt scientists have claimed the equivalent of discovering the Higgs Boson. When scientists approach the professed discoverer with solicitations of hard evidence, and are rebuffed, it is no longer science. It is a scam.

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