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Thread: Experiment makes energy from information

  1. #1 Experiment makes energy from information 
    Forum Isotope Bunbury's Avatar
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    Does this make sense? If so can someone explain it more clearly than the article does?

    http://content.usatoday.com/communit...-information/1


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  3. #2 Re: Experiment makes energy from information 
    . DrRocket's Avatar
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    Quote Originally Posted by Bunbury
    Does this make sense? If so can someone explain it more clearly than the article does?

    http://content.usatoday.com/communit...-information/1
    As is typical with reporters the story is sensationalized.

    Basically the idea is that the second law of thermodynamics is statistical, not fundamental, and that one can reduce entropy by something like a Maxwell's demon -- culling higher energy objects from a population of objects, which then allows one to extract work.

    A lot of details are missing from the story. You might want to look for an ArXiv preprint on this experiment from the scientists reported to have performed the experiment. That ought to have the straight skinny.


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  4. #3  
    Forum Isotope Bunbury's Avatar
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    Dr.Rocket, thanks for the reply.

    Here’s a much better description of the experiment, but I don’t see what is supposed to be remarkable about it. The molecule gains potential energy, but in order to achieve that gain an electric field is manipulated by researchers, both of which consume vastly more energy than the tiny gain made by the electron. My immediate response is “so what?” The second law remains unchallenged.

    Seems I’m missing something.

    http://www.livescience.com/strangene...on-101114.html
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  5. #4  
    . DrRocket's Avatar
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    Quote Originally Posted by Bunbury
    Dr.Rocket, thanks for the reply.

    Here’s a much better description of the experiment, but I don’t see what is supposed to be remarkable about it. The molecule gains potential energy, but in order to achieve that gain an electric field is manipulated by researchers, both of which consume vastly more energy than the tiny gain made by the electron. My immediate response is “so what?” The second law remains unchallenged.

    Seems I’m missing something.

    http://www.livescience.com/strangene...on-101114.html
    I don't think that you are missing anything.
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  6. #5  
    Veracity Vigilante inow's Avatar
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    There's a physicist whose blog I read. He's a member at another site where I've frequented... A bright guy with a good demeanor who does work on fountain clocks and extreme cooling. He posted on this topic this time last week.


    http://blogs.scienceforums.net/swansont/archives/7080

    That seems more reasonable — storing information (and all information needs to be stored) requires energy, so there is energy in information storage. But what is being presented as “information” is just the state of a system; one could just as easily say there is energy in e.g. an electron’s orientation in a magnetic field (or the location of a polystyrene bead, as in this case), and skip the discussion about information.

    It sounds like a version of the Brownian ratchet, where a paddle would spin in only one direction from random collisions, because the ratchet would impede motion in the other direction. It fails because the ratchet, too, would be subject to collisions, and fail to work if everything were at the same temperature. Here, the mechanical ratchet has been replaced by an electric field, which is not in thermal equilibrium. You expend energy determining when to change the field.

    More at the link.


    As a side note... the "creationist" to whom he is referring in his opening is our very own Cypress who was banned from this site some time ago. Ahh... Small world.
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  7. #6  
    Forum Isotope Bunbury's Avatar
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    Inow, there is a decent Discover article linked in the blog you linked to. Having read the Discover article I now think I understand the point of the experiment, so thanks for that. I wonder what practical applications might develop from this.

    But going back to Maxwell's original demon, this other article says:

    http://blog.joerg.heber.name/2010/11...of-the-bottle/

    The door is controlled by a small ‘demon‘ that lets fast-moving gas molecules go into the right half, and leaves slow ones in the left. The left box would cool down, and the right one heats up. Overall, the box is more ordered than before. If the demon itself doesn’t use up any energy (which can be done), entropy would decrease, right?
    How can the demon open and close the door without using any energy?
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  8. #7  
    . DrRocket's Avatar
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    Quote Originally Posted by inow
    There's a physicist whose blog I read. He's a member at another site where I've frequented... A bright guy with a good demeanor who does work on fountain clocks and extreme cooling. He posted on this topic this time last week.


    http://blogs.scienceforums.net/swansont/archives/7080

    That seems more reasonable — storing information (and all information needs to be stored) requires energy, so there is energy in information storage. But what is being presented as “information” is just the state of a system; one could just as easily say there is energy in e.g. an electron’s orientation in a magnetic field (or the location of a polystyrene bead, as in this case), and skip the discussion about information.

    It sounds like a version of the Brownian ratchet, where a paddle would spin in only one direction from random collisions, because the ratchet would impede motion in the other direction. It fails because the ratchet, too, would be subject to collisions, and fail to work if everything were at the same temperature. Here, the mechanical ratchet has been replaced by an electric field, which is not in thermal equilibrium. You expend energy determining when to change the field.

    More at the link.


    As a side note... the "creationist" to whom he is referring in his opening is our very own Cypress who was banned from this site some time ago. Ahh... Small world.
    Swanson is a pretty good guy.
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  9. #8  
    Veracity Vigilante inow's Avatar
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    Quote Originally Posted by DrRocket
    Swanson is a pretty good guy.
    Yes, he certainly is. He's not a bad cartoonist, either.




    Quote Originally Posted by Bunbury
    But going back to Maxwell's original demon, this other article says:

    http://blog.joerg.heber.name/2010/11...of-the-bottle/

    The door is controlled by a small ‘demon‘ that lets fast-moving gas molecules go into the right half, and leaves slow ones in the left. The left box would cool down, and the right one heats up. Overall, the box is more ordered than before. If the demon itself doesn’t use up any energy (which can be done), entropy would decrease, right?
    How can the demon open and close the door without using any energy?
    This is a bit beyond my depth, but the wiki write up is pretty good. My take away (in response to your question) is that 1) this is an imaginary demon opening and closing the door, so that part is not subject to normal laws of physics, and 2) to open the door based on velocity, a measurement must be made (to determine velocity) and that measurement increases the disorder of the system.

    More here... again... not my forte:

    http://en.wikipedia.org/wiki/Maxwell%27s_demon
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  10. #9  
    Forum Freshman .o:0|O|0:o.'s Avatar
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    Quote Originally Posted by inow
    http://en.wikipedia.org/wiki/Maxwell%27s_demon
    A further point to add under Criticisms in that article is that entropy increases from t=0, with "hot" particles losing or transferring energy to "cold" particles even before they are sorted between the chambers. The demon would not only need to expend energy to observe and select, put would require a much more immediate way of segregating the hot and cold particles.

    .o:0|O|0:o.
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  11. #10  
    Forum Isotope Bunbury's Avatar
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    this is an imaginary demon opening and closing the door, so that part is not subject to normal laws of physics
    My question is why would a brilliant mind (Maxwell) invoke demons, or for that matter gods in a scientific thought experiment. Why not just say "Then a miracle happens."

    And on that note I'm off to the kitchen. Happy Thanksgiving.
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  12. #11  
    . DrRocket's Avatar
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    Quote Originally Posted by Bunbury
    this is an imaginary demon opening and closing the door, so that part is not subject to normal laws of physics
    My question is why would a brilliant mind (Maxwell) invoke demons, or for that matter gods in a scientific thought experiment. Why not just say "Then a miracle happens."

    And on that note I'm off to the kitchen. Happy Thanksgiving.
    I think the name "demon" came from someone else. Maxwell was proposong a "thought experiment" as a test of a physical theory. That is quite common and often productive. Einstein was famous for that -- in his development of relativity and in his correspondence with Bohr regarding perceived problems with quantum mechanics.
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  13. #12  
    Veracity Vigilante inow's Avatar
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    Quote Originally Posted by Bunbury
    My question is why would a brilliant mind (Maxwell) invoke demons, or for that matter gods in a scientific thought experiment. Why not just say "Then a miracle happens."
    I found your question interesting, so starting swinging the google bat and doing some reading.

    As it turns out, it was not Maxwell who called it a demon. That came later.


    http://iopscience.iop.org/0031-9120/...pdf/pe7111.pdf

    Maxwell did not call his creature a 'demon'; the term was a later invention. Maxwell's demon was never a supernatural being, although it did appear...
    ... although it did appear to be blocked with a pay wall, so I couldn't keep reading.



    So, from the same wiki link above:

    In the experiment, an imaginary container is divided into two parts by an insulated wall, with a door that can be opened and closed by what came to be called "Maxwell's Demon".

    <...>

    When Maxwell introduced the concept, in his letters to colleagues, and in his book, Theory of Heat, he described it as a "finite being."

    The thought experiment first appeared in a letter Maxwell wrote to Peter Guthrie Tait on 11 December 1867. It appeared again in a letter to John William Strutt in 1870, before it was presented to the public in Maxwell's 1871 book on thermodynamics titled Theory of Heat.

    William Thompson (Lord Kelvin) was the first to use the word "demon" for Maxwell's concept, in the journal Nature in 1874, and implied that he intended the mediating, rather than malevolent, context of the word.


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

    In 1866, he formulated statistically, independently of Ludwig Boltzmann, the Maxwell–Boltzmann kinetic theory of gases. His formula, called the Maxwell distribution, gives the fraction of gas molecules moving at a specified velocity at any given temperature. In the kinetic theory, temperatures and heat involve only molecular movement. This approach generalized the previously established laws of thermodynamics and explained existing observations and experiments in a better way than had been achieved previously. Maxwell's work on thermodynamics led him to devise the Gedankenexperiment (thought experiment) that came to be known as Maxwell's demon.

    Here is Maxwell's original description:

    ... if we conceive of a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are as essentially finite as our own, would be able to do what is impossible to us. For we have seen that molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the slower molecules to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics....

    Okay... I spent too much time with that. I'm seriously bored. I perhaps need to get into the kitchen and help, as well. Cheers.
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