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How the first two laws of thermodynamics apply to order

  1. Jun 3, 2009 #1
    I know that the first law states that matter is can't be created or destroyed but in the second it mentions that the universe is moving towards entropy. But does not the universe have a moment of creation and if that is the case then what would you say the matter would have been before the moment of the big bang. I am doing research for a book and I would like to see what others think of order and chaos.
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  3. Jun 4, 2009 #2


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    Energy cannot be created or destroyed. We now know that matter can, as it's a form of energy - which can be converted into other forms of energy.

    "Amount of disorder" is a common, but pretty bad definition of entropy. A better one is "degrees of freedom", another one is "the amount of energy in a system that can be converted into work".

    I'm not sure the concept of 'before' the creation of the universe has meaning.
  4. Jun 4, 2009 #3


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    This definition is pretty bad too, worse than "disorder." Entropy is not an amount of energy. And a high-entropy system is not more capable of producing work.
  5. Jun 4, 2009 #4
    I think that if one refers back to the logistic function/ sigmoid curve and using the first law that the universe had to have a beginning or to say it a different way the moment that universe changed from whatever form it was to what it is to day. It had to have a moment of birth and that means that if it had a birth it must have a death.
  6. Jun 4, 2009 #5
    As has previously been mentioned "beginning", "end" and "disorder" as english words really convey no understanding of what's going on. Physics is a theoretical framework expressed in mathematics. However, since the vast majority of people do not have sufficient mathematical proficiency to understand theory so it then becomes necessary, when conversing with the layman public, to try and provide the "jist" of what's going on in english words, which, unfortunately, creates a whole lot of trouble. For example, entropy IS a measure of the number of microstates available to a given system, it is expressed as k*ln(omega) where k is a constant (called the Boltzmann constant) and omega is the number of microstates available to the system. Now that's what Entropy IS. Now, at some point, someone, who didn't understand quantum mechanics of statistical mechanics demanded that the concept be expressed in a much simpler way, and then confusion begins. I think the whole "disorder" idea came from a certain line of reasoning that went something like this:
    -a microstate is a possible configuration of a given system, a system with low entropy has few micro states and thus can only be in a small number of states (for example, the simplest of systems might be a single confined electron which can only be in two states, either it has a spin up or a spin down)
    -therefore, a system of low entropy can kinda be thought to be confined/simple/ordered (once again, none of these words truly encapsalate the idea)
    -and thus if a low entropy system is 'ordered' then a high entropy system is 'disordered' and voila you have the oft misunderstood idea that entropy is a measure of disorder. However, for example, if one considers a 'dirty room' with clothes on the floor, bed unmade, etc. one might, in english, say it is disordered and one might then say if the same room was 'clean' and all the clothes folded and put in drawers and the bed made then it is more 'ordered'. However, the entropy of the room is still the same, it has neither gained or lost possible states you just switched it between them. So you see how an english explanation gets you into trouble.

    So to sum up, entropy is a measure of the number of states available to a system. That's what it is
  7. Jun 4, 2009 #6
    Now as for notions of "beginning" and "end" of the universe things are even more complicated (in fact a great deal so) because in our common layman discussions of time we simply think of past, present, future and time progressing at 1 second per second. However, time is a far more complicated creature, for example, the RATE at which time progresses is a local (i.e. it depends on where you are and how close you are to other masses) and relative (it also depends on how fast you are moving relative to someone else's clock) quantity and quite malleable. These were the concepts that Einstein introduced, what are called General and Special relativity, about 100 years ago. Since then these once foreign and quite unbelievable concepts have been worked into the mathematical framework of physics and the resulting effects are observed everyday (for example, the workings of large particle accelerators like LHC at Cern are only really possible because of time dilation (otherwise reaction products would decay too quickly to collide) and communication satellites need to consider relativity when calculating their position in order to be accurate enough to make things like GPS possible). However, for the large layman public the fact that time does dilate (both by relative motion and presence of mass (i.e. gravity)) often does not register which makes explaining things like the big bang very difficult (I've had many people inform me that the big bang was when all the matter in the universe was stuck at a single point in space before exploding outwards. This is not it at all I'd correct them, it is rather that all of SPACE was of point-like extent and then... but then I have to stop and think because to say "and then" really does not convey the fact that TIME is also dilating". Needless to say if you find yourself trying to explain a BEGINNING of TIME then you know the flexibility of our spoken language has failed at conveying the necessary concepts.
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