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Noob here Order from Disorder

  1. Aug 9, 2012 #1
    I am convinced that order must come from disorder. If there is something to be disordered, then if there is nothing constraining things to become ordered, then it seems axiomatic that some order eventually arises.

    Specifically, with regard to the formation of the Observable universe from a sea of undifferentiated energy.

    (In my mind, I see the universe as a bubble in an eternal pool of swirling, random, chaotic "something" (Something that can create universes such as ours).

    In your best layman's terms, can you help me explain order from disorder to a couple of theists who insist that the 2nd Law makes it impossible, or that in order to have order arise from disorder you need order in the first place, etc.... (the latter may be true, but in a trivial sense - the "laws" of the undifferentiated energy/quantum foam/or whatever it is that exists "outside" of the universe may have some order in this sense: "Be chaotic".)

    Anyhow, looking for some decent explanations on the current understanding of how things could have arose from random chaos.

    Can anyone help me out?

    Thanks in advance.
     
  2. jcsd
  3. Aug 9, 2012 #2

    marcus

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    I hope you get several responses exhibiting several different points of view. I will not try to contribute anything that might help you argue with your two theists, but I will try to present an idea which you yourself might enjoy thinking about.

    Because gravity is normally attractive, the lowest-entropy state is normally the most uniform, with matter distributed evenly throughout all space.

    [you can picture space as either infinite or finite (a boundaryless 3d hypersphere) with matter uniform throughout in either case]

    The 2nd Law is satisfied because, starting from an even distribution, matter will begin to condense into a cobwebby mess under its own self-attractive gravity. Nice computer simulations of this process in George Smoot's TED talk: google "TED Smoot". The formation of structure in the universe is an increase in geometric entropy, under the assumption that gravity is attractive. We are only to the stage of galaxies however. Ultimate entropy would be black holes, but we are not there yet. They have the highest entropy (assuming grav. attractive).

    So condensation, curdling, coagulation, collision and merger proceed apace. Geometry continues to get more and more entropic, as the 2nd Law would wish. :biggrin:

    However there is a catch. Some researchers have found that when they quantize the equation of how geometry evolves (the GR equation) they get that very high density gravity repels instead of attracts. In that situation it is the UNIFORM distribution which is the one with highest entropy and the one favored by the 2nd Law.

    So if the whole coagulated cobwebby mess should COLLAPSE to extreme density it would do two things
    get uniform by action of 2nd Law under repellence
    rebound (because of repellence) and start expanding again, resulting in a new spacetime region.

    At the moment this is a speculative scenario. People are working on determining what the observable effects would be of a bounce from extreme (uniform) density causing the expansion phase we are in. They want to know what the "footprint" of such a bounce would be, so they can tell the astronomers how to look for it.
    Here's a listing of some recent research papers mostly about this, and related:
    http://www-library.desy.de/cgi-bin/spiface/find/hep/www?rawcmd=FIND+%28DK+LOOP+SPACE+AND+%28QUANTUM+GRAVITY+OR+QUANTUM+COSMOLOGY%29+%29+AND+%28GRAVITATIONAL+RADIATION+OR+PRIMORDIAL+OR+inflation+or+POWER+SPECTRUM+OR+COSMIC+BACKGROUND+RADIATION%29+AND+DATE%3E2008&FORMAT=www&SEQUENCE=citecount%28d%29 [Broken]
    The server is slow so you may have to wait for perhaps 15-20 seconds for the list to appear.
     
    Last edited by a moderator: May 6, 2017
  4. Aug 9, 2012 #3
    This comes from a misunderstanding of the second law of thermodynamics. The second law says that entropy must increase with time, not disorder. Entropy is thermodynamics represents how much useful work a thermodynamics system can perform. In statistical mechanics, entropy represents the number of ways you can re-arrange the microstates of a system without affecting the overall macrostate. This is why it appears that the second law says the ordered systems evolve towards disorder, since this is usually the case - water is more disordered than ice, but that isn't the reason ice will tend to become water. It's because there are more ways to re-arrange the molecules in water to keep it the same than for ice, so statistics tells you the ice will become water (assuming it's in an environment that is sufficiently warm).

    However, there are cases where we can entropy isn't exactly disorder. If a random cloud of gas fluctuated into a miniature replica of the statue of liberty, that would seem to be far more ordered. However, the gas fluctuating into a very small and dense packet is less 'ordered', but has far less entropy.

    A gas that is heated to a very high temperature will have a lower entropy, since it will tend towards a lower temperature. Since the early universe was a very hot, dense, state, it had a very, very low entropy. Since our current universe is much cooler, it has a much, much higher entropy. Eventually, the universe will become a cold, dark, de Sitter space, which has an enormously high entropy.

    Why the early universe had such a low entropy is still an open question.
     
  5. Aug 9, 2012 #4

    marcus

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    Yes, still open, but as I just described in my post one conjectured explanation of the low entropy of the early universe is that it resulted from a bounce.
     
  6. Aug 9, 2012 #5

    bcrowell

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    We have a FAQ about this: https://www.physicsforums.com/showthread.php?t=509650 [Broken]
     
    Last edited by a moderator: May 6, 2017
  7. Aug 9, 2012 #6
    ...of course

    A Super Order.
    the "Big Freeze"
    a totally cool universe in the distant future.
     
  8. Aug 10, 2012 #7

    Chalnoth

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    Well, there are generally two separate issues at work here. First, the second law of thermodynamics does not prevent a local decrease in entropy. This particular misunderstanding of the second law of thermodynamics is frequently trotted out in an attempt to say that evolution is wrong, but if this particular misunderstanding were correct, forget evolution: life itself wouldn't be possible! But local decreases in entropy are very common and happen all the time, both naturally and through human intervention. Air conditioning systems, which build up an out-of-equilibrium (and thus low-entropy) state by cooling the inside of a building or vehicle, lower the entropy of the area they are cooling. Moving a car in a particular direction requires a lowering of entropy for the car. The formation of a storm front is a lowering of entropy.

    In each case, the lowering of entropy is allowed because entropy elsewhere increases even more than the local lowering of entropy. With the air conditioning system, you have to pump out a lot of heat to cool the system you want cooled, and that heat represents an increase in entropy. With a vehicle, you change the chemical composition of your fuel, breaking it down from large, complex molecules to a much larger number of simpler molecules. With a storm front, the entropy decrease ultimately comes from the uneven heating of the Earth by the Sun, causing worldwide wind patterns that periodically manifest as storms. The entropy decrease of the Earth is matched by a vastly larger increase of entropy of the Sun.

    If you want to go all the way to talk about origins, well, things get a bit trickier because we don't know that much about the origins of the universe. That initial state did have to be an extremely ordered, low-entropy state, this is true. And right now nobody is quite sure what produced that state. However, there are many ideas. For example, the fact that it was, though ordered, exceedingly tiny (as in, smaller than an atomic nucleus) seems to offer a hint as to how it could have occurred. One idea is that the small amount of dark energy that appears to exist in our universe today (roughly equivalent to the energy of four protons per cubic meter) is an equilibrium state: that far, far in the future, our universe will become completely empty except for this dark energy stuff. At that time, it will be very big, with very high entropy, but with very low entropy per volume. So it isn't a very big jump in entropy any longer for a tiny piece of the universe to sort of "pop", producing a new, low entropy universe.

    But unfortunately this is mostly speculation at the current time. We don't know the correct solution to why the early universe had such a low entropy.
     
  9. Aug 10, 2012 #8
    First all all the second law says that global entropy must increase. Entropy is not quite the same thing as disorder/order.

    Why shouldn't expect order to come from chaos? When things cool they naturally become more ordered, and the universe has been cooling.
     
  10. Aug 10, 2012 #9

    Chalnoth

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    Well, in the most strict sense it is, but only if you define order and disorder very carefully. The problem is that the strict definition of entropy frequently doesn't line up with what we usually think of as order or disorder.

    If you want to get into the nitty-gritty of it, the entropy of a system measures how many different ways you can rearrange the microscopic pieces of the system and still have the same overall appearance. This is why smaller molecules tend to have higher entropy than larger ones, for example: smaller molecules can be rearranged in many more ways. This is why an even mixing of gases is higher in entropy than dividing oxygen into one area and nitrogen in another: when evenly-mixed, you can rearrange the pieces throughout the whole system without changing the overall appearance, while when divided you can only rearrange the oxygen within its own section, the nitrogen within its own.

    Which reminds me, I didn't explain something properly in my somewhat lengthy post above about air conditioners. The entropy increase is not found in the increase in temperature of the surroundings. It's found in the increase in entropy of the fuel at the power plant that supplies the electricity to the air conditioner.

    One interesting bit is that the highest-entropy configuration of our universe is completely empty space. Eventually, this is what our universe will become.
     
  11. Aug 10, 2012 #10
    Exactly. Just to give an example. Imagine some hot gas in empty space. The gas cools and becomes ice crystals. Now there seems to be more order, but if you do the bookkeepping you'll find that the extra "order' of the ice crystals is outweigh by the "disorder" of radiation radiating into space.
     
  12. Aug 10, 2012 #11
    don't need to go to cosmology for this stuff. order from disorder happens all the time. oil and water for instance. shake up a bottle of the stuff. the oil and water separate out into layers. you see this all the time with copolymers folding on themselves in solution to expose the most hydrophilic parts and hide the hydrophobic parts, proteins are just a very complicated copolymer.

    global entropy must increase but local entropy can definitely decrease. what do we mean by *global* though, is the question. Even a galaxy cluster can be considered "local".
     
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