Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

2nd law of thermodynamics and the big bang

  1. Jul 25, 2007 #1
    I read from Victor Stenger's books that maximum entropy exists in blackholes or singularities. So, at the Big bang, the universe had its maximum entropy. Does it mean that entropy has DECREASED since then? Stenger explained that since the universe expands, it has more space for entropy. However, this doesn't really make sense to me.
  2. jcsd
  3. Jul 25, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    Could you give a precise reference please? It was my understanding that the early universe contained a small entropy, which has increased as time increased (this is something like that thermodynamical arrow of time). I'd like to take a look at the given reference though, or at least an exact quotation, before commenting on it (especially since I'm not too sure what's meant by "the maximum entropy is found in a black hole).
  4. Jul 27, 2007 #3


    User Avatar
    Science Advisor
    Gold Member

    Further complicating matters is whether or not the laws of thermodynamics are a transcendental property of the 'oververse', or an emergent property of this universe. If an emergent property [which is an arguably difficult proposition to avoid], it is conceivable this is the only kind of universe possible - i.e., one whose fundamental properties happen to be sufficiently fine tuned to enable a very long lived incarnation [the only kind where observers like us could emerge]. In that sense, the quest for a TOE is an 18th century classical hangover. We will be forever stuck with some number [greater than one] of fundamental constants that defy all efforts to further reduce. I find it curious the current number of fundamental constants of nature [26] is the same as the number of dimension proposed by heterotic string theory.
    Last edited: Jul 27, 2007
  5. Jul 27, 2007 #4
    totally in line with you. I would add the question, "isn't it a fact that, so far, adding more spacetime dimensions has done nothing in reducing the degrees of freedom ?".
    Having said that, if we had a theory that could enable to derive the 26 parameters from one, would you say that this gets closer in the way of a TOE ?
  6. Jul 28, 2007 #5
    Have a look at Victor Stenger's book called "God: the failed hypothesis", in which he argues that although at the big bang, the universe had maximum entropy, the universe has ever since expanded so it has more space to "throw" its entropy. :surprised
  7. Jul 29, 2007 #6


    User Avatar
    Science Advisor
    Gold Member

    I think, chrisina, we need to think outside the box when it comes to defining what constitutes a 'dimension'. Classical spacetime, IMO, is emergent, not fundamental, arising from quantum imbalances in the initial conditions. I would argue that quantum principles are transcendental properties of the 'oververse', but have no preferred value. Think of it as looking for dimensions in all the wrong places.
    Last edited: Jul 29, 2007
  8. Dec 27, 2007 #7
    actually in a black hole the event horizon is compared to the antropy. antropy increases as disorder increases.in the same way matter falling inside a blackhole is the disorder and the increasing eventhorizon is the antropy.we can say that the disorder(acretion disc)in a blackhole increases the antropy(eventhorizon).another example the total antropy of a system is the sum of the reactant antropies of the two systems. similarly if two blackholes collide the event horizon of the resultant blackhole will be the sum of the event horizons of the colliding blackholes.therefore it is said that black has the max antropy.thanks for reading
  9. Dec 28, 2007 #8


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    Unfortunately I don't have Stenger's book handy, so i cannot follow this argument.
    there is a talk about the Big Bang and entropy and the 2nd Law by Roger Penrose,
    that is free online (voice and slides).

    Penrose says that from the standpoint of someone in our universe looking back at the Big Bang, conditions at that time had very LOW ENTROPY. He says people are mistaken to say it was high entropy because that does not count the extremely low entropy of the gravitational field at that era.

    It is a very clear, wide-audience talk. I respect Penrose a lot although i don't always understand his arguments, or agree in every case (where i do follow.)

    the talk can be googled using information like "Penrose before the big bang"
    Last edited: Dec 28, 2007
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook