1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Does the entropy of the universe as a whole change?

  1. Mar 29, 2015 #1
    Does the universe as a whole ever change from being the universe as a whole? Does it ever break into pieces and cease being the universe?

    And if anything (like the universe) never changed its state, wouldn't that mean its entropy never changed? Are there any constant thermodynamic properties that can be assigned to the universe as a whole?
  2. jcsd
  3. Mar 29, 2015 #2


    User Avatar
    Gold Member

    No. Why would you expect the universe to "break into pieces". Besides "universe" means "everything there is, so the pieces would STILL be the universe (but it's still a non-starter).
  4. Mar 29, 2015 #3
    I'm thinking of how the universe may be getting bigger at the same time gravity is drawing things together. Wouldn't gravity have a tendency to counteract the entropy of expansion?
  5. Mar 29, 2015 #4


    User Avatar
    Gold Member

    I have no idea what you mean. Dark Energy (whatever it is) has made it so that no only is the universe expanding, the rate of expansion is accelerating. Gravity was overcome some 5 billion years ago. Your late.
  6. Mar 29, 2015 #5
    Or, as I understand it, wave functions are unitary and conserve information. So if we were to write a wave function for the entire universe, what else besides the universe would the universe interact with to collapse the entire universe? If nothing, then the information content of the universe would remain constant, right?
  7. Mar 30, 2015 #6
    The wave function of the entire universe need not collapse all. The portion of the universe which is in causal contact with you collapses via interacting with you, hence, you observe a universe that is comparable with your existence. This is called the "strong anthropic principal". It is by no means a widely agreed upon principal but it is something you might be interested in learning about.

    Entropy of the universe is always increasing.

    Thermodynamic principals are a bit hard to apply to the universe as a whole. If you define the universe as everything that is in causal contact then the universe consists of everything within a certain radius of a chosen object. Your universe and my universe are different because each of us is at the center of a slightly different sphere. Discussing the universe as a whole cannot be done without reference to the things within it, such as a high red-shift galaxy for example. But if we discus a high red-shift galaxy we have to acknowledge that, being in the center of a different sphere, it is in causal contact with things that we are not, and not in causal contact with things that we are.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Does the entropy of the universe as a whole change?
  1. Change in entropy (Replies: 8)