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!

Entropy and news stars born

  1. Aug 6, 2007 #1
    According to the second law of TD, entropy is increasing in the whole universe.
    Then how could you explain the fact that from a chaotic state of dust and gas remnants of a supernova, gravity causes all them to gather together to form new stars which are less chaotic thus having less entropy than the former state?
    And this happens ALL THE TIME through t the universe.
  2. jcsd
  3. Aug 6, 2007 #2
    Local entropy can decrease for various reasons, but there is always a corresponding increase in the larger system.

    What do you mean by "the whole universe?" Last I checked, no one knew for sure if there is such a thing. Is the universe a closed system? Or an open one?

    It is probably better when learning physics to stick to observable phenomena, and "the whole universe" is not observable.
  4. Aug 6, 2007 #3
    I think you'll find it said (in the published literature) that the highest entropy state is the black hole (consider the no hair theorem versus the number of unknowable microstates), and that homogeneously distributed dust is not very chaotic.
  5. Aug 6, 2007 #4

    Claude Bile

    User Avatar
    Science Advisor

    Are you sure stars and the radiation they emit have less entropy than the gas they originate from? You will probably need to qualify this assertion a little better because it isn't obvious to me that this is true.

  6. Aug 6, 2007 #5
    I suspect it's a superficial thing, "entropy" isn't always visible in the same manner. In an ideal gas (with particles uncoupled from each other), the most probable macro-state is well known to be the least clumped and most uniform. Throw in the force of gravitational interactions and that result is just no longer the case (the uniform distribution is balanced in unstable equilibrium). Wonder if there is a similar "paradox" with ferromagnetism vs diamagnetism?
    Last edited: Aug 6, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Entropy and news stars born
  1. Star ? (Replies: 7)