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Heat Death, eh?

  1. Jun 16, 2003 #1
    Yo, d00ds, my Physics book mentions the concept of Heat Death (All the energy in the universe going to an unusable form) but says that it might not be valid if the universe is bounded in certain ways

    Does that just mean that if the universe hits a Big Crunch, it won't experience Heat Death, or if it experiences Cold Death it can't hit Heat Death, or is it something more interesting?

    IS there any way on any level to conceive of a (statistically reasonable) net decrease in entropy?

    Edit: fixed typo
    Last edited: Jun 17, 2003
  2. jcsd
  3. Jun 16, 2003 #2
    what do you mean by unusable form? are you talking about the possibility of an ever expanding universe?

    as of now, everything is on a net increase. maybe you meant net DECREASE.
  4. Jun 17, 2003 #3
    yeah, that's what I meant

    So do you know anything, Maximus?
  5. Jun 17, 2003 #4
    i'm still unclear about what "Hot Death" is or what you mean by unusable energy. also, what is the situation in which this hot death will take place? the big cruch collapse or the other, continually expanding scenerio. i can make a guess that you mean the eternal expansion becuase that's the situation in which entropy will eventually increase to a state where even stars will be unable to make thermonuclear reactions (be rendered "useless" i suppose) and the distribution of the energy of the universe will become too uniform.

    but in a more direct answer to your last question: no. in both scenerios (collapse and no) the net entropy value will increase to a maximum.
  6. Jun 17, 2003 #5


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    Heat death refers to the situation where, in an open universe, everything reaches the same temperature. When this happens, thermodynamics states that there will no longer be any way to move energy around -- and since all biology and technology depend on the heat reservoirs, biology and technology will cease to exist.

    If the universe is closed, it will reach a big crunch (probably) far earlier than it will suffer heat death.

    - Warren
  7. Jun 17, 2003 #6


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    A slight miscommunication, Maximus; and Killa is talking about "Heat Death", not "a hot death". Killa, I have only a ever heard of heat death in association with an open (ever expanding) cosmological model. The idea is that, as space continues to expand, energy continues to spread out until it is evenly distributed. When there are no areas of high concentration for energy to flow from, or low concentration for it to flow to, all motion will stop. This is not restricted to biology and technology only, it will mean the cessation of all movement. When there is no movement of any kind anywhere in the cosmos, it can be said in a very lateral way that kind itself has stopped.

    As for a conceivable scenario in which entropy decreases, this is precisely what many proponents of the "Oscillating Universe" model espouse. When the universe stops expanding, according to this cosmological model, entropy will also stop increasing. As the universe begins to contract, entropy will be reversed.
  8. Jun 17, 2003 #7
    after posting a thread a while back, wondering about the possibility of entropy decrease upon recollapse, we concluded that entropy would not behave so during the Big Crunch. most modern theories about the recollapse agree.
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