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Author Topic: Heat death violates Entropy?  (Read 3057 times)

Offline pshmell

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Heat death violates Entropy?
« on: 25/07/2009 23:58:10 »
I can't see how there would ever be a heat-death of the Universe.

It would violate the second law of thermodynamics! Kind of paradoxical, really, since the second law of thermodynamics is what led to the heat-death theory.
But if heat-death occurs, and everything is in total equilibrium, then entropy is no longer increasing: it has reached its goal. But the 'goal' is illusory, really. Think limits, in algebra: the curve is always getting closer and closer to zero, but it never quite makes it. Heat death would be the curve reaching zero, and that just can't happen.


 

Offline JP

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Heat death violates Entropy?
« Reply #1 on: 26/07/2009 03:53:07 »
It can after infinite time.
 

Offline pshmell

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Heat death violates Entropy?
« Reply #2 on: 26/07/2009 07:23:35 »
So in other words... never?
 

Offline JP

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Heat death violates Entropy?
« Reply #3 on: 26/07/2009 14:13:00 »
If you're assuming a steady-state universe, the idea of heat death is a limiting process, like you said.  You can't classically reach the point of "maximum entropy" in finite time, but since time in the universe would go on forever, no matter how close you wanted to get to heat death, I could always tell you a time that would get you closer.  The idea of heat death is valid as a limiting process. 
 

Offline pshmell

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Heat death violates Entropy?
« Reply #4 on: 26/07/2009 16:37:55 »
The idea of heat death is valid as a limiting process. 

Exactly! And as it would violate the fundamentals of calculus for a limiting function to ever reach the limit it is approaching, it would violate the fundamentals of thermodynamics for the entropy of the Universe to ever reach a impassable maximum.
 

Offline Soul Surfer

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Heat death violates Entropy?
« Reply #5 on: 26/07/2009 17:06:46 »
The actual process of the heat death of our universe is quite interesting Stephen Hawking in a paper published many years ago on the topic suggested that the whole universe would eventually merge into a single black hole which would itself evaporate over an unthinkably long period of time.  However accelerating expansion and big rip cosmologies could considerably shorten this period
 

Offline pshmell

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Heat death violates Entropy?
« Reply #6 on: 26/07/2009 17:31:47 »
The actual process of the heat death of our universe is quite interesting Stephen Hawking in a paper published many years ago on the topic suggested that the whole universe would eventually merge into a single black hole which would itself evaporate over an unthinkably long period of time.  However accelerating expansion and big rip cosmologies could considerably shorten this period

Imagine it this way: the Universe is this push and pull, ebb and flow: entropy vs. gravity. While entropy is always increasing, gravity is as well. And in the form of black holes, the Universe will eventually coalesce into one. But JUST before it gets to that singularity, that zero-volume, infinite density singularity (it never ACTUALLY reaches that limit, jpetrucelli, just like entropy never reaches its limit), the quantum gravitational forces become repulsive rather than attractive, and entropy takes back over in a marvelous explosion we know as a Big Bang. And so it goes, expand, contract, expand, contract, etc.
 

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Heat death violates Entropy?
« Reply #6 on: 26/07/2009 17:31:47 »

 

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