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Time and entropy

Time and entropy - Physics Forum

Time and entropy - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 02-10-2006, 01:10 PM
Don1
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Default Time and entropy



What is the relationship between time and entropy?

Why is entropy considered as a running down; toward a heat death of the
energy contained in the sun, stars, and planets?

Why can't energy be increasing?

Don

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  #2  
Old 02-10-2006, 02:33 PM
Sam Wormley
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Default Time and entropy

Don1 wrote:

The total mass-energy of the universe was fixed in the big bang.

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  #3  
Old 02-10-2006, 06:58 PM
Don1
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Default Time and entropy

Sam Wormley wrote:

What's unfixing it? Why can't entropy remain the same, or be decreasing?

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  #4  
Old 02-10-2006, 07:05 PM
PD
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Default Time and entropy


Don1 wrote:

There isn't a fixed one, other than as time increases, then the *total*
entropy of the universe increases.


Heat death is not the *lowering* of energy, it's the homogenizing of
energy. The only reason we can do anything at all (motors, chemistry,
biology) is that energy is more concentrated in some places than in
others. It's the controlled gating of that energy from concentrated
spots to less concentrated spots that results in work, heat flow,
chemical processes.


I suppose it could be, but it doesn't seem to be, experimentally.
That's why we took note of energy as an interesting quantity that seems
to remain constant, and why we guessed that it is conserved.


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  #5  
Old 02-10-2006, 10:28 PM
Sam Wormley
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Default Time and entropy

Don1 wrote:



Entropy is a measure of the disorder of a system and is defined
by equations in this link
[Only registered users see links. ]

The mass-energy of a system can remain constant while
the entropy can change.
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  #6  
Old 02-11-2006, 01:13 AM
Steve Pope
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Default Time and entropy

Don1 <[Only registered users see links. ]> wrote:


They're certainly gaining potential energy since the universe
is expanding. I believe total mass plus energy is conserved --
something to do with the universe cooling.

Steve
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  #7  
Old 02-11-2006, 03:57 AM
Allan Murray
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Default Time and entropy


It wasn't my high school teaching (or university, that matter)
that made me beleive that gravity (only) attracts. I don't know what
planet you are living on. But it (so far) seems to be an experimentally
observable fact.

Allan Murray
[Only registered users see links. ]



I bet they still think that quantifying


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  #8  
Old 02-11-2006, 05:08 AM
Allan Murray
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Default Time and entropy

Because:

"Energy spontaneously tends to flow only from being concentrated in one
place
to becoming diffused or dispersed and spread out."

See Prof. Frank Lambert's website for a good (modern) explanation
[Only registered users see links. ]


Allan Murray
[Only registered users see links. ]



"Don1" <[Only registered users see links. ]> wrote in message
news:1139577043.244539.97550@o13g2000cwo.googlegro ups.com...


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  #9  
Old 02-19-2006, 02:47 AM
Two
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Default Time and entropy

"Don1" <[Only registered users see links. ]> wrote in message
news:1139577043.244539.97550@o13g2000cwo.googlegro ups.com...

The local universe is expanding at the speed of light, FAPP. It is
impossible for something to exceed (go faster than) the rate at which space
is being created. All things are involved in this expansion but are
'measured' locally without consulting the rate of change. It's called Time's
Arrow.

Imagine seeing the local universe from a position which saw all things
happening in the context of expansion; entropy as we consider it would not
be relevant.

Never mind the breaking glass returning to its original state metaphors. Way
too macro to be pertinent.


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  #10  
Old 02-19-2006, 02:49 AM
Two
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Default Time and entropy

"Sam Wormley" <[Only registered users see links. ]> wrote in message
news:Ur8Hf.767758$_o.193853@attbi_s71...


Keep in mind the necessary artificiality of the 'system' to make the
equations work.


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