A important property of all systems in thermodynamics and statistical mechanics. Entropy characterizes the degree to which the energy of the system is *not* available to do useful work
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How do you prove $S=-\sum p\ln p$?
How does one prove the formula for entropy $S=-\sum p\ln p$?
Obviously systems on the microscopic level are fully determined by the microscopic equations of motion. So if you want to introduce a law ...
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915 views
Maxwell's Demon Constant (Information-Energy equivalence)
New Scientist article: Summon a 'demon' to turn information into energy
The speed of light c converts between space and time and also appears in e=mc^2.
Maxwell's Demon can turn information supplied ...
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658 views
How can it be that the beginning universe had a high temperature and a low entropy at the same time?
The Big Bang theory assumes that our universe started from a very/infinitely dense and extremely/infinitely hot state. But on the other side, it is often claimed that our universe must have been ...
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750 views
How efficient is a desktop computer?
As I understand it (and admittedly it's a weak grasp), a computer processes information irreversibly (AND gates, for example), and therefore has some minimum entropy increase associated with its ...
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623 views
Does the scientific community consider the Loschmidt paradox resolved? If so what is the resolution?
Does the scientific community consider the Loschmidt paradox resolved? If so what is the resolution?
I have never seen dissipation explained, although what I have seen a lot is descriptions of ...
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Why was the universe in a extraordinarily low-entropy state right after the big bang?
Let me start by saying that I have no scientific background whatsoever. I am very interested in science though and I'm currently enjoying Brian Greene's The Fabric of the Cosmos. I'm at chapter 7 and ...
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945 views
What is information?
We're all familiar with basic tenants such as "information cannot be transmitted faster than light" and ideas such as information conservation in scenarios like Hawking radiation (and in general, ...
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7answers
598 views
How is $\frac{dQ}{T}$ measure of randomness of system?
I am studying entropy and its hard for me to catch up what exactly is entropy.
Many articles and books write that entropy is the measure of randomness or disorder of the system. They say when a gas ...
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Why does the low entropy at the big bang require an explanation? (cosmological arrow of time)
I have read Sean Carrol's book. I have listened to Roger Penrose talk on "Before the Big Bang". Both are offering to explain the mystery of low entropy, highly ordered state, at the Big Bang.
Since ...
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3answers
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Do magnets lose their magnetism?
I recently bought some buckyballs, considered to be the world's best selling desk toy. Essentially, they are little, spherical magnets that can form interesting shapes when a bunch of them are used ...
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3answers
295 views
Chance of objects going against greater entropy
My books uses the argument that the multiplicities of a few macrostates in a macroscopic object take up an extraordinarily large share of all possible microstates, such that even over the entire ...
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Is there any proof for the 2nd law of thermodynamics?
Are there any analytical proofs for the 2nd law of thermodynamics?
Or is it based entirely on empirical evidence?
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Can a single classical particle have any entropy?
recently I have had some exchanges with @Marek regarding entropy of a single classical particle.
I always believed that to define entropy one must have some distribution. In Quantum theory, a single ...
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1answer
264 views
Motivation for maximum Renyi/Tsallis entropy
The Conditional limit theorem of Van Campenhout and Cover gives a physical reason for maximizing (Shannon) entropy.
Nowadays, in statistical mechanics, people talk about maximum Renyi/Tsallis entropy ...
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584 views
Ignorance in statistical mechanics
Consider this penny on my desc. It is a particular piece of metal,
well described by statistical mechanics, which assigns to it a state,
namely the density matrix $\rho_0=\frac{1}{Z}e^{-\beta H}$ ...
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2answers
538 views
About Susskind's claim “information is indestructible”
I really can't understand what Leonard Susskind means when he says that information is indestructible.
Is that information really recoverable?
He himself said that entropy is hidden information. ...
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4answers
852 views
Entropy of radiation emitted into space
In several papers I see something equivalent to the following expression for the entropy of radiation given by an astronomical object such as the Sun (assuming the object can be approximated as a ...
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319 views
Is there a mechanism for time symmetry breaking?
Excluding Thermodynamic's arrow of time, all mathematical descriptions of time are symmetric. We know the arrow of time is real and we know the equations describing physics are real so is there any ...
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1answer
158 views
Why is (von Neumann) entropy maximized for an ensemble in thermal equilibrium?
Consider a quantum system in thermal equilibrium with a heat bath. In determining the density operator of the system, the usual procedure is to maximize the von Neumann entropy subject to the ...
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4answers
615 views
What are the arguments towards the Life-and-Entropy relation?
I've heard it from a few people, and I've seen it popup here in the site a couple of times. There seems to be speculation (and studies?) towards this idea, and this is what I've picked up so far:
...
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2answers
248 views
Connection between entropy and energy
An isolated system $A$ has entropy $S_a>0$.
Next, the isolation of $A$ is temporarily violated, and it has entropy reduced $$S_b ~=~ S_a - S,\space\space\space S\leq S_a.$$
Is it true to say: the ...
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2answers
410 views
Energy of unmixing
Mixing of two different fluids is associated with an increase of entropy. Conversely, separation of two gases must be associated with a decrease of the entropy of the two fluids.
Is there a minimum ...
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2answers
224 views
black hole no-hair theorems vs. entropy and surface area
I was revisiting some old popular science books a while ago and two statements struck me as incompatible.
No-hair theorems: a black hole is fully-described by just a few numbers (mass, spin etc) ...
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440 views
Experiments that measure the time a gas takes to reach equilibrium
If you take two ideal gases at different temperatures, and allow them to share energy through heat, they'll eventually reach a thermodynamic equilibrium state that has higher entropy than the ...
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Second law of Thermodynamics: Why is it only “almost” always true that entropy is non-decreasing?
The venerable Wikipedia states the second law of Thermodynamics as such:
...
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2answers
366 views
Does entropy apply to Newton's First Law or does “acted upon” always require an external factor?
First law: Every body remains in a state of rest or uniform motion (constant velocity) unless it is acted upon by an external unbalanced force. This means that in the absence of a non-zero net ...
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3answers
379 views
How bright can we make a sun jar?
A sun jar is an object that stores solar energy in a battery and then releases it during dark hours through a led.
Assume:
a $65cm^2$ solar panel
a 12h/12h light/dark cycle
insolation of ...
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1answer
348 views
Does the heat death of the universe really imply a maximum entropy state *all* of the time? Or most of the time?
Statistically speaking, you're going to still encounter deviations from equilibrium, even though the expected value is equilibrium. But these rare deviations from equilibrium - which are inevitable - ...
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47 views
Would the universe get consumed by blackholes because of entropy?
Since the total entropy of the universe is increasing because of spontaneous processes, black holes form because of entropy (correct me if I'm wrong), and the universe is always expanding, would the ...
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44 views
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349 views
What is the physical or mathematical meaning of the Gibbs-Duhem equation?
The Gibbs-Duhem equation states
$$0~=~SdT-VdP+\sum(N_i d\mu_i),$$
where $\mu$ is the chemical potential. Does it have any mathematical (about intensive parameters) or physical meaning?
