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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807 views
What is the relationship between Energy, Entropy, and Information?
What is the relationship between Energy, Entropy, and Information?
I read this - What Is Energy? Where did it come from? - and the top answer says that 'energy' is an abstract number that is a ...
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1answer
239 views
Loschmidt's paradox - really a paradox? [duplicate]
Is Loschmidt's paradox a paradox even today?
In other words, is the paradox resolved or not?
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3answers
840 views
Does radiation change entropy?
Are there entropy changes associated with the transmission of energy from the sun to the earth? Does radiation differ from other modes of heat transfer with respect to the entropy changes?
Are the ...
3
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1answer
223 views
Wasn't the Hawking Paradox solved by Einstein?
I just watched a BBC Horizon episode where they talked about the Hawking Paradox. They mentioned a controversy about information being lost but I couldn't get my head around this.
Black hole ...
3
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2answers
557 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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0answers
44 views
What other factors effect the ability of a propigating field of pressure in a gaseous medium to predict gravitational collapse?
What other factors effect the ability of a propigating field of pressure in a gaseous medium to predict gravitational collapse?
Will the only factor influencing the Speed of Sound in this medium be ...
7
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1answer
206 views
Area law for Entropy in Loop Quantum Gravity
In connection with the long saga of the (claimed) microscopic
calculations of the Hawking-Bekenstein entropy in (3+1) Loop Quantum Gravity (LQG) and related approaches I have the following question: ...
8
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0answers
153 views
How is the logarithmic correction to the entropy of a non extremal black hole derived?
I`ve just read, that for non extremal black holes, there exists a logarithmic (and other) correction(s) to the well known term proportional to the area of the horizon such that
$S = \frac{A}{4G} + K ...
9
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2answers
233 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) ...
2
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0answers
222 views
Influence of Joe Rosen work, is it marginal, or significantly accepted?
I have prepared a paper that relies on work of Joe Rosen on symmetry (e.g. "Symmetry Rules: How Science and Nature Are Founded on Symmetry"). I am wondering about his influence. For example, when I ...
0
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0answers
52 views
The entropy of a static granular mixture
Regarding static granular mixtures (pile of sand - particles with different sizes), is there an expression that will give me the entropy of such a mixture? I am interested in finding the entropy of ...
6
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3answers
311 views
Confusion regarding entropy, reference papers request
1.a In paragraph at Wikipedia/Entropy it is stated:
This is because energy supplied at a high temperature (i.e. with low entropy)
tends to be more useful than the same amount of energy
...
3
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1answer
250 views
Relation between external magnetic field intensity H, magnetisation M and the entropy?
How are the external magnetic field intensity H, magnetisation M and the entropy related to each other? i.e. if I change the magnetic field intensity by dH what will be the change in entropy dS in ...
3
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2answers
270 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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1answer
70 views
System moves away from equilibrium $\rightarrow$ it has energy added?
Suppose there is an isolated system $A$ at time $(-\infty, t_1)$, whose entropy is $S=S_{max}$, i.e. it is at thermodynamical equilibrium.
Between moments $[t_1, t_2)$ the isolation is violated and ...
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1answer
106 views
Reference paper to support information — energy relation ($kT \ln2 \rm\frac{J}{bit}$)
In answer to Maxwell's Demon Constant (Information-Energy equivalence) there is stated that one bit of information allows to perform $kT \cdot \ln2$ Joules of work. Which paper supports the ...
2
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1answer
93 views
Is a closed system receiving heat guaranteed to have entropy below maximum?
Isolated system will preserve its entropy unchanged (for fully reversible system) or it will increase its entropy (for system with irreversible processes).
For a closed system, it can receive energy ...
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1answer
305 views
How did the energy/entropy/volume/pressure/temperature relationship exist at the Big Bang and how did it evolve thereafter?
According to the current Big Bang with inflation cosmological model?
I was under the mistaken impression that there was very low volume, very high temperature/pressure, very low entropy and the Big ...
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2answers
362 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?
3
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3answers
185 views
Does the second law of thermodynamics tell me how the entropy changes?
In thermodynamics I can e.g. compute the properties of ideal gases with certain energies $U_1,U_2$ in boxes with certain volumes $V_1$ and $V_2$. Say I have two such boxes and they have some specific ...
6
votes
1answer
174 views
Does measurement, quantum in particular, always increase the total entropy?
Measurement of a quantum observable (in an appropriate, old-fashioned sense) necessarily involves coupling to a system with a macroscopically large number of degrees of freedom.
Entanglement with this ...
4
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2answers
225 views
What's the validity of the thermodynamic definition of entropy?
Thermodynamic Entropy Variation is defined as
$$\Delta S = \int_i^f \frac{dQ}{T},$$
where $i$ and $f$ are the initial and final states of the process.
My question is: does this equation apply to ...
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1answer
85 views
What is a qualitative explanation for order of values of standard entropies of formation for isomers of hexane?
I have literature values for the standard enthalpy and Gibbs energy changes of formation at 298 K, $\Delta H_\text{f}^o$ and $\Delta G_\text{f}^o$, for product in the ideal gas state. Since $G=H-TS$ ...
2
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1answer
64 views
Is there an abstract notion of heat within a microscopical system?
The microstates of a system are said to be unobservable. I can introduce the entropy as a measure of the number of microstates, which lead to the same macroscopic variables. So in this detailed ...
3
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2answers
124 views
What physical processes may underly the collisional term in the Boltzmann equation, and how do they increase entropy?
Consider particles interacting only by long-range (inverse square law) forces, either attractive or repulsive. I am comfortable with the idea that their behavior may be described by the collsionless ...
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4answers
606 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
145 views
Entropy change in a cycle with two isochoric and two adiabatic processes [closed]
Prove that the change of Entropy in a cycle with two isochoric and two adiabatic processes is 0.
How can I prove that? Thanks!
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2answers
509 views
Are information conservation and energy conservation related?
as evident from the title, are both, conservation of energy and conservation of information two sides of the same coin??
Is there something more to the hypothesis of hawking's radiation other than ...
3
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2answers
377 views
How long will my fridge magnet stay attached to my fridge?
I have a 500 gram neodymium magnet. It is stuck to my fridge. With the constant pull of gravity trying to pull it off how long would it stay attached to fridge? For arguments sake lets say my fridge ...
3
votes
2answers
703 views
What meaning do changes in the absolute value of Gibbs free energy have in a simple expansion process?
Below is a simple representation of the thermodynamics of a steam turbine. Stream kinetic and potential energy changes are neglected and no other type of non-PV work is done besides shaft work. ...
8
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4answers
417 views
Did really everything begin with a state with very low entropy?
As emphasized by Penrose many years ago, cosmology can only make sense if the world
started in a state of exceptionally low entropy. The low entropy starting point is the
ultimate reason that the ...
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5answers
1k views
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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4answers
627 views
What does third law of thermodynamics tell us?
I just have a question concerning the third law of thermodynamics.
The third law describes that the entropy should be a well defined constant if the system reaches the ground state which depends ...
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3answers
247 views
Is a world with constant/decreasing entropy theoretically impossible?
I'm not 110% sure exactly what I mean by this question. It was sparked by a friend who said he wished the law of entropy were reversed, so he wouldn't have to worry about cleaning the bathroom.
...
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2answers
281 views
Statistical interpretation of Entropy
I'm preparing my statistical physics course, and while writing the lecture notes it says that a system with non distinguishable particles has much less microstates asociated with a particular ...
2
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1answer
245 views
Joining the definitions of entropy
$\int \frac{Q_{rev}}{T} = \Delta(k_B\ln\Omega)=\Delta S$
Could anyone give some definite proof for this?
I was able to prove that the two definitions of change in entropy are equivalent for an ...
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1answer
370 views
Deriving an Expression for Entropy
How to derive an expression for entropy in form of
$S = \ln \Omega$
from the form
$\displaystyle{S = - \sum_i \; p_i \ln p_i}$ ?
That is the last formula taken as a definition of entropy.
Just a ...
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4answers
2k views
Why does maximal entropy imply equilibrium?
From a purely thermodynamical point of view, why does that entropy have to be a maximum at equilibrium? Say there is equilibrium, i.e. no net heat flow, why can the entropy not be sitting at a ...
5
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1answer
219 views
Energy formula for separating $O_2$ from mixture of $O_2$, $NH_3$ and $H_2O$
I have a physics problem I'd like to make sure I get correct.
The practical aspect of this problem is that the photosynthetic efficiency of algae is inhibited with dissolved O2 in the growth medium, ...
6
votes
6answers
651 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 ...
2
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1answer
240 views
How to choose the right units to compute the phase space volume in classical statistical mechanics?
Without the natural unit $\hbar$, why doesn't it seem to be a problem for Statistical Physics to define
$$S=k_B\ log(\Omega)\ ?$$
If $\Omega$ is given in one unit system and I switch to other units ...
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1answer
181 views
Maxwell's Demon bug, trapdoor space and time
What about the size of the door (space) and how long has it to be opened (time)?
I think Maxwell's demon would have a problem with space, if the door is too wide (more than one particle size), then ...
3
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3answers
221 views
Simple question about a gas in a box with a moving wall
David Albert is a philosopher of Science at Columbia. His book "Time and Chance" includes this example (p 36).
A gas is confined on one side of a box with a removable wall. "Draw the wall out, ...
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1answer
101 views
Entropy of a mass arrangement around the earth
An mind experiment, taking the entire Earth as an isolated system
Then this is the initial state:
N masses are distributed around the earth, at different height.
(for example we can use a single ...
3
votes
0answers
241 views
How does lifting an object effect its entropy
I have figured out that:
When photons leak out from a container, the entropy of the photon collection increases, because each photon has a different escape time.
Photons that have leaked out from a ...
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3answers
477 views
Can heat be extracted and concentrated? [closed]
If one could devise an answer to this question, electricity would be free for everyones disposal. (seems like a good dream but in reality free energy will be this worlds downfall)
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1answer
130 views
Do all closed systems, only considering kinematic/mechanical principles, exhibit time reversal symmetry?
It makes a lot of sense to me to imagine a cannonball flying through space as not so much experiencing a macroscopic non-conservative drag force, but as pushing a bunch of air molecules and giving ...
6
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2answers
190 views
Renyi entropy in physical systems
We know that the Shannon entropy $H(P)=- k_{\mathrm{B}}\sum_i p_i \ln p_i$ is mostly the entropy of the thermodynamic systems.
Does the Renyi measure $H_{\alpha}(P)=\frac{1}{1-\alpha}\log \sum ...
5
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5answers
2k views
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 ...
4
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3answers
686 views
How to understand temperatures of different degrees of freedom?
So I'm reading this book, where after the preface and before the models there is a section called General Notions and Essential Quantities, which introduce some things I don't understand. They regard ...
