A important extensive property of all systems in thermodynamics, statistical mechanics, and information theory, quantifying their disorder (randomness), i.e., our lack of information about them. It characterizes the degree to which the energy of the system is *not* available to do useful work.

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Gibbs entropy, Clausius' entropy and irreversibility

I have a bunch of doubts and confusions on the concept of entropy which have been bothering me for a while now. The most important ones are of a more technical nature, arisen from the reading of this ...
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96 views

Number theoretic loophole allows alternative definition of entropy?

A bit about the post I apologize for the title. I know it sounds crazy but I could not think of an alternative one which was relevant. I know this is "wild idea" but please read the entire post. ...
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Why is entropy defined as a discrete sum over all microstates in classical case?

I'm reading about statistical definition of entropy, which says $$S=-k_B\sum_ip_i\ln p_i,\tag1$$ where $k_B$ is Boltzmann's constant, and $p_i$ is probability of $i$th state to be occupied. But in ...
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31 views

Have we found a resolution to the Loschmidt paradox? [duplicate]

Loschmidt's Paradox (also known as the Reversibility Paradox) claims that it is not possible to deduce an irreversible process from time-symmetric dynamics such as the classic dynamics. This puts the ...
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2answers
38 views

Can the law of entropy decide our fate? [on hold]

Second law of thermodynamics states that entropy always increases.Elixir of immortal life is a thing humans are longing for since ages.Does this law forbid us from becoming immortal?I mean if disorder ...
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43 views

Why are $S = -k_B\sum_i P_i \ln P_i$ and $S = k_B \ln\Omega$ equivalent?

This might be a silly question, but I don't see the equivalence relation between these two equations. Could somebody explain to me how to derive one from the other? Thanks in advance!
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89 views

The second law of thermodynamics and life on Earth [closed]

The second law of thermodynamics says that order always decreases in a system. The appeareance of life seems to contradict that law, but if we invoke the Sun, everything faals into place again. But ...
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38 views

Does it take the same amount of time, it takes for a system to get to a low-entropy (fluctuation) state from equilibrium, to go in the other way?

Let a system be in a state of fluctuation - a state of low-entropy at $t_0\;.$ Then before and after a sufficiently large but finite time-interval, the system would again be at equilibrium. As the ...
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67 views

Exact differentials and state functions

I was reading a Wiki article on the relationships between heat capacities And during the derivation I came across this formula (and others like it): This equation was used as a tool in a ...
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28 views

Extra 5/2 tau term in chemical potential of a monoatomic ideal gas? [closed]

The chemical potential of an ideal monoatomic gas should be: $\mu = \tau ln \frac {n}{n_Q}$ http://web.mit.edu/ndhillon/www/Teaching/Physics/bookse5.html I get this result if I derive it using the ...
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Entropy is…disorder?

As I read somewhere, it said that the universe is heading toward disorder a.k.a entropy increasing. Now as far as I know from the second law of thermodynamics it states that entropy is indeed ...
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131 views

Is there really a direction of time?

Laws of physics are (almost) time symmetric, so a time-reversed description of a physical process is as qualified as the original one. What's the reason then, that in reality one version seems to ...
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2answers
57 views

Thermodynamics and Newton's second law

Is it correct to say, that the Newton's laws (or a Newtonian system) is reversible if the friction isn't considered (the fact that the time is of second order $\frac{d^2x}{dt^2}$) and an isolated ...
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2answers
91 views

Why can't the entropy of an isolated system decrease? [duplicate]

I read that heat cannot flow from cooler body to hotter because for that entropy of the system becomes negative. Why is that so? Why we cannot have negative entropy?
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18 views

How would one derive a theoretical anti-entropic force equation? [closed]

How would one imagine and formulate a theoretical force that counteracts the second law of thermodynamics? I'm not conceptualizing a force that merely pauses Entropy, but a force that creates order, ...
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91 views

Doesn't this LED created by MIT violate the second law of thermodynamics?

Here is the article I am referring to: http://www.wired.co.uk/news/archive/2012-03/09/230-percent-efficient-leds In their own words (or at least the article writer's), "it appears to draw in heat ...
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39 views

Could the Big Bang be the result of a decrease in entropy?

In my freshman engineering physics class I learned that a decrease in entropy, though hypothetically possible, is less statistically likely than either any or almost any other possible single ...
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35 views

Is uncertainty principle due to entropy? [duplicate]

Is uncertainty principle due to entropy or thermodynamics at all , I was wondering
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1answer
79 views

A mass falls to the ground from a height. What's the change of the entropy of the universe?

A mass $m$ falls to the ground from a height $h$. The temperature $T$ is constant. What's the change of the entropy of the universe? It's an example in Carter's Classical and Statistical ...
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1answer
108 views

What exactly is entropy? Why is it measure of randomness? [duplicate]

What exactly is entropy? Why is it measure of randomness? I have been told Entropy is measure of randomness and it increases everytime randomness increases. What is Randomness? Randomness in what? ...
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68 views

Direction of time in an insulated room

I am puzzled with thought experiment that resembles/is version of Bolzmann's brain-hyphothesis. I could explain it in following way: Let’s assume that we have isolated system full of some stuff, ...
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132 views

Why is the logarithm of the number of all possible states of a system differentiable?

Temperature of a system is defined as $$\left( \frac{\partial \ln(\Omega)}{ \partial E} \right)_{N, X_i} = \frac{1}{kT}$$ Where $\Omega$ is the number of all accessible states (ways) for the system. $ ...
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29 views

is it possible to get energy by lowering temperature

Is it true that I have a pressure meter that is precise enough and measures fast enough, if I use it to measure the pressure of atmosphere, the measure will vary because gas molecules hit my pressure ...
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143 views

Why doesn't the separation of particles by mass via gravity decrease entropy?

Let's say we've got a fluid of heavy and light particles inside a cubical flask, which is initially shaken up so that the density of heavy particles is uniform everywhere. Let's also say that these ...
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78 views

What determines time flow? (arrow of time) [closed]

I've been reading up on the arrow of time and there is one thing that is being omitted from every explanation that I've found: time flow. I am rewording this question to make it clearer. From the ...
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Fundamentals of atomic bonding [closed]

Are these basic statements about atoms and bonding correct: atoms are at their lowest energy state when they have no bonds, existing as single atoms it always requires energy to form any ...
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29 views

Calculating Microcanonical Entropy in Molecular Dynamics

As a beginning, I am simulating Argon liquid at 94 K and characterising as it is done by the Rahman's first paper on Molecular Dynamics. After going through the first two chapters of Art of Molecular ...
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63 views

Is it a law of physics that all machines will break?

The question sounds kinda dumb when I say it out loud but at the same time I'm very curious. When things break, is it solely due to an intrinsic design flaw or is it due to entropy? And is the ...
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35 views

Is there a relation between complexity of a system and entropy?

Disclamer: I'm not a physics professional, so pardon me if the question is stupid/incomperhensible/generally doesn't make sense. And I've googled it, but didn't find an answer. Getting to the point, ...
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23 views

If $\Delta Q/ T$ approximates the entropy change of some transition, is it inclusive of the entropy from volume change?

At the point of a transition where latent heat must be added to some substance, entropy change can be approximated by $\Delta Q/ T$. At these points, the volume of the substance also increases, which ...
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52 views

In an equilibrium of two systems, why is not true that $\frac{\delta S_{1}}{\delta N_{1}} = \frac{\delta S_{2}}{\delta N_{2}}$?

Why is not true that $\frac{\delta S_{1}}{\delta N_{1}} = \frac{\delta S_{2}}{\delta N_{2}}$ across two systems that exchange particles? It is true, instead, that $\frac{\delta F_{1}}{\delta N_{1}} = ...
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Does the Entropy of the Visible Universe Decrease?

My understanding is that the entropy in a closed system increases. However, I would also assume that the number of particles in the open system of a visible universe decreases because of accelerated ...
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32 views

Could one, practically or hypothetically, capture energy from heat using magnetic fields? [closed]

I have had this idea, and I'm not sure if it would work. Heat is a form of chaotic kinetic energy, right?. Would it be possible to create a magnetic field within a gas or liquid so that when the ...
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38 views

Is there any relation between the entropy of a system and the kinetic energy of molecules in the system?

The kinetic energy of the molecules in the system increases when we provide heat to the system,thereby increasing its temperature under certain conditions. Similarly providing heat to a liquid ...
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40 views

Energy/entropy in transport of molecules across cell membranes

I'm asking a "Maxwell's Demon" question. I've read statements that sorting molecules and sending them to one side or the other of a barrier requires work, but none of these statements have explained ...
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109 views

Is black hole formation reversible if physics law holds even in time reverse?

As we know many situations still fulfill physics law if time is reversed, such as particle collision. But how about black hole formation? Suppose a star is turning to a black hole and starts to have ...
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15 views

Does 'Entropy-Sated' mean that no 'Order' can be produced from a black hole?

I believe I have a misconception somewhere that I need help to clear up. No-Hair indicates that a black hole created from highly ordered matter with low entropy reaches the same final state as ...
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1answer
49 views

Calculation of Entropy of Debye Solid at High T

I am calculating the kmolar entropy of a Debye solid at low temperature ($T << \theta_D$) and high temperature ($T >> \theta_D$). For the low temperature, I use $U = U_0 + \frac{9 k_B ...
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Current status of nonextensive statistical mechanics

A version of the maximum entropy principle is the following. $$\max_{P}~~~ -\sum_i p_i\log p_i$$ subject to all probability distributions $P=\{p_i\}$ satisfying $$\sum_i p_i \epsilon_i = U.$$ ...
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104 views

Quantum mechanics and second law of thermodynamics

Recently I came across this idea of Gibbs that, it is the coarse-grained entropy that always increases, whereas the fine-grained remains a constant. So classically, coarse graining refuses us some ...
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Does the second law of thermodynamics imply a spacetime beginning of the universe?

Recently I have been studying thermodynamics and I noticed a article by a religious person which says that the second law of thermodynamics proves that the universe had a beginning. A spacetime one. ...
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77 views

entropy and dispersion

If I know the positions and the speeds of each particle in a box over the time, how can I compute the entropy ? (I`m making a simulation where I want to show that the disperion of the particles over ...
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93 views

Can entropy be regarded as energy dispersal?

In several answers here the claim has been made that thermodynamic entropy can be regarded as energy dispersion. See, in particular here, and here and here. This is apparently the pet theory of a ...
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29 views

Entropy changes of water

I have a few questions regarding entropy and water. Suppose you cool down water so that it freezes at $273.15K$. How is entropy positive in this case? I have a feeling it may have to do with the ...
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1answer
77 views

Is entropy increase in disorder or 'energy-dispersal'? [duplicate]

My teacher explained entropy like this: It is increase in disorderliness. Take a glass jar put three layers of blue marbles in it then put three further layer of red marbles, now shake the ...
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Why must the total change in entropy be 0 for a heat cycle to be as efficient as possible?

If $\Delta S_{total}$ were not zero, then heat flow would take place at different temperatures. It is easy to see why this is true by examining the opposite: that when heat flow takes place at the ...
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1answer
103 views

If time is like space, why entropy always increases with time? [duplicate]

If time is like space, why entropy always increases with time I should not be able to distinguish whether I am going forwards or backwards in time. As entropy always increase with time. I can ...
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Calculate the entropy using microcanonical ensemble

$$Ω=\sum_{n=0}^{N-\frac{E}{\epsilon}} \frac{Ν!}{\left(\frac{N-n-\frac{E}{\epsilon}}{2}\right)!\left(\frac{N-n+\frac{E}{\epsilon}}{2}\right)!n!}$$ I am supposed to calculate the above sum using first ...
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56 views

Is the law of maximum entropy production the same as principle of least action?

I just have read about the law of maximum entropy production. Someone has idolized it enough to make an whole website just for it: http://www.lawofmaximumentropyproduction.com/ A system will ...
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Why doesn't the entropy increase when two similar gases mix with each other?

Entropy increases when two substances mix with each other. For example, the entropy of mixing of two different gases are given by $$\Delta S= 2Nk\ln\frac{V_f}{V_i}\;.$$ But, the entropy doesn't ...