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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Can the law of entropy decide our fate? [closed]

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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1answer
229 views

Explicit form of the entropy production in hydrodynamics

I'm trying to understand how hydrodynamics arise from a precise, mathematical formulation of thermodynamics, learning mostly from Landau's "Hydrodynamics". So Landau starts from formulating the ...
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4answers
194 views

What is the cause for the inclusion of 'thermal equilibrium' in the statement of Ergodic hypothesis?

This is the fundamental assumption of statistical mechanics: In an isolated system in thermal equilibrium $^1$, all accessible microstates are equally probable. But why does it mention the ...
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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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340 views

How can heat turn into light

I am confused about how hot surfaces can radiate light to their surroundings. When I shine a light on a surface the light turns to heat spontaneously, and when I leave that hot surface it radiates ...
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What is the conceptual difference between Gibbs and Boltzmann entropies?

In simple words what is the conceptual difference between Gibbs and Boltzmann entropies? Gibbs entropy: $S=-k_B\sum p_i\ln p_i$ Boltzmann entropy: $S=-k_B\ln \Omega$
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1answer
48 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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104 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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39 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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90 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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8answers
4k views

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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2answers
124 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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36 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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4answers
226 views

How can there be entropy change in this system?

How can there be an entropy change in this system? Suppose if I have a system consisting of liquid water, $1\, \mathrm{kg}$ at $290\,\mathrm{K}$, I stir it, and do say, $10\, \mathrm{J}$ of work on ...
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2answers
141 views

Entropy / Structure Relations

I want to check on the validity of the following objective definition of order. Is it correct? Is there a more rigorous statement of this concept? The further a system is from its maximum ...
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148 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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68 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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1answer
49 views

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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0answers
19 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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115 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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114 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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0answers
49 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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1answer
97 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
111 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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2answers
932 views

Difficulties with understanding total entropy change and unavailabillty

Of course, I know the fact that the entropy of an isolated system never decreases. Neverthless what makes me confused about the entropy(or change of entropy) of an isolated system is the explanation ...
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1answer
139 views

Is entropy related to Poincare recurrence time?

One of the ideas involved in the concept of entropy is that nature tends from order to disorder in isolated systems. But we even know that Poincare recurrence time also is a particular time after ...
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50 views

Behavior of maximum entropy states in a closed system?

As I understand it, entropy is a measure of the number of permutations of microstates of a system possible, without changing the observed 'macrostate variables' / measurements or properties of a ...
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2answers
2k views

Physics-based derivation of the formula for entropy

I am looking for a derivation of the formula $$S~=~-\Sigma_ip_i \log (p_i).$$ for entropy, from first principles. I only wish to assume the laws of physics, and without involving concepts in ...
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1answer
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Motivation for the use of Tsallis entropy

Every now and again I hear something about Tsallis entropy, $$ S_q(\{p_i\}) = \frac{1}{q-1}\left( 1- \sum_i p_i^q \right), \tag{1} $$ and I decided to finally get around to investigating it. I haven't ...
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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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3answers
93 views

How can a reversible adiabatic expansion not increase entropy?

In the second stage of the Carnot cycle, a gas is thermally insulated and allowed to expand and do work on the piston. I understand the reason people give is that because entropy is $\,dS = \,dQ/T$ ...
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164 views

Entropy of loops in the PV plane

The change in entropy of the Carnot and reversible cycles is said to be 0. Several other loops are supposed to have a non-negative change in entropy. This presents 2 problems which I cannot ...
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202 views

The black hole paradox

I recently read in the news that Stephen Hawking claims to have solved the Black Hole Information paradox. I researched a bit about the paradox and the research that Stephen Hawking did to solve it. ...
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1answer
130 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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1answer
70 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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3answers
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Where is the flaw in this machine that decreases the entropy of a closed system?

I was thinking about a completely unrelated problem (Quantum Field Theory Peskin & Schroeder kind of unrelated!) when the diagram below sprang into my mind for no apparent reason. After some ...
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1answer
32 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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323 views

Information Preservation and Burning Books

I recently read an article in the NY Times called A Black Hole Mystery Wrapped in a Firewall Paradox. I really liked the article, but reading one quote immediately made me think of asking Physics.SE a ...
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84 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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52 views

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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53 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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1answer
80 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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39 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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1answer
216 views

Reference paper to support information — energy relation $\left(kT \ln2 \rm\frac{J}{bit}\right)\;.$

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 ...
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596 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 ...
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1answer
262 views

Confusions regarding entropy

Help, I am terribly confused about entropy. On the one hand, I am taught at school that a substance such is an ice/solid has a lower entropy than its gaseous equivalent and that a process such as ...
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539 views

Axioms behind entropy!

The concept of entropy is very ubiquitous, we learn about its uses starting from Information Theory (Shannon entropy) up to its basic definition in statistical mechanics in terms of number of ...
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79 views

Entropy of ideal gas with finite volume

I know that the entropy of an ideal gas is given by the Sackur-Tetrode equation, but is there also a way to take into account that even the ideal gas will acquire some volume $v_0$? Or is it then just ...
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25 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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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}} = ...