How can we think about entropy in these situations? To my knowledge all of these structures are born out of gravitational interaction. However, it would seem that the formation of these more organized structures conceptually violates the second law of thermodynamics. Is this dilemma arisen from my flawed understanding of thermodynamics or are these structures actually in a way defying an increase in entropy?
31536
Please forgive: I am a layman when it comes to physics and cosmology, and have tried finding an answer to this that I can understand, with no luck.  As I understand it, the solar system evolved from a massive molecular cloud. To me, this seems to break the second law of thermodynamics, as I think it suggests order from disorder.  I know there must be something wrong with my logic, but am really stuck.  Can anyone explain this one in layman's terms?  (Posting to both "Astronomy" and "Physics", as it seems to overlap these subjects)
113565
I'm new here, so apologies if the question doesn't sound meaningful considering what physics is supposed to answer. I don't have a physics or mathematics background, but I did learn a few things about entropy and the different possible fates of an expanding universe from other forums.   Now, assuming the heat death "fate" is where the universe is heading towards, asymptotically reaching towards a thermal equilibrium, will it stay in a state of equilibrium forever? or the will the "arrow of time" cease pointing sharply towards the future since decrease in entropy becomes likelier when a state of near maximal entropy is achieved (I'm guessing here) ?  The wiki article on this states the number of years that would take for a random quantum fluctuation to perhaps recreate another "big bang" and restart the universe as $10^{10^{10^{56 }}}$ . I realise that's a RIDICULOUS amount of time to even comprehend, nevertheless it is still a physical possibility and $10^{10^{10^{56}} }$ years are only a tiny fraction of time when compared to an infinite amount of time.  Finally what I want to ask: Is reality a one time phase transition from a vague potential with maximal degrees of freedom (big bang) to a crisp actuality with maximal constraint (heat death) with asymmetric, unidirectional time or is it infinite cyclic with symmetric time that reverses itself (by means of highly improbable, but physically not impossible mechanisms) after a finite period of time?   I suspect this may be a borderline philosophy question, but figured might as well give it a try here before posting in more relevant forums. Thanks.
67975
Is there a physical reason why not to think that instead of space expanding, all physical constants and parameters are shrinking (including of course the instruments we use to measure the constants) and space is static, or is it a case of Occam's razor?
8006
It is well known that quantum mechanics and (general) relativity do not fit well. I am wondering whether it is possible to make a list of contradictions or problems between them?  E.g. relativity theory uses a space-time continuum, while quantum theory uses discrete states.  I am not merely looking for a solution or rebuttal of such opposites, more for a survey of the field out of interest.
93201
Can one derive Newton's  second and third laws from the first law or   first and third laws from the second law or  first and second  laws from the third  law  I think Newton's laws of motions are independent to each other. They can not be derived from one another. Please share the idea.
76828
The nature of the experiment has been discussed , but my main question is this: is there any theory that has predicted the results of this experiment or are we completely clueless about what's happening? In other words, have we come up with a new hypothetical interaction that could explain the results?
45177
I'm having trouble understanding how a  (not the  that is generated as a result but the material itself) work. The particles are aligned in a specific direction to give rise to force but I don't see how this alignment gives rise to "attraction" or force.
18170
Could someone provide me with a mathematical proof of why, a system with an absolute  (such that of a spin system) is  than any system with a positive temperature (in the sense that if a negative-temperature system and a positive-temperature system come in contact, heat will flow from the negative- to the positive-temperature system).
108587
Why does the nature always prefer low energy and maximum entropy?  I've just learned electrostatics and I still have no idea why like charges repel each other.  I don't quite understand why U has to be minimum. Can someone explain?
86967
There are people proposing the possibility of using entropic force to explain the gravity force between objects. The emphasis is that entropy is more fundamental than energy. It is the closest study as entropy is closely related to information. What is Mathematical formulation of ?     ... It implies that gravity is not a fundamental interaction, but an emergent phenomenon which arises from the statistical behavior of microscopic degrees of freedom encoded on a holographic screen...
47015
recently wrote an  on  in collisionless , where at least one topic discussed confused me.  Besides discussing the issue of how a process can be microscopically  and macroscopically , he mentions something regarding a "entropy-preserving relaxation mechanism" that is irreversible.  Am I missing something?  I think the article is suggesting that something can preserve entropy but still be irreversible.  This begs the following questions:   Are  and irreversibility synonymous? Or are they distinct entities each with their own fundamental properties?
51567
I am assuming there are two constituents that obliterate our current model of physics;   that it's infinitely dense that it's infinitely small   Please correct me if I am wrong.
107185
My question pertains to a possible inconsistency between the first law of thermodynamics and the general expansion of space itself.   First, the knowns:   Space itself has, and continues to expand - the acceleration aspect is not relevant to the discussion Empty space in a vacuum has intrinsic energy - some refer to this as dark energy Energy cannot be created or destroyed as per the first law of thermodynamics   Concisely, what is the source of energy that is imbued into this "new" space?  A few speculations:   The energy for this process is taken from something other source that already exists inside or outside the known universe. The energy for this process is created from nothing, thus violating the first law. If space itself is quantized, perhaps the planck length itself is expanding across the universe, giving the appearance that new space is created, but actually it is just the space "particles" themselves that are expanding.  At some critical point this expanding space would have observable consequences for our own scale of existence.   These ponderings can also be applied to the big bang theory - either energy was created at some point (from nothing) or existence of anything has been an infinite cycle into the past. Either way we are dealing with infinites. Create something from nothing and you will find infinites cropping into your calculations.
82301
Intro:  In completing , he presents an experiment (go to 42:44) which leaves me baffled.    Experiment:  (I recommend watching the video; see link above.)   There is a $2$ kg block with 2 identical strings attached to it: one at the top, the other at the bottom. The top string is attached to a "ceiling", and the bottom to a "floor". Professor Lewin "stretches" the system (by pulling on the bottom string) with the block not accelerating. One string snaps.     Prediction:   Initially, the top string has a tension of approximately $20$ N, to counter the force of gravity. The bottom string has no tension at all. Then, when Lewin pulls the bottom string, it gains some tension $n$ N. To counter act the force exerted by the bottom string, the top string exerts now $20 + n$ N. I assume that the string with more force will give out sooner, leading me to conclude that the top string will break.     Results:  (This was conducted by Lewin, not me; see link above.)   Trial 1: Bottom string breaks. Trial 2: Top string breaks. Trial 3: Bottom string breaks.     Additional Notes:  The results don't seem consistent. If I was right, I'd expect all 3 experiments to be right; conversely, if I was wrong, I'd expect all 3 experiments wrong, with one exception: the results are more-less random and one result isn't preferred over the other.    Question:        Why was my prediction incorrect?   Was there a flaw in my logic?   Why were the results inconsistent?
110692
Here is something that I never understood about Maxwell's demon paradox : in order to contradict the second law of thermodynamics, the demon must open and close the door without doing any work... But how is that possible ?   I know it is just a thought experiment but still, as I see it, it just shows (by contraposition) that, if you assume the second principle to hold true, then there cannot exist a device that will open and close the door in this way without doing any actual work (for instance, there will necessarily be some friction or whatever which will creates some work..)  Seeing things this way there is no paradox and it only states, as a corollary of the second law, that such a demon cannot exist...  Obviously, I am missing something here since there seems to be much more to this thought experiment than that... I would be extremely grateful if someone would take the time to explain to me where I am mistaken ! :)  Thanks !
69522
Scientists say that entropy of our universe is increasing as it is expanding and our universe is cooling down gradually from the time of its birth. If something is getting cooler and cooler, then how can it become more random (entropy increase) with the passage of time? According to laws of thermodynamics, at absolute zero temperature, the entropy is zero. That means as we go down and down to the temperature scale entropy must decrease, but why is it not happening in the case of our universe?
91829
Layman here,  Stumbling through some physics stack posts and started reading the Wikipedia for the . In it, it states     The very earliest universe was so hot, or energetic, that initially no   matter particles existed or could exist except perhaps fleetingly, and   the forces we see around us today were believed to be merged into one   unified force. Space-time itself expanded during an inflationary epoch   due to the immensity of the energies involved. Gradually the immense   energies cooled – still to a temperature inconceivably hot compared to   any we see around us now, but sufficiently to allow forces to   gradually undergo symmetry breaking, a kind of repeated condensation   from one status quo to another, leading finally to the separation of   the strong force from the electroweak force and the first particles.   Where is the "immense energy" going to when it is "cooled"? Is there now no "immense energy"?