4 ms·

Your perspective is incorrect. Physical entropy governs real physical processes. Simple example: why ice melts in a warm room. More subtle example: why cords g

• refactor_master 1y ago
  I think original post is confused exactly because of “tangled chords” analogies. Something being “messy” in our daily lives can be a bit subjective, so using the same analogies for natural forces may seem a tad counterintuitive actually. Maybe it would be more fitting to say that it just so happens that our human definition of “messy” aligns with entropy, and not that someone decided what messy atoms look like. I’d say a bucket of water is more neat than a bucket of ice, macroscopically.
• HelloNurse 1y ago
  But "disordered" and "ordered" states are just what we define them to be: for example, cords are "tangled" only because we would prefer arrangements of cords with less knots, and knots form because someone didn't handle the cords carefully. Physical processes are "real", but entropy is a figment.
  • dekken_ 1y ago
    I believe you are correct. Entropy is not a physical quantity, it is a measure of how far a system is from equilibrium. Lots of people talk about order/disorder or macro and micro states, not realizing these are things we've invented and aren't physical in nature.
    • kgwgk 1y ago
      > Entropy is not a physical quantity, it is a measure of how far a system is from equilibrium. That’s funny because the original thermodynamic entropy is defined only for systems in equilibrium.
      • deleted 1y ago
        [deleted]
      • dekken_ 1y ago
        from who? Clausius? It doesn't make a lot of sense to me because a system at equilibrium, cannot go undergo any further diffusion, so there's no potential "entropy increase" Maybe the issue, is that, like an ideal gas, a perfect equilibrium just doesn't occur.
• ludwik 1y ago
  > there are far more ways for a system to be disordered than ordered I'm a complete layman when it comes to physics, so forgive me if this is naive — but aren't "ordered" and "disordered" concepts tied to human perception or cognition? It always seemed to me that we call something "ordered" when we can find a pattern in it, and "disordered" when we can't. Different people or cultures might be able to recognize patterns in different states. So while I agree that "there are more ways for a system to be disordered than ordered," I would have thought that's a property of how humans perceive the world, not necessarily a fundamental truth about the universe
  • hackinthebochs 1y ago
    Think minimum description length. Low entropy states require fewer terms to fully describe than high entropy states. This is an objective property of the system.
    • amelius 1y ago
      In a deterministic system you can just use the time as a way to describe a state, if you started from a known state.
    • sat_solver 1y ago
      You're thinking of information entropy, which is not the same concept as entropy in physics. An ice cube in a warm room can be described using a minimum description length as "ice cube in a warm room" (or a crystal structure inside a fluid space), but if you wait until the heat death of the universe, you just have "a warm room" (a smooth fluid space), which will have an even shorter mdl. Von Neuman should never have repurposed the term entropy from physics. Entropy confuses a lot of people, including me.
      • nick__m 1y ago
        And somewhat surprisingly the heat death of the universe is the maximal entropy state. Because there are an infinite number of microstates (all the particles are interchangeable) that lead to the same macrostate: nothing happening for ever!
• deleted 1y ago
  [deleted]
• meindnoch 1y ago
  >Simple example: why ice melts in a warm room. Ice melting is simply the water molecules gaining enough kinetic energy (from collisions with the surrounding air molecules) that they break the bonds that held them in the ice crystal lattice. But at the microscopic level it's still just water molecules acting according to Newton's laws of motion (forgetting about quantum effects of course). Now, back on the topic of the article: consider a system of 2 particles separated by some distance. Do they experience gravity? Of course they do. They start falling towards the midpoint between them. But where is entropy in this picture? How do you even define entropy for a system of 2 particles?
  • ccozan 1y ago
    Let me try to answer. Let's say the particles are experiencing gravity as a natural entropy phenomena. They will attract until they become so close that they are now seen as a single particle. The new system has a lower entropy and a higher gravity than before. Explanation seems very rudimentary but that is the gist of the theory. From my point of view, I might add the layer of information density. Every quantum fluctuation is an event and the more particles the more information is produced in a defined space volume. But there is no theory of information that is linked to the physics so ...that let me leave as that :).
    • stephenitis 1y ago
      Can you define quantum fluctuation?
  • tsimionescu 1y ago
    > But where is entropy in this picture? How do you even define entropy for a system of 2 particles? The answer is that this doesn't happen in a system with only 2 particles. The idea of gravity as an entropic phenomenon is that you introduce some other kind of particle that permeates spacetime, so there is no system that only contains 2 particles. You may use some idea like virtual particles from quantum field theory, or you may define "quanta of space time" as something that is not technically a particle but basically works like one in a handwavy sense. But the basic point of these entropy based theories is to explain gravity, and typcilaly spacetime itself, as an emergent result of a collection of numerous objects of some kind. This necessarily means that they don't make sense if applied to idealized systems with very few objects - which is why they typically posit such isolated systems simply can't actually exist in reality.
• aeonik 1y ago
  My take, for what it's worth, Entropy isn’t always the driver of physical change, sometimes it’s just a map. Sometimes that map is highly isomorphic to the physical process, like in gas diffusion or smoke dispersion. In those cases, entropy doesn't just describe what happened, it predicts it. The microstates and the probabilities align tightly with what’s physically unfolding. Entropy is the engine. But other times, like when ice melts, entropy is a summary, not a cause. The real drivers are bond energies and phase thresholds. Entropy increases, yes, but only because the system overcame physical constraints that entropy alone can’t explain. In this case, entropy is the receipt, not the mechanism. So the key idea is this: entropy’s usefulness depends on how well it “sees” the real degrees of freedom that matter. When it aligns closely with the substrate, it feels like a law. When it doesn't, it’s more like coarse bookkeeping after the fact. The second law of thermodynamics is most “real” when entropy is the process. Otherwise, it’s a statistical summary of deeper physical causes.
  • lumost 1y ago
    What makes entropy interesting is that you can describe many physical processes through analysis of the systems degrees of freedom. This pattern repeats regularly despite the systems being radically different. So you can interpret entropy as being about as real as potential energy or newtons laws. Very useful for calculation, subject to evolution laws which are common across all systems - but potentially gives way as an approximation under a finer grained view (although the finer grained view is also subject to the same rules)
  • buggyipadmettoo 1y ago
    Just swap out "my take, for what it's worth" For "according to ChatGPT"
    • aeonik 1y ago
      I don't like your comment, it's pretty low effort, and your tearing down a lot of effort that I have put into learning about physics and entropy over the years. I came up with the psuedonym Aeonik Chaos circa 2010 because my studies of Chaos Theory and Entropy left a very deep impact on me. I've been thinking about entropy ever since my dad, a biochemist, embryologist, and doctor told me he thought that entropy was behind the secret of life. That event was over 30 years ago. I've been thinking about this stuff very deeply for a very long time. So no, it's not according to ChatGPT, it's just my current take, but I don't to come out and say "this is how it is", because entropy has a way of being sneaky, I've been wrong about theories of entropy way too many times to pretend to be some authority on the matter. Hence, this is my take, take it or leave it. By the way, I love using ChatGPT to learn more about science and math, and have it act as sounding board for ideas. It's great for learning and diving deeper into this stuff.
• geon 1y ago
  It has been suggested that time too is derived from entropy. At least the single-directionality of it. That’d make entropy one of the most real phenomena in physics.
• kgwgk 1y ago
  > Physical entropy governs real physical processes > the measure is not the same thing as the phenomenon it describes. There is some tension between those claims. The latter seems to support the parent comment’s remark questioning whether a “fundamental physical interaction could follow from entropy”. It seems more appropriate to say that entropy follows from the physical interaction - not to be confused with the measure used to describe it. One may say that pressure is an entropic force and physical entropy governs the real physical process of gas expanding within a piston. However, one may also say that it’s the kinetic energy of the gas molecules what governs the physical process - which arguably is a more fundamental and satisfactory explanation.
• woopsn 1y ago
  You need some additional assumptions. Only near equilibrium / thermodynamic limit is system linear in entropy. What governs physical processes such as you mention is conservation, dynamics pushing equipartition of energy - but outside that regime these are no longer "theorems".
• quantadev 1y ago
  Bekenstein-Hawking entropy goes up when an Event Horizon increases in radius. That means some mass "falling onto" an EH. So this implies, if our universe is actually a 3D EH, both time and increasing entropy can be explained by one thing: Increasing size of our EH. That is, mass falling onto our EH from outside our universe. It also happens to elegantly replace the Big Bang nonsense theory with something that makes sense. It explains the universe expansion as well. Assuming our universe is a 3D EH makes lots of things make sense that don't otherwise make sense.