This is for the same reason that you can, from a perfectly fair coin, get an arbitrarily long sequence of "heads" or "tails", e.g. Moreover, so long as their movements are truly and thoroughly random (that is, enough to make the system "ergodic"), there will always be a nonzero probability that by pure luck a configuration arbitrarily close to this will happen, and that probability for such will approach 1 given unlimited time. Such movements are entirely possible thanks to the time-reversal symmetry of the laws of physics. To the best of our knowledge, there is nothing at all to prevent the atoms and molecules in the Earth from all moving to conspire "just right" so that at a particular point in time, they give it a huge "kick" that sends it reeling. Yes, it is, but it is, indeed, as you say, "extremely unlikely" in a very specific sense. These reorganized molecules would themselves be local areas of low entropy, further altering the manner in which entropy/energy is dissipated through the system. Along the way, areas of uneven energy cause molecules and atoms to organize themselves in a manner which is conducive to (a) the medium of energy, and (b) the manner in which entropy equilibrium is reached (the environment). As energy from the star is added to say, the ocean of a planet, the entropy increases locally before being dissipated through the medium. I am currently working on a personal theory (inspired by the work of Jarzynski and Crook) that the second law of thermodynamics is the most fundamentally important reason that life exists that the formation of amino acids, and complex life is a necessary byproduct in every solar system (with the proper precursors) in order to approach equilibrium.Īny solar system as an isolated system (each star is so far apart from the next, it's isolated enough) and entropy cannot decrease over time, even as the entropy of the star is reducing through nuclear fusion. The sun, a region of very high energy, directly interacts with the Earth. In order for any life on Earth to exist in a manner that reduces entropy so much so that 7+ billion humans can exist, build cities that remain rigid, and coexist with trillions of other organisms, somewhere outside of the system there must be a region of spacetime with a very high entropy interacting with this system. The solar system is a great example for visualization purposes, although it is itself a subsystem of a larger system, ad infinitum. a region who's entropy is constantly being reduced. It is crucial distinction to make, between a region of lower relative energy vs. Although a local reduction of entropy does not increase the entropy of it's surroundings, but rather the constant reduction of entropy in the surroundings enable these local low entropy states to exist in order to approach equilibrium. This means that this reaction will show a decrease in entropy.Note: Was going to comment on Wang's answer, but Without the 50 reputation yet, I'd like to build off their example of living organisms being a local system with a decrease in entropy, and how this is balanced out.Īs Wang pointed out about living organisms:īut although they can reduce entropy locally, they must increase the entropy of their surroundings by at least as much in the process. Has a total of #3# moles of gas on the reactants' side and only #2# moles of gas on the products' side. #"more moles of gas on the products' side " -> " increase in entropy"#.#"more moles of gas on the reactants' side " -> " decrease in entropy"#.When it comes to reactions that involve gases, you will have In such cases, look at the total number of moles of gas present on the two sides of the chemical equation. Now, the first two reactions involve gaseous reactants and gaseous products. I'm not going to go into why that is the case, just keep in mind that it is possible. This is not a very good example because there are solids that can be dissolved in water to a decrease in entropy. #"NaClO"_ (3(s)) -> "Na"_ ((aq))^(+) + "ClO"_ (3(aq))^(-)#Ī solid is being dissolved to produce solvated ions, so in general, you can say that entropy will increase. #"CH"_ 3"OH"_ ((l)) -> "CO"_ ((g)) + 2"H"_ (2(g))#Ī liquid is being converted to two gases, so entropy will increase. So right from the start, you know that any reaction that has a gas as a reactant and a liquid as a product, for example, will result in a decrease in entropy. On the other hand, randomness and disorder decrease as a substance goes from gas to liquid, and finally to solid. Now, randomness and disorder increase as a substance goes from solid to liquid, and finally to gas. Similarly, entropy decreases as disorder and randomness decrease. The general idea here is that entropy increases as disorder and randomness increase.
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