Entropy: Why the 2nd Law of Thermodynamics is a fundamental law of physics

Why the fact that the entropy of the Universe always increases is a fundamental law of physics.

[@EugeneKhutoryansky]

To see subtitles in other languages: Click on the gear symbol under the video, then click on "subtitles." Then select the language (You may need to scroll up and down to see all the languages available). --To change subtitle appearance: Scroll to the top of the language selection window and click "options." In the options window you can, for example, choose a different font color and background color, and set the "background opacity" to 100% to help make the subtitles more readable. --To turn the subtitles "on" or "off" altogether: Click the "CC" button under the video. --If you believe that the translation in the subtitles can be improved, please send me an email.

[@count_of_darkness5541]

This video doesn't actually change aything in the initial argument. The fact that you would have to wait eternity-long time span still doesn't make improbable to be impossible.

[@count_of_darkness5541]

A more accurate picture seems to be that there is physical prototime and subjective time. The subjective time always points to the region where enthropy is increased and evetually comes to AN end. The prototime in which physical laws act doesn't care about the subjective time and just goes through such an and. From a past to a future to another past and another future crossing multiple universes and so on through all imaginable combinations.

[@naman4067]

Ok

[@naman4067]

@@count_of_darkness5541 lol 😆 so why newton's law is fundamental

[@cexploreful]

You just prove the oposite. Please, take your Nobel prize 🏆! If a law could be violated (even with small probability), then it is not fundamental at all. Your videos are MIND BLOWING!

[@Lucky10279]

You completely missed a huge point - the second law DOESN’T say that entropy can never decrease. It says that the entropy of a CLOSED SYSTEM will TEND TO INCREASE over time. The balls could all move to one side of the box and that wouldn’t violate it, because it would be a temporary, local reduction in entropy.

[@RickB500]

Thanks, that is an important point!

[@Jopie65]

Thanks for increasing the entropy in my brain! I hope it will stay there. Maybe I should stay at a warm place so my brain can't forget it by emitting this new knowledge as heat

[@ashutoshmahapatra537]

One of the best comment

[@EugeneKhutoryansky]

In case, you have not already seen them, I also uploaded several other videos recently. As always, for each video that you like, you can help more people find it in their KZbin search engine by clicking the like button, and writing a comment. Lots more videos are coming very soon. Thanks.

[@EugeneKhutoryansky]

***** The Poincaré recurrence time for a large system is so much longer than the age of the Universe that it can be said that this is essentially the same as saying that it will never occur.

[@EugeneKhutoryansky]

***** It depends on our definition of the word "never." Incidentally, I would point out that mathematically, an event can have exactly zero probability, while still being possible. For example, suppose we randomly pick any real number between zero and one. Since there are an infinite number of possibilities, each of them has a probability of exactly zero, yet they are each possible.

[@EugeneKhutoryansky]

Just for the record, I was not comparing the Universe to a discrete mechanical system. I was using the example of the two spheres just to explain the concept of entropy to people who are not familiar with it.

[@EugeneKhutoryansky]

For anyone who has not yet seen it, the link to my main video on thermodynamics can be found at the beginning and end of the video up above, and it can also be found on my KZbin home page.

[@JamesSmith-ek1or]

+Eugene Khutoryansky excellent argument and explanation

[@Trunks47r786]

Thank you for clearing up some misconceptions I had on the nature of entropy and the Second Law of Thermodynamics.

[@EugeneKhutoryansky]

Trung Nguyen Glad I was able to help.

[@EugeneKhutoryansky]

You can help translate this video by adding subtitles in other languages. To add a translation, click on the following link: kzbin.info_video?ref=share&v=vE82PDJB8ow You will then be able to add translations for all the subtitles. You will also be able to provide a translation for the title of the video. Please remember to hit the submit button for both the title and for the subtitles, as they are submitted separately. Details about adding translations is available at support.google.com/youtube/answer/6054623?hl=en Thanks.

[@corneliariasdita715]

The Valkyrie is a suitable song for arguing about thermodynamics

[@forrestgump3111]

lol 😂😂😂

[@ChildOfTheUniverse3]

This channel is "godsent" for a lay like myself. It simplifies difficult to intuit concepts into comprehensible packets of information from which many insights can be drawn

[@NomoSapienss]

Why these videos are not just good, but excellent, is because they just keep on giving. I found these videos interesting, when I was in gymnasium. Now I'm returning to them, while studying chemistry and physics at Uni.

[@EugeneKhutoryansky]

Thanks. I am glad you like my videos.

[@kingworld7430]

This is the channel I have ever needed and searched . Thanks to you to for these universal laws making available for us in such a beautiful way . Just love the way .

[@EugeneKhutoryansky]

Thanks. I am glad you like my videos.

[@simoputtonen2799]

This was a really cool video. You should do these kind of videos more often where you answer questions. It is more important to try to figure out ways break the fundemental laws of the universe than just remembering them. That is why I always try to ask questions about physics videos I watch.

[@EugeneKhutoryansky]

Simo Puttonen, I am glad that you liked this format. Though, there are still so many topics I would like to cover that it has to be a balance between making videos that answer questions that have been asked about my previous videos, and doing videos on new topics.

[@magnetmotor7160]

Eugene Khutoryansky if you do the same format with new stuff, then with answering questions you use adobe flash format it will save you time.

[@greysflorida7801]

Thank you for your work. Your videos helps me to improve my knowledges in physics and English simultaneously, it’s nice.

[@SvetlinTotev]

I really like your explanation for the second argument (the first one you disproved). Unfortunately, I didn't get at what point did you disprove the other argument. The argument is "the probability may be small but not 0" and you countered it with "well the probability is very very small". So that's just not an argument. Entropy doesn't necessarily have to always rise or always drop. It can go any way it wants with some probability. It is just that on average the universe will spend more time in more likely states and less time in less likely states but even that gets a bit more complicated when you concider that there is a big difference between the probability of the universe being in a state defined by some global parameters and the probability of the universe getting to a given state from another state. Technically, there is nothing stopping the universe from being in a loop, or even being in a state where the entropy stays mostly within a certain range and doesn't change its deviation too much in either time direction. It could even be that the universe is in a loop that is also symmetrical relative to two points in time. This doesn't disagree with the second law of thermodynamics because it is entirely based on statistics. And there is no such thing in statistics where "very small probability" = "impossible". As a side note, I would never believe that any event ever in the universe is based on complete randomness. This is for two main reasons. First of all, if the entropy is high, then events are very unpredictable unless you have the full information of the universe. Second of all, the fundamental principles that we use for doing science are based on determining the probabilities of things and trying to get theories with very high probabilities but we can never get a 100% probability on anything and we can't prove with any probability that some event is happening due to no pattern because that would be indistinguishable from not being able to find a pattern. So there is no way to prove that quantum mechanical events are purely random, we know that events can look random without being random and such a theory would give us no more information than supposing that we just don't know yet the pattern so it is completely useless. On top of that we already have measurements that increase the probability of a non-random theory over that of a random one like particle twins which would require an independant set of rules since their behavior is not purely random because of their co-dependance. Sorry for long post. I know nobody will be bothered to read it. I just wanted to say it somewhere so when in the future people find the pattern behind the "random" events I will be able to brag about not being so stuck inside the box of conventions.

[@RickB500]

Yes, think so too, but there is a good comment above, which helped me, of Mikayla Eckel Cifrese: "You completely missed a huge point - the second law DOESN’T say that entropy can never decrease. It says that the entropy of a CLOSED SYSTEM will TEND TO INCREASE over time. The balls could all move to one side of the box and that wouldn’t violate it, because it would be a temporary, local reduction in entropy."

[@raypath403]

Dude, physicists are just leading you by the nose. Entropy = probability(in their understanding). That's all. Entropy increase=probability is high,Entropy decrease=probability is low. This law just about systems with many particals. If we have 1,2, few particals-use Newton laws. Many particals=WTF count them. It is explanation why air around us cannot be used like fuel for 19th century. Intresting, will you read my explanation? :)

[@Captainspamo]

@@raypath403The way I understand it: entropy is closely related to probability, but not the same. It's all about the level of disorder in the system's microstates. As each moment ticks by, it seems like systems have this natural lean towards slipping into states that have a bunch of different microstates-more ways to shuffle around without changing the overall picture, which is what ramps up the entropy. The more microstates matching a macrostate, the more options the system has to move into as time rolls on, and that's why higher entropy sort of nudges the system into more likely states. So yeah, entropy is about the disorder, but it also gives us a hint about where things might head next, especially when you think about it over time. High entropy just means there's a whole lot of ways things could turn out, making it a pretty good guess that's where the system will go.

[@raypath403]

@@Captainspamo rolf, man. Or you trolling me or you just confused man! I broke my brain reading your post :) "High entropy just means there's a whole lot of ways things could turn out, making it a pretty good guess that's where the system will go." High entropy mean that: 14:40 High entropy mean single variant: all life will be dead. All your post misunderstanding or trolling!

[@raypath403]

@@Captainspamo Entropy is the set of most probable options. If you have 100 options and 2 of them are rare (all molecules are on the right and left side of the vessel) and 98 are different uniform distributions, this is high entropy. Life in the universe will end - just a huge set of different options (microstates) versus a much smaller number when life continues. Entropy is just a statistical law where options are counted and with a huge number of identical options it is said that Entropy is high. With an equal number of different options, it is low.

[@sanchitsingh7162]

During the first 2 minutes, I like how the narrator introduces the counterarguments before going like, "I'm going to destroy all of you who tried to blatantly apply your half knowledge of Physics."

[@EugeneKhutoryansky]

I didn't want to make people feel as they did something "bad" by trying to make these arguments. One of the ways science progresses is by challenging existing theories.

[@Jer20.9]

@@EugeneKhutoryansky I have heard that the 2nd law applies only to heat transfer in engines, and is not universal. This from evolution apologists who say it cannot be applied to the amount of entropy in say, an organism. Evolution involves a decrease in entropy as a simple organism evolves to a more complex one. Would you be able to comment?

[@EugeneKhutoryansky]

@@Jer20.9 The Second Law of Thermodynamics applies to everything, including to the evolution of life. The decrease in entropy of an organism is more than offset by an increase in entropy of the surroundings by the organism's dissipation of heat. I cover this in detail in my original video on thermodynamics at kzbin.info/www/bejne/fYDViKyVrrN1rLs

[@InvaderMik]

wardy For more information on this question, I would definitely recommend “What is Life?” by renowned physicist Erwin Schrödinger. The book covers many physics concepts in the view of how they apply to living systems. He covers entropy somewhere near the middle. It’s very accessible without dumbing things down, so I would definitely suggest it!

[@wesleyrm]

@@Jer20.9 Organisms are not a closed systems. We eat and excrete. Therefore the net increase the entropy of the universe is positive.

[@lucasf.v.n.4197]

I like your soft confident voice; besides your explanations and animations are the best; the 2nd law has always been difficult to grasp.

[@MichaelSmith-sn8mr]

Thank you for educating me. Seriously. You have vastly added to my knowledge base which is fundamentally increasing. Your demonstration was well-thought-out. I enjoy the purposeful simplicity of the most complicated topic to ever come to fruition. Until the 3rd Law of thermodynamics is introduced..... Lol To infinity and BEYOND.

[@kunalshukla1236]

Thanks for this beautiful explanation! Love watching your videos. Keep inspiring!

[@shkotayd9749]

I like these :D You simplify for non-experts very well :D

[@EugeneKhutoryansky]

Shkotay D Thanks for the compliment.

[@KerryFreemanMelbourne]

Great series of videos on an understandable level.

[@abadosa]

Incredible and excellent explained videos. I love your channel and your work, keep it going!

[@EugeneKhutoryansky]

***** Thanks for the compliment. Lots more videos are on their way.

[@abadosa]

Eugene Khutoryansky Fantastic! I'm waiting for them!

[@avanika_space]

Thank you for inspired me to study thermodynamics This is a great video

[@EugeneKhutoryansky]

Thanks. Glad you liked my video.

[@nikola4294]

Great video, yet its realy enjoyable to theorize about the probability, fun watching the video :)) keep the good work!

[@EugeneKhutoryansky]

+Nikola Thanks for the compliment. I am glad you liked the video.

[@TheGarrymoore]

Eugene, you can try to explain entropy using the argument of the sensitivity to initial conditions and Sinai billiards. It will be interesting to compare the two explanations, this given here and the second one.

[@brayanqlorbit]

Stadistic mechanics please, Eugene. Excellent work thanks

[@MrTiti]

staistic? sadistic? and what? why?! wtf ??

[@iaexo]

This is a wonderful video. You have opened my mind.

[@EugeneKhutoryansky]

Thanks. I am glad you liked my video.

[@Thekingmaker]

Question: At 5:00 it is stated that if we wait long enough the balls will eventually spread evenly between the two spheres, but after that happens wouldn't it be considered a decrease in entropy even if a single ball found it's way back to the original sphere?

[@jemie1190]

Great response video. My fav physics channel

[@EugeneKhutoryansky]

Thanks.

[@navinmishra9431]

Excellent. . Nicely expained d concept..waiting for more videos like dis..

[@EugeneKhutoryansky]

+NAVIN MISHRA, thanks. Glad you liked it.

[@littlefishbigmountain]

So this is basically the cosmic equivalent of waiting for the moving screensaver to hit _juuuust_ so that it strikes both sides of the monitor at once and bounces exactly off the corner and reflects back in the opposite direction

[@robertgreenwood2258]

this... this.

[@rmxevbio5889]

yes. there was a time when this idea came to my mind watching the bubbles screen saver... crazy!

[@Epoch11]

I agree that it is unlikely that the balls will gather in one spot and as human beings who live a blink of an eye this might hold true. The problem is that when we are talking about these kinds of probabilities, we are talking about unimaginable time spans. The Second Law fails to fully address this. It is a law that is ALMOST always true. It also fails to address the question of why the initial conditions of the universe were of such low entropy. I agree with most of what you said, but the fact that the probability is not 0% creates a situation in an eternal universe (eternal in time) where this will happen an infinite amount of times. You just have to wait a length of time that makes Graham's number look as if it barely is even there.

[@Epoch11]

Mark G So raise Graham's number to the power of a googolplexian number of years.........and then ask if this is going to happen. Obviously what will be coming together will most likely be pure energy as all atoms would have decayed, but this might occur and we do not know what the end result might be.

[@nanfolio]

+Mark G also, bear in mind that if it was just energy coming back together then that isn't the same micro state we started with. Also, there are no 'walls' at the edge of the universe for the 'balls' to bounce off back to where they started. It does not seem that the universe will even end in a big crunch. So while yes it is perfectly possible to beat the second law of thermodynamics on a small scale, it is a law of the universe.

[@phoenixamaranth]

I'm glad to see I'm not the only one who feels this way about entropy. I've been bothered by it from the first time I learned about it. It has always struck me as a generality that is useful as a tool but not necessarily true of the universe.

[@Adam-go7cz]

Exactly. Also, if universe is infinite, there are infinite worlds there these extremly unlikely events happend infinite times. And also there would be a world where these extremly unlikely evetns happens ALL the time. We are just too limited yet to understand. Like some primitive people could say that the sun rises every day for ever and without knowlage they would assume that it is a LAW. It is kinda same LAW as this (based only on our observatsion we have YET)

[@zes3813]

its imaginable

[@XtroTheArctic]

YAAAAAY!!! Return of the legend!! (Entropy)

[@zhouwu]

Awesome! I love it! Thank you so much!

[@EugeneKhutoryansky]

+Zhou Wu, glad you liked it.

[@The_Tormented_One]

It was very much helpful. Thanks 😀

[@tiagofranca2660]

Really great video!! Thank you!

[@EugeneKhutoryansky]

+Theenerd ジェームズ, Glad you liked it. Thanks.

[@joet7830]

Really good video as always!

[@EugeneKhutoryansky]

Joe T Thanks. Glad you liked it.

[@MrShanqwert]

Quite interesting...Tnx Eugene for putting vid after such a long time...

[@EugeneKhutoryansky]

MrShanqwert Glad you found it interesting.

[@astralacuity]

I'm simply curious: do you use a speech synthesis program for these or are they narrated by a voice actor? If the former, what do you use? Also, I'm curious what modeling/simulation programs you use for these. Thanks for making them!

[@EugeneKhutoryansky]

+James Hansen, all my videos are narrated by my friend, Kira Vincent. For my 3D animations, I use the program "Poser." Thanks.

[@astralacuity]

Your friend's narration is excellent! Keep up the excellent work on the physics videos!

[@victor7530]

Thanks. This is really interesting.

[@aminakhalid2197]

Amazing understanting❤👌

[@anom3778]

That was extremely profound!

[@Markus9705]

You bring up a very interesting point: the arrow of time. Our Universe does not seem to obey a T-symmetry which is still a unsolved problem in physics to this day.

[@ElPsyKongroo]

Have you ever thought to have quiz videos that use equations, calculus, derivations as well as concepts, all pertaining to the videos you make?

[@dramese]

Thank you best much for this great video

[@EugeneKhutoryansky]

Glad you liked my video. Thanks.

[@arkdark5554]

Absolutely fascinating...

[@blake301987]

Great video Eugene, thanks for making it!

[@EugeneKhutoryansky]

blake301987 Thanks. Glad you liked it.

[@evgenistarikov3386]

Dear Eugene + your esteemed audience, First of all, many sincere thanks for your collective efforts! Sure, bringing the universe down to Earth is definitely entertaining, but deforms the verity. As the arrow of time pushes us forward, each day the universe inches closer to maximum entropy. And when that does happen, the lights just might turn back on, and for all we know, we might just end up back at square one. This is but not for an average mind... Even scientific research workers' brains had to stumble... Hence, a clarification is urgently necessary! So, captain, AHOY! A. There is ONLY ONE BASIC, fundamental Energy Conservation and Transformation Law. It is definitely unique and conceptually indivisible delivering two logically joint concepts - these are Energy Conservation - and Energy Transformation. Still, a more-then-100-years-old conceptual failure has brought us to two separate thermodynamic laws - but this has nothing in common with the actual physics. To come back, they have coined two more fake thermodynamic laws, employed the Probability Theory + Mathematical Statistics, and this has helped formulate the Quantum Mechanics, which is thus a basically metaphysical conceptual construction and thus ought to be only restrictedly fruitful. B. By dividing the basically indivisible law, you are telling about Combinatorics, you are touching Probability Theory, you are even stepping back to Thermodynamics for a while, but... You are NOT answering the poser: WHAT IS ENTROPY, sorry! 1. In the formula S = kB * ln(Ω) you imply, Ω means not a "Huge Number of Microstates", not "Probability", which numerically ranges between [0,1], not even "Wavefunction", which ought to be a purely metaphysical notion, as it is... In effect, Ω ought to be a simplistic algebraic function of Lord Kelvin's Absolute Temperature. This result has been published 100 years ago in JACS. 2. WHAT-ENTROPY-IS-poser has been answered not by Clausius, not by Boltzmann, etc., but by Goethe, who has introduced Mephistopheles, the philosophical embodiment of ENTROPY. 3. Newton did basically know WHAT ENTROPY IS - A Counteraction. 4. That Counteractions do not grow to infinity with the growing Actions, but MUST reach their MAXIMUM values, is the result by Nicky Carnot formalized by Clausius... 5. In effect, Gibbs Energy formula renders implicit the interplay among ALL the relevant Actions (the Enthalpic term) and ALL the Counteractions (the Entropic term). 6. The standard approach you are reporting about is OK for the implicit Enthalpy-Entropy picture, employing it for studying reaction mechanism details is likewise eating soup with fork.🧐

[@anmolmehrotra923]

Thanks for clearing my misconceptions

[@EugeneKhutoryansky]

Glad my video was helpful. Thanks.

[@kipper1668]

I think it's worth noting that even in the extremely unlikely example scenario of the atoms going over to one side of the box, that is only the entropy of a small subsection of the universe decreasing momentarily, the rest of the universe more than compensated for that reduction in entropy during that moment. I'm not sure if it is also a statement of the Second Law of Thermodynamics that the entropy of all subsections of the universe always increase, but that might be a useful distinction to make. Although, this brings to mind the possibility that the entropy across the whole universe would decrease at the same time, which is maybe the single least likely thing to occur in any given moment? Interesting to consider...

[@andyashford6945]

Aren't you falling into a 'Maxwell's Demon' type trap by accepting apparently without question that 'all particles on the rhs' is necessarily a low entropy state? If the rhs space is at a sufficiently higher temperature than the evenly distributed state then the entropy of the low volume state may be the same or even higher, surely? Consider that any particle travelling left to right must first create space for for itself by slightly compressing the rhs with its own momentum. Then four things seem to follow: i) as the process progresses, it increasingly favours higher momentum particles with enough punch to break through the pressure barrier; ii) therefore a greater proportion of internal energy is being transferred to the rhs than mass; iii) therefore there is an ever increasing temperature jump at the boundary; and iv) eventually the lhs will run out of particles with sufficient momentum to perform this crossing. And leaving aside any consideration of the implausibility of preventing reverse flow, I see no reason to assume that any entropy is being lost during this process. Admittedly this may be an engineer's perspective rather than a physicist's, but I wonder if you see as I do some parallels between point iv) and the solution to the UV catastrophe? Good work nevertheless and sorry for not isentropically compressing this post to fewer lines.

[@Mrosen7542]

Thanks again for the great video. But wouldn't this have implications for the fate of the universe? If wait eons for life to go extinct and the universe to die, it would just remain barren for almost an eternity afterward, right? But if the universe continues to exist, albeit dead, for many, many more eons, then, theoretically, an extremely unlikely scenario such as described in the video would eventually have a strong chance of occurring. Then what would happen?

[@Toertsch]

Boltzmann Brains? And eventually another BigBang?

[@disgruntledwookie369]

More to the point, if the universe is eventually going to end up in that state and remain in that state forever, then that means it is significantly (in fact, infinitely) more likely for the current state of the universe to be a barren state than an active state. So why does the universe exist at all? Why are there stars? Why is there life?

[@user-cu7li6qq5x]

James White Entirely due to observer bias. Since we are part of the active state, we wouldn’t be here to observe it if it wasn’t this exact way. So no matter how unlikely it is, given that we exist to ask the question, it’s 100% guranteed from our point of view.

[@tissuepaper9962]

@@disgruntledwookie369 P[active state | humans exist] = 1. These are not independent events.

[@mikel4879]

Mrosen7 / The real Universe is infinite. Coming to an end, entropic or of any other kind, is not possible. An entropic end of the real Universe is not possible. Entropy is continuously increasing but it is not absolute. It is a complex and neverending emergent phenomenon.

[@jaxamilius5237]

Can you please tell me where you got the video of the small galaxies zooming by? it is so clear and HD. for example, from 9:58 to 10:41 . where did you get that?

[@EugeneKhutoryansky]

John Smith, I made that animation myself.

[@jaxamilius5237]

Eugene Khutoryansky Wow that is amazing. any chance you can upload that sequence? i know it is not releated to your channel but i would love to use it on my computer.

[@knv9090]

The video says that if we simulate -- backward in time -- the system of particles filling a box that came from a state where they all initially filled a corner, they will go back to being in the corner. But also, how do we simulate the wall that kept them in the corner in the beginning, and how do we simulate the removal/reinsertion of that barrier?

[@knv9090]

You say that we see expansion of the particles into a volume in forward time, but never contraction into a small space. But there are two things here (a) there was a barrier that prevented expansion until it was removed and (b) statistically, the expanded macro-state has more micro-states and all these micro-states look alike, so chances are high that the system ends up in an expanded state. If we repeat this barrier-removal multiple times, the micro-state of the expanded gas is different each time, but it always looks the same from a macro point of view. So, if we add statistics to the laws of motion, we get entropy increase without resorting to a new law. At least, that is what it seems to me.

[@brayanqlorbit]

Is there a channel like this where to learn physics this illustrative?

[@zyxwfish]

Got to love those aliens standing there at the start.

[@pasijutaulietuviuesas9174]

Watch the original reference video to learn how they got there.

[@oleg5730]

Thank you for your video. I have a question -- assuming that the universe has the highest entropy, would gravitational forces not eventually overcome the expansion of the universe, resulting in a new big bang?

[@donniedorko3336]

Gravity can only travel at the speed of light, and the universe is and has always been expanding faster than that.

[@Aladato]

Maximum entropy should be basically radiation if I'm not wrong. I'm guessing there's no mass and no gravity at that point.

[@shauryaverma9486]

Appreciate this explanation

[@EugeneKhutoryansky]

Thanks.

[@alexanderdiederichs7332]

fantastic video, thank you!

[@EugeneKhutoryansky]

Thanks. I am glad you liked my video.

[@Adam-go7cz]

So probabilty argument wasn't disproved. You just told us it is extremely unlikely and compared it to quantum mechanic extremely unlikely events. Don't forget that universe has unimaginable long time ahead so those extremely unlikely events can happen pretty easily.

[@Hank254]

+Adam Kubík The probability argument is wrong but it is explained better in a different video. Even with an infinite amount of time entropy does not decrease.

[@Adam-go7cz]

Thank you, could you please provide the link, or explain it little bit then? It seems to me, that if probability is more than 0% and you have infinite amount of time ahead, it must happen eventually.

[@Hank254]

Adam Kubík That's true, if something has a non-zero probability then it must happen eventually given an infinite amount of time. Entropy is a state variable like temperature or pressure. It emerges from the statistical behavior of the particles but (also like temperature and pressure) it goes beyond just the statistics. Imagine the air inside a scuba tank (at around 3000 psi). When you open the valve, the air will escape into the room with a considerable force. The air molecules come out and collide with slow moving air molecules in the room and distribute their energy randomly until the pressures equalize. Once the pressures equalize, the force pushing the air out of the tank disappears. This is considered the highest state of entropy for that particular system. If the air molecules (through their statistical random motions) start to randomly enter the tank, it will cause another pressure difference. That pressure again causes a force that prevents additional air from entering the tank (and the pressure will again equalize). So what happens is that the statistically emergent force of pressure actually disallows the system from leaving equilibrium; the air molecules can never randomly collide themselves back into the tank once their energy has been randomly distributed. People often use statistical examples when talking about the microstates (the individual arrangement of all particles). Often, they are very counterproductive; one example is a deck of cards. Shuffling a deck of cards has nothing to do with entropy, it is completely statistical. If you shuffle a deck of cards, it will (given an infinite amount of time) eventually return to its original order. ANY arrangement of 52 cards is exactly as likely/unlikely as any other arrangement; there is no force pulling the cards into a random order (in this case, the order is completely subjective based on our detection of 'interesting' patterns in the microstates). A change in entropy is NOT a change from one allowed microstate to another... it is an increase (or decrease) in the number of possible microstates. Because of bad examples like this or people equating Shannon entropy with thermodynamic entropy or the 'messy room' example, there are many people that think they understand entropy but they really don't; it is often taught wrong by both teachers and textbooks. I Hope that helps. I try not to post links on youtube because they tend to filter the posts as spam but if you search for 'entropy bad examples' you will find good explanations of what I am talking about.

[@Adam-go7cz]

Thanks for your effort. The Pressure example is however simmilar of what Eugene did in this video. How is it fundementally different, if you have an extreme example of 3000psi in large space, and 0,000...1 in the small space? (for example just 2 molecules of oxygen) I am not saying it is counter intuitive. It is of course it is... Also, I have an idea. Imagine all universe in perfect equilibrium. We don't know yet, what drives the expansion of the universe. Is it possible that in that state, weird thing things might start happen. (for example local gravity takeovers, collisions of particles and eventually new big bang? As analogy, when you look on sea waves, they are usually pretty same size and frequency. But from time to time, they add up (matematicaly) and you can see one HUGE wave. I don't really know the math behind all of this but still... Also you don't have to reply if you find it silly :D

[@Hank254]

Adam Kubík Not silly at all. The idea you talk about is very much like Roger Penrose' s theory about a cyclical universe. He postulates that the universe eventually reaches thermal equilibrium (even after any gravitational effects have exhausted their possibilities) at which point quantum uncertainty would dominate. This could be the 'nothing' from which a big bang originates. So instead of an expanding and collapsing cyclical universe, you would have an expanding universe until equilibrium... then another big bang and so on. I am not sure what you mean by your 'extreme example', can you elaborate? I can say that in Eugene's video, the balls are moving so slowly (and there are comparatively so few of them) that the temperature and pressure (and entropy) are not well defined at all. Essentially, the system is very close to absolute zero and any change in entropy would be negligible compared to the energy required to affect that change. Unfortunately, that aspect of the video does give the impression that entropy is strictly statistical.

[@Yotrek]

Low, or decreasing entropy videos would be interesting. ie how life decreases local entropy in a positive feedback loop.

[@lioneldelmas1814]

Hi Eugene, What about the 2nd law of thermodynamics and the big crunch theory? Doesn’t it contradict the fact that entropy can never decrease? How both can be reconciliated? Thank you. Your videos are great!

[@EugeneKhutoryansky]

Entropy would still increase as the Universe is contracting, as there is more that determines Entropy than just the amount of volume available. For example, all the matter/energy that was previously concentrated inside a star would now be spread out as photons dispersed over a large region of space.

[@b43xoit]

@@EugeneKhutoryansky So if there is to be a Big Crunch, each successive crunch and bang has ever higher entropy?

[@rittenbrake1613]

Why if each set of starting conditions was equally likely to occur , then the starting conditions which we would most likely get is one in which the entropy was already at the maximum possible value to begin with?

[@codegeek98]

10:27…you say it's something "profound": that we happen to live in a universe where "forward" time coincides with decreasing entropy. but I thought we defined "forward" *as* the direction in which entropy decreases (since causality necessarily Points that way, too)? i.e., it's true *by definition/convention* (of how we define time's "direction", what we call "forward") that we live in a universe where time flows "in" the direction of decreasing entropy, and not the other way?

[@riccardoorlando2262]

Well, there's then the matter of human memory. You could say that the second law actually says that we remember the universe in the direction of decreasing entropy.

[@yaramohamed33]

your videos are awesome.

[@EugeneKhutoryansky]

Thanks. Glad you like my videos.

[@rolandmousaa3110]

Thank you for the education on particles in the universe.. Roland (inventor)

[@EugeneKhutoryansky]

Thanks.

[@migfed]

Quite interesting vid Eugene.

[@EugeneKhutoryansky]

migfed Thanks. Glad you liked it.

[@robertruta687]

Great video, thanks for this. One thing I take trouble with, however, is your refutation of the first point. I don’t think you refuted it. It seems that you simply say: this happening is as unlikely as someone spontaneously teleporting across the galaxy. With this response you seem to be simply emphasising the unlikelihood of the event rather than demonstrating how this unlikelihood holds as a fundamental law. In the quantum case of teleportation no laws are violated. Your atoms and subatomic particles being measured on the other side of the galaxy is clearly not impossible according to quantum physics. In the thermodynamic case of spontaneous particle convergence the second law is violated. There is a non-zero chance of an event happening that violates a fundamental law. Both cases are terribly unlikely, however, in the latter case, the second law is violated because the entropy of the particle system has decreased. What do you think?

[@EugeneKhutoryansky]

My point is that the fundamental laws of the universe are inherently probabilistic. Therefore, the fact that something is probabilistic does not prevent it from being a fundamental physical law. Also, if the probability of something happening is so low that in order for it to happen, we would have to wait several orders of magnitude longer than the present age of the universe, this is almost the same thing as saying it never happens.

[@neildutoit5177]

@@EugeneKhutoryansky Hang on, there is a difference between saying that something has a low probability and saying that something will never happen because it has a low probability. isn't it that other laws of physics describe probabilities, but don't rely on probabilities? Quantum mechanics tells us what the probabilities are. But it tells us what they are with certainty. The wave function is an exact description of the probabilities isn't it? Whereas the second law isn't trying to describe the probability of entropy increasing, it's saying that it will happen, because the chance of it not happening is low. Surely there's a big difference between those two things? Surely if I appeared on the other side of the galaxy, that wouldn't actually violate quantum mechanics, but if entropy decreased, that would violate the second law? Or what do you mean by "probabilistic"?

[@neildutoit5177]

@@EugeneKhutoryansky With regard to the second point, doesn't one then need to draw a distinction between "fundamental laws" and "effective theories"? If something is so unlikely that it will never happen, but could, in theory, happen, doesn't that mean that the "law" is really just an effective theory? It describes what we experience with total accuracy. But surely it can't be fundamental if it could conceivably be violated?

[@EugeneKhutoryansky]

​@@neildutoit5177 You have some good points. I think that what is fundamental, as I focused on in the video, is the fact that our Universe started in a low entropy condition. This fact can't be derived from any of the other known laws of physics, hence it is a fundamental fact. We can view this fact as being synonymous to the Second Law of Thermodynamics, since either one of these implies the other.

[@neildutoit5177]

@@EugeneKhutoryansky thank you!

[@mynameisben123]

I don’t understand how entropy spontaneously decreasing being very low probability is enough to make it a law that it will never happen.

[@MichaelSmith-sn8mr]

Decay is the word I would throw around to express the unfolding nature of our experiences with a negative spin to it. And Stable for a more placid effect.

[@Prometheus7272]

Michael Smith I would disagree, the definition of decay is not inherently subjective, it is you who places a negative connotation on the word.

[@MichaelSmith-sn8mr]

@@Prometheus7272 Mister Prometheus I totally agree with you. But only the truly open-minded will understand that concept of yours. Regardless of its standing definition, my opinion again I repeat my opinion is that the word conjures up a macabre sensation due to its repeated and constant utilization in referencing death.

[@Prometheus7272]

@@MichaelSmith-sn8mr I agree, but to be perfectly honest with you i cant remember my train of thought from a week ago, im not sure exactly what i meant :D

[@MichaelSmith-sn8mr]

Neither do I bro LOL. Thought is so abstract that is hard to grasp and hold onto for so long. Are you a pothead like I as well LOL

[@Prometheus7272]

@@MichaelSmith-sn8mr I've re-read and i do understand what i meant now :D. I sometimes smoke weed, used to a lot more and probably will again when i go uni. Considering i don't smoke as much anymore i'm not sure i could be considered a pothead but i'm a pothead at heart lol. It should 100% percent be legal.

[@Imthatguyx10]

Great video. Loved it. But how do you explain a state of Absolute zero? Or superconductivity? Let's say where resistance is zero? A state of absolute zero would seem to imply that although it's highly unlikely for all heat to be ordered out of a system, it can be achieved such that any and all heat exists outside of the system in absolute zero. Looking forward to your response. Thanks.

[@EugeneKhutoryansky]

Thanks for the compliment. We can cool a system to near absolute zero using refrigeration. Using refrigeration to lower the temperature of a system does not violate the second law of thermodynamics, because the refrigeration system itself generates heat and expels it to the outside environment, such the increase in the entropy of the outside environment more than compensates for the decrease in entropy of the system being cooled. I go into this in detail in my original video on Thermodynamics at kzbin.info/www/bejne/fYDViKyVrrN1rLs

[@Imthatguyx10]

@@EugeneKhutoryansky ahhh yes of course! Duh! Thank you so much for your response! Have you heard of the ITER project? An international large scale fusion reactor that's projected to produce net energy for the 1st time ever? If that's true and it does produce net energy (say 500MW produced from 50MW input) and that net energy (450Mw) is used to run the refrigerator wouldn't that violate entropy? Thank you!

[@poondlasaidinesh9208]

Every one though 3ball in one ballon and 2 ballon in another ballon is maximum entropy bit it can be further extended to some extinct. By heating (converting enrgy boxess divide further . Thank you very much mam

[@RomanNumural9]

Although i personally don't doubt the validity of the second law of thermodynamics; i don't think the counter argument to the first argument properly addressed the point, unless i missed something. The argument being can't all the particles gathering in one region of the box violate the second law when they should spread out? Another example in the video i struggled with was the two spheres with 500 particles in the left sphere example that can be used to illustrate this confusion more clearly. Lets consider for a moment the initial condition set in that sphere example: All 500 particles in the left sphere. I don't argue that roughly 250 particles will be in each sphere after enough time has passed, but right at the start, as the first particle begins to leave the left sphere into the right sphere, couldn't that particle bounce perfectly off the back of the right sphere and land back into the left sphere, causing the entropy in the system to go from high to low and back to high again? Although unlikely, if this happens, that should mean the entropy in the universe has increased at some point and the law is violated. The explanation in the video seemed to explain that this is very unlikely but did not point out why the second law of thermodynamics forbids this from ever happening. That said though, these videos are very clear and well designed, i've been binge watching them over the past couple of days and it has been very enjoyable and informative. :)

[@phoenixamaranth]

I felt it didn't really address the criticism of probability either. I have never felt okay with entropy from the first time I encountered the concept. It seems more a tool to me than a law of physics. In general, and on our scale of things, it works wonderfully to calculate certain events, but that doesn't mean it's the rule of thumb for all things. In my mind, I immediately think of things like gravity, electromagnetism, even humanity and realize the universe, in fact, does have systems in place that can overcome the idea of an endless entropy.

[@Hank254]

"This is whats going on. When you have 500 particles in 1 sphere, it causes the temperature of the sphere to be higher than the sphere with no particles." Yes, this is correct. It is easier to visualize as pressure though. The only thing I would add is that temperature, pressure, entropy, etc. are state variables and only apply to the macrostate. The 'pressure' in the sphere with 500 particles is _extremely_ low... just look at the energy of the particles. It is essentially 0 (and the temperature is very close to absolute 0). When the pressure/temperature are so close to 0, the entropy is almost non-existent (it is an emergent property). When you are talking about higher energy systems (with real temperatures and pressures and entropies) these emergent properties will prevent the microstate from occurring again. There would not be enough energy for the particles to gather back into one side because it will be lower for the increased number of microstates. This is why entropy is often described as 'energy spreading'

[@RomanNumural9]

+Henry School I second that, nice!!

[@tmusic99]

I find the arguments against the second Law are somewhat outdated. But we may state "All models are wrong, some are useful" (George Box). In this context; Is the current model of the universe the final model? Will the entropy model need refinement?

[@tjjohn7983]

Superb animation with simple explanation of a complex concept. The loud background music however is distracting and should be removed .

[@donniedorko3336]

Am I following along?: The entropy is the measure of the number of microstates belonging to a given macrostate. We can also call this the uncertainty, and it is defined as the number of bits of information required to pin down the exact microstate. Am I at least close?

[@satchelfrost6531]

I just had a really interesting thought, but feel free to eviscerate me if my understanding is misguided or wrong. Okay so I'm not criticizing the second law because I know how useful it is and I'm all for it, but a sense of wonder came about me when I thought to myself "yeah it should technically be possible to close that door at the right moment so that the particles are in that confined portion of the box.... However unlikely". In other words, in this hypothetical reference frame I have gajillions of years to wait for that special moment. But then it dawned on me: if the 'particles' are atoms then you would never be able to observe both the position and momentum of any single particle at any given moment (i.e. The uncertainty principle). So even if you had a gajillion google plexium shmexium of time, you would never be able to observe the moment when it would be necessary to close the door. What say you physics gurus? Does my argument strengthen the 2nd law, or is it beside the point?

[@davidwright8432]

I think your argument runs into the same difficulty as 'Maxwell's demon' - a little guy who does exactly what you suggest, tracking each ball and letting balls travel only into the smaller volume. Every time an ball approaches his barrier, he opens it, the ball goes in, and - he closes the barrier! Surely, given long enough, he'll get all the balls in? Unfortunately, it takes energy to make the observations - and swing the door! And before he gets the last ball, he'll no longer have enough energy to observe, or trap, it. The best thing you could do is google 'maxwell's demon', likewise on youTube, and check out the explanations. They'll say what I wanted to - but may say it clearer!

[@dariuszspiewak5624]

@@davidwright8432 But the problem is that it's not about any trapping particles at all. It's about such an event occurring or not. And the answer is precisely this: Given enough TIME, any combination in the box WILL eventually happen (since it's probability is not 0). It's not about opening and closing any doors, even theoretically. The entropy of any sufficiently complex system will be increasing over time precisely because there is not enough time to wait for the opposite to happen. However, it's not hard to demonstrate that in very simple systems, entropy will be fluctuating. It's the same story as with the phenomenon of electron tunelling. If there are 2 electrons, it's easy to observe that an electron can get out of the potential well without having enough energy. In other words, a single electron can disappear on one side and appear on the other (like a ghost). But if you have a system with billions of electrons.... what is the probability that all of them at the same time will do what one can do easily? THIS WILL NOT HAPPEN because there is not enough time (and will probably never be) to observe this. If we assume that each electron acts independently and the probability that within time T it'll overcome the energy barrier is p, then for billions of electrons N the probability that all of them do it within time T is p^N. This for big N will be unimaginably small. And even if p were close to 1, given big enough N, the probability of all of them doing the thing within time T would be virtually zero (for all intents and purposes). This is by the way one of the reasons why we can't see things going through walls... and emerging on the other side.

[@cxa011500]

I'm probably going to need to re-watch this a few times. :/

[@chrissalinas325]

Grad physics student here to drop my opinion! I was having this exact talk with some of my peers the other day, and it seems like what we were arguing was the definition of a "fundamental" law. Since it is clear that the 2nd law of thermodynamics can be broken down into the convolution of other laws (for example simulating the particles in a box only using newtonian mechanics), then it itself shouldnt be considered a "fundamental" law. Not saying its wrong in anyway, or that any derived statistical mechanics from it are wrong (obviously there is a grand advantage gained from studying things in a statistical way), I'm just saying it shouldn't be considered a "fundamental" law. The video presents an interesting counter point to this view. While other laws are symmetrical with time, it presents the argument that, given the sheer unlikelyness of the existence of a universe that when ran backwards in time entropy decreases, since we live in this universe now (where that appears to be the case) the initial argument is violated. And I see how one can think of it that way, but I would counter that point using another meta-physical argument. The anthropic principle. Which states that only a universe capable of producing observers, will be observed. We cannot say anything about the probabilities of any other universe producing life based on our sample size of (1) universe. But what we can say is that we know for certain this universe with its laws and conditions etc. can produce life (obviously). Which means that, even in an extremely unlikely universe where the probability of entropy decreasing backwards in time is just as unlikely as it decreasing forwards in time, it is not valid to assume the argument presented to be falsified by sheer unlikelyness, given the anthropic principle and all it entails.

[@egidijuskuprusevicius4225]

2nd law of TD says that all processes are going toward energy minimum (which is a direct result of 1st law of TD)...other formulations are nonsensical especially with order-disorder thing

[@larrykinglk]

Very good all together, but the Music!!! Why? And why so loud?

[@adiadiadi333]

last question, at 5:21 what is that song? i couldnt find it with nekoprism. i wont ask any more question on where you find the songs.

[@EugeneKhutoryansky]

All the music in this video is from the free KZbin audio library, and the names of the songs are the following. Ride_of_the_Valkyries_by_Wagner Renaissance_Castle Allemande

[@padamrajgurung9916]

Thank you very much!!

[@EugeneKhutoryansky]

+Padam Raj Gurung, you are welcome, and thanks.

[@luphiax4239]

Very good explanation. Sorry if i ask but did you mean at min 9:50 "increase as you run the simulation backwards in time?" Because if, due to the 2nd law of thermodinamycs, it is unlikely that forward in time entropy dicreases so it means that it should increase.Then if something is increasing forwardly it means that it should decrease backwards. Probably you were refering to the simmetrycal property of law of physics that you mentioned before, so in this sense you were actually demonstrating that you should need another theory to explain our universe. Correct me if i'm wrong, anyway thank you again for your videos they are helping me a lot understanding physics more deeply.

[@EugeneKhutoryansky]

I meant exactly what I said. If you pick a "random" set of initial conditions, and then run a simulation (either forward in time or backward in time), then it is unlikely that the entropy would decrease. The laws of physics work the same way both forwards and backwards in time. Therefore, there is something special going on in the universe with regards to the types of initial conditions we are actually presented with. (These initial conditions are not random.) Thanks.

[@luphiax4239]

@@EugeneKhutoryansky Perfect, now i underatand. Every answer you give is so precise and long that you are actually representing an online incarnation of a real professor. You are really humble to answer in these way to all the comments they write, even the stupidest like mine. I really wish you the best

[@brayanqlorbit]

there is some channel like this where learn physics this illustrative?

[@chikeezebilo6545]

Could entropy account for the universe expanding but slowing down as it expands?

[@PumatSol]

What are your thoughts that the initial conditions of our universe are what they are due to the fact that our universe used to be in a state of maximum entropy, and existed in this state for so long that due to random motion, all energy in the universe spontaneously condensed into such a small volume that the Big Bang happened? Given an infinite amount of time, if spontaneous decreases in entropy continue to be theoretically possible, then the probability of such an event occurring eventually is exactly 100%.

[@patgoley]

Firstly, thanks for the amazing videos! I'm still a little confused on the refutation of the 2nd critique. You seem to say that entropy could decrease but it's so unlikely that we'd have to wait longer than many times the age of the universe. But that seems to imply that it is still probabilistic and not fundamental. Besides, what's a few trillion years between friends?

[@EugeneKhutoryansky]

One way to look at it is that fundamental laws of the Universe, such as Quantum Mechanics, are intrinsically probabilistic. Therefore, something being probabilistic does not negate the fact that it is a fundamental law.

[@ngruhn]

I’m still a bit skeptic. If it would “only” take until the end of the universe for decreasing entropy to occur, would it still be a fundamental law? Or if entropy decrease would be as likely as me winning the lottery, would it then still be a fundamental law? Or if it would be as likely as getting a 6 when rolling a die? I guess not right? But were do we draw the line? Picking any specific probability feels arbitrary, so that’s why the second law doesn’t feel truly like a fundamental law to me.

[@rodrigoappendino]

Eugene, can you make a vídeo explaining wave functions and the newest atomic model?

[@EugeneKhutoryansky]

Rodrigo Appendino, I discuss wave functions in my video on Quantum Mechanics, and I cover the atomic electron orbitals at the end of my video titled "Waves: Light, Sound, and the nature of Reality." Though yes, would like to eventually make another video that goes over the atomic model in much more detail. Thanks.

[@rodrigoappendino]

Eugene Khutoryansky I can't understand why wave functions of quantum mechanics has complex numbers. That's why I asked.

[@jeevahbkhhh]

one small doubt to me that....entropy is really how many configuration it can take in space...please reply me if possible

[@animeshkumar1201]

Sir can you please upload some videos explaining thermodynamic processes like polytropic and adiabatic expansion cooling.thanks,you are doing a great work,,,😂😀👌👍

[@EugeneKhutoryansky]

That is covered in my main video on Thermodynamics at kzbin.info/www/bejne/fYDViKyVrrN1rLs

[@MadiDoll]

Sort of a related question. If you could identify all of the starting conditions of the universe and the related physics, could you theoretically use this information to predict all past and future events of the universe? I have been struggling with the concept of free will lately, and while I know this is more of a philosophical domain, my personal belief is that life is not inherently special in relation to any other form of matter in the universe and thus what we experience as free will/the linear way in which we interpret time is merely an elaborate illusion. Perhaps this is my own flawed perception, or is it perhaps that our entire perception of time, free will, and the value of life at a universal scale is what is really flawed? Thoughts? (This is not meant to be a question of ethics/morality. I value life, of course.)

[@bradbadley1]

+Madi >>could you theoretically use this information to predict all past and future events of the universe?

[@speculawyer]

IMHO, No. you can't get all that starting point information. and even if it was given to you, quantum mechanics throws in impossible to calculate randomness.

[@ACLozMusik]

+Madi As it has been said, you need a deterministic universe for that as so far it doesn't seem to be the case for our own

[@pabs7135]

If the attained entropy of a system is at its maximal value, is it possible that a different state is achieved?

[@angelmunoz1925]

You resolv my question thank you

[@junk_bear]

Parallel universe and multiple different dimensions with different possibilities. Like for example theirs a universe we’re instead me eating the strawberry ice cream I am eating vanilla ice cream instead. Can entropy used like that ?

[@BKNIRJULI]

What is meant be 'equally likely'? What have you tried to tell by this 2 word?

[@fugacityxdunk6782]

do you have a major in physics? or a PhD? you are so professional :)

[@tsgptmautomobiles4583]

Excellent

[@EugeneKhutoryansky]

Thanks.

[@cr1216]

For the second question, is it the same way of the probability of generating a random real number between 0 and 1 of being exactly 0.5? If that's the case then there is still a slim chance of hope that humanity will survive if we managed to figure out that "exact 0.5".

[@davidbain701]

Entropy must be an elastic energy imparted to each molecule That is a way store the potential for all its possible modes We just have to change the conditions to obtain the different modes

[@gabrielmirandalima3493]

13:07 but if the universe is infinite in size, then it means that the probability of such scenario really occurs is 100%, because there will be an inifite amout of boxes and all the possibilities will happen, so it means that there may be an infinite amount of living beings that saw, that are seeing and that will see a box with all the particles going to the same side of the box

[@dariuszspiewak5624]

It's not about the size of the Universe. It has nothing to do with this. It's about the TIME. If there is enough TIME, such events should happen.

[@Nikhil-vy2lt]

Please explain line integrals.