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Entropy: A little understood concept in physics [video]
- 4ad 3y agoI hate Veritasium's clickbait, and I think most of his videos are very poor, but this one is the exception. It's very well put together. The first ten minutes of the video is exactly how I introduce entropy to people. Of course I can't give him a pass on how crass it was telling that women he has a PhD in physics (he does not). The video would have been so much better without that two seconds of footage...
- andyjohnson0 3y ago> course I can't give him a pass on how crass it was telling that women he has a PhD in physics (he does not) To be clear, he does have a PhD but it is in physics education research, not physics.
- deleted 3y ago[deleted]
- hilbert42 3y ago"I think most of his videos are very poor," Why do you think so? (Most to me seem reasonable but one on speed of electricity stands out as badly done (he redid the video but it too could have been better).)
- willis936 3y agoHis video on electromagnetism is still my gold standard for Lorentz's Law. It came out while I was taking emag. I liked it so much I showed it to my professor, who didn't name drop Lorentz all semester. The class was making sure no one got a BSEE without knowing Maxwell's Equations, which does warrant a semester. I guess it was more of a failing of the physics curriculum.
- hospitalJail 3y agoHis dandruff ad was pretty cringe IMO. But idk, it seems like his videos are really long for what they accomplish in general. He seems like the generic youtuber that milks every dollar of ad revenue and is shameless about it. Kind of sad that a expensive camera + clickbait thumbnail/title > Experts communicating clearly and accurately. I imagine he/his team is scouring youtube for the experts, and remaking their videos with more production value.
- pxeger1 3y agoHe seems to exaggerate the importance of things when they make for a good story and sound interesting. This is a classic flaw in popular science but I think he's got a lot more egregious with it over the years. The worst example I remember, which is actually what drove me to unsubscribe, was when he said that the golden ratio was "a pretty five-y number" because it can be written as 0.5 + 0.5 * (5^0.5). Anyone with a good mathematical background could tell you there's nothing five-y about 0.5 at all. I'll grant him, the golden ratio is still a little bit five-y because of the sqrt(5). The whole context and presentation seemed like it was designed to make the viewer feel like they'd learnt something even though nothing of substance was really delivered in those 20 seconds. He does that a lot.
- interestica 3y ago> Anyone with a good mathematical background could tell you there's nothing five-y about 0.5 at all. Um, I disagree? Visually, the 5 is memorable here. "Fivey" just seems to mean "lots of the number 5"?
- koningrobot 3y agoI think the point is that 0.5 is 1/2, and the 5 digit only appears because of our base 10 presentation of numbers.
- pxeger1 3y agoI think the context was perhaps more important than I'd considered to explain the significance of "five-y". The implication was that the fiviness gives something of an intuitive explaination for why some shape had 5 sides. The presence of a √5 does (maybe) do this, but 0.5 definitely doesn't. (Because as sibling comment points out, 0.5 = 1/2 and the 5 only appears due to our (arbitrary, from a mathematical point of view) choice of base ten.
- hilbert42 3y ago"The whole context and presentation seemed like it was designed to make the viewer feel like they'd learnt something even though nothing of substance was really delivered in those 20 seconds. He does that a lot." I can't disagree with that. He's not only a YouTube presenter but also a documentary maker, His documentary Uranium: Twisting the Dragon's Tail https://www.imdb.com/title/tt4847012/ https://www.imdb.com/title/tt4847012/ has been repeated on TV where I am, I think, at least three times. He's also made others. Unfortunately, that type of presentation is all too common in modern docos (probably couldn't get it past the director otherwise). As you'd know, this and similar techniques (which I find highly irritating) are also used to pad out half-hour shows to an hour and or to multi episodes when one would do adequately (thankfully, my PVR comes to the rescue and I rarely watch them in real time).
- AlexandrB 3y agoI was quite disappointed by his video on self-driving cars. It presented a very one-sided view and felt like a puff piece (and, indeed, it was sponsored by Waymo). Tom Nicholas did a good job breaking down the problems with it: https://m.youtube.com/watch?v=CM0aohBfUTc&pp=ygUPdG9tIHZlcml0YXNzaXVt https://m.youtube.com/watch?v=CM0aohBfUTc&pp=ygUPdG9tIHZlcml...
- manojlds 3y agoMost of his videos are GOOD, come on!
- kergonath 3y agoThe problem is that on a given specific subject you can never be sure whether he’s exaggerating or misrepresenting things. Just this makes watching him a waste of time, because then you need to spend at least twice the time to fact check him. A bit like asking a question to ChatGPT. At least Wikipedia provides you links to proper sources.
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- PrimeMcFly 3y ago> I think most of his videos are very poor, This sounds quite bitter, as does griping about him mentioning his PhD. His videos have excellent production quality, and do a great job of communicating advanced STEM concepts to laypeople in an entertaining way. Maybe you don't like them, but that doesn't mean they are bad. Given their popularity, it would seem they are anything but.
- thumbuddy 3y agoIn my opinion the most misunderstood concept from physics is probably any exponential relationship. I realize we could view entropy to be one of those if we flip the relationship around and equate for microstates making my statement the superset. But generally speaking, Ive seen both lay people and experts struggle to reason about them, especially with complex numbers.
- szundi 3y agoJust after Sabine’s
- lll-o-lll 3y agoYes, and the Sabine video contained far more information (lower entropy?) and one genuinely interesting idea I’d never heard before. The idea that heat death may not be the end of intelligent life! The concept this relies on is the idea that macro states are actually just combinations of micro states all of which have the same probability. E.g. the sequence 1, 2, 3, 4, 5 and 3, 1, 4, 2, 5 are equally likely if you are selecting 5 random numbers (1-5), but the ordered sequence is an important state to us. The Big Bang -> heat death is just super unlikely state to super likely state, but these macro states are poorly defined. They matter to us. So perhaps the universe goes on with complex life harvesting neg-entropy from a heat death configuration of micro states as they slowly transition from “extremely unlikely” to “likely” in the context of something incomprehensible to humans. I feel like the idea would need more mathematical meat on the bones to go further, but still an intriguing thought!
- cubefox 3y agoI suspect that "macro state that is more important to us" really is special in some objective way, not just subjectively.
- hilbert42 3y agoThat's an excellent overall summary as he covers almost every aspect of the subject albeit in brief. It would be good if he produced a second video dealing with the low entropy of incoming energy from the sun and the higher entropy of radiated energy from earth and relate that to global warming. In all the debate over global warming little is talked about why say CO2 and other greenhouse gasses increase the earth's temperature and how they shift the wavelength of the radiated energy from earth. In other words we need to explain in simple terms why the incoming and outgoing energy can remain the same yet the earth's temperature has increased.
- willis936 3y agoWhich debate over global warming are you referring to? There are debates that involve atmospheric chemists that discuss Earth darkening cause and effects. https://en.m.wikipedia.org/wiki/Albedo https://en.m.wikipedia.org/wiki/Albedo
- hilbert42 3y agoRight, the average person hasn't a clue about albedo, nor do they know why say CO2 and CH4 increase global warming whereas others such as O2 are more benign. It may help lower the temperature of the debate if they did. Edit, we're pitching this discussion at the level he has—the lay public. Scientific argument over the minutiae is another matter altogether.
- jjaken 3y agoYeah debates in climate science are about phenomena laypeople don’t even know exist. It’s about how what we observe happens. No one is arguing about what we’re observing, eg global warming.
- jjaken 3y agoThe important part to understand is timescales. In a day, the Earth does absorb some energy. Of course it does, plants collect it, solar panels collect, the ocean and land collect it. The amount Earth collects is a tiny fraction of what it releases. That collection isn’t permanent though and is slowly released. Within a day, the Earth absorbs some energy, but over a long enough timescale, all of that energy is released again. The Earth is taking on energy every day from the sun. If we didn’t release it all back, the earth would be warming much much faster. It only remains relatively cool because it releases almost as much as it receives. Another important note is that long term energy is not only stored as heat on earth. It’s stored as potential energy in the atoms of cells in plants and animals. Think of how cold a gallon of gasoline is, yet how much energy it stores. For an example think of hot asphalt from a summer day. It gets real hot all day and slowly cools down at night. Sometimes it can be pretty warm to stand on the road even if it’s a cool night. Within the human timescale, the Earth is retaining some (tiny fraction) of heat. That tiny fraction of heat is a very small window of heat that life can tolerate. It’s not too much and not too little. If the earth were to retain just a tiny bit more, suddenly life can’t tolerate it. On the scale of the universe, the difference between those realities is minuscule, even though it’s enormous to us.
- lisper 3y agoA pithier way to introduce this topic: the first law of thermodynamics, a.k.a. the law of conservation of energy, is that energy cannot be created nor destroyed, only transformed from one form to another. In light of this, how can there ever be a shortage of energy? [Note that this is intended to be a rhetorical question advanced for the purposes of pedagogy. If you find yourself wanting to post an answer, you have missed the point.]
- sghiassy 3y agoUsable energy is different than total energy. If energy isn’t concentrated (say something like gasoline) it’s not usable
- dekken_ 3y ago> how can there ever be a shortage of energy I think it's not so much a shortage of energy, but that there thermodynamic equilibrium and thus no available energy to do anything. I don't think this will ever happen tho, it's pretty clear to me that making energy more dense is a universal process.
- sghiassy 3y agoNot really - look up “heat death” of the universe.
- jjaken 3y agoHeat death doesn’t mean “no heat” or that energy has depleted. It just means that energy is fully dispersed. All kg the hear exists, it’s just that no one place has any more than anywhere else, and so there is no longer any transfer of energy.
- A_D_E_P_T 3y ago> so there is no longer any transfer of energy. Ah, but there is. The Second Law is a statistical law, not an absolute law. On long enough timescales, low-probability fluctuations in local entropy will allow for energy transfer. These fluctuations will also allow for the formation of structures. (Boltzmann himself was of the opinion that the low-entropy universe emerged from a higher-entropy background state. And indeed there's nothing in physics to rule out the emergence of Boltzmann Brains and even Boltzmann Galaxies from homogeneous and maximally entropic universes in "heat death." This is a philosophical problem of the highest order, because it implies that we're not necessarily going from "less likely to more likely states" as the video implies, but rather from a relatively deterministic state to a probabilistic state.)
- manojlds 3y agoWhen I was watching the video I was thinking this deserves to be posted on HN and yup, someone already has.
- hospitalJail 3y agoLast night me and my wife were deciding if we should watch The Witcher or this video. I decided I didn't have the brainpower/mental capacity to think about The Witcher and that this video on Entropy would be easier to digest.
- SanderNL 3y agoNot sure if you are humble bragging, but I agree The Witcher is more demanding. Layers of meaning, emotions, allegory, subtext. It’s no Shakespeare, but physics and math are simple in comparison especially in the wonderfully produced and easily digestible format of Veritasium.
- Balgair 3y agoI mean, the author has a doctoral degree in science communication. It's his job and the point of the channel to try to make things easy to understand. The opposite is true with fiction. You're intentionally trying to have the audience make connections themselves, like a Sherlock story or the Great Gatsby. The point is in the discovery by the viewer.
- TexanFeller 3y agoI recently enjoyed this presentation by Sean Carroll that touches on definitional and philosophical issues with entropy. The talk made me feel less stupid for not feeling entirely comfortable with how entropy was explained to me before. Turns out there are a few different ways to define and quantify entropy that are used in different contexts and they each have some unresolved philosophical issues. "Can you get time out of Quantum Mechanics?": https://youtu.be/nqQrGk7Vzd4 https://youtu.be/nqQrGk7Vzd4
- m3affan 3y agoI wonder how many concepts that are so complicated for our brain to formalize or even process.
- cubefox 3y agoAnother surprising thing is that physicists have not yet succeeded in reducing the ordinary notion of cause and effect to fundamental physics. Carroll has also worked on this issue.
- kergonath 3y agoI would recommend reading some Carlo Rovelli, it sounds like something you might like.
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- guerrilla 3y agoIt's actually amazing how bad science popularizers are at explaining entropy. It's really not that difficult if they would just take some time and think before they speak (which I'm sure this video proves based on what people are saying about it.)
- spuz 3y agoI think the concept would be easier for me to understand if we talked about the inverse of entropy - i.e. some kind of measurement for the concentration of useful energy or "order". I think it would then be more intuitive to say that this measurement always decreases. Do we even have a word for the opposite of entropy?
- knolan 3y agoExergy
- dangitnotagain 3y agoPotential
- MaxRegret 3y agoNegentropy? This is a concept in information theory, but maybe also in physics.
- winwang 3y agoAnd it's closely related to the Gibbs free energy (available energy), which decreases with increasing entropy, all other things equal.
- vehicles2b 3y agoI find it intuitive to think of such “ordered” distributions as having a higher compression ratio. (Ie compare the file sizes of zipping a file with just ones or just zeros vs zipping a file with a uniform, random mixture of ones and zeros.)
- Solvency 3y agoHuh? I've never really understood this metaphor. Take any photograph in Photoshop. First, save one copy of it as a compressed JPG. Now, on the original, add a small densely repeating tiled pattern multiplied on top as a layer. Like a halftone effect, dot texture, whatever. Technically you're adding more order and less chaos. The resulting image won't compress as efficiently.
- dangitnotagain 3y agoEntropy should be redefined as “the distribution of potential over negative potential.” Whether discussing what is over what may be, or thermal equilibrium, potential distribution describes it all!
- lvl102 3y agoI’d like to think of entropy in terms of randomness or rather uniqueness of elements/compounds within a system.
- javajosh 3y agoEntropy only made sense when I learned it from the perspective of statistical thermodynamics. It's a very programmerly understanding, IMHO, and it's quite intuitive. EXCEPT that the language used is ridiculous: grand canonical ensemble indeed! Anyway, the idea that a system can be in some number of specific states, and that equilibrium is that unique situation where the number of possible specific states is at its maximum, really spoke to me.
- passion__desire 3y agoEntropy is mathematical force to be honest.
- Solvency 3y agoHuh? "Force"?
- esafak 3y agoconcept
- danq__ 3y agoNo. A force is the correct characterization. Entropy is indeed a force with a singular direction. Can you explain why does entropy perpetually increase? Additionally explain what happens if we reverse time, does your intuition of entropy still make sense? Likely no, because there is a vector directionality to entropy which makes it comparable to a "force".
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- dekhn 3y agoI took a stat thermo class and it was basically all about entropy, which was expresed as ln W- the log of the number of ways (permutations) that a system can be ordered, which gives a convenient denominator when calculating the probability of a specific permutation. Here's the professor's book, which was still only in latex form when we took the class: https://www.amazon.com/Molecular-Driving-Forces-Statistical-Thermodynamics/dp/0815344309 https://www.amazon.com/Molecular-Driving-Forces-Statistical-...
- dist-epoch 3y agoSabine Hossenfelder also had a video recently on entropy: > I don't believe the 2nd law of thermodynamics. https://www.youtube.com/watch?v=89Mq6gmPo0s https://www.youtube.com/watch?v=89Mq6gmPo0s
- evouga 3y agoWhat I really like about this explanation is that it highlights the fact that entropy is not a natural property of the physics system: entropy is only defined with respect to some coarse-graining operation applied by an imperfect observer of the system. So as Sabine points out it seems we should really be talking about multiple different entropies, each of which corresponds to a different mechanism for coarse-graining microstates into macrostates, with each different entropy changing at different rates depending on the coarse-graining mechanism and physical system. (And in particular, God observing the universe would not see entropy change at all; even if there were uncertainty in the initial conditions of the universe, God would see that uncertainty perfectly propagated with no loss of information, in a way made precise by Liouville's Theorem.) But even this is not the full story, because I can take a mass-spring network, and no matter how I choose to coarse-grain it, I will not see the entropy corresponding to that coarse-graining increase, because the trajectory of a mass-spring system is periodic. Entropy increase requires that the system is ergodic with respect to the chosen coarse-graining operation, i.e. that over long times the trajectory visits the coarse-grained states in a "random" and uniform way. It's not at all obvious to me why the dynamics of particles bouncing around in a box have this property, and particles attached in a mass-spring network do not; and neither the Sabine nor the Veritaserum videos address this or why we should expect all practical real-world physical systems to be ergotic with respect to practical coarse-graining mechanisms.
- dist-epoch 3y ago> mass-spring system is periodic I don't pretend to understand this stuff, but wouldn't a real mass-spring system slowly stop, due to friction, air resistance, heat dissipation, ...? So a real system wouldn't be periodic.
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- bugs_bunny 3y agoAn interesting read related to this is the following article, which begins with von Neumann's comment that ``Nobody really knows what entropy really is." https://www.researchgate.net/publication/228935581_How_physicists_disagree_on_the_meaning_of_entropy https://www.researchgate.net/publication/228935581_How_physi...
- floatrock 3y agoThe part that was new to me was the bit about how a space full of life tends toward more entropy faster than the same amount of space without life. Like the best ideas, it’s simple and makes sense if you think about it, but it’s still a really interesting framing that the complex machinery of life is really just the most efficient “entropy converter”. If there’s something about the arrow of time that speeds towards the heat death of the universe, we’re just helping it go a tiny bit faster here on our floating speck of dust.
- quickthrower2 3y agoDoes Einstein’s model of time care about entropy. In other words if there are 2 regions, one where entropy is increasing at that time and one where it isn’t as much, does it affect time?
- semi-extrinsic 3y agoNo. Entropy can be used to explain the direction of time, as a kind of symmetry breaking of all the microscopic laws that are symmetric in time. But it does not say anything about the "speed of time". Relativity does tell us the speed of time - it's the speed of light.
- Balgair 3y agoTo be suuuuuuper pedantic here: Relativity tells us that time is a dimension, one that is a bit unique. In that it has a constant attached to it. So, the 3 dimensions you're used to are just normal, they have no constants. (x,y,z) Meters of x are meters of z and meters of y. Relativity (and I'm really simplifying a lot by just saying 'relativity'), well relativity comes along as says that time is also a dimension, just with the constant of 'c' attached (the speed of light). That way you can convert seconds into meters. (x,y,z,ct) not just (x,y,z,t). So now the time dimension is much larger than the spatial dimensions. About 300,000,000 times larger, a third-ish of a billion. So a meter of x is ~1/3 of a billion meters of time. Now, there is a lot more about relativity, like, just tons. And I skipped most of it. And trying to just say that time is a simple little conversion away from meters is just wrong. And how that all relates to entropy is a mess that we really haven't figured out yet.
- rssoconnor 3y agoWhile this is a reasonable historical explanation of entropy, and explains that we don't gain net energy from the sun, it still misses the mark on what entropy is now known to be. Entropy isn't a property of an object, or a system or things in physics. Entropy is a property of our _description_ of systems. More precisely it is a measure of how poorly a given specification of a physical system is, i.e. given description of a systems, typically the pressure / volume / temperature of a gas or whatnot, how many different physical systems correspond to such a description. In particular, _thermodynamic entropy is Shannon entropy_. In the case where the description of state specifies a volume of phase space wherein a physical state lies within, then the entropy is the logarithm of the volume of this fragment of phase space. If we take this collection of states and see how they evolve in time, then Liouville’s theorem says the volume of phase space will remain constant. If we want to build a reliable machine, i.e. an engine, that can operate in any initial state that is bounded by our description, and ends up win a final state bounded by some other description, well, in order for this machine to preform reliably, the volume of the final description needs to be greater than the volume of the description of the initial state. Otherwise, some possible initial states will fail to end up in the desired final state. This is the essence of the second law of thermodynamics. I want to emphasis this: entropy exists in our heads, not in the world. E.T. Jaynes illustrated this "5. The Gas Mixing Scenario Revisited" in https://www.damtp.cam.ac.uk/user/tong/statphys/jaynes.pdf https://www.damtp.cam.ac.uk/user/tong/statphys/jaynes.pdf where two imaginary variants of Argon gas are mixed together. If one engineer is ignorant of the different variants of Argon gas, it is impossible to extract work from the gas, but armed with knowledge of the difference (which must be exploitable otherwise they wouldn't actually be different) work can be extracted. Knowledge _is_ power. Taking an extreme example, suppose we have two volumes of gas at different volumes / pressures / temperature. We can compute how much work can be extracted from those gases. But, suppose someone else knows more than just the volume / pressure / temperature of these gases. This someone happens to know the precise position and velocity of every single molecule of gas (more practically they know the quantum state of the system). This someone now gets to play a the role of Maxwell's demon and separate all the high velocity and low velocity molecules of each chamber, opening and closing a gate using their perfect knowledge of where each particle is at each moment in time. From this they can now extract far more work than the ignorant person. In both cases the gas was identical. How much useful work one can extract depends on how precise one's knowledge of the state of that gas is.
- danq__ 3y agoI don't think this delivers the intuition in a simple manner. It's also not fully correct. People explain entropy in over complicated ways and even in this thread many people explaining it don't get it. There is a simple way to think about this and I guarantee if you read my explanation you'll understand it more. In essence what you need to realize is that entropy is just a label for an aspect of probability. Things tend to become disordered over time because disordered states are more probable then ordered states. Entropy is thus simply phenomenon of probability... of things moving from a low probability state to a high probability state. That's it. That's really all there is to it. That's all you need to digest, all the complicated math and explanations are all just surrounding the above concept. Entropy is just a high level abstraction of probability. It just allows you to explain things without the intuition of probability bogging you down. For example, explaining life in terms of probability is harder to grasp as it's akin to rolling 10 dice and having all the dice roll a 6.
- danq__ 3y agoThe most intuitive explanation of entropy ever: entropy is a fancy way of explaining probability. Things with higher probability tend to occur over things of lower probability. Thus when certain aspects of the world like configurations of gas particles in a box are allowed to change configurations, they will move towards high probability configurations. High probability configurations tend to be disordered. Hence the reason why we associate entropy with things becoming increasingly disordered. For example... gas particles randomly and evenly filling up an entire box is more probable then all gas particles randomly gathering on one side of the box. If you understand what I just explained than you understand entropy better than the majority of people.
- pcwelder 3y agoSo the law of increasing entropy is not a fundamental law of the reality because it can be derived from other fundamental equations. Suppose I show you a snapshot of a random universe, would you be able to tell if the entropy of the universe is going to increase or decrease as the time progresses? Let's assume that universe's entropy would increase. Consider another universe exactly the same as current universe, but all the particles' velocities reversed. Then this universe's entropy would decrease. So you are equally like to select both the universe and hence the original assumption of increasing entropy is wrong. Discarding quantum properties of the particles, is it then fair to say that time's direction is unrelated to whether entropy increases or decreases?
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- canjobear 3y agoThe expected increase in entropy can be derived from laws of mechanics plus the critical stipulation that, in the past, entropy was very low. Essentially, physical systems want to be in high-entropy states. So if you observe one to be in a very low-entropy state, then you can conclude that with high probability the future of that system will go to higher-entropy states. > Suppose I show you a snapshot of a random universe, would you be able to tell if the entropy of the universe is going to increase or decrease as the time progresses? Yes, if it has low entropy then entropy will probably increase; if it has high entropy then the entropy will probably fluctuate up and down statistically. > Let's assume that universe's entropy would increase. Consider another universe exactly the same as current universe, but all the particles' velocities reversed. Then this universe's entropy would decrease. The key is that you're exponentially unlikely to find yourself in a universe where all the particles' velocities are reversed. See this: https://en.wikipedia.org/wiki/Fluctuation_theorem https://en.wikipedia.org/wiki/Fluctuation_theorem The probability that a system randomly evolves in a way that reduces entropy is very very small.
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- antimora 3y agoJust recently I also watch a video by Sabine Hossenfelder called "I don't believe the 2nd law of thermodynamics": https://www.youtube.com/watch?v=89Mq6gmPo0s https://www.youtube.com/watch?v=89Mq6gmPo0s I recommend this video as well.
- antimora 3y agoThe video did not explain why the sun is a low entropy source. I found this explaining what I am sharing with you: So, the sun is a low-entropy source of energy, and Earth (and everything on it) increases that entropy as it uses and then reradiates that energy. This process is entirely consistent with the second law of thermodynamics. The relationship between light frequency and entropy comes from the fact that entropy is a measure of disorder or randomness. High-frequency light, such as ultraviolet or visible light, is more ordered and less random than lower-frequency light, such as infrared or microwave light. This is due to how light is structured. Light is made up of particles called photons, and each photon carries a certain amount of energy. The energy of a photon is directly proportional to its frequency: higher-frequency photons carry more energy than lower-frequency ones. So, if you have a fixed amount of energy to distribute among photons, you can do so in many more ways (i.e., with higher entropy) if you use low-energy, low-frequency photons. That's because you would need many more of them to carry the same total amount of energy. On the other hand, if you use high-energy, high-frequency photons, you would need fewer of them to carry the same total amount of energy. There are fewer ways to distribute the energy (i.e., lower entropy), so this arrangement is more ordered and less random. Therefore, high-frequency light is considered a lower-entropy form of energy compared to low-frequency light, because the energy is concentrated in fewer, more energetic photons.
- kgwxd 3y ago> The video did not explain why the sun is a low entropy source. Laymen to the extreme but, didn't it? The thing about the low entropy of the universe near the big bang, gravity naturally bringing things together, and such?
- guga42k 3y ago>The video did not explain why the sun is a low entropy source. I found this explaining what I am sharing with you: to my best understanding, to go from high entropy state to low entropy state you need work to do. The sun is a source of energy to do the work
- martythemaniak 3y agoGreat video, but very wrong to cite Jeremy England. Ilya Prigogine came up with the concept of Dissipative Structures and won the Nobel Prize in Chemistry in 1977 for that work. He also has a couple of pop-sci books on he subject that I found super illuminating. They are a little bit challenging to read, but they're very thorough and Order out of Chaos in particular has a fantastic summary of 400 years of philosophy of science. Highly recommend reading the OG.
- ctafur 3y agoAccording to entropy, and thermodynamics in general, I can't recommend enough the notes [0] of prof. Zhigang Suo of Harvard. It's a new way of presenting thermodynamics and I finally get it... contrary to when I took a thermo course at university. [0]: https://docs.google.com/document/d/10Vi8s-azYq9auysBSK3SFSWZx64NUGnqBkmHYYQU9Bw/edit https://docs.google.com/document/d/10Vi8s-azYq9auysBSK3SFSWZ... Also prof. Suo puts entropy as the main character of the "play". The other concepts (temperature, etc.) are defined from entropy.
- Lichtso 3y agoI think the most unintuitive even unsettling aspect of entropy is that the entropy of black holes is proportional to their surface area, not their volume [0]. That is only briefly mentioned in the video and not discussed any further. [0] https://en.wikipedia.org/wiki/Holographic_principle#Black_hole_entropy https://en.wikipedia.org/wiki/Holographic_principle#Black_ho...
- contravariant 3y agoTo be fair black holes are just weird so that's not too damning on its own. What makes it weird is that black holes must necessarily* have the maximum amount of entropy for a specific volume. So not only the entropy of a black hole is proportional to its surface area, but the entropy of some volume of space can not grow beyond that. In particular entropy cannot be proportional to volume without limit, the density must be 0 on average for a big enough region. *: According to some people anyway.
- spiralx 3y agoThe surface of a black hole is also the most efficient information storage possible - each 2x2 Planck lengths area can store a single bit. Of course there's no way to read that data...
- max_ 3y agoSad he didn't talk about Shannon Entropy
- friend_and_foe 3y agoThe video talks about how the earth radiates away the same amount of energy as it gets from the sun, just red shifted. In light of this, let's talk about climate change, global warming and the greenhouse effect.
- sourcecodeplz 3y agoIt was a great video
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- northlondoner 3y agoThere are multiple different definitions of Entropy and usage. Boltzmann's and Gibbs's physical entropy is not strictly equivalent to information entropy of Shannon whereby legend says von Neumann told Shannon that call 'information capacity of a channel' entropy, as nobody knows it. A great reads from books of Arieh Ben-Naim is highly recommended.
- wpwpwpw 3y agoI loved this one too and I believe it is an excelent followup: I don't believe the 2nd law of thermodynamics. (The most uplifting video I'll ever make.) @ https://www.youtube.com/watch?v=89Mq6gmPo0s https://www.youtube.com/watch?v=89Mq6gmPo0s
- subroutine 3y agoIn the video, Derek says the sun provides "a more useful form of energy than earth gives back because it is more concentrated". I would argue this is not technically true. What makes the energy from the sun useful is that it emits blackbody radiation, and this has photons that are more energetic than heat (IR) radiated back into space. Light with wavelengths between 400-700 nm are used by plants for photosynthesis. Heat radiated back into the atmosphere is mostly in the IR spectrum. This is both quantitatively and qualitatively important due to the quantized properties of electrons orbiting nuclii (IR wavelengths cannot readily to elevate electrons into a greater energy state). see: https://youtu.be/_vK5KPycEvA https://youtu.be/_vK5KPycEvA
- topologie 3y agoRelated: "I don't believe the 2nd law of thermodynamics. (The most uplifting video I'll ever make.)" by Sabine Hossenfelder https://www.youtube.com/watch?v=89Mq6gmPo0s https://www.youtube.com/watch?v=89Mq6gmPo0s