I don't believe the 2nd law of thermodynamics. (The most uplifting video I'll ever make.) 

As Abba said: "Entropy killed the radio star..."

I have witnessed water running upwards from a ditch onto a road then becoming airborne and creating a cloud. But, it was because of a tornado passing near to my house and I hope never to see anything like that again.

If I don’t shower, all the good air in a room definitely moves into the corner.

Sabine, I'm a chemist, and in conversations in the past, I attempted to make the arguments about entropy you've made so eloquently in this video (especially the associations/ideas about order). From now on, rather than arguing, I'll recommend watching your video. Thank you so much for this great video!

“and luckily so because it would be inconvenient if you entered a room and all the air went to a corner” just made my day

“My videos can only go downhill from here…” The perfect ending to a video about entropy! 😂

"It can only go downhill from here" Sabine's humor, much like our universe, is chaotic.

To some of your vids, I come back months later again and again, because they are lovely every time new. This is one of them.

You should read Asimov's story called "The last question". It covers the topic of entropy and this video explains perfectly the science behind it. The story also follows Sabrines idea about future life forms in higher entropy universe. It is one of my favorite Asimov's pieces.

THANK YOU for pushing back against entropy being described as order vs. disorder! Through years of schooling entropy was this poorly defined, almost spooky concept of order. Then I was finally introduced to entropy as probabilities of microstates (with gas in a box), and it was completely logical and clear.

A friend of mine once said ”if studying physics doesn't humble you, you're doing it wrong."

Thank you for making clear to me what entropy is and as a bonus giving me a solid idea of what Necessity could mean as well .

This video reminds me how it always frustrated me in school as well as later at Uni that things were described or defined in simplified ways that made them wrong, harder to actually grasp or both. Sometimes the actual truth of the matter would slowly reveal itself often leading to an „aha“ moment years later and a feeling of „I knew it“. Also funny how oftentimes simply explaining the meaning of a latin or greek term would have almost explained the whole concept behind it, yet somehow no professor ever did that.

I'm a mechanical engineer who focused on thermodynamics in college. Despite years of study and using entropy in formulas, this is by far the best explanation of entropy I've ever heard.

This has brought me closer to reconciling questions I've had about entropy than I've ever been before. Thank you for that.

This is a great philosophical point. I love your subtlety, Sabine.

I enjoy your sense of humor keeping things light and entertaining while simultaneously tackling deep concepts. Great blend.

Aging biologist here! I’d like to add an uplifting comment to this uplifting video. :) I’m always a bit sad to see entropy given as the reason we get old. As Sabine discusses later in the video, open systems with access to a source of low entropy can use that to decrease their own entropy, so given that we can take in low-entropy food, there’s no in-principle reason we couldn’t use this to keep the entropy of our bodies roughly constant with time. So not aging is totally allowed by the laws of physics! It’s even well within the laws of biology-there are plenty of animals that don’t age, from tiny hydra to giant tortoises, and even one of nature’s most beautiful animals, the naked mole-rat. Their risk of death and disease doesn’t change with time, which basically means they keep their entropy constant throughout their adult lives. Now all we need to do is crack this biological entropy preservation using science…but that’s another story!

Sabine’s Carnot efficiency at explaining this stuff is 100%.

I’ve been hoping to hear something like this from you. Thank you for this.

Thanks Sabine! This makes me appreciate my current stat mech class more!

I completely agree with you. When I was young, I used to tell my mom that my room was never in disorder because disorder itself doesn't truly exist. Instead, what exists are infinite states of possible order, and none of them holds more inherent sense than another.

9:55 Finally someone said it! I always considered a homogeneous mixture as "ordered", contrary to how lots of entropy explainers describe it as "disordered". This led me to lots of confusion over the years, until my recent physics classes cleared things up.

She’s an excellent teacher and her dry humor is hilarious! Love her!

This is the best explanation of entropy I’ve heard yet

LOL “I’d be inconvenient if you entered room and all the air went into a corner” @sabine you totally cracked me up with this joke. Thank you!

The entropy of RU-vid must have decreased since veritasium and Sabine both posted videos on entropy within two weeks of eachother :) They're both great, but Sabine definitely lives up to her motto of no gobbledygook... thanks Sabine!

Excellent video on entropy and statistical probabilities; thank you, Sabine!

Thanks Sabine, I am a curious dilettante in science and I really enjoy being able to understand a little more about everything that science has advanced.

This is the coolest clearest and most concise explanation of entropy ever. I wish my physics professors had taught it this way. It would have saved me so much sleep.

The idea that there are always macrostates capable of turning a high entropy system into a low entropy system is fascinating. Entropy being constant, but perceived by us macrostates as variable, and thus subjective is powerful. I love how more and more physicists are adopting such a perspective! 😁✨

One of the best commentaries on Entropy I've encountered thanks SB, especially as "The # of microstates per macrostate" - Given that a macrostate is simply an arbitrary human classification/aggregation, does this mean that entropy is an arbitrary physical aggregate outcome? I think I'm missing something, so I'll listen to your commentary until I can discern this thing. 🥝🐐

Entropy change expresses the potential for change of the state of life. It seems more interesting and philosophical than anything else. I do like your description of changed entropy for the future and what it could mean....a crazy world indeed. Very good views...thank you!

This remembers me of the book "A Choice of Catastrophes" by Isaac Asimov. He talks about how to survive heat death by exploiting low entropy fluctuations. The book was written in 1979.

Thank you for delivering such great content 👏 always interesting, humorous, and informative. My field is engineering, but sometimes, I regret not pursuing physics. Watching your videos gives me a chance to see what I missed.

Thanks Sabine! A few years out of college and missing my p Chem courses, this brought back happy memories

Probably one of the best explanation of Entropy. Thanks for the video.

Intuitive explanation of entropy. Thanks a lot

Me encanta la profundidad y claridad que tienes, este tipo de contenidos es oro. Yo estudié Física y Filosofía y una conversación contigo me hubiera ahorrado años de dudas y confusiones. Gracias por esto.

Thank you so much, it sheds some light on the entropy for me =)

_"Not enough data for a meaningful answer."_

I've always read the term heat death as the death of heat, which made a lot of sense to me.

Great video! But tiny correction: high entropy means high information, not low information. The more random something is, the least it can be succinctly explained. At least for Shannon Entropy. For instance imagine water in its solid form with molecules neatly aligned, it can be described succinctly as a pattern repeating, whereas in its (high entropy) gaseous form, each particle can be anywhere in a the volume that contains it: describing the micro-states would require describing the position of each molecule (high information).

I’m not old, I’m just high entropy.

😂 Much credit given to your intellectual sense of humour. Great work on the presentation, Sabine! 🎉 😂

"It can only go downhill from here" made me laugh out loud. Another excellent video that teaches us about science. Lovely.

Sabine your work has changed the very way I view life and physics in a way that's nearly spiritual. I feel so lucky to be able to learn about the beauty of the universe and physics from you

13:37 this is key, thanks for all the clear explanations and happy to see you got ready early for movember

Sabine is not only intelligent enough to master a complex subject, but also think in new ways about how the data should be interpreted. It absolutely blew my mind when you explained how macro systems are a relative concept, and not an absolute value that happens to match our anthropocentric view of the universe. Thank you.

I have been trying to understand entropy for decades, now I am a little closer to it.

The statistical description of entropy has never resonated with me, but your talk about other life with access to different macrostates is very interesting, and warrants further thought.

thank you for this wonderful video and for all the others. you have kindled an interest in physics in me.

Very nice! It's refreshing to hear someone talk about Entropy in this manner. When I teach thermo, I always emphasize that Entropy is not about order or disorder. But, I don't know what those terms mean in a quantitative sense. Second, the analogy of the universe being in 1 microstate per microstate is spot-on correct. The thermodynamic definition of entropy dS = dq/T (for a reversible process) also ties into this analogy. If the universe's entropy increases, then heat (dq) must be added...but from where? That "where" can be incorporated into your definition of the universe, which moves the "where" to somewhere else, und so wieder/ So, one is faced with the notion that the universe expansion must be adiabatic (dS = 0)....which is a beautiful problem in Callen's Thermodynamics book.

She is wonderful at explaining very difficult or (almost) impossible ideas in an understandable way. Alas, even Sabine leaves my poor brain often mystified, but always stretched, curious, and entertained. 🙂

Very interesting point about 'macrostates' that I've never heard or thought of before. Definitely food for thought. Thanks!

Love the videos Sabine, especially the hand waving - are you trying to hypnotize us?

I really like this video and it helps and enables a better understanding on physics.

Sabine s humour and wit is so empowering. Such a wonderful person. Thank you for existing Sabine 😂

I've been waiting a long time for this video. Sabine, you are an amazing communicator and I think the world needs to hear you. This channel and other sources like it are THE REASON I use the internet. Thank you! ❤

I recently learned that Planck was highly motivated by believing in the 2nd law, but was still reluctant to embrace atomism. What I seem to remember from either a P Chem or a Chem E course that entropy, or was it enthalpy(?), is a calculable quantity that plays a role in the equations much the same as energy. We can recognize that it is a construct, but it still plays a role in our modern frame of reference. I think it is something still worth pondering as Planck did so I thank you for the video , although the first 8 minutes of textbook regurgitation make me want to pound my head on the desk. Actually I dont own a desk, just a sewing machine table so I can make my sails and escape to my ocean sabbatical,,, maybe then I will understand entropy

Lots of mistakes to address here so I’ll just start with Heat death and why it will happen. In your box example you said particles on one side of the box and particles allowed to flow through the whole box have the same micro state. This isn’t necessarily true, but is built on a naive definition of micro state and a naive interpretation of particulate motion. For one, the particles in the right side of the box are moving with a specific average velocity within a specific volume. If those particles are then free to love in a larger volume, their average velocity decreases, increasing entropy. The two micro states are not the same, as their volumes differ. If we apply this reasoning to you “reservoir” analogy (I really like that analogy), we find that the volume of space occupied by light is smallest near a reservoir (this is due to both angle of incidence and gravity, as gravity stretches space near a star, causing a lensing effect). Further out, the light dissipates energy by transferring heat to particles and loses volume due to cutting a greater angle through space and reduces lensing as it moves away from the strong gravitational pull of the star. At some point in the distant future, the size and number of reservoirs will be too small for the energy of light per volume of space to spontaneously generate virtual particle pairs. Beyond that, the EM field will vibrate at too weak a resonance to generate large enough motion in particles it interacts with, thereby making particle collisions less likely and temperature to drop. This is the heat death.

For a mortal being with a life expectancy of ~80yrs I confess I spend an irrationally large portion of my life brooding on the eventual heat death of the universe. Glad to find videos like this on occasion which at least try and come up with a philosophical explanation for why we shouldn't feel depressed over the stars eventually going out. Kudos Sabine!

Sabine has just addressed a question I been tickling me since my teenage years. This notion of pockets of emergent decreasing of entropy, such as say, our brains. I'm so grateful to hear her address this topic.

Thank you! Your videos are brilliant and offer a different perspective that is not found in school or textbooks!! They contain valuable insight that anyone with an interest in this topics absolutely should watch. One question regarding your explanation about the micro states - in the examples often cited eg breaking an egg, air molecules expanding to fill the space etc - that contains an assumption that all the available micros are equally likely, and have the same probability distribution of containing the object. But I somehow doubt that no matter what happens an egg will not rejoin itself or water will not spontaneously form itself back into a raindrop and go back into the clouds. So my question is, how does one handle micro states for which probability distributions are not equal but actually zero? I mean have there been experiments done where very unlikely micro states become inhabited per the nonzero probabilities that you would expect? I would expect to prove that the logic as described applies then there must be some measurable quantity of unexpected events happening in a controlled experiment? Sorry if this sounds trivial or stupid, but I was just something that was bugging me. Thank you again ! -F

Finally a video makes the topic crystal clear. And the comments anout macro vs micro states was incredibly logical and very interesting. This should be the ultimate video on entropy.

Videos that provide a "simple understanding" of historically complex concepts (like the laws of thermodynamics) are crucial for our kids to hear and learn. I am especially interested when the video explains what we "don't know" or "don't yet understand" to pique their interest in what to solve next!

This reminds me of Roger Penrose’s ideas. I think you shared a stage with him at one point. If we change our scale of looking at the universe, in both space *and* time, the almost uniform distribution after 10^100 years (or whatever the number is) becomes recognisably clumpy again. The almost imperceptible effects of gravity speed up and become perceptible again.

If anyone here has NOT read Isaac Asimov's short-story "The Last Question", now would be a good time.

Great and simple as usual😊

I love your channel Sabine. I've been following you for a long time (we even had an epic argument on Twitter _many_ years ago) and it makes me happy that your channel is doing good!

That was one of the best lectures although it is hard to compare lectures. It's maybe the first time entropy makes sense even though I have been reading about it all my life. I also like your dry physics humor. One needs humor in life. So thank you very much.

Ive been trying to explain this to students for years, this video is spot on 🤝🏻

I have to say: her jokes are rather as you would expect them to be from a German

Fascinating video and very well explained; entropy has always been one of these quantities I've found difficult to define or understand. It has mostly been explained to me in the concept of order (or just plain equations), and those mostly just made me go ‘oh that makes sense... wait.’ Minor note, Boltzmann has two n's. 😅

I like how complexity emerges somewhere between minimum and maximum entropy :)

Simple question- the partciles that constitute the body of a living organism are highly ordered and constantly work towards repairing damaged parts- HOW IS THIS POSSIBLE IN A WORLD OF EVER INCREASING DISORDER?

I'd love to see Sabine discuss that with Sean Carroll, also a brilliant scientist who put a lot of effort into the science behind the arrow of time. Sean, why don't you make a podcast episode out of that?

This is truly your best video IMO. Thank you Sabine! Finally a happy ending, from which, as you said, everything will have to go downhill 😂

I think many of my (undergraduate) students would get a laugh (or a cry) out of the phrase, '...You don't need to know that much maths, just differential equations and probabilities...'

Very nice and easy explanation.

🎯 Key Takeaways for quick navigation: 00:00 🌌 *Introduction to Entropy and the 2nd Law of Thermodynamics* - Introduction to the concept of life requiring order and structure. - Physics perspective on entropy and its connection to the increase in disorder. - Questions about the accuracy of the 2nd Law of Thermodynamics and its implications. 02:26 🚗 *The Arrow of Time and Probability* - Explanation of the "arrow of time" and its connection to the likelihood of events. - Discussion on time reversibility in physics equations. - Importance of initial states and the probability associated with entropy. 05:00 ⚙️ *Entropy, Equilibrium, and Work* - Definition of entropy as a measure of system likelihood. - Explanation of equilibrium and its role in defining useful energy(work). - Practical applications of entropy in physics and daily life. 07:42 ☀️ *Entropy, Reservoirs, and the Fate of the Universe* - Discussion on the Past Hypothesis and the low entropy start of the universe. - The role of entropy in the increasing disorder of the universe. - Utilization of low entropy reservoirs like the sun and fossil fuels. 09:33 ❄️ *Heat Death and the End of the Universe* - Explanation of the concept of "heat death" as the eventual fate of the universe. - Clarification that "heat death" doesn't imply a hot end but rather a state of maximum entropy. - Discussion on the exhaustion of low entropy reservoirs leading to a cosmic standstill. 10:25 🌌 *Entropy, Order, and Perception* - Clarification of the confusion surrounding the relationship between entropy and order. - Examples of seemingly ordered situations with varying entropy. - Discussion on the subjective nature of human perceptions of order. 12:12 🔄 *Entropy, Microstates, and the Second Law* - Explanation of microstates and macrostates in the context of entropy. - Assertion that the second law doesn't strictly state an increase in entropy but rather a lack of decrease. - The role of information loss in the perception of increasing entropy. 14:26 🌐 *Entropy, Quantum Mechanics, and the Future* - Discussion on the relationship between entropy and information in quantum mechanics. - The proposition that complex systems may emerge, reducing entropy for those systems. - Speculation on the future of life in the universe and its potential forms. 15:51 📚 *Conclusion and Brilliant.org Sponsorship* - Summary of the video's main points about entropy and the 2nd Law of Thermodynamics. - Encouragement to explore further learning on Brilliant.org. - Information about Sabine's own course on Brilliant, focusing on quantum mechanics. Made with HARPA AI

According to entropy at some point we're going to come back to this video and say "well this didn't age well" 😉

So much food for thought. One of your best yet Sabine.

Great video, as usual. Sabine really puts things in perspective with her very humble scientific admission of gaps. Around the 7th minute we can visualize clearly what is the greatest bias (blindness?) that will make our grandkids cringe in a century: "how could you not understand this emergent order?" To me it feels like it's way past time we start conceptualizing things like "syntropy" and eutropy", and take Metaphysics seriously again. Restore it to its natural place since Aristotle: the real "theory of everything". Intuition (idealism) is the way we understand things so that science can make strides again. Empricism depends on it, and is basically a secondary development.

This is a really good video on entropy. I now know why all my things keep breaking! 😅

Great video Sabine! Even if I have a MSc in chemistry and PhD in pharmacy, one of the hardest thing to undetstand is the thermodynamics. You really have to eat and breathe thermodynamics to really understand it, and it doesn't come with intuition, and one of these things are entropy. So thank you Sabine to make these entropy more intuitiv.

I have had major depressive episodes because of entropy and the second law. I am deadly serious. Since learning about it in high school physics class, I have always considered it to be my greatest fear. Thank you for easing my fear a bit. 😊

“Meanwhile entropy is exactly what I thought”… me: fighting with my inner voice after reading thumbnail.

This is the first time I’ve left a comment on RU-vid. And this is really uplifting. Heat death is too sad.

How did Sabine know I was about to ask, “But what about Quantum Mechanics?” Spooky action at a distance at work?

The analogy of "disorder" can work in the right context. You could say: there's all kinds of messy but only one kind of clean. For that reason your room tends towards getting messy if you make any change not specifically targetting cleanliness. What I like about the example is that it uses the cleanliness as a macroscopic state defined by a human and talks about the associated microstate count.

For the life of me I don't remember where I first heard "life is the postponement of entropy" but that quote has stuck with me since I was about 15 or 16 years old so had been a factor in my thinking for over 30 years now. It is nice to see someone talk about life vs entropy.

Wow, this is so far above my head it’s funny. But it is amazing to hear this kind of analysis done by someone so educated. I agree with the concept of entropy not being the opposite of order. That never sat right with me, either. Love your work! ❤

Hi Sabine, I think this is imo one of your best physics presentations yet. Explaining entropy and how it applies to pretty much all aspects of nature. Thanks.

Beautiful! I was wondering whether the "entropy reversing" influence of "life" would arise, and it surely did! Joy arises. Thank you.

Speaking of entropy, can you please make a video about carbon capture and storage? I think the subject could use some of your analysis! There is so much misinformation out there about it.

I don't understand what Sabine is saying at the very end, about other life forms. Up to that, fine. She says first that the universe is in one microstate per microstate, always, and always with zero entropy. I can see that, using the analogy of the partitioned box, whether the partition is in place or not and whether the molecules are in half the box or in the full box. The states of individual molecules (mass + energy) are the same in each case. She then applies that to the universe, declaring that there is only one microstate in the universe, whether or not there are "partitions," such as stars, planets, black holes, etc. She's saying that we humans are artificially looking at the macrostates for our own purposes, and as far as the universe goes, it's only in one microstate at zero entropy. I get that. So she must then be saying that the increase of entropy in conjunction with the arrow of time that physicists teach us is an artifact of our dividing the universe into macrostates. Fine. But what does she mean by saying there's a possibility of other life forms appearing? From where? From the same universe? How can that happen? What region of lower entropy can provide for such life forms (macrostate)? Near Heat Death, there will be next to no concentrated bits of matter or energy from which to construct - or imagine - any macrostate. I do see parallels here with Penrose's idea that at Heat Death, the universe forgets itself, unable to distinguish Heat Death with the instant of creation, and so with no distinction, Heat Death again becomes the first instant of creation. And on and on. But Sabine seems to be wading far more into speculation here, and I don't see the basis for it. Am I wrong?

I read a while ago that they made a tiny membrane out of graphene that could harvest minute amounts of electricity from brownian motion by vibrating the membrane. That's pretty cool because as I understand it, it would mean that if you're in a sealed sphere that doesn't lose energy, you could in theory produce energy out of seemingly nothing by cooling the air to convert the heat to electricity, which in turn would do useful things before inevitably heating the air again.

i think using the term "stability" is better than the term "order". You could say that a system with low entropy is unstable and has a tendency to collapse into a more stable state

Perfect timing. I am reading The Order of Time by Carlo Rovelli. And the low entropy Google algorithm sends me right here. Always enjoy your explanations. Well worth my subscription.