Your Daily Equation #32: Entropy and the Arrow of Time 

I'm not sure if you read the comments posted following your videos, or would even have the time(!), but I'd like to offer a heartfelt thanks for them, and to remark that I cannot get over how much time you willingly give up to educate, entertain and inspire us. So, so generous. Thank you.

Mom: Get your life together. Me: Can't Entropy.

Hi Professor, Thanks for Ur lecture Lots of love from India God bless you BG

I stood in front of the tombstone of Boltzmann in Vienna on friday 13th on my 50th birthday, just days before the world went corona 'crazy'. The cemetery was almost closed, it was hard to find, but in twilight even more impressive! This is an equation that will last.

All the Daily Equations have been perfect. I can't wait for the next one. BUT, This one is so great to get a feel for the laws of thermodynamics. Dr. Brian is brilliant in explaining principles that are challenging to dumb asses like me.

This episode was sponsored by Christopher Nolan, so that you can understand his upcoming movie, TENET. Entropy and arrow of time. The inversion.

i wish he continued these

Leo Tolstoy also observed that there are more disordered states than ordered ones in Anna Karenina: "Happy families are all alike; every unhappy family is unhappy in its own way."

All I can say is that my desk has a very high entropy and is extremely unlikely to decrease any time soon!

Fantastic professor Brian! I think this has been the best explanation I have ever seen about entropy!! I feel happy to say this! Thanks for all you have gave to us!!

Thank you for these videos! I'm not a student in physics, but I've always had a great interest in it, and I've learned a lot from these sessions. Thank you again and take care, stay well and safe!

I've never been addicted to something like this...this much! Thank you Dr. Greene for your valuable insights and wisdom through this series and thanks a lot WSF!

From explaining the Big Bang to demonstrating the basics of General Relativity on TV with Stephen Colbert, you have made difficult scientific ideas understandable to us all. Science dorks around the world owe you a huge debt. Thanks a million, Dr. Greene.

My man who’s been in all sorts of amazing documentaries with amazing visuals and broad strokes of theories- literally now has me back in AP Physics just as confused as ever once the X and letters enter the picture lol. Almost had some flashbacks there till I remembered how my teacher taught us how to manipulate the reference sheet ;) but this is what happens when science communicators can backup their statements with the cold math... Thanks as always!!!

Thanks so much for taking this question up that I requested in the second episode. This was a really good refresher! Thanks very much again Prof.

Thank you Prof. Greene! I really appreciate your ability to take complex topics and make them easily digestible for anyone (sign of genius). I especially enjoyed how you maintained your focus and train of thought while the phone was going off. I wish I had that skill - fun! Oh...and is it Ree-dl like needle? Someone please solve that problem too (wink).

Wow, I've never ever learned so much about entropy in such a short time. It would be very interesting to hear more about this from Brian. Too bad it's the last episode ...

Used to decide whether or not to buy a dictionary on their definition of ‘entropy’, it was surprising but common to find dictionaries with no entry for entropy.

This was superbly helpful. Greene made the subject matter interesting throughout! (Thank you!)

What time to be alive having these videos from great minds for free. This is a rare moment in history, our world with Electricity providing the internet is very fragile, maybe in a few centuries all this is lost, cherish and embrace your time alive right now

I did appreciate every single minute of of all 32 sessions , i thank you dr.brain green

Truly enjoyed your descriptive explanations. Found it interesting and unusually understanding for the most part. Thank you so much.

my appreciation of Brian Greene grows daily !!

Loved it. Thanks, Brian.

Thank you professor... Respect from India ❤

Brilliantly explained Prof !

Whoa.... great lecture Sir ! Especially tht statement about the anchor/ residual order... of Big bang tht sort of gives order to our current ordered stuff !

Thank you Prof. Greene; very interesting as usual ! So that's why time travel is forbidden, because it would reverse the tendency of entropy to grow. Regarding the arrow of time, you said that things fall in order to reach a region of spacetime where time is slower. Could it be that "falling" should be a way to escape from a region with high entropy (because time is faster so more configurations happen) to another with potentially less entropy due to a "shorter" arrow of time ? Taking this reasoning to its extreme, it is correct to say that if time stops entropy doesn't grow anymore? Another crazy idea: could it be that traveling through time is much more "expensive" than traveling through space ? (I'm talking about components of spacetime) Because when there is a component along the time axis, things "age" (there are changes of state) and so entropy grows...(maybe the Universe tries to fight entropy with gravity). Sorry, but all these lessons unleash my fantasy :-)

Just came across your videos and love this format. So many others have over the top splashy videos and graphics that usually just distract from the topic at hand. Much prefer your approach. Please keep it up! Love the ringing telephone… real life at its best 😂

Your explanations of math and physics are awesome. Id like to see a Physics of Music episode sometime.

What a surprise! An interesting, informative, and articulate description and explanation from Brian Greene. I love these sometimes daily equation sessions and will sure miss them when Dr. Greene stops giving them.

Fantastically explained 👏🏻👏🏻🙌

I deeply appreciate your videos and the knowledge you are sharing with us. Thank you!

i love u brian!!

This is greatness !

Yes! Thank you Professor Greene!

Your content never fails to amaze me and ignite my hunger for knowledge about the universe. Thank you for sparking my curiosity.

Artificial atomic structures created by electrochemical resonance will help us to take the first steps in dealing with this great chapter talking about the reversibility of time. Thank you.

Great explanation 👏👏👏

i only recently found this channel. most explanations concerning physics blow by me. but i can understand yours to the point i at least know what you are talking about. I'm not educated but i'm life long curious. Thanks. first saw you on star talk, now i am a fan. you do a great job illuminating einstein's work for non physicists.

These daily equation is awesome.

This is the first time I’m watching the video, and it’s already blew up my mind😱 while watching this video I repeat in many times to understand it again cause I really excited about the topic and how I hypnotized by Prof. Brian words🤔. I truly encourage with this topic and I really really appreciated this one. Thank you so much for sharing. Greetings from Indonesia 🇮🇩

That's the most beautiful explanation of entropy that I have ever heard

Thank you profesor for a very interesting lecture.

Such beautiful, almost poetic explanations. Outstanding. Thank you, Brian.

Beautiful, indeed!!!

Thank you Doctor. Greetings from Romania.

Thanks, Brian.

That is extraordinary! Thanks to Prof Greene! I have learned much today, and also today I have more questions than yesterday. For example: if laws of physics allow reverse entropic "trajectories", what about irreversible chemical reactions, such as combustion?

Beautiful!

Thank you Prof. Greene. Your simplification of Entropy rocks! Q. pls, is it possible to get a copy of the code for the coin simulation by Danny Swift? My 17 year old Nephew loves it.

Great explanation.

thanks prof GREENE

Great lecture

Terrific!

Brilliant, TY for not editing out the phone. Now we know your human like everyone else! :)

We love you Sir

You changed my thinking on entropy,😍😍 beautiful explanation

Prof Greene .my name is Eran Sinbar from Israel . Its a pleasure seeing your inspiring videos and read your books . a major question that bothers me: could it be that our known local fabric of spacetime is divided into Planck length sized spacetime cells and between them there is an extra non local grid shaped dimension (or dimensions) that is responsible for the non local quantum phenomena like for example entanglement? could this extra dimension conceal the non - symmetry in the arrow of time?

Times is so sensitive,and we should liked any second of it , let’s have some rest after few year’s hard work and been refresh for next

nice job Sir !

I'm 56 years old and this is the first time being introduced to how equations are used to prove or disprove what is possible in our world. This helps me with my aversion to laws because in my world laws are not backed up by any kind of equation. These are the laws of the just diss sis dumb (justice system). Being exposed to the laws of the justice system prior to being educated in the laws of physics should be illegal. How can one defend oneself against unjust laws or unfounded laws with no ability to prove the unjustness of the process's ones being held accountable to? How can any educated judge attorney or attorney look at themselves when in our system should I need a jury of my peers to judge me it would be necessary to have a jury made of children 8 and younger? How is it possible to live in a world where there is such a vast amount of knowledge and be kept ignorant of it for over fifty years? Once again RU-vid and the creators who share their knowledge by creating useful content are rescuing me from the pit of ignorance. It's very difficult to not become outraged in these moments of elation that bring to the surface years of painful alienation and suffering induced by the hunger for substance and reason. Listening to this video makes me imagine what it would have been like to be raised by people who had been educated and how differently I could have patented had I actually been an autonomous educated adult before trying to create and set an example for new life to emulate. Thank you so much for this video. I'm surrounded by folk who think having more knowledge than another makes them more successful so there is not an atmosphere of progress. It's an oppressive and smothering way of life. I hope it's not too late for me to integrate these knowledge u to my DNA and save my children from the ignorance of myself so they don't end up in the loop my family has been circling in for generations now. I do not function in a world that has consequences for problems but no room for solutions. No desire for solutions. Even as my country is falling into decay before our eyes there is only slight begrudging changes aimed at preventing problems rather than a justice system feeding off its victims.

정말 대단한 강의입니다. 책을 통해서는 잘 이해가 되지 않았었는데 이 영상을 보고 완벽한 이해에 도달했습니다. 수학 부분은 빼고..ㅎㅎ 엔트로피, 열역학 제 2 법칙 또는 경향, 시간의 화살 그리고 빅뱅 시점에서의 고도의 엔트로피 질서를 갖고 있었던 이유로....우주가 팽창하면서 질서에서 무질서로 진행하는 과정에서 별과 은하계 행성 지구 그리고 인간과 같은 고도의 질서체계가 발생할 수 있는 원리 등등... 브라이언 그린 교수에게 감사드립니다!!

Thanks again Prof. for another great episode. Have you considered doing an update of "Fabric of the Cosmos" ? I would buy the DVD again !! All the Best, Paul C.

We are waiting for you sir ... Come soon... U r the best teacher of secrets of this world... Salute to ur genius mind and gentle nature towards giving water to our thirst curiosity. Lots of love and respect from India🙏

incredible lecture Sir as usual. That provides so many foods for thought, for instance if the condition at the time of big bang was in super order what sort of thing that might have been. If life is the result of residue of that order, what kind of consciousness that actual order would have possessed. Are multiverse and parallel universes not accessible by us since they fall under the category of higher entropy, and so on and so forth

Uhh, amazing again. Thank you!

Please make more videos on this

Wonderful presentation. It made me imagine the "stuff" of the universe in its primitive form smeared out over a spherical de Sitter space fluctuating around maximum entropy until finally enough of that primitive "stuff" converges at a point causing a region of minimal entropy which thereby gives birth to a system similar to the one in which you and I currently exist. Maybe extreme spatial curvature at the convergence point causes an outlying region of repulsive flatness which results in separation from the parent de Sitter universe thereby allowing the system to evolve on its own without influence from the parent de Sitter universe until eventually, when a high enough entropy occurs and/or spatial effects ease, it rejoins the parent de Sitter universe.

2 questions: The arrow of time was wonderfully explained (2nd Law + residual order), thank you for that. 1st QUESTION: does this means that the arrow of time loose any meaning when the maximal entropy was finally reached? 2nd QUESTION: by the used example the motions where equally probable, randômico, like by diffusion. How would entropy evolve if we do have a preferential arrow for motions, when there is a slight higher portability in one specific direction, like by the migration of charged particles in an electric field?

Honest Question I would love an answer to: To Preface it, I will start with - Since we understand entropy by virtue of witnessing and experiencing it, then we see that time moves forward.... and that is based on the information we receive. When people talk about going backwards in time, the assumption they make is that they will carry... some sort of information with them that will be the catalyst for change, leading to a different future outcome. ....seems to me, however, that if we reverse time, we lose information. If I didn't know what the word "photosynthesis" meant and you explained it to me, I would learn. going backwards in time means returning to before I knew what the word meant. If I am returning to a point where I didn't know the meaning of the word.....I lost information. so, my question is the following: If we went backwards in time suddenly.... how would we even know? What test could be done where entropy is measured, then time is reversed and no information is lost? If I see a glass of milk and think "I will trip and spill this if I don't watch out for the cat" ....then the cat runs in my way, but I don't spill any milk..... obviously, that doesn't mean I tripped over the cat, spilled the milk, went back in time and 'intuitively knew' to avoid the approaching cat. So, is it possible that time, say... oscillates and we are unaware? if so, how could we tell either way? I've asked this before and the only answer I got was "we wouldn't survive such an experince"..... which makes no sense. You would be returning to a previous point in time..... where you were alive. if you survived making it through time the first time, you would go through the same stream of events you just went through. you survived it once....why would you die the next time? ......just curious. I'm probably not intelligent enough to get why this is a silly question but, I'm fine making an ass of myself... so, learning in the process isn't going to do me any harm 🙃

Around 3 minutes in, I started to think about entropy in a different way. Those 3 examples were very good for building up the concept

Interestingly, this explains why the Moonwalk is such a sensation! MJ and the others reversed a natural phenomenon: WALKING. Thank you Prof. Greene for a very easy to digest method of explaining Entropy.

To reverse the broken glass, would you also need to somehow supply (or remove) heat to cause the bonds to re-form to convert it from a bunch of silicon shards into a smooth glass?

By the glass breaking example, not only every motion must be reversed but also the chemical reactions, with the recombination of many Si-O bonds. Overcoming their activation energies is necessary, as well.

Declare professor Greene the rockstar of science world 🤟🏼

Thanks prof. Greene, nice lesson as usual. Question about the past hyphotesis: how can we considered the big bang an highly ordered state? It was a hot soup of photons and high energy elementary particles chaotically moving. Has that to do with gravity? I believe I heard prof. Penrose discuss this but I'd like to hear your point of view.

Dear Professor Brian Greene, Hi. I just want to say - thank you for having these videos. Are you familiar with Edgar Cayce?

Hello!I was thinking about the energy conversion points...Could we consider these points as sensing sensors in an electromagnetic band type system?I await your response.Thank you!

For more on this subject, I recommend Leonard Susskind's entertaining and enlightening talk on Time as a One-Way Street.

Prof. Greene please make a video on quantum gravity

Dr. Greene What do you think about the idea of, when dealing with a local system (for example 100 pennies on your table), that a person can identify and then flip each individual coin to produce an ordered state. How does this relate to the tendency to disorder? Is this because energy is introduced into the system? Just curious.. thanks!

Finally, i thought he gave up on us

The low-entropy of big bang brings back again the concept of creator.

Hello! I thought about the Brownian movement that would ensure the formation of other structures, but regarding the broken glass experiment on the frequency line, to ensure reversibility,Before the experiment we have to create a linear transformation system, which restructures my atoms, forming these artificial atomic structures. Thank you!

Dear Dr. Greene, can you please help me understand something i never could find in any of the programs about double slit experiment. Every program says interference pattern breaks down to definite particle state once measurement is done by detector but nobody says how the detector actually measures the "which way" path. Is the detector some kind of a passive screen or does it shoot a beam of laser to measure the path or something else? Some scientists says that interaction with another particle breaks the interference pattern- in that case there are already so many particles moving around in space like photons bouncing off the walls of the lab, or cosmic rays or background microwave radiation. Why that does not interact with the electron wave and break the interference? Does that mean the double slit experiment is done in complete darkness and shielded from all outside interaction?

If you wonder how to go from time flowing ahead to time flowing inverted, just take a look to the symbol "i" (aka imaginary unit) which appairs in some physic formulae.

What's is most astonishing is that time at athe quantic level flows in the opposite direction that it does at the macroscopic scale.

Great lecture! One question though: Might it not be an error to equate the thermodynamic arrow of time with the true arrow of time. As you note, entropy can decrease although it becomes fantastically unlikely as the system grows. Time, however, is not a statistical phenomenon like entropy: it cannot even in theory spontaneously go backward (to our knowledge). Furthermore, suppose the universe reaches its maximum entropy; as far as we know time will still move forward then. It's not like the diagrams you showed stopped progressing once maximum entropy was reached. Yes, perhaps it is practically impossible to distinguish the past from the future in a system of maximum entropy, but that doesn't mean that a past and a future don't exist in that system. Maybe we should simply consider entropy a natural phenomenon that occurs in temporal systems and the direction of entropy is only determined by the arrow of time of the temporal system. In other words, our existence does very much depend on the statistical phenomenon of entropy, but time itself (and the arrow of time) is what enables entropy to function in the first place.

I love you!

Nice video. Although I think what we lost was the actual equation! It's the equation of the day and he didn't unpack S = k log w and put it back together at the end. What did the k term represent, for example?

that means the universe after reaching highest entropy state,the tendency of object from moving order to disorder stops and ultimately leads to the end of the universe and it will feal like time is stopped.

Hi. Why some things that break you can sometime put together again (like when you break clay dough) but some you can't (like wood, or the wine glass etc)? About the glass, even if you apply force to each of the piece in a such an exact reversed way when it hit the floor, the glass won't become whole again right because you must melt glass for it to be seamlessly joined so the piece will remain in pieces? Since a child I have always wondered how come I can rip a piece of paper in two but I can't put it together again. They won't stick with each other. What happened at molecular level when I rear it? Why won't the molecule join back? I found out it's when the object is mallable or easily separated, that it can be easily joined again. Why?

This was a crackin' wee chat. Thoroughly enjoyed this. So good I watched it at 1x!

Please make more videos on time and Quantum consciousness

Sir you are sharpest example of your name.... Masha Allah....maybe Brian... I named brain....

will the reverse procces will occur in the time moving forward or time moving backward??????? please give answer

In the coin example, all heads or all tails are just particular configurations of the coins, with equal probability than the other ones. We just define "all heads" or "all tails" as "ordered". So it's time just a concept? The likelihood of the unbroken glass of wine is the same of any individual configuration of the broken one. The only difference is that an unbroken glass of wine can be easily drank whereas the others don't. So we define that the unbroken configuration is the ordered one.

Most startling take away from this video: someone under 80 years old actually has a landline phone. ;) But in all seriousness, these videos are very engaging and entertaining.

I don’t understand how entropy increasing leads to me remembering the past and not the future. When we deviate and there is a rare fluctuation that reduces S, does that mean time has moved backwards?