The Stunning link between Entropy, time & information | Science behind Tenet

in all of physics entropy is one of the most unique yet enigmatic concepts and understandably so what does it actually mean and the common interpretation is that it is a measure of disorder in the universe and the second law of thermodynamics states that the entropy can never decrease in other words the universe is on an inexorable path to more and more disorder and it is this one-way property of entropy that some scientists contend is the reason time also flows one way and that's forward and if entropy is responsible for something like the flow of time itself then is it a fundamental property of nature or is there something deeper about entropy that really explains what's going on at the core of reality Scottish physicist James Clerk Maxwell came up with a thought experiment called Maxwell's demon that showed a mechanism where entropy of a closed system could be reversed it would violate the second law it was a paradox that no one could resolve for over a hundred years but when computer researchers at IBM finally did resolve this paradox they showed that entropy was related to something that could be even more fundamental and that is information how is this possible what is the link between entropy information and time the answer is coming up right now [Music] if you observe the rotation of the planets are on the Sun and then reverse the video there's nothing about the reversed motion that is unusual it would be permissible within the loss of physics similarly as far as is known all physical laws are time reversible the only laws of physics which appear to be time irreversible is the law of increasing entropy the second law of thermodynamics scrambling an egg shattering a hard drive putting sugar and coffee these are all actions such that if you saw them in Reverse you would immediately know that you're watching something absurd that could not happen but the second law of thermodynamics appears to be the only law that reversing these processes would violate running the movie backward would mean decreasing entropy the second law states that in an isolated system the entropy can never decrease but this doesn't tell us what entropy actually is so what is entropy the common definition is that entropy is a measure of the disorder of the system this is not quite precise to get a better understanding let's look at a simple visual example let's take a container with gas isolated in one side with a barrier if we remove the barrier we expect the gas to expand into the full volume of the container we have just increased the entropy of the gas why is there more disorder if the gas expands into a larger volume the reason is there is a greater volume and thus more places that individual gas molecules could be there are more ways to arrange the gas molecules in a larger volume than in a smaller volume this greater possible number of arrangements is really a better description of entropy this insight was made by Austrian physicist Ludwig Boltzmann as a definition of entropy that it is a way of counting the number of arrangements of atoms inside a system now what if we had a plunger on the right wall and push the gas back to half the volume of the container wouldn't this reduce the entropy back to what it was no because compressing the gas like this requires putting work into the system it would raise the temperature of the gas the gas would heat up and entropy would increase making up for any decrease in entropy because of the smaller volume why does entropy increase when the temperature increases again this has to do with an increase in the number of ways the motions of the molecules can be described an increase in temperature is due to an increase in motions or kinetic energy of the molecules in the gas as the molecules move faster the temperature increases and there are more ways to describe this motion than if the molecules were moving slower now the question is could the gas spontaneously arrange itself so that it fills only half the volume you might say well that can't happen because it would violate the second law by decreasing the entropy yes it would violate the second law but the truth is that there's nothing in the laws of physics that really prevents this from happening except that it is very very unlikely the possibility that all the multiple trillions of molecules in the gas could arrange themselves in one side of the container is about 1 to the power 150 billion trillion this number is so enormous that it is statistically impossible to give you an idea of the scale the total number of Planck volumes the smallest volume that could exist that would fit in the volume of the known universe is only 10 to the 183 so needless to say the second law is not going to be violated any time soon but it also tells you that the second law is not an absolute law it is a statistical law in other words it could be violated but it's just extremely unlikely but in 1867 Scottish physicist James Clerk Maxwell devised a thought experiment that showed that the second law could be violated and entropy could indeed decrease and this thought experiment seemed perfectly plausible to scientists and they could not figure out why it was wrong for over a hundred years British physicist Lord Kelvin later labeled this Maxwell's demon imagine a chamber with a divider in the centre if we start out with the gas in one chamber this gas will distribute itself evenly between the two chambers now what if we put a door between the two chambers that is controlled by a little demon the door is frictionless so adds no heat or energy to the enclosed system the demon controls the door such that he only lets the molecules travel in one direction when a molecule comes near the door from the right he opens the door to let the molecule travel to the left chamber he doesn't let any of the molecules from the left chamber travel over to the right chamber you can imagine that over time this demon makes it so that the gas is collected on the left chamber such that no molecules remain in the right chamber no work was added and the temperature remained the same so the entropy decreased now this clearly seems to violate the second law you might say well it's a thought experiment with an imaginary demon it can't really be done but you have to remember this was thought of at a time when the concept of nano robots and micro processors didn't exist it's conceivable that in the near future we could build a computer-controlled device that could be the mechanical equivalent of the demon so scientists could not disprove this idea behind this thought experiment for over a hundred years the solution finally came in 1982 by two scientists at of all places IBM research rolf landau and charles bennett they boiled the idea of the demon down to a fundamental idea behind entropy and that is information they showed that in order for the demon to reduce the entropy he has to gather information about the movement of various molecules to determine when to open and close the door he's building a memory record the demon is increasing the amount of information in the system because he is part of the system this increase in information is an increase in entropy they showed that the decrease in entropy due to the volume decrease is exactly counter balanced by an increase in information in the demon's brain the second law is not violated you might say well all I have to do is erase the memory of the demon if this was a computer hard drive we can just reformat the hard drive and there now the hard drive has low entropy again aha but Landauer and Bennett show that erasing information is not free erasing information produces heat it increases entropy so you can't gather information in the demon and then erase it to reduce the overall entropy the increase in entropy from the heat of the sure he's perfectly offset by the decrease in information in the hard drive now this is not very much heat only about three billions of a trillionth of a joule per bit that's erased but this also gives us a clue about the true nature of entropy and that nature is that it is really a measure of the information required to express the state of a system a system with higher entropy requires more information to describe its microstates when you increase temperature by adding energy for example there are more ways that this energy can be shared with the gas molecules this requires more information to figure out if we increase the volume the molecules have more places where they can be so this requires more information to describe the microstates of the gas this information requirement is a better definition of entropy than simply disorder now how does time and turn to the picture how is time related to entropy and information since all the laws of physics we know appear to be symmetrical with respect to time it doesn't seem to be any reason time should be asymmetrical except through the idea of entropy entropy is asymmetrical it flows only in one direction higher the feature of the universe that changes with time is entropy now this inspired British scientist Arthur Eddington to postulate that it is the increase in entropy that's responsible for the flow of time but this time go forward because entropy increases this is not well understood it's not a good theory because the prediction it would make is that time should go backward when entropy decreases there are pockets of decreasing entropy all over the place the inside of your refrigerator is a place where entropy is decreasing your food is getting colder but time doesn't flow backward inside your refrigerator similarly the earth at night experiences decreasing entropy but time does not flow backward at night so what actually causes time to flow forward to answer that let's look at why entropy increases entropy increases not because the fundamental laws of physics says it does but because there are simply more ways that microstates can arrange themselves in the future than in the past for example there are more ways to arrange the checker pieces on a checker board then when they are neatly arranged at the start of the game we are much more likely to be in a state of higher entropy than lower entropy as time passes but since entropy is fundamentally a statistical law based on higher and higher amount of information needed to describe microstates then could the flow of time also be a statistical phenomenon that is time is much more likely to flow forward than to flow backward if so this would leave open the idea that time flowing backward is not forbidden but just statistically impossible if entropy increases over time that means that entropy must have been at its lowest possible state at the start of the universe at the Big Bang this is sometimes referred to as the past hypothesis and this low entropy start is thought to be the primary reason why time flows forward but why was entropy so low at the start why did the universe start in a very ordered state given all the energy and matter in the universe and all the states that it could have been in why did it start in this way in this very small subset of all the different configurations that it could have been it no one really knows the final answer but there are some leading ideas maybe there's a fundamental reason but we haven't discovered yet and we're trying to explain something that is part of our ignorant maybe it's just a fact it's a property of the universe like the fundamental constants another idea is from physicists like Alan Guth and Sean Carroll if there's no upper limit to entropy that is maybe entropy is infinite then no matter where the universe started it would have been in the lowest entropy state it has nowhere else to go except to a higher entropy state if time flows forward as entropy becomes higher then we are a result of the second law we are a consequence of the increasing entropy of the universe if the universe was in thermal equilibrium we would not exist the reason we have causality evolution biological processes thoughts memories and even consciousness is the second law Alan Guth points out that if information was not increasing in brain we would not have memories or consciousness this links entropy to consciousness itself and entropy will continue to increase for billions and probably trillions upon trillions of years when all the galaxies have spread apart all the stars have been burned out dark energy will have ripped apart all matter including all molecules atoms and even subatomic particles at some point we will be in thermal equilibrium at least locally where we are in the universe and at this point entropy may cease its inexorable forward march and all will become quiet but space will not go away and the laws of physics probably won't either what will remain is the vacuum energy quantum fluctuations in the fabric of space-time given enough time there will be enough random energy fluctuations within the vast space of the universe that an atom formed spontaneously a molecule forms spontaneously interstellar gases could form stars and galaxies could form the bigger the thing the longer you have to wait but if you have an eternity to wait it will happen at some point and statistics predict that if you wait long enough around 10 to the 10 to the 10 to 100 20 years defending universe could form spontaneously guys in this short video I've only given you a sample of how entropy works but if you want to get a deeper understanding of this and other scientific subjects then your best bet is to head on over to brilliant today's sponsor brilliant is a problem-solving website an app that allows you to dive into the world of science and math often through the eyes of a pioneering scientist or mathematician they offer a variety of courses from scientific thinking to quantitative finance there's no better way to learn than by doing it's the best way to train your brain you can take your learning to the next level by solving problems and working on puzzles in real time and don't worry if you get stuck on a problem or puzzle they give you hints the goal is always to learn and grow not to feel silly I was really impressed by how well thought-out and curated the content is they have a special offer for our vinash viewers right now head on over to brilliant dot org /rv - to sign up for free not only will you get a free trial but the first 200 visitors will 20% off your subscription check it out I think you'll be impressed I'd like to thank my supporters on patreon for their generous support if you like this video then please feel free to share it with your friends I will see you in the next video my friend [Music] [Music]

Channel: Arvin Ash

Views: 404,540

Keywords: entropy, what is entropy, second law of thermodynamics, entropy thermodynamics, how is entropy measured, how is entropy affected by temperature, how is entropy related to the second law of thermodynamics, entropy and time, entropy and information, entropy and life, entropy and temperature, entropy and consciousness, entropy and conservation of information, entropy definition, Maxwells demon, maxwells demon information theory, science of tenet, tenet theory, tenet time reversal

Id: T6CxT4AESCQ

Length: 15min 20sec (920 seconds)

Published: Sat Jun 27 2020

Reddit Comments

[u/CivilServantBot]

Welcome to /r/Futurology! To maintain a healthy, vibrant community, comments will be removed if they are disrespectful, off-topic, or spread misinformation (rules). While thousands of people comment daily and follow the rules, mods do remove a few hundred comments per day. Replies to this announcement are auto-removed.

[u/aught-o-mat]

This was fascinating and informative - I can feel the entropy increasing in my brain as my understanding of the universe becomes more ordered...