Leonard Susskind - Why Do We Search for Symmetry?

Lenard the concepts of symmetry and beauty are often used by physicists and it's it's wonderful to see terms that have artistic meaning but being used in a very rigorous way to search for ultimate reality day as fundamental as we can get how should we view those terms and and and what's been the current thinking about the search for symmetry because these are personal things I mean I'm a beauty symmetry elegance heretic I don't see the idea that nature is beautiful and the idea that we are searching for beauty is sort of mother apple pie things that we always say when we appear on television like this and stuff the fact of the matter is the universe is what it is it is neither beautiful nor not beautiful it is we who either who were imposed beauty or not beauty on it a butterfly is beautiful a slug is not beautiful this is our decision what we decide is beautiful and not beautiful that being said physics can be beautiful but it's we who impose the beauty on it we find beauty and mathematical arguments we find beauty and but what is beautiful and what it's not beautiful is entirely in the in the eye of the beholder general it's thought that if you're simple you're beautiful they're very complicated things going on never stick this in and stick that and then it's sort of under mainly yes the universe is very ungainly I have called it a Rube Goldberg machine it is very unkind lead there are too many parts the standard model has a hundred particles it has full of parameters there is nothing particularly elegant and simple about it there are elegant and simple parts pieces but the whole thing is I would call a monstrosity well that's why that drives people to look for something simpler that says therefore there must be something yes nice but keep in mind that that is something within the Hume being and not necessarily within nature now as far as symmetry goals if symmetry is meant in the way that physicists do mean symmetry and it has a very technical definition very technical definition it is now understood by most physicists to study the combination of quantum mechanics and gravity that there are no symmetries all symmetries of nature are approximate and therefore accidental so to call the world elegant because it's so symmetric is to my mind imposing our own values our own human values on a physical universe that doesn't give a damn what we call beautiful but in the past certainly physicists have used the search for simplicity as their form of beauty and and that has driven them to sosa narrative results and sometimes some very wrong ideas you know the Greeks thought there were four elements and only for the earth air water and fire there was a time in physics when they were also exactly than in recent times where there were exactly four elements the electron the proton the neutron and the photon that's all there were and people thought how marvelously simple well it didn't turn out that way as I said it remains to be seen how simple the laws of nature in their final form will be since we're so far from final laws of nature I don't think we can say whether they'll be simple and elegant in in the usual human sense looking at symmetry I'd like to understand more of if that it's it's approximate and therefore accidental it's fascinating concept because we mike knowledge in the past has been that physics looks for symmetries and then subtle ways of breaking the symmetry in order to in order to give the depth and and substance to it and so you need this concept of symmetry rotational or otherwise and then breaking the symmetry but now if it's if it's ax if it's if it's approximate an accidental what does it mean well it still may be useful the mathematics of symmetry even if symmetry is only approximate may still be very very useful in solving the mathematics of for example atoms or molecules and so forth atoms and molecules have approximate symmetries it is possible to use those symmetries to make mathematical statements about them where I would draw the line is saying that symmetry somehow represents the beauty and fundamental elegance of nature it may just be reflecting certain approximations approximate the relationships between numbers well these approximations because there are so many that seem to be important even if they are proximation x' whereas an individual one may be accidental collectively it doesn't seem accidental it's collectively the the large number of the symmetries wherever they form seem like it fits a pattern that this kind of structure is just a necessary way to build things okay so let me ask you how many symmetries can you name well I mean you know there are very complicated symmetries in the standard model of physics let me and they're all on they're all aprox and they're all Prime's I'm likely but it's all on the box but it's a way of listening the tables and the different family yeah alright so so for example the most important symmetries of the standard model offer example symmetries among the quarks yes as a matter of fact those symmetries are not even really approximately true they're simply there because the quarks have very very small masses and because they have such small matter some of them not all of them the up quark and the down quark have very small masses because their masses are so small they're almost equal because 0 is equal to 0 right so therefore there's a symmetry between the up quark and the down quark simply because they're both almost massless well when you look more carefully you find out that the down quark is about twice as heavy as the up quark but they both happen to be very light so because they're light you can ignore the mass because you can ignore the mass you can interchange them but they're not the symmetric they're not symmetric at all so the point is that the apparent symmetry is that which is there is an accident of numbers it's an accident of the fact that the up quark only weighs 5 MeV in the down quark 10 MeV and that for all practical purposes is almost zero it is not a fundamental law or a fundamental principle of physics that there should be a symmetry between the quarks is there a dispute in the field that people argue about the importance of symmetry no no no no they don't they are at least within the circles that I move in you can go on the internet you can find every possible opinion on every subject on every subject and the circles that I move in there is no debate about this we all understand that the symmetries that we talk about are approximate we all understand that they break down at some scale and that the accidents of numbers there are some things that we sometimes call symmetries they're called gauge symmetries these are not really symmetries they're not genuine symmetries in the usual sense there's something else we all agree that the things that we normally call symmetries relations where you can interchange things or rotate things or whatever like that they are all approximate there's no debate about it

Channel: Closer To Truth

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Keywords: closer to truth, deepest questions, fundamental questions about reality, ideas of existence, life's big questions, pbs science show, robert lawrence kuhn, search for purpose, stem education channel, ultimate reality of the universe, vital ideas, understanding the universe, Symmetry, understanding fundamental physics, Nobel laureate, symmetry and beauty, nature of physical laws, quantum mechanics questions, structure of the universe, why did humans evolve emotions, existence

Id: cVPNgHvSpCI

Length: 8min 27sec (507 seconds)

Published: Tue Feb 25 2020