One thing I absolutely love about Noether's theorem (you know, besides the whole "she literally figured out _why_ conservations occur") is the fact that symmetry in position implies momentum conservation, and symmetry in time implies energy conservation. Meaning that the relationship between space and momentum is very similar to the relationship between time and energy - something that Einstein *_also_* figured out through a _completely_ different route. And the fact that 2 different people could arrive at such a fundamental truth about the universe through such different means is mindblowing. Oh, one more thing: Angular momentum is conserved because of rotational symmetry - yet elliptical planetary orbits also have a conserved angular momentum. How exactly do the two fit in? Does it mean "same energy even though the orbit shifted slightly"?
@michaelsommers23566 жыл бұрын
_"Angular momentum is conserved because of rotational symmetry - yet elliptical planetary orbits also have a conserved angular momentum. How exactly do the two fit in? Does it mean "same energy even though the orbit shifted slightly"?"_ No, it means "same angular momentum". The position changes, and the velocity changes, but their (cross) product stays the same. This is true with either circular or elliptical orbits (or with no orbit at all). Remember that position and velocity are vectors, with both magnitude (distance and speed) and direction. In circular orbits, the magnitudes are constant, and only the directions change; in elliptical orbits both magnitudes and directions change. But in either case, the cross product is constant.
@Rastafa4695 жыл бұрын
I think you can also see the elliptical orbit as a combination of rotation and translation (it pops right out if you use polar coordinates) so you could think of it as a combination of rotational symmetry (conservation of angular momentum) and translational symmetry (conservation of momentum). I'm not 100% sure about this it's just an idea that popped into my head and l would love for someone with more knowledge about this topic to correct or approve this idea
@aartvb94434 жыл бұрын
In the video she talks mainly about potential energy. In the case of an elliptical orbit the potential energy is not concerved, but kinetic + potential energy is conserved, so the TOTAL energy of the system is still conserved. If the planet is closer to the center the potential energy is lower but kinetic energy is higher, and vice versa. So now indeed your question arises what the symmetry is - it's not a circle! What you need to remember here is that not the shape of the path has to be symmetric, but 'the way the planet acts' (in Lagrangian physics terms: the action). If the planet would be rotated to another point, the path would also be rotated with it, so the planet would still act the same, but it is rotated a bit, including the path it takes. So the symmetry doesn't have to mean it takes the exact path as before, but that it follows the same path, with that path just being rotated over the same angle as the object was. Does that help?
@giljorge74792 жыл бұрын
Newton also sort of figured it out. F*t= change in momentum F*d= energy
@nuclearnyanboi Жыл бұрын
@@michaelsommers2356 how do I bookmark this comment?
@LockenJohny1018 жыл бұрын
Its all fun and games, until your exam is tomorow....
@RamkrishanYT7 жыл бұрын
LockenJohny101 lol, my exam is tomorrow and this is not even in my course
@Walsh25717 жыл бұрын
same
@CandidDate7 жыл бұрын
God said "let there be a bang" and there was a bang. A big one. And the only one we have proof of. I argue that if even one atom were misplaced, nothing would have happened.
@degautaborg7 жыл бұрын
There is no proof whatsoever of the ridiculosly naîve big bang. The universe is moving alright, but not outward since there is nothing, no spatial dimensions "outside", it continuously moves whitin itself, known as the Donut Theory. From this movement of the spatial dimensions themselves emanates the red shift.
@onehitpick97587 жыл бұрын
Even the big bangers are now saying there was no "bang". Nowadays, it's just a simple expansion of of space-time, optionally with inflation and even more optionally with effervescence.
@PseudoAccurate8 жыл бұрын
I love your videos. I always hear a smile in your voice.
@RSolimov8 жыл бұрын
Yea, you can kinda tell she can barely contain herself. so kewl.
@fukpoeslaw36134 жыл бұрын
@@RSolimov 'kewl'?
@SteveGouldinSpain4 жыл бұрын
@@fukpoeslaw3613 cool but with a cooler spelling.
@fukpoeslaw36134 жыл бұрын
@@SteveGouldinSpain tewk me half a year, but finally I know!
@summernights15554 жыл бұрын
@@fukpoeslaw3613 kewl. 😹
@cheesywiz94436 жыл бұрын
"writes most beautiful bit of physics in spare time 100% not jealous" xDD
@devon93743 жыл бұрын
power of math, so beautiful
@RalphDratman8 жыл бұрын
This is the best introductory discussion of Noether's Theorem I have seen. Thank you for your excellent work! Here is a suggestion. It seems to me that your examples of systems whose energy has not changed after a particular transformation might be easier to understand for viewers (for me anyway) if you considered a small, continuous change rather than a large jump change. A system whose energy did not change after a jump (for example, an instantaneous rotation through 60 degrees) might turn out to have periodic energy dependence with period, in this example, 30 or 60 degrees. While a jump change is not ruled out, I do not think a discontinuous change would best exemplify the type of conservation law you are aiming to illustrate in this video. The real-world conservation laws that I am aware of (in classical physics with or without relativity) are all based on continuous quantities. You don't have to call it an infinitesimal change. You might just say the change is gradual, or something like that. P.S. I might be wrong about this. It was just a thought.
@LookingGlassUniverse8 жыл бұрын
No I love the suggestion. If I could go back, that's a change I'd want to make. Hopefully I will give Noether's theorem another shot in a while- I wasn't too happy with that one. I really appriciate the suggestions for improving it!
@RalphDratman8 жыл бұрын
+Jack McMillan So each symmetry to be characterized requires its own Lie algebra to be set up based on the relevant degrees of freedom in the neighborhood of a given point in the problem space -- something like that?
@Legionary428 жыл бұрын
Hi there. I've got to ask... " So...a symmetry is when you change a system and some number computed from the initial condition doesn't change. And, A conservation law says that when a system changes, there's a number that characterized the system in the first instance that's the same in the second instance. This theorem seems...tautological... " I first posted this to the original video (just now), but I realize that's probably not going to get a good answer. Can you help me sort my confusion? Edit...perhaps I am under-appreciating the development of ideas that it takes to come to such conclusions...particularly when I am now speaking from the shoulders of all the others who had to toil so!
@RalphDratman8 жыл бұрын
I am not qualified to assist you with that. Sorry. Perhaps the following might be of help: physics.stackexchange.com/questions/4959/can-noethers-theorem-be-understood-intuitively
@MrAkashvj967 жыл бұрын
Hi there Legionary42. Maybe I can help you a little bit. Symmetry means something very specific in physics. Symmetry refers to a certain transformation of a system's dynamical information (which consists of positions, velocities and perhaps even time) which leaves the Lagrangian unchanged. These transformations are physically interpreted as a change of coordinates. Note something very VERY important though. The only kinds of symmetries Emmy Noether discusses in her groundbreaking paper are so called continuous symmetries, where each symmetry transformation can be built up by a large number of tiny infinitesimal symmetry transformations, such (to be more precise, the group of symmetries forms a Lie group). An example is rotational symmetries. A conservation law refers to a physical scalar quantity that doesn't change with time. Notice, a priori these 2 concepts seem to have no no connection whatsoever but Noether's theorem shows otherwise. There is no intuitive argument I can think of to explain this relationship and in fact I'm not even sure there exists one. A Lie group refers to something very very specific (namely a differentiable manifold, equipped with a group operation) & the fact that every "continuous symmetry" (i.e. what we intuitively think of as being a continuous symmetry operation) can be given enough structure for it to form a Lie Group is a highly unintuitive fact. Symmetry, the way we intuitively think of it, is just a map on the phase space which leaves the Lagrangian unchanged. This is not enough to derive a conservation law. So although we have intuitive notions of what we mean by symmetry and conservation laws, those intuitive ideas are not enough to establish Noether's theorem. We have to introduce a lot more structure to our model to establish the connection. Unfortunately this breaks down the intuition. Moreover I think I should point out that although in classical mechanics, you get conservation laws only from continuous symmetries, In Quantum Field Theory, even discrete symmetries have a conservation law. For instance think of the harmonic oscillator modelled by the potential (1/2) kx^2. You can check that the Lagrangian doesn't change if you swap x for (-x). There is no conservation law for classical mechanics for such a symmetry. There is one in QFT.
@kingmunch72525 жыл бұрын
After 2 or 3 years later and also constantly learning new things, i finally feel like I understand what’s being said said in this video. Truly feels amazing finally able to grasp it. Thank you 😊
@makarlock4 жыл бұрын
The coolest thing about this video is that you explained the intuition, motivation, and significance of Noether's theorem without invoking the Lagrangian at all. I watched this video when it came out (in high school for me) and thought it was an amazing concept. I'm commenting now after taking classical dynamics for my physics degree, and this intuition was really useful for understanding the lagrangian, even though usually, its the other way around. Thanks again! Love the new "self-teaching" physics video too btw!
@ScienceAsylum9 жыл бұрын
I'm so excited you got around to this video. Were you just using conservation of energy as an intuitive reference? Because I think (traditionally in Noether's theorem) it's treated as a complete independent thing.
@LookingGlassUniverse9 жыл бұрын
+The Science Asylum Traditionally its symmetry of the lagrangian, but there's an equivalent Hamiltonian formulation that I got excited about. Way more intuitive to me!
@ScienceAsylum9 жыл бұрын
Looking Glass Universe I think I should sit down with the math then. Lagrangians are weird. Anyway, I'm glad you got excited about it. It showed :-)
@holomorphicguy5 жыл бұрын
:D
@howardOKC5 жыл бұрын
Hi crazies!
@badmintongo48323 жыл бұрын
@@LookingGlassUniverse Nah, AdS/CFT is way more beautiful
@asymptoticspatula7 жыл бұрын
Thank you for this great explanation of Noether's Theorem. I've been reading a biography of Emmy Noether, and I have a physics background, but I didn't really understand her work at all. Now I understand it a bit more. Thank you. I subscribed to your channel and will definitely be checking out some more of your work. Thanks again! P.S. Emmy Noether is really a tragically unknown figure in physics. I hope more people learn about her. That's why I decided to read up on her, because she's one of the most influential women in math/science (one of the most influential of men and women, in fact) but she is still totally unknown to most. It's a shame. But your video surely has reached new audiences and for that you deserve praise.
@niklasb26649 жыл бұрын
As a theoretical physicist, I'm very happy that this video exists. It certainly is the most beautiful theorem in physics and i wish i could explain it that well in simple terms.
@tok84254 жыл бұрын
I love how happy your voice is when you are talking about this subject :)
@kevinocta97168 жыл бұрын
Wow, this is AWESOME! I finally UNDERSTAND why there are these random 'laws.' And on your roller coaster example, I'VE HAD THE EXACT SAME THOUGHT!!! Yeah, I solved the problem, but I'm just using some law, so to really explain anything I must explain where the law comes from! This is so cool! Great video. I cannot express how long I've been thinking this and how annoyed I've been with 'It's just the law' (I really feel like this should have been explained to me years ago, maybe in high school or something) But, it's never to late to learn, so thanks!
@julsius8 жыл бұрын
yes this was definately not in HSC AUstralian higher physics 2004 though clearly shouldve been. I think its because symmetry has buddhist connotations, and Australia has a Christian hangover.
@j.c.79757 жыл бұрын
I feel 100% the same! :)
@PatchyE6 жыл бұрын
To be honest even if you don't know about Noether's theorem, conservation laws are just mathematical derivations from basic Dynamics (Newton's laws, Schrodinger Equation, etc.) They are not "random" or artificial, just magic numbers given rise to by mathematics. Of course if you are still not satisfied and want to go deeper you can always fall back to the Principle of Least Action.
@selforganisation6 жыл бұрын
I agree, I also find it extremely beautiful that conversation rules are connected with symmetries of time and space. When I've read about Emma Noether's theorem, it blew my mind!
@DaytakTV7 жыл бұрын
I am currently a physics major in college. I absolutely love your work! It is so refreshing and clarifying yet introduces fascinating questions to ponder :)
@12tone9 жыл бұрын
Really interesting. I had encountered symmetries and conservation laws before, of course, but it had never occurred to me that they'd be related like this. It makes sense, and I think the rotational example is probably the best one in order to understand it. If an object behaves the same no matter where in its orbit it is, then logically it'll always come back to where it started, and angular momentum is conserved. It had never occurred to me though. Thanks for explaining it! On the second question, I don't really understand supersymmetry beyond that my physicist brother thinks it's hilarious that we haven't found any supersymmetric particles yet. I have some grasp of what supersymmetry is for, but not much at all about what it is. Looking it up, it seems to be about symmetry between bosons and fermions. But would energy be equivalent in that? If these supersymmetric particles exist they'd have to be of higher mass than particle accelerators can produce, so the boson version of a down quark, for instance, would have to have a much higher mass than it. And if it has a higher mass it has more energy, so then how could it be symmetric? Researching this has left me more confused than when I started... Maybe I'll ask my brother when he wakes up. On examples of symmetries, my music training is kicking in and I keep thinking of things like diminished seventh chords, augmented triads, and whole-tone or chromatic scales. those are translationally symmetric, at least if you don't count octave. I have no idea what, physically, is conserved there though. On the diminished seventh chords at least, harmonic function is conserved, which is actually an incredibly cool feature of those. (Seriously, diminished seventh modulations are my all-time favorite piece of music theory.) But that's not a physical property, it's an observational effect. If you're talking physically, you do go up in pitch as you go, and I believe higher frequency is higher energy, so not really symmetric. If you rotate it around so you're actually playing the same register of notes though I suppose you're conserving something. I don't know if that's valid though, since it requires accepting the octave as a fundamental unit. I may be cheating, but if I am I still don't have any useful answers so at least I'm not a very good cheater.
@razorborne9 жыл бұрын
I've started commenting on videos with my 12tone account instead of my personal account (this one) to keep them a little more separate. I don't know if you recognize me anyway, but I've been watching and commenting for a while and I didn't want you to think I'd just disappeared!
@salim4449 жыл бұрын
+razorborne bro that some really nice text. :)
@12tone9 жыл бұрын
saleem khatib Thanks!
@erictao83962 жыл бұрын
This is an interesting question (I know I'm 6 years late to respond)! I don't have a full answer, but I will say the behavior of pitch classes in music works a lot like a cyclic group in abstract algebra! If you accept the octave as a fundamental unit, you can "quotient" out the octave and just focus on pitch classes, which is similar to if you took all the integers and divided them by 12, concentrating only on the remainder after the quotient. Physically, I think you could interpret this symmetry as a dilational symmetry in frequency (since moving everything a major third up for example is equivalent to multiplying the frequency by the third root of two). However, I can't think of a way you could apply Noether's theorem to this situation because Noether's theorem requires a *continuous* symmetry. For example, if you move forwards 10 seconds, 2 seconds, 0.01 seconds, 0.00001 seconds, etc., it doesn't matter: energy is still conserved in Newtonian mechanics. However, with the chords that you mention, the symmetry is *discrete* in that it only works for specific values of movement. If you move an augmented triad up a major third or an augmented fifth, it stays invariant, but if you move it up a whole tone, a semitone, a quarter-tone, etc., the symmetry breaks, meaning the conditions of Noether's theorem aren't met. Also, I'm not sure if there's an analogous principle of least action (which Noether's theorem depends on) in this situation, but I'm sure there's some way to draw a physical interpretation of this, maybe in studying the frequency spectrum of sound decay over time? This is just wild hypothesizing since it's 2 AM, but it would be interesting to see if there's a spectral equivalent of Noether's theorem since all the examples given (translation, rotation, time translation) are symmetries in space-time while your example is a movement in frequency space. I suspect that if you could formulate an appropriate Lagrangian, there might be some way to apply Noether's theorem, although it would probably have nothing to do with music. It's still an interesting thought experiment though! For an elaboration on the abstract algebra though, check out this cool stack exchange post about Messiaen's modes of limited transposition and group theory :) math.stackexchange.com/questions/4045800/music-and-maths-modes-of-limited-transposition Also, I love your video on diminished seventh modulations
@LacXav4 жыл бұрын
4:20 "I used to not like using conservation laws because they can make it seem too easy." Love it, I feel exactly the same.
@arctic_hazeАй бұрын
This is because physics is taught roughly as it has been discovered. We start with the Newton's Laws of Motion not noticing that they come from the conservation laws, which are much more fundamental. If I would ever be forced to teach Physics 101, I would start with conservation laws.
@adamthornton78807 жыл бұрын
Thank you, ma'am. I watched this at least 5 times now (I'll probably watch it again, when my head stops spinning), and I feel like I understand much more than I did before, but also like I've only scratched the surface of the ideas presented here.
@TheHow2win7 жыл бұрын
Thank you! I have read about Noether's theorem and I know Einstein really like her work. I think I have a good understandings of the basics. Well done.
@AbhishekKumar-xf9td2 жыл бұрын
Never heard it before,my friend suggested me to look for noether theorem ,I searched it and I'm glad I found it 💙💙💙. You explained it so well ,thank you 😇🙏
@tarreqmaulana94949 ай бұрын
I haven't heard any of this before, and now it's another theorem for me to explore! Thanks you for the great explanation.
@YossiSirote7 жыл бұрын
I knew that therr was something in Physics that had to do with symmetry implying a something, but I was not sure. I went to KZbin to find a video explaining it. And yours was bu far the best. Thank you. I have subscribed to your channel, and I am working my way threw all of your videos now. I love them. Keep up the great work!
@monkey_gamer_0017 жыл бұрын
Starting third year astrophysics. Noether's Theorem came up. Wanted it explained concisely. This is what I was looking for!
@dubhuiitisro Жыл бұрын
This video is extremely descriptive and very easy and understandable from layman point of view. Really good work
@michaelanderson48493 жыл бұрын
Emmy was such a BOSS! It pisses me off to no end that she wasn't recognized at the time for what she achieved.
@QDWhite4 жыл бұрын
I've seen a lot of videos and read a lot of books explaining Noether's theorem. Considering the balance between completeness and simplicity, this video is by far the best.
@boom20558 жыл бұрын
This is a really good video demonstrating physical laws. For me, when trying to look this theorem up, I found wikipedia no help, being dropped into an infinite cycle of looking up unfamiliar terms. This video really showed the essence.
@timh.68727 жыл бұрын
I've seen a few other of your videos, but this one earned the sub. Math and physics with a solid backing in both? Absolutely. As a CS/Math person (who spends most of his time where the two look like the ssme thing), I would almost venture to say that I'd prefer a mechanics built from conservation laws implied by symmetries, because symmetries are the building blocks of the algebra we use to solve the problems in the first place. I think I'll spend the afternoon poking at Noether's theorem with respect to multivectors and geometric algebra. That angular momentum conservation due to rotational symmetry is begging to be described in terms of bivectors, heck, kepler's laws probably drop out if the orbit's spinor varies in time...
@antipoti3 жыл бұрын
Her voice is so soothing and lovely, with a hint of a smile in it. It tingles my brain.
@hp1273 жыл бұрын
In 2020, your videos are great presentations, drawings and humor in addition to the science. Thanks
@carlb.95189 жыл бұрын
This reminds me of the uncertainty principle, in that everything comes in pairs that multiply to give angular momentum. Momentum * Distance = Angular momentum * Angle (dimensionless in radians) = Energy * Time
@WackyAmoebatrons4 жыл бұрын
More precisely, the pairs multiply to give "action" (which only happens to have the same unit as angular momentum). Planck's constant is a tiny quantum of action.
@sriramalka9 жыл бұрын
Beautiful presentation of a beautiful theorem. Thank you!
@Relative09 жыл бұрын
Was just about to apply this idea of conservation and symmetries to some logical systems that I have been examining; but then you asked it in the homework. But say we take (in first order logic) the logical expression X Y. Now we can see by the truth table that we could switch X and Y (X on the right and Y on the left) and we get the same truth table. However, if we tried that with X => Y, this is not equal to Y => X (If X not equal to Y of course). So an interesting question might be, what is conserved? Possibly Logic? Well I am going to look in to it, but before I do, I must thank you for bringing these ideas to my attention - your videos are amazing, and while I am sure you hear that all the time, I suppose it doesn't hurt to add to the pile of compliments ;).
@lanevotapka40128 жыл бұрын
Thanks for this video! I've heard of this before but I just noticed an interesting thing watching this. I realize that in a lot of formulas, you see position and moment together, and energy and time together. For instance, I've seen that the Heisenberg uncertainty principle can be expressed in terms of position and momentum, but can also be expressed in terms of time and energy. We also know that the momentum of a light wave is related to its wavenumber (cycles per distance), and the energy of a light wave is related to its frequency (cycles per time). Perhaps this is what you mean when you say that more appears in quantum mechanics. Very cool!
@lucystarlight88874 жыл бұрын
I don't know much about physics but I have tons of respect for the people long ago who made revelations that still impact us today
@zennizura6 жыл бұрын
Thank you for helping me understand what the theorems about. Although I barely understand what you were saying at all. I strangely get what you are trying to say. Then again, I am just a person who is trying to do a book report about Emmy Noether. Not helpful that I don't even take a physics class. But, then again, thank you very much!
@simonhanson59902 ай бұрын
excellent discussion, i really appreciate the clarity of your explanations, thank you
@Hecatonicosachoron9 жыл бұрын
Here's a little derivation which I used to work out several examples, for the one-dimensional case. Let G be a generator satisfying the Leibniz rule, i.e. G[fg] = fG[g] + gG[f] For the 1-d case, if G is a first-order differential operator is can be written as G = v d/dq where v is some suitably integrable function of q (note d/dq is supposed to be a partial derivative wrt. q, but for the 1-d case that does not matter much anyway). Define w as the antiderivative wrt q of the reciprocal of v: dw/dq = 1/v and let W be the inverse function of w. Given these definitions, and k being some parameter, it can be shown that the operation exp[kG]{f(q)} = exp[ k v df/dq ] can be evaluated: exp[kG]{f(q)} = f(W( w(q) + k )) Particular cases include 1) v(q) = 1; G = d/dq; exp[kG]{f(q)} = f(q+k) i.e. the derivative wrt is the generator of translations wrt q. 2) v(q) = q ; exp[kG]{f(q)} = f(q exp[k]) i.e. q d/dq is the generator of dilations other interesting cases: 3) v(q) = q^(1-a) ; exp[kG]{f(q)} = f( (q^a + ak)^(1/a)) 4) v(q) = sech(q) ; exp[kG]{f(q)} = f(arsinh( sinh(q) + k)) one of my favourites, which is an interesting transformation, asymptotically mapping f(q) to itself for sufficiently large values of q, but skilngully avoids the origin for values of sinh(q) comparable to k. v = sqrt(q^2 - 1) is also interesting. I guess similar versions with the cisrcular functions may also be interesting. Note, I was copying my notes while typing that so I hope the derivation is correct and I didn't copy the mistaken version (yes, there were a few of those...)
@THPV9 жыл бұрын
Great video, I loved it. This channel is really one of the best I know on KZbin and you do a great job explaining science phenomena. Thank you
@vwcanter6 жыл бұрын
Thanks for putting this up. I believe there is a more basic version of this that predates Noether's theorem by many centuries, because you can easily make an argument by contradiction, where you suppose that a certain quantity is _not_ conserved, under a certain transformation, and then it follows that by measuring that quantity, you could tell where you are on the particular dimension on which the quantity varies. If there is no way for you to tell where you are on that dimension, by measuring that quantity, that means that the quantity is conserved under transformations on that dimension. If you could tell, by measuring a certain quantity, that means there has to be at least some type of difference between one place and another place on that dimension, in other words, an asymmetry. For example, the temperature outside is not conserved, from one day to the next, and consequently, you can look at a thermometer for 30 days in a row, and (in case you had no other information) you could ascertain the position of the earth in its solar orbit. That tells you that the position of the earth in the summer can not be exactly the same as in winter, and in fact, the earth's solar orbit does not have rotational symmetry, at all, and in fact, the weather is the first way that people knew that (and the positions of the stars, of course). If you applied the same reasoning to linear momentum, which is conserved, on the other hand, you could ask, if you rode a train from one town to another town, whether you could tell how far you had gone by measuring how fast the train was moving. If you could tell where you were by how fast it went, that would mean that our path did not have a symmetry under a linear translation, precisely because you could tell the difference between one place and the next. (I am implying an idealized train, but you see what I mean.) If it were possible on such a train to observe, for example, "We're going faster, so we must be almost there," that would mean that there was a difference between your momentum in the first town and your momentum in the second town, in other words, an asymmetry under linear translation. I believe what Noether's theorem does is merely formalize and generalize this fact, which people had already been applying for many centuries.
@dawnbern2917 Жыл бұрын
Thank you so much for your explanation, I heard about this from Jack Kruse, a renowned brain surgeon who is very interested in quantum biology. Best to you.
@connemignonne8 жыл бұрын
Mindblow at 7:57 when I realise that these line up perfectly with the quantum operators on the wave function! We work out the momentum of a particle by the rate of change of the wave function with respect to position (or translation!) Similarly, we work out the energy using the rate of change of the wave function with respect to time. I can only then imagine that the spin of a particle is calculated using the rate of change of the wave function with respect to its rotation in some sense? Also, please return to your videos! I am only discovering them now and seeing that you seem to be on some quite long hiatus. :-( A clearer explanation of what I was just saying: kzbin.info/www/bejne/govMlmWHeJp9mMU
@aartvb94434 жыл бұрын
Wow that's so cool! I didn't realize that yet.
@plasmaballin6 жыл бұрын
This clarified a lot about Noether's theorem - specifically what exactly counts as a symmetry. I still have two questions if anyone knows the answers: 1. I noticed that, in all three examples, the dimensions of the conserved quantity are ML^2/T divided by the dimensions of the symmetric property. I could easily see there being a mathematical reason for this, since the theorem is about quantities being conserved over time in systems where energy is symmetric, and the units of energy*time are ML^2/T, but I could also see it just being a coincidence. Which is it? 2. If we slide an object across the ground, it will lose momentum due to friction, but the object's energy wouldn't change if it was moved to a different part of the ground. Why doesn't this violate Noether's theorem?
@mcneelyng5 жыл бұрын
Please start making videos again. These are great
@TheAllroth9 жыл бұрын
A minor point but at around 0:34 you say that "Symmetries imply conservations" but what you have in the image is an equvalence and during the rest of the video it sounds like you're talking about an equivalence rather than an implication. Other than that this was a very good video for introducing the concept of symmetries and the relation to conservations, of which I didn't know; but you learn something new every day and I say thank you for that! :)
@Holobrine6 жыл бұрын
I think you can take it a step further and say that symmetries can also imply potential energy. For example, an object going up will have the same speed when it falls back down to the same height; therefore gravitational potential energy exists. Or an object moving at a spring will have the same speed when it gets repelled back to the same distance, thus elastic potential energy exists. I’m not sure what to call that symmetry though.
@camilodominguez46784 жыл бұрын
" The most profound and far-reaching idea" is quite ambitious even thoug Thank you for this explanation, such a brilliant carrier that Emmy had by the way.
@RoulDukeGonzo7 жыл бұрын
I heard about this from Feynman's lecture on symmetry. "Watch out!” - lol. Best physics punchline ever?
@caioreis3508 жыл бұрын
Halliday once said that we use physics to make it more easier to understand the nature around us. And to help us, we use tools like symmetries. I aways agreed with him on that, and now that i watched your video i can totally see where and how those symmetries help us. Also, i think we humans use symmetries because of our power to recognize patterns. Thanks very much for adding this
@whovillewho97648 жыл бұрын
I always watch your vids while doing my stats homework. Keeps me motivated!
@buttegowda2 жыл бұрын
Thanks a lot for wonderful and simple way the concepts are explained. The next question would 1. What there are certain symmetries ? 2. How is co ordinate translation related to this .
@schmetterling44772 жыл бұрын
These symmetries exist because the world is geometric and relative. Why is the world geometric? We don't know. It is relative because it is mostly empty at this time. During the early phases of the big bang the density would have been so high that relativity would have only be relevant at really high energies and short distances. All the low energy creatures would have been living in a thick soup of matter and radiation. The universe would have looked more like the bottom of the ocean than space, the final frontier. The important thing to know is that even a geometric universe is not enough. Geometry is a very subtle interplay between fully symmetric and fully anti-symmetric geometric objects. In particular, a fully anti-symmetric vector product (cross product) only exists in three and seven dimensions. It is this cross-product that enables stable planetary orbits (and only in three dimensions). Heat flow on dimensions other than three will, if I am not mistaken, also lead to near insurmountable stability problems with systems like star-interiors and it will severely limit the thermodynamics of living organisms in fewer or more than three dimensions. So basically everything that we see around us depends on this three dimensional geometric background. Don't get me wrong, there might very well be other interesting solutions for highly organized universes in different dimensional spaces, but they won't look anything like this one. And so when you go down the rabbit hole of these kinds of insights in physics, then you will discover that almost everything that we know about nature depends more of less on the existence of this three dimensional physical vacuum in which relativity is the dominant symmetry. The reasoning just gets ever more complicated. What I told you above can be discovered with little more than high school math. The consequences for quantum field theory, on the other hand, require much more demanding mathematical tools to unearth and we are far from done with that work.
@MacksP0w3r7 жыл бұрын
The best way I can think of explaining symmetry ts than if in happens, and you observe it from different locations, angles and time, you will always observe the same event after accounting for the differences in location angle and time. In other words the laws of physics do not change based on when and where and observer is witnessing and event. Due to Noether's theorem, this means that we can only disprove the three conservation laws, if we disprove the very idea that the laws of physics are consistent over space and time.
@marcuss.maranto91247 жыл бұрын
I'm a newcomer to physics/chemistry/mathematics. My mind is blown @how amazing these things are. I even have a solar-powered Einstein figure that points to his head as if to say, "Use your brain!" But symmetry? That's a whole Noether thing...
@whatis_asis2 жыл бұрын
Since you asked us to brainstorm on applications of the theorem: what if the transformation was not applied to the object? Could the theorem be applied to an apple’s reflection in a mirror? The object is symmetric when transformed by an external agent, the conversation law is the conservation of edge conditions in the medium of translation. The physical object is no longer physical in the image but preserves the edge conditions in the virtual image. This symmetry also conserves angular incidence via reflection or refraction.
@whatis_asis2 жыл бұрын
Could you infer that if there was symmetry and conservation of some law, then there must be a transformation being applied even if it is imperceptible? For instance, your hands are symmetric about the median plane of the body and they almost perfectly preserve the boundary conditions of the first hand, therefore could we infer that there is a transformation being applied, even though it is imperceptible (such as DNA)?
@pandavroomvroom10 ай бұрын
this the best video about noether's theorem ngl; would love to know how do u mathematically derive it.
@edvogel563 жыл бұрын
What do you think of this idea? - I think this idea and your explanation are beautiful and powerful like Euclid's "Things that are equal to the same thing are equal to each other"(paraphrasing Lincoln's usage . . from the Daniel Day Lewis movie). I am a volunteer STEM educator and insights like these help keep me going. Thank you very much. Have you heard of it before? - Yes but the Wikipedia article didn't bring me the intuition that your video did.
@xj-vn4eo5 жыл бұрын
Well from Classical mechanics, related to what you said in descriptions, Lagrangian and Hamiltonian essentially is the same as Newtonian. But I think these 3 approaches have different perspective so useful in different situations. I think since the theorem can be directly related to the action of the system, it is natural to think of it in Lagrangian framework. But I believe Noether's theorem is more general in mathematical sense as a great contribution to abstract algebra, as you indicated in the video. Sorry I did not really say much actually but there is a LOT to say about it if one chooses to focus in such route.
@shawniscoolerthanyou8 жыл бұрын
Great video! My QM prof mentioned Noether's theorem in passing so I figured I'd check it out.
@nujuat8 жыл бұрын
Hey these are the things that are "linked" together with the uncertainty principle - the plot thickens!
@LookingGlassUniverse8 жыл бұрын
Ding ding ding! Well spotted. I'm writing those videos now.
@sp4958 жыл бұрын
come back! your videos are awesome!
@LookingGlassUniverse8 жыл бұрын
Really soon! Promise :)
@sp4958 жыл бұрын
+Looking Glass Universe woo! I'm excited!
@tomlowe63828 жыл бұрын
If you can, could you (or someone else) summarize Dirac/bra-ket notation briefly, or perhaps just provide links to a webpage that you think summarizes it in layman's terms. As a British High-school student watching your (really fantastic) videos out of simple curiosity, i think it would help immensely with my understanding of the quantum mechanics ones in particular. Thanks so much :)
@rlittlefield26917 жыл бұрын
Very nice, my understanding of conservation laws come from Chemistry, so this explanation really rounded out my understanding. In Chemistry, the conservation of matter means that no new matter can form, nor can it disappear. While this is workable and provable, we are guessing that it is not true based on the big bang theory. It is my guess that being that E = MC2 that saying matter and energy are the same thing, that you have proven that it only conserves if there is symmetry, that the size of space itself creates potential energy and that is the source of all matter.
@jonmay12906 ай бұрын
This video is far better than all the ones I've seen. Explain what the usefulness and not restating that ball go straight if thrown in a vacuum. Kids new that without seeing a theorist! I'm now much less frustrated.
@mc44449 жыл бұрын
A theorem of great scope yet a simple idea, sounds exactly like something a mathematician would come up with. It should definitely be mentioned in the classrooms in some form. I've heard of super symmetry and CPT symmetry, stuff to look up. So a system like a falling apple doesn't have translational symmetry but it can still have time translation symmetry since the total energy is conserved.
@mdasaduzzaman69217 жыл бұрын
Well i learned the theorem in a more complicated way. I think this is the best way to think of it.Its really helpful.Thank you
@sethapex96708 жыл бұрын
this is very interesting, never thought that there was any reason for conservation laws, much less that they were connected to symmetries. from what i found about super symmetry it appears to be a type of transformation involving particle's spin value, which would imply that fermions and bosons are simply a transformation of this value. however because there are no superpartners that have been discovered, the symmetry is said to be spontaneously broken.
@Aei89449 жыл бұрын
Hey. What a great explanation of the magnificent Noether's Theorem. It's applications in QM are huge and the connection to supersymmetry gives us String Theory. Thanks so much for these videos, they are unreal. I'd love to talk further, if you're down :)
@saikat93ify7 жыл бұрын
I have heard of invariants in Mathematics in combinatorics and game theory. The idea is to look for some mathematical quantity that is invariant under an operation. This helps a lot. For example, in the game Nim - the invariant is the XOR of all the number of stones in each pile !
@swiftswing117 жыл бұрын
The moment when you realize that the conserved quantity and the symmetric quantity is blended in together in the Heisenberg's uncertainty principle.
@MrGarry14107 жыл бұрын
Reading this feels like it should give me great insight, but it doesn't. Please tell me more of your thoughts that you have about this.
@swiftswing117 жыл бұрын
I asked my professor about this. he said that symmetric of time mean you can do that same experiment at any given time the result will be the same, symmetric of space mean you can do at any given position in space, it will be the same (similar to Einstein's relativity). I have a very strong sense that if an object doesn't move, I cannot know its velocity, similar to if time doesn't past, I cannot know its energy. It sounds very difference from the symmetric above, but when I try to combine it (and possibly doing some math), my mind got very fuzzed and still stuck in the idea for month. some other conservations like the conservation of charge, came natural as the other way to speak that the divergence of a curl is zero (derive from Maxwell's EM equation) which is a kind of symmetric. Feynman's lecture has just been published public so i might spend time watching it.
@Baekstrom7 жыл бұрын
Thanks. Now I am ignorant on a much higher level.
@Shazrazmatazisaspaz9 жыл бұрын
I found your channel today while procrastinating boring exam revision and now I am watching vid after vid after vid non-stop. I am in my third year of engineering and watching these videos makes me wish I had gone with my gut and studied physics instead. Thank you for helping me rediscover my love for physics and maths (looking up Hamiltonian mechanics atm so I can better understand Noether's theorem). Regarding this vid specifically: we often rely on "conservation of mass" in engineering. After watching this vid I'm wondering, what kind of symmetry would lead to conservation of mass?
@Shazrazmatazisaspaz9 жыл бұрын
Is conservation of mass even a real law like conservation of energy? Or is it more of an assumption rather than a law?
@LookingGlassUniverse9 жыл бұрын
+Shazrazmatazisaspaz Thank you for the really sweet comment :)! And it's not at all too late for studying physics, esp when you have an engineering background! Also, great question! I think that conservation of mass is similar to conservation of charge- and there is a version of noether's theorem that applies to that. It comes from 'gauge symmetry' which you may have heard of in electromagnetism? But, conservation of mass is infact a special case of conservation of energy, since energy and mass are the same thing. Kind of cool right?
@Shazrazmatazisaspaz9 жыл бұрын
+Looking Glass Universe Yeeahh after asking that question I did some more research and found out that mass and energy are the same thing. HEAPS COOL
@LookingGlassUniverse9 жыл бұрын
Right??
@Shazrazmatazisaspaz9 жыл бұрын
Defs. I just read that if c were expressed in natural units then the distance and time units are related so that light travels 1 distance unit in 1 time unit (this is kinda cool because it does away with pesky metres and seconds). And so in natural units c=1, and then E=mc^2 reduces to just E=m. Which really highlights how samesame-but-different energy and mass are!
@SomeGuy11178 жыл бұрын
Why haven't there been any new videos? This was one of my favorite channels.
@Harlequin3141597 жыл бұрын
Thanks. Studying momentum generating functions in Finance/Economics and its nice to have the real physics concepts salient :D
@tiburcarodrigues79856 жыл бұрын
In statistics that's a different stuff. It's a function used to compute mean values of things snd measures of deviation from a certain value.
@samgdotson7 жыл бұрын
This was a lot easier to understand than my professor's messy lecture notes.
@quest27189 жыл бұрын
Not many videos on Noether's theorem. Thanks.......
@normanofthetempest73472 жыл бұрын
This concept is really something. I havent been in school for 20 years and I am kind of angry they never discussed Emmy Noether at all. Wow. I dont see anyone ever talk about Emmy Noether thats sad. Granted I dont hang out in math science circles but I dont think I've ever heard of her on tv or in a book.
@schmetterling44772 жыл бұрын
It's typically second or third semester material in university, but you are correct. We should make Noether's theorem part of high school science. It's the central piece of modern physics and it can be explained at the high school level.
@metasamsara2 жыл бұрын
Split your symmetry into more symmetries. Will make understanding the curves a lot easier and more intuitive. I think like this since I was a kid I have no academic training and I'm working on creating my own theory of quantum time relativity to disprove Newtonian mechanics and Einstein's theory of general relativity with just this concept xD I naturally split each rotational and translational 3D axis into symmetries to understand motions at the core of my perception. I research to understand what I don't know yet when it's not logical, but it's just like a game of pool with magnetic and other forces acting upon the symmetries, either linearly or exponentially, while observing the laws of conservation and other transformations/reactions based on "sacred" geometries and energy charges. Entropy takes care of slowly shifting the balance and we perceive that as time, but it is a local phenomenon and not a linear universal axis translation like so many people think of time as.
@susanvallarino72224 жыл бұрын
THIS IS THE MOST SIMPLE AND BEAUTIFULLY PUT TOGETHER VIDEO TO EXPLAIN PHYSICS TO EVEN CHILDREN! MAY GOD CONTINUE TO BLESS YOU AND ALL YOU DO YOUNG LADY!
@NirielWinx4 жыл бұрын
Praise Vishnu, indeed.
@bethanyjermann5696 Жыл бұрын
Best explanation I've heard yet. I almost get it. Thanks :)
@patrice3739 жыл бұрын
I didn't know that relation, you've oppened doors for new reflexions, thank's a lot ... it's as strong as the Heisenberg uncertainty, the symetry of Quantum properties and mass-energy-speed-time relation, it must be linked somehow … One thing I'm sure : your video is awesome, they all are, you manage to explain complex concepts in a very pleasant, elegant and graspable way and with nice little real life examples and illustrations.
@PeterBaumgart1a6 жыл бұрын
Some of the comments below indicate some confusion that has it's origin in an inaccuracy (false statement) in this video. A system is not considered "symmetric" if it has "the same energy" when it is (for example) "moved to over there," but rather when it "looks" in all relevant aspects (i.e. in a sense "IS") the same after it is "moved to over there." It's not the "energy" but the "being" (appearance in all relevant ways) that is " the same" after the transformation. (Energy by itself, is of course "just another conservation law" that is the result of "remaining the same" under a translation in time, and thus falls under the same framework of "symmetry corresponding to a conservation law," as also postulated (discovered?) by Emmy Noether...)
@chaitanya.awasthi7 жыл бұрын
There is an excellent book on this topic called Emmy Noether's Wonderful Theorem by Dwight E. Neuenschwander. It gets a bit dense at times but I think the author has done a fabulous job. Thanks!
@adithyan92632 жыл бұрын
wow great video. i kinda had a thought abt something similar before. if we shrunk(or expand) everything in our universe by decreasing the size of atoms by a constant, would that be symmetric. i think it would be and if yes what if we could put normal atoms and minimized atoms in a room together how would they interact with each other? Another unrelated question: life(or intelligent life), exists and has a size of some huge number times the size of the atom. but isn't that sort of arbitrary.Could life evolve in the quantum world. but then it wouldn't exactly be " life" as we know it but something like that.All organisms we see are based on heaps of molecules(hail carbon). but could life form out of chunks of subatomic particles maybe a bit of quarks, muons, etc ???
@fg_arnold5 жыл бұрын
Excellent bit of toe-dipping, as usual. I'm amazed I only discovered this channel a week ago. All the vids are SO thought-provoking & SO entertaining - a wonderful combo - and the homework questions an added bonus. The link in the description here is broken: those lectures (based on Goldstein) are currently at www.physics.usu.edu/torre/6010_Fall_2016/Lectures.html. Lecture 4 (the 5th in the list) describes Noether's theorem & Lecture 12a discusses generators.
@benarnao17209 жыл бұрын
Not entirely on topic but i feel like more and more evidence suggests that the universe isn't a bunch of a independent pieces as is intuitively thought, but rather one connected system and the idea of duality/supersymmetry seems to be most fitting at this point.
@PankajBhambhani645 жыл бұрын
Thanks for the wonderful video! I'm not a physicist but I've heard about Noether's theorem while reading about the "Theory of Everything". Maybe you can follow up by talking about Gauge Symmetries?
@NwZ27 жыл бұрын
"100% not jealous" rofl, totally not jealous but definitely kinda cute. The production value in these videos sure does deliver.
@fminc6 жыл бұрын
this is a great channel, thanks
@aidanlara18 жыл бұрын
Posted this on Veritasium's video on Quantum Entanglement was hoping you could help read it and probably comment thanks :) Before, when I had studied different aspects of QM such as spin and wave functions I thought of them as separate concepts and therefore never fully understood them until I saw this video and decided to compare it to that of "A Brief History Of Time" It was only then that I understood that these concepts and ideas were all intertwined which led to me to discuss the possibilities of FTL travel mentioned in this video. Firstly, this video does not include a mention to or explanation of (collapsing) wave functions but what it did mention is that these "entangled" particles do not have any hidden information within them which would therefore mean that examining the spin of 1 particle in a pair would directly influence the outcome of the results found in observing the other particle instead of just revealing hidden information in the particle as previously thought. Now let's incorporate the concept of collapsing wave functions.So the examination of a particle or said particle's spin collapses the probability of it's position into one state, now if knowing the state of one of these entangled particles doesn't just tell you the state of the other but has a direct influence on it therefore collapsing the wave function of one particle also collapses the other particle's two possible states (spin up or down). Now when one examines a particle such as one in the double slit experiment it INSTANTANEOUSLY collapses to one state(passing through only one slit) So therefore these entangled particles do carry "information" over an arbitrary distance faster than light if not instantly. Interested to hear what people think :) P.S it helps to not think of spin as the traditional sense of the word but rather as a way of saying different states a particle can be in (for explanation's sake)
@evalsoftserver6 жыл бұрын
Aidan Adams It's Called Normalization
@adityakhanna1139 жыл бұрын
wow! I really added the la-la-la myself when the particle flew by... and then you added it.. that's cool...
@hongkai20009 жыл бұрын
Proof (in classical mechanics): A symmetry of a physical system is defined by: Say we have a Lagrangian. If, under some transformation q'= q+f(q)δ , the Lagrangian is invariant (remains the same), or equivalently, the change in the Lagrangian δL=0, then the system is said to be _symmetrical_ under that transformation. In canonical coordinates, from the chain rule, δL= ΣdL/dqi δqi over all i (unfortunately, due to circumstances beyond my control, I cannot write i as a subscript). With some manipulation, this can be written as: The time derivative of pif(qi)δ. (confusing, I know) Since δL=0, The time derivative of pif(qi)δ=0 Thus pif(qi)δ is conserved. Did I do this right? Tell me if there's anything wrong.
@johnarnold3128 жыл бұрын
You a very able teacher. I wish you’d try your hand at teaching calculus maybe add some formulas here and there.
@abcdef20698 жыл бұрын
since spin is conserved, there exists su(1) su(2) symmetry. since charge is conserved, su(3) symmetry exists. find really good su(4) su(5), su(6) symmetries... like super symmetries, then you can automatically have what physical property was conserved in that symmetry, then people will bow down to your intelligence.
@judgeomega7 жыл бұрын
you could twist things around and define energy as things which contain a specific type of symmetry
@EugeneKhutoryansky9 жыл бұрын
Interesting. But, since the definition of a symmetric system depends on the energy being constant, this means that the definition of symmetry depends on the definition of energy, and the definition of energy can be different in different mathematical systems.
@dontwanttojoingoogle17999 жыл бұрын
+Eugene Khutoryansky Logically false (and nonsense). I don't need the word 'energy' to define a symmetric system. The so-called 'definition' you speak of does NOT "depend" (whatever that means) on energy being "constant".
@xXxBladeStormxXx9 жыл бұрын
+Eugene Khutoryansky No. See, you don't quite understand what is being said because not much was really being said in this video other than how great Noether's theorem is. Symmetry is an abstract idea. You can apply the idea to mathematical sets or an actual physical lattice of atoms.
@shantanukawale91276 жыл бұрын
you defined it well
@SvenBVBKlopp096 жыл бұрын
this is bullshit and you run a physics video channel?
@xXProMetalicXx5 жыл бұрын
Math is just a prank
@Hecatonicosachoron9 жыл бұрын
Oh, I was looking at this some time ago... I remember that I found out that dilatation symmetry implies the tracelessness of the stress-energy tensor, which is definitely a peculiar way of describing a 'conserved quantity'... Funnily enough I had been thinking of different generators and the symmetries they imply, but I can write about that a bit later
@starwarsjk997 жыл бұрын
Position/translation corresponds to momentum Rotation corresponds to angular momentum Time corresponds to energy Is this related to Heisenberg uncertainty principle
@SSJHF7 жыл бұрын
I see a lot of comments asking for certain explanations to be approached from different directions. Some even say the implication of one thing to another is in the "wrong" direction. However, all the implications mentioned in this video actually go both ways. It may be that people are taught the implication one way only, so upon seeing this video they think it incorrect to go the other. Rest assured the in the examples it may be done in either direction.
@movazi Жыл бұрын
Beautiful presentation, as usual. Thx
@thermodynamics4587 жыл бұрын
Beautifully done. You obviously have had quite a bit of formal training in Physics/Maths. to produce something of such quality.
@Johnny200220023 жыл бұрын
The prosody of her voice is like she’s holding back laughter. She must really like this stuff.
@johnathanmonsen65674 жыл бұрын
Two things come to mind for me- First, I saw a different video on it, that made it a bit more clear what it would mean for time NOT to be symmetric, but I didn't quite understand it then and I don't remember it now... wish I could figure that out. Second thing- it occurs to me, could we consider the speed of light to be a value which is conserved? It's a constant, after all. So, then, could we then find a transformation that holds symmetry in respect to the conservation of that value? And then, would that let us better hypothesize what would happen if that symmetry was BROKEN?
@sagarrathore5400 Жыл бұрын
Hi, could you please update the links in description? Great video btw :)
@劉為尹8 жыл бұрын
Thanks for the great video, but can this explain other conservation quantities? Take charge conservation for example. Take an electron as the object (or say, the system) moving toward a proton (just like the translation example about 6:30 in the video), its energy is changed, but the charge still conserved.