actually it is infinitely complicated and also not complicated at all. it is infinitely complicated because it is always expanding and is everything so there is always more than we can think. and it isnt complicated because if it is everything we already know what it is.
In the book "Love and Math" the author, Edward Frenkel, takes some time to explain symmetries and their relation to physics. That's an interesting read anyway, try it.
I love PBS Space Time. My understanding of special relativity and GR wouldn’t be anywhere near what it is today without it. This is not a comment about today’s episode, but I realise I’m fully unprepared to detect whether they ever start to veer off into crackpot fringe physics territory. Or into crackpot “I’ve got a grand-unified-theory of everything based on a Gauge Theory but won’t publish it because the formal academic system of peer review has been institutionally captured and is keeping me down man” like I’ve seen in certain corners of the interwebs. I guess that short of becoming a professional physicist myself or dedicating all of my spare time to learning, that uncertainty the nature of the bargain :)
It is also clear you do not understand how to not a be cringe virgin maybe instead of watching these video you should hit the gym noodle arm lookin ass
['But Small, half-smart creatures have a fierce talent for denying the Inevitable, for Balking and complaining about [REDACTED] that don't Exist and consequences that should be borne in Silence.'.]
I love being walked carefully through Feynman diagrams. For a moment I think "I understood that" but then I realize a moment later, "Nope, I got nothing."
@@westyphys and the diagrams actually make things *simpler* to understand! Props to Feynman et al for understanding the equations well enough to come up with the diagrams.
Lol yes, it's kinda the same with everything on a higher complexity level here or other channels. I've accepted that i generally don't understand anything in the end, but i still enjoy watching and trying.
Remember how in school they'd have a teacher specifically go over the same concept for two weeks, teaching you it over and over until it clicked, testing you on what you know and making sure you understood the concepts? Don't feel bad if your adult brain doesn't pick up quantum mechanics in 20 minutes. Rewatch. Listen again. Do further research. It'll start to click, pieces will come together, and you'll feel like an absolute genius. It's a great feeling.
The outro to every video having, usually a run-on sentence, an extended play on words to bulk it all back into a thematically relevant and compressed summary of the video inevitably bounding it all back in to the everything-ness of.... Spacetime; it always gets me! Every single time! I love it! ^.^
I understand how this happens. I severely tore and compacted my rotary cuff. Now all my shirts slump to one side. Most of the time i dont notice it, but i now instinctly adjust my shirt. When i do i always find my shirt has slumped. That or the camera has a minor black hole in front bending and warping the incoming light.
Me too. All other forces seem like actual forces: Gravity pulls, electricity and magnetism can be attractive or repulsive and the strong force binds nucleons together. But the weak force causes decay...
@@Shenron557 the way I see it- that electron ends up moving at quite a clip after the decay, if it's moving then something must have pushed it, the resulting atom would be a really nice place for the formed electron, but it usually ends up pushed out, leaving an ion. The thing doing the pushing is the weak force? Other things might be contributing to the push- nuclear binding energy, but it's not doing the actual "pushing"
I would LOOOOVEEE a follow-up video on this subject!! As a non-physicist, I have been DESPERATE to understand symmetry breaking, gauge field theory and special unitary groups. This video did more for me than any book I've ready so far but still left me with more questions than answers (as it should!)
You must watch "The most important ideas in the universe" series by Sean Carroll. It's the only serious attempt to explain symmetry groups and gauge theory to laypeople I've seen on TH-cam.
This was definitely one of the harder to understand videos you've done. But I respect that the subject of the electro-weak force is just complicated, so I appreciate the explanation all the same.
quantum decoherence...and.. mmm those..cosmic background radiation videos..and they've done some videos on parity before, alike 1veritasium guy..but yeh this was one of those episodes
Spontaneous symmetry breaking in the electroweak force is like a 4th year university physics concept, which is dealt with in more depth in postgraduate study. It's heavy hitting no matter how you package it,
So, if you heated a region of space above 10^15K, could you get the Electroweak force to break symmetry in a different way? Like how heating and cooling the bar magnets can lead to the group pointing in a different direction.
@@jajssblue I'd guess that since the "original" symmetry break started with 4 massless particles and ended up with 3 massive and a massless one, that the masses of the particles might do a musical chairs and end up in different positions - no new particles, just different masses, leading to different force strengths. *But thaaaat's just a theeeeeory* (hypothesis)
I think to carry this bar magnet analogy forward, consider that the symmetry could break in a different 'direction' every time - sure! That's just what it means for the system to favor one specific direction over the symmetry of all possible choices. What remains the same after the bar magnets cool down is that their total overall "emergent" magnetic properties have the same magnitude, no matter what direction they face. One hunk of magnetite is just as magnetic as another hunk, even if the crystalline structure formed in a different direction - breaking the symmetry in another 'way'. Similarly, while the breakdown of the electroweak symmetry may produce Higgs particles in one trial of the experiment, Z bosons in another, and purely photons in another trial, they all end of having the appropriate masses. In the LHC, zillions of trials are run basically simultaneously, so the restored symmetry of Electroweak becomes the broken symmetry of the Standard Model.
If we have 4 forces that used to be less, how outlandish is it to assume that the forces we currently have can be further broken? Do we have proof that they're 'prime' forces?
I think the fact that you can’t get below 0K, and relatively speaking we’re already in that temperature range means there’s nowhere else to go for these new symmetry breaking stuff to happen. Edit: I suppose you could invoke vacuum decay but I think that’s a separate concept.
@@RecoveryHacker You can go below zero at a quantum mechanical level, but the negative energy state is unstable and will be filled back up. Experimentalists have cooled atoms to negative temperatures with lasers. Similarly, Hawking radiation at black holes has a negative energy state when one particle of a virtual pair falls into the event horizon, and the negative energy is recouped by the black hole shrinking in mass.
I always wonder if the scientists that studied the weak interaction at first were aware that this interaction was indeed a force that can push and pull things. And not just transform. As I understand it it is extremely difficult to measure the actual force of the weak force because it is almost always eclipsed by other forces like electromagnetism.
I think you're right! When I read about experiments that attempt to observe the elastic collisions of neutrinos on giant tanks of some material, what they're looking for is a weak interaction where neutrinos trade a W or Z boson with some material. It's super uncommon, but with the right setup the weak force is a force all the same! I think when W bosons are transmitted, you can expect a particle like a quark to change flavor, often from down to up while also elastically colliding, but weak neutral current uses Z bosons, which carry spin but not (electric) charge. With Z bosons the weak force can be communicated without the same kind of flavor change.
It's definitely possible that at super-low temperature states that we could see unexpected behavior which would indicate a breaking of symmetry. Consider superconductivity, where a magnetic field behaves normally at higher (>90K°) temperatures, but gets expelled from the material at a critical temperature. Could something like that exist for the weak or strong nuclear forces as well?
@@galacticbob1 Consider color superconductivity! en.wikipedia.org/wiki/Color_superconductivity I literally reread that whole article every few months in a hopeful attempt to imagine just how it is that the quarks are trying to hang out together... This is of course, at higher temperature, so I don't know about lower.
The entire time watching this I was just waiting to hear Grant Sanderson's (3blue 1brown) voice explaining some of the math. To think of it, it would be cool to have him on as a guest once...
Matt I'm genuinely bewildered how you can be a professor and do this on the side. I'm an academic too, and I wish I had the time to engage in this type of science communication.
I have a physics and engineering background but still look forward to everything you release - and learn a huge amount. Please keep up the amazing work!
The best proof regarding quantum electrodynamics comes from ontology: 1. A physics theory with a cool abbreviation is inherently better than a physics theory without a cool abbreviation. 2. Quantum electrodynamics has a pretty cool abbreviation. ∴ Quantum electrodynamics is better than other physics theories. _Q.E.D._
I got so confused in school, not starting philosophy classes until after taking AP physics. Why do all these arguments about men and mortals keep ending in a quantum mechanics reference?
@@paulmoir4452 The _other_ meaning of ontology, as applied to research disciplines: a set of concepts and categories in a subject area or domain that shows their properties and the relations between them.
That analogy with the magnets was brilliant. I was familiar with the concept symmetry breaking abstractly before but now I actually understand what it physically means.
I always wondered how such an equation would look like, where you can see/read off that su(1) and su(2) merge. I'd love to see some more math Matt. Even if my amateur astronomer, dangerous half-knowledge of physics is shattered. 🔭🙃
@@alexakalennon All of the original papers on the subject are available through sci-hub. And all sorts of books through Library Genesis. It takes digging to find the best bits of explanation, but it's all there.
you don't need lie groups to understand it. you start with the klein-gorden equation (a linear complex field) and then add a new term to the Lagrangian (the mathematical thing you use to produce the equations of motion, classically you literally just do L = kinetic energy - potential energy) that is quartic rather than quadratic in the field. This allows a potential energy that looks like -r^2 + r^4 rather than just +r^2 (plot it on desmos or something) and the field "drops" to a lower potential state, from the plot you can see that the initial state r = 0 was symmetric when you rotated the system (similar to phase transformation that is mentioned, but this is a *global* symmetry so is not as profound) but the new state won't be. (note the +r^2 potential always has its ground state at r=0, a vacuum, and there is no other such state) This is all well and good but when you combine the complex field with a gauge field (literally by adding a vector potential to L). you will see that you can make a gauge transformation that "compensates" for the broken symmetry *locally*. The result of all of this is that the complex field loses a degree of freedom , the gauge field gains one (photons, which are not the result of a broken symmetry have 2 polarisation states, but W bosons, for instance, have 3 spin states) and also its dispersion relationship changes from omega^2 = k^2 (massless particles) to omega^2 = k^2 + M^2 (massive particles). The mass it gains is related to the mass that the scalar field has, and the mass of say, the Higgs boson (a scalar field) can be predicted. as a motivation for why symmetry is important, any foundational physicist worth their salt can, given the symmetry group of the standard model, derive every equation they could possibly want, the only other thing they need to do is measure constants (like the speed of light or plank's constant).
Yay! The advanced episodes are back. I am honestly learning so much from this channel as someone without a physics degree that loves quantum mechanics and GR. Just gotta say that so that you know it's still super valuable. This is what sets this channel apart from pop-sci to me. I actually have to rewatch parts and think hard about how to imagine it all without it being impossible to parse for a lay person like a textbook this advanced might be.
I need to say thank you so much. This is by far the most concise and understandable explanation of this concept I have ever seen. I want to say that you guys are doing incredible work. I never thought I would see a day where pop science presentation meets the required level of depth on the subject matter to really explain the mathematical underpinnings without getting too far into the weeds.
...all I understood was that double slit visualisation, everything else is as broken as SU(2) and U(1) symmetries below electroweak temperature...:'D ...still liked the episode...xD
It's simple: "adding mass to a photon means adding an extra term to the electromagnetic field stuff in the Schrodinger equation so that it would no longer be invariant to local phase shifts." /s
These amazing videos are packed with information. But he wields these complex terms so masterfully that I feel like we need a "slow mode" where there are pauses after every statement and little reference links everywhere for every term in the statement.
@@querywizard ...well this I can image to some small extent since I've never dealth with Schrodinger equations per se but I persume this "adding a mass term" can only be balanced by adding another "symmetrical" (hypothetical) term to satisfy the overall equation...
Whenever people tell me I'm getting insufferably arrogant at the hospital I watch one of these videos to feel stupid again and back off a bit from terrorizing my students, residents or nurses :)
Agreed Vladimir! I am of above average intelligence but the level of cutting edge of physics these geniuses in the subject work at is beyond me, I think even if I understood what different equation symbols stood for, by a long way!
@@redhatlt Most likely :D But teaching does that to you some times (makes you feel smarter than you really are), that's why I like to drag myself back to reality by looking at actually smart individuals discussing science so hardcore that sounds almost esoteric to me.
It’s like watching the history of science. Which is crazy because I could never stay awake in an actual history class as a kid, but this has my full attention.
“Actually, a visual representation would really help, here.” Funny, that usually works. This time, spinny arrow and woobly lines didn’t help me. Will watch again...and again.
The magnets all pick a direction to align to, up or down, left or right. The choice is arbitrary. Before the choice was made, the system was homogeneous and random
Yeah this time I really don't understand it at all really. I'm going to rewatch a thousand times and get back I understand the intention. It reminds me of understanding vectors in stress tensors
You have a way of explaining these things so casual fans of Cosmology and Physics like myself, feel as if we can at least follow the ideas that you explain.......we may not understand the complex mathematics behind it, but at least we kinda understand.......I hope this makes sense
This episode is such a hurculean task. Well done spacetime team! The spontaneous symmetry breaking illustration is the best analogy I have come across. Thank you!
This video could not have been more timely. I was just talking even today with Dr. Don Lincoln about this in his comments, trying to understand how a single force with (presumably) identical bosons could react differently than each other to changing temperatures and the Higgs field if there weren't already some other differing variable from the start that allowed them to react differently. He was very gracious in helping me try to understand this topic. Now I get to see at least two detailed videos from you on the subject. Perfect timing. Thanks so much!
Would love to see more animation analogies of the U1 and SU2 symmetries of the electroweak field. I think the "clock" animation was getting close, but then you moved on and over my head.
Just out of curiosity, could you provide references for this material for those wanting to read more about this. I've noticed with this and other episodes a lack of references except when citing specific publications.
You guys should go onto the Portal with Eric Weinstein. You have mentioned his work in the past and has a really interesting perspective on gauge theory.
Thank you. Not enough people tackle this complex subject for us non-professional astrophysics enthusiasts. I really appreciate the thorough explanation using simplified analogies that even I can understand (maybe)
“How does one force separate into multiple” > “How does one force become separated into several forces?” “Separate” is a transive verb; “multiple” should not be used where “several” / “numerous” / “many” is meant.
If we heart up the universe, until Electromagnetism and the Weak force merge and cool it down again, would the Weak force crystallize into different properties?
No, we can do this as the LHC. The Higgs field, responsible for the symmetry breaking, imposes a lowest energy configuration that always forces the same symmetry breaking. And good thing too, or we might trigger 'vacuum decay'.
Why do physicists talk so weird? “Symmetries” are said to exist when particles look random; symmetry is “broken” when they all look… symmetrical… argh!
Because that's what symmetry IS. Symmetry is broken not when particles look symmetrical but when they look IDENTICAL. You're used to lower symmetry where you can divide something like a cube up into a few limited symmetries rather than something like a sphere which has infinitely many symmetries.
if you're talking about the dipoles analogy, we should keep in mind that the symmetry in question was related to the DIRECTIONAL behaviour of the entire system. *when all of the magnets are jumbled up,* the SYSTEM will basically behave the same from every direction *(i.e. it will be symmetric).* by contrast, *when all of the magnets are aligned pointing upwards,* the UP and RIGHT directions will behave in noticeably different ways *(i.e. the system will be asymmetric).* I think a better term for this type of symmetry/asymmetry is "isotropy"/"anisotropy", check that out on Google. Hope that clears it!
"The most famous paradox in physics, first posed by Stephen Hawking fifty years ago, has been solved. In a landmark series of calculations, physicists have proved that black holes can shed information - if you jumped into one, you wouldn't be gone for good. This means that space-time is not the root level of reality, but an emergent structure from something deeper." This was straight out of a newsletter I'm subscribed to. Would love to see Matt cover this in a future episode! EDIT Here's a direct link to the article www.quantamagazine.org/the-black-hole-information-paradox-comes-to-an-end-20201029/ Here's a link to the newsletter that I read this in futurecrunch.com/fc114/
@@ThatCrazyKid0007 I do not, It was in an email newsletter I get. The newsletter is called Future Crunch and it covers news about science that doesn't often get picked up by larger news outlets.
@@ThatCrazyKid0007 Good news, I went back and found the link tot he article quoted in the newsletter. www.quantamagazine.org/the-black-hole-information-paradox-comes-to-an-end-20201029/ If you're interested in the newsletter itself, I found an online version of it here futurecrunch.com/fc114/
Forget where one theorist said black holes are not the same as the early universe where all 4 forces were somehow unified into a single force. Maybe I misheard what was really being said but it would seem to my limited understanding that it would be the case that inside a singularity some of the forces should be unified. It's also interesting to hear that they sort of pair up like with the electro-weak force shortly after the big bang. Great episode as usual and like some of the comments I understand a small fraction but always interesting.
@@wasp89898989 Yeah I know about entropy I mean all of the matter and the forces that hold all the matter-energy together. They all seem to fight entropy.
11:50 "s(1) field" means U(1) field? Btw, since U(1) × SU(2) ≅ U(2), does the combined U(2) correspond to something meaningful? EDIT: replaced equality by isomorphism.
It looks like that spot in the video has "SU(2) x (U)1", and I don't ever see U(2) or S(1) written. The SU(2) x U(1) is the only way to write out the electroweak force, and the 'cross' operation is always required. I've never seen it written as, say, a single term.
@@zzztopspin Is it really the Cartesian product? Then the isomorphism holds. Mathematically, SU(2) is isomorphic to U(2)/U(1). The latter can be interpreted as "U(2): anything unitary on a 2-vector base, /U(1): but ignore global phase shift". Now the isomorphism I gave is basically just the same in reverse, reconstructing U(2) from SU(2) and a global phase. Note that "phase" is to be read as mathematical explanation of the isomorphism, not something physical.
@@cmilkau I think you're interpreting this quite mathetmatically! You probably know more about Lie algebra than I do, but I think it's important to remember that for physics, models of math (Gell-Mann matrices, Neother's theorem, etc) are often developed "so that" the empirical data can be explained. If a unitary matrix in general has a determinant with magnitude 1 (complex or real) but a special unitary matrix has determine of 1 (real only) then these ideas would have a significantly different realization were they applied to the empirical world. As for your question about if it's REALLY the cartesian product, I can't say I understand what you're asking! At the end of the day, I'm pretty sure the laws of physics at large govern the particle interactions in a clear cut way (I'm not saying deterministic), so that whatever math the particle physicists are using is probably the way to do it. Until we get a working theory of quantum gravity, that is!
Finally you made me fully understand the concept of broken symmetry in the state of functions while conserving symmetry in the equations describing the latter's relations!
So... in layman terms for someone like me that needs them... When the electroweak field was unified it had the 4 massless bosoms, but when it "broke apart", breaking the symmetry of the field, it gained bosoms with mass? Please someone tell me if my understanding is correct xD, I think the idea in itself is pretty fascinating and I want to properly understand it.
for me - this is aa prime example as to why many folks switch off listening. It just seems to be explained in a manner that could be simplified BUT of course, I am a dummy and did not request a vid on this subject to be put in "lay(z)wo/mens terms" Great Vid Doh! x
“Our universe seems pretty complicated”
Understatement of the year, Matt.
Exactly! ;p
idk about understatement of the year, it is 2020 after all
Actual understatement of the year: calling our 8-months-and-counting-confinement "quarantine"
actually it is infinitely complicated and also not complicated at all. it is infinitely complicated because it is always expanding and is everything so there is always more than we can think. and it isnt complicated because if it is everything we already know what it is.
@@wy477x You are assuring on the basis of if. It can be "if it is not" also.
This is the first episode in a long time where I really didn’t understand much of anything. My head hurts
Try binge watching it til the next episode comes
In the book "Love and Math" the author, Edward Frenkel, takes some time to explain symmetries and their relation to physics. That's an interesting read anyway, try it.
I love PBS Space Time. My understanding of special relativity and GR wouldn’t be anywhere near what it is today without it.
This is not a comment about today’s episode, but I realise I’m fully unprepared to detect whether they ever start to veer off into crackpot fringe physics territory. Or into crackpot “I’ve got a grand-unified-theory of everything based on a Gauge Theory but won’t publish it because the formal academic system of peer review has been institutionally captured and is keeping me down man” like I’ve seen in certain corners of the interwebs.
I guess that short of becoming a professional physicist myself or dedicating all of my spare time to learning, that uncertainty the nature of the bargain :)
Me too but I'm stoned
Same, I usually understand 60-80% of the video, but this time it would be 20% at absolute best
I can't even imagine how satisfying it must have been when this theory got proved at CERN.
They were all dead.
Dead satisfied
@@n3wm3r1c5 lol
Proven
I am sure all the scientists didn't expect it to be proven true either. They definitely went home dancing thinking damn how did we get that right.
Spacetime is so good it makes me feel like I understand things that I DEFINITELY do not understand.
They're so good, they make me feel utterly lost on things I thought I understood.
It is also clear you do not understand how to not a be cringe virgin maybe instead of watching these video you should hit the gym noodle arm lookin ass
@@MrMegaStega and you think, you randomly crapping unter every 2nd comment makes you look stronger in any way? lol
@@MrMegaStega oh yeah, and you’re a strong looking boy for insulting someone for no reason just to make yourself look tough aren’t ya, mountain man
['But Small, half-smart creatures have a fierce talent for denying the Inevitable, for Balking and complaining about [REDACTED] that don't Exist and consequences that should be borne in Silence.'.]
Hey matt! Just want to say I appreciate you and the whole SpaceTime team! You guys are by far my favourite TH-cam channel!
Completely agreed!
Yeah I agree
Agreed
Agree
Agre
I love being walked carefully through Feynman diagrams. For a moment I think "I understood that" but then I realize a moment later, "Nope, I got nothing."
gunna have to watch this a couple times i think
I made my masters degree in this very field and sometimes still feel the same way... :D
@@westyphys and the diagrams actually make things *simpler* to understand! Props to Feynman et al for understanding the equations well enough to come up with the diagrams.
Lol yes, it's kinda the same with everything on a higher complexity level here or other channels.
I've accepted that i generally don't understand anything in the end, but i still enjoy watching and trying.
Remember how in school they'd have a teacher specifically go over the same concept for two weeks, teaching you it over and over until it clicked, testing you on what you know and making sure you understood the concepts?
Don't feel bad if your adult brain doesn't pick up quantum mechanics in 20 minutes. Rewatch. Listen again. Do further research. It'll start to click, pieces will come together, and you'll feel like an absolute genius. It's a great feeling.
The outro to every video having, usually a run-on sentence, an extended play on words to bulk it all back into a thematically relevant and compressed summary of the video inevitably bounding it all back in to the everything-ness of.... Spacetime; it always gets me! Every single time! I love it! ^.^
You did it perfectly yourself :P
Matt's t-shirt is violating symmetry :(
No, the t-shirt is straight, Matt's head is on crooked.
In every episode... :(
I understand how this happens. I severely tore and compacted my rotary cuff. Now all my shirts slump to one side. Most of the time i dont notice it, but i now instinctly adjust my shirt. When i do i always find my shirt has slumped.
That or the camera has a minor black hole in front bending and warping the incoming light.
He's been working out asymmetrically
You're not cool in 2021 (and can't afford a $90 t-shirt) if your t-shirt isn't flimsy and ill-fitting.
"Not very satisfying" is EXACTLY how I've always felt about the radioactive decay definition of the weak force!!
Me too. All other forces seem like actual forces: Gravity pulls, electricity and magnetism can be attractive or repulsive and the strong force binds nucleons together. But the weak force causes decay...
@@Shenron557 Gravity is not a force according to most physicists.
@@Shenron557 gravity doesn’t actually pull; gravity warps space/time
@@Shenron557 the way I see it- that electron ends up moving at quite a clip after the decay, if it's moving then something must have pushed it, the resulting atom would be a really nice place for the formed electron, but it usually ends up pushed out, leaving an ion. The thing doing the pushing is the weak force?
Other things might be contributing to the push- nuclear binding energy, but it's not doing the actual "pushing"
I once shot a man for arguing the radioactive decay definition of the weak force.
I would LOOOOVEEE a follow-up video on this subject!! As a non-physicist, I have been DESPERATE to understand symmetry breaking, gauge field theory and special unitary groups. This video did more for me than any book I've ready so far but still left me with more questions than answers (as it should!)
You must watch "The most important ideas in the universe" series by Sean Carroll. It's the only serious attempt to explain symmetry groups and gauge theory to laypeople I've seen on TH-cam.
This was definitely one of the harder to understand videos you've done.
But I respect that the subject of the electro-weak force is just complicated, so I appreciate the explanation all the same.
quantum decoherence...and.. mmm those..cosmic background radiation videos..and they've done some videos on parity before, alike 1veritasium guy..but yeh this was one of those episodes
Yeah this one's a deep dive if you really want to get it. Gonna need to watch a few more times.
Il is quite a complex subject Indeed.
Spontaneous symmetry breaking in the electroweak force is like a 4th year university physics concept, which is dealt with in more depth in postgraduate study.
It's heavy hitting no matter how you package it,
@@hyperduality2838 Words don't mean anything I agree
So, if you heated a region of space above 10^15K, could you get the Electroweak force to break symmetry in a different way?
Like how heating and cooling the bar magnets can lead to the group pointing in a different direction.
I like this question a lot! I wonder if there is a change, how it would be expressed? More particles? Different force strengths? Heavier particles?
@@jajssblue I'd guess that since the "original" symmetry break started with 4 massless particles and ended up with 3 massive and a massless one, that the masses of the particles might do a musical chairs and end up in different positions - no new particles, just different masses, leading to different force strengths. *But thaaaat's just a theeeeeory* (hypothesis)
huh, now there's a thought! i'd love to know the answer
The LHC experiments have shown it breaks the same way every time. I think the bar magnet analogy was a bad one.
I think to carry this bar magnet analogy forward, consider that the symmetry could break in a different 'direction' every time - sure! That's just what it means for the system to favor one specific direction over the symmetry of all possible choices.
What remains the same after the bar magnets cool down is that their total overall "emergent" magnetic properties have the same magnitude, no matter what direction they face. One hunk of magnetite is just as magnetic as another hunk, even if the crystalline structure formed in a different direction - breaking the symmetry in another 'way'.
Similarly, while the breakdown of the electroweak symmetry may produce Higgs particles in one trial of the experiment, Z bosons in another, and purely photons in another trial, they all end of having the appropriate masses. In the LHC, zillions of trials are run basically simultaneously, so the restored symmetry of Electroweak becomes the broken symmetry of the Standard Model.
My brain definitely melted on this one
The example of spontanious symmetry breaking of a magnetic field at the Curie temperature is brilliant.
"The midichlorian" lmao
I love you, Matt
“The midichlorian.”
Me: **head meet desk while snort laughing**
He said that seconds after I read your comment
when i typed in the google i found its related to something in biology. Lmao😂
@@dipakshisarma2903 Uhhhh it's from Star Wars lmao
@@ava_niche ohh is that so ? but it also plays well with the biological meaning.
If we have 4 forces that used to be less, how outlandish is it to assume that the forces we currently have can be further broken?
Do we have proof that they're 'prime' forces?
That is quite an interesting idea
I think the fact that you can’t get below 0K, and relatively speaking we’re already in that temperature range means there’s nowhere else to go for these new symmetry breaking stuff to happen.
Edit: I suppose you could invoke vacuum decay but I think that’s a separate concept.
@@sphaera2520 Didn't Sixty Symbols do a video saying you can actually go below absolute zero? You just can't get *to* absolute zero iirc.
@@RecoveryHacker You can go below zero at a quantum mechanical level, but the negative energy state is unstable and will be filled back up. Experimentalists have cooled atoms to negative temperatures with lasers.
Similarly, Hawking radiation at black holes has a negative energy state when one particle of a virtual pair falls into the event horizon, and the negative energy is recouped by the black hole shrinking in mass.
@@RecoveryHacker It sort of is :) th-cam.com/video/yTeBUpR17Rw/w-d-xo.html
This one was definitely worth waiting till the end. I was a bit confused for a while but it came together beautifully in the end! Great vid!
CGP Grey told me about the great hexagon of Saturn and now I'm gonna need you to tell me more, please and thank you ❤️
Dr. Becky Smethurst has a great video about it on her channel that I highly recommend:
th-cam.com/video/PCpis-SiZ0c/w-d-xo.html
@@ConcertsAtHome THANK YOU! Watching now
I always wonder if the scientists that studied the weak interaction at first were aware that this interaction was indeed a force that can push and pull things. And not just transform.
As I understand it it is extremely difficult to measure the actual force of the weak force because it is almost always eclipsed by other forces like electromagnetism.
I think you're right! When I read about experiments that attempt to observe the elastic collisions of neutrinos on giant tanks of some material, what they're looking for is a weak interaction where neutrinos trade a W or Z boson with some material. It's super uncommon, but with the right setup the weak force is a force all the same!
I think when W bosons are transmitted, you can expect a particle like a quark to change flavor, often from down to up while also elastically colliding, but weak neutral current uses Z bosons, which carry spin but not (electric) charge. With Z bosons the weak force can be communicated without the same kind of flavor change.
It's definitely possible that at super-low temperature states that we could see unexpected behavior which would indicate a breaking of symmetry.
Consider superconductivity, where a magnetic field behaves normally at higher (>90K°) temperatures, but gets expelled from the material at a critical temperature. Could something like that exist for the weak or strong nuclear forces as well?
@@galacticbob1 Consider color superconductivity!
en.wikipedia.org/wiki/Color_superconductivity
I literally reread that whole article every few months in a hopeful attempt to imagine just how it is that the quarks are trying to hang out together... This is of course, at higher temperature, so I don't know about lower.
The entire time watching this I was just waiting to hear Grant Sanderson's (3blue 1brown) voice explaining some of the math. To think of it, it would be cool to have him on as a guest once...
Matt I'm genuinely bewildered how you can be a professor and do this on the side. I'm an academic too, and I wish I had the time to engage in this type of science communication.
I have a physics and engineering background but still look forward to everything you release - and learn a huge amount. Please keep up the amazing work!
A new force has been discovered in these new '20s: the ElectroSwing force.
What is the mechanism of this force.
@@WaqarKhan-ws4uj I think he is talking about music.
@@WaqarKhan-ws4uj it acts upon your ears, causing a rhythmic motion of the body in response.
He's definitely got some brass.
@@内田ガネーシュ r/whooooosh
The best proof regarding quantum electrodynamics comes from ontology:
1. A physics theory with a cool abbreviation is inherently better than a physics theory without a cool abbreviation.
2. Quantum electrodynamics has a pretty cool abbreviation.
∴ Quantum electrodynamics is better than other physics theories.
_Q.E.D._
Tautology? Ontology is the study of being.
KED
Lmao
I got so confused in school, not starting philosophy classes until after taking AP physics.
Why do all these arguments about men and mortals keep ending in a quantum mechanics reference?
@@paulmoir4452 The _other_ meaning of ontology, as applied to research disciplines: a set of concepts and categories in a subject area or domain that shows their properties and the relations between them.
The irony of Matt's shirt neck while talking about symmetry 😅
I suppose that's a representation of symmetry breaking
Its symmetrical in curved space.
OMG. It's been a while since I had my head explode while watching a spacetime episode!
That analogy with the magnets was brilliant. I was familiar with the concept symmetry breaking abstractly before but now I actually understand what it physically means.
I'm with you there, this is the first time I have properly grasped that randomness is symmetrical and that breaking symmetry is creating order.
I am super addicted to this channel now, please don't stop, ever, even when you reach the end of .... spacetime.
I always wondered how such an equation would look like, where you can see/read off that su(1) and su(2) merge. I'd love to see some more math Matt.
Even if my amateur astronomer, dangerous half-knowledge of physics is shattered. 🔭🙃
To do that though is to mathematically formulate the Higgs mechanism. That is of course much easier to say than to do, and is even harder to explain.
@@Erin-ks4jp I agree!, yet I would love to get a hint. Or a book...for I don't have anything on QM any more.
@@alexakalennon All of the original papers on the subject are available through sci-hub. And all sorts of books through Library Genesis. It takes digging to find the best bits of explanation, but it's all there.
read the original papers then :P
you don't need lie groups to understand it.
you start with the klein-gorden equation (a linear complex field) and then add a new term to the Lagrangian (the mathematical thing you use to produce the equations of motion, classically you literally just do L = kinetic energy - potential energy) that is quartic rather than quadratic in the field. This allows a potential energy that looks like -r^2 + r^4 rather than just +r^2 (plot it on desmos or something) and the field "drops" to a lower potential state, from the plot you can see that the initial state r = 0 was symmetric when you rotated the system (similar to phase transformation that is mentioned, but this is a *global* symmetry so is not as profound) but the new state won't be. (note the +r^2 potential always has its ground state at r=0, a vacuum, and there is no other such state)
This is all well and good but when you combine the complex field with a gauge field (literally by adding a vector potential to L). you will see that you can make a gauge transformation that "compensates" for the broken symmetry *locally*. The result of all of this is that the complex field loses a degree of freedom , the gauge field gains one (photons, which are not the result of a broken symmetry have 2 polarisation states, but W bosons, for instance, have 3 spin states) and also its dispersion relationship changes from omega^2 = k^2 (massless particles) to omega^2 = k^2 + M^2 (massive particles). The mass it gains is related to the mass that the scalar field has, and the mass of say, the Higgs boson (a scalar field) can be predicted.
as a motivation for why symmetry is important, any foundational physicist worth their salt can, given the symmetry group of the standard model, derive every equation they could possibly want, the only other thing they need to do is measure constants (like the speed of light or plank's constant).
Actually, the midichlorians compose 80% of the dark energy. And 100% of the light, of course.
Of course. And "dark matter" is all the dust in the universe we don't see.
so some dark matter banged anakin's mom
@@mikejohnstonbob935 Energy. Dark energy! 😝
@@Meine.Postma just ii
Does your statement then mean that light (photons) are what make up dark (matter)? Or dark energy? I crave to grasp this.
Me: Pretend to understand while eating a poptart.
Matt: This is over your head stevie, go to bed.
This is so abstract the only word I understood was midichlorians.
Yeah me too. At least I understood one thing😂
So If the energy level of the universe sinks even more, we might se new forces pop up?
Interesting point
@FiniteAutomaton reddit moment
We measure the forces to zero kelvin and symmetry is only altered by formation of Bose-Einstein Condensate.
Yay! The advanced episodes are back. I am honestly learning so much from this channel as someone without a physics degree that loves quantum mechanics and GR.
Just gotta say that so that you know it's still super valuable. This is what sets this channel apart from pop-sci to me. I actually have to rewatch parts and think hard about how to imagine it all without it being impossible to parse for a lay person like a textbook this advanced might be.
I need to say thank you so much. This is by far the most concise and understandable explanation of this concept I have ever seen. I want to say that you guys are doing incredible work. I never thought I would see a day where pop science presentation meets the required level of depth on the subject matter to really explain the mathematical underpinnings without getting too far into the weeds.
I love how Matt paused after saying Spontaneous Symmetry Breaking at 10:42 as if in anticipation for something ;)
...all I understood was that double slit visualisation, everything else is as broken as SU(2) and U(1) symmetries below electroweak temperature...:'D
...still liked the episode...xD
It's simple: "adding mass to a photon means adding an extra term to the electromagnetic field stuff in the Schrodinger equation so that it would no longer be invariant to local phase shifts." /s
These amazing videos are packed with information. But he wields these complex terms so masterfully that I feel like we need a "slow mode" where there are pauses after every statement and little reference links everywhere for every term in the statement.
When I'm really motivated, I do this manually. But I'm not always up for it.
@@querywizard ...well this I can image to some small extent since I've never dealth with Schrodinger equations per se but I persume this "adding a mass term" can only be balanced by adding another "symmetrical" (hypothetical) term to satisfy the overall equation...
I've watched this episode like 10 times, and it's hard time for me to understand... I'll continue watching
Thank you guys, for constantly releasing videos which explain complicated topics easily
@PBS Space Time ; visual representation of a quantized oscillating object would be great, thank you :-)
omg I finally understand wtf U(1) and SU(2) mean!! Thank you 3rd year Complex Analysis and 4th year Singal Processing courses!
Whenever people tell me I'm getting insufferably arrogant at the hospital I watch one of these videos to feel stupid again and back off a bit from terrorizing my students, residents or nurses :)
Agreed Vladimir! I am of above average intelligence but the level of cutting edge of physics these geniuses in the subject work at is beyond me, I think even if I understood what different equation symbols stood for, by a long way!
@@sherlockholmeslives.1605 Guys,you are both dumb :)
I can actually feel your arrogance trough this comment.
Incredible
@@redhatlt
Lol! I may not be John von Neumann ( who is ) but I am happy.
@@redhatlt Most likely :D But teaching does that to you some times (makes you feel smarter than you really are), that's why I like to drag myself back to reality by looking at actually smart individuals discussing science so hardcore that sounds almost esoteric to me.
Grad school was a long time ago. This video was a really great refresher on the topic. Thanks PBSST.
When Matt mentioned midichlorians, my dog let out a little growly 'wuff' in his sleep.
The Force is not weak in that one.
Is your dog larger than seven feet? If so you may have accidentally picked up a Wookie. Surprisingly common mistake.
It’s like watching the history of science. Which is crazy because I could never stay awake in an actual history class as a kid, but this has my full attention.
“Actually, a visual representation would really help, here.”
Funny, that usually works. This time, spinny arrow and woobly lines didn’t help me. Will watch again...and again.
Yeah, this one is... particularly impenetrable.
I'm glad I'm not the only one.
Yeah, this one is bad. The whole video is.
The magnets all pick a direction to align to, up or down, left or right. The choice is arbitrary.
Before the choice was made, the system was homogeneous and random
Yeah this time I really don't understand it at all really. I'm going to rewatch a thousand times and get back
I understand the intention. It reminds me of understanding vectors in stress tensors
This video made it's way through my recommended playlist, and I have never been more thankful for it. So fascinating.
Please make a disclaimer like „Beware of unexpected jokes“ or so - my daughter jolted out of sleep from my laugh at 2:45 😂
I pretty much put this exact question in the comments of another spacetime video, so I'm so glad I saw this
Ok this has been the hardest one for me so far. I’m gonna have to come back to this one a few times
Had to look at 1/2 speed and still can't understand 1/4 of it
You have a way of explaining these things so casual fans of Cosmology and Physics like myself, feel as if we can at least follow the ideas that you explain.......we may not understand the complex mathematics behind it, but at least we kinda understand.......I hope this makes sense
"The sea was angry that day my friends, like an old man trying to send back soup in a deli."
i just watched that clip last night
th-cam.com/video/0u8KUgUqprw/w-d-xo.html
Hoochie mama!
This episode is such a hurculean task. Well done spacetime team! The spontaneous symmetry breaking illustration is the best analogy I have come across. Thank you!
2:43 ah makes sense .... wait what? no XD
This video could not have been more timely. I was just talking even today with Dr. Don Lincoln about this in his comments, trying to understand how a single force with (presumably) identical bosons could react differently than each other to changing temperatures and the Higgs field if there weren't already some other differing variable from the start that allowed them to react differently. He was very gracious in helping me try to understand this topic. Now I get to see at least two detailed videos from you on the subject. Perfect timing. Thanks so much!
Love Space timeeeeeee!
Being in the army myself...I thank you for your closing comment/analogy.
Would love to see more animation analogies of the U1 and SU2 symmetries of the electroweak field. I think the "clock" animation was getting close, but then you moved on and over my head.
The strongelectroweak force is fantastically named.
Just out of curiosity, could you provide references for this material for those wanting to read more about this. I've noticed with this and other episodes a lack of references except when citing specific publications.
I always wanted a pbs space-time vid on electroweak theory
You guys should go onto the Portal with Eric Weinstein. You have mentioned his work in the past and has a really interesting perspective on gauge theory.
they mentioned eric weinstein? where?
Thank you. Not enough people tackle this complex subject for us non-professional astrophysics enthusiasts. I really appreciate the thorough explanation using simplified analogies that even I can understand (maybe)
Wonder if Matt has an estimate on the year when we'll have the strong force added to the mix? 2021? 3021?
I think year 20,213,021 is more likely
42,069 more like
At 67 years old I finally understand this! Thank you
Wikipedia : "Matt O'Dowd was voted the sexiest astrophysicist of 2020"
One of the reasons why I don’t visit Wikipedia at all. No idea who might find this (supposedly) fact relevant.
@@Wonders_of_Reality cool story
@@evilotis01 Whatever you say.
@Khannea That was added to Wikipedia moments before you posted this... coincidence?
Great day with both a video from Don at Fermilab and Matt at PBS Space Time and the daily news from Anton at What Da Math.
I love learning about the Matrix.
This was such a info filled episode i has t rewind constantly. One of my fav vids this was so mind blowing. Thank you for such a high quality content!
For this episode, the 1/4 normal speed playback is still too fast.
Thank you very much. I did not know that I was waiting for this episode desparately. Thaks!
The midichlorian joke really got me. XD
I don’t understand like 95% of these videos and yet I still watch them.
“How does one force separate into multiple” > “How does one force become separated into several forces?” “Separate” is a transive verb; “multiple” should not be used where “several” / “numerous” / “many” is meant.
If we heart up the universe, until Electromagnetism and the Weak force merge and cool it down again, would the Weak force crystallize into different properties?
No, we can do this as the LHC. The Higgs field, responsible for the symmetry breaking, imposes a lowest energy configuration that always forces the same symmetry breaking. And good thing too, or we might trigger 'vacuum decay'.
Every time I think I'm beginning to understand a concept, along comes PBS Space Time.
Please make a video on entropic gravity....its very interesting..please unclutter it
Why do physicists talk so weird? “Symmetries” are said to exist when particles look random; symmetry is “broken” when they all look… symmetrical… argh!
Because that's what symmetry IS. Symmetry is broken not when particles look symmetrical but when they look IDENTICAL. You're used to lower symmetry where you can divide something like a cube up into a few limited symmetries rather than something like a sphere which has infinitely many symmetries.
It's more about the symmetry in the equations
if you're talking about the dipoles analogy, we should keep in mind that the symmetry in question was related to the DIRECTIONAL behaviour of the entire system. *when all of the magnets are jumbled up,* the SYSTEM will basically behave the same from every direction *(i.e. it will be symmetric).* by contrast, *when all of the magnets are aligned pointing upwards,* the UP and RIGHT directions will behave in noticeably different ways *(i.e. the system will be asymmetric).* I think a better term for this type of symmetry/asymmetry is "isotropy"/"anisotropy", check that out on Google.
Hope that clears it!
not gonna lie I listen to spacetime to fall asleep bcs that voice really do be soothing
"The most famous paradox in physics, first posed by Stephen Hawking fifty years ago, has been solved. In a landmark series of calculations, physicists have proved that black holes can shed information - if you jumped into one, you wouldn't be gone for good. This means that space-time is not the root level of reality, but an emergent structure from something deeper."
This was straight out of a newsletter I'm subscribed to. Would love to see Matt cover this in a future episode!
EDIT
Here's a direct link to the article www.quantamagazine.org/the-black-hole-information-paradox-comes-to-an-end-20201029/
Here's a link to the newsletter that I read this in futurecrunch.com/fc114/
Got a link to the article?
Quanta?
@@ThatCrazyKid0007 I do not, It was in an email newsletter I get. The newsletter is called Future Crunch and it covers news about science that doesn't often get picked up by larger news outlets.
@@djschuby04 Does the newsletter link to any papers on the subject? I'd love to read them.
@@ThatCrazyKid0007 Good news, I went back and found the link tot he article quoted in the newsletter. www.quantamagazine.org/the-black-hole-information-paradox-comes-to-an-end-20201029/
If you're interested in the newsletter itself, I found an online version of it here futurecrunch.com/fc114/
Forget where one theorist said black holes are not the same as the early universe where all 4 forces were somehow unified into a single force. Maybe I misheard what was really being said but it would seem to my limited understanding that it would be the case that inside a singularity some of the forces should be unified. It's also interesting to hear that they sort of pair up like with the electro-weak force shortly after the big bang. Great episode as usual and like some of the comments I understand a small fraction but always interesting.
Everything in the universe interacts to gain higher stability
What
Ever heard of entropy?
@@wasp89898989 Yeah I know about entropy I mean all of the matter and the forces that hold all the matter-energy together. They all seem to fight entropy.
How would you define stability?
Tell that to my girlfriends lmao got 'em
This might be my favorite of the entire series. Wonderfully explained!
11:50 "s(1) field" means U(1) field? Btw, since U(1) × SU(2) ≅ U(2), does the combined U(2) correspond to something meaningful?
EDIT: replaced equality by isomorphism.
It looks like that spot in the video has "SU(2) x (U)1", and I don't ever see U(2) or S(1) written.
The SU(2) x U(1) is the only way to write out the electroweak force, and the 'cross' operation is always required. I've never seen it written as, say, a single term.
Yes. He misspoke. I should massless U(1) field"
@@zzztopspin Is it really the Cartesian product? Then the isomorphism holds. Mathematically, SU(2) is isomorphic to U(2)/U(1). The latter can be interpreted as "U(2): anything unitary on a 2-vector base, /U(1): but ignore global phase shift". Now the isomorphism I gave is basically just the same in reverse, reconstructing U(2) from SU(2) and a global phase. Note that "phase" is to be read as mathematical explanation of the isomorphism, not something physical.
@@cmilkau I think you're interpreting this quite mathetmatically!
You probably know more about Lie algebra than I do, but I think it's important to remember that for physics, models of math (Gell-Mann matrices, Neother's theorem, etc) are often developed "so that" the empirical data can be explained.
If a unitary matrix in general has a determinant with magnitude 1 (complex or real) but a special unitary matrix has determine of 1 (real only) then these ideas would have a significantly different realization were they applied to the empirical world.
As for your question about if it's REALLY the cartesian product, I can't say I understand what you're asking! At the end of the day, I'm pretty sure the laws of physics at large govern the particle interactions in a clear cut way (I'm not saying deterministic), so that whatever math the particle physicists are using is probably the way to do it. Until we get a working theory of quantum gravity, that is!
I was not prepared for the can of worms I opened by clicking on this video lol intense stuff!
There's a really good chance you read the title as 'Election Week'.
I feel your anxiety too...!
i did
Finally you made me fully understand the concept of broken symmetry in the state of functions while conserving symmetry in the equations describing the latter's relations!
Symmetry is unstable whereas asymmetry has great stability by sorting things into fundamental relations.
You are right but for now mathematicians don't understand what this mean
Perfectly summarized my whole Electroweak Theory Course. Well done!
CENTER YOUR SHIRT
center your face
I'm from the future. Man kind will discover a 5th fundamental force in the universe. This will make way to a revolution in technology.
So... in layman terms for someone like me that needs them... When the electroweak field was unified it had the 4 massless bosoms, but when it "broke apart", breaking the symmetry of the field, it gained bosoms with mass?
Please someone tell me if my understanding is correct xD, I think the idea in itself is pretty fascinating and I want to properly understand it.
lol at massless bosoms
@@alib8396 This is why I'm asking for the layman explanation lol. Certainly this isn't my strong point but I find the idea really interesting.
The early universe had massive bosoms able to easily crush entire cities of men
Was that ,
“ gained Bosoms with Mass”,
Or was it supposed to read,
“Gained Bosoms and ASS” 😂
@@alib8396 I prefer massive bosoms, but W and Z are a bit too heavy. No wonder they don't live that long.
What a fantastic episode! More like this, please.
for me - this is aa prime example as to why many folks switch off listening. It just seems to be explained in a manner that could be simplified BUT of course, I am a dummy and did not request a vid on this subject to be put in "lay(z)wo/mens terms" Great Vid Doh! x
The crooked neck on the T-shirt bothers me more than it should.
Lol I thought it was just me.
It violates symmetry for sure !
The best physics channel on TH-cam
I understand all the words, by single. But when they are put together, I do not understand them! How magnificent
First? maybe?
First comment on your first comment commenting first comment on your first comment yes!
So what you’re telling me is that we’re a third the way to describing the universe in a single equation? Dope!