The beauty of theory vs. experiment

1:18:17universe >> which is a big >> that's a big deal. That's a big deal because parody had that pedestal. >> Yeah. >> That was the same as translation in space translation in time of energy. Like imagine if someone rolled up like oh the conservation of energy actually is not a thing. It's not a thing. Like >> yes [laughter] that would BE LIKE YO WHAT ARE YOU TALKING ABOUT? >> WHAT ARE YOU TALKING ABOUT? >> IT would be a huge it would be a huge deal. Yeah. it spread like wildfire across across the world, you know, through the telegrams. Um, so it's really unfortunate that she didn't win the Nobel Prize. >> Um, and that is what won Young the Nobel Prize, >> right? >> Okay. What he's most known for actually

1:18:58nowadays, and I'm just going to go through this real quick because I don't have the expertise yet. I'm I'm reading this textbook called um, Physics from Symmetry. Mhm. >> Um I'll put the I'll put the the author. I I forget the author, but there's this it's an amazing textbook, physics from symmetry, and it's and it's going through talking about um how to build up physics >> from an axiomatic perspective of like what if the symmetries are axioms? How do we build up a universe >> based on those >> based on those? And that sort of way of thinking about stuff came from something called Young Mills theory. Okay, this is Young His Tour to Force, the reason why

1:19:41he's considered the great, right? Like the this parody stuff is cute. >> Yeah. >> Okay. >> The real reason why he's considered like one of the greatests of the 20th century is because of the Yang Mills theory. So Yang's been obsessed with symmetry for the very longest time, right? And um while started working on these, Herman Wild started working on symmetries in physics. he piggybacked off of not to and he renamed these symmetries something called gauge symmetries after like the gauges of um railroad tracks and how they're all like you know standardized. I literally remember being in Terrace at Princeton and hearing any number of you guys talk. Someone was

1:20:22constantly on about gauge theory uh constantly. Dude, gauge theory once once I mean I'm just getting into it with this textbook and it's it's like intoxicating how beautiful it is. Like imagine it's completely inverting the logic of how you want to study the universe, >> right? because it's saying like it's postulating a symmetry to derive a forceh >> right it's saying we can take as an axiom >> the fact that these symmetries exist and then ask what is the kind of universe that we would live in >> if these symmetries exist

1:21:02>> right it's almost dude it's like >> dare I say a little religious [laughter] in some sense it's it's it's insane right so so here here's what I here's here's the Only thing that I'm going to say about like sort of how the math that works um >> well we talked about how the wave function right it's a complex number it's everywhere in space if I change the phase of that wave function that complex number and the only thing I care about in terms of observables is the magnitude of that complex number then it doesn't matter how how much I change the phase as long as I change the phase everywhere the observable is going to be the same that gives me conservation of charge okay >> um we can ask what if I want to change the phase differently everywhere

1:21:43everywhere in space and time. Yes. >> Okay. So instead of a global symmetry which is which is where I change the phase everywhere, I change the phase locally. Is there a local symmetry that I can do? And that's where we what what you can do is you can say okay if I change the local phase everywhere then I