Why symmetry remains the compass of physics

1:10:05or it could go backwards. Right? If my cobalt 60 is oriented in one direction, the electron could spit out forward or backwards. Yes. Now, they're always going to be the the spin is always going to be oriented in the same direction as the cobalt 60 because of conservation of angular momentum, right? Be like the the Cobalt 60 has an initial angular momentum that is away from me. >> Yes. >> So, the electron that's going out is always going to have an angular momentum that's away from me. The question is the direction of motion. Is it gonna be away from me or towards me? >> Those are the two scenarios, right?

1:10:46>> And in a world that doesn't care about left or right-handedness, both of those directions should be exactly >> equally probable. Got >> right. I should have an equal number of electrons coming from the front as from the back because I've oriented the cobalt in in in the front direction, let's say. But if the world doesn't care, then the electrons should come out from the front and from the back equally likely because they're all oriented. I mean, sure, the electrons are all right-handed orientation, but if the universe doesn't care about right-handed orientation, then the front and the back should be equally likely. That is not what she saw. >> So, okay, got it.

1:11:27>> All of the electrons came out from the back. >> Interesting. >> All of the electrons came out from the back. So, the universe does care. >> The universe does care. >> That's so funny because after all of that, >> after all that, >> after all that. >> Yeah, [laughter] >> it does actually matter. >> It does actually matter. Left and right-handedness is something that the universe does care about. This is schematic. You've got the magnetic field in one direction. The cobalt 60 is oriented in that one direction. There's two possibilities. The electrons going out front and going out back. But the electrons only come out the back because they're constrained by which way they can spin. >> Okay? >> Right? So, so if I could spin this way,

1:12:09I can only come out this way >> in some mirror world. Let's say that I have an anti- cobalt made out of anti-rotons and anti-neutrons and the thing that's coming out is a posetron instead of a electron. Then it would come out the front. M this goes back to the same analogy of of like when we're looking at the mirror it's the same direction. Um it it's it's okay. So let me take a step back. >> It's crazy dude. >> So the experiment proved that there's not symmetry in the mirror image. >> No, the mirror image physics is different >> is different >> from our image. >> From our image.

1:12:49>> Yeah. Let me let me let me get a little bit more specific. Okay. >> Okay. Let me get a little bit more. Um, yeah, let me let let me let me say it this way. Okay, I've got my cobalt nucleus, right? My cobalt nucleus is >> in this direction. It's spinning clockwise. >> Yes. >> Right. In my mirror world, the cobalt nucleus is also spinning clockwise. >> Yes. >> Yes. >> Okay. So in my world, the cobalt nucleus is spinning clockwise, but the electrons are shooting out towards me. >> Yes. >> Right. >> Yes. >> In the mirror world, if everything was

1:13:30exactly symmetric, the electrons shoot should be shooting towards the mirror Krishna. >> Not right. Not towards >> it'd be coming towards the real Krishna. >> Right. Right. Yeah. Yeah. Yeah. >> The physics is different. You see what I'm saying? in the mirror. >> In the mirror world, the electrons should be going that way, but they'd be coming back this way. >> Back this way. >> So, there is not there is not this um conservation of par. >> There's not a conservation of par when it comes to beta decay. >> When it comes to the weak nuclear force, >> when it comes to the weak nuclear force >> specifically. So, there is it's one of

1:14:10those things where there is an exception. um specific to not to gravity, not to the strong nuclear force, >> not to the not to the um electromagnetism either. >> Not to electromagnetism either. But the weak the tiny >> the tiny the weakling >> Yeah. The weak nuclear force >> does not have this conservation law that is true everywhere else, which is fascinating. >> That's crazy. >> No, that is crazy. >> That is Dude, it's like cuz now we can DM our aliens. >> Right. Right. We can DM our alien be like, "Hey, prepare some cobalt 60," [laughter] >> right? And then and then and then orient