Chen Ning Yang’s early life in China

25:46physics distinguish left from right? Okay. like the Taj Mahal. The Taj Mahal does not distinguish left from right, right? I can flip the Taj Mahal in the mirror and it'll look exactly the same. If I if I put a giant mirror in front of the Taj Mahal, right? And then I I got somebody to to be in the garden of the Taj Mahal and he's looking one way and he's looking the other way. If the mirror is big enough and if he's not allowed to move around, he could not tell which one's the real Taj Mahal and which one's the fake Taj Mahal because the Taj Mahal is symmetric under inversion. >> Mhm. >> Right. >> Mhm. >> The question is can someone devise a

26:30physics experiment to show that we are not doing that? Okay. And this is something that I've borrowed from uh Fineman. He he proposed a thought experiment. He said suppose we're making a clock. Okay. We're making a clock that's normal. So, it's going to go, you know, clockwise. >> Yes. >> Okay. And now I make a clock with that that looks like my grandfather clock but in the mirror. >> Right. Okay. So, we're seeing we're seeing an image with two clocks. One that looks like a normal clock where the 12, the 3, the 6, the 9 look like normal numbers. >> Look like normal numbers. And the the the hand is going to go from the 12 to the Yeah. >> And then there's a second clock that's basically the inverse. >> It's the inverse. So So the 12 is

27:10flipped. The three is where the nine should be. The nine is where the three should be. And then the the hand goes from the 12 to the inverted three. >> The three to the left. It's rotating counterclockwise instead of clockwise >> instead of clockwise. Right. So he's like, can I can I make a clock like that? Okay. This was part of his Fineman lectures of physics which I'm a huge fan of. Um so how do we make such a clock? Well, we got to be really careful. Okay. >> Okay. for example, um even the screws, all of the screws are right-handed on our grandfather clocks, right? Because because in in America and I think across the world, right? Righty tighty, lefty loosey. I think that's just a standard

27:52all over the world now. But that's just a human convention. If I wanted to make a truly symmetric mirror image clock, I'd have to I'd have to call up my guy and have him make left-handed threads, which is like probably super hard because the thingy that's making the thread is itself right-handed. So, he'd have to make like custom equipment and all, he'd probably have to 3D print or something like that. But, if we did, let's say we let's say we went through all of that trouble. >> Yes. >> Okay. And we made a mirror image clock. >> Yes. >> Okay. >> Would that clock go exactly like the mirror image of my >> normal clock? >> Normal clock. And intuitively it seems

28:34yes right? >> I mean, without thinking too hard about it, >> without thinking too hard about it, honestly, like it it does seem yes. Honestly, like if um if if the gears are are tuned different, if the screws are tuned different, if everything is reversed, then of course the clock is going to go in reverse, right? And and that was the that was the way to do it for the longest time. And another um another way to think about this this parody symmetry, right? Um, we just talked about like the the clock is really a microcosm of like can I make an experiment that that goes one way or the other, right? That can tell the