Physics, unlike chemistry, can actually distinguish left-handed from right-handed without relying on an arbitrary convention. Using Richard Feynman's thought experiment about explaining left versus right to an alien over the phone, the hosts explain why chemical tricks like growing crystals or testing sugar rotation fail, since an alien's biochemistry could be built on the opposite handedness. They then connect this to Chen Ning-Yang's theoretical work and C.S. Wu's experimental proof of parity violation in beta decay, where the electron emitted during neutron decay shows a directional preference tied to spin, demonstrating that physics does have a built-in way to define handedness that chemistry lacks.
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The hosts reference Feynman's version of the alien-phone-call problem as the way to see why chemical signatures like crystal shape or light rotation cannot fix an absolute left versus right.
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C.S. Wu performed the experiment that proved parity violation in beta decay but did not receive a Nobel Prize for it, which the hosts note was controversial.
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An on-screen clarification notes that in Wu's beta decay experiment, electrons are preferentially emitted opposite to nuclear spin rather than always in one fixed direction, and antineutrinos are also emitted in the process.
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39:00And before we get to that, let's do some housekeeping because we haven't done that in a while and I think we deserve it. A quick opportunity to shill, a quick pause. So you can find all of the papers that we talk about and go through on the show at our website, ffppod.com. We do short clips and little bite-sized takes of some of the best science that we talk about on our socials at FFPpod. And one of the best ways to help this show get seen by more people, the like, share, or comment, share it with somebody you think would find it interesting, Five Star on Spotify or any of the podcast networks really helps us get the best science show on the planet out to more people.
39:44And I just want to note, I was so excited when I saw the announcement this morning because one of the, and you mentioned this earlier, one of the biggest unlock episodes for me in terms of my mental framework around the sciences was when we talked about due to the unfortunate passing of Chen Nanyang at the end of last year, we have an episode, "The Man Who Unlocked Symmetry." If any of these concepts are super interesting to you and you want to know more, whether it's about parody violation or the birth of Yang Mills, that episode is an absolute banger. Yeah, it really is. And the one thing that I want to mention about that episode and its distinction with this one is
40:28the fact that physics does care about the mirror world. Yes. Right? In chemistry, as we said, you can create a Petri dish of both left-handed and right-handed stuff. And you might be thinking, well, you know, does everything in physics care about left-handed, right-handed or not? Like in chemistry, it clearly doesn't. In physics, in fact, there is a way to tell between left-handed and right-handed stuff. And we do this great analysis that Richard Feynman actually originally did, where he talked about, you know, if we were to call up an alien, how would we tell him left versus right hands, right? We can't use chemistry. We can't be like grow some glucose and then make it go through light and see which way the light
41:11turns because the glucose on earth, sure, it's turning to the right-hand side because glucose is right-handed here on earth. But the alien is gonna grow crystals and then like Louis Pasteur, he's gonna be like, well, there's two different types of crystals. And like this type of crystal is going left-hand, this type of crystal is going right-hand. Or in the worst case scenario, the alien has a left-handed version of life, right? He's still somehow eating glucose, but his version of glucose is all left-handed. And so he goes the other way and he thinks his left is our right. Chemistry cannot make that distinction. Physics on the other hand can. Chen Ning-yang was one of the key people who understood that.
41:51And CS Wu, the very famous Chinese physicist, she did not win the Nobel Prize very controversially, but she proved that that was in fact a fact of the universe, that parity violation exists in beta decay where neutrons spit out a proton and an electron, but the electron only spins in one direction versus the other. It's an incredible episode. It's actually one of my favorites as well. It's so good and beta decay coming up again. Yeah, we talked about beta decay yesterday.
Nobel PrizeChemistryBiochemistryChemical origin of lifeSynthetic Biology