StarTalk Radio - The Limits of Knowing with Elise Crull

Episode Date: November 4, 2025

How do you know what you know? Neil deGrasse Tyson and comedian Chuck Nice explore issues with quantum mechanics and objectivity, the history of physics, and how scientists ask questions on the edge of our understanding with philosopher of physics Elise Crull.NOTE: StarTalk+ Patrons can listen to this entire episode commercial-free here: https://startalkmedia.com/show/the-limits-of-knowing-with-elise-crull/Thanks to our Patrons Erik Nunez, Jim Zehr, Paulo Santos, Ken Cho, Dean Starbuck, Dan, Spacious, Bryce Larson, Robert Neal, Dawn C. Coles, Brent Williams, Mitchell Ransom, Kyle Kwartel, Salvatore Mammana, Benjamin Hunzeker, Peter O Halloran, Kristopher, Sean Josiah, Harry Summlar, Jeffrey Walker, Matt Coda, Beth Gallagher, Sherene Levert, Gabriel Castro, Paul Elliott, Robert watry, Nathan Baker, Eric Pozzobon, Adam Weldon, George Xenakis, Troy Kemp, Manjushree Tea, Juan Villegas, John Hart Project, Trygve Peterson, driven13, Malkoon Malkoonian, Dasha, Sam Hardy, miriam walter, Adam Goodspeed, Cindy Buccellato, Brandon Christian, Robert Loper, Liam, Viper, Kroij, Kevin Casey, Waverous, TJM8991, Timothy Jeffirs, Riley Thompson, Kushal Lal, Vivak Singh, K. Stalker Art, Jerel, Sophia Bogard, Len Smith, Kenneth, Daniel Coleman, Sharjeel Sahibzada, Christopher Tillman, Chuck Bell, Mal, Zakharius, Agata Tomaszewska, Mike Strauss, Jessica Baker, Robert Palmer, Mary Loyche, Jaime R Topp, Dan Macken, yazan al hajari, Johsua Skelly, Jamie, Tammi, Elizabeth White, Martin Assirati, Christine Peterson, Sooraj Poonawala, Rachel, Bryan Gaines, Guy Gore, Kelly Bragg, Surya Bakshi, J.J., Kevin Abeln, Doug Hemphill, Thomas Hogg, Greg Brunelle, CHO, Francis, and Bryan Olay for supporting us this week. Subscribe to SiriusXM Podcasts+ to listen to new episodes of StarTalk Radio ad-free and a whole week early.Start a free trial now on Apple Podcasts or by visiting siriusxm.com/podcastsplus. Hosted by Simplecast, an AdsWizz company. See pcm.adswizz.com for information about our collection and use of personal data for advertising.

Chuck, we got some more philosophy in the house. Yes, along with physics. Yes. Yeah. And they, they're the racist pieces of science. They belong together. Maybe physics and philosophy are entangled. Ooh.

More on that coming up. Welcome to StarTalk. Your place in the universe where science and pop culture collide. StarTalk begins right now. This is StarTalk. Neil deGrasse Tyson, you're a personal astrophysicist. Got with me, Chuck Knight, baby. Hey, hey, hey, Lord of Comedy.

You know, that sounds so... It does sound... But people call you Lord Nice. So why not run its course? Yeah, I am the... Because it sounds like I should say, I am the Lord of Comedy. Like, when people are like, Lord Nice,

that sounds kind of cool. You know what I mean? It sounds like a, like, you know, a term of endearment, more so than a title, the way they say it. But when I say it, it's just like, bow down before me. Bend the knee. Exactly. Will you bend the knee before the Lord of Comedy? Laugh not, I say, but capitulate.

We're revisiting the philosophy of physics. All right. Oh, right. Couldn't get enough the first time. It triggered a lot of interest. Okay. More than I expected or anticipated. And so...

A lot of people like philosophy. I think so. Did you bullshit today? Are you a plan on bullshitting? Well, we have an authentic philosopher in the house once again. At least crawl. At least, welcome back to Start Talk. Hey, everybody.

Have you bullshaded today yet? Yes, but not about philosophy. All right. All right, good answer. So let's remind people... Good answer. So you're associate. Professor of Philosophy at CUNY, City University of New York City College. My father was an administrator

there many moons ago. And your background is entirely in physics and philosophy. And I think there's some math in there too. Is that right? Was there? There's some history. I was one class away from getting a minor in math and I decided to take tap dance instead and no looking back, man. No, right. You got to move that body. Move that body. And so I love this. And you have a specialty in the history of quantum physics? The history and philosophy of quantum physics. Because there's a lot of room to philosophize there. Let me tell you.

Yes. Because, you know, I'm happy to just calculate, but somebody's thinking about why. And I'm glad that's not me. Somebody else is doing that. And so part of why we have you back on, I'm reminded by not only my producers, but the comment thread that I might have been, or was certainly, over-exuberant in my conversation with you. Way beyond what is normal.

Maybe I had a lot of thoughts and feelings, but you're the guest. That's hard to believe. No, no. Hard to believe that I... Look, I'm going to choose to understand it as... I mean, you guys have a great rapport. And what I do is intrinsically interesting.

So it gets people... We were all in it. We were in it. I was totally in it, but I wanted to... make sure because I'm an educator first and I want to make sure that people come into this conversation more thoroughly informed and so that they can become enlightened. I appreciate that, Neil. Thanks. So let's just, at the risk of sounding too pedantic, tell us what philosophy is. Let me be more precise. What is philosophy today compared with maybe 100 years ago, 200,

300 years ago, back to Aristotle and the famous sort of Greek philosophers. Right. So I hope I won't be repeating like the same stuff. I only have like three jokes and I think I did two of them last. We got other jokes coming here. We're good. We're good. Fresh. But that's maybe actually to the point. Some people have famously said that everything is just a footnote to Plato. Like it's all been done. All of the questions have been asked. but one of my favorite definitions of philosophy comes from philosopher of science Bosvin Frazen who also

That's a name? Van Frasen. Let me say, Basen Frasen. It sounds like a Hagenas ice cream. Well, you know what, Hagen, yeah. They made that up. The oomlots on the road. They're like, let us sound European

to sell our pican ice cream. They're made a jersey. Hagenoff is made in Jersey. But Fenthrassen is legit Dutch, which is like part of my heritage. Right. But he says that philosophy, it might be asking similar

questions, but every time you ask it, you're in a new context. New scientific context, new cultural context, new political context. And you're a different person asking it. And so there's a way that every time it's done, it's done anew. And you could be a different person from yourself having asked the question, even just a year or two earlier. I think one thing, we tend to look really hard for coherent thought across a person's lifetime. But why should we expect that? Well, we shouldn't. We shouldn't, right? People change their minds, and people who think hard are the ones who change their minds the most

because I think there's a bit of humility there. So, yeah, people, Aristotle defined metaphysics right after his book, physics. And for him, they were similar things. They're asking about what kinds of things we encounter in the world, what their behaviors are, what the patterns are that we see. And that's still a decent way of talking about what science is. it's explaining natural phenomena, like physical phenomena, right? Understanding their relationships and their behavior and their patterns and all this stuff.

So they started together as the professions became a bit more specified. And specialized. Specialized. Yeah, thank you. That's the word. They teased apart a little bit. But even into the early 1900s, you have all these really famous philosophers like Ernst Mach and Einstein and Pierre Du M. and Poincerey and Lorenz, who were... In Mach 1, Mark 2. Speed sound in a medium, yeah.

Absolutely. That same Mach. They were philosopher physicists. Go before them. Tell me coming through Newton and Hook, because they didn't call themselves physicists. They were natural philosophers. So take me through that era before you land in the 1800s.

Yeah, so again, Newton is building on Descartes. And Descartes was sort of the world. worldview that was building on Galileo and Kepler and Copernicus, but doing so in a way that wouldn't piss off the Catholic Church. So it's kind of a weird thing. But he wrote his, his magnum opus, his great work, is called the Principles of Philosophy. And Newton is criticizing that particular book when he writes the principles, the mathematical principles of natural philosophy. Wait, did I get the title right? I only just call it the Principia. So I've forgotten by the Yeah, yeah.

So what you're saying is Newton's famous work post dates Descartes's famous work. And he's, is he poking fun at the title and making it more of a product? He's trying to replace it. Replace it. Right. This is what they build on it. Yeah, so let me get the right. So Principia, Mathematica, Naturalis.

So in English, the mathematical principles of natural philosophy, that's the full title. In Principles of Philosophy, there's four books, Descartes, right? There's four books. The first one is setting up his philosophical worldview, his epistemology, which is theory of knowledge. How do we know anything in the first place? And then as metaphysics, like, what is there that exists for certain? And that is considered the first thing to do before book two, which is his physics. So in order to even get to the physics, you have to talk about when do we know something.

Which book has the, I think, therefore I am? That is in the meditations, which was published a few years before. before and 41. So he was already trying to go there. So book one of the principles is like a polished version of the meditations. And that's what starts, his philosophical worldview is the first book, and then his physics and his celestial mechanics, and then onwards. The Principia begins with definitions, which arguably, Poincere argues, are not helpful, and there's a way that that's true. and then there's the general scolium which means explanation and the general

scolium is where he gives his philosophical arguments for absolute space and absolute time and it is after that philosophical framework is established that he derives the three laws of motion and gravity would come in there and gravity is even later down the line right right but the first thing that they considered having to do was talking about how we know how you know what you know okay so and then do you know that you know what you know and is it important to know whether you know if you know you know or like i don't know i would say which is right did you give the right answer to that sure yeah so through that period the various folks who are trying to do physics are are fundamentally conjoined with philosophical foundations of why they're

thinking that way at all right okay so now fast forward or slow forward into the 1700s now take us to the 1800s scientific revolution time also actual revolution time for a variety of countries. Also... Merca. Yeah. Merca. Merca.

Merca and, of course, France. Liberté, fraternity. Liberty. That's right. Tobacco. Wait, I don't know how to say tobacco in France. Which is probably a good thing. Keep your stinking freedom fries.

Because we didn't like the idea of, a monarchy. That's our history. Rebelling against a monarchy. Anyway. I see what you did there. They're writing to each other in corresponding and setting up experiments. Boyle, Gassendi,

Newton, Leibniz, the people who were still philosopher of physicists in the 1700s and 1800s. They're also now working with Newton's Principia. And it's known pretty early on that the Principia doesn't answer everything. Like the law of gravity is action at a distance because it just says if I mean imagine on the universe with

nothing in it if two masses just popped into existence they would somehow immediately feel the force between the two right okay and there's no like time for the force of gravity to travel and say hey other planet this is what you should feel toward me um no it's instantaneous so people knew there were issues and one of the main people was emily de chatelle who wrote a book called the foundations of physics Right, so before, you know, maybe... When was that? I'm going to pick that up.

She's in the mid-1700s. Thank you for that. And she's experiencing a renaissance right now. For a long time, she was just known as, like, Voltaire's lover and mistress, and she hosted many salons. Z. This is how I feel about... I don't know.

I don't really want to say French things. Okay. Go ahead. I just, I want to make sure the timeline. is established here. So Newton's greatest work was done in the 1600s, spilling into the early 1700s. Voltaire comes around mid-1700s.

A little earlier, yeah. A little earlier. And so, and you're... And Duchatelais is the same time. Duchatelais, and so they're coincident in time. That's right. Yes. And she's, so she's hosting a lot of the intellectuals of the time

and, like, they're having an interesting conversation. But she's also in charge of teaching her kid, her son, physics. And she's disappointed with all the tests. textbooks, and she does what many people do. She writes her own. And the first thing she does... As one does. You do that with your kids, too. You see all the textbooks my kids are reading.

They're all wrong, because I wrote it. Do you put it as like, the byline is like, Lord of Comedy, comma, your father. Yeah. Anyway, she, before writing this book of foundations, which again starts with

a philosophical framework and goes from there. It starts with the principle of efficient reason and the law of non-contradiction and the rule of like sort of proper reason. Wait, law of, do they declaring that it's a law? It's an axiom. Okay. You have to start somewhere. Okay, so you've laid out some rules.

That's right. Rules and regulations. Yeah, you've got to bite the bullets somewhere. And what follows, derives within those constraints. Yes. Okay, gotcha. So, but she's also the one who translated the Principia into French. And I guess, like, current French physicists still read her transatlanticians.

But she didn't just translate the Latin into French. She filled in gaps. Like she wrote a thick commentary. Wow. And so it was her physics that has trained. You go pull out Newton and say, Newton. You need help. Here's what you left out.

Exactly. And so it was, people kind of got it. Like, he's not telling us everything. He's given us some parameters. But there's more work to be done if we want to really know why things work the way they do. And how many lady physicists existed at the time? hard to know because again this physics philosophy split isn't totally there so while there were just a few women maybe who were doing experiments of any kind i'm not sure i know any there are a lot of women doing philosophy corresponding with leibniz corresponding with hume um interacting like writing influencing libynitz's thought

interesting because i have a book which is leibniz's letters and and there's all manner of people that are on the other side of those letters. I'll take another look at them. Why, we all know Leibniz today. Just tell Chuck. Newton both developed calculus more or less at the same time, which I'm sure you woke up this morning saying, you know what, I'm dying to know who invented the calculus at the same time as Newton. But anyway, he thought that space was not a substance. It wasn't a thing.

It was just the relationships between stuff, a relational view. And so he objected to the idea of Newtonian absolute space, an absolute time. which is not really a stuff either, but it exists independent of matter. So it's like a thing in Newton's ontology. Like when he's listing the stuff that exists, space is there. Space is part of it.

But for Leibniz, it just is how we understand the difference between, the distance between matter. I'm confused here. There are two independent calculus and they both work. They, because that sounds weird. You know they're different because all the notation is different.

Yeah. And in physics, we retain a lot of Newton's notations. Okay. But in pure math, it's all leibnenses. You know, the integral signs and all these squiggly symbols. That's Leibniz, right? That's Leibniz. Yeah, it's all Leibnance.

And so Leibniz is a little more elegant than Newton's. Newton was like, let's get in and get the job done and get out kind of thing. All right. But I'm impressed that it would happen at this, basically at the same time and independently. I love calculus. I don't know why people give it such a bad rap. Well, I didn't. No, that's the thing I never thought I'd hear this morning.

When I woke up this morning, that's what I thought I'd never hear. Is that a bumper sticker on your car? I don't have a car. But if I did, that would be one of them for sure. All right. I'm Nicholas Costella, and I'm a proud supporter of Star Trek. Talk on Patreon. This is StarTalk with Neil deGrasse Tyson.

So now we got them. Now take us now into the 19th century. As technology gets better, we get, we're able to get. Industrial Revolution. Yes. And all these, like, we start moving from talking about forces and inertia and stuff where they can't fully analyze. And we, we start getting quantitative about.

conservation of energy and about like tweaking frog legs so we can understand how muscles work and psychology is coming into its own and sociology is coming like the different fields start to distinguish themselves and at the same time like universities are being built and growing and the different faculty at universities are getting set up um professional societies like the royal society and the para society of scientists um are growing so now you have communities growing up where people share their findings, and it's international, at least in the West, and so on.

It's a long and interesting story, which other people could probably give a better version of, but it's this increasing ability to quantize and specialize. The more we learn, the more there is to sort of... You know, I was thinking the other day, wouldn't it be great if we lived at the time of the Library of Alexander? Because, like, you could really have said,

I've read all the books in the world. Wow. Look at that. This is not possible. I think at least, I think that was true up until much later than that. Really? Rumor has it, I've heard told, that up through the 1500s, highly educated people could have claimed to have read everything that was ever written.

Well, that's because it was all handwritten. Real slow. Yeah, but some people like Aquinas, they had scribes. They had like a room full of monks writing for them. Just writing on their cheats. As they go into these communities, when does all of this lead to what we are? because none of this stuff is cross-pollinating today. Well, I wouldn't say none of it is.

I would say it's harder to do. Okay. And I'd say people are still asking these questions. But we've built, and we touched on this last time, we've built up our universities in a way that we actively discourage people from staying as general as possible. Okay. Liberal arts training is being kicked like a poor little puppy. And it's like such an important thing.

Right. And then when you get to graduate school, it's all over. It used to be like you would try to say general, even through your master's degree, you would take a little bit of, like you would learn everything. Are you saying it's important because it just kept you loose? Yeah. It kept you learning a bunch of other stuff. Other stuff, just the dimensions of life and of society. So, I mean, I'm going to jump all the way to the Cold War era.

And if people are interested, like there is good history on this. And one book in particular is The Physicists by Daniel Kevlas. It might be a little outdated by now, but it just talks about the history of physics in the U.S. and how it became so many different specializations and so on. But it was only after the Manhattan Project and after World War II that physics was properly considered a thing you could have as a career. It wasn't just something you learned as a young man at the university, or one of the few women,

but it was something you could have a, you could bring home the bacon, right, if you actually did physics. But at that point, physics is making bombs. That's right. They're important for national security. And no one is talking about philosophy at that point. So that's when the transition kind of happens. It becomes in the U.S. very pragmatic.

It's about the shut up and calculate mentality. And that really dominates through the Cold War era because there's its competition. But interestingly, in the 50s and 60s, James Kahn, who was the president of Harvard and a physicist and a chemist. I didn't remember that about that. Conant fought really hard for even his physics students to know the history and philosophy. He understood it is so important that he built it into Harvard's program that even if you were just, studying physics, it wouldn't be like writing down lab notes and doing calculations, you would also take a history and philosophy of science course. You're saying explicitly and implicitly

that coming out of the 19th century into the 20th, especially post-war, the field of physics has borders in a way where other ways of thinking can't get in. And you're saying that's to the detriment of physics, not to the detriment of other fields? How would you characterize that? I think it's to the detriment of any field, not just science, when those walls became impermeable.

I think walls are very good. Stop. Physics, as far as I can tell today, still suffers from this border problem. It makes sense because we get hyper-specialized because we know so much and building on so much,

we're asking just that many more questions. questions. And we have that much more technology to explore. So, I mean, the blossoming of many flowers is a good thing. So how do we use you? Well, maybe I don't want to be used. Okay. Okay. Sorry. Maybe I get to be exists in my own right because it's a beautiful and wonderful human endeavor. It came out wrong. I know what you mean. How do you help us? Okay. We help each other when we share ideas, when we have conversations like we're doing now. So, for instance, I was just talking about Mach, he was an important influence in Einstein. When Einstein wrote an obituary that everybody read for Mach, he said, one of the reasons I hold this person in such high esteem

as a physicist is because he kept asking about what is the proper goal of science, and that guided how he did science. But what is the proper goal of science is like a guiding principle? It is itself a philosophical principle, the same as we might say at a more intimate level in physics, like that choosing something that's parsimonious or beautiful or simple or whatever. There's no reason why the earth should, or why nature should give a damn about

those principles. About our aesthetics. Yeah. In fact, that nature is uniform at all is something you have to assume to even think science is worth doing in the first place. So there are a moment, you have to sort of buy into

certain untestable principles to consider are science worth doing? But the thing is, these are important things, but the concepts that we use too. So here's a good point. Space and time, the way that they're used in Newton, absolute space and absolute time, and whether or not they're important for his derivation of the three laws and his law of gravity and all this was an important question to ask, but Mach and Einstein and others at the end of the 19th century are clear that electrodynamics isn't going to work in absolute space and time.

Like, we, they knew things didn't fit together in the right way. And so they knew that one way to attack this to get to new physics was not just going to be to push around the equations, but to re-evaluate the basic concepts. And just to be fair to Newton, the whole electrodynamics, the, the physics that came to be understood that we call electrodynamics was not yet there for Newton, right? So he's working in his own, like you said, you work in your own world, you come up with what works later on we keep going yeah right so you know 19th late 19th century there's there's some there's tension between these different like really these pillars of physics like thermodynamics

system mechanics uh um and and and and i'm blanking sorry newtonian mechanics sorry classical mechanics um and it's Einstein Einstein says that it is not the physics in him as it were that allowed him to get to special relativity. It was that he said, what do we mean by this term simultaneous? And what do we mean when we're talking about space and time in a different, in different frames of reference? These are not questions physicists typically ask. Well, they were back, they were for the heroes of Einstein. And the class of people who were philosopher physicists was a, was a significant class of people.

At the time. A century ago. Yeah. That's right. So that it's not, that it wasn't for the last 50, 70-some years is, it's partly because of, like, there are political reasons for it, like the intellectuals who came to the U.S. from Germany during the wars, the way that they entered into the academy and began to teach physics and philosophy and think about this stuff. There are whole classes at the graduate level you could teach just about why the Vienna Circle, a particular philosophical school, which was all scientists, influence the way American philosophy and physics relate to one another. So it's a complex and interesting story.

But the end point is that if we take Einstein's word for it, going back and saying, are we really understanding this concept the way we should be? And this is what we're doing right now with gravity and trying to understand the quantized of gravity. And what we're doing right now with causality? Like, is there a quantum notion of causality? Or what does causality mean if space and time are even crazier than? in a relativistic framework.

So it's the reevaluation of these basic concepts. And that is a philosophically motivated question and asking, how do we know? We talked about this a bit last time. We're getting into regimes and physics where we're beyond what is empirically testable, at least for the foreseeable future. What then do you use,

what are your criteria for judging what is better? Or what is worth pursuing? Who do we fund? Where do we send our best graduate students? That is based on, who has the framework that you find the most compelling, whose view about the nature of space and time, how general relativity and quantum mechanics fit together.

So Brian Green's best-selling book, The Elegant Universe, just an all-famorce to him, that was not his original title. What was it? It was some more boring title. The publisher chose that, and that had a certain cachet with the public. Yeah, well. But it implies that we as scientists are in search of beauty,

a majesty and elegance in the universe as though it's waiting for us to discover it. It's like the universe is going to a cocktail party, darling. Presumably that's still okay to have some prior expectation for the universe to guide your next questions. Well, you shouldn't, like, it's important

and unavoidable as a guide, right? And we sort of talked about this framework, this worldview thing. Like, it's going to be there. But elevating those guidelines to the level of dogma, is when we get in trouble. Because then it affects who you hire into departments. Yeah, but it also affects what you consider the correct route to go.

It shapes your whole outlook on how you're going to approach everything. Right. You know, because you're like, well, we can't do that because we've already made up in our mind that this is the way it's got to go. Right. Or, I mean, you have to bet on a pony, right? I mean, if you're choosing whether you're going to pursue, like, canonical approaches to quantum gravity,

like loop quantum gravity versus covariant, like gauge theoretic like string theory like what brian green does i'm pretending i'm i don't know what you are talking about right now different approaches to solving a problem that we know exists there are like two basic this is this is a very crass way to put it forgive me but there are two big approaches to how to unite general relativity and quantum theory okay that's so far i'm with you go ahead is trying to build a theory of everything from the ground up string theory is kind of like that heard that go ahead okay uh the canonical approaches say we think quantum theory is is the most fundamental theory so we're going to try and

bring GR into that framework but that is something we that is something we can never empirically prove which is the right path to pursue look I said why I'm leaning that way yeah because no one has ever found a quantum physics prediction that was false it is so correct that at, oh my gosh, all right? But now you go to general relativity. It has known limits. It can't calculate the center of a black hole. It can't calculate the moment of the Big Bang.

It fails. If you can't calculate, you know, stuff about black holes, get out. No, no. Get out of physics. No, no, no. What I'm saying is, what I'm saying. People, I'm not talking about people. I'm talking about abstract entities.

You know, what I'm saying is if you already know, if you already know the limits of general relativity. Right. and you don't know the limits of quantum physics because you've never seen the limit. So you're, I'm thinking quantum is more badass. That probably goes in here and not the other way around.

Or, or of course, there could be a third entity. There could be a whole other than both. Yeah. So, and then there are some alternates to these approaches and they're considered a little bit fringe, but that means like it's hard to get good grad students to come and build your, like there are sociological factors too. But yeah, back to this notion of guiding principles.

Some of them have been, like, huge issues in the history of science. And I talked about space and time, but one of them is, like, objectivity. This idea that you ask the person on the street, what are the adjectives that describe science? And they're like, well, it has, like, a corner on truth, maybe. That science has, like, this corner on capital T truth. And there are some philosophers and scientists who continue to say things like this, but that's wildly problematic. Because that itself is a philosophical view. like how would you know as one single person even that that this is a special kind of truth now it's true that we have in empirical medium capital T like the slash is somewhere between okay quasi different size T's to begin the word true I'm going to say like you know 50 50 I don't know 20 proof that is weak sauce anyway um objectivity is also one of the things that's

supposed to make the knowledge and the truth that comes out of science a bit more untouchable. But objectivity is where the development of quantum mechanics gets you in trouble, because if you mean objectivity, be something like, when we do science, we can rope off this realm or this system, and we can poke it and prod it and study it and ask lots of questions, blow it with hot air, like see what comes out. And that's how you do fit. Like, you have to assume that there's some divide between your apparatuses that are measuring the thought. thing and the thing itself. This is a very old problem. I think it's even Aristotle. It's a measurement problem. It is. And it's an old one except in the sense that like Aristotle, I think, or somebody

said, like, if you want to study a bird, you can watch it flying around in his habitat and singing and all that, but you also like need to dissect it and look at it. But you can't have them both really, because if you've dissected the bird, you can't fly around anymore. Well, you don't want that happening, right? I thought that was fine. Feynman had a whole lecture on birds. Oh, then I really don't want to quote Feynman for a lot of reasons. But I like what you said where if you really want

to know what a bird is, you're going to have to open it up, cut it open, and then it's not the bird that you were studying. You just influenced the thing you were trying to understand. So we know how to sort of quotient out that engagement in classical theories to a point that we

can get very nice predictions of like football trajectories. Hence the idea of an objective truth. Right. But what happens in quantum mechanics is, and Boer and many others were realizing this already in 100 years ago, right in 1925 when it was first developed. A hundred years ago, we're in the centennial. That's right. It is the 100th anniversary of, like, my favorite.

We did a whole live show at Beacon Theater, celebrating the centennial. There's been a lot of celebrations. It's the international year of quantum. I'm just going to have, like, I'm going to have just sleep for all of 2026. But that's when wave mechanics was developed and new physics. Yeah, every year. And Hubble discovers that we're not the only galaxy. Wow. 1826.

There's always something to celebrate, right? 1926, right. There's a way when you're talking about quantum systems, like photons and electrons and these things, that you cannot avoid interacting with a system in a way that cannot be quotiented out. And so this is something that Einstein continued to look for. In particular, he thought that when a physical theory is completely, that means that you can give a mathematical state bijectively. That means there's a mathematical state that corresponds to some real system in the world. Did you just use the word bijectively?

Yeah, sorry about it. That's a word? It just means in both directions, like, that you can read from the math to the world or from the world to the math. Interesting. That's all. That there's a nice correspondence. Bijectively. Cool.

And I think somewhere else, Schrodinger says, yeah, Einstein, he likes a map with a little flag on it saying, And here's this system, and here's the system, right? And because in Frodinger's wave mechanics, you can't do that anymore. Because once a system, two subsystems have interacted quantum mechanically, and we pull them apart, and even after their interaction has ceased, Einstein says, you should, if you have a complete theory, you should be able to give a description mathematically of this guy over here that doesn't make reference to this guy over here.

Oh, that's... They're totally separable. That's kind of an issue, right? It is. It is. It's a little bit of an issue. Because entanglements can be understood as non-separability. Right.

In fact, it means after there's a quantum interaction and it's a new kind of thing that it's not mechanical, it's not thermal. Like, you don't even have to, like... It's a new thing. It's a new thing. And it's not just a new thing. It is, according Schrodinger, the thing that causes a departure between classical theories and quantum theories. when systems interact something weirdly different happens and you can no longer talk about the system the physics of one without considering the other or reference it that's right because wow that's wild it is wild i i love it okay but in all fairness to the objective truth people they're really i don't think they ever intended to include quantum systems in it you're talking about the macroscopic classical physical world right well can you have both I mean, can you just isolate the one for those circumstances and then have the question of the other, like philosophically and, I'll say physically?

Is that possible? It is, but even Einstein realized right away that quantum theory, if it's made it, if it's about the really small stuff, what is the big stuff made of? Well, yes. A bunch of the really small stuff. So there's a way that Schrodinger's description, mathematical description of the, the quantum stuff that means you can't separate out systems that's part of it should also apply at the macroscopic scale. So there becomes this whole issue of how do we explain, first of all, what this theory of small

stuff is doing, and then what happens when we get to this level? Because at this level doesn't look like you and I are entangled or anything like that, right? And we can give really good physics explanations now for why that's the case. but a lot of people mistakenly think that the Copenhagen interpretation

like Bohr and the others that were so intent on recovering objectivity so we could talk about quantum science made a sharp and fast distinction between the classical world and the quantum world like you have your measuring apparatus

and that is a classically sized thing so that we as humans It's a blunt instrument it's a blunt instrument that's right and then you have the quantum system that it's interacting with but in order for them to

interact. We have to talk about them in the same theory. However, aren't you allowed to say macroscopic objects, all these wave equations average out and to get to this classical result? But we know better than, it's not just averaging out. It's a process called quantum decoherence. Decoherence, sure. What is that please? Yeah, entanglement itself when you, well, it's the same problem about objectivity, but first of all, I just want to clearly, like, Bohr never, in his post, World War II, popul lectures and stuff, he sometimes talks about a classical world.

But he never, ever, there's no evidence that he believed there was some really separate realm. Like, it's a continuous situation. Thank you, Chuck. You're my friend. You're here for me. It's a continuous situation.

And he's like, okay, it's continuous, but we still have to, we are physicists, and we go into the lab and we look at a machine with a pointer. We have to be able to talk about that. So there's this pragmatic aspect of what he's saying.

This pragmatic object It is the failure of our being able to give this hard and fast divide between the object we're studying and the world around it that accounts for why we can't see things as quantum mechanical. It's because the things, the quantum systems we're looking at are in fact interacting with lots of other stuff. Einstein said God doesn't play dice with the universe, famously. Is there, are philosophers landing in a place where there is objectivity in quantum physics? It depends. Sorry, are they headed to a place? Is that a goal at all?

Well, if you mean objectivity as intersubjective agreement, like that we could go into each other's labs and agree on the results of what each other see, then clearly, yes, that's a part of what we want. Okay, of course, because otherwise there's no science without that. But I mean, I was at the 100th anniversary of quantum like Helgeland Conference. Helgeland is the little island in the North Sea where Heisenberg went to do a wee bit of cocaine and to finish how to do... Where do you get all the scoop on people? And I'm going to tell you some. I read their letters. Oh, the letter? Because it's not in their books. Yeah. Right. Let me just say this one I'm saying I make a correction there.

There is no such thing as a wee bit of cocaine. You can't do a quantum. So they got a bunch of physicists together. They had a panel session with a number, like four recent Nobel laureates in physics. And they're talking about the bell experiments which test entanglement and show that they're not communicating faster than the speed of light or anything like that. And it's something we call non-locality, which I would characterize as like the signature that, like the signature that we can measure the signature of entanglement. That's a poetic way of putting it.

These physicists won the Nobel Prize for designing experiments to test this and they could not agree on stage what non-locality meant about the world. Okay, so tell us what non-locality means. I'm not going to be able to supply and answer if two bell no,

Lord, I think it's just indicating that systems are quantum interaction is a kind of interaction we have never studied before in physics. Okay, so non-locality means these two particles that are entangled cannot be described independently of each other. So this is not local. It is connected. So it's not just that, because we could do that classically, right? If Chuck always wore different color socks, and I saw just one of his

socks on a given morning, it's like he's wearing a brown sock. I could know something without measuring his other sock, I would know that it would be non-brown. Exactly. Right? Okay. That's purely classical, not interesting. What makes it very non-classical is the idea that once these systems have, for all purposes we believe, stopped interacting. They're not communicating. There's no information going between them.

Nothing is exchanged. While they're in flight, we can ever at our, over at our measuring device for this guy, set it to measure some quantity or other. Spin with respect to some angle or something. measuring a quantum property of that entity. Yeah, some property of that entity. And the other one will know what it is that was measured and what state the other thing is.

So therefore it's not local. So it's not just that there's a correlation between the two. We have lots of classical correlations that we love. But it's that these correlations cannot be explained. The correlations exceed like just statistical randomness. Can you one day? But yet they can't be talking to each other. Can you one day?

That's what, there you go. They can't be communicating unless you want to ditch the speed of light. And most people are happy to say, did you wait? Like Chuck woke up this morning and said, I'm happy with the speed of light being what it is. At least, why not go full Monty here and say the two particles are connected via wormhole? So there are, we could give alternate explanations. But wormholes are way, they would have other.

effect. Wouldn't like they would have other... It's a entanglement wormhole. I mean, who knows? With a wormhole, you're not moving fast from the speed of light. You're just cutting through the space time continuum, instantaneously. I think it would be hard because entanglement, non-locality

is so ubiquitous. I think it would be it's not impossible, of course, and this is where like your guiding principles come in, but to just think that wormholes occur whenever it. But also, entanglement is can happen with respect to different properties of a thing

and it can change over time and it can be multiple systems depending on those so it is a really complicated relationship okay so now I measure one of the particles the other one manifests itself with the complementary properties and now I just de they're no longer coherent

yeah they're no longer entangled after you've done that measurement now they're local particles yeah in fact the measurement that you do the physics that we're doing is all local over there, right? But yet there's this thing we can't explain. All right, so my question to you is, is it the physicist

who's taken a little bit of philosophy that'll help them address all of these questions? Or is it the philosopher who's taken a little bit of physics who might get us out of these conundrums? I think we could use all the help we can grow. Let's all talk to one another. Yeah, like, who cares where it comes from? All hands on deck. All hands on deck.

I mean, so there's a... I'm sorry, because I'm still, you guys, We're moving very quick, and I'm the guy sitting here without any Ph.D. of anything, okay? So, there's, you don't have a PhD? Yeah. Somebody give this man an honorary doctor. I know, yeah. Who invited you?

Okay. So, based on what you just said, because I'm running it back in my head, is it the actual measurement at the time of measurement that makes the entanglement? or is there ever a decoupling at all? Or are they measured and then tangled and they're forever entangled? All of those things can be true. So we've developed ways to do weak measurements, which sort of lightly tap in the system. It's like in a ways you can gather some information

but not fully decouple it. And again, the degree matters. Like there are some limits on how entangled certain numbers of states can be with respect to some like so it's this is why we can use entanglement as a resource and it's like to help us explore different like topologies and in in in in holography which is you know ADS like and it relates to conformal field theories which I don't really know about and I want to figure out like a guy got a front of but they're using entanglement as a way to probe unmeasurable stuff okay we got to land this plane so the way I want to land the plane to get you super cool man I'm telling

It's very cool, yeah. It's unbelievable. Yeah. Get you to tell me what the future of this creative thinking will bring to quantum physics. Will it, is the goal state, to turn quantum physics into something as intuitive as classical physics. With a pathways of understanding, that's obvious that it should do that. This particle pops in and out of existence. Of course.

or will it just remain statistically mysterious and like Einstein said God does not play dice with the unit, but maybe God does. I'm my answer's done. Maybe God is a gambler. Just deal with it. Yeah. People have a different

people have different questions about that. So here's another, like if you're a physicist who does quantum theory or you're an experimental quantum physicist and you believe that the universe is not statistical, then you're going to design tests that try to get beyond that. But if you think the world is ultimately indeterministic, then at some point you're going to move on. Yeah. But I've already said, I think, this is just my guessing, again, from conversations I have

with practicing physicists, but thinking about quantum mechanics is never going to be intuitive the way classical mechanics is. Because we as evolved creatures the way we are started doing science in terms of position and with things we could see and measure and apples and arrows. We didn't evolve in a quantum state. No, in fact, you could very easily argue that knowing quantum theory is evolutionarily maladaptive because it's a bunch of nerds like myself sitting around

doing problem sets and here comes the saber-tooth tiger. So it's good for us species. Oh, you would be summarily removed from the gene pool. Yeah, I think so. It's a classical... It's a good thing for physicists. A classical understanding of the saber-toothed tiger wins every time. Yes.

If that's the only thing that the audience takes away, that's a good one. For those who live near saber-tooth tigers. They're extinct, right? Yeah. Biology is not my area of expertise. But I got news for you. The regular tigers. They don't eat you, too.

We'll stick with the regular tigers. They're good enough. We have sharks and things. They'll eat you too. Plus they're on the list for becoming de-extincted. the saber-toothed tiger. Okay. The fact that we can do that now. So cool. So there's a way that quantum is never going to be intuitive to us the way it is. But that's why engaging with these philosophical questions, we're going back and asking,

what are we doing when we do this test? When we do tests, are there loopholes in the logic of how we're doing this? Are there things we can be testing we haven't thought of yet? Are we using the word causality or space or time or background? Like, are we using these in a consistent way when we set up our experiments? Are we testing our assumptions? Like these conversations as well, we're so wedded to the classical picture of things that understanding that... It's not our fault. We evolved that way. It's very natural, right?

But it also means that we have to do a lot of work to continue unmooring ourselves from that perspective. I love it. Unmoring. So, so, okay, all hands on deck. Keep doing it. No, it makes sense. I mean, it's like you're, really it's kind of a, you know, and awesome. that happens.

That's another really good word. You know, because of the practice, the practice itself. Yeah. And then what you have to do now is in order that we can become more elastic, this is where the philosophy comes in to help change the thinking altogether so that we can go in a different direction. Right. And in the ideal world, there would be more cross-pollination, but also the way we train

physicists would be, I mean, because there are a lot, there's lots of philosophy that doesn't really talk about physics or take physics as its input the way philosophy of physics does, you know, ethics, epistemology, social political philosophy. These are important areas of philosophy that leave physical philosophy, religious philosophy, even economic philosophy. Philosophy of law. Yeah, yeah, yeah. Philosophy of the emotions. Like, these things can stay pretty far as. Space law. That's another frontier where they need some philosophers. I really, every time I meet a lawyer, I ask if they're a maritime lawyer, because they're going to be the first one. who, like, develop, they're going to be the ones Yeah, a good friend of... Has your satellite crashed into another satellite? That's not the cat! No, listen.

We can get you what you deserve. That's not what we're talking about by space law. Actually, it's not far away. I mean, there's a nearest trajectory between Earth and the Moon. Who's going to please... Is there going to be toll booths along that? Like, who's going to police?

My brother is co-founder of Carmen Plus, which is an asteroid mining startup. And they have a lawyer... Everyone's brother would be. Of course. And what they do is super cool. But what they're, but they have to think about these questions.

Like how do we, do we tax stuff that you mine from asteroids? Who owns this stuff? These are really important questions. So yes. But that physics training in the U.S. would involve some pausing and stepping back and looking at the history of the field

and asking philosophical questions. Is there a country that's doing that now? I think there are. I think there are. I, you know, I don't know at the university level, but when this was what was really exciting at Helgeland is I met a lot of young, like, early career folks in physics at these great labs all over Europe in China and in South America and some in the U.S. Although, to be honest, most of the labs in Europe are hoping to get some of our best scientists who are leaving. This is a real thing. Phone calls have been made, yes.

We're losing some of our top scholars. I wonder what's going on with that. But the young generation wants to study this stuff. They are interested in knowing these things because they understand how wet it is to the edge of physics that they're asking. So I think if enough people ask for it,

like vote with your dollar, right? Ask to be taught these questions when you're learning physics. And it will... A reminder that when you're young, you're a little more irreverent in your thoughts anyway. Yeah.

You're a little bit less... Like, you haven't built a whole career in a particular groove. So you can sort of... hop over. All right. Yeah, yeah. Well, at least, thanks for coming back.

Fascinating. Thanks for inviting me. I have a good time conversing with you on. Okay, and you're just up the street. I mean, you're right up there. City College is up in 138th Street. Right up there in Manhattan. A few miles north of here.

Can I ask one last question, Neil? I guess so, sure. I know you've said, this is personal, and so it doesn't have to go on the air if you don't want, but I know you've said a number of things about philosophy of science and philosophy in general in the past. But you're, like, you seem really genuinely curious about these things.

What's that about? I would say my comments on philosophy have been caricatured. Okay. And so I can be very explicit. There. Okay. I have yet to see someone who has earned

a PhD in a philosophy department in the 20th century contribute materially to our understanding of the physical sciences. Oh. It's been done already, yeah. But also, I mean. So who was saying, is the philosopher saying that, or is the physicist saying that?

The physicists have said that. Okay, so what's the single best example? Oh, um. Single best. Adam's got one. You're here. No. I'm calling on my ask a friend.

Okay. Ask you. Phone friend. I get a phone of friend. Phone a friend. So Abner Shimony was a physicist at Boston. Was a physicist? So his.

He's formally trained as a philosopher. Abner Shimoni has formal training in physics and in philosophy. But his Ph.D. is in what? Both. What? Well, there you go. We has two PhDs. But that's less the point.

The point is when you read these papers, the reasoning is philosophical, logical reasoning. Just don't get me wrong. I'm not saying that physics can't be helped by philosophical thinking. I don't know any good physicist who isn't thinking on some level philosophically about what they do. Great. And in the field of astrophysics as well. Good.

There's always a philosophical dimension. So the precision of my comment about philosophy has just been, what is the value to the physical scientist of someone who's spent their entire career academic training in philosophy? And I compare modern times to how frequent those contributions

came a century ago. And so if this is the, this is one guy, maybe there's more examples, but I'm just contrasting the utility relative to what role philosophers played back in the day. So first of all, yeah. So I said this last time, and it's worth repeating, saying that something is only important in as much as it contributes to science is a really dangerous point of view. Yeah. That said, it's still contributed to science, but it is worth doing in its own right.

But this, it is worth doing philosophy of science in its own right. I'm not denying that either. And I don't think it's also very always quantitative. I don't think there's a hard and fast line between these disciplines, which is why they were for thousands of years the same pursuit and why in some arenas we're seeing them coming back. I never said it wasn't worth pursuing. You've just been shimonied.

Shimoni. No, I never said it. I didn't say it wasn't useful. as it's in its own field. I'm just talking about how useful it used to be to physics to have a philosopher in the room. And that utility is now absorbed by physicists who are thinking philosophically

rather than a person whose entire training is in the philosophical world. Have these physicists themselves been trained in philosophy? They might have, but not as if... Not very much. Have they taken philosophy classes? Probably, yes. I actually maybe an intro philosophy class is undergrad, but I'm willing to bet most of them have not taken a philosophy of science course.

Probably most, but some have, sure. So there's a difference between like stepping back and thinking, which everybody should do if they're good practitioners of their, but there's just different ways of viewing the world that, again, I do have training in science and good philosophers of science will have some engagement with the science itself and the people who are practicing it now. And when we have conversation, it's interesting. It's interesting, and we learn things. It is a dialectic. So it may be impossible for those fields to merge again, and maybe that's not the end game. But to have a conversation is very fruitful, because I change the way I think about how physics is being done right now. I learn about what they consider the interesting questions, how much progress we've made.

It is all very interesting. So then we should promote more of that. I've been like four or five different academic institutions. At no time is the philosophy department having lunch with the chemist, the physicist, and there lies the problem. That's what she's saying. That's the problem. And then when we do talk to each other, I think, yes, you're going to find people

like, they don't have anything to do with each other. And you're going to find philosophers of science who are saying a bunch of stuff that has no connection to real science at all. And it could still be interesting. But if you're doing philosophy of physics in a way where you're trying to engage, you have to actually engage. Maybe what I'm observing is the imperative. fact that

this doesn't happen. Yeah. The philosophy departments don't have lunch with the physicists. We should. And so I'm observing that reality and commenting on it. Yeah. So that's all it is. Yeah, that's fair. Because I've long for the day.

Now that you have observed it, that reality is now entangled for all. So now it has to happen. Actually, it's the observing that would destroy the entanglement. Oh, that's right. They can't do it anymore. I'm so sorry. This is the comedic inversion of that. At least, let me get you, take us out with Einstein's comment on philosophy. Do you remember it?

Okay? He probably had several. He made many. Which one are you hoping for the history and philosophy? No, no, it's not that deep. This was very, this is very off the cuff of him. Sometimes when I think about philosophy, I feel like I'm chewing on something that's not in my mouth. Where's my book?

Hand me my book. I want to read the quote. One quote from Einstein, that's a legit quote. Thanks for reminding me that the Einstein paradox. This is an academic... It's an academic text. It does presume some acquaintance with quantum physics. But just, you know, a scooch.

Wow. The Einstein paradox, the debate of non-locality and incompleteness in 1935. The originators of the theory... This is very... This is very... that's like a title of a thesis right there. This is intricate work. It is intense work. So this is Einstein...

writing in June to Schrodinger. I'm trying to figure out what on earth quantum mechanics means. Dear Schrodinger, I was very pleased about your detailed letter dealing with our little paper. The actual difficulty lies in the fact that physics is a kind of metaphysics. Physics describes reality, he puts the scare quotes in, but we do not know what reality is. We know it only through our physical description. They are wedded together.

Wow. That's pretty cool. He called him Strzinger, not Erwin? Didn't I say Dear Irwin? No, you said, dear Schrodinger. No, no. Just like buddies. Like, if you're playing a sport, you don't say,

Hello there, Terrence. I have, in fact, played sports in my life, despite what that sounded like. Okay, there it is. All right, we've got to wrap this. Well, thanks for this second visit. You know what any time. To my office here at the Hayden Planetarium.

It's great stuff. It's good to be back with you guys. Yeah. This has been another installment of StarTalk. let's call out the Physics of Philosophy Edition Chuck Always a pleasure

You are Lord of Comedy Yes Neil before me Until next time I'm Neil degrass Tyson Keep looking up Thank you.