The Problem With Quantum Theory | Tim Maudlin

so I'm Tim maudlin I'm a professor of philosophy at New York University [Music] and you've written a lot or thought a lot about quantum mechanics and a lot of people see it as the most accurate is like giving the most accurate predictions compared to other scientific theories at the moment but your latest what some of your latest work looks at how quantum theory is actually a misnomer would you be able to explain this to us right so there's no doubt and no one's going to dispute that there's a mathematical formalism that we know how to derive predictions from and those predictions can be accurate to 14 decimal places but what a theory is what a physical theory is is more than just a mathematical formalism with some rules it should specify a physical ontology which means tell me what exists in the physical world are there particles are there fields is there space-time and tell me about those things and then specify some laws about how they behave that tell me how they behave through time and the problem is that there is standard quantum what's taught as quantum theory isn't isn't a theory in that sense it's just the formalism and then what people call interpreting quantum theory which sounds like a funny thing to do because you'd say well I have a theory what's an interpretation what's called interpreting quantum theory is really the development of precise physical theories that make the same predictions or nearly the same predictions that you get out of this standard mathematical recipe and so this to me clears up a kind of funny question because often they say Oh a physicist would say well I've got quantum theory what do I need an interpretation for what the philosophers do the interpreting whatever that is and that's because the language is misleading them no you don't have a theory you have a predictive recipe and what we want as a physicist what you should want is a theory is something that makes clear statements about what the world is so does that mean that actually quantum mechanics is a lot stronger in its predictions than the kind of public broad audience thinks what does it mean that they're not there yet and they still need to work towards having the stages of the theory well there are different approaches that people have been working on this is a very minority group who work in foundations of physics so there's a whole approach that goes back actually to 1925 and Louis debroglie that's called the pilot wave theory there's another approach that are called objective collapse theories and Roger Penrose is working on those and some other physicists Giancarlo Girardi particularly it worked on versions of objective collapse theories and these are just different theories and they all make the same predictions insofar as they have been tested so far so we can't go to into a lab and say which of these approaches is right even though in principle sometimes these different approaches make slightly different predictions you have to think very hard about how you could actually test them and what does quantum tell us about physical reality well that's what's interesting is that these different approaches would give you different answers so if you if I say well I think it's the pilot wave approach is correct I'm gonna say well it tells me that the quantum mechanical wave function is not a complete physical description and maybe the world is deterministic and so on and if I take an objective collapse theories I'm gonna say that tells me the world is fundamentally in deterministic and so there's no single answer to that the one thing we know for sure is that there's a kind of nonlocality and this comes from a theorem of john bell which doesn't depend on the interpretation john john bell proved that just certain results that you get in the lab cannot be reproduced in a theory that is local in a certain well-defined sense so there has to be some non locality where do you stand amongst these theories I I mean I have a slight but this is just my preference my my aesthetic sense is that the pilot wave approach seems more natural to me and the objective collapse approach seems to me more unnatural but I wouldn't you know give a lot of attention to my aesthetic preferences here they're both very serious they're trying to write the theory down in completely precise mathematical terms and everybody should pay attention to all the going things that are actually out there that have a chance of being right what does it mean that you have like this aesthetic preference for well in the so in a collapse theory for example to give you the reason it's called a collapse theory is that you have a wave function that all the theories use and you have equation Schrodinger's equation which is a deterministic equation that tells you how this wave function evolves through time and in the pilot wave theory that's the end of it for the wave function that's all what ever does and in a collapse theory the wave function sometimes collapses it does something very different so for a long time it'll be doing this and then all of a sudden it'll do this or do that and and it'll do that in a completely random way that the theory will tell you well there's some chance it'll do this and some chance it'll do that and in order to specify that theory you then need to add some new parameters to tell me how often this happens at how it happens and so on so there's more new data or new constants of nature that go into specifying that theory whereas in the pilot wave theory it doesn't have that and to me that it feels more natural even Giancarlo Girardi who developed this objective collapse theories always said well for him this was just a kind of stopping point it was a it was a way toward a deeper theory he never thought in theory he himself wrote down felt fundamental to him that he thought there must be something deeper beneath it but these are all very subjective judgments and I wouldn't put that much weight on um but to you it is important that direct impressions inform scientific theories and for instance you take the view that time is real and an actual thing physics any empirical science has to start from what the philosopher Wilfred sellers called the manifest image of the world that is the world as it presents itself to me when I just opened my eyes and of course we know that some of those appearances can be deceptive or misleading you know the the or in water looks bent but it really isn't and so on but you have nowhere else to begin but with the manifest image and then you try and produce theories that would explain it or account for it and part of the manifest image of the world is that it's in space a three-dimensional space and in time and time goes on and things happen in a certain sequence and they take different amounts of time and I can't imagine really what it would be like to say all of that is an illusion like the or being bent in water and there's no reason to think it is so so especially time structure we know how to put it into the fundamental physics and the idea that no this is all an illusion that derives from something else I don't even know how you'd ever get to an idea I mean you can say oh maybe it's like the matrix and we're all plugged into a machine by aliens but there's no way to get to that right the the hypothesis is built so you can never test it and so I think there's been a I think all of the talk about time being an illusion is just a misunderstanding of relativity theory and so on and I diagnosed that in very specific ways why is it a misunderstanding of the relativity theory because relativity doesn't suggest that all the time is an illusion it suggests that the temporal structure of the world isn't what we naively thought it to be in very specific ways but that there is time and the time is directed and goes from past to future and you can't go backwards in time all of that is just the natural way to understand that there's certainly the way Einstein understood the theory there's a funny thing I'll have to mention there was a note that Einstein wrote a note of condolence to the family of his friend Michael besa when he died and this this note Einstein wrote three months before he himself died and in it he writes very poetically about how oh the physicists now know that time is an illusion and so on and everybody quotes that as if this was Einstein's considered scientific view which it makes no sense whatever because he never said that in any scientific paper he never said that in places where he's expositor the theory of relativity he was writing a note to cheer up people who had just lost lost their son and it was a very kind thing for him to do but the idea that he had this view of time that he kept all to himself until three months before he died and then and then wrote it down in a note and and that's how to understand the theory of relativity that makes no sense at all but people like it it's it's the eye if someone says oh time is an illusion that sounds amazing you know Wow tell me about that but I just think there's really nothing to to it quite honestly is that an issue of celebrity science in general that we start mixing up serious work with a public persona that these scientists yeah there's that and there's the temptation quite honestly and it's hard to resist it certain things are just sell I mean they're kind of sexy or they're kind of mind-blowing and there are some amazing things we've discovered and I think Belle put his finger on the fundamental new thing about quantum mechanics but if someone says oh a cat can be both alive and dead at the same time or they're an infinite number of parallel worlds or something like that that just sounds like science fiction and people react in an emotional way to it and they're attracted to it and so it's very easy want to repeat things like that and get this rise out of the audience you know you understand that people are tempted that way but my job is to try and say look let's slow down here they're very interesting results but let's not mix them up with pure speculation or you know things that just sound so any of you then Schrodinger's cat is just a sexy kind of what the Schrodinger cat thought experiment when Schrodinger wrote it down had a very serious point and his point was that the understanding of quantum mechanics that Bohr and Heisenberg had produced which goes by the name of the Copenhagen interpretation was completely unacceptable because it had this consequence that a cat could end up neither alive or dead and Schrodinger said that's ridiculous right that tells you you've made a mistake Bohr right that tells you you've made a mistake Heisenberg go back and think again and so the example had a very serious purpose the purpose wasn't to convince you that there are cats that are neither dead or alive that was supposed to be the absurd consequence of a bad interpretation that tells you don't think that way we needed you know we need to understand this theory but now we've we have this theory presented as reflecting in quantum mechanics in physics textbooks yep how did we get here it's a we got here because the there were really two phases to this I think one was early on Niels Bohr who had some kind of amazing magnetic personality that I don't understand but you just see his effect on people he loved these kind of weird Gnostic hard to understand pronouncements and and he thought the key to quantum mechanics was that you couldn't understand it in normal ways of thought and we sort of reached the limit of our intuitive understanding of the world and he pushed that very hard and said a lot of very obscure and inscrutable things and and very strongly enforced that other people say this and people like Einstein just never put up with it I mean that's why Einstein hey you know really did not like war and the Copenhagen and he was always fighting against it because it didn't make any sense and it was obscure and so this the few people who were fighting against it really got sidelined very politically and then when it came to the United States all of this Borean kind of hard to understand semi mystical philosophy got kind of thrown away and then it became shut up and calculate so they said we'll just don't ask us questions like what's really going on just we have a thing that you can use to make good predictions just use it to make the predictions and don't ask these and that when I studied physics as an undergraduate that happened to me in my first quantum mechanics course I put up my hand and asked the physics professor well is it like this and he and his answer was no you can't think of it that way but then he didn't go on to say here's how you think of it it's like don't think of it right you know I just calculate the numbers and so this shut up and you know this was has become known it's not quite clear who started this is shut up and calculate and that's a practical point of view if all you care about is making predictions but if you care about what the world really is not about building bridges or making microchips but if you're just curious what's really going on shut up and calculate doesn't get you anywhere and so the physics textbooks are all written by people who never studied these questions because they were told not to ask them and not to think about them they were very exquisitely told do not think about these questions but if a theory helps you make predictions and shouldn't get also that doesn't it take what the world really is or what reality really is into account let me give you a very simple example people knew for thousands and thousands of years ago that aspirin will actually have medical uses it'll make your headaches go away they knew that empirically they didn't have a clue even long into the 20th century how it works they knew you took the bark of a certain tree and you chewed it or whatever and your headache went now if all you care about is getting rid of your headache you're happy you don't care how it works so you can have something that tells you very effectively practically what to do and not have a clue why it works you may know that it works but not it but not have a clue how it works yes it is exactly what's happened in quantum theory we have a very effective mathematical recipe for grinding out predictions and those predictions are really accurate so there's something in that recipe that reflects the real world but exactly what reflects the real world and how you can stare at that mathematics from morning till night and the mathematics won't tell you you'll need a physical theory um so the way you present the kind of fight for truth in quantum physics sounds like a bit of a power struggle what's the role of power in science well powers there are some people who literally are good at wielding institutional power and in academia you know you have to get a position you have to get tenure if you're a physicist and you are interested in these foundational questions it will kill your career or it used to now it's a bit better but there was certainly a time where literally you could not get a job if you said I'm interested in the foundations of quantum mechanics not in a physics department you could get one in a philosophy department and maybe you could get one in a math department as a mathematical physicist and the hardest place was in a physics department there are some people who you know really and Bohr early on knew how to use institutional power but that's not usually what happens more it's just you do what your professors do you know you're you're brought up in a certain culture and if then the culture is don't ask these questions you just don't ask them and if you then go on to teach you tell your students don't ask them so it's not so much the imposition of power in a hard way it's just the kind of influence that the general zeitgeist around you hands what would you like to happen in the academic environment in particularly in what physicists are doing about quantum now uh what I really want to happen what I'm working hard right now in a practical way to happen is simply to have foundations of physics recognized institutionally as a legitimate enterprise that it's it's something that some people can devote their lives to and if you're a physicist who doesn't care about it and you just want to make the predictions or you just want to run the experiment fine but you say there are these people who are interested in this question and they're doing also a serious kind of work and to have it have it recognized institutionally it would be nice if every student who learned quantum mechanics at least got a 3-page accurate description of the situation right if you really want to understand the foundations and you have to have classes and foundations sometimes I mean I physicists have this idea because they have a physics PhD they must they must know all these answers and if you then but then you have to ask well where did you learn it it wasn't in your textbooks you never learn foundations you never took a course in it you never read a chapter about it you never read a book about it why do you think you know about it all I really want people to do is to recognize that this is a serious work and they're serious people some people in physics departments on people in math departments some people in philosophy departments working on a common project and it's a legitimate project thank you so much for more debates talks and interviews subscribe today to the Institute of Arts and ideas at IAI TV you

Channel: The Institute of Art and Ideas

Views: 146,701

Rating: 4.652741 out of 5

Keywords: the problem with quantum theory, quantum mechanics, quantum theory, quantum non-locality relativity, tim maudlin, truth and paradox, quantum physics, the problem with quantum mechanics, philosophy of quantum, general relativity, schrodingers cat, roger penrose, the measurement problem, dark matter, dark energy, space time, physics, science, einstein, newton

Id: hC3ckLqsL5M

Length: 19min 51sec (1191 seconds)

Published: Sun Jun 23 2019

Reddit Comments

[u/BakuDreamer]

' Shut up and calculate ' is attributed to Richard Feynman, rightly or not.

[u/MoiMagnus]

If I sum-up with my own words the argument in this video: the quantum theory is a purely predictive theory, but not an explanatory theory at all. It gives you mathematical formalism to predict the result of an experimentation, but let you puzzled about what is reality and what exists or not.

What are called interpretations of the quantum theory are tentatives to enhance the quantum theory with an explanatory part, in order to be a predictive and explanatory theory. Tim Maudlin does not believe a non-explanatory theory is worth being called a theory, and is just a mathematical formalism empirically confirmed. Hence for him, finding a satisfying interpretation is required to says that "we have a quantum theory", and that scientist should not avoid the burden of trying to find such an interpretation just because the mathematical model works. And more importantly, the research of such an interpretation should be recognize as an important part of the scientific research and not just philosophy.

I'd like to point that quantum theory is currently as a state such that unless new breakthrough, it is likely that we never get to determine which interpretation is correct, and that multiple interpretations fundamentally different at a philosophical level (is the world deterministic or not?) might all be compatible with the experiences we're able to make.

In fact, some researchers in quantum theory I know actually believe finding an explanatory theory might be out of human's reach, and that we will be stuck with predictive theories forever. It is even possible that no explanatory theory can be perfectly predictive, which is quite near to a nihilistic approach of science (the universe would be fundamentally absurd to the human mind).

[u/shitpaw]

I was immediate distracted by the naked looking person stumbling in the background water.

[u/Drifter_01]

I was thinking by looking at the thumbnail, ofcourse they will be talking about quicksilver

[u/zombiesingularity]

From Schrödinger's cat to General Relativity, Professor of Philosopher at NYU, Tim Maudlin, explains the problem with quantum theory today and how the foundations of quantum mechanics should be understood.