Nobel Conference XII The Nature of the Physical Universe: Steven Weinberg on concepts of nature

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Steven Weinberg, a Harvard University physicist talks with Rachel Kranz about some underlying concepts of nature. Weinberg attended the annual Nobel Conference at Gustavus Adolphus College in Saint Peter, Minnesota.

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Well, the title has Is nitrous simple, which is rather a large question. Of course, if you just look around you and nature doesn't appear very simple is a tremendous diversity of phenomena and over the centuries. We've learned how to interpret them first in terms of 92 chemical elements and then had to interpret the chemical elements in terms of a certain number of Elementary particles. But even at that level even if the level of elementary particle physics that you find it in text books on the subject nature still has the appearance of a tremendous non Simplicity. There are over three or four large classes of particles that we call left on this had drawn as photons and there are at least four classes of interactions gravitation and electromagnetism, which are fairly familiar and others that a less-familiar theNuclear force and the strong nuclear force and then not terribly similar to each other. So you might not want to say that. On the basis of what we already know I Nature has that appearance of Simplicity. But Simplicity after all is what we intuitively feel must be found at really the most fundamental level of knowledge. I don't know why we feel this so strongly but then it certainly an ancient dream that someday we would find a few simple principles. That would determine why everything is the way it is and so the fact that it it doesn't appear simple at the level. We we've reached tells us that we must not be at the fundamental level and what I'm going to talk about today.Italy attempts that have been made in the last decade or so to try to see below what I called the textbook level of elementary particle physics to what is a deeper level and we have been receiving all kinds of intimations that underneath he's a level of elementary particle physics, which supposedly underlies all other phenomena. There was a deeper level deeper in the same way that elementary particle physics is deeper than chemistry sign.And that on that level the world does look remarkably simple. There are powerful symmetries which relate all the forces of nature and all the particles of nature so that the description mathematically is much more simple much more elegant than one might have imagined. It's a fascinating idea that there are few basic principles and at their symmetry in his principles that everything has been complimenting in nature. Does that seem something that is possible for people to grasp without an advance knowledge of physics it is that something that that can be understood in a way that still meaningful without understanding the mathematics of it or what any attempt to try be just an over-simplification to the point that it wouldn't have any meaning where are the Perfection of the analogies for example? About to take a an example that played a very large role in the history of physics. We now know that there is a symmetry in nature which technically it's called translation invariance. But speaking very Simply It it means that the laws of nature looks the same wherever you happen to be the laws of nature do not depend on how you choose. What you going to call the zero of your system of measuring latitude and longitude and up and down and to watch that's very natural long time to realize that if you live on the earth, then it just doesn't seem like that's true. The Earth pulls you down. The stars are up there and for thousands of years people thought there was a difference physics in the celestial sphere then here and are dull sublunary world. What we now know there isn't that in fact, it's all governed by Cemetery the cemetery translation friends now that cemetery is in a sense of broken symmetry. It applies to every atom in the Earth every atom of oxygen are solar panel iron in the earth undergoes an interaction with every other atom and the law that represent interaction is completely independent of of where the atoms are two atoms of oxygen was it here on the other end of the universe will attract each other or repel each other exactly the same way and yet the Earth manifestly break the Symmetry the artist here it's not there. So we've always in science been going through this process with tremendous difficulty of trying to see behind appearances and see an underlying symmetry in the case of of translation invariance. Elope normally people. Don't call it that this is something that has a way of thinking about nature. I think most people now have firmly embedded in their minds the idea that the laws of nature pretty much the same wherever in the University of happen to be most people now don't think the Earth is at the center of the universe, but that took a long time in coming. I'm interested in the idea that you have to see beyond appearances to the reality because I know that in other fields than science in say sociology or even in certain areas of philosophy. There is a theory that the only things that exist or at least of whose existence we can be sure of our the appearances that it's somewhat idealistic in both senses to try and assume that there are laws governing everything. I I I know politically also there's this tense of all we can do is deal with one problem at a time. We can't make basic principles that a society is going to be built on or that a legal system is going to run on the idea that everything has to be dealt with individually that we can't have basic concept it. Is it something that science contradicts the very good question because there is in fact an endless tension between late on one hand our commitment to scientists really only to pay attention to things that have observational meaning to only ask Questions that can be answered by experiment. If you will to make theories theories which deal with things which cannot be observed as for example of many of us now think that the cork C fundamental particle which which is the constituent of the constituents of the nuclei of atoms not only cannot be observed with today's techniques. And even though those theories cannot be Well, the series can be confronted with observation for the things were talking about cannot be directly observed. It's a danger. But in fact we always do go back and try what we're talkin to about down to Observation. I think that's one thing about physics and about natural science in general. And that is that no matter how willing are speculations. Are we doing the end? I have always the danger of being proved wrong by experiment and it's only that feeling that experiment could prove you wrong that gives you the feeling that you're really saying something that isn't just woolgathering and as to whether that's true in philosophy and sociology bypass. Can I restate what you're saying as there's a sort of interaction in your observation between on one hand the concrete observable direct reality of things and the abstraction of the law that you're trying to set up it applies to many things that's beyond the reality and that the way you figure out the interaction between those two things is to practice through experimentation to actual activity in the world. Yes. That's exactly what I would have said myself and just add one thing. We have to realize that we are somewhat accidental that through a variety of circumstances human beings happened to be about to be large and a tenth of a metric ton heavy and we have so we are used to certain perceptions. We think of things as having definite color definite substance definite composition about the way the world Works which are based on the particular size and shape and mass we happen to have In dealing with what's fundamental we often have to go to levels which are either March large were much smaller than the level then the scale on which we happen to live and that means that increasingly we we seem to be dealing with ideas that are counterintuitive that are very strange that cannot be expressed except mathematically and some people get the idea that we do it best. We like to be as we want to get away from ordinary experience as friends since I think some people might have the feeling that we build accelerators to produce particles that have never existed in the universe except in our accelerators, simply because we enjoy having fun and doing things that are exotic is possum. Are they are and we're trying to get at them and some phenomena are more relevant to them than others and often the phenomena which are relevant to them are just not the phenomenon which irrelevant to us in our everyday lives. Tell me something about how you work as an investigating scientist. If if you can what are the steps of the process that you go through when you working on a new idea stunt. I'm like others I suspect I'm probably like a large majority of scientists. I think there are some signs of prep science time who make great magical leaps from from one step to another in a way that can't be understood. What I do is Warrendale I get something in my mind, which doesn't quite seem right but smells interesting and I worry about it. I worry about in the shower. I worry about it while raking leaves. I worry about it sitting at my desk off and I watch television at my desk just because I want to sit at my desk and not do anything else, but I I don't have any calculations to do and sometimes We're about your time worrying about two or three different things at the same time and one of them will gel and then that's wonderful because when you begin to see the way out, then you have calculations to do when you can make theories and write paper isn't life gets very exciting. And then you start worrying that something else their experiments that give results that very paradoxical and you worried about what that means very often the result is wrong and mental friends, but it happens often enough. So that is a possibility always have to keep in mind for me. It's an internal worry, I understand three or four different things in a certain area, but they don't quite job with each other. I can see if possible application where the three or four different things. I think I understand but have different consequences just an inconsistency between them. I normally don't worry about that unless it's smells like it might be important. There are reports Grand problems that we all worry about. Why is the charge of the electron Wyatt? What it is? Why is the universe here? I'm real worried about those little things that just don't happen to seem consistent and what I already know they sometimes are more often. They don't What is it about the process of this kind of investigation that you like what keeps you going with all these worries and then and Minor Details that don't quite fit. I think some people say they do it for fun. I wouldn't call it that because of the. Of worrying which is the most important. Is that why you're not doing anything you're not sitting at your desk calculating beautiful mathematical Expressions you or you're really just wasting your time. It is really just for those moments when things click that you do it all for but it isn't that personal a satisfaction, you know physics unlike art mathematics. I think really is a historical process it it is working toward a definite goal and your surfing is part of the historical process and that's very exciting. It is something outside you you're not worrying as a painter does about where to put the next door off of paint. No one will ever be able to say whether you were right or wrong. We really Have ways of finding out whether we're right or wrong and that wonderful interaction with the real world is is one of the recompense. I'm interested in this idea of your historical sense. Do you feel close to the physicist that have preceded you or are you very conscious that they will be physicist who come after you will be looking back at your work. Yeah, I I do feel that for one thing. We feel a part of a great tradition. I think that just as a member of them same Reverend Jackie who is speaking speaking here. Remember the Benedictine order and look, look back to Saint Benedict of nursia and back to 500 AD. We also feel that we are members of an order if you will that has its great Heroes and it's great victories and it's the Fades and the wonderful sense of kinship with the pasta with the future when you really get down to it. It's often more frustrating one hand looking back at the past. It's very hard. Understand the work of the past. In fact, one of the best invitations of how much scientific work shapes the way scientists think is that it's now very hard for us to read the great paper to the Past recedes. It's very difficult to put yourself in the mind of a Heisenberg writing in 1925 and see what was bothering him. Why didn't he make the next step? I find it almost impossible to read some of the great founding papers of quantum mechanics, or I think I understand the physics. Are you looking for the future? I suppose the only thing one thing you feel is resentment that they future scientists will know so much more than we do and it's just not fair. The principle of trying to get inside someone else's mind in the past and that being difficult because you just can't see why he didn't know the right answer because you know it right so it's difficult to understand how he did. Do you have apply that to yourself? Do you ever realize that you've been thinking along lines that prevent you from seeing the right answer just because you're so stuck in a certain frame of mind that you can't get Beyond it to A New Concept. Yes, unfortunately usually too late and then there's some examples in my life which I much regret I meant to take one which I don't think I can explain the details of this a certain mathematical formulas mm call the functional formalism. Let it pass what whatever it is from the time. I was a graduate student until about 1971. I felt that it was a waste of time that is absolutely fruitless that it was some What's a flummery and then in 1971 it began to be a parent through the work of young are physicists, especially the young man in Utrecht that in fact was indispensable in The Next Step even in the very serious that I have been working on could not be taken without it and I had to learn it at the cost of some Agony mental and spiritual that has happened to me more than once all those that was perhaps the worst example, and I don't know what lesson 1 drugs because in fact 11 Contra on the lesson that you have to learn everything because you can't learn everything. I work. We're always in the position of deciding not to learn something deciding not to read a certain Paper not because we're narrow-minded but because there's just too much to learn too much to read to get anything done. Maybe Murray gell-mann can learn everything and read everything that I can't and For that reason, we always have to make these decisions of closing our mind to certain things and too often those decisions are wrong. Closest kind of integration between a scientist thinking and the thinking of people who are not scientists in that that seems to have all kinds of political and social and historical application that that that extend decides. Okay, if if you are a medieval scientist and you believe that the world Works a certain way and God and religion set up certain laws. It seems to me that that's going to affect your thinking even about things that could later be tested. In fact such as How the Universe really does work as opposed to social ideas with her later considered to be wrong if I can actually be proven, I guess what I'm what I'm trying to get at is that it it seems that science has one of the things that shape sort of the general picture of how we look at the world and that's something that goes into our thinking about all kinds of systems not just physical ones, but also maybe social ones a simple Universe might suggest that we could have certain basic social principles of a complex universe that human beings can never hope to even understand might suggest that we have to Societies that we really can't control just doesn't seem to be in a very wrong to try to draw a lessons from the detail contents of natural scientific discovery Harper ordinary human life or social science and there been people who've tried it who was Herbert Spencer who tried to make a kind of physics out of society and it just doesn't work. In fact of a friend of mine once said that he thought it was a good idea for the social science test to try to pattern themselves after a physical science, but they chose the wrong physical science section of try to use physics as a model, but they should have his meteorology because of the uncertainty of weather is much more like social systems and the Beautiful Simplicity of physics. On the other hand, I think it's true. And in fact, I'm convinced of it that the general bulk of scientific discovery can't help but change the way people think about the world at the simplest level. We do not see the world as mysterious anymore. I'm in the we certainly don't understand everything. We understand an awful lot. We know the causes of things. We don't know exactly why it'll rain tomorrow, but we know in general why rain occurs when we don't know exactly how the continents were formed. We have a pretty good idea more or less even Perhaps the most difficult problem of all of how the brain is able to think is yielding to this analysis with lots of holes. We have an idea that there are no mysterious effects without causes and that I think it's the most profound revolution in human thinking we don't have to look in Supernatural world for explanations of what we see around us. Now that doesn't necessarily imply anything about what we affecting of the bed. I think even beyond that the way the scientist operates which has changed over the centuries scientist now or not what scientists were Newton's time science itself is change the scientific method but the scientific method as it is changing is continually serving as a kind of model of human thinking not the only model but it's one way that you move beings can think about things changed well, I think what is the model is inside problem that philosophers endlessly debated about to try to really Define the scientific method has proved much more difficult than to do science. And the fact that is remarkably enough one to do science without having a very clear explicit statement about the scientific method is we all know roughly what it is. It's paying attention to Observation thinking things through logically and not believing in things just because they make you happy or because someone told you to believe them, but because you you've checked them against observation, there's a lot of theory and that there's a lot of building hypotheses and then verifying them or refuting them by observation that all kinds of ways of saying and I'm not sure the right way of saying it but it doesn't really seem to have one says it when those what it is. I don't know how to define a giraffe, but I think I recognize a giraffe when I see one. the the changes have been considerable certainly people thought about it in a different way the ability of theory for example to deal with things that are not directly accessible to Observation my corks for example, and yet not to depart from this ideal of always checking that stops eviction is something I don't think I could have been imagine a century ago earlier and another huge difference is I think it's new to this entry is the sense of the all-embracing this of physical science that is that there is not a separate science of chemistry and a separate science of physics and a separate science of biology, but they're really just science and within science. There are separate principalities, which for reasons of convenience often overwhelming convenience have to work under their own laws, but there really is only one science. I think people have really gotten frightened about in the latest developments in science. At least the latest has the general public is aware of them are are two kinds of principles that are sort of related and it seems to me that you're saying that scientist in a way gotten Beyond The Mists that came out of this I'm talking about relativity and about the idea that the world is so complex and so mysterious and so detailed that we're never going to really be able to say that we understand it and then of course relativity says and even if we do understand it's going to be different somewhere else. Those are the popular misunderstandings, perhaps of the scientific principles. It sounds like you're saying that's not the right attitude that a person who understand science believes that human beings can understand their world can't even control it or at least work with it to some extent and don't have to feel that relativity or the principle of the mystery of science or whatever negates our own ability to control our lives and to control our world. Simplicity I mean principle of Relativity is that the laws of nature have the same no matter how you're moving as long as you're moving in a straight line with constant velocity that was true before and it was Einstein didn't technically speaking was to restore that to being true ask her for a while and had seemed not to be true the other principle that you talkin about the principle of the complexity of nature. I don't really know what you're referring to accept. I suspect you may be referring to quantum mechanics and there again, I don't see complexity would rather Simplicity it is unfortunately a Simplicity, which is is very far removed from Wonder experience quantum mechanics much more so than relativity challenges ordinary human intuition spent the way the world works and it's something you just have to get used to and it is probably the biggest bar to communication between scientists and non scientist that exists now actually The younger generation of scientists growing up finding much more easily thinking quantum mechanical terms and sometimes have trouble thinking about ordinary classical physics, which just shows that human nature is infinitely malleable, but taken together quantum mechanics and relativity. In fact don't give a picture of a complicated world, but of a simple world and I would say simple in a wonderful logical sense quantum mechanics allows you to imagine a great many possible universes including very complicated one so does relativity but if you put them together you find that they are nearly logically incompatible and as a result just as a mathematical exercise, which we haven't yet quite been able to finish but we can sort of see the shape of it as a mathematical exercise one can deduce from quantum mechanics and special relativity be taken together everything else. That's the real Simplicity. There are how many kinds of interaction are the real Simplicity is The Logical Simplicity whether or not from a few principles, you can reduce everything else and I think that looks more hopeful now than it ever has in the past allocatively different stage of science then than we've ever known before in human history. I think it's been moving in this direction for a long time. And in fact the physics that we now are working with quantum mechanics and special relativity was more or less complete by 19:30. And I think what has happened in the last decade or so has been the realization of how powerful those principles are it is. A remarkable development, but I think it's been going in this direction for a long time and I hope it will continue to go and little read some kind of fruition during our lifetimes things for the first time in history will be able to stay in that in some sense. They've understood the totality of the universe or understood a part of that totality. It's hard to somehow either. I found myself just stopping short of that point and I can't conceive of really understanding things that well and yet we're moving in that direction and everything we do we do in as if we we thought we were going to reach that point. So I don't know that's a mystery to me. What will things be like when we understand that much. Is that possible? I don't know.

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