Transcript
00:00:00 The following is a conversation with Lee Smolin.
00:00:02 He’s a theoretical physicist,
00:00:04 co inventor of loop quantum gravity,
00:00:06 and a contributor of many interesting ideas
00:00:08 to cosmology, quantum field theory,
00:00:11 the foundations of quantum mechanics,
00:00:12 theoretical biology, and the philosophy of science.
00:00:16 He’s the author of several books,
00:00:18 including one that critiques the state of physics
00:00:21 and string theory called The Trouble with Physics.
00:00:24 And his latest book, Einstein’s Unfinished Revolution,
00:00:27 The Search for What Lies Beyond the Quantum.
00:00:30 He’s an outspoken personality in the public debates
00:00:32 on the nature of our universe,
00:00:34 among the top minds in the theoretical physics community.
00:00:38 This community has its respected academics,
00:00:41 its naked emperors, its outcasts and its revolutionaries,
00:00:44 its madmen and its dreamers.
00:00:46 This is why it’s an exciting world to explore
00:00:49 through a long form conversation.
00:00:51 I recommend you listen back to the episodes
00:00:53 with Leonard Susskind, Sean Carroll, Michio Okaku,
00:00:57 Max Tegmark, Eric Weinstein, and Jim Gates.
00:01:01 You might be asking, why talk to physicists
00:01:03 if you’re interested in AI?
00:01:06 To me, creating artificial intelligence systems
00:01:08 requires more than Python and deep learning.
00:01:11 It requires that we return to exploring
00:01:13 the fundamental nature of the universe and the human mind.
00:01:18 Theoretical physicists venture out into the dark,
00:01:21 mysterious, psychologically challenging place
00:01:23 of first principles more than almost any other discipline.
00:01:28 This is the Artificial Intelligence Podcast.
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00:01:38 at Lex Friedman, spelled F R I D M A N.
00:01:42 As usual, I’ll do one or two minutes of ads now
00:01:45 and never any ads in the middle
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00:02:58 And now, here’s my conversation with Lee Smolin.
00:03:03 What is real?
00:03:05 Let’s start with an easy question.
00:03:06 Put another way, how do we know what is real
00:03:09 and what is merely a creation
00:03:10 of our human perception and imagination?
00:03:14 We don’t know.
00:03:15 We don’t know.
00:03:16 This is science.
00:03:17 I presume we’re talking about science.
00:03:19 And we believe, or I believe,
00:03:24 that there is a world that is independent of my existence
00:03:28 and my experience about it and my knowledge of it,
00:03:32 and this I call the real world.
00:03:35 So you said science, but even bigger than science, what?
00:03:39 Sure, sure.
00:03:40 I need not have said this is science.
00:03:42 I just was warming up.
00:03:44 Warming up?
00:03:46 Okay, now that we’re warmed up,
00:03:47 let’s take a brief step outside of science.
00:03:51 Is it completely a crazy idea to you
00:03:54 that everything that exists is merely a creation
00:03:57 of our mind?
00:03:58 So there’s a few, not many.
00:04:01 This is outside of science now.
00:04:04 People who believe sort of perception
00:04:06 is fundamentally what’s in our human perception,
00:04:10 the visual cortex and so on,
00:04:11 the cognitive constructs that’s being formed there
00:04:16 is the reality.
00:04:18 And then anything outside is something
00:04:20 that we can never really grasp.
00:04:22 Is that a crazy idea to you?
00:04:24 There’s a version of that that is not crazy at all.
00:04:27 What we experience is constructed by our brains
00:04:33 and by our brains in an active mode.
00:04:38 So we don’t see the raw world.
00:04:41 We see a very processed world.
00:04:43 We feel something that’s very processed through our brains
00:04:47 and our brains are incredible.
00:04:50 But I still believe that behind that experience,
00:04:55 that mirror or veil or whatever you wanna call it,
00:04:59 there is a real world and I’m curious about it.
00:05:02 Can we truly, how do we get a sense of that real world?
00:05:06 Is it through the tools of physics,
00:05:08 from theory to the experiments?
00:05:11 Or can we actually grasp it in some intuitive way
00:05:15 that’s more connected to our ape ancestors?
00:05:21 Or is it still fundamentally the tools of math and physics
00:05:25 that really allow us to grasp it?
00:05:26 Well, let’s talk about what tools they are.
00:05:29 What you say are the tools of math and physics.
00:05:32 I mean, I think we’re in the same position
00:05:34 as our ancestors in the caves
00:05:37 or before the caves or whatever.
00:05:40 We find ourselves in this world and we’re curious.
00:05:43 We also, it’s important to be able to explain
00:05:47 what happens when there are fires, when there are not fires,
00:05:50 what animals and plants are good to eat and all that stuff.
00:05:56 But we’re also just curious.
00:05:57 We look up in the sky and we see the sun and the moon
00:06:01 and the stars and we see some of those move
00:06:03 and we’re very curious about that.
00:06:07 And I think we’re just naturally curious.
00:06:10 So we make, this is my version of how we work.
00:06:16 We make up stories and explanations.
00:06:20 And where there are two things
00:06:24 which I think are just true of being human,
00:06:27 we make judgments fast because we have to.
00:06:31 Where to survive, is that a tiger or is that not a tiger?
00:06:36 And we go.
00:06:37 Act.
00:06:38 We have to act fast on incomplete information.
00:06:41 So we judge quickly and we’re often wrong
00:06:46 or at least sometimes wrong, which is all I need for this.
00:06:49 We’re often wrong.
00:06:50 So we fool ourselves and we fool other people readily.
00:06:56 And so there’s lots of stories that get told
00:06:59 and some of them result in a concrete benefit
00:07:04 and some of them don’t.
00:07:06 So you said we’re often wrong,
00:07:09 but what does it mean to be right?
00:07:12 Right, that’s an excellent question.
00:07:15 To be right, well since I believe that there is a real world,
00:07:23 I believe that to be, you can challenge me on this
00:07:26 if you’re not a realist.
00:07:27 A realist is somebody who believes
00:07:28 in this real objective world
00:07:31 which is independent of our perception.
00:07:33 If I’m a realist, I think that to be right
00:07:38 is to come closer.
00:07:40 I think first of all, there’s a relative scale.
00:07:42 There’s not right and wrong.
00:07:43 There’s right or more right and less right.
00:07:46 And you’re more right if you come closer
00:07:49 to an exact true description of that real world.
00:07:53 Now can we know that for sure?
00:07:54 No.
00:07:56 And the scientific method is ultimately
00:07:58 what allows us to get a sense
00:08:00 of how close we’re getting to that real world?
00:08:03 No on two counts.
00:08:04 First of all, I don’t believe there’s a scientific method.
00:08:08 I was very influenced when I was in graduate school
00:08:10 by the writings of Paul Fireman
00:08:12 who was an important philosopher of science
00:08:15 who argued that there isn’t a scientific method.
00:08:18 There is or there is not?
00:08:19 There is not.
00:08:20 Can you elaborate, I’m sorry if you were going to,
00:08:23 but can you elaborate on what does it mean
00:08:27 for there not to be a scientific method,
00:08:28 this notion that I think a lot of people believe in
00:08:33 in this day and age?
00:08:34 Sure.
00:08:36 Paul Fireman, he was a student of Popper
00:08:39 who taught Karl Popper.
00:08:42 And Fireman argued both by logic
00:08:48 and by historical example that you name anything
00:08:51 that should be part of the practice of science.
00:08:55 Say you should always make sure that your theories agree
00:08:57 with all the data that’s already been taken.
00:09:01 And he’ll prove to you that there have to be times
00:09:03 when science contradicts, when some scientist contradicts
00:09:08 that advice for science to progress overall.
00:09:16 So it’s not a simple matter.
00:09:18 I think that, I think of science as a community.
00:09:25 Of people.
00:09:26 Of people and as a community of people
00:09:29 bound by certain ethical precepts,
00:09:33 precepts, whatever that is.
00:09:35 So in that community, a set of ideas they operate under,
00:09:40 meaning ethically of kind of the rules of the game
00:09:44 they operate under.
00:09:45 Don’t lie, report all your results,
00:09:48 whether they agree or don’t agree with your hypothesis.
00:09:52 Check the training of a scientist.
00:09:56 Mostly consists of methods of checking
00:09:59 because again, we make lots of mistakes.
00:10:01 We’re very error prone.
00:10:03 But there are tools both on the mathematics side
00:10:06 and the experimental side to check and double check
00:10:09 and triple check.
00:10:11 And a scientist goes through a training
00:10:14 and I think this is part of it.
00:10:16 You can’t just walk off the street and say,
00:10:18 yo, I’m a scientist.
00:10:20 You have to go through the training
00:10:22 and the training, the test that lets you be done
00:10:27 with the training is can you form a convincing case
00:10:33 for something that your colleagues
00:10:37 will not be able to shout down
00:10:40 because they’ll ask, did you check this?
00:10:42 And did you check that?
00:10:43 And did you check this?
00:10:44 And what about seeming contradiction with this?
00:10:47 And you’ve got to have answers to all those things
00:10:52 or you don’t get taken seriously.
00:10:53 And when you get to the point where you can produce
00:10:56 that kind of defense and argument,
00:10:58 then they give you a PhD.
00:11:02 And you’re kind of licensed.
00:11:03 You’re still gonna be questioned
00:11:06 and you still may propose or publish mistakes.
00:11:10 But the community is gonna have to waste less time
00:11:14 fixing your mistakes.
00:11:15 Yes, but if you can maybe linger on it a little longer,
00:11:20 what’s the gap between the thing that that community does
00:11:25 and the ideal of the scientific method?
00:11:28 The scientific method is you should be able
00:11:31 to repeat and experiment.
00:11:36 There’s a lot of elements to what construes
00:11:39 the scientific method, but the final result,
00:11:41 the hope of it is that you should be able to say
00:11:46 with some confidence that a particular thing
00:11:50 is close to the truth.
00:11:53 Right, but there’s not a simple relationship
00:11:55 between experiment and hypothesis or theory.
00:11:58 For example, Galileo did this experiment
00:12:01 of dropping a ball from the top of a tower
00:12:04 and it falls right at the base of the tower.
00:12:07 And an Aristotelian would say, wow,
00:12:10 of course it falls right to the base of the tower.
00:12:12 That shows that the earth isn’t moving
00:12:14 while the ball is falling.
00:12:16 And Galileo says, no way, there’s a principle of inertia
00:12:19 and it has an inertia in the direction
00:12:22 where the earth isn’t moving and the tower
00:12:24 and the ball and the earth all move together.
00:12:26 When the principle of inertia tells you it hits the bottom,
00:12:30 it does look, therefore my principle of inertia is right.
00:12:33 And Aristotelian says, no, our style of science is right.
00:12:37 The earth is stationary.
00:12:39 And so you gotta get an interconnected bunch of cases
00:12:45 and work hard to line up and explain.
00:12:49 It took centuries to make the transition
00:12:51 from Aristotelian physics to the new physics.
00:12:55 It wasn’t done until Newton in 1680 something, 1687.
00:13:02 So what do you think is the nature of the process
00:13:04 that seems to lead to progress?
00:13:07 If we at least look at the long arc of science,
00:13:11 of all the community of scientists,
00:13:13 they seem to do a better job of coming up with ideas
00:13:16 that engineers can then take on and build rockets with
00:13:21 or build computers with or build cool stuff with.
00:13:26 I don’t know, a better job than what?
00:13:30 Than this previous century.
00:13:32 So century by century, we’ll talk about string theory
00:13:35 and so on and kind of possible,
00:13:38 what you might think of as dead ends and so on.
00:13:41 Which is not the way I think of string theory.
00:13:42 We’ll straighten out, we’ll get all the strings straight.
00:13:45 But there is, nevertheless in science, very often,
00:13:49 at least temporary dead ends.
00:13:52 But if you look at the, through centuries,
00:13:57 the century before Newton and the century after Newton,
00:14:01 it seems like a lot of ideas came closer to the truth
00:14:07 that then could be usable by our civilization
00:14:10 to build the iPhone, right?
00:14:12 To build cool things that improve our quality of life.
00:14:15 That’s the progress I’m kind of referring to.
00:14:19 Let me, can I say that more precisely?
00:14:21 Yes, well, it’s a low bar.
00:14:23 Because I think it’s important to get the time places right.
00:14:28 There was a scientific revolution that partly succeeded
00:14:34 between about 1900 or late 1890s
00:14:39 and into the 1930s, 1940s and so.
00:14:45 And maybe some, if you stretched it, into the 1970s.
00:14:50 And the technology, this was the discovery of relativity
00:14:54 and that included a lot of developments of electromagnetism.
00:14:58 The confirmation, which wasn’t really well confirmed
00:15:02 into the 20th century, that matter was made of atoms.
00:15:06 And the whole picture of nuclei with electrons going around,
00:15:09 this is early 20th century.
00:15:12 And then quantum mechanics was from 1905,
00:15:17 took a long time to develop, to the late 1920s.
00:15:21 And then it was basically in final form.
00:15:25 And the basis of this partial revolution,
00:15:29 and we can come back to why it’s only a partial revolution,
00:15:33 is the basis of the technologies that you mentioned.
00:15:37 All of, I mean, electrical technology
00:15:40 was being developed slowly with this.
00:15:42 And in fact, there’s a close relation
00:15:46 between the development of electricity
00:15:49 and the electrification of cities in the United States
00:15:54 and Europe and so forth.
00:15:56 And the development of the science.
00:16:00 The fundamental physics since the early 1970s
00:16:08 doesn’t have a story like that so far.
00:16:11 There’s not a series of triumphs and progresses
00:16:16 and there’s not any practical application.
00:16:19 So just to linger briefly on the early 20th century
00:16:26 and the revolutions in science that happened there,
00:16:30 what was the method by which the scientific community
00:16:33 kept each other in check about when you get something right,
00:16:39 when you get something wrong?
00:16:40 Is experimental validation ultimately the final test?
00:16:43 It’s absolutely necessary.
00:16:45 And the key things were all validated.
00:16:47 The key predictions of quantum mechanics
00:16:50 and of the theory of electricity and magnetism.
00:16:54 So before we talk about Einstein, your new book,
00:16:57 before String Theory, Quantum Mechanics, so on,
00:17:00 let’s take a step back at a higher level question.
00:17:04 What is that you mentioned?
00:17:06 What is realism?
00:17:08 What is anti realism?
00:17:11 And maybe why do you find realism,
00:17:13 as you mentioned, so compelling?
00:17:15 Well, realism is the belief in an external world
00:17:26 independent of our existence, our perception,
00:17:28 our belief, our knowledge.
00:17:30 A realist as a physicist is somebody who believes
00:17:35 that there should be possible some completely objective
00:17:40 description of each and every process
00:17:44 at the fundamental level, which describes and explains
00:17:49 exactly what happens and why it happens.
00:17:52 That kind of implies that that system,
00:17:55 in a realist view, is deterministic,
00:17:58 meaning there’s no fuzzy magic going on
00:18:01 that you can never get to the bottom,
00:18:02 or you can get to the bottom of anything
00:18:04 and perfectly describe it.
00:18:07 Some people would say that I’m not that interested
00:18:10 in determinism, but I could live with the fundamental world,
00:18:15 which had some chance in it.
00:18:18 So do you, you said you could live with it,
00:18:21 but do you think God plays dice in our universe?
00:18:26 I think it’s probably much worse than that.
00:18:30 In which direction?
00:18:32 I think that theories can change,
00:18:33 and theories can change without warning.
00:18:36 I think the future is open.
00:18:38 You mean the fundamental laws of physics can change?
00:18:40 Yeah.
00:18:42 Oh, okay, we’ll get there.
00:18:43 I thought we would be able to find some solid ground,
00:18:49 but apparently the entirety of it, temporarily so, probably.
00:18:55 Okay, so realism is the idea that while the ground
00:19:00 is solid, you can describe it.
00:19:02 What’s the role of the human being,
00:19:04 our beautiful, complex human mind in realism?
00:19:10 Do we have a, are we just another set of molecules
00:19:14 connected together in a clever way,
00:19:16 or the observer, does the observer, our human mind,
00:19:22 consciousness, have a role in this realism view
00:19:24 of the physical universe?
00:19:27 There’s two ways, there’s two questions you could be asking.
00:19:30 One, does our conscious mind, do our perceptions
00:19:35 play a role in making things become,
00:19:38 in making things real or things becoming?
00:19:42 That’s question one.
00:19:43 Question two is, does this, we can call it
00:19:47 a naturalist view of the world that is based on realism,
00:19:54 allow a place to understand the existence of
00:19:58 and the nature of perceptions and consciousness in mind,
00:20:01 and that’s question two.
00:20:04 Question two, I do think a lot about,
00:20:06 and my answer, which is not an answer, is I hope so,
00:20:11 but it certainly doesn’t yet.
00:20:14 So what kind?
00:20:14 Question one, I don’t think so.
00:20:17 But of course, the answer to question one
00:20:18 depends on question two.
00:20:20 Right.
00:20:21 So I’m not up to question one yet.
00:20:24 So question two is the thing that you can kind of
00:20:26 struggle with at this time.
00:20:27 Yes.
00:20:28 That’s, what about the anti realists?
00:20:32 So what flavor, what are the different camps
00:20:36 of anti realists that you’ve talked about?
00:20:38 I think it would be nice if you can articulate
00:20:42 for the people for whom there is not
00:20:44 a very concrete real world, or there’s divisions,
00:20:47 or it’s messier than the realist view of the universe,
00:20:52 what are the different camps, what are the different views?
00:20:54 I’m not sure I’m a good scholar and can talk about
00:20:58 the different camps and analyze it,
00:20:59 but some, many of the inventors of quantum physics
00:21:04 were not realists, were anti realists.
00:21:07 Their scholars, they lived in a very perilous time
00:21:11 between the two world wars.
00:21:13 And there were a lot of trends in culture
00:21:17 which were going that way.
00:21:19 But in any case, they said things like,
00:21:21 the purpose of science is not to give an objective
00:21:27 realist description of nature as it would be
00:21:29 in our absence.
00:21:30 This might be saying Niels Bohr.
00:21:33 The purpose of science is as an extension
00:21:36 of our conversations with each other
00:21:38 to describe our interactions with nature.
00:21:41 And we’re free to invent and use terms like
00:21:44 particle, or wave, or causality, or time, or space.
00:21:48 If they’re useful to us, and they carry some
00:21:53 intuitive implication, but we shouldn’t believe
00:21:58 that they actually have to do with what nature
00:22:00 would be like in our absence,
00:22:02 which we have nothing to say about.
00:22:05 Do you find any aspect of that,
00:22:08 because you kind of said that we human beings
00:22:10 tell stories, do you find aspects of that
00:22:13 kind of anti realist view of Niels Bohr compelling?
00:22:18 That we fundamentally are storytellers,
00:22:20 and then we create tools of space, and time,
00:22:24 and causality, and whatever this fun quantum
00:22:28 mechanic stuff is to help us tell the story of our world.
00:22:32 Sure, I just would like to believe that there’s
00:22:35 an aspiration for the other thing.
00:22:39 The other thing being what?
00:22:41 The realist point of view.
00:22:44 Do you hope that the stories will eventually lead us
00:22:47 to discovering the real world as it is?
00:22:56 Yeah.
00:22:57 Is perfection possible, by the way?
00:22:59 Is it? No.
00:23:00 Well that’s, you mean will we ever get there
00:23:03 and know that we’re there?
00:23:05 Yeah, exactly.
00:23:06 That’s not my, that’s for people 5,000 years in the future.
00:23:09 We’re certainly nowhere near there yet.
00:23:14 Do you think reality that exists outside of our mind,
00:23:20 do you think there’s a limit to our cognitive abilities?
00:23:24 Is, again, descendants of apes,
00:23:26 who are just biological systems,
00:23:28 is there a limit to our mind’s capability
00:23:31 to actually understand reality?
00:23:35 Sort of, there comes a point,
00:23:39 even with the help of the tools of physics,
00:23:42 that we just cannot grasp some fundamental aspects
00:23:46 of that reality.
00:23:47 Again, I think that’s a question
00:23:48 for 5,000 years in the future.
00:23:49 We’re not even close to that limit.
00:23:51 I think there is a universality.
00:23:54 Here, I don’t agree with David Deutsch about everything,
00:23:56 but I admire the way he put things in his last book.
00:24:01 And he talked about the role of explanation.
00:24:04 And he talked about the universality of certain languages
00:24:08 or the universality of mathematics
00:24:11 or of computing and so forth.
00:24:15 And he believed that universality,
00:24:18 which is something real,
00:24:19 which somehow comes out of the fact
00:24:22 that a symbolic system or a mathematical system
00:24:26 can refer to itself and can,
00:24:29 I forget what that’s called,
00:24:30 can reference back to itself and build,
00:24:34 in which he argued for a universality of possibility
00:24:38 for our understanding, whatever is out there.
00:24:41 But I admire that argument,
00:24:45 but it seems to me we’re doing okay so far,
00:24:51 but we’ll have to see.
00:24:53 Whether there is a limit or not.
00:24:55 For now, we’ve got plenty to play with.
00:24:57 Yeah.
00:24:58 There are things which are right there in front of us
00:25:01 which we miss.
00:25:03 And I’ll quote my friend, Eric Weinstein,
00:25:06 in saying, look, Einstein carried his luggage.
00:25:10 Freud carried his luggage.
00:25:12 Marx carried his luggage.
00:25:13 Martha Graham carried her luggage, et cetera.
00:25:17 Edison carried his luggage.
00:25:19 All these geniuses carried their luggage.
00:25:22 And not once before relatively recently
00:25:25 did it occur to anybody to put a wheel on luggage
00:25:28 and pull it.
00:25:29 And it was right there waiting to be invented
00:25:33 for centuries.
00:25:34 So this is Eric Weinstein.
00:25:37 Yeah.
00:25:39 What do the wheels represent?
00:25:40 Are you basically saying that there’s stuff
00:25:42 right in front of our eyes?
00:25:43 That once we, it just clicks,
00:25:46 we put the wheels on the luggage,
00:25:48 a lot of things will fall into place.
00:25:49 Yes, I do, I do.
00:25:52 And every day I wake up and think,
00:25:55 why can’t I be that guy who was walking through the airport?
00:26:00 What do you think it takes to be that guy?
00:26:02 Because like you said,
00:26:05 a lot of really smart people carried their luggage.
00:26:10 What, just psychologically speaking,
00:26:12 so Eric Weinstein is a good example of a person
00:26:14 who thinks outside the box.
00:26:16 Yes.
00:26:16 Who resists almost conventional thinking.
00:26:21 You’re an example of a person who by habit,
00:26:25 by psychology, by upbringing, I don’t know,
00:26:28 but resists conventional thinking as well,
00:26:31 just by nature.
00:26:32 Thank you, that’s a compliment.
00:26:32 That’s a compliment?
00:26:34 Good.
00:26:34 So what do you think it takes to do that?
00:26:37 Is that something you were just born with?
00:26:40 I doubt it.
00:26:42 Well, from my studying some cases,
00:26:47 because I’m curious about that, obviously,
00:26:49 and just in a more concrete way,
00:26:52 when I started out in physics,
00:26:54 because I started a long way from physics,
00:26:57 so it took me a long, not a long time,
00:27:00 but a lot of work to get to study it and get into it,
00:27:04 so I did wonder about that.
00:27:07 And so I read the biographies,
00:27:10 and in fact, I started with the autobiography of Einstein
00:27:12 and Newton and Galileo and all those people.
00:27:18 And I think there’s a couple of things.
00:27:22 Some of it is luck, being in the right place
00:27:24 at the right time.
00:27:26 Some of it is stubbornness and arrogance,
00:27:28 which can easily go wrong.
00:27:30 Yes.
00:27:31 And I know all of these are doorways.
00:27:36 If you go through them slightly at the wrong speed
00:27:38 or in the wrong angle, they’re ways to fail.
00:27:45 But if you somehow have the right luck,
00:27:47 the right confidence or arrogance, caring,
00:27:52 I think Einstein cared to understand nature
00:27:56 with ferocity and a commitment that exceeded
00:28:00 other people of his time.
00:28:02 So he asked more stubborn questions.
00:28:05 He asked deeper questions.
00:28:09 I think, and there’s a level of ability
00:28:15 and whether ability is born in or can be developed
00:28:20 to the extent to which it can be developed,
00:28:21 like any of these things like musical talent.
00:28:24 So you mentioned ego.
00:28:27 What’s the role of ego in that process?
00:28:29 Confidence.
00:28:30 Confidence.
00:28:30 But in your own life, have you found yourself
00:28:34 walking that nice edge of too much or too little,
00:28:38 so being overconfident and therefore
00:28:41 leaning yourself astray or not sufficiently confident
00:28:43 to throw away the conventional thinking
00:28:47 of whatever the theory of the day, of theoretical physics?
00:28:51 I don’t know if I, I mean, I’ve contributed
00:28:54 where I’ve contributed, whether if I had had
00:28:57 more confidence in something, I would have gotten further.
00:29:01 I don’t know.
00:29:03 Certainly, I’m sitting here at this moment
00:29:09 with very much my own approach to nearly everything.
00:29:14 And I’m calm, I’m happy about that.
00:29:18 But on the other hand, I know people
00:29:20 whose self confidence vastly exceeds mine.
00:29:26 And sometimes I think it’s justified
00:29:28 and sometimes I think it’s not justified.
00:29:33 Your most recent book titled
00:29:35 Einstein’s Unfinished Revolution.
00:29:37 So I have to ask, what is Einstein’s unfinished revolution
00:29:42 and also how do we finish it?
00:29:45 Well, that’s something I’ve been trying to do my whole life,
00:29:48 but Einstein’s unfinished revolution
00:29:51 is the twin revolutions which invented relativity theory,
00:29:54 special and especially general relativity,
00:29:58 and quantum theory, which he was the first person
00:30:01 to realize in 1905 that there would have to be
00:30:04 a radically different theory which somehow realized
00:30:09 or resolved the paradox of the duality
00:30:12 of particle and wave for photons.
00:30:14 And he was, I mean, people I think don’t always
00:30:18 associate Einstein with quantum mechanics
00:30:21 because I think his connection with it,
00:30:24 founding as one of the founders,
00:30:27 I would say, of quantum mechanics,
00:30:28 he kind of put it in the closet.
00:30:30 Is it?
00:30:31 Well, he didn’t believe that the quantum mechanics
00:30:34 as it was developed in the mid to late 1920s
00:30:38 was completely correct.
00:30:39 At first, he didn’t believe it at all.
00:30:42 Then he was convinced that it’s consistent,
00:30:44 but incomplete, and that also is my view.
00:30:47 It needs, for various reasons, I can elucidate,
00:30:52 to have additional degrees of freedom, particles,
00:30:56 forces, something to reach the stage
00:31:00 where it gives a complete description of each phenomenon,
00:31:03 as I was saying, realism demands.
00:31:07 So what aspect of quantum mechanics
00:31:10 bothers you and Einstein the most?
00:31:12 Is it some aspect of the wave function collapse discussions,
00:31:18 the measurement problem?
00:31:19 Is it the?
00:31:23 The measurement problem.
00:31:24 I’m not gonna speak for Einstein.
00:31:26 But the measurement problem, basically, and the fact that.
00:31:31 What is the measurement problem, sorry?
00:31:34 The basic formulation of quantum mechanics
00:31:36 gives you two ways to evolve situations in time.
00:31:41 One of them is explicitly when no observer is observing
00:31:44 and no measurement is taking place.
00:31:47 And the other is when a measurement
00:31:48 or an observation is taking place.
00:31:50 And they basically contradict each other.
00:31:53 But there’s another reason why the revolution
00:31:56 was incomplete, which is we don’t understand
00:31:58 the relationship between these two parts.
00:32:01 General relativity, which became our best theory
00:32:04 of space and time and gravitation and cosmology,
00:32:08 and quantum theory.
00:32:11 So for the most part, general relativity
00:32:14 describes big things.
00:32:15 Quantum theory describes little things.
00:32:18 And that’s the revolution that we found
00:32:20 really powerful tools to describe
00:32:22 big things and little things.
00:32:24 And it’s unfinished because we have
00:32:27 two totally separate things and we need to figure out
00:32:30 how to connect them so we can describe everything.
00:32:32 Right, and we either do that if we believe quantum mechanics
00:32:36 as understood now is correct by bringing general relativity
00:32:42 or some extension of general relativity
00:32:44 that describes gravity and so forth
00:32:46 into the quantum domain that’s called quantize,
00:32:50 the theory of gravity.
00:32:52 Or if you believe with Einstein
00:32:55 that quantum mechanics needs to be completed,
00:32:58 and this is my view, then part of the job
00:33:03 of finding the right completion
00:33:04 or extension of quantum mechanics
00:33:07 would be one that incorporated space, time, and gravity.
00:33:12 So, where do we begin?
00:33:14 So first, let me ask, perhaps you can give me a chance,
00:33:19 if I could ask you some just really basic questions.
00:33:22 Well, they’re not at all.
00:33:23 The basic questions are the hardest,
00:33:24 but you mentioned space, time.
00:33:26 What is space, time?
00:33:28 Space, time, you talked about a construction.
00:33:32 So I believe the space, time is an intellectual construction
00:33:36 that we make of the events in the universe.
00:33:39 I believe the events are real,
00:33:40 and the relationships between the events,
00:33:43 which cause which are real.
00:33:45 But the idea that there’s a four dimensional
00:33:50 smooth geometry which has a metric and a connection
00:33:54 and satisfies the equations that Einstein wrote,
00:33:57 it’s a good description to some scale.
00:34:00 It’s a good approximation, it captures some
00:34:02 of what’s really going on in nature.
00:34:05 But I don’t believe it for a minute is fundamental.
00:34:08 So, okay, we’re gonna allow me to linger on that.
00:34:12 So the universe has events, events cause other events.
00:34:16 This is the idea of causality.
00:34:19 Okay, so that’s real.
00:34:22 That’s in my.
00:34:23 In your view is real.
00:34:25 Or hypothesis, or the theories that I have been working
00:34:29 to develop make that assumption.
00:34:32 So space, time, you said four dimensional space
00:34:35 is kind of the location of things,
00:34:37 and time is whatever the heck time is.
00:34:42 And you’re saying that space, time is,
00:34:47 both space and time are emergent and not fundamental?
00:34:51 No.
00:34:52 Sorry, before you correct me,
00:34:55 what does it mean to be fundamental or emergent?
00:34:58 Fundamental means it’s part of the description
00:35:01 as far down as you go.
00:35:03 We have this notion.
00:35:03 As real.
00:35:04 Yes.
00:35:05 As real as real it could be.
00:35:07 Yeah, so I think that time is fundamental,
00:35:10 and quote goes all the way down,
00:35:12 and space does not, and the combination of them
00:35:16 we use in general relativity that we call space time
00:35:18 also does not.
00:35:20 But what is time then?
00:35:24 I think that time, the activity of time
00:35:29 is a continual creation of events from existing events.
00:35:34 So if there’s no events, there’s no time.
00:35:37 Then there’s not only no time, there’s no nothing.
00:35:41 So I believe the universe has a history
00:35:47 which goes to the past.
00:35:48 I believe the future does not exist.
00:35:51 There’s a notion of the present
00:35:53 and a notion of the past,
00:35:55 and the past consists of,
00:35:58 is a story about events that took place to our past.
00:36:03 So you said the future doesn’t exist.
00:36:05 Yes.
00:36:08 Could you say that again?
00:36:10 Can you try to give me a chance to understand that
00:36:14 one more time?
00:36:15 So events cause other events.
00:36:18 What is this universe?
00:36:19 Cause we’ll talk about locality and nonlocality.
00:36:23 Good.
00:36:25 Cause it’s a crazy, I mean it’s not crazy,
00:36:27 it’s a beautiful set of ideas that you propose.
00:36:32 But, and if Kozali is fundamental,
00:36:34 I’d just like to understand it better.
00:36:37 What is the past?
00:36:38 What is the future?
00:36:40 What is the flow of time?
00:36:42 Even the error of time in our universe, in your view.
00:36:46 And maybe what’s an event, right?
00:36:50 Oh, an event is where something changes,
00:36:54 or where two,
00:36:59 it’s hard to say because it’s a primitive concept.
00:37:02 An event is a moment of time within space.
00:37:07 This is the view in general relativity,
00:37:11 where two particles intersect in their paths,
00:37:15 or something changes in the path of a particle.
00:37:19 Now, we are postulating that there is,
00:37:23 at the fundamental level, a notion,
00:37:25 which is an elementary notion,
00:37:27 so it doesn’t have a definition in terms of other things,
00:37:31 but it is something elementary happening.
00:37:34 And it doesn’t have a connection to energy,
00:37:36 or matter, or exchange of energy?
00:37:38 It does have a connection to energy and matter.
00:37:40 So it’s at that level.
00:37:41 Yeah, it involves,
00:37:43 and that’s why the version of a theory of events
00:37:48 that I’ve developed with Marina Cortez,
00:37:50 and it’s, by the way, I wanna mention my collaborators,
00:37:54 because they’ve been at least as important
00:37:55 in this work as I have.
00:37:57 It’s Marina Cortez in all the work since about 2013,
00:38:02 2012, 2013, about causality, causal sets.
00:38:07 And in the period before that, Roberta Mangibera Unger,
00:38:11 who is a philosopher and a professor of law.
00:38:14 And that’s in your efforts,
00:38:16 together with your collaborators,
00:38:17 to finish the unfinished revolution.
00:38:20 Yes.
00:38:20 And focus on causality as a fundamental.
00:38:23 Yes.
00:38:24 As fundamental to physics.
00:38:26 So.
00:38:28 And there’s certainly other people we’ve worked with,
00:38:30 but those two people’s thinking
00:38:32 had a huge influence on my own thinking.
00:38:34 So in the way you describe causality,
00:38:36 that’s what you mean of time being fundamental.
00:38:39 That causality is fundamental.
00:38:41 Yes.
00:38:43 And what does it mean for space to not be fundamental,
00:38:47 to be emergent?
00:38:48 That’s very good.
00:38:48 There’s a level of description in which there are events,
00:38:52 there are events create other events,
00:38:58 but there’s no space.
00:38:59 They don’t live in space.
00:39:00 They have an order in which they caused each other.
00:39:04 And that is part of the nature of time for us.
00:39:07 But there is an emergent approximate description.
00:39:13 And you asked me to define emergent.
00:39:15 I didn’t.
00:39:17 An emergent property is a property
00:39:22 that arises at some level of complexity,
00:39:26 larger than and more complex than the fundamental level,
00:39:31 which requires some property to describe it,
00:39:36 which is not directly
00:39:40 explicable or derivable is the word I want
00:39:44 from the properties of the fundamental things.
00:39:48 And space is one of those things
00:39:50 in a sufficiently complex universe,
00:39:53 space, three dimensional position of things emerged.
00:39:58 Yes, and we have this,
00:39:59 we saw how this happens in detail in some models,
00:40:03 both computationally and analytically.
00:40:07 Okay, so connected to space is the idea of locality.
00:40:11 Yes.
00:40:13 So we’ve talked about realism.
00:40:15 So I live in this world that like sports.
00:40:21 Locality is a thing that you can affect things close to you
00:40:26 and don’t have an effect on things that are far away.
00:40:29 It’s the thing that bothers me about gravity in general
00:40:32 or action at a distance.
00:40:35 Same thing that probably bothered Newton,
00:40:37 or at least he said a little bit about it.
00:40:43 Okay, so what do you think about locality?
00:40:45 Is it just a construct?
00:40:48 Is it us humans just like this idea
00:40:51 and are connected to it because we exist in it,
00:40:54 we need it for our survival, but it’s not fundamental?
00:40:57 I mean, it seems crazy for it not to be
00:40:58 a fundamental aspect of our reality.
00:41:01 It does.
00:41:03 Can you comfort me on a sort of as a therapist,
00:41:05 like how do I?
00:41:07 I’m not a good therapist, but I’ll do my best.
00:41:10 Okay.
00:41:13 There are several different definitions of locality
00:41:16 when you come to talk about locality in physics.
00:41:20 In quantum field theory,
00:41:23 which is a mixture of special relativity
00:41:27 and quantum mechanics,
00:41:29 there is a precise definition of locality.
00:41:33 Field operators corresponding to events in space time,
00:41:37 which are space like separated,
00:41:38 commute with each other as operators.
00:41:41 So in quantum mechanics,
00:41:43 you think about the nature of reality as fields
00:41:46 and things that are close in a field
00:41:48 have an impact on each other more than farther away.
00:41:53 That’s, yes.
00:41:54 That’s very comforting.
00:41:55 That makes sense.
00:41:56 So that’s a property of quantum field theory
00:41:58 and it’s well tested.
00:42:00 Unfortunately, there’s another definition of local,
00:42:04 which was expressed by Einstein
00:42:07 and expressed more precisely by John Bell,
00:42:11 which has been tested experimentally and found to fail.
00:42:15 And this set up is you take two particles.
00:42:19 So one thing that’s really weird about quantum mechanics
00:42:24 is a property called entanglement.
00:42:26 You can have two particles interact
00:42:28 and then share a property
00:42:31 without it being a property
00:42:32 of either one of the two particles.
00:42:35 And if you take such a system
00:42:38 and then you make a measurement on particle A,
00:42:43 which is over here on my right side,
00:42:46 and particle B, which is over here.
00:42:48 Somebody else makes a measurement of particle B.
00:42:50 You can ask that whatever is the real reality
00:42:56 of particle B, it not be affected by the choice
00:43:01 the observer at particle A makes about what to measure,
00:43:04 not the outcome,
00:43:06 just the choice of the different things they might measure.
00:43:09 And that’s a notion of locality
00:43:11 because it assumes that these things
00:43:13 are very far spaced like separated.
00:43:16 And it’s gonna take a while for any information
00:43:19 about the choice made by the people here at A
00:43:22 to affect the reality at B.
00:43:24 But you make that assumption,
00:43:25 that’s called Bell locality.
00:43:27 And you derive a certain inequality
00:43:30 that some correlations,
00:43:32 functions of correlations have to satisfy.
00:43:36 And then you can test that pretty directly
00:43:39 in experiments which create pairs of photons
00:43:42 or other particles.
00:43:44 And it’s wrong by many sigma.
00:43:46 In experiment, it doesn’t match.
00:43:49 So what does that mean?
00:43:51 That means that that definition of locality
00:43:54 I stated is false.
00:43:56 The one that Einstein was playing with.
00:43:58 Yeah, and the one that I stated,
00:44:00 that is it’s not true that whatever is real
00:44:04 about particle B is unaffected by the choice
00:44:08 that the observer makes as to what to measure
00:44:10 in particle A.
00:44:12 No matter how long they’ve been propagating
00:44:14 at almost the speed of light or the speed of light
00:44:17 away from each other, it’s no matter.
00:44:19 So like the distance between them.
00:44:22 Well, it’s been tested, of course,
00:44:23 if you want to have hope for quantum mechanics
00:44:27 being incomplete or wrong and corrected
00:44:30 by something that changes this.
00:44:32 It’s been tested over a number of kilometers.
00:44:35 I don’t remember whether it’s 25 kilometers
00:44:39 or a hundred and something kilometers, but.
00:44:42 So in trying to solve the unsolved revolution,
00:44:47 in trying to come up with the theory for everything,
00:44:50 is causality fundamental and breaking away from locality?
00:44:57 Absolutely.
00:44:59 A crucial step.
00:45:00 So in your book, essentially, those are the two things
00:45:04 we really need to think about as a community.
00:45:07 Especially the physics community has to think about this.
00:45:12 I guess my question is, how do we solve?
00:45:15 How do we finish the unfinished revolution?
00:45:19 Well, that’s, I can only tell you what I’m trying to do
00:45:22 and what I’ve abandoned as not working.
00:45:27 As one ant, smart ant in an ant colony.
00:45:31 Yep.
00:45:32 Or maybe dumb, that’s why, who knows?
00:45:35 But anyway, my view of the,
00:45:40 we’ve had some nice theories invented.
00:45:45 There’s a bunch of different ones.
00:45:47 Both relate to quantum mechanics,
00:45:49 relate to quantum gravity.
00:45:51 There’s a lot to admire
00:45:53 in many of these different approaches.
00:45:56 But to my understanding,
00:45:58 they, none of them completely solve the problems
00:46:02 that I care about.
00:46:05 And so we’re in a situation
00:46:08 which is either terrifying for a student
00:46:11 or full of opportunity for the right student,
00:46:14 in which we’ve got more than a dozen attempts.
00:46:19 And I never thought, I don’t think anybody anticipated
00:46:22 it would work out this way.
00:46:23 Which work partly and then at some point,
00:46:26 they have an issue that nobody can figure out
00:46:28 how to go around or how to solve.
00:46:31 And that’s the situation we’re in.
00:46:36 My reaction to that is twofold.
00:46:39 One of them is to try to bring people,
00:46:42 we evolved into this unfortunate sociological situation
00:46:46 in which there are communities
00:46:48 around some of these approaches.
00:46:50 And to borrow again, a metaphor from Eric,
00:46:53 they sit on top of hills in the landscape of theories
00:46:58 and throw rocks at each other.
00:47:00 And as Eric says, we need two things.
00:47:02 We need people to get off their hills
00:47:05 and come down into the valleys and party and talk
00:47:08 and become friendly and learn to say,
00:47:14 not no but, but yes and yes.
00:47:18 Your idea goes this far,
00:47:19 but maybe if we put it together with my idea,
00:47:21 we can go further.
00:47:22 Yes.
00:47:25 So in that spirit, I’ve talked several times
00:47:29 with Sean Carroll, who’s also written
00:47:32 an excellent book recently.
00:47:34 And he kind of, he plays around,
00:47:36 is a big fan of the many worlds interpretation
00:47:39 of quantum mechanics.
00:47:40 So I’m a troublemaker.
00:47:42 So let me ask, what’s your sense of Sean
00:47:47 and the idea of many worlds interpretation?
00:47:50 I’ve read many the commentary back and forth.
00:47:52 You guys are friendly, respect each other,
00:47:55 but have a lot of fun debating.
00:47:57 I love Sean and he, no, I really,
00:48:02 he’s articulate and he’s a great representative
00:48:07 or ambassador of science to the public
00:48:10 and for different fields of science to each other.
00:48:14 He also, like I do, takes philosophy seriously.
00:48:19 And unlike what I do in all cases,
00:48:24 he has really done the homework.
00:48:26 He’s read a lot, he knows the people,
00:48:29 he talks to them, he exposes his arguments to them.
00:48:34 And I, there’s this mysterious thing
00:48:37 that we so often end up on the opposite sides
00:48:40 of one of these issues.
00:48:41 It’s fun though.
00:48:43 It’s fun and I’d love to have a conversation about that,
00:48:47 but I would want to include him.
00:48:50 I see, about many worlds, well.
00:48:52 No, I can tell you what I think about many worlds.
00:48:54 I’d love to, but actually on that, let me pause.
00:48:56 Sean has a podcast.
00:48:57 You should definitely figure out how to talk to Sean.
00:49:00 I would, I actually told Sean,
00:49:01 I would love to hear you guys just going back and forth.
00:49:05 So I hope you can make that happen eventually,
00:49:07 you and Sean.
00:49:08 I won’t tell you what it is,
00:49:09 but there’s something that Sean said to me
00:49:12 in June of 2016 that changed my whole approach to a problem.
00:49:17 But I’ll have to tell him first.
00:49:19 Yes, and that, that’ll be great to tell him on his podcast.
00:49:23 So.
00:49:24 I can’t invite myself to his podcast.
00:49:26 But I told him, yeah, okay, we’ll make it happen.
00:49:28 So many worlds.
00:49:30 Anyway.
00:49:31 What’s your view?
00:49:32 Many worlds, we talk about nonlocality.
00:49:34 Many worlds is also a very uncomfortable idea
00:49:39 or beautiful depending on your perspective.
00:49:43 It’s very nice in terms of,
00:49:49 I mean, there’s a realist aspect to it.
00:49:50 I think you called it magical realism.
00:49:52 Yeah.
00:49:53 It’s just a beautiful line.
00:49:55 But at the same time,
00:49:57 it’s very difficult to far limited human minds
00:50:00 to comprehend.
00:50:01 So what are your thoughts about it?
00:50:04 Let me start with the easy and obvious
00:50:08 and then go to the scientific.
00:50:10 Okay.
00:50:12 It doesn’t appeal to me.
00:50:13 It doesn’t answer the questions that I want answered.
00:50:17 And it does so to such a strong case
00:50:20 that when Roberto Mangueber Anger and I
00:50:23 began looking for principles,
00:50:24 and I want to come back and talk about
00:50:26 the use of principles in science,
00:50:28 because that’s the other thing I was going to say,
00:50:30 and I don’t want to lose that.
00:50:32 When we started looking for principles,
00:50:34 we made our first principle,
00:50:36 there is just one world and it happens once.
00:50:39 But so it’s not helpful to my personal approach,
00:50:47 to my personal agenda,
00:50:49 but of course I’m part of a community.
00:50:51 And my sense of the many worlds interpretation,
00:50:57 I have thought a lot about it and struggled a lot with it,
00:51:00 is the following.
00:51:05 First of all, there’s Everett himself,
00:51:07 there’s what’s in Everett.
00:51:10 And there are several issues there
00:51:13 connected with the derivation of the Born Rule,
00:51:16 which is the rule that gives probabilities to events.
00:51:20 And the reasons why there is a problem with probability
00:51:25 is that I mentioned the two ways
00:51:28 that physical systems can evolve.
00:51:31 The many worlds interpretation cuts off,
00:51:34 one, the one having to do with measurement,
00:51:37 and just has the other one, the Schrodinger evolution,
00:51:39 which is this smooth evolution of the quantum state.
00:51:44 But the notion of probability is only in the second rule,
00:51:48 which we’ve thrown away.
00:51:50 So where does probability come from?
00:51:52 And you have to answer the question
00:51:54 because experimentalists use probabilities
00:51:57 to check the theory.
00:52:00 Now, at first sight, you get very confused
00:52:05 because there seems to be a real problem
00:52:07 because in the many worlds interpretation,
00:52:10 this talk about branches is not quite precise,
00:52:13 but I’ll use it.
00:52:16 There’s a branch in which everything that might happen
00:52:19 does happen with probability one in that branch.
00:52:23 You might think you could count the number of branches
00:52:27 in which things do and don’t happen
00:52:30 and get numbers that you can define
00:52:32 as something like frequentist probabilities.
00:52:35 And Everett did have an argument in that direction,
00:52:41 but the argument gets very subtle
00:52:43 when there are an infinite number of possibilities,
00:52:45 as is the case in most quantum systems.
00:52:49 And my understanding,
00:52:50 although I’m not as much of an expert as some other people,
00:52:54 is that Everett’s own proposal failed, did not work.
00:53:00 There are then, but it doesn’t stop there.
00:53:05 There is an important idea that Everett didn’t know about,
00:53:08 which is decoherence,
00:53:10 and it is a phenomenon that might be very much relevant.
00:53:13 And so a number of people post Everett
00:53:19 have tried to make versions of what you might call
00:53:22 many worlds quantum mechanics.
00:53:26 And this is a big area and it’s subtle,
00:53:29 and it’s not the kind of thing that I do well.
00:53:33 So I consulted, that’s why there’s two chapters on this
00:53:36 in the book I wrote.
00:53:37 Chapter 10, which is about Everett’s version,
00:53:39 chapter 11, there’s a very good group of philosophers
00:53:44 of physics in Oxford, Simon Saunders, David Wallace,
00:53:49 Harvey Brown, and a number of others.
00:53:52 And of course there’s David Deutsch, who is there.
00:53:57 And those people have developed and put a lot of work
00:54:01 into a very sophisticated set of ideas
00:54:04 designed to come back and answer that question.
00:54:07 They have the flavor of there are really no probabilities,
00:54:11 we admit that, but imagine if the Everett story was true
00:54:15 and you were living in that multiverse,
00:54:18 how would you make bets?
00:54:20 And so they use decision theory
00:54:24 from the theory of probability and gambling and so forth
00:54:28 to shape a story of how you would bet
00:54:33 if you were inside an Everett in the universe
00:54:35 and you knew that.
00:54:37 And there’s a debate among those experts
00:54:41 as to whether they or somebody else has really succeeded.
00:54:47 And when I checked in as I was finishing the book
00:54:50 with some of those people, like Simon,
00:54:52 who’s a good friend of mine, and David Wallace,
00:54:56 they told me that they weren’t sure
00:54:59 that any of them was yet correct.
00:55:02 So that’s what I put in my book.
00:55:04 Now, to add to that, Sean has his own approach
00:55:08 to that problem in what’s called self referencing
00:55:10 or self locating observers.
00:55:14 And it doesn’t, I tried to read it
00:55:20 and it didn’t make sense to me,
00:55:22 but I didn’t study it hard,
00:55:24 I didn’t communicate with Sean,
00:55:25 I didn’t do the things that I would do,
00:55:27 so I had nothing to say about it in the book.
00:55:30 I don’t know whether it’s right or not.
00:55:32 Let’s talk a little bit about science.
00:55:36 You mentioned the use of principles in science.
00:55:40 What does it mean to have a principle
00:55:43 and why is that important?
00:55:45 When I feel very frustrated about quantum gravity,
00:55:48 I like to go back and read history.
00:55:51 And of course, Einstein, his achievements
00:55:55 are a huge lesson and hopefully something
00:55:59 like a role model.
00:56:00 And it’s very clear that Einstein thought
00:56:05 that the first job when you wanna enter a new domain
00:56:09 of theoretical physics is to discover and invent principles
00:56:13 and then make models of how those principles
00:56:15 might be applied in some experimental situation,
00:56:19 which is where the mathematics comes in.
00:56:22 So for Einstein, there was no unified space and time.
00:56:27 Minkowski invented this idea of space time.
00:56:30 For Einstein, it was a model of his principles
00:56:33 or his postulates.
00:56:36 And I’ve taken the view that we don’t know
00:56:41 the principles of quantum gravity.
00:56:43 I can think about candidates and I have some papers
00:56:46 where I discuss different candidates
00:56:50 and I’m happy to discuss them.
00:56:52 But my belief now is that those partially successful
00:56:56 approaches are all models,
00:57:01 which might describe indeed some quantum gravity physics
00:57:05 in some domain, in some aspect,
00:57:08 but ultimately would be important
00:57:12 because they model the principles
00:57:15 and the first job is to tie down those principles.
00:57:18 So that’s the approach that I’m taking.
00:57:21 So speaking of principles, in your 2006 book,
00:57:26 The Trouble with Physics, you criticized a bit
00:57:30 string theory for taking us away from the rigors
00:57:34 of the scientific method or whatever you would call it.
00:57:37 But what’s the trouble with physics today
00:57:42 and how do we fix it?
00:57:44 Can I say how I read that book?
00:57:47 Sure.
00:57:48 Because I, and I’m not, this of course has to be my fault
00:57:52 because you can’t as an author claim
00:57:55 after all the work you put in that you are misread.
00:57:59 But I will say that many of the reviewers
00:58:04 who are not personally involved
00:58:06 and even many who were working on string theory
00:58:09 or some other approach to quantum gravity
00:58:12 told me, communicated with me and told me
00:58:14 they thought that I was fair
00:58:17 and balance was the word that was usually used.
00:58:20 So let me tell you what my purpose was in writing that book,
00:58:24 which clearly got diverted by,
00:58:28 because there was already a rather hot argument going on.
00:58:35 And this is.
00:58:36 On which topic?
00:58:36 On string theory specifically?
00:58:38 Or in general in physics?
00:58:41 No, more specifically than string theory.
00:58:44 So since we’re in Cambridge, can I say that?
00:58:47 We’re doing this in Cambridge.
00:58:48 Yeah, yeah, of course.
00:58:49 Cambridge, just to be clear, Massachusetts.
00:58:52 And on Harvard campus.
00:58:55 Right, so Andy Straminger is a good friend of mine
00:59:00 and has been for many, many years.
00:59:03 And Andy, so originally there was this beautiful idea
00:59:09 that there were five string theories
00:59:11 and maybe they would be unified into one.
00:59:14 And we would discover a way to break that symmetries
00:59:18 of one of those string theories
00:59:20 and discover the standard model
00:59:22 and predict all the properties
00:59:24 of standard model particles,
00:59:26 like their masses and charges and so forth,
00:59:28 coupling constants.
00:59:31 And then there was a bunch of solutions
00:59:35 to string theory found,
00:59:37 which led each of them to a different version
00:59:39 of particle physics with a different phenomenology.
00:59:42 These are called the Calabi Yao manifolds,
00:59:46 named after Yao, who is also here.
00:59:50 Not, certainly we’ve been friends
00:59:52 at some time in the past anyway.
00:59:55 And then there were, nobody was sure,
00:59:57 but hundreds of thousands of different versions
01:00:00 of string theory.
01:00:01 And then Andy found there was a way
01:00:04 to put a certain kind of mathematical curvature
01:00:07 called torsion into the solutions.
01:00:10 And he wrote a paper, String Theory with Torsion,
01:00:13 in which he discovered there was,
01:00:15 and not formally uncountable,
01:00:20 but he was unable to invent any way
01:00:22 to count the number of solutions
01:00:24 or classify the diverse solutions.
01:00:27 And he wrote that this is worrying
01:00:31 because doing phenomenology the old fashioned way
01:00:33 by solving the theory is not gonna work
01:00:37 because there’s gonna be loads of solutions
01:00:41 for every proposed phenomenology
01:00:42 for anything the experiments discovered.
01:00:45 And it hasn’t quite worked out that way.
01:00:47 But nonetheless, he took that worry to me.
01:00:51 We spoke at least once, maybe two or three times about that.
01:00:56 And I got seriously worried about that.
01:01:00 And this is just a little.
01:01:02 So it’s like an anecdote that inspired
01:01:05 your worry about string theory in general?
01:01:07 Well, I tried to solve the problem
01:01:10 and I tried to solve the problem.
01:01:12 I was reading at that time, a lot of biology,
01:01:15 a lot of evolutionary theory,
01:01:17 like Linmar Gullis and Steve Gould and so forth.
01:01:23 And I could take your time to go through the things,
01:01:29 but it occurred to me,
01:01:30 maybe physics was like evolutionary biology
01:01:33 and maybe the laws evolved.
01:01:36 And there was, the biologists talk about a landscape,
01:01:40 a fitness landscape of DNA sequences
01:01:44 or protein sequences or species or something like that.
01:01:48 And I took their concept and the word landscape
01:01:51 from theoretical biology and made a scenario
01:01:54 about how the universe as a whole could evolve
01:01:59 to discover the parameters of the standard model.
01:02:03 And I’m happy to discuss,
01:02:04 that’s called cosmological natural selection.
01:02:07 Cosmological natural selection.
01:02:09 Yeah.
01:02:10 Wow, so the parameters of the standard model,
01:02:12 so the laws of physics are changing.
01:02:15 This idea would say that the laws of physics
01:02:18 are changing in some way that echoes
01:02:23 that of natural selection,
01:02:24 or just it adjusts in some way towards some goal.
01:02:28 Yes.
01:02:30 And I published that,
01:02:33 I wrote the paper in 1888 or 89,
01:02:36 the paper was published in 92.
01:02:39 My first book in 1997,
01:02:40 The Life of the Cosmos was explicitly about that.
01:02:45 And I was very clear that what was important
01:02:49 is that because you would develop an ensemble of universes,
01:02:55 but they were related by descent to natural selection,
01:03:00 almost every universe would share the property
01:03:03 that it was, its fitness was maximized to some extent,
01:03:08 or at least close to maximum.
01:03:10 And I could deduce predictions
01:03:12 that could be tested from that.
01:03:16 And I worked all of that out
01:03:18 and I compared it to the anthropic principle
01:03:20 where you weren’t able to make tests
01:03:23 or make falsifications.
01:03:24 All of this was in the late 80s and early 90s.
01:03:28 That’s a really compelling notion,
01:03:30 but how does that help you arrive?
01:03:32 I’m coming to where the book came from.
01:03:36 Yes.
01:03:37 So what got me,
01:03:41 I worked on string theory.
01:03:42 I also worked on loop quantum gravity.
01:03:47 And I was one of the inventors of loop quantum gravity.
01:03:50 And because of my strong belief in some other principles,
01:03:55 which led to this notion of wanting a quantum theory
01:03:58 of gravity to be what we call relational
01:04:00 or background independent,
01:04:03 I tried very hard to make string theory
01:04:05 background independent.
01:04:07 And it ended up developing a bunch of tools
01:04:09 which then could apply directly to general relativity
01:04:12 and that became loop quantum gravity.
01:04:15 So the things were very closely related
01:04:17 and have always been very closely related in my mind.
01:04:20 The idea that there were two communities,
01:04:22 one devoted to strings and one devoted to loops is nuts
01:04:25 and has always been nuts.
01:04:28 Okay, so anyway, there’s this nuts community
01:04:32 of loops and strings that are all beautiful
01:04:35 and compelling and mathematically speaking.
01:04:37 And what’s the trouble with all that?
01:04:38 Why is that such a problem?
01:04:40 So I was interested in developing that notion
01:04:45 of how science works based on a community
01:04:47 and ethics that I told you about.
01:04:50 And I wrote a draft of a book about that,
01:04:54 which had several chapters on methodology of science.
01:04:58 And it was a rather academically oriented book.
01:05:02 And those chapters were the first part of the book,
01:05:06 the first third of it.
01:05:07 And you didn’t find their remnants
01:05:09 in what’s now the last part of the trouble with physics.
01:05:14 And then I described a number of test cases, case studies.
01:05:18 And one of them, which I knew was the search
01:05:21 for quantum gravity and string theory and so forth.
01:05:25 And I wasn’t able to get that book published.
01:05:28 So somebody made the suggestion of flipping it around
01:05:34 and starting with a story of string theory,
01:05:36 which was already controversial.
01:05:38 This was 2004, 2005.
01:05:42 But I was very careful to be detailed,
01:05:48 to criticize papers and not people.
01:05:52 You won’t find me criticizing individuals.
01:05:55 You’ll find me criticizing certain writing.
01:05:59 But in any case, here’s what I regret.
01:06:03 Let me make your program worthwhile.
01:06:06 Yes.
01:06:07 As far as I know, with the exception of not understanding
01:06:11 how large the applications to condensed matter,
01:06:15 say ADS CFT would get,
01:06:20 I think largely my diagnosis of string theory
01:06:26 as it was then has stood up since 2006.
01:06:31 What I regret is that the same critique,
01:06:34 I was using string theory as an example,
01:06:37 and the same critique applies to many other communities
01:06:41 in science and all of, including,
01:06:44 and this is where I regret my own community,
01:06:46 that is a community of people working on quantum gravity.
01:06:49 Not science string theory.
01:06:52 But, and I considered saying that explicitly.
01:06:55 But to say that explicitly,
01:06:57 since it’s a small, intimate community,
01:07:00 I would be telling stories and naming names
01:07:04 and making a kind of history
01:07:06 that I have no right to write.
01:07:08 So I stayed away from that, but was misunderstood.
01:07:12 But if I may ask, is there a hopeful message
01:07:16 for theoretical physics that we can take from that book,
01:07:20 sort of that looks at the community,
01:07:22 not just your own work on,
01:07:24 now with causality and nonlocality,
01:07:26 but just broadly in understanding
01:07:29 the fundamental nature of our reality,
01:07:32 what’s your hope for the 21st century in physics?
01:07:37 Well, that we solve the problem.
01:07:39 That we solve the unfinished problem of Einstein’s.
01:07:44 That’s certainly the thing that I care about most in.
01:07:47 Hope for most.
01:07:49 Let me say one thing.
01:07:50 Among the young people that I work with,
01:07:53 I hear very often and sense a total disinterest
01:07:59 in these arguments that we older scientists have.
01:08:03 And an interest in what each other is doing.
01:08:05 And this is starting to appear in conferences
01:08:09 where the young people interested in quantum gravity
01:08:13 make a conference, they invite loops and strings
01:08:16 and causal dynamical triangulations and causal set people.
01:08:20 And we’re having a conference like this next week,
01:08:24 a small workshop at perimeter.
01:08:26 And I guess I’m advertising this.
01:08:28 And then in the summer,
01:08:30 we’re having a big full on conference,
01:08:33 which is just quantum gravity.
01:08:34 It’s not strings, it’s not loops.
01:08:37 But the organizers and the speakers
01:08:39 will be from all the different communities.
01:08:41 And this to me is very helpful.
01:08:45 That the different ideas are coming together.
01:08:49 At least people are expressing an interest in that.
01:08:54 It’s a huge honor talking to you, Lee.
01:08:56 Thanks so much for your time today.
01:08:57 Thank you.
01:08:59 Thanks for listening to this conversation.
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01:09:27 And now let me leave you with some words from Lee Smolin.
01:09:31 One possibility is God is nothing but
01:09:35 the power of the universe to organize itself.
01:09:39 Thanks for listening and hope to see you next time.