0:01

Hey,

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0:11

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Hugh and Betty and the Nazis

0:33

and Bill's and Joe's and James will

0:36

find in the study of science a

0:38

richer, more rewarding life.

0:42

Hey, welcome to inquiring minds. I'm

0:44

Endrevious gaunt this. This is a podcast

0:46

that explores the space where science and

0:48

society collide. We wanna find out

0:50

what's true, what's left to discover, and

0:53

why it matters.

1:01

It's always a

1:03

good day when I get a new book from

1:05

one of my favorite physicists Sean

1:08

Carroll sent to my house. If you don't

1:10

know Sean or his work, you're in for

1:12

a treat. Sean Carroll is the

1:14

Homewood Professor of Natural Philosophy at

1:16

Johns Hopkins and Fractal FACulty

1:18

at the Santa Fe Institute. He's also

1:21

host of The Mindscape Podcast, an

1:23

author of several books, including one of my favorites

1:25

called The Big Picture. He's received

1:28

awards from the National Science

1:30

Foundation, NASA, the American

1:32

Institute of Physics, and many

1:35

others. And now he's promised

1:37

us a trilogy of books to

1:39

help those of us who are not professional

1:41

physicists take a deeper dive

1:43

into the biggest ideas in the universe.

1:49

Sean Carroll welcome back to inquiring

1:51

minds.

1:52

Thanks so much for having you back. It's great to be here.

1:54

Oh,

1:54

it's always so good to talk to you. So

1:56

you're promising us a trilogy.

1:58

That's right.

1:59

So let's for the sort of for listeners

2:02

who don't know about this exciting trilogy,

2:04

tell us little bit about sort of why you decided to break

2:06

it up into three books. What what is it? Well,

2:08

there's I'll tell you the true story. I mean,

2:10

the fake story would be something about, you know,

2:12

I don't know, literary marriage or something, but

2:15

This project started during the pandemic

2:18

when I was

2:20

I decided that what I would try to do,

2:22

I don't have any ability as a theoretical

2:24

physicist to cure COVID

2:27

or make the epidemic

2:29

spread any more slowly. So I said at

2:31

least I can keep people entertained by making

2:33

some YouTube videos explaining concept

2:36

in physics. And it often happens with

2:38

what I try to do. It got out of hand and it grew.

2:41

And the gimmick was that

2:43

I could tried to explain basic

2:45

ideas in physics, but I would use the equations.

2:48

I would not assume you knew the equations. I would

2:50

teach them to you, teach you what calculus is,

2:52

what a matrix is, all that stuff, what an

2:54

imaginary number is, but then put

2:56

them to work. And and the reason you can do it

2:58

is because you don't have to solve

3:01

the equations as someone who is is

3:03

playing along. And after this is

3:05

all done, it turned into a large

3:07

number of videos. And

3:09

I I thought it would make a good book, and I really

3:11

wanted to write like an opus,

3:13

like a thousand page book with all of physics

3:15

in it. And my publisher came back and

3:17

said, we love this idea, except we also

3:19

love the idea very short books. How would

3:21

you like to divide it into

3:23

seven volumes?

3:25

And and I said, no, I'm just not gonna

3:28

do that. That's not gonna happen. So we

3:30

compromised on three. That's the reason why there are

3:32

three. Well, I mean, you know, it it makes a

3:34

lot of sense. As you say, from a literary perspective,

3:37

and and sort of, you know, fits this whole idea

3:39

of a story. And I also I feel like,

3:42

although I would love to have that thousand page

3:44

OPIS on my shelf. I find it

3:46

more tractable to, like -- Yeah. -- read

3:48

one book at a time and it's Look, you know, we'd

3:51

like you're a you're a book author. We

3:53

know that we like to that a little bit about our publishers

3:55

sometimes, but they also know what they're doing

3:58

sometimes. And I would not, you

4:00

know, reject their advice out of hand

4:02

just because it wasn't what I thought of the first time.

4:04

And I and I do think the the material

4:06

falls pretty cleanly into three separate

4:09

sections. The first book that just came out is

4:11

about classical physics from Aristotle,

4:13

basically up to Einstein. The second

4:15

book will be about quantum mechanics and

4:17

particle physics. Third book will be about

4:19

complexity and emergence. So these

4:22

are all related but pretty separate topics.

4:24

So the the three volumes that should be fine. Yeah.

4:26

I have to say, like, the emergence and and

4:28

complexity one is the one I'm most looking forward

4:30

to. So you've been there. Yeah.

4:32

Since I really do feel like we're on book one.

4:35

You gotta read book one and then, you know,

4:37

the payoff comes in book three. Exactly. But

4:39

I so one thing I wanna I wanna

4:41

kind of glossed over a little bit. I think

4:43

this is a really important point. The difference

4:45

between understanding an

4:47

equation and having to solve it.

4:50

Tell us

4:50

more about that. Yeah. You know,

4:52

the equations that we look at in physics,

4:54

whether it's Einstein's equation or the Schrodinger

4:57

equation or whatever. If you're

4:59

a professional physicist or if you're a student

5:01

studying to be a professional physicist, you get

5:03

to, like, be told what the equation says. But

5:06

that's the easy part. And the hard part is,

5:08

okay, applying it to different situations.

5:11

Solve the equations for a spinning

5:13

black hole for electron and

5:15

helium atom or whatever. And

5:17

that's why the memories of most young

5:19

physics students are mostly of doing problem

5:21

sets pulling all nighters, you

5:23

know, with their friends or doing take

5:25

home exams and all those things. It's all about

5:28

solving the equations. And

5:30

what I realized was If

5:32

you're aiming at an audience that does not

5:34

intend on eventually being professional

5:37

physicists, but just wants to know

5:39

the material, There is a happy

5:41

medium where you can go beyond just hand

5:43

waving and metaphors and so forth

5:45

and do some of the equations but not

5:48

fret about ever solving them. You just

5:50

wanna know what they mean. You just wanna know

5:52

what the ideas are. And that's

5:54

what I'm aiming to do in these books. We'll

5:56

see if it works.

5:57

I also wanna underscore this other

5:59

part of it

5:59

that you talk about where, you know, a lot of

6:02

us

6:02

who aren't physicists professionally love

6:05

the metaphors, love understanding things through

6:07

the analogies, and you've written books using

6:10

that, you know. So

6:12

so why is that not enough? in

6:14

your opinion of, like Well, why should I say, look,

6:17

it

6:17

is enough for some people depending on what

6:19

you want. I I'm a huge believer

6:21

in a vast diverse pluralistic

6:24

ecosystem of talking about these

6:26

things. You know? Look, I'm active on Twitter.

6:28

You can't explain quantum field theory on

6:30

Twitter really or Einstein's equation.

6:33

I've I've done my best. But, you

6:35

know, it it's possible to

6:37

get some understanding using metaphors

6:39

and pictures and things like that. But problem with metaphors

6:42

and words is that usually

6:46

they convey some aspects of the reality

6:49

but not all of them. And

6:51

it's very difficult as the recipient

6:53

of the analogy to really appreciate

6:55

which parts are supposed to be conveyed and which parts

6:58

are not. So for example, a

7:00

classic example is we try to explain the

7:02

expanding universe by imagining

7:04

a balloon that we're blowing up Okay?

7:06

And in many ways that tells you a little bit

7:08

about the expanding universe. But then, you have

7:11

to say, but there's nothing inside the balloon.

7:13

there's that doesn't count. The balloon is not expanding

7:15

into anything. And people are like,

7:17

well, you could tell

7:19

them that, but they don't really believe it. And they're like, well,

7:22

Are galaxies expanding? Like, if I draw

7:24

dots on the balloon, the dots expand along

7:26

with the balloon? And you have to say, no, no, no, they're not really expanding

7:28

because that's not part of the analogy that I was supposed to try

7:30

to, you know, convey. So the

7:33

equations and this is really sort of the payoff

7:35

of the book. And when I give talks about it and things

7:37

like that, the equations can

7:39

surprise us. Right? The equations know

7:42

more than we do. They're smarter than we are.

7:44

And they

7:47

they're right. They're the actual theory.

7:49

And so if you can get that little bit of

7:51

extra understanding, you're you're less

7:53

likely to be confused by the words.

7:55

Okay.

7:55

So now we get a sense of of sort of what

7:57

the payoff is. for doing the work

8:00

in terms of understanding these equations little

8:02

bit better. And I do wanna get into

8:04

a few of them or at least

8:06

some of the general concepts because I think it's really

8:08

hard to talk about equations without

8:11

seeing what they are. So but there are there are

8:13

things we can sort of talk around them really important. But

8:15

one

8:15

one of the things that I wanted to ask right

8:17

from the beginning is that, you know, our last guest

8:19

was Temple Grandin, and she just

8:21

wrote a book called visual thinking in which she

8:23

lays out sort of the different ways

8:25

in which, you know, people

8:28

can can think,

8:30

right, sort of, so how we think. And

8:32

one of them that she was describing that I

8:34

thought was exactly relevant to how

8:37

you're thinking about or how you're presenting this

8:39

information in the book.

8:40

is she she distinguishes

8:43

object visualizer, so people who,

8:45

like, literally see pictures. from

8:48

people who are more sort of visual

8:50

spatial oriented where

8:53

like algebra is easy for them.

8:55

But for the object visualizers, algebra

8:58

can be very difficult. And then there's,

9:00

of course, the majority of us who are kind

9:02

of verbal thinkers, who think in language. What

9:05

are you? I've never actually

9:07

heard that distinction that that you just mentioned

9:09

from Temple Grandin. So

9:11

I I'm I'm gonna have to think about it a

9:13

little bit. There There's a related distinction

9:16

among mathematicians where they

9:18

distinguish between being an algebraist

9:20

and being a geometer. So

9:22

it's the algebraicists who are happy with equations

9:25

and the geometrism are happy with pictures.

9:28

Within that distinction.

9:31

I'm much more of a geometry. I'm actually much

9:33

happier with the pictures than with

9:35

the equations. But the but, you

9:37

know, none of these distinctions are hard and fast.

9:39

Right? So certainly, sometimes

9:42

as a newly minted philosopher myself,

9:46

I talked to fellow philosophers of hers. And sometimes

9:48

my feeling is just like, just give me some equations.

9:50

Like, you're saying a bunch of things. It'll be so much easier

9:52

if you gave me equations. So I do have those moments

9:55

as well. Yeah.

9:55

And and so I think and one of the reasons I

9:57

wanna bring this up because I think that for some people

9:59

who

9:59

are reading your book, I I think

10:02

you're they're gonna different thinking

10:04

styles, we'll have we'll get different

10:06

things out of the book, and we'll we'll approach the book

10:08

in different ways, and this whole sort

10:10

of idea of equations. And so know,

10:13

I guess that would be something that I wondered

10:15

if you thought about, like, whether, you

10:17

know, as you mentioned right up the top that not

10:19

everybody needs to go into deep

10:21

the equations. And so

10:24

guess, you know, do you have any advice

10:26

for people who traditionally have

10:28

been have found equations frightening?

10:30

Like, what was I mean, I guess, or or sort of what

10:32

what was your writing strategy to make

10:35

them more tractable for people, for whom

10:37

they are intimidating? Yeah. Good. Let me I

10:39

definitely wanna answer that. That's crucial question, but

10:41

it reminds me of a related fact that I also wanna

10:43

get on the table, which is that the

10:46

end of my book. Is

10:48

it not a long book? It's pretty short. Two

10:51

fifty pages, something like that. big

10:53

font and etcetera. But

10:56

we do Einstein's equation for general

10:58

relativity. And

11:00

most

11:01

let's say, put it this way, very few

11:04

people who get an undergraduate bachelor's

11:06

degree in physics. And even

11:09

a lot of people who get a PhD in physics,

11:12

Never get that far. Never get

11:14

Einstein's equation for general relativity. They're learning

11:16

other things, and general relativity is sort of

11:18

used by specialists. And

11:20

so even people who are really into

11:22

the equations, because

11:25

if we if we have this paradigm that we're

11:27

teaching you to solve all the equations and

11:29

make a living out of it. There's so many things so

11:31

much work you have to do that you you

11:33

just have to go slowly. And so with

11:35

with this approach in in the biggest ideas,

11:37

we can go very fast, much faster than

11:40

undergraduate physics education would. So

11:42

even if you're into it, this kind of approach pays

11:44

off. but you're asking about the people who are not into

11:46

it so much. And, surely, I do

11:49

try in the book to deploy

11:51

bunches of different strategy There's a lot of

11:53

figures in the book as well as a lot of equations,

11:56

worked hard on those, shout out to Jason

11:58

Toreczynski, friend who is at

12:00

usually an auto writer. He writes

12:03

about cars, but he's also wonderful scientific

12:05

illustrator. And I also

12:08

tell stories. I tell stories. There's

12:10

some jokes in there in the footnotes. I

12:12

love digging into the history of

12:14

this field because it is just amazing

12:16

and and every time I write a new book and

12:19

I I focus in on some particular historical

12:21

event. I learned something about some figures

12:23

that I'd never heard before. My favorite

12:25

for this book was Carolyn

12:29

of Anspah, who was a

12:31

princess in Prussia, and she was

12:33

back in the days of Newton and Liventz in the seventeenth

12:36

century. and she was actually tutored

12:38

by Liventz. But then she married

12:40

the Prince of Wales, the heir to the British

12:43

throne, so she moved to England and fell under

12:45

the spelled of Newton. And liveness was really upset

12:47

by this. And he would write to her and say, like, don't

12:49

fall for what Newton is telling you. And

12:52

but she was very smart. Like, she

12:54

did some of the very first controlled medical

12:56

trials that she arranged and things like that.

12:58

And she

13:01

mischievously sort of set Knewton and

13:03

Liveness against each other writing letters

13:05

back and forth, and and their their

13:07

correspondence, what it's called the Clark LiveNet's

13:09

correspondence because it was actually Samuel

13:12

Clark who was listening to what Newton said and

13:14

then writing letters. This is one of the foundational

13:16

texts in philosophy of science. And

13:19

it's really Carolyn's fault that it ever happened,

13:21

but you never hear her name. So so I

13:23

do hope that telling some of those stories

13:25

humanizes the process along the way.

13:33

Hey,

13:34

electrical contractors. I'm Matt

13:36

from ABB. Our

13:38

rising cost and product delays keeping you

13:40

up at night we can help you

13:43

contractor better. ABB's

13:45

contractor resources are designed to

13:47

help you increase productivity and

13:50

profitability on your commercial construction

13:52

projects. Check out contractor

13:54

better today. Visit

13:56

go dot ABB slash

13:58

contractor better.

14:01

Okay.

14:08

So now now we sort of laid out sort

14:10

of why people should read this book, given them bit

14:12

of a tantalizing, like, there's stuff

14:14

in there that is gonna you so feel so

14:17

happy if you're annoyed with the film gravity and

14:19

various other things. But

14:21

now I wanna talk little bit about some

14:24

of the sort of nuts and bolts. And in particular,

14:27

like, one of the things that I the

14:29

other you haven't mentioned this, but one of the things I

14:31

like about the book is that you also talk about why

14:33

physicists talk like physicists. And

14:37

one of them is the spherical cow.

14:39

So tell us

14:41

the not very funny

14:44

spherical cow joke just so that

14:46

I don't, you know, set up two high expectations.

14:49

So

14:49

the dairy, yes, please. Don't don't let them

14:51

think that there's a much funnier joke in the end of

14:53

the book. If dairy

14:55

farmer wants to improve their

14:59

dairy productivity, milk output.

15:01

And for some reason, they go to the local university

15:04

and go into the physics department rather than

15:06

the biology department, I suppose,

15:08

or the agriculture department. And

15:10

they ask physicists, you know, how do I what do

15:12

I do? And the theoretical

15:15

physicists who happen to be listening, you know, goes

15:17

away and comes back and says, okay, I have it. I

15:19

have a theory for how to improve your

15:21

milk output. And then starts

15:23

with first, a Suma spherical cow.

15:26

That's it. That's the joke. There's really no

15:28

more. I can't make it better. I

15:30

try to make it better. But It's not

15:32

supposed to be funny. What it's supposed to

15:35

do is to illustrate method

15:37

of thinking that both makes

15:39

fun of physicists, but also work

15:41

really well if you're a physicist. You

15:43

know? It won't work if you're

15:45

trying to improve the dairy output of a of

15:47

a dairy farm to assume that the

15:50

cows are spherical. I mean, cows are intrinsically

15:52

not spherical. That's important for what it is

15:54

to be a cow. Once you've made that approximation,

15:56

you're probably too far away from the reality

15:58

of dairy farming to be as much help.

16:01

But there are situations in physics

16:04

where you make kind of that

16:06

big of an assumption, a simplification, and

16:08

it really is helpful. you know, ignore

16:10

air existence. Right? Thinking

16:13

there are only two particles in the universe. Thinking

16:15

the universe is perfectly smooth everywhere. Like,

16:17

these are all crazily wrong

16:19

approximations, but they're really

16:21

really good at giving you physical insight.

16:24

So I coined the term the spherical

16:26

cow philosophy because again and again

16:28

in physics, you can actually make progress

16:31

by simplifying in exactly the right

16:33

way. And the reason why people like Galileo

16:35

or Einstein or Genius is because

16:38

they just had a a sense for

16:40

what parts of a problem were the important

16:43

ones and which parts you could throw away.

16:45

So you're right. I mean, part of the

16:47

book is not just here's a bunch of thoughts

16:49

and equations, but I wanna give you some insight

16:51

into how physicists think.

16:54

So at the end, when we do talk about Einstein's

16:56

equation, I don't just tell it to you.

16:58

I say, well, look, you might have guessed this. Here's

17:00

why that doesn't work. Here's another guess.

17:02

Here's why that doesn't work. More or less

17:04

tracing the reasoning that Einstein himself undoubtedly

17:07

went through. So

17:08

one of the spherical cows

17:10

that I I really enjoyed learning

17:13

about and and helped me understand

17:15

this is the oscillator. So

17:18

tell us a little bit about oscillations.

17:21

And, you know, as a neuroscientist, this something I

17:23

think really important for us to understand because

17:27

neural oscillations are sort of

17:29

one of the big frontiers now that trying to understand

17:31

what they mean in terms of how they relate

17:33

to, you know, brain and behavior and sort

17:35

of how our minds work. So

17:38

tell us a little bit about like, let's

17:40

define what an oscillator is and

17:43

kind of

17:44

what are some of the main physics things

17:46

that we need to know if we wanna understand this a little

17:48

bit more deeply. Yeah.

17:49

It's funny because the phrase simple

17:52

harmonic oscillator means nothing

17:54

to most people, but any physics is will

17:56

just laugh when you say that out loud because simple

17:58

harmonic oscillators are ubiquitous. They're

18:01

literally everywhere around us. I mean,

18:03

the basic idea is you push

18:05

something and there's a force that pushes it

18:07

back. in the direction where it started from,

18:10

but then it comes back and it overshoots.

18:12

So it goes past where you started

18:14

from and then it gets forced back again,

18:16

voila, you have an oscillator. And

18:19

obviously, there's a million different examples lying

18:21

around. The simplest possible one is probably

18:24

a pendulum. you know, a pendulum and

18:26

poke it a little bit or, you know, anything

18:28

falling, chandelier, like suspended

18:30

from a string. Or for that matter,

18:32

in the world of music, plucking

18:34

the string on a musical instrument.

18:36

Right? They vibrate back and forth, and that, therefore,

18:39

it's an oscillator. But of course, all

18:41

of these oscillators are a little bit different

18:43

For the pendulum, it

18:46

will eventually slow down. Right? It'll eventually

18:48

lose energy and stop. Likewise, for the

18:50

violin string or whatever, you know, the

18:52

different violin strings made of different

18:54

materials will sound a little bit different.

18:56

So there are details. There are complications. But

18:59

if you do the spherical cal thing, if you

19:01

simplify it and say, imagine

19:03

that there's no air resistance that we

19:06

poked our us later, our pendulum

19:08

just a little bit that the violin

19:10

string is is absolutely pure, and there's

19:13

no nothing that is

19:15

making it go off note

19:17

or whatever, then it turns out that

19:19

the mathematical description of the

19:21

violin string and pendulum

19:23

is exactly the same. And

19:25

in fact, when you eventually get in book

19:27

two to quantum field theory and you say,

19:30

well, the universe is made of fields

19:32

and those fields guess what? You can poke them

19:34

and they vibrate. and they'll obey the same

19:36

exact equations. So

19:38

sometimes in the world, in the universe,

19:41

you poke something and it moves, And

19:43

basically, there's a set of things that can happen.

19:45

Either it's unstable, it just keeps moving forever,

19:47

like you push a ball down a hill,

19:50

or there's friction and it stops

19:52

or it oscillates. There you go. There's

19:54

not a lot of different possibilities. And so

19:57

it turns out that many, many things in nature

19:59

from quantum fields to pendulums What's

20:02

inside whatever clock you use? If

20:04

you have a mechanical watch, there's a little spring

20:06

that bounces back and forth. If it's a

20:08

electrical cord switch, there's a little

20:10

crystal the vibrates back and forth. And

20:13

like you say, in the brain, in your body,

20:15

your, you know, lots of different parts of you are

20:17

just dangling oscillators back and forth. So

20:19

That's a great example of a

20:21

very very simple system that just keeps

20:23

showing up. And one of the things that I can do in the

20:26

book because you have a little bit of equations under

20:28

your belt by that point is

20:30

show you in the mathematical detail

20:32

why this particular set

20:34

of equations is so applicable over and

20:36

over again. And

20:37

you do something similar to when

20:39

you talk about sort of our conception

20:43

of

20:43

space.

20:44

And so I think that this is something that

20:46

also kind of I think for a lot of

20:48

people conceptualizing space

20:50

and understanding how to work with

20:53

the physics of space can

20:55

be a barrier

20:57

into moving on further. So

20:59

can you give us a little bit of sort of like

21:01

the fundamentals of how

21:04

we should think about the physics of space?

21:06

Yeah.

21:06

Well, you know, look, it's a really good question. And

21:09

it's one of the things that I that I enjoyed

21:11

about the chance to write the book is that

21:14

even, you know, there's lots of books

21:16

without equations that will tell you about

21:18

general relativity and special relativity and

21:20

Einstein's equations, stuff like that. but

21:23

mostly they don't take the

21:25

time to start with what

21:27

is space, what is time, what

21:29

is motion. Right? And Even though my

21:31

book is short, I get to do that, and I talk a little

21:33

bit about the philosophical background and so forth.

21:36

Again, Newton and Livent has argued over

21:38

what space is. There there's a picture

21:40

of space which is probably pretty

21:43

intuitive to most of us today in

21:45

which space is a thing. Space

21:48

is an arena. space is a container

21:50

in which things are located. So you have

21:52

space. And by space, we don't

21:54

mean the final frontier. We don't we don't mean

21:56

outer space. We mean literally the three-dimensional

21:59

world around us with things at different

22:01

locations. And the question is, is

22:03

that three-dimensional world a

22:05

separate thing, in addition to the things

22:08

in it, which is what Newton would have said, Liventz

22:10

would have said, the only things that are

22:12

real are the things,

22:14

not space.

22:15

But if you told me this

22:18

thing is a certain number of centimeters away

22:20

from this other thing, and you told me that list

22:22

of distances literally every set of

22:24

things in the universe, space

22:26

is basically a bookkeeping device.

22:28

It's the relationship between all

22:30

of the things. And so

22:32

to this day in highfalutin

22:35

questions about quantum gravity and the emergence

22:37

of the universe, people argue

22:39

over whether space is a substance

22:42

or a relation. And you

22:44

won't ever read about that in physics textbooks,

22:46

but I thought it was it it lets

22:48

the reader in on why physicists

22:51

think about things in certain ways if you know what

22:53

the alternatives are.

22:54

And to me, I thought it was really interesting too

22:56

that to to find out that now you are

22:59

sort of you have a foot in

23:01

each department, physics, and philosophy.

23:04

And there seemed to be some characteristics

23:07

of, like, the conversations I overhear amongst

23:09

physicists that, you know, are similar

23:11

to the conversations I hear from philosophers,

23:13

but coming from very different backgrounds

23:16

or or sort of, you know, foundations. So

23:19

I wonder if you could talk a little bit about that. Like, what

23:21

it what is it like? What when you talk to your

23:23

philosophy colleagues, how is that different

23:25

from when you talk about your theoretical physics

23:27

colleagues?

23:28

It's a fascinating

23:29

question. It's really, really interesting to me. Like, someone

23:31

tried to about this, not me. But

23:34

both physics and philosophy in their different

23:36

ways, parts of them, not not the whole

23:38

parts, but parts of these two fields are

23:41

devoted to figuring out the ultimate

23:43

questions. What is the universe made of?

23:45

How does it work? Why is it there? Where did

23:47

it start? All of these questions. Right?

23:50

But the way they do it is pretty different. And

23:52

what's interesting is there is an

23:54

overlap. So when

23:56

I first discovered philosophy, I

23:58

was an undergraduate, I knew that there was philosophy

24:00

of physics, but mostly it was

24:03

how are theories invented, and

24:05

how do we decide, and what is science, and

24:07

what is not science. There are methodological questions.

24:10

I

24:10

didn't know that there's a whole extra

24:12

group of philosophers

24:13

who are doing what is called

24:15

foundations of physics. And they're

24:17

really asking questions about the universe. They're not asking

24:19

questions about science. They're saying, you know, what happens

24:22

when a quantum measurement occurs? What

24:24

does it mean to have singularity? Why is

24:26

the past different from the future? You know, things

24:28

like that? And those are big

24:30

questions that philosophy has to say something

24:33

about and so does physics. But the

24:35

interesting thing is in the

24:37

history of academia, we have

24:39

decided that these are two different fields. philosophy

24:42

and physics are not even in the same school.

24:45

Right? There's the humanities or arts and sciences,

24:47

I guess, arts and humanities, and

24:50

then there's the natural sciences that there's

24:53

usually a different Dean is in charge of both

24:55

departments. Right? And so

24:57

therefore, the philosophers end up talking

24:59

to other philosophers and the physicists end up

25:02

talking to other physicists. And so even though

25:04

they are motivated by very similar questions.

25:06

They don't talk to each other nearly as

25:08

much as they could. So I'm

25:10

I'm very happy that here at Johns Hopkins

25:12

were actually the devoted to overcoming

25:15

that barrier a little bit. We started

25:17

a new forum on natural philosophy,

25:20

borrowing the terminology back from Isaac

25:22

Newton and and LLAO, philosophy

25:25

that is really informed by dialogue

25:28

with nature, by experiment and observation

25:30

and trying to move forward. So I

25:32

do think that even though both sides

25:34

are used to talking to other people in other

25:36

ways, the philosophers are

25:38

much more likely to be talking about the nature of

25:40

rationality, the are much more likely

25:42

to do a scattering calculation, there

25:46

is still more than enough overlap for them to get

25:48

together and and converse. mean,

25:49

to me, well, what what's kind of fascinating

25:51

too is that, like, you you have, like, over the last

25:53

year, right, that, you know, a couple hundred

25:56

years ago, the philosopher and the physicist

25:58

especially the theoretical physicist was

26:00

often the same person or, you know,

26:03

that that, ma'am. And then as, you

26:05

know, I DMEA sort of created these separate departments.

26:07

They they sort of went in very separate

26:09

directions in in some ways,

26:11

I think. At least in terms of, like,

26:14

who wins the argument? Like, what

26:16

what makes, you know, a good

26:18

philosophical argument versus a good

26:20

theoretical physics argument? And

26:22

so I wonder if if if you have any thoughts

26:25

about, like, how to how to bring

26:27

those two fields closer together

26:29

so that we do get to some

26:31

higher truth about, you know, some of these big

26:33

questions. Yeah,

26:34

you know, I'm teaching a course right now

26:37

on topics in the philosophy of physics. And

26:39

so I'm just go forces you to systematically

26:42

go through and read what other people say and, you

26:44

know, look at the big questions rather than just

26:46

do your own research. And I, you know,

26:48

I gotta say, as fascinating as these questions

26:50

are and as brilliant as some of the people are who talk

26:53

about them, there's a lot of silly

26:55

things that are being said in the

26:57

academic literature about these very important

26:59

questions. And you can see why for

27:01

different reasons. On the philosophy side,

27:03

you can get away with not

27:05

confronting our best current

27:08

theories of reality. You can

27:10

sort of work in a tradition where there's

27:12

certain questions that are considered to be interesting

27:14

and certain words that are considered to be meaningful

27:17

and just stay in that tradition and sort of

27:19

never get shaken out of your dogmatic slumbers

27:21

by a new discovery or something like that.

27:23

Right? On the physics side,

27:25

you can just be perfectly happy getting

27:28

a good enough answer from a calculation

27:30

to make a prediction even though some of the

27:32

assumptions that went into that calculation are completely

27:34

nonsensical. And this

27:36

kind of problem really lurks in a lot

27:38

of areas of fundamental physics today.

27:41

And the thing about physics is we're

27:43

not done. Like, we we we we don't

27:45

have all the answers. So the

27:48

fact that we're not being

27:50

careful even in the answers we think

27:52

we have, I think is like an obvious room

27:55

for improvement situation. Because

27:57

maybe thinking about these foundations and

27:59

making sure we get the arguments right

28:02

will improve our understanding of

28:05

the emergence of spacetime in quantum gravity

28:07

in the origin of the universe, in the nature of time

28:09

in all of these questions that even physicists think

28:11

are perfectly respectable ones to think about.

28:13

Well,

28:14

if anyone can can draw

28:16

these two fields closer together and

28:18

get some answers on these big questions. It's you.

28:20

So I'm glad that that is on

28:22

your shoulders. Thank you very much.

28:24

So I wanna remind our listeners that

28:26

Sean Carroll's new book, the biggest ideas in

28:28

the universe, space time and motion,

28:31

part one, I should say, the biggest

28:33

ideas in here for part one, is

28:35

now available booksellers everywhere. And

28:37

Sean do not pull a George r r

28:39

Martin on us. Book

28:41

three better come out before the,

28:44

like, you know, HBO series.

28:46

If I if I have an HBO series, I

28:48

might just resign so that that makes perfect

28:50

sense. So You should tell the people

28:52

at HBO not to sign me up for

28:54

a multi season deal. Okay. Great.

28:56

Great. Well, thanks so much for coming back on

28:58

inquiring minds and chatting with us about your book.

29:01

Thanks, Andre. Anytime you want me, I'm here. Thanks.

29:06

So that's it for another episode. Thanks

29:08

for listening. And if you wanna hear more, don't forget

29:10

to subscribe. If you'd like to get an ad free

29:12

version of the show, consider supporting us

29:14

at patreon dot com slash inquiring

29:17

minds. I wanna especially thank David

29:19

Noelle Haring Chang, Sean Johnson,

29:21

Jordan Miller, Kaia Brehala, Michael

29:23

Galgule, Eric Clark, Yuchy

29:25

Lynn, Clark Lindgren, Joelle, Stephen

29:28

Meyer, Eyewall, Dale Lemaster, and Charles

29:30

Blime. Inquiring

29:31

Mines is produced by Adam Isaac,

29:33

and I'm your host, Indreyvus Contus.

29:35

see you next time.

29:57

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29:57

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