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56-2-3-3-1-6-6-2 3-3-4 for details. Hello

0:59

everyone, welcome to the March 2025

1:01

Ask Me Anything edition of the

1:03

Mindscape podcast. I'm your host Sean

1:05

Carroll. Before diving in to the

1:07

AMAs, I want to mention two

1:09

announcement kind of things, not really

1:11

announcements, two things, one announcement and

1:13

one reflection, if you want to put

1:15

it that way. The announcement is,

1:17

we have winners for this year's

1:19

Mindscape Big Picture Scholarship. I hope I've

1:22

been flogging this enough, probably I

1:24

haven't, but this has been going

1:26

on for a few years now.

1:28

It's at bold.org, so it's going

1:30

to keep going on. It's

1:32

not ended, so you can

1:34

still contribute. We solicit donations

1:36

from mindscape listeners to help

1:38

undergraduate university students achieve their

1:40

dreams of studying big picture

1:42

ideas down the road. So

1:44

this is hosted by bold.org,

1:46

which has scholarships and all

1:48

kinds of things. If you

1:51

go to bold.org/scholarships slash mindscape,

1:53

you can find hours and

1:55

contribute to it. You can

1:57

just go to our podcast

1:59

homepage. proposterousuniverse.com/podcast. In the right hand

2:01

column, there's a link that says

2:03

Minescape Big Picture Scholarship. Click on

2:05

it and you get all

2:07

the info. So we've been super

2:09

successful. Thank you so much for

2:11

contributing. We've been very successful at

2:14

getting donations so much so that

2:16

each year the current plan

2:18

is we can give two scholarships

2:20

worth $20 ,000 each, which is

2:22

not enough to send someone to

2:24

college entirely, but makes a big

2:26

difference to someone who's just trying

2:28

to pay that tuition for school,

2:30

especially if you're not

2:32

planning to go in some

2:35

area that is super

2:37

financially remunerative down the road.

2:39

And I'm very happy

2:41

to announce this year's winners.

2:43

One winner is Jillian

2:45

Kate from, she's already a

2:47

undergraduate enrolled at Auburn

2:49

University and she's studying biochemistry,

2:51

biophysics, molecular biology with

2:53

the goal of becoming a

2:55

college professor and doing

2:57

research in those areas. And

2:59

one line that caught my eye

3:01

from her application was that she's already

3:03

planning not only to be a

3:05

professor, but what kinds of courses she's

3:07

going to teach as a professor.

3:09

So Jillian says, my goal is to

3:11

one day teach biology in a

3:13

southeastern university. And when I teach introductory

3:15

courses, I hope to intertwine creativity,

3:17

philosophy and art into my lectures and

3:19

course content. That certainly sounds something

3:21

like something we could use more of

3:23

in academia. So I'm all in

3:25

favor of that. Other winner is Miles

3:27

Webb, who is a senior in

3:29

high school and looking at different universities

3:31

to go to wants to study computer

3:33

engineering, material science, chemistry and physics.

3:35

And one of the lines in his

3:38

application was a dream of mine

3:40

is to become the first black Nobel

3:42

Prize winner in physics. Part of

3:44

me says, you know, I hope you're

3:46

not miles because I hope someone

3:48

else is even before you get there.

3:50

But if miles is the first

3:52

black Nobel Prize winner in physics, I

3:54

hope he gives a shout out

3:56

to mindscape listeners in his Nobel Prize

3:58

acceptance speech because because we have

4:00

given them a little bit of

4:02

a boost in paying for that

4:04

college education along the way. Again,

4:06

very many sincere thanks to all

4:08

the listeners because you are the

4:10

ones who contribute and it really

4:13

does make a difference to students,

4:15

especially in times of uncertainty when

4:17

it comes to higher education, scientific

4:19

research, things like that. The other

4:21

announcement, which is not an announcement

4:23

but a little reflection, is that

4:25

in last week's episode, I did

4:27

the theory of cocktails with Kevin

4:29

Peterson, a bit of a

4:31

change of pace, but we're allowed to

4:33

have fun here at the podcast. We

4:35

don't to be serious all the time.

4:37

And the thing we did at

4:39

the end of the podcast, if you'll

4:41

remember, is that we invented on the

4:44

spot, I say we, but it was

4:46

really Kevin, invented a Minescape cocktail, the

4:48

Minescape Petricor Negroni. Petricor is a word

4:50

having to do with that smell

4:52

in the forest after it rains. So

4:54

Kevin came up with a great idea,

4:56

except that it was difficult to pull

4:58

off for the typical home bartender. Negroni,

5:00

for those of you who

5:02

don't know, is one part

5:05

gin, one part something Campari

5:08

-esque, something bitter like that, and amaro,

5:10

I guess, in general. And then

5:12

one part sweet vermouth, red vermouth. So

5:14

the specific ingredients that matter is,

5:16

you know, what kind of gin, what

5:18

kind of vermouth, what kind of

5:20

amaro do you use? And Kevin came

5:22

up with Antica Formula Vermouth, which

5:24

is a very standard, you know, it's

5:26

one of the ones you can

5:28

easily get, typically, in the liquor

5:31

stores. It's what I generally use

5:33

when I'm using that kind of

5:35

vermouth in cocktails. For the amaro,

5:37

he suggested St. George Bruto Americano,

5:39

which I'd never heard of. St.

5:41

George, I knew quite well as

5:43

a gin producer, and I didn't

5:45

know that they made sort of

5:47

a Campari substitute. But now I

5:49

do, and it's amazing. It's really,

5:51

really wonderful. It's a little bit

5:53

smoother than real Campari. Opera roll

5:55

is the other thing that people

5:57

often substitute for Campari. But I

5:59

like the same. Georgia's brutal Americano better than

6:01

either one of them. So that's a

6:04

real discovery. And it does have that

6:06

little bit of herbaceousness in it that

6:08

we were looking for in our cocktail.

6:10

But then for the gin, Kevin's suggestion

6:13

was to distill our own gin from

6:15

vetiver, which is a type of grass

6:17

that is. hard to find. It's in

6:19

Haiti and maybe in India, something like

6:21

that. It's not easy to find a

6:24

vetiver. It's also not easy to distill

6:26

your own gin. So I'm not at

6:28

that level of cocktail wizardry. And I

6:30

asked him for maybe an off-the-shelf replacement

6:33

option. So he suggested moletto. gin, which

6:35

I had not been aware of, and

6:37

now I am. So I actually, when

6:39

we did the podcast and I recorded

6:42

the intro, etc., I hadn't made the

6:44

cocktail, but now I have, and I'm

6:46

here to report to you that it

6:49

was very good. So the issue with

6:51

the mulleto gin is the gimmick that

6:53

they have. You know, gin is sort

6:55

of flavored. Vodka, flavored neutral spirit of

6:58

some sort, and the flavors are supposed

7:00

to be various botanicals, largely juniper, but

7:02

then the individual character of the gin

7:04

comes from exactly which botanicals you use.

7:07

And Moleto uses tomatoes, among other things,

7:09

to flavor their gin. And I got

7:11

a say, I didn't say it to

7:14

Kevin in the moment, but I was

7:16

instantly thinking and was still thinking, that

7:18

sounds terrible. Like, I like tomatoes in

7:20

the right context, but in gin might

7:23

not be that context. And when I

7:25

got it, I managed to, you know,

7:27

shake up a bottle and it arrived

7:29

and indeed, it's not mostly made of

7:31

tomatoes, it's made of some grain, but

7:34

then there's a tomato essence in there

7:36

and you open it up and it

7:38

kind of smells like tomato juice. Like

7:40

it's a very noticeable tomato smell. And

7:42

I was very skeptical about this, but

7:44

I thought, you know, look, he knows

7:46

what he's doing. I bet this is

7:48

one of those things that when you

7:50

put it into the cocktail, it's not

7:52

going to smell to me at all.

7:54

It's going to be mixed in in

7:56

a particular way. And indeed, that's exactly

7:58

what happened. So I don't know. whether

8:00

I would drink Moleto gin straight.

8:02

I haven't tried yet. Maybe it

8:04

would be good in the right

8:07

circumstances with a grilled cheese sandwich,

8:09

perhaps. I really don't know. But

8:11

in the cocktail, it was very

8:13

good. And it did, in fact,

8:15

completely satisfy the requirements of giving

8:18

you that foresty, piney, herbaceous kind

8:20

of feel. In fact, maybe I

8:22

could add a drop of my

8:24

pine. bidders that I got on

8:26

the shelf there. Maybe that could

8:29

like juiced up a little bit.

8:31

Anyway, I can give a positive

8:33

recommendation to the Mindscape Petricor Negroni.

8:35

I think that it works. For

8:37

those of you who are into

8:40

that kind of thing. I would

8:42

hesitate to try to come up

8:44

with a mocktail version, but it

8:46

would definitely involve tomato juice somehow,

8:49

which I don't know whether that

8:51

would be a good thing. Anyway,

8:53

many thanks as always to Mindscape

8:55

listeners, especially patron supporters. The monthly

8:57

AMA is supported by patron supporters,

9:00

if you join on patron.com/Sean M.

9:02

Carroll, then you get ad-free versions

9:04

of the podcast, and you get

9:06

to ask questions for the AMAs,

9:08

and you get my little tiny

9:11

reflections after each episode. As usual,

9:13

too many questions to answer all

9:15

of them, but they're all good.

9:17

Keep asking them. Someone said, like,

9:19

can we keep asking questions even

9:22

if we if we tried once

9:24

and didn't get selected? Can we

9:26

ask the next question the same

9:28

question next time? Absolutely yes. I

9:30

mean, it might even slightly increase

9:33

your chances of getting selected. You

9:35

know, I do. Try to select

9:37

questions that are new to me,

9:39

that have something interesting to say

9:41

about, that are relatively short, that

9:44

I think will be interesting to

9:46

listeners. So there's a lot of

9:48

criteria that go in there, even

9:50

some really good questions I can't

9:52

answer just because of bandwidth reasons.

9:55

But I appreciate your understanding in

9:57

that matter. And with that, let's

9:59

go. Julian

10:07

Mark starts us off with a priority

10:10

question. Remember that priority questions are ones

10:12

that patron supporters are allowed to ask

10:14

once. per their lifetime, at least, you

10:16

know, their initial lifetime here on Earth,

10:19

who knows, with cyclic universe models, and

10:21

I will try my best to answer

10:23

it. So, sometimes that best is okay,

10:25

sometimes it's not, but, you know, that's

10:27

the risk that you run here. The

10:30

question is, if I were floating somewhere

10:32

between our sun and the closest star,

10:34

would I be able to see my

10:36

own hands? In other words, are the

10:38

stars in our galaxy bright enough to

10:41

illuminate any object in interstellar and, if

10:43

you're right? next to it. Well, this

10:45

is a question more about your ability

10:47

to see, or at least as much

10:50

about your ability to see as it

10:52

is about astronomy, so I don't actually

10:54

know the answer. My suspicion is it

10:56

would look pretty dark to you. It's

10:59

not that much different than just saying

11:01

what What do things look like if

11:03

you're outside on a clear moonless night

11:05

in an area where there is no

11:08

artificial illumination, right? You can certainly

11:10

see stars. In fact, you can

11:12

see the Milky Way galaxy surrounding

11:14

you. It would be kind of

11:17

cool, but that's probably not enough

11:19

to reflect light off of your

11:21

hands and see them unless your

11:23

vision just is really, really good,

11:25

I suppose. That's my guess. James

11:27

Heath says, I really enjoyed your solo

11:30

episode on science funding specifically when you

11:32

said that the current administration is not

11:34

thinking seriously about what they're cutting. Do

11:36

you think we need to touch the

11:38

hot stove and suffer consequences to remember

11:40

why government funding of science vaccines, alliances

11:42

with Europe really matter? I want to

11:44

know where this... phrase of touching the

11:46

hot stove came from, like suddenly it's

11:49

everywhere on the internet, like I guess

11:51

I can figure out what it means,

11:53

but it just suddenly appeared in all

11:55

my social media feeds all at once.

11:57

I don't know where it came from. Well,

11:59

you know... Do we need to do

12:01

that? No, we should be smart

12:03

enough to know that funding science

12:05

vaccines and protecting alliances with Europe

12:08

really matter. That should not be

12:10

something we need to... test and

12:12

remember like, oh yes, these things

12:14

actually solved real problems that we

12:16

faced with. All the evidence you

12:18

need that the cutting is not

12:20

being done in any sensible way

12:23

comes from the fact that so

12:25

many things have been cut and

12:27

then uncut. So many people have

12:29

been fired and then rehired right

12:31

away. So much damage has been

12:33

done and to important things with

12:35

respect to health and science and

12:37

national defense and national security that

12:39

they're clearly not. paying attention. The

12:42

most recent one was they put

12:44

up for sale a building that

12:46

is used by the CIA for

12:48

secret operations that was supposed to

12:50

be secret. I mean it's not

12:52

the best secret in the world

12:54

but you know they just listed

12:56

it for for soon being sold

12:58

by the General Services Administration. You

13:00

know, they're very excited about cutting things, but

13:02

they're doing enormous damage. It's like saying, you

13:05

know, you know you have a tumor in

13:07

your body, so I'm just going to start

13:09

cutting things open and taking things out. Eventually

13:12

we'll find that tumor. No sensible person thinks

13:14

that this is the right thing to do.

13:16

And part of it is that... You might

13:18

think, well, if you make a

13:20

mistake, we'll just fix it, but

13:23

some of these things are not

13:25

fixable. The United States is supposed

13:27

to have a reputation as a

13:29

relatively reliable international partner. All that

13:31

talks about tariffs being put on

13:33

and then taken off has done

13:36

irreparable damage to that reputation that

13:38

we've had. People in Europe and

13:40

in Asia and elsewhere are absolutely

13:42

realizing that they cannot rely on

13:44

the United States for protection for

13:47

military support. or anything like that,

13:49

so they're gonna have to beef up

13:51

their own defenses. And there's a certain

13:53

attitude that says, well, they should defend

13:55

themselves, but you know, as far as

13:57

the United States is concerned, it really.

14:00

serves the United States' interest to

14:02

be in charge of all that,

14:04

because they might not always agree

14:06

with decisions that other places make.

14:08

I mean, maybe a multipolar world

14:10

is better in some ways. I

14:12

absolutely could see the argument for

14:14

that. The real, very obvious, huge

14:16

disadvantage to me is that some

14:18

of these other countries are going

14:20

to develop nuclear weapons. And the

14:22

more countries that have nuclear weapons,

14:24

the worse we are. worse we

14:26

all are because the greater chance

14:28

that someone uses them either intentionally

14:30

or by mistake or they lose

14:32

it or whatever. So none of

14:34

this is good. It's all bad

14:36

and it's not something that is

14:38

going to be easy to fix.

14:41

Dennis Cooperberg says, in the big

14:43

picture a crucial claim is made.

14:45

The laws of physics underlying everyday

14:47

life are completely known. This strikes

14:49

me as both highly plausible and

14:51

surprisingly almost never mentioned elsewhere. How

14:53

widely accepted would you say this

14:55

claim is among physicists or more

14:57

generally among those well-versed in modern

14:59

physics? Well, I've said this before,

15:01

but basically, when I explain the

15:03

claim to my fellow physicists, they

15:05

think for about five seconds and

15:07

go, yeah, I guess that's true.

15:10

So I don't think it's something

15:12

that they think about. You know,

15:14

scientists are kind of laser focused

15:16

on pushing beyond what we already

15:18

know into regimes that we don't

15:20

yet understand. So the typical theoretical

15:22

particle physicists spend their time thinking

15:24

about amplitudes or supersymmetry or. brains

15:27

or hidden symmetries in quantum field

15:29

theory or quantum gravity or whatever it

15:31

is, things that we don't understand very

15:33

well. So, and also of course the

15:35

fact that we understand the laws of

15:38

physics well enough doesn't really have a

15:40

huge impact on the higher emergent levels,

15:42

whether it be chemistry or biology or

15:45

whatever. It has some impact because you

15:47

might otherwise... wonder whether you're when you

15:49

know studying a chemical reaction and it

15:51

doesn't happen at the rate that you

15:54

expected it to if you didn't know

15:56

about underlying laws of physics you might say

15:58

well oh maybe there's like a a new particle

16:00

or a new field somehow involved that

16:02

is changing the reaction rates. That is

16:05

not the way to go, given what

16:07

we understand about effective field theory. So

16:09

instead, people look for much more mundane

16:12

chemical reasons for those kinds of things

16:14

and they find them. So I think

16:16

it is something that is not controversial

16:18

in the sense that there's a lot

16:21

of people out there who deny it

16:23

within the physics community, but it's not

16:25

also something that people think about that

16:27

much. And again, as I should always

16:30

add, it's, it could, it might not

16:32

be true, right? That's, I always try

16:34

to phrase it as, given everything we

16:37

know, this is absolutely what is the

16:39

most sensible thing to believe as good

16:41

basians, but who knows, you know, we

16:43

could be missing something deep. in quantum

16:46

mechanics. I don't think that that's a

16:48

very likely place to find anything new,

16:50

but other people disagree about that.

16:52

Radolfo Hansen says, I've heard you

16:55

speak positively about capitalism in the

16:57

past. Given increasing evidence in forcible

16:59

cooperative frameworks, outperform their competitive counterparts,

17:02

would you consider alternatives allow us

17:04

to step away from the negative

17:06

some game we are currently running

17:08

to a positive someone? Well, lot

17:11

to unpack here. I don't know

17:13

what that evidence is that you're

17:15

pointing to the increasing evidence about

17:18

enforceable cooperative frameworks. I'm not exactly

17:20

sure what is meant by enforceable

17:22

cooperative frameworks. I will certainly consider

17:24

alternatives. I'll always consider alternatives, but

17:27

I do think a lot of

17:29

alternatives are sort of influenced by

17:31

wishful thinking or by unrealistic expectations.

17:33

Capitalism, I think, is very very

17:35

effective at certain things, very very

17:37

harmful in other ways, and I'm

17:40

in favor of fixing it and

17:42

ameliorating the bad effects rather than

17:44

trying something completely different until we

17:46

really do get evidence that something

17:48

completely different would be better. Finally,

17:50

I don't quite agree with the

17:53

negative some game versus positive some

17:55

game. Like, there's no reason intrinsically

17:57

why capitalism has to be negative

17:59

some... game. Indeed, I think that

18:01

one could easily make an

18:03

argument that standards of living and

18:06

health and other very basic

18:08

measures have improved over years, even

18:10

for most of the less

18:12

well -off people in capitalist societies.

18:14

Not to undersell any of the

18:16

real problems under capitalism, but

18:18

there's no, again, intrinsic reason why

18:21

it's a negative sum game.

18:23

The whole idea is that you

18:25

incentivize people to be productive

18:27

and productivity makes everybody better off.

18:30

So I think that capitalism

18:32

plus a very strong taxation

18:34

and social safety net system

18:36

would actually be very obviously

18:39

positive sum. This

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-L -p.com/Mindscape. Okay

19:45

we have two questions I'm gonna group

19:47

together. They're both a little vague

19:49

so maybe that's a good reason to

19:51

group them together. One is from

19:53

Yazan al -Hajari who says, Kepler wrote,

19:55

metaphors are my truthful masters. One should

19:58

make good use of them. In

20:00

science, metaphors shape our understanding black

20:02

holes as cosmic sinks, entropy is

20:04

disorder, just as thought experiments stretch

20:06

logic to reveal deep truths. Science

20:08

fiction blends both inspiring real discoveries.

20:10

How do you see the role

20:12

of metaphor and thought experiments in

20:14

science? Are they essential tools for

20:16

discovery? Or should we be cautious

20:18

of their limits? And has any

20:20

metaphor, thought experiment or sci-fi story

20:22

ever influenced the way you think

20:24

about physics? And then Nanou asks...

20:26

When you were learning physics or

20:28

cosmology over the years, did you

20:30

incorporate your imagination? If you did

20:33

and still do when you think

20:35

about those ideas, what images does

20:37

your brain generate? So to take

20:39

the second question first from NANU,

20:41

I mean, yeah, you definitely incorporate

20:43

your imagination. I might hesitate here

20:45

because maybe you mean something different

20:47

by incorporating one's imagination than I

20:49

might mean. imagination is that just

20:51

a supernupor important part of all

20:53

of science because you're trying as

20:56

we just mentioned to push beyond

20:58

what we know to suggest ideas

21:00

for doing better than our current

21:02

theoretical models do and that is

21:04

a fundamentally act. So you say,

21:06

what images does your brain generate,

21:09

implying that imagination is somehow associated

21:11

with images in the brain? That's

21:13

one kind of imagination, but there's

21:15

other kind of imagination. You can

21:17

imagine equations. You can imagine structural

21:20

relations between different parts of the

21:22

physical world or something like that.

21:24

So imagination is absolutely centrally crucial.

21:26

And indeed, we don't understand it.

21:28

very well. We don't really understand

21:31

how it is that the human

21:33

brain comes parts of the physical

21:35

world or something like that. So

21:37

imagination is absolutely centrally crucial and

21:39

indeed we don't understand it very

21:41

well. We don't really understand how

21:43

it is that the human brain

21:45

comes up with hypotheses scientifically and

21:48

this is becoming a more directly relevant

21:50

question in the age of AI where you

21:52

might say, well I'm going to... Imagine building

21:54

an AI that will do science in the

21:56

same way that theoretical physicists do, and we

21:59

don't really know how. don't even really

22:01

have any expectations for whether that's

22:03

easy or hard or whatever so

22:05

it's becoming a very down-to-earth kind

22:07

of question. For Yuzan's question you

22:09

know what is the role of

22:11

metaphor and thought experiments it's super

22:13

crucial as a matter of empirical

22:15

fact so I don't necessarily think

22:17

that it's you need to have

22:19

thought experiments or metaphor. I could

22:21

imagine a kind of science that

22:23

was just much more straightforward and

22:25

literal, but I don't think it

22:27

would be as productive, at least

22:29

for we human beings. We human

22:31

beings definitely think in terms of

22:33

images and metaphors. I mean, one

22:35

that I like to use is

22:37

when I talk about Hilbert space,

22:39

the space of all possible quantum

22:41

states of a system in very...

22:43

commonly thought of examples. Hilbert space

22:45

is a vector space that is

22:47

infinite dimensional. In some very realistic

22:49

examples, it's still very, very big,

22:51

right? Ten to the ten to

22:53

the hundred dimensional or some crazy

22:55

number like that, right? So there's

22:57

no possible way that any human

22:59

being can actually visualize all of

23:01

those dimensions of Hilbert space in

23:03

their head. And yet we visualize

23:05

a little bit and we use

23:07

tools like reducing the number from

23:09

infinity to three. the number of

23:11

dimensions of Hilbert space, and we

23:13

make a little picture of it,

23:15

like a three-dimensional vector space. That's...

23:17

Not really a metaphor, it's just

23:19

a sort of a simplification. It's

23:21

helpful in some ways, and it's

23:23

misleading in other ways because things

23:25

become different when you have a

23:27

very very large dimensional vector space

23:29

compared to a very very small

23:31

dimensional vector space. But it's absolutely

23:33

crucial for most of us. Others,

23:35

maybe it's not crucial. Like maybe

23:37

you just memorize the rules of

23:39

a vector space. You say, oh,

23:41

a vector is helpful in some

23:43

ways. and it's misleading in other

23:46

ways because things become different when

23:48

you have a very very large

23:50

dimensional vector space compared to a

23:52

very very small dimensional vector space.

23:54

But it's absolutely crucial for most

23:56

of us. Others, maybe it's not

23:58

crucial. Like, maybe you just memorize

24:00

the rules of a vector space.

24:02

You say, oh, a vector is

24:04

something you can add to other

24:06

vectors and scale by real numbers

24:08

or complex numbers or something like

24:10

that. Everyone who understands vector spaces

24:12

knows those rules, but what I'm

24:14

saying is maybe someone only knows

24:16

those rules and doesn't ever think

24:18

about vectors as little arrows, right?

24:20

That would be fine. You could

24:22

do it that way. I always

24:24

think that science is something that...

24:26

benefits from a diverse set of

24:28

approaches, because the space of possible

24:30

ideas is very, very large, and

24:32

no matter how brilliant you are,

24:34

if you sort of have your

24:36

particular way of moving forward in

24:38

the space of ideas, you're bound

24:40

to miss some good ones. We're

24:42

all bound to miss some good

24:44

ones, and that's why you need

24:46

lots of people with lots of

24:48

different kinds of ideas, and you

24:50

need to support them, even though

24:52

they're not doing things exactly the

24:54

way that you want to be

24:56

doing them. And that is the

24:58

difficult thing to do. Are there

25:00

any metaphors, thought experiments, ever influencing

25:02

the way I think about physics?

25:04

I mean, sure, but I would

25:06

separate out those three things. Those

25:08

are very different things. Metaphors, thought

25:10

experiments, sci-fi stories. I don't think

25:12

that sci-fi stories have really influenced

25:14

the way I think about physics.

25:16

Maybe the closest is, you know,

25:18

time travel stories that tried to

25:20

make everything completely logically consistent. provide

25:22

a nice way to think about

25:24

that, because I do think that

25:26

if time travel were possible, it

25:28

would be logically consistent. It's not

25:30

a major part of my scientific

25:32

research, though, so most other science

25:34

fiction stories do not talk about

25:37

the kinds of science that I

25:39

personally am invested in. For thought

25:41

experiments, yes, I mean, thought experiments

25:43

are everything. We're always doing sort

25:45

of spherical cows, you know, imagining

25:47

if this is true, then what

25:49

would happen? That's really the bread

25:51

and butter of what theoretical physicistsists

25:53

do for a living. metaphors it's

25:55

harder you know we I'm always

25:57

skeptical of metaphors. You know, many

25:59

of you will know my long-standing

26:01

antipathy for thinking of the universe

26:03

as a balloon being blown up.

26:05

That's a metaphor, right? You know,

26:07

take a balloon, put some dots

26:09

on it with a marker, blow

26:11

it up, and say, oh look,

26:13

it's kind of like the expanding

26:15

universe, and the dots are moving

26:17

apart from each other like galaxies

26:19

are, which is... explaining something correctly,

26:21

but also getting other things very

26:23

very wrong. In that picture of

26:25

the balloon blowing up, not only

26:27

do the dots get further away

26:29

from each other, the individual dots

26:31

get bigger. and individual galaxies don't

26:33

get bigger. When you're blowing the

26:35

balloon up there is an obvious

26:37

inside and outside and in the

26:39

universe there is not. So you

26:41

can use metaphors and they're very

26:43

helpful but they are all so

26:45

dangerous and so you got to

26:47

keep your what's about you understanding

26:49

exactly what the limitations of the

26:51

metaphor are supposed to be. Mark

26:54

Sleight says, how should a layman

26:56

understand the temperature of the cosmic

26:58

microwave background radiation? Is this the

27:00

temperature a thermometer in space would

27:03

show? If it only absorbed the

27:05

microwave background and no other photons

27:07

or particle collisions? Yes, that's exactly

27:09

what it is. I mean, that

27:11

is more or less what we

27:13

measure. We have a telescope. Here

27:15

on Earth, we have a radio

27:18

telescope, right? Like, I mean, the

27:20

original one, it was in New

27:22

Jersey, but now we have more

27:24

advanced telescopes, but it's not that

27:26

hard, if you know what you're

27:28

doing, to go up on the

27:30

top of a building in your

27:32

random urban area in the United

27:35

States and put up a telescope

27:37

that can detect the cosmic microwave

27:39

background. And not only do you

27:41

detect detect photons in the radio

27:43

band coming from the CMB, but

27:45

you can, if you're good, measure

27:47

the spectrum. and the spectrum takes

27:50

the form of a black body

27:52

with a certain temperature. So that's

27:54

the temperature. It really is literally

27:56

what you're doing. Even though there

27:58

are other photons there, you build

28:00

a detector that is not sensitive

28:02

to the other photons, only to

28:04

those in a certain direction and

28:07

in a certain wavelength range, and

28:09

you detect the CMB, and you

28:11

figure out its temperature. It's really

28:13

just gas of photons bumping into

28:15

you. Anonymous says, I think democracy

28:17

only makes sense for groups of

28:19

people who share a common ontology.

28:22

If the primary concern of one

28:24

group is to secure themselves an

28:26

entrance ticket to a type of

28:28

heaven, the other group does not

28:30

believe in. The minority group needlessly

28:32

suffers. A decision between building a

28:34

dam or an airport with a

28:36

limited budget can effectively be guided

28:39

by the outcome of a popular

28:41

vote, whereas a decision on abortion

28:43

rights hinges on whether a fetus

28:45

has a soul. Given that a

28:47

majority of the population is unwilling

28:49

to reassess their ontological commitments, the

28:51

divide often results in a hostage

28:54

situation. What are your thoughts on

28:56

this? Well, I think this is

28:58

a real and very well-known problem

29:00

in democracy. We've discussed it before

29:02

on the podcast, the idea that...

29:04

A democracy is supposed to allow

29:06

for people with different value systems

29:08

to coexist together, but their value

29:11

systems have to overlap enough to

29:13

make democracy work. And in the

29:15

case of abortion or something like

29:17

that... Well, let's just try to

29:19

be the more general principle here.

29:21

In the case where someone, two

29:23

sets of people, have very different

29:26

ideas about the morality, the sort

29:28

of fundamental morality of some kind

29:30

of action, this is where democracy

29:32

is always going to get in

29:34

trouble. It's not that it can't

29:36

work, right? Like, whether it's abortion

29:38

or the death penalty or going

29:40

to war with some other country,

29:43

you can personally say, look, I

29:45

don't believe in the moral correctness

29:47

of this. I do, however, believe

29:49

in the democratic process. So what's

29:51

going to happen is I'm going

29:53

to accept that the democratic process

29:55

has led to an outcome that

29:58

I don't like, and I'm going

30:00

to protest it, and I'm going

30:02

to vote against it, and I'm

30:04

going to try to convince other

30:06

people on the other side to

30:08

come to my side, but that's

30:10

the best I can do, because

30:13

I'm part of the democracy, and

30:15

I'm subject to decisions that democracy

30:17

makes. That is inevitable, and I

30:19

think that we can easily imagine

30:21

groups of people who would not

30:23

work well, who would not function

30:25

in a functioning democracy together. You

30:27

have to imagine that the people

30:30

in the democracy are committed enough

30:32

to the values of democracy. You

30:34

know, there was a... a little

30:36

plot that I just reposted on

30:38

Blue Sky the other day. There

30:40

was a survey of values or

30:42

something like that in political parties

30:45

in the Western world. Not even

30:47

the Western world, in the world,

30:49

I guess. And they plotted them

30:51

on two axes, whether a political

30:53

party was overall liberal or conservative

30:55

in values. And then also their

30:57

importance that a political party put

30:59

on international cooperation. And you know,

31:02

we can debate. where you should

31:04

be on that plot. Are you

31:06

in favor of international cooperation? Are

31:08

you not? Are you liberal or

31:10

conservative? Are you not? That's a

31:12

very... very much up for debate,

31:14

up for grabs, that's fine. What

31:17

was interesting is that, you know,

31:19

they plotted to different countries, the

31:21

United States, the UK, Norway, Italy,

31:23

China, Turkey, Russia, and they plotted

31:25

where there was a functioning democracy,

31:27

they plotted both what the left

31:29

leaning party where they landed on

31:31

this two-dimensional plot and the right

31:34

leaning party. And there's a group

31:36

of countries and parties grouped together

31:38

that roughly speaking is either more

31:40

liberal than conservative or at least

31:42

close to neutral and more interested

31:44

in international cooperation than not or

31:46

close to neutral on that also

31:49

and includes all of the parties

31:51

right and left in countries that

31:53

we know in love as Western

31:55

liberal democracies you know the European

31:57

countries Canada or whatever except for

31:59

the right-wing party in the United

32:01

States, which is off that off

32:03

of the group of Western democracy

32:06

parties right next to China, Turkey,

32:08

and Russia, which are not democracies

32:10

at all. In other words, what

32:12

it's saying is the Republican Party

32:14

in the United States is now

32:16

closer to Russia, China, and Turkey

32:18

in its political values than it

32:21

is to any other party in

32:23

Western liberal democracies. Okay? Now maybe

32:25

there is some... room to argue

32:27

about the particular methodology of

32:29

that Survey that they did

32:31

fine go ahead and do

32:33

that But the point is

32:36

One can imagine a large

32:38

group of people in a

32:40

country abandoning what we think

32:42

of as democratic values, and

32:44

I think that that's more

32:47

the problem than people disagreeing

32:49

about a little bit of

32:51

morality because of their ontological

32:53

differences Stone R. Carroll, no

32:55

relation as far as I know,

32:58

says what are your thoughts on

33:00

the physical foundations of mathematics? It

33:02

is interesting that the universe has

33:05

produced a possibility for us to

33:07

reason about these abstract mathematical objects

33:09

and deduce objective truths about them.

33:12

For example, to me, if Zermelo

33:14

Frankel axioms are true, then one

33:16

plus one equals two is undeniably

33:19

true. Are these truths fundamental, independent

33:21

of the physical reality? Are they

33:23

emergent? What's in your opinion the

33:25

most compelling view? So I am

33:27

not an expert on this stuff.

33:30

I have grappled with it. I

33:32

have tried to get a more

33:34

nuanced understanding, but I am left

33:36

unconvinced in any of the arguments

33:38

either way. But so I can

33:40

tell you my feelings, okay, but

33:42

I'm not going to be held

33:44

to saying, you have to defend

33:46

these feelings because I... feel the

33:48

force of the countervailing arguments. I'm

33:50

not a mathematical realist, okay? I

33:52

don't think that we should think

33:55

of mathematical objects as being real,

33:57

at least not in the same

33:59

sense. as we think about physical

34:01

things as being real. So I

34:03

think that physical things are real,

34:05

or at least the physical world

34:07

is real. We divide it up

34:09

into sub things, and that's our

34:12

move, not the universe's move. And

34:14

it turns out, maybe it didn't

34:16

have to turn out this way,

34:18

but it turns out that there

34:20

are patterns inherent in the sort

34:22

of instantiation of physical reality that

34:24

are describable by what we call

34:26

mathematics. Okay, one plus one equals

34:28

two is one way of saying

34:30

that every time I have one

34:32

coffee cup and another coffee cup,

34:34

now I have two coffee cups

34:36

and et cetera. There's sort of

34:38

a physical understanding of what that

34:40

means. And when you get into

34:43

the more wild areas of mathematics

34:45

with transfinite numbers and things like

34:47

that, maybe there isn't any physical

34:49

instantiation of that, and maybe it

34:51

sort of doesn't matter. So I

34:53

think where it really becomes, we

34:55

had this conversation on the podcast

34:57

not too long ago with Joel

34:59

David Hamkins, so you're welcome to

35:01

check that out. In a previous

35:03

discussion with Justin Clark Doan that

35:05

touched on these things, there

35:08

are, it is a well

35:10

known fact in post 20th century

35:12

mathematics, or I guess post

35:15

19th century mathematics that you can

35:17

easily write down axiom systems

35:19

that are very similar to each

35:21

other, but differ in one

35:23

axiom, and whether or not that

35:25

axiom is there, or the

35:27

opposite of that axiom is there,

35:29

or that axiom is neither

35:31

there nor not there, all of

35:33

those are consistent systems, right?

35:35

Like the continuum hypothesis, the existence

35:37

of infinite numbers that are

35:39

larger than the number of countable

35:41

numbers, the integers, but smaller

35:43

than the number of real numbers.

35:45

Is that true or false?

35:47

Well, you can choose. You can

35:49

pick an axiom to include

35:52

or not to include. And to

35:54

me, that means like clearly

35:56

these things are not objectively real.

35:58

There are ways that we

36:00

are constructing systems ourselves that turn

36:02

out to be super duper... useful

36:04

for discussing physical reality. For what it's worth I do have

36:06

a paper where I express these feelings. It is called reality

36:08

realism. You're welcome to check it out. Yusuf

36:10

says, do you think taking more

36:12

abstract math courses is beneficial for

36:14

a physics student wanting to pursue

36:16

higher education in physics? For example,

36:18

classes like real analysis, topology, and

36:20

abstract algebra. I'm curious if you

36:23

think being trained in upper level

36:25

math courses is beneficial for people

36:27

doing not just theoretical research but

36:29

experimental. Well, I think it's a

36:31

cost-benefit analysis question. All else being

36:33

equal, yes, it is absolutely useful

36:35

to take those courses. It's also

36:37

useful to learn foreign languages and

36:39

to learn programming languages and to

36:41

appreciate the history and philosophy both

36:43

of science and other things. Maybe

36:45

it's beneficial to take classes in

36:47

literature or poetry because it makes

36:49

you a more eloquent explainer of

36:51

your science. So there's lots of

36:54

things that could be beneficial. Whether

36:56

or not taking a class in real

36:58

analysis, for example, for those of you

37:00

who don't know, real analysis is like

37:02

the fancy pants way of saying calculus.

37:05

But it gets very, very fancy, so

37:07

you almost don't recognize it anymore. Like

37:09

once you take seriously the number of

37:11

numbers on the real line, things go

37:14

pretty wild. And a lot of your

37:16

common sensical ways of thinking about math

37:18

break down, so you have to like

37:20

stick with what the axioms are actually

37:23

telling you, and then that's... That's a

37:25

step along the way to becoming

37:27

a more rigorous mathematician. Physicists generally

37:29

don't care about any of that

37:32

stuff. Generally, sometimes they might. But

37:34

generally, you just do an integral.

37:36

You're not worried too much about

37:39

all the higher level details of

37:41

proving that it converges or whatever.

37:43

Some areas in quantum field theory,

37:46

where you really try to prove

37:48

careful theorems, then you need some

37:50

functional analysis, real analysis, real analysis.

37:53

topological considerations and so

37:55

forth. But that's, you know, a

37:57

tiny little subset of physics, even

37:59

theoretical. physics, like most theoretical physicists,

38:01

if you want to calculate the

38:04

scattering amplitude of two electrons into

38:06

two photons or whatever, okay, you

38:08

don't need any of that fancy

38:10

math to do that. I think

38:12

it's good training because it stretches

38:14

your brain. It really is, mathematics

38:16

is the most rigorous I count

38:18

mathematics and sort of logic together

38:20

in a set of things that

38:22

say like here's a set of

38:24

axioms, what can you prove? And

38:26

that way of thinking is really

38:29

good exercise. It's a good calisthenics

38:31

for your brain, okay? But the

38:33

actual substance of what you learn,

38:35

you know, about some theorem, about,

38:37

you know, contractability of a certain

38:39

space or whatever, will be... unlikely

38:41

to be directly useful to you

38:43

in your physics research. And again,

38:45

it could be if you're one

38:47

of those supermathematical physicists, but you're

38:49

asking in general, and I think

38:51

that most physicists learn the math

38:53

they need as they go, rather

38:56

than learning math classes. And the

38:58

other thing is... Mathematicians are doing

39:00

math for different reasons than physicists

39:02

are. Physicists want to get the

39:04

answer and they want to put

39:06

it to work. You know, when

39:08

I was in grad school and

39:10

it dawned on me from taking

39:12

quantum field theory classes, etc. that

39:14

the idea of group theory and

39:16

Lee groups and Lee algebras and

39:18

representations was really important. I sat

39:21

in on a class in the

39:23

math department on the groups and

39:25

the algebras and it was entirely

39:27

a waste of time. It was,

39:29

you know, like theorem lemma proof,

39:31

you know, showing that something could

39:33

be diagonalizable or representation was faithful

39:35

or whatever it was, and as

39:37

a physicist, you would just look

39:39

it up. you just say, oh,

39:41

is this true? Okay, it is.

39:43

All right, I'm going to move

39:45

on, right? And very elaborate methods

39:48

of proving these things. So what

39:50

you want out of these mathematical

39:52

concepts is different as a mathematician,

39:54

and that's fine. But don't think,

39:56

I guess, is the short answer

39:58

that you need to take fancy

40:00

math classes to be a very

40:02

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40:54

restrictions may apply. Astro Nobel says,

40:56

I hear a lot of people,

40:58

scientists and laymen alike, talk with

41:00

confidence about the existence of extraterrestrial

41:02

life and the chances to find

41:05

it in the near future. I

41:07

have the impression that proper Bayesian

41:09

reasoning is not applied most of

41:11

the time, and that expectations are

41:13

often mixed with hope and wishful

41:15

thinking. No matter what we find

41:17

or fail to find, credences are

41:19

never lowered. Why are people so

41:21

reluctant to admit that new results

41:23

indicate that life may not exist

41:25

outside the earth at all? How

41:27

should a good Bayesian reason about

41:30

this? Well, I think that the

41:32

thing about Bayesianism, of which I'm

41:34

a big fan, is the following.

41:36

You admit that you start your

41:38

investigation with prior credences, right? You

41:40

have priors for something being true,

41:42

and then you update them when

41:44

new evidence comes in. And... The

41:46

way that you update them is

41:48

on the basis of what are

41:50

called likelihood functions. Given all the

41:52

different possible theories, under which theory

41:54

would, no, under each theory I

41:57

should say, would the new information

41:59

be probable or improbable? and conditions

42:01

under which the information you're

42:03

getting is probable would increase

42:05

in their credences and that's

42:08

given you your posterior not

42:10

your prior people keep calling it

42:12

a prior even after it's been

42:14

updated but that is you know

42:17

technically not correct so The big

42:19

worry about Bayesian reasoning is what

42:21

if we start with very very

42:23

different priors, which is allowed by

42:26

the rules of Bayesianism, and then

42:28

you require enormous overwhelming evidence in

42:30

the form of likelihood functions to

42:32

converge on a common answer. There

42:35

are theorems that assure us that

42:37

if we get enough evidence, we

42:39

will always converge on the common answer,

42:41

but... You can easily find yourself in

42:44

a situation where, number one, priors are

42:46

very different, and number two, there's just

42:48

not enough evidence to move them very

42:50

much. I think that's the situation we're

42:53

in right now with life on other

42:55

planets. We have the fact that we

42:57

exist. Some people take our existence to

43:00

say you should have a prior that

43:02

life is actually pretty ubiquitous, that it's

43:04

easy to make. You'll keep being told

43:06

that life arose relatively quickly here on

43:09

earth, even though it might have

43:11

been hundreds of millions of years,

43:13

still relatively quickly compared to the

43:15

billions of years that we've been

43:17

around. and therefore the argument goes

43:20

your prior should be large. Other

43:22

people will say, well, I have

43:24

a prior that it's very small,

43:26

I have evidence that we haven't

43:28

met any other civilizations yet, and

43:31

that decreases my prior to an

43:33

even lower number, and that's both

43:35

perfectly fine. There's a lot of

43:37

evidence, and none of it is...

43:39

definitive, I guess. I mean, there's a

43:42

lot of evidence in some sense. What

43:44

I mean is there's a lot of

43:46

different kinds of evidence. There's evidence from

43:48

biochemistry and thinking about the origin of

43:50

life. There's evidence that we've looked for

43:52

a lot of planets, and we found

43:54

a lot of planets, right? So

43:56

whatever your credence is that life on

43:59

other planets exist, based purely on the

44:01

number of planets we found, it's very

44:03

reasonable that it should be higher now

44:05

than it was before. Based on the

44:07

fact that none of them have stood

44:10

up and said, hi, your credence should

44:12

be lower than it was before, and

44:14

there's a battle going on. So I

44:16

just don't think that the evidence is

44:18

strong enough in any way to... really

44:21

be upset if people still have credences

44:23

that are very different than yours. That's

44:25

why I'm very, very open-minded about this

44:27

particular question. The credences are just not

44:30

pinned very close to zero or one.

44:32

Chris Mason says, how do you feel

44:34

about the 76ers season so far? Disappointed

44:36

or as expected. So I'm not sure

44:38

if Chris is teasing me a little

44:41

bit here, but for those of you

44:43

basketball fans out there, my team, the

44:45

Philadelphia 76ers, went into the season with

44:47

enormously high expectations, having two superstars on

44:49

the team, Joelle Embed and Tyres Maxie,

44:52

and getting a third superstar, Paul George,

44:54

as a free agent, and doing a

44:56

pretty good job of building out the

44:58

rest of the roster on very cheap.

45:00

contracts, etc. So expectations were very high

45:03

and it has been a complete unmitigated

45:05

disaster. And it's a weird, like it's

45:07

so disastrous this season that it's almost

45:09

inexplicable. You know, it's not really that

45:11

the team was ill-constructed. You know, the

45:14

obvious thing is there have been injuries,

45:16

especially to Joelle and Bede. If you,

45:18

I follow this too closely, so for

45:20

those of you who care, Joe Allenbeat

45:23

had a knee injury and... There's a

45:25

question of how do you get better

45:27

after the knee injury. He's had a

45:29

lot of injuries over the year, but

45:31

I think people hope and beat has

45:34

been shut down for the year. They're

45:36

gonna try other different strategies for getting

45:38

him better. I still, you know, I

45:40

recognize that I am not the general

45:42

manager of the team. I'm not the

45:45

coach of the team. I'm not a

45:47

player on the team. My job is

45:49

to enjoy the team's success. So I'm

45:51

going to continue to be optimistic that

45:53

next year, everyone's gonna be optimistic. to

45:56

happen. Peter Bamber says, you recently said

45:58

that for the first time you had

46:00

a thought about leaving the USA as

46:02

a consequence of political changes, though you

46:05

have no plans to do so. What

46:07

is the view amongst your friends and

46:09

colleagues on this topic? Well, look, I

46:11

think most people don't really want to

46:13

leave their... houses and their jobs, right?

46:16

Especially in academia, that's super hard to

46:18

do. If you're like a genius superstar,

46:20

then you can call up another university

46:22

and get a job offer, but most

46:24

people, you know, getting a job is

46:27

very difficult and very precious and you

46:29

hang on to it when you have

46:31

it, especially at a moment when funding

46:33

and things like that are very precarious.

46:35

It's super precarious here in the United

46:38

States, obviously. The president of John's... just

46:40

put out an email, which was overall,

46:42

I think, a pretty good email. Ron

46:44

Daniels is the president, and he was

46:46

sort of, he made the point, which

46:49

I hoped he would make, that we

46:51

still stand up for diversity and pluralism

46:53

here at Johns Hopkins, but he also

46:55

said, look, we're getting cut. by an

46:58

enormous amount and it might be a

47:00

devastating set of cuts coming down the

47:02

road, even though they don't know exactly

47:04

what they are yet. As I said,

47:06

because we have no idea what the

47:09

actual funding cuts are going to be,

47:11

so it's very hard to do planning

47:13

for the future. So that kind of

47:15

thing makes people worried, you know. Certainly

47:17

if I were a young person, if

47:20

I were looking at postdocs, and I

47:22

had a chance to go to a

47:24

country that was a little more reliable

47:26

in their funding of science, then I

47:28

would take that very, very seriously. But,

47:31

you know, as an old settled person,

47:33

you know, I'd rather, you know, just

47:35

stick around, and I think that that's...

47:37

basically what people think. I think that

47:40

a lot of young people, you know,

47:42

we're right now, it is early March,

47:44

which means that we're recruiting new grad

47:46

students and things like that. Some major

47:48

universities have already said we're not going

47:51

to accept any new graduate students this

47:53

year. Others have accepted grad students and

47:55

then rescinded the offer to them because

47:57

they just don't have. money. And this

47:59

is, it makes a very difficult time

48:02

of a young person's life even more

48:04

difficult in ways that, you know, my

48:06

heart breaks for them and I really

48:08

feel bad for them. Here at Hopkins,

48:10

we're thinking that we can just stick

48:13

with the number of grad students that

48:15

we've already accepted, so we're recruiting them,

48:17

and in fact, it looks like we're

48:19

going to do much better this year

48:21

at getting people to come to Hopkins

48:24

because we're better than average in terms

48:26

of... assuring the prospective grad students that

48:28

they will get a position when they

48:30

arrive. But if I had an option

48:33

to go somewhere else that, you know,

48:35

things were more reliable and I would

48:37

take that very, very seriously. I don't

48:39

yet know of any senior colleagues who

48:42

are saying, I'm picking up and leaving.

48:44

This is something that takes months or

48:46

years to really sink in to people.

48:49

So I don't think it's like that

48:51

anyone will snap their fingers and suddenly

48:53

will lose 10 percent of our scientists,

48:55

but... there's an accumulated effect that is

48:58

sort of difficult to discern from moment

49:00

to moment and it's many little

49:02

changes in outlook that add up to

49:04

a big effect. So I don't I

49:07

don't see in any exodus from the

49:09

United States right now but I think

49:11

the long-term effects are going to be

49:13

very very noticeable. Paulina Vino

49:15

says, do you think that agents made

49:18

up of conscious agents, for example

49:20

a company or a society, can themselves

49:22

have a conscious experience? What are

49:24

the caveats for this and how would

49:26

we know if say a corporation

49:28

or a country were conscious if we

49:31

can even know this? So I

49:33

think... I don't think it's useful to

49:35

think of countries as being conscious in

49:37

the same way that we human beings

49:40

are being conscious for a number of

49:42

reasons. I should mention that not everyone

49:44

agrees. Eric Schutzkable, who is a previous

49:47

mindscape guest, has written a paper saying

49:49

that if you are materialist about ontology

49:51

and you think that, you know, consciousness

49:53

is just an immersion property, both of

49:55

which are true for me, then you

49:57

should probably think that the United States

49:59

is conscious. which I don't think. But

50:01

my reason for thinking that is

50:03

not thinking that it's impossible in

50:05

principle, but I think that there

50:07

are questions of time scales and

50:09

integration that aren't quite... appreciated in

50:12

most discussions of what consciousness is.

50:14

When we think about consciousness, we

50:16

think about not just a person

50:18

contemplating themselves, we also think about

50:20

their interactions with other people, right?

50:22

And, you know, people just are

50:24

smaller and quicker than countries or

50:26

corporations. They can have a lot

50:28

of thoughts in a very short

50:30

period of time, and those thoughts

50:32

are kind of coherent. You know,

50:34

we know that in the brain

50:36

lots of incoherent things are going

50:38

on, lots of different parts of

50:40

the brain. are bouncing back and

50:42

forth and interacting with each other

50:45

much like a country or a

50:47

corporation. But in physics terms you

50:49

would say that the bouncing around

50:51

is tightly coupled, right? Like there's

50:53

part of your brain that's literally

50:55

right next to the other part

50:57

of your brain and very very

50:59

quickly exchanging information and coming to

51:01

some equilibrium or consensus or whatever

51:03

in ways that doesn't quite happen

51:05

for a country or a corporation.

51:07

So I think that you know

51:09

there are... details about what is

51:11

necessary to say that a group

51:13

is truly conscious that tend to

51:15

be absent in these dilute large-scale

51:17

things like countries or corporations. But

51:20

that's more or less a feeling.

51:22

There's nothing quantitative there. I'm open

51:24

to the possibility. I guess I

51:26

would need some operational. way of

51:28

thinking about it. What is the

51:30

difference that it makes to thinking

51:32

about the behavior of a country

51:34

or corporation to say that it

51:36

is conscious or not? I think

51:38

that when it comes to human

51:40

beings, we invent the concept of

51:42

consciousness because it is explanatory. It

51:44

helps us understand how people are

51:46

behaving. Oh, this person is conscious

51:48

of this happening and that's why

51:50

they did this other thing. Not

51:53

sure that that talk is very

51:55

useful when it comes to countries

51:57

or corporations, but, you know, maybe

51:59

in some circumstances it is. I'm

52:01

open to the possibility. Morrison Chady

52:03

or Chaddy says, when I was

52:05

in high school we were told

52:07

that the 19th century scientists were

52:09

looking for a medium which they

52:11

called ether in which light waves

52:13

would propagate. Eventually, the theory of

52:15

electromagnetism established that there was no

52:17

such medium. Yet I can't help

52:19

but think that the original view

52:21

was vindicated by quantum field theory.

52:23

Isn't the electron field of quantum

52:26

field theory the equivalent of ether?

52:28

No. It is not the equivalent

52:30

of ether. I have answered this

52:32

question or talked about it in

52:34

various times, but it's been a

52:36

while, so let's address it again.

52:38

The fields of quantum field theory

52:40

are just the quantum versions of

52:42

the fields of classical field theory.

52:44

So if you think that classical

52:46

electromagnetism, which is a classical field

52:48

theory, doesn't need ether, then you

52:50

think that quantum fields don't need

52:52

ether either. The point is that

52:54

either was supposed to be, like

52:56

you say, a medium in which

52:58

waves propagate. Whereas in contrast... Field

53:01

theory, classical or quantum, takes the

53:03

fields as the fundamental independent entities.

53:05

The waving electron field or the

53:07

waving electromagnetic field or the waving

53:09

Higgs field or whatever, none of

53:11

these are waves in something other

53:13

than themselves. Okay, so that's the

53:15

ontological difference. And there's also a

53:17

practical difference. The whole point of

53:19

the ether in 19th century physics

53:21

was to allow for there to

53:23

be a rest frame. with respect

53:25

to which you can measure your

53:27

motion, as opposed to the naive

53:29

reading of Maxwell's equations, which say

53:31

there is no universal rest frame.

53:34

So 19th century physicists went to

53:36

great lengths to sort of bend

53:38

over backwards and figure out how

53:40

you could reconcile the existence of

53:42

a rest frame determined by the

53:44

ether with the fact that you

53:46

couldn't observe it in any way

53:48

in Maxwell's equations. And that's how

53:50

they invented things like Lorentz transformations,

53:52

even before relativity came on the

53:54

scene. But in quantum field theory,

53:56

there's no rest frame. There's no

53:58

rest frame. Everything is. perfectly relativistically

54:00

invariant. So the whole point of

54:02

the ether is completely missing in

54:04

quantum field theory. So I don't

54:07

think that's an especially useful way

54:09

of thinking about things. Mark Foske says,

54:11

you have said that it's wrong to

54:13

think of the inside of a nucleon

54:15

as a dynamic place with lots of

54:17

quarks popping into and out of existence.

54:20

To the best of my understanding, it's

54:22

Matt Strassler who popularized that very view.

54:24

Can you think of something about how

54:26

a physicist could arrive at such a

54:28

So it's certainly not Matt who popularized

54:31

that view. That view has been around

54:33

forever. This is a very very common

54:35

way that physicists talk, as if the

54:37

vacuum state or a particular state of

54:39

a proton or neutron is actually

54:42

wildly fluctuating back and forth. And

54:44

I think it's just because people

54:46

don't have what I would call

54:49

the right. philosophical view of how

54:51

to think about quantum states. There's

54:53

a relationship between our classical way

54:56

of thinking and then what happens

54:58

when we quantize it. And people

55:00

kind of are reluctant to let

55:03

go of that classical way of

55:05

thinking. I think that if you

55:08

asked any physicist, is the quantum

55:10

state of a proton in its

55:12

lowest energy state? Is it static?

55:14

Or is it dynamical? Right? So

55:16

as a literal question, you know,

55:18

there's a quantum state, sie, a

55:20

vector in Hilbert space, that represents

55:22

a single proton, alone in the

55:24

universe, in its lowest energy state,

55:26

and just ask them, is that

55:28

static or not? If they thought

55:30

about it carefully, they would tell

55:33

you is static, right? So the

55:35

question is, is that all that is

55:37

going on? If you were somehow... to observe

55:39

what is happening inside the proton over and

55:41

over again. So you make a measurement of

55:43

the proton that excites it because you're interacting

55:45

with it so it's no longer in its

55:47

ground state, but okay, now you let it

55:50

settle back down and you measure it again,

55:52

you let it settle back down and you

55:54

measure it again, or you just measure a

55:56

million protons separately, each in their ground states.

55:58

You would see different answers. Every time you

56:01

measure it, because that's the nature

56:03

of quantum mechanics, and there is

56:05

a really strong impulse when you

56:07

measure something over and over again

56:09

and see it moving around from

56:11

measurement to measurement, to think that

56:13

it's moving around when you're not

56:15

measuring it. But if you take

56:17

the point of view that the

56:19

quantum state is what really exists,

56:21

that's just not true. So I

56:23

think it's a very common view.

56:25

I think that physicists have avoided

56:27

talking to philosophers for a long

56:29

time and haven't thought about this

56:31

very carefully, but I'm going to

56:33

do my part to change their

56:35

minds. Tariq says, would you be

56:37

able to talk about information conservation

56:39

from a few perspectives to try

56:41

to help clarify what information actually

56:43

means in this context, particularly at

56:45

the quantum level, and in the

56:47

context of many worlds and why

56:49

there is such a strong perspective

56:51

that it must be conserved. A

56:54

common example that's given is if

56:56

a book is burned and you

56:58

gathered all the energy, smoke ashes,

57:00

etc. You could in principle reconstruct

57:02

the book in all respects. Binding

57:04

glue all the way down to

57:06

every atom and its state. If

57:08

they were radioactive elements in the

57:10

ink and they were decaying randomly,

57:12

as the book was burned, how

57:14

could all this be unambiguously reversible

57:16

in principle, and I don't expect

57:18

such a machine to be built,

57:20

such that no information is lost?

57:22

Yeah, I mean when you talk

57:24

about information conservation in general in

57:26

physics Let's first be clear about

57:28

what we mean by information because

57:30

lots of different people mean different

57:32

things I'm not going to go

57:34

through all the different definitions, but

57:36

the relevant one here is the

57:38

data that you require to precisely

57:40

specify the physical state of a

57:42

system So in good old classical

57:44

mechanics you imagine you have some

57:47

number of degrees of freedom, maybe

57:49

they're particles points of a field

57:51

in space, and typically the relevant

57:53

parts of information you need to

57:55

specify the state are the position,

57:57

the configuration of those degrees of

57:59

freedom, and the momentum of those

58:01

degrees of freedom, whether it's a

58:03

particle or a field or whatever.

58:05

In quantum mechanics, the state of

58:07

the entire system is generally specified

58:09

by the quantum state, the wave

58:11

function, whatever you want to call

58:13

it, the vector in Hilbert space.

58:15

There's details there about, you know,

58:17

maybe you could think of a

58:19

density operator which indicates a distribution

58:21

over possible quantum states as more

58:23

general, but that's not the point

58:25

right here. We can think of

58:27

everything as just a quantum state.

58:29

So if you give the wave

58:31

function, you've given the information, and

58:33

the statement of information conservation is

58:35

just that the amount of information

58:37

you need to specify the state

58:40

at one moment in time is

58:42

preserved over time. So if I

58:44

give you the equation, the information

58:46

to specify the state at one

58:48

moment, and I use the Schrodinger

58:50

equation to evolve it forward in

58:52

time. I can also go backward.

58:54

The information that was in the

58:56

original state is preserved. It's modified

58:58

by the fact that it's evolving

59:00

under the Schurner equation, but it's

59:02

still there. If you know the

59:04

Schurner equation, you can figure out

59:06

from the future state what the

59:08

past state was. Now, quantum mechanics.

59:10

raises a complication here because there's

59:12

such a thing called measurement. The

59:14

way that we usually talk about

59:16

quantum mechanics is there are two

59:18

different ways that a quantum state

59:20

can evolve. When you're not measuring

59:22

it, it evolves according to unitary

59:24

evolution, which is a fancy way

59:26

of saying it obeys the shorteninger

59:28

equation. But when you measure it,

59:30

the wave function collapses. Of course,

59:32

in many worlds, you interpret that

59:35

measurement event as actually just a

59:37

branching of the wave function. so

59:39

that the wave function as a

59:41

whole just does unitary evolution. But

59:43

inside a branch, which is where

59:45

actually observers live, they do not

59:47

see unitary evolution. They see wave

59:49

functions collapsing when measurement is done.

59:51

But of course, there's a more

59:53

sophisticated notion of what measurement means

59:55

in many worlds. It doesn't actually

59:57

require any conscious being to measure

59:59

it. It just requires... decoherence and

1:00:01

branching of the wave function. So, whether

1:00:03

or not information is conserved just

1:00:05

depends on what kind of evolution

1:00:08

you're talking about. In the overall

1:00:10

unitary evolution of the wave function

1:00:12

in many worlds, information is conserved.

1:00:14

In Copenhagen or objective collapse models,

1:00:16

it would not be. conserved. But

1:00:18

from the perspective of an observer

1:00:21

in a branch, that information is

1:00:23

completely lost because you do not

1:00:25

see the entire wave function of

1:00:27

the universe. So if you burn

1:00:29

a book or burn something else

1:00:31

in a fire and try to

1:00:34

collect all the information about it,

1:00:36

and like you say, in the

1:00:38

process there's some radioactive decay in

1:00:40

the wave function of the universe

1:00:42

branches, then there is no way.

1:00:44

in principle or in practice for

1:00:46

you to accumulate all the information

1:00:48

that was in the book ahead

1:00:50

of time. The statement is that

1:00:52

it's there in the wave function

1:00:54

of the universe, but that's very

1:00:56

different than saying you can actually

1:00:58

recover it somehow. So those kinds

1:01:00

of thoughts experiments are always a

1:01:03

little bit unrealistic and in fact

1:01:05

are super duper unrealistic if you

1:01:07

believe in branching of the wave

1:01:09

function. But it's just a statement

1:01:11

about the unitary evolution part of

1:01:14

quantum mechanics, not a statement about

1:01:16

measurement. Everyone knows that in measurement

1:01:18

information is not conserved. Nicola

1:01:20

Ivanov says, my question is about

1:01:22

possible information loss. See what I

1:01:24

did there? I put these questions

1:01:26

right next to each other because

1:01:28

they make sense together. Possible information

1:01:30

loss for a hypothetical observer when

1:01:33

our universe eventually enters the phase

1:01:35

of the dissiter vacuum. Are degrees

1:01:37

of freedom of the universal wave

1:01:39

function inaccessible hidden behind the dissiter

1:01:41

cosmological horizon for a hypothetical observer?

1:01:43

Or do they remain scrambled at

1:01:45

the cosmological horizon and somehow recoverable

1:01:47

in principle similarly to a black

1:01:49

hole horizon? Yeah, nobody knows that

1:01:51

is not something that is understood

1:01:53

for those of you who are

1:01:56

not familiar with this story You

1:01:58

know our universe is accelerating discovered

1:02:00

in 1998 and we attribute that

1:02:02

to dark energy pushing the universe

1:02:04

apart. We don't know exactly what

1:02:06

the dark energy is, but the

1:02:08

leading candidate is simply a cosmological

1:02:10

constant, a constant amount of energy

1:02:12

density. And if that's true, that

1:02:14

can stay like constant forever and

1:02:16

it will push our universe apart

1:02:19

forever and our universe will settle

1:02:21

down into a... cold, desolate, empty

1:02:23

state called dissiter space with nothing

1:02:25

in it other than the vacuum

1:02:27

energy, the cosmological constant, the dark

1:02:29

energy that is pushing the universe

1:02:31

apart. in that case we will

1:02:33

have a horizon around us, much

1:02:35

like a black hole has a

1:02:37

horizon, but in this case we

1:02:39

are looking at the horizon from

1:02:41

inside, and there's no singularity associated

1:02:43

with it. It's just a horizon

1:02:45

in the sense that if something

1:02:47

goes outside the horizon, then from

1:02:49

our point of view, it can

1:02:51

never come back. It is separated

1:02:53

by faster than speed of light

1:02:55

barrier. in the context of information

1:02:57

conservation, would you, would it be

1:02:59

right to think of things that

1:03:01

are inside our desiter observable universe

1:03:03

as going outside and being lost

1:03:05

forever? Or can they somehow eventually

1:03:08

come back? I think that the

1:03:10

simple understanding is that they're lost

1:03:12

forever. And the real difference with

1:03:14

the black hole case is that

1:03:16

a black, so there's a similarity

1:03:18

first, I should say. Again, for

1:03:20

those of you who aren't familiar,

1:03:22

both a black hole horizon and

1:03:24

a decider horizon have a temperature

1:03:26

and they have an entropy. This

1:03:28

is all very, very similar calculations.

1:03:30

When Hawking and Beckenstein first figured

1:03:32

out the stuff about black holes,

1:03:34

Hawking and Gary Gibbons soon thereafter

1:03:36

showed that the same kind of

1:03:38

thing is true for the horizon

1:03:40

and decider space. So there's a

1:03:42

temperature, there's radiation. The radiation for

1:03:44

our real world would be very,

1:03:46

very, very cold. You know, if

1:03:48

it's about... three degrees Kelvin outside

1:03:50

in the cosmic microwave background right

1:03:52

now. The eventual dissiter temperature would

1:03:54

be something like 10. to the

1:03:57

minus 30 Kelvin very roughly speaking.

1:03:59

So the point is it's much

1:04:01

much much much much lower. But

1:04:03

in principle it's there. So you

1:04:05

might ask can we get that

1:04:07

information back? The difference is black

1:04:09

holes evaporate. Decider space doesn't. as

1:04:11

far as we know. So black

1:04:13

holes don't last forever. Before we

1:04:15

knew about black hole evaporation, Allah

1:04:17

Hawking, people didn't worry that much

1:04:19

about information loss because you say,

1:04:21

well, I've thrown some information into

1:04:23

the black hole, I can't get

1:04:25

it back, but it's still in

1:04:27

there. Right? So I'm not that

1:04:29

worried about it. Whereas once you

1:04:31

know the black hole can evaporate,

1:04:33

now you're like, oh, well, it's,

1:04:35

there's no more black hole after

1:04:37

it's evaporated. There's nowhere for that

1:04:39

information to be. It must have

1:04:41

returned to us in the radiation.

1:04:43

Maybe, maybe not. You know, we

1:04:46

think that that's the nice way

1:04:48

to think about unitary evolution, as

1:04:50

just explained. But of course, we

1:04:52

don't know the ultimate laws of

1:04:54

physics yet. Decider space, however, is

1:04:56

forever. It's the attractor solution. It's

1:04:58

the equilibrium solution. It's the highest

1:05:00

entropy state the universe can be

1:05:02

in. So as far as we

1:05:04

know, that horizon just stays there.

1:05:06

And there's no sense in which

1:05:08

the information that goes beyond the

1:05:10

horizon needs to come back to

1:05:12

our observable universe. That's not to

1:05:14

say it doesn't. You know, we

1:05:16

don't. there is an open question

1:05:18

about whether or not we should

1:05:20

think of dissiter space as a

1:05:22

finite number of degrees of freedom

1:05:24

inside the horizon and an infinite

1:05:26

number outside or as a finite

1:05:28

number of degrees in degrees of

1:05:30

freedom inside the horizon and everything

1:05:32

outside is just sort of a

1:05:35

mirage. Everything that we're thinking about

1:05:37

as being outside the horizon is

1:05:39

actually encoded on the horizon and

1:05:41

there's only a finite number of

1:05:43

degrees of freedom to the whole

1:05:45

shebang. Okay, we don't know because

1:05:47

there's lots of things we don't

1:05:49

know about quantum gravity, holography, things

1:05:51

like that. But I think that

1:05:53

the easy way to think about

1:05:55

it until there's some strong evidence

1:05:57

otherwise is that the information just

1:05:59

leaves us when it crosses the

1:06:01

dissiter horizon and we're never going

1:06:03

to get it back. It's out

1:06:05

there, but we're never going to

1:06:07

be able to see it ourselves.

1:06:09

Water says, if special relativity says

1:06:11

there is no universal now, how

1:06:13

does many worlds know how to

1:06:15

split? Or when to split, sorry.

1:06:17

Many worlds is very smart. It

1:06:19

knows lots of things. I think

1:06:21

that this is an example where

1:06:24

I'm going to invoke the thing

1:06:26

that I often say, which is

1:06:28

that the idea of branching. in

1:06:30

many worlds is made up by

1:06:32

human beings. The laws of physics

1:06:34

are simply that the universe obeys

1:06:36

the Schrodinger equation. The universe is

1:06:38

described mathematically as a wave function

1:06:40

or a vector in Hilbert space,

1:06:42

and it obeys a Schrodinger equation.

1:06:44

There's nowhere in there any mention

1:06:46

in the fundamental... description of what

1:06:48

many worlds is of branches or

1:06:50

splits or anything like that. Those

1:06:52

are higher level emergent phenomena. That's

1:06:54

why David Wallace's book, former Mindscape

1:06:56

guest David Wallace, his famous book

1:06:58

about many worlds, is called the

1:07:00

emergent multiverse. And the thing about

1:07:02

emergent things is we choose to

1:07:04

define them by throwing away information,

1:07:06

right? By coarse graining or whatever,

1:07:08

by making some choices about what

1:07:10

information matters to us and what

1:07:13

doesn't. Typically in emergence and things

1:07:15

like the emergence of a fluid

1:07:17

description from a bunch of molecules,

1:07:19

there's more or less a unique

1:07:21

way. to throw away that information

1:07:23

to do the course graining. In

1:07:25

the case of the branching of

1:07:27

the wave function that's not true.

1:07:29

We can choose to let the

1:07:31

branching happen in all sorts of

1:07:33

different ways. So some people think

1:07:35

that branching should be thought of

1:07:37

as only happening inside a light

1:07:39

cone. I'm not a big fan

1:07:41

of that because I don't think

1:07:43

that light cones are fundamental. I

1:07:45

think that quantum gravity exists and

1:07:47

you should take advantage of that.

1:07:49

So what I like to say

1:07:51

is, you can do the branching

1:07:53

whatever way makes sense to you

1:07:55

as long as compatible with observationalational

1:07:57

with observationalational outcomes. In particular, in

1:07:59

terms of special relativity, saying that

1:08:02

different people are going to choose

1:08:04

different reference frames, that's just a

1:08:06

way of saying that I can

1:08:08

do the branching differently, depending on

1:08:10

what reference frame I'm in. And

1:08:12

the point is, it makes zero

1:08:14

difference to any observational outcome, how

1:08:16

you do the branching. There's no

1:08:18

right way to do it. There's

1:08:20

no implication. If I'm here and

1:08:22

I have a spin and it's

1:08:24

entangled with some spin very far

1:08:26

away, and I'm going to measure

1:08:28

it. I might use a language

1:08:30

that said, oh, the wave function of

1:08:32

the other spin collapses now in my

1:08:35

reference frame. But nobody cares what I

1:08:37

what my now is what reference frame

1:08:39

I'm in because there's no observable effect

1:08:41

at the other spin There eventually will

1:08:43

be when they measure it But that's

1:08:46

true no matter when I do it

1:08:48

or even if I'm working in a

1:08:50

frame where they measure it before me

1:08:52

the answers are all exactly the same

1:08:54

So it's completely a matter of convention

1:08:57

how we choose to describe that branching

1:08:59

process Ken Wolf says, I

1:09:01

recall you saying that you were very

1:09:03

disappointed with the transformation of Twitter into

1:09:05

X. What I have heard is that

1:09:07

under X freedom of speech was protected

1:09:09

all but unconditionally, with protection from unsavility

1:09:11

or downright harassment being almost entirely sacrificed

1:09:13

as a result. Is that your experience

1:09:15

or was there something else at play?

1:09:17

Well I think there's lots going on.

1:09:19

I don't actually spend a lot of

1:09:21

time on X anymore, so I'm not

1:09:24

going to try out a whole bunch

1:09:26

of evidence for what it's like there,

1:09:28

but when I do go there, because

1:09:30

I do post the new podcast every

1:09:32

day, every week when it comes out,

1:09:34

it's just mess. It's just unpleasant. People

1:09:36

are mean, people are jerks to each

1:09:39

other, there's an enormous amount of spam

1:09:41

and bots, and that's just not rewarding

1:09:43

for me. There's a lot of people

1:09:46

who are still there, who are still

1:09:48

there. And I wish that they were

1:09:50

on Blue Sky where I am, but

1:09:52

that's okay. We don't need one single

1:09:55

social media site for everybody. That's fine.

1:09:57

On Blue Sky, I enjoy talking to

1:09:59

people. It reminds me of what

1:10:01

Twitter used to be. There's always

1:10:03

jerks, right? There's always people, but

1:10:06

it's easy to ban people and

1:10:08

easy to block them and move

1:10:10

on. Whereas on Twitter, that's almost

1:10:12

all I do is block people

1:10:14

and very rarely get constructive engagement.

1:10:17

So yeah. So I just moved

1:10:19

over to Blue Sky, and Blue

1:10:21

Sky for various reasons is more...

1:10:23

shielded from potential future capture by

1:10:25

bad actors. We'll see if that's

1:10:28

true or not, but for the

1:10:30

moment that's true right now. Connor

1:10:32

Schaffrin says, I hope this question

1:10:34

isn't too much of a bummer,

1:10:36

but I'm just curious, how bad

1:10:39

do you think things will get

1:10:41

in the next four years? Yeah,

1:10:43

I don't know. I've mentioned before

1:10:45

that my track record for making

1:10:48

political predictions used to be very

1:10:50

good, and then starting in 2016,

1:10:52

it became very bad. So recognizing

1:10:54

my own limitations, I'm not about

1:10:56

making predictions, because my predictions have

1:10:59

been pretty reliably wrong for the

1:11:01

last decade. It could get very

1:11:03

bad. I mean, I guess... It

1:11:05

is useful to understand, even if

1:11:07

you don't want to make a

1:11:10

prediction, the range of possible outcomes,

1:11:12

right? And that includes the best

1:11:14

possible and the worst possible outcomes.

1:11:16

In my own personal view, I

1:11:18

do not think that Donald Trump

1:11:21

is a good president. I think

1:11:23

that the things he is doing

1:11:25

to the United States and to

1:11:27

the world order and to the

1:11:29

progress of science and academia are

1:11:32

terrible and bad. If you think

1:11:34

differently, you will obviously have different

1:11:36

answers to this question, just so

1:11:38

you know that that's where I'm

1:11:41

coming from. So to me, the

1:11:43

best possible outcome is the courts

1:11:45

and the rest of the governmental

1:11:47

system. constrain the Trump administration from

1:11:49

giving into their worst impulses. They

1:11:52

try to preserve most scientific funding,

1:11:54

most freedom of the press and

1:11:56

universities and so forth, all of

1:11:58

which are under threat right now,

1:12:00

to try to mostly, you know,

1:12:03

somehow or another, we don't. do

1:12:05

too much damage to our international

1:12:07

standing and alliances. That would be

1:12:09

the best possible outcome and then

1:12:11

in four years people are tired

1:12:14

of this and they throw the

1:12:16

bums out. That seems like very

1:12:18

very rosy right now. I don't

1:12:20

think it's not going to be

1:12:22

business as usual. It's not it's

1:12:25

already not business as usual. Literally

1:12:27

as I'm recording this they just

1:12:29

announced that they've cut off stipends

1:12:31

to full bright scholars. Full bright

1:12:33

scholars are you know it's a...

1:12:36

for college students who want to

1:12:38

spend a year abroad, sometimes they're

1:12:40

in the United States, but they're

1:12:42

doing something, you know, for a

1:12:45

year, something interesting because they want

1:12:47

a competition and they show that

1:12:49

they're some of the best, most

1:12:51

promising scholars we have and this

1:12:53

is their... tiny salary that they

1:12:56

pay rent on and buy groceries

1:12:58

with and suddenly the government says,

1:13:00

oh, actually we changed our mind,

1:13:02

we're not going to give that

1:13:04

to you. And they might be

1:13:07

stuck in another country or something

1:13:09

like that. This is just unconscionably

1:13:11

bad behavior on the part of

1:13:13

our government. And it's a very

1:13:15

tiny thing compared to other things

1:13:18

that they're doing, but it shows

1:13:20

how little they care about real

1:13:22

human beings and some of the

1:13:24

best human beings that we have.

1:13:26

So the worst side, the worst

1:13:29

case scenario is... that the rest

1:13:31

of the governmental apparatus lets them

1:13:33

get along, go along with their

1:13:35

plans to break everything. We essentially

1:13:38

become pariahs on the international scene

1:13:40

because Canada and Australia and Europe

1:13:42

and Japan and so forth no

1:13:44

longer think of us as reliable

1:13:46

partners and they form their own

1:13:49

organizations that exclude us. The economy

1:13:51

completely collapses because we are... firing

1:13:53

in an enormous number of government

1:13:55

workers which leads to huge amounts

1:13:57

of unemployment and then we cut

1:14:00

taxes for very rich people while

1:14:02

not doing anything for non-rich people

1:14:04

and we cut Social Security and

1:14:06

Medicaid so that very poor people

1:14:08

are worse off and we put

1:14:11

on tariffs that lead to trade

1:14:13

wars so there's enormous inflation that

1:14:15

we're going to have to be

1:14:17

faced with. All of these... are

1:14:19

super plausible. They're happening, right? Like

1:14:22

we're not making this up right

1:14:24

now. And potentially worse than that

1:14:26

is that the political system will

1:14:28

be undermined. You know, there's this

1:14:31

long-standing pattern where people on that

1:14:33

side of things make a joke

1:14:35

about something terrible and then they

1:14:37

actually do it. And right now

1:14:39

they're joking about getting Trump a

1:14:42

third term in 2028. So let's

1:14:44

just to... put the fear of

1:14:46

God into you as it were.

1:14:48

Trump became president in 2017 and

1:14:50

he's become president again now in

1:14:53

2025 and he's the same person

1:14:55

that he was but the amount

1:14:57

of damage and the swiftness that

1:14:59

he's with which he's doing the

1:15:01

damage has been ramped up enormously

1:15:04

now. Back then, he was still

1:15:06

rained in by certain expectations, right?

1:15:08

By having certain ideas of like

1:15:10

having regular old people in the

1:15:12

cabinet or in government organizations. That's

1:15:15

completely gone. Now his cabinet is

1:15:17

full of Fox News hosts and

1:15:19

loyalists who don't know anything about

1:15:21

the agencies that they're leading, but

1:15:23

they're very very loyal to Donald

1:15:26

Trump. So there's an enormous ramping

1:15:28

up of the boldness and brazenness,

1:15:30

right? Okay, keep that in mind.

1:15:32

And then think about the fact

1:15:35

that in 2020, he lost an

1:15:37

election and refused to give up

1:15:39

power. He tried his best to

1:15:41

overturn the election results and eventually

1:15:43

led to January 6th, the riot

1:15:46

taking over the U.S. capital. So

1:15:48

the sensible thing to believe is

1:15:50

that 2024, sorry, five years, three

1:15:52

years from now. So 2028. you

1:15:54

can imagine will be as much

1:15:57

worse than 2020 was as 2025

1:15:59

right now is worse than 2017

1:16:01

was. so much more brazenness, so

1:16:03

much more relying on complete control

1:16:05

of all the leavers of government

1:16:08

and having loyalists in place, you

1:16:10

know, of all the things that

1:16:12

he's done, there's things that, you

1:16:14

know, are very obvious, like tariffs

1:16:16

and things like that, that people

1:16:19

get worked up about, but the

1:16:21

complete purges of independent agency leaders

1:16:23

and... people in inspector generals were

1:16:25

supposed to control corruption and things

1:16:28

like that those people are all

1:16:30

fired right so the number of

1:16:32

things he can get away with

1:16:34

now or in 2028 are enormously

1:16:36

larger than what he could get

1:16:39

away with in 2020. So that's

1:16:41

the worst case scenario. Like, usually

1:16:43

you talk to political scientists when

1:16:45

you get like crazy political ideas

1:16:47

in your head. You talk to

1:16:50

professional political scientists and they talk

1:16:52

you down. Like, oh no, it's

1:16:54

not that bad. If you right

1:16:56

now talk to professional political scientists,

1:16:58

they will tell you, 90% of

1:17:01

them will tell you, it can

1:17:03

be much worse than you think.

1:17:05

Like, whatever crazy dream you have

1:17:07

about democracy collapsing, the Constitution being

1:17:09

overthrown, no more actual elections with

1:17:12

undetermined outcomes ahead of time, all

1:17:14

that could go. That's the worst

1:17:16

case scenario. And I think we

1:17:18

need to take that seriously. People

1:17:21

are certainly talking about that. So

1:17:23

I hope it doesn't go that

1:17:25

bad. And, you know, this is

1:17:27

not even to get into... measles

1:17:29

outbreaks and other disease outbreaks and

1:17:32

universities collapsing. We already see universities

1:17:34

stopping letting new students in because

1:17:36

they can't afford it. New graduate

1:17:38

students at a lot of major

1:17:40

universities. The amount of bad that

1:17:43

it can be is really really

1:17:45

really bad so I think that

1:17:47

even though the range of possibilities

1:17:49

is still broad it's prudent to

1:17:51

plan for the worst and to

1:17:54

see what we can do to

1:17:56

prevent it. Justin Proctor says I

1:17:58

have to fly back to... East

1:18:00

to visit families. as someone who

1:18:02

does a lot of traveling for

1:18:05

work, do you feel as safe

1:18:07

flying now after the recent cuts

1:18:09

to the FAA and increase in

1:18:11

collisions and near collisions as before?

1:18:13

Well, no, certainly not as safe

1:18:16

as before, but still pretty darn

1:18:18

safe. I have no problems flying.

1:18:20

Flying until very recently was actually

1:18:22

super duper safe. You know, congratulations

1:18:25

to the FAA and to the

1:18:27

airline industry, etc. the idea of

1:18:29

taking a giant metal bird and

1:18:31

flinging it across the country seems

1:18:33

a little dicey but we don't

1:18:36

really have air crashes anymore because

1:18:38

we have built in an enormous

1:18:40

amount of safety is much safer

1:18:42

than driving a car or something

1:18:44

like that. But yes, one of

1:18:47

the very bad things that is

1:18:49

going on right now is cutting

1:18:51

people from the FAA. generally degrading

1:18:53

our ability to take care of

1:18:55

these things, shifting from well-established procedures

1:18:58

to letting Elon Musk's company be

1:19:00

in charge of things, it's not

1:19:02

as safe. And I think that

1:19:04

on the one hand, it's kind

1:19:06

of like climate change, right? Like,

1:19:09

you know the climate change is

1:19:11

going to increase the number of

1:19:13

unpredictable bad things happening. But when

1:19:15

you get a specific unpredictable bad

1:19:18

thing, you can't very easily just

1:19:20

say, oh, climate change did it,

1:19:22

right? You can say climate change

1:19:24

increase the chances of that happening,

1:19:26

but it's hard to get it

1:19:29

a very, very specific correlation there,

1:19:31

causal relationship there. Exactly the same

1:19:33

thing with the plane crashes that

1:19:35

we've seen and the close calls

1:19:37

on runways that we've seen. It's

1:19:40

been a little scary for some

1:19:42

people. Some people I know personally

1:19:44

have been in one of these

1:19:46

situations where the plane was landing

1:19:48

and had to actually stop landing

1:19:51

and zoom off because there was

1:19:53

by mistake another plane on the

1:19:55

runway just in the last couple

1:19:57

weeks. It's not, it's very very

1:19:59

difficult to directly associate these. these

1:20:02

events with the degradation of the

1:20:04

Federal Aviation Administration, but it is

1:20:06

not surprising that the rate of

1:20:08

those events has gone up. It's

1:20:10

still pretty low though. If we're

1:20:13

honest about it, it's still pretty

1:20:15

low right now. So I'm still

1:20:17

very willing to hop on a

1:20:19

plane. If it gets worse, then

1:20:22

that could conceivably change. Chris

1:20:24

says at some point a few

1:20:26

episodes back you made an often

1:20:28

comment about how the locality of

1:20:30

physical laws was an astonishing or

1:20:32

least unnecessary property and could be

1:20:34

viewed as a type of fine

1:20:37

tuning. I'm confused how locality can

1:20:39

be viewed as surprising. What would

1:20:41

a universe with non-local interactions look

1:20:43

like? If we'd evolve in such

1:20:45

a universe wouldn't we have a

1:20:47

different notion of distance such that

1:20:49

physical laws appear to respect our

1:20:51

idea of locality? What does distance

1:20:53

even mean if not the metric

1:20:56

that determines which things can interact?

1:20:58

Well, yeah, this is a very

1:21:00

good question. Sorry if I wasn't

1:21:02

clear about it before, but the

1:21:04

important part of this question is,

1:21:06

wouldn't you say, if we devolve

1:21:08

in a universe with non-local interactions,

1:21:10

wouldn't we just have a different

1:21:12

notion of locality, such that the

1:21:14

physical laws appear to respect those

1:21:17

different laws? So the implication there

1:21:19

is that given any set of

1:21:21

interactions, it must be possible to

1:21:23

organize them so that things interact

1:21:25

readily when they're near... nearby under

1:21:27

some definition of locality, but not

1:21:29

when they're far away under some

1:21:31

definition of locality. But the mathematical

1:21:33

fact is there's no reason that

1:21:36

that kind of organization must apply

1:21:38

to hypothetical laws of physics. If

1:21:40

you think about locality as we

1:21:42

have it in the real world,

1:21:44

given that the real world is

1:21:46

governed by quantum field theory to

1:21:48

a good approximation, we can sort

1:21:50

of chop up the world into

1:21:52

regions of space, you know, little...

1:21:54

tiny one cubic nanometer regions, okay,

1:21:57

like little boxes all over the

1:21:59

world. And according to the rules

1:22:01

of quantum field theory, Each little

1:22:03

box will interact directly under the

1:22:05

laws of physics with its nearest

1:22:07

neighbor boxes. Okay? It doesn't interact

1:22:09

directly with boxes far away at

1:22:11

all or even a little bit

1:22:13

away, even one centimeter away. It

1:22:16

only interacts indirectly via the boxes

1:22:18

in between. Okay? That's locality. That's

1:22:20

what locality is. And... I can easily

1:22:22

imagine different laws of physics in

1:22:24

which every box interacts directly and

1:22:26

strongly with every other box. That

1:22:29

would be entirely different than the

1:22:31

laws of physics that we have

1:22:33

right now, and there wouldn't necessarily

1:22:35

be any way to organize some

1:22:38

things such that it looked local.

1:22:40

This is even a proven result.

1:22:42

There's a paper called locality from

1:22:45

the spectrum. by Jordan-Kottler at all,

1:22:47

and they showed that a generic

1:22:49

set of laws of physics isn't

1:22:51

local at all. So it is sort

1:22:54

of a mathematical fact that in the

1:22:56

space of all possible laws, ones that

1:22:58

admit some notion of locality are a

1:23:00

tiny subset. Of course you're right that

1:23:02

the notion of locality isn't given to

1:23:05

you by God ahead of time. If

1:23:07

you do have some laws of physics

1:23:09

that allow for the existence of some

1:23:11

notion of locality, you can go and

1:23:13

find it, right? And then you can

1:23:15

do your best. But it's not at

1:23:18

all something that is necessary under

1:23:20

any possible laws of physics. Pete

1:23:22

Harlan says, I've heard you say

1:23:24

that effective field theories choose a

1:23:26

cutoff for maximum energies in order

1:23:28

not to blow up. Does anyone

1:23:31

think that there actually is a

1:23:33

theoretical limit on maximum energy? Yeah,

1:23:35

sure. Plenty of theories do that.

1:23:37

The sort of most straightforward way

1:23:39

to do that is to really

1:23:41

imagine that there is a smallest

1:23:43

distance, right? That there is some...

1:23:45

minimal length scale in nature. Because

1:23:48

you know that in whenever you

1:23:50

have a field theory, if your

1:23:52

wavelength is shorter, the energy of

1:23:54

the wave that you're thinking about

1:23:57

is higher. So short wavelengths correspond

1:23:59

to high... energies, so if there's

1:24:01

a shortest possible wavelength, there is a

1:24:03

maximum possible energy. And plenty of approaches

1:24:05

to quantum gravity try to do that.

1:24:07

Arguably loop quantum gravity tries to do

1:24:10

that. I think that that way of

1:24:12

doing quantum gravity is not right. It

1:24:14

takes locality too seriously, and it's not

1:24:16

going to be able to... to recover

1:24:18

holography black hole information conservation, things like

1:24:21

that. Now maybe those things aren't true.

1:24:23

So, okay, maybe that does actually work,

1:24:25

but I think that there's good reason

1:24:27

to think that those things are true.

1:24:29

So relying too heavily on locality, I

1:24:32

don't think is the way to go.

1:24:34

But in a very different way, string

1:24:36

theory has a kind of maximum energy

1:24:38

because there's the plank scale or the

1:24:40

string scale. There's a kind of duality,

1:24:43

and this is very vague because it

1:24:45

happens under some circumstances, but not others,

1:24:47

but just to give you an idea,

1:24:49

if you have string theory and there's

1:24:51

an extra dimension in the shape of

1:24:53

a circle, you can imagine wrapping a

1:24:56

string around the circle, right? And you

1:24:58

can imagine wrapping it once or twice

1:25:00

or three times or whatever, or you

1:25:02

can imagine taking a string and not

1:25:04

wrapping it around the circle, but letting

1:25:07

it travel. around the circle with a

1:25:09

certain momentum. It turns out that there's

1:25:11

a duality where you can trade one

1:25:13

for the other. Having a string moving

1:25:15

really fast is kind of like having

1:25:18

it wrapped around in some, there's some

1:25:20

map between those possibilities anyway. So basically,

1:25:22

this is, I'm not doing a very

1:25:24

good job of explaining this, but the

1:25:26

upshot is that if you try to

1:25:29

imagine scattering two strings at super duper

1:25:31

high energy, it turns into the equivalent

1:25:33

of a low energy. interaction in some

1:25:35

other perspective, some other point of view.

1:25:37

It's not quite a hard cutoff on

1:25:39

maximum energy because that probably wouldn't work

1:25:42

anyway, but it's sort of effectively that.

1:25:44

You know, you can't be too naive

1:25:46

about this because energy is not a

1:25:48

larynx invariant concept. The energy that a

1:25:50

particle has depends on the reference frame

1:25:53

in which you're measuring it. So you

1:25:55

have to be a little more subtle

1:25:57

about talking about a theoretical limit on

1:25:59

the... scattering the energy that is exchanged

1:26:01

from one particle to another in the

1:26:04

center of mass frame or something like

1:26:06

that. But yeah, so you can imagine

1:26:08

that. All of this is very far

1:26:10

away from how we use effective field

1:26:12

theories in the real world, because in

1:26:14

the real world, in the real world

1:26:17

in the sense of actual effective field

1:26:19

theories used to make predictions in nuclear

1:26:21

physics or something like that, the cutoffs

1:26:23

that we use are far, far below,

1:26:25

the plank scale or anything to do

1:26:28

with quantum gravity. The

1:26:30

great deceiver says, I haven't heard

1:26:32

you talk too much about the

1:26:34

large-scale structure of the universe, filaments

1:26:36

and super voids and all that

1:26:38

fun stuff. I was wondering if

1:26:40

the galactic clustering, in terms of

1:26:42

these immense filaments, comes out of

1:26:44

GR and its math or even

1:26:46

other theories models like inflation. Yeah,

1:26:48

it basically does, but of course

1:26:50

there are details that are going

1:26:52

to matter. The story is that

1:26:54

we have from inflation or from

1:26:56

some other... theory of initial conditions,

1:26:58

whatever that turns out to be,

1:27:00

the early universe is pretty smooth

1:27:02

but not exactly smooth. So there

1:27:04

are fluctuations with different amounts of

1:27:06

noticeability on different length scales, but

1:27:08

on every length scale there are

1:27:10

some kinds of fluctuations and they're

1:27:12

generally small in the early universe.

1:27:14

One part in 10 to the

1:27:16

5, so a hundred thousandth. So

1:27:18

if there's a region of space

1:27:20

that has a hundred thousand particles,

1:27:22

the region next to it might

1:27:24

have a hundred thousand and one

1:27:26

or 99, nine hundred nine parts.

1:27:28

right? That's the kind of fluctuation

1:27:30

we're talking about. And then over

1:27:32

time, as the universe expands and

1:27:34

dilutes, gravity pulls together matter from

1:27:36

the slightly over-dense regions by pulling

1:27:38

matter out of the slightly under-dense

1:27:40

regions, so the universe becomes more

1:27:43

contrasty and it becomes more lumpy

1:27:45

in some regions, emptier in other

1:27:47

regions. That's exactly what is predicted

1:27:49

by general relativity plus cosmology plus

1:27:51

initial conditions, and that's exactly what

1:27:53

we see. in the universe today.

1:27:55

Now the details happen because you

1:27:57

know you have dark matter and

1:27:59

you have ordinary matter and you

1:28:01

have magnetic fields and you have

1:28:03

light in the universe heating things

1:28:05

up and you have x-rays and

1:28:07

you have supernovae exploding and injecting

1:28:09

energy into the world around them.

1:28:11

So the whole thing is kind

1:28:13

of a mess. It's what is

1:28:15

called gastrophysics by theoretical physicists who

1:28:17

find it a little frustrating. But

1:28:19

having said all that we try

1:28:21

to do our best, we do

1:28:23

pencil and paper, we do simulations,

1:28:25

we collect as much data as

1:28:27

we can. There is right now

1:28:29

a slight mismatch. between what you

1:28:31

predict the clustering of galaxies to

1:28:33

be in the current universe from

1:28:35

what we see at early times,

1:28:37

from the microwave background, etc. You

1:28:39

make a prediction and it's not

1:28:41

quite right. This is called the

1:28:43

S... You may have heard of

1:28:45

the Hubble tension. We talked to

1:28:47

Adam Reese on the podcast some

1:28:49

time ago. If you infer the

1:28:51

current Hubble constant by looking at

1:28:53

the microwave background versus if you

1:28:55

measure the current Hubble constant directly,

1:28:57

you get slightly different answers with

1:28:59

a statistically significant difference. And the

1:29:01

same thing is true for the

1:29:03

amount of clustering. And it's called

1:29:05

S8 because that's just S sub

1:29:07

8 is the number that you

1:29:09

use to have the best constrained

1:29:11

characterization of how much clustering there

1:29:13

is in the current. universe. Maybe

1:29:15

it will go away when data

1:29:17

becomes better. Maybe it's signal that

1:29:19

something really interesting is going on.

1:29:21

That's why we do science because

1:29:23

we don't know ahead of time.

1:29:25

David Maxwell says, your chat with

1:29:27

Blaiseggari Yarkas added to my growing

1:29:29

impression that life at its most

1:29:31

basic is, if not inevitable, highly

1:29:33

likely in any environment that permits

1:29:35

enough complexity. How have your credences

1:29:37

changed over time? Is any Fermi

1:29:39

paradox bottleneck at abiogenesis, multi-cellularity, sentions,

1:29:41

or somewhere else? You know I

1:29:44

do think that Blaze's results increased

1:29:46

my credence that some kind of

1:29:48

life is easier to get started

1:29:50

or more likely to get started

1:29:52

than you might have thought. But

1:29:54

if you might have thought that

1:29:56

that number was incredibly small to

1:29:58

begin with and maybe it didn't

1:30:00

really do a lot to update

1:30:02

your credences. Again, I'm actually pretty

1:30:04

open-minded about this. I do tend

1:30:06

to think that there are not

1:30:08

hyper-advised technological civilizations here in our

1:30:10

Milky Way galaxy for the simple

1:30:12

reason that it would have been

1:30:14

too easy to notice them already

1:30:16

and we haven't. That could be

1:30:18

wrong. There could be some reason

1:30:20

why they're hiding from us. But

1:30:22

it's much easier for me to

1:30:24

imagine that they're just not there,