0:08

Hey, Daniel, is it true that every electron

0:11

is identical?

0:12

Well, they all do have the same mass

0:15

and the same charge, Like exactly,

0:18

yeah, we think so.

0:19

Isn't that weird? Why don't you expect them to be a little

0:21

bit different each one.

0:23

It's kind of exactly not weird.

0:25

It means that no electrons

0:27

are weird because they are all the same.

0:29

I don't know, man, that's a bit wooky.

0:33

Like if everyone in your neighborhood looked the same, wouldn't

0:36

that be weird?

0:37

I mean, I live in Orange County, so that's

0:40

kind of what most people in the neighborhood are going

0:42

for.

0:43

Everyone's going for that scruffy physicist.

0:45

Look more

0:47

like plastic surgery face and beige

0:49

housing.

0:50

Well.

0:50

I didn't want to say anything, but yeah, I do feel like you need a

0:52

facelift in or at least a

0:54

physics lift. Hi.

1:10

I'm jorm At, cartoonist and the author of Oliver's

1:12

Great Big Universe.

1:14

Hi, I'm Daniel. I'm a particle physicist

1:16

and a professor at UC Irvine, and I'm proud

1:18

of being one of a kind.

1:19

But what kind is that? Daniel?

1:21

That's the quiet that you. The

1:24

pride might depend On. Mm, yeah, I

1:27

define my kind man. There's nobody

1:29

else like me. M.

1:30

How do you know, though, have you met everyone who's

1:33

ever existed? What if

1:35

there was a Daniel with your exact same

1:37

DNA that you know, lived two

1:39

hundred years ago or could be living right now.

1:41

It's possible, but they wouldn't have the same experiences.

1:44

I have actually met another Daniel Whitson.

1:47

He's an artist in the UK and quite

1:49

accomplished.

1:50

Ooh are you jealous?

1:54

Am I jealous of the artist lifestyle?

1:56

Oh?

1:56

So many directions to go with that?

2:01

What was that like? I don't think I've ever met a horhe Cham

2:03

yet, but I think one exists

2:05

somewhere in Indonesia.

2:06

Maybe isn't there

2:08

another one who has the Twitter handle at hohorhey.

2:11

Cham somebody got that Twitter handle.

2:13

I don't know if it is horri ha Jam or not,

2:16

but I'm waiting for the blackmail email. Mm.

2:18

Yeah, well, at least a digital copy of you exists.

2:21

Or maybe I opened it years ago, but I forgot

2:23

the password and the email

2:26

I associated it with, so I don't

2:28

know. Maybe I am my other meat.

2:30

Yeah. Maybe we're old enough that younger versions

2:32

of us are like alien minds.

2:34

Oh wait, wouldn't that make you an alien?

2:39

I think we're all still struggling to know ourselves.

2:41

Right, well, we might all

2:43

be aliens, right that Isn't there a theory that maybe

2:46

life came to Earth from Mars.

2:48

There is a theory like that called panspermia,

2:50

that life may have originated somewhere

2:53

else in the universe and then transported microbially

2:56

hidden inside asteroids. It's

2:58

a possibility all immigrants,

3:01

kind of.

3:02

But anyways, welcome to our podcast, Daniel and Jorge

3:04

Explain the Universe, a production of iHeartRadio

3:06

in.

3:07

Which we do our best to digest this alien

3:09

universe to explain all of the bizarre

3:12

and amazing effects we see out there

3:14

in terms of little mathematical stories that

3:16

your mind and my mind and Jorge's mind

3:18

can actually understand that we

3:21

can talk about and digest and explain

3:23

to you.

3:23

That's right, because it is a pretty vast universe,

3:25

and it's also pretty weird, full of unexplained

3:28

phenomenon, unanswered questions,

3:30

and potentially other versions of

3:32

you out there.

3:33

Raising all sorts of interesting philosophical

3:35

questions like what does it mean to have an identical

3:38

copy? And when you step into a transporter on

3:40

Star Trek. Is it making a copy or

3:42

actually transporting you?

3:44

And what if, like there's another Jorge and another

3:47

Daniel and they start a podcast. Can

3:49

we sue them technically or

3:53

maybe just retiring and give

3:55

them the feat?

3:57

Yeah, maybe it's time for the next generation, right.

4:00

The new Daniel and Jorge explain

4:02

the universe? Or Daniel and Horry explained the

4:04

universe the next generation?

4:06

Exactly? Yeah, one of us is Jean Luke

4:08

and the other one is Riker.

4:11

Wait wait, wait your name comes first, as I mean, I'm number

4:13

two?

4:14

Make it so? Okay?

4:16

Can I just beque? Like,

4:19

if I had to pick a character from the

4:21

next generation, I would pick Q.

4:23

Really not Data. Data might be the smartest

4:25

one.

4:26

A smart than Q can do anything in time

4:28

and space.

4:30

Q has no rules, so it doesn't really count

4:32

exactly exactly, So you basically

4:35

you want to be God, you're.

4:36

Saying, I

4:39

mean, who doesn't, come on, Q.

4:42

Has so much responsibility. Every child

4:44

who's dying of cancer. That's Q's fault,

4:47

is it?

4:47

Is it?

4:47

Really? If you had the power to

4:49

save a child and you didn't, then yeah,

4:52

I think you're kind of responsible. Boy.

4:54

That's a lot of gud killed.

4:56

That's why I'd rather be data.

5:00

Do you want to be data or be data?

5:03

Hmm, Yeah, that's a good question. I actually just want to harness

5:06

data's computing powers to solve mysteries

5:08

of the universe. Yeah.

5:09

That's a lot of makeup to put on every data.

5:11

It's pretty heavy.

5:13

Yeah, but anyways, welcome

5:16

to our podcast. We also like to answer

5:19

questions, not just talk about the answers

5:21

that physicists have found. We also like to think about

5:23

questions about the universe.

5:24

Because everybody's got questions. I've got

5:27

questions, You've got questions. Everybody who looks

5:29

up at the night sky and wonders how it all works,

5:31

or stares down between their toes and wants to understand

5:33

the tiniest particles is yearning to understand

5:36

how the world works, and that means asking

5:38

questions. And on this podcast

5:40

we answer questions at the edge of knowledge, those

5:43

pose by physicists and those pose by

5:45

listeners. So if you have questions

5:47

about the nature of the universe or some explanation

5:50

you've heard somewhere that didn't quite make sense to

5:52

you, write to us to questions at Danielandjorge

5:55

dot com. We really do. Right back

5:57

to all of our listeners.

5:58

Yeah, we're all curious about how the universe works,

6:01

why we're in it, and how it's all put together.

6:03

Although I'm not exactly curious about the particles

6:05

in your toes or anyone's toes. Maybe

6:08

we'll leave that part out of our questions.

6:11

Wow, limits to your curiosity.

6:13

That's disappointing.

6:14

Yeah, I

6:16

think there should be limits to anyone's

6:19

curiosity. But yeah, we like to answer questions

6:21

here on the podcast and plans from listeners, and so

6:23

thanks to everyone who sent their questions in.

6:25

Often I'll just write back, but sometimes we choose

6:28

questions to answer on the podcast because

6:30

we think lots of people will want to hear the answers.

6:32

And so today on the podcast, we'll be tackling listener

6:40

questions number forty nine. What

6:42

are we gonna do when we hit fifty, Daniel, We're gonna

6:44

have a mid podcast live crisis.

6:46

We're gonna have a nice cake with fifty on it, and we're

6:48

gonna fall asleep before the end of the.

6:49

Party and then burn your house down.

6:51

What it's gonna be virtual,

6:54

of course, but.

6:56

Yeah, we're answering listener questions here today and

6:58

we have some awesome questions here from our listeners.

7:01

There's one about black hole identity,

7:04

there's one about neutrino and how many

7:06

there are in the universe. And we also

7:08

have a question about what it's like to serve

7:11

a gravitational wave and

7:13

what happens when you wipe out, Like where do you

7:15

fall if it's a gravitational wave?

7:18

But let's jump right in. Our first question comes from

7:21

Matthew, who comes from Barry, Ontario.

7:24

Hello, Daniel and Jorge. This is Matthew

7:26

from Barry, Ontario up here in Canada, and

7:29

like many of your listeners, I spend a bit of time

7:32

thinking.

7:32

About black holes.

7:34

While I understand that it is impossible

7:36

for us to see what lurks beyond the event

7:38

horizon, I was curious if there is consensus

7:40

in the scientific community about all black holes

7:43

being the same, or if they could vary inside

7:46

based on their density. For example, could

7:48

a smaller black hole be not a black

7:51

hole at all, but a dark star, while

7:53

the super massive black holes at the center

7:55

of some galaxies be a more traditional

7:57

black hole or a string theory fuzz.

8:01

Thank you very much for the wonderful show and I look forward

8:03

to hearing your response.

8:04

All right, I feel like this question

8:07

ken has an identity problem in itself.

8:10

It's so many questions but also one.

8:12

But I think Matthew's basic question is

8:15

about the identity of black holes, Like,

8:17

are all black holes the same? Are

8:19

they actually black holes? Could they be something

8:21

else? Is it a case of mistaken

8:23

identity? Or do all

8:25

black holes come with an ID tag?

8:27

Yeah, he's basically wondering what's going on inside

8:30

black holes and if they all have to be the same

8:32

on the inside, and whether the

8:34

things we've seen out there in the universe that look

8:37

like black holes could actually be a bunch of different

8:39

kinds of stuff that all mimic

8:41

black holes. So it's a really cool question guess at

8:43

the heart of what we think is going on inside

8:45

black holes.

8:46

M Like, maybe what we

8:49

call black holes are actually maybe a

8:51

varity of different things.

8:53

Yeah, it's possible. And two black

8:55

holes with the same mass, do they have to look the same

8:57

on the inside?

8:59

Wait on how much mass is in it? Or

9:02

Like, two things that look like black holes, are they actually

9:04

black holes? Or do you think he's asking

9:06

if they're the same, if there's any property

9:08

that sets them apart?

9:09

Yeah, I think he's asking both of those questions, and

9:12

I think we should start with that. Like, if you have two

9:14

black holes that have the same mass,

9:17

are they the same thing? Are they indistinguishable?

9:20

Or are they different? And this is a big

9:22

question in general, relativity goes by the name

9:24

of two black holes have hair?

9:27

Essentially, are there texture or details?

9:30

Are there tiny little properties that set two

9:32

black holes apart the way two Like

9:34

identical twins are always a little bit

9:36

different. Are two black holes with

9:38

the same mass, could they actually be a little bit

9:40

different on the inside.

9:43

Well, I feel there's two questions. One is like

9:45

are they the same? And can you tell

9:48

if they're the same? Aren't those two separate

9:50

questions?

9:50

Yeah, those are two separate questions. So

9:53

as you can see, with black holes, we have like a constantly

9:55

multiplying stream of questions.

9:58

It's like a black hole of questions. It's

10:01

a bit of a rabbit hole. It's a black rabbit

10:03

hole. So which which question

10:05

are we tackling? Can you tell if two black holes are

10:07

different or whether they're actually different

10:09

inside?

10:10

Yeah, we can talk about all of it, but let's start with what's

10:12

going on inside black holes, at

10:14

least what we think is going on.

10:16

Okay, well, you sort of mentioned the no hair problem,

10:19

and that one's more of a like can you tell

10:21

if two black holes are different problem?

10:23

I think it also touches on whether the black

10:25

holes inherently are different.

10:27

Are there features to two black holes which tell

10:29

them apart? Because in general relativity,

10:32

the idea is that all you can know

10:34

about a black hole are three different

10:37

quantities how much mass it has,

10:39

whether it's spinning, and whether it has

10:42

electrical charge. And to say

10:44

that that's all you can know about a black hole means

10:46

that that's what defines a black hole.

10:49

So in general relativity, two black holes

10:51

with the same mass, spin, and charge

10:53

really are identical according

10:56

to that theory.

10:57

From the outside right, I mean, it's

10:59

basically saying that's all you can tell about

11:01

what's inside a black hole.

11:02

It means those are the only properties of

11:04

the objects, So even on the inside, they would

11:07

be identical again according to

11:09

general relativity. Important caveat we

11:11

can get to later.

11:12

But I guess, how can they be exactly

11:14

identical or how can we know or how can the theory

11:16

know that it's identical because inside the

11:18

black hole maybe things are arranged

11:21

differently.

11:21

We can't know currently because we can't see inside

11:23

black holes, but that doesn't stop the

11:25

theory from predicting what's there and describing

11:28

what we think is happening. And

11:30

according to general relativity, again big

11:33

caveat there we can get to in a minute. All

11:35

these black holes, if they have the same mass,

11:38

spin, in charge, really are identical.

11:40

They have the same exact internal

11:42

structure because they're defined just

11:44

by those three numbers, So there's no

11:46

whiggle room. There's no opportunity

11:48

for a black hole made of bananas to be different

11:50

from a black hole made of bowling balls

11:52

or squirrels if they have the same mass,

11:55

spin, and charge. That's again

11:57

according to general relativity, which is predict

12:00

what's inside black holes, though it's not something we've

12:02

seen.

12:03

I guess what I mean is like a black hole is like a sphere

12:05

right like to us, it has volume,

12:08

and so what does general relativity predict

12:10

is inside of that sphere just a

12:13

singularity? Like everything just collapses

12:15

instantly or what.

12:17

Well, a black hole that's had time to settle,

12:19

everything will fall towards the singularity.

12:22

So if things are still dynamically falling

12:24

into a black hole, its state is changing.

12:27

But after a long time. When it settles, then

12:29

it's just defined by these three numbers.

12:32

And yeah, two black holes with the same mass

12:34

will each have a singularity inside them

12:37

with the same.

12:37

Mass and nothing between the singularity

12:40

and the event horizon. What does general

12:42

relativity say is between the singularity which

12:45

is at the center, and the event horizon, which

12:47

is the outer shell of the black hole.

12:49

So it depends a little bit on the mass, spin, in

12:52

charge. These kinds of black holes

12:54

have different internal structures, like

12:56

the simplest kind one with just mass

12:58

and no spin, no charge, or this is the kind most

13:00

people talk about and think about, is

13:03

just a sphere and in the inside you have the

13:05

singularity and there's nothing else. If

13:07

it's charged or if it's spinning, then

13:10

the structure in the inside is a little bit different, Like

13:12

you don't actually have a singularity if it's

13:14

spinning, you have a ringularity

13:16

because you need an object that can spin and singularities

13:19

can't. And you can have different kinds

13:21

of horizons inside the black

13:23

hole or even near the black hole on

13:26

the outside if it's spinning and if it has

13:28

charge.

13:29

Well, that's an interesting concept you just mentioned,

13:31

which is like the settling of a black

13:33

hole. Now does that happen

13:35

like instantly over billions of years

13:38

trillions? Does it ever happen? Doesn't times

13:40

stop? Inside of a black hole?

13:42

Nothing happens instantly, right. Relativity

13:44

describes how there's a maximum

13:46

speed limit to the universe, and so

13:48

you definitely can't have things instantly

13:50

collapsing into a singularity. It always

13:53

takes time. How much time it takes depends

13:55

on who you are and where you are. Like,

13:58

if you're outside the black hole and you're watching things fall

14:00

in, you'll actually not see them fall

14:02

in because time slows down so much at

14:04

the event horizon. You'll see them frozen

14:06

at the event horizon. If you are

14:09

riding that banana into the black hole,

14:11

then you will see yourself past the event horizon

14:13

and you'll fall in, and you'll reach the singularity

14:16

in a finite amount of time. So

14:18

how long it takes depends on the observer. In

14:20

general relativity, these things are very screwy.

14:23

But I guess maybe then the scenario I

14:26

wonder that Matthew's thinking about me, Like, if

14:28

I have two black holes, they have the same mass and energy

14:31

and spin in charge and all that they're identical,

14:33

But then black hole A eats a banana,

14:36

and black hole b eats a bowling ball. Like

14:40

to us, it takes some

14:42

time for the banana to and bolling bull

14:44

to make it to the center of the black hole. So

14:46

are those two black holes different in

14:48

the meantime.

14:49

In the meantime they are. Yeah, But

14:52

if the bowling ball and the banana have the same

14:54

mass, and like that's a tiny bowling ball or

14:56

a huge banana, then eventually

14:58

they do reach steady state, which is just

15:00

described by the mass, spin and

15:02

charge.

15:04

But could we tell that one

15:06

aid the banana and the other one ate the bowling ball.

15:08

We couldn't, right, Not after they've settled into the

15:10

singularity exactly. According to general relativity,

15:12

that information is lost. Before

15:15

that information is still within the event horizon.

15:17

We can't see it, but it does still

15:20

exist within the black hole after

15:22

it's settled into the singularity. According to general

15:24

relativity, that information is gone

15:27

because the state is perfectly described by

15:29

the mass, spin in charge.

15:31

Mmm.

15:32

So then it's sort of possible for two black holes

15:34

to be different, perhaps, but for us

15:36

to not be able to tell them apart.

15:38

Yeah, that is possible, and that's a transient

15:40

state.

15:42

Right, Well, black holes are eating all the time, right,

15:44

So black.

15:44

Holes in the real world yet are always eating

15:47

are They're always surrounded by something. There's

15:49

never a true vacuum. There's always a solar wind

15:51

or particles everywhere. So yeah, absolutely,

15:53

black holes are always eating in real

15:56

life. In the sort of thought experiments

15:58

we construct, you could imagine a black hole

16:00

surrounded by actually nothing and then you just drop

16:02

a banana into it. But yeah, and the real

16:04

universe, black holes are never surrounded by

16:06

nothing.

16:08

But I think, as you were saying, this all depends on

16:10

general relativity.

16:12

Yeah, exactly. This is a picture

16:14

from classical physics that says

16:16

that singularities can exist within black

16:18

holes, and that it matter could be compressed into

16:20

a tiny dot. That's totally incompatible

16:23

with what we know about the nature of reality that

16:25

is quantum mechanical. Though, when things get really

16:27

really small, like the size of singularities,

16:30

different rules take over and have to be accounted

16:33

for, rules that general relativity ignores.

16:35

So we don't think singularities actually do

16:38

exist at the heart of any black holes in our

16:40

universe. We think, if black holes

16:42

are even real, that there's some other

16:44

kind of thing going on, something dictated by

16:46

a different theory of physics, not general

16:48

relativity, one that correctly incorporates

16:51

the quantum nature of our universe, a theory

16:53

we don't have today, so we can't

16:55

say what we actually think is inside a black

16:57

hole.

17:00

I think maybe Matthew's question is, like, let's say

17:02

black holes they're all a little bit different

17:04

inside, depending on their density, Like maybe

17:07

some of them are super dense

17:09

but collass into a singularity,

17:11

or maybe some do, or maybe some are more

17:14

like uh, let strings every fuzzballs. I

17:16

wonder if they can be different in that way inside,

17:18

but to us from the outside they all look the

17:21

same.

17:21

It's possible, and it depends on your flavor

17:24

of quantum gravity. If what he's

17:26

describing is true. There are no classical

17:28

black holes in the universe. They're all some weird

17:30

quantum version. And you're right, there could

17:32

be a variety, right, There could be some fuzzballs

17:34

and some dark stars and some white

17:37

holes and some other kind of crazy stuff

17:39

going on. And whether we could see

17:41

the difference on the outside also depends

17:43

on the details of the quantum gravity

17:45

theory. In some scenarios, you can

17:47

tell what's inside a black hole by studying

17:50

the patterns of the hawking radiation, which

17:52

might be quantum entangled with the details

17:54

of what's going on inside and leaking

17:56

that information out. There are other quantum

17:59

theories of black holes in which you still can't

18:01

get that information out even though it is inside

18:04

the event horizon. So it depends

18:06

on your flavor of quantum black hole.

18:08

But it's possible that all these things do really

18:10

exist in our universe.

18:12

Hmmm. It sounds like it sort of depends

18:14

on what you define as a black hole, right, Like,

18:16

if you define it as what a general

18:18

what relativity calls a black hole, then you

18:21

get one as er. But if you just define

18:23

it as something that has an event horizon

18:25

that doesn't let you look inside, it

18:28

is possible maybe to have different kinds

18:30

of black holes exactly.

18:31

And remember, not all of these objects even

18:33

have event horizons. When we talk

18:35

about a black hole, we sort of imply an event horizon.

18:38

But it's possible that some of the things

18:40

out there in the universe that we call black holes

18:42

don't actually have event horizons. We haven't

18:44

verified the event horizon nature

18:47

of those objects. They're just really

18:49

really small, really really massive, and

18:51

really really space bendy in the

18:53

way we expect black holes to be, but

18:56

we haven't like zoomed up close and proven

18:58

that they actually have event horizons. And

19:00

some of these theories don't create objects

19:02

with event horizons.

19:03

But some do, right, Like you could have a dark

19:05

star that does have event horizon.

19:07

Perhaps, yeah, some of them do. It

19:10

depends on the flavor or quantum gravity.

19:12

Hmm, all right, well

19:14

then so then the answer for Matthew is, uh,

19:17

it depends and we don't.

19:19

Know that

19:21

summarizes most of physics.

19:23

Yes, it depends that black hole

19:25

that's in your backyard.

19:27

What it means is that there's still so much to learn

19:29

about the nature of these objects. And the answer

19:31

to the question might not be it's this kind or

19:33

it's that kind, but it's all the kinds. I

19:36

love that possibility.

19:37

Mmm. So it sort of maybe depends on

19:40

what's actually going on, which we don't

19:42

have a clear theory about.

19:43

And we might not ever know.

19:45

Ever.

19:46

It might be that the universe prevents us from ever

19:48

seeing inside these black holes, or

19:50

that the information in the Hawking radiation doesn't reveal

19:53

what's inside them. It might be that we're

19:55

not smart enough to figure out the universe.

19:57

Who knows, Boy, I wish you had left

20:00

the question on a more positive note,

20:03

But it could.

20:03

Be that we figure it all out and then you go in ten

20:06

generations the latest. Daniel and Jorge

20:08

are explaining it all to you on their podcast.

20:11

All right, all right, yeah, that's good. That

20:13

doesn't leave us in a black hole. All

20:16

right, let's tackle some of our other questions. We have questions

20:19

here about the number of neutrinas

20:21

in the universe and also about

20:23

what it's like to bob up

20:25

and down on a gravitation wave. So

20:27

let's stick into those. But first let's take a

20:29

quick break. Right

20:43

we're answering questions from listeners, and

20:45

our next question comes from Sam from

20:48

British Columbia.

20:50

Hello, Daniel and Jorge, this

20:52

is Sam from British Columbia and thank you for

20:54

your podcasts and availability to answer

20:56

our questions. It is really appreciated

21:00

about neutrinos. You always mention how many

21:02

trillions are passing through the Earth every second.

21:05

This got me wondering about how many neutrinos

21:07

are estimated to exist in the universe,

21:10

as well as proportions for the other main

21:12

particle groups.

21:13

In the standard model.

21:14

It has often estimated that there are ten

21:16

to the eighty particles in the universe. When

21:19

he asked chat gpt for help, I

21:21

got back that each of the groups of leptons,

21:23

quarks, and bow sounds each were

21:25

in the order of ten to the eighty, and

21:28

then that there were significantly more electrons

21:30

than neutrinos, and also that there were about

21:32

ten to the eighty of each. I think

21:35

chat gpt once again was confused,

21:37

and I'm hoping you can help unconfuse

21:39

me.

21:40

Thanks all right, Well,

21:42

I'm glad that we were his second choice for answering

21:44

questions about the universe.

21:48

Oh man, chat GPT.

21:51

I guess chat gpt is

21:53

free. I guess you don't

21:55

have to listen to ads d I.

21:57

Think you have to pay for some version of chat GPT.

22:00

No version of it can be relied on to

22:02

answer physics questions. I see, well,

22:05

you know what they say, you get what you pay for. You

22:07

can do get what you paid for.

22:09

It sounds like chat jipt did not answer

22:11

Sam's question or game of an answer that maybe

22:14

it was confusing.

22:15

Well, it's also not designed to answer physics

22:18

questions. It's designed to generate

22:20

text which looks like the answers to questions

22:22

it's not designed to do any reasoning, or have

22:24

a model of the universe, or actually

22:27

think in any way, or be accurate

22:29

or explain things. So I wouldn't rely

22:31

on chat gpt to answer any questions.

22:34

Yet you could say that about anything.

22:36

Man, your toaster hasn't replaced

22:38

you yet.

22:39

Well, you know, it's like they say, chat chipet

22:42

is not designed to do basic math, right, Like, if

22:44

you ask it a math question, it may not give you the right

22:46

answer. But I've seen examples of like

22:48

asking Chad Gipt to check using

22:51

some sort of math toolbox, and then it gives you the right

22:53

answer.

22:53

Yeah, you know a stop clock is right a few

22:55

times a day, right, yeah?

22:57

Yeah, So you could ask chat gipt twice

22:59

a day to go read every

23:01

physics paper in the universe and

23:03

then come back to you with an answer, which is basically

23:06

what we do in this podcast.

23:07

And it's the wrong tool for the job. You know.

23:09

Its job is to generate text which resembles

23:12

answers, not to reason and

23:14

think and provide explanations. I

23:16

don't think it'll ever be a good place to ask physics

23:19

questions. I say, I see somedays somebody might

23:21

actually develop an AI which is good at

23:23

the reasoning and thinking and explaining. I'm

23:25

not ruling that out. I'm pretty sure that will happen

23:27

one day, but large language models

23:30

won't get there.

23:32

I think what you're saying is that we're the right tools.

23:34

Yes, ask us where we

23:37

were, just the pair tools,

23:41

just like data on Star Trek.

23:42

Right, there you go, There you go. Maybe

23:44

the next chat GBT should be

23:46

called Daniel and Cordy Chat DJ. All

23:49

right, well, let's get to Sam's question here. Samon

23:51

wants to know how many neutrinias there are

23:54

in the universe, right, Like,

23:56

what's a good estimate for the number of neutrinos

23:58

in the universe?

23:59

Such an awesome question because

24:02

there are so many neutrinos in the universe,

24:04

it's mind boggling.

24:06

Well, there's a lot of everything in the universe, right, Well,

24:08

there's only one me and one you. How do you know.

24:12

Ship a theseus man, if there's another

24:15

copy of me, it's not me.

24:18

Well, there could be one you that

24:20

has gone through the same experiences as you. Wouldn't

24:22

that be the same Anyways, let's

24:25

get back on track here. It's

24:27

a big universe. Asne wants to know how many

24:29

neutrinios are Why do you think he wants to know how many

24:32

there are? Like, why neutrinos? Why not how

24:34

many electrons or quarks there are

24:36

in the universe?

24:37

I think because neutrinos give us a window

24:39

into a deeper understanding of what's out

24:41

there in the universe. Like we're

24:44

made out of quarks and electrons, and that

24:46

feels like, Oh, that's the universe, what's all

24:48

that made out of? But as soon as you realize

24:50

that our senses are limited and

24:52

that there's so much more going on in the universe

24:55

than the little bits of matter that you and I are

24:57

made out of, it makes you wonder what's out

24:59

there, how much of it is there? And new trinos

25:02

are like the tip of that invisible matter Iceberg.

25:05

I see, Well, how would

25:07

you answer the question of how many new trinos there

25:09

are?

25:10

Yeah, so it takes a few steps. Basically,

25:12

you have to know how many protons there are in the universe,

25:15

and then you have to try to figure out how many neutrinos

25:17

there are per proton. And it turns

25:19

out that we can do both of those calculations.

25:21

Wait, why do we have to go through

25:24

protons?

25:24

Because the way we figure out how many new trinos there

25:26

are in the universe is by going back to the

25:28

very very early universe and understanding

25:31

how photons and protons and neutrinos

25:33

and dark matter all slashed around

25:36

and pushed against each other. It's this plasma

25:38

soup at the very beginning of the universe that reveals

25:40

the answers to all of these questions.

25:43

From measurements of the cosmic microwave background,

25:45

we can learn a lot about that plasma and

25:48

how it was slashing, and it tells us the

25:50

answers to all of these things. Then, specific

25:52

ways it tells us some ratios allow

25:54

us to get to these answers.

25:56

Like the beginning of the universe tells you the original

25:59

recipe of the universe kind.

26:00

Of yeah, exactly, And some of that hasn't

26:02

changed, and some of that has changed, and we know how

26:05

that has changed, and we can evolve that through time.

26:07

But it basically starts the machine and

26:09

tells us how things evolve through time.

26:12

But is it even possible to get this answer

26:14

because aren't neutrino's being created, for

26:16

example, all the time in the sun? Like,

26:19

are new neutrinos being made all the time?

26:21

Yeah? The specific number like to

26:23

the individual neutrino is

26:25

not very well defined because neutrinos are

26:28

quantum particles, and so they even have probabilities

26:30

of existing. Like you have a certain

26:32

reaction that might generate neutrinos.

26:35

Whether it actually did or not isn't

26:37

even determined until it interacts with some

26:39

classical objects. So from a quantum

26:41

mechanical point of view, getting the answer down

26:43

to like the individual neutrino is not

26:45

technically possible, and even zooming

26:47

out a little bit as you say, there are neutrino factories

26:50

in the universe and neutrinos being annihilated.

26:52

Neutrinos can be created and destroyed,

26:55

so the number is changing. But

26:57

it turns out that the number of neutrinos being created

26:59

in roid in the universe is really

27:01

tiny compared to like the huge

27:03

reservoir of neutrinos we already

27:05

have.

27:06

Well, how do you.

27:07

Know, because we think we understand those processes,

27:09

and we've measured neutrinos that come from space

27:11

and neutrinos that pass through the Earth. Neutrino

27:14

physics is something we're really starting to get a

27:16

grip on in like the last twenty years. So

27:18

we are a pretty good handle on how

27:20

many neutrinos are out there and how many are being

27:22

made by the Sun. We even see neutrinos

27:25

generated by crazy sources in other

27:27

galaxies. Neutrino

27:29

astronomy is something that's really come

27:31

into its own in the last couple of decades.

27:34

And so what's the picture. It's like the Sun

27:36

is making bazillions of neutrinos, but that's

27:39

very like a drip of water compared to

27:41

like we're swimming in an ocean of neutrinos.

27:43

Zechon what you're saying exactly. It's like asking

27:45

what's the volume of the Pacific? Well, you don't really

27:47

have to worry about evaporation and rain because

27:49

those are tiny details relative

27:52

to massive volume of water there.

27:54

And so then what's the connection to protons?

27:56

Why do we need to know how many protons

27:59

there are?

28:00

Know how many neutrinos there are per proton.

28:02

That's a measurement we can make back in the very

28:04

early universe. If you wind

28:06

the universe backwards, we see that it gets hotter

28:09

and denser. Right now, the universe is kind

28:11

of old and cold, very dilute,

28:14

very chill. But as you wind time

28:16

backwards and you undo the expansion, things

28:18

get very hot and very dense. Back to

28:20

some early state where there were protons

28:23

and there were photons, and there were electrons,

28:25

and there were also neutrinos zipping about,

28:27

and we can see photons from that moment. This

28:30

is the moment we call the surface of last scattering,

28:33

when the universe became transparent to those

28:35

photons, so they're still around. So

28:37

we can see a picture of what that

28:39

early universe plasma looked like. It's

28:41

called the cosmic microwave background radiation,

28:43

and we can see patterns in it. We see wiggles

28:46

and we see waves. Those wiggles

28:48

and waves are determined by how it's slashing,

28:50

which depends on how many protons there

28:52

are, how many photons there are, how

28:54

much dark matter there is. As you change

28:57

those fractions, that early universe plasma

28:59

slashed differently because those different

29:01

pieces all behave differently.

29:03

But even neutrinos were consequential

29:05

at the beginning of the universe because I thought neutrinos

29:08

were basically massless and they're

29:10

ghostly and they they don't really interact

29:12

with anything much. Isn't

29:15

there like a wide range of neutrino

29:17

proportions that could have been there at the beginning of

29:19

the universe.

29:20

Yeah. Absolutely. Neutrinos don't interact

29:22

very much, but they do have energy, and

29:25

so they affect the energy density of the universe,

29:27

which changes its expansion. And

29:29

because neutrinos are very very light, they sort of

29:31

fall into the same category as photons.

29:34

Back in the early universe, everything that was

29:36

moving almost at the speed of light or at

29:38

the speed of light gets counted kind of as

29:41

radiation. Remember we talked about this

29:43

once, and stuff that's moving very

29:45

very slowly gets counted as matter. And

29:48

so things that are moving as radiation do

29:50

affect the expansion of the universe

29:52

because they affect the energy density in this complicated

29:55

way. So you're right, the neutrinos are

29:57

weak, but they still have energy and that affects

29:59

the old overall balancing of these equations

30:01

in general relativity.

30:03

There's stills a piece of the pot.

30:05

Yeah, exactly. And it turns out there's

30:07

a huge number of them, so they have a pretty

30:09

big influence.

30:10

Oh, how big of a number, Like if you had a pie

30:12

chart of the universe at the beginning in

30:14

the Big Bang, how big is the neutrino slice.

30:17

Yeah, so you wouldn't even be able to see the protons

30:19

on that pie chart because there are approximately

30:21

one billion neutrinos for

30:24

every proton.

30:25

Well in terms of quantity, but in energy,

30:27

how big of a slice is it there?

30:30

The numbers are much more closely balanced. There

30:32

are many fewer protons, but protons

30:34

have a huge mass compared to neutrinos

30:36

that have almost no mass. On the other

30:38

hand, the neutrinos have a lot more kinetic

30:41

energy. Right they're moving really really fast,

30:43

They're almost at the speed of light, so

30:45

the energy is there are much better balanced that are in the same

30:48

order of magnitude. The numbers aren't exactly

30:50

determined, but the original question was about the

30:52

number of neutrinos in the universe,

30:54

and so there we need the number ratio,

30:57

and the cosmic microwave background radiation

30:59

tells us that there are like three hundred

31:02

and thirty million neutrinos per

31:04

cubic meter of space back then, and

31:07

there was less than one proton per

31:09

cubic meter, so the ratio is about a billion

31:11

I.

31:12

See, so neutrino's were a pretty significant

31:14

slice of the universe, but in terms of quantity, like

31:16

number of neutrinos because they're so small at

31:18

night that the number of them dwarfs

31:20

the number of protons around us exactly.

31:23

So there's this incredible ocean of

31:25

neutrinos back in the early universe

31:27

and still today. Like the density

31:30

of neutrinos has dropped because the universe

31:32

expands and everything gets more dilute except

31:34

for dark energy, but most of those neutrinos

31:37

are still around. It's called the cosmic

31:39

neutrino background, and it's something we're

31:41

searching for in neutrino experiments.

31:44

Does it depend still on the number of protons?

31:47

Is it the same ratio like three hundred and thirty

31:49

million to one or billion

31:51

to.

31:51

One, depends a little bit what you count as a proton.

31:54

Like some of those protons go on to make helium.

31:57

There's still protons in there, but like now

31:59

we call them helium instead of protons or hydrogen.

32:02

But most of those protons are still around, and most of

32:04

those neutrinos are still around, and because they're both

32:06

matter, they both get diluted in the

32:08

same way as the universe expands,

32:10

and so their ratio is approximately the same.

32:14

Then to get account of the number and neutrinos, we need a

32:16

count of the number of protons, So how many

32:18

protons are there in the universe.

32:20

So in the observable universe, we don't

32:22

know what's in the full universe right past

32:24

where we can see. We know the density

32:26

of protons, which is about a fifth per cubic

32:28

meter, and we know roughly the

32:31

volume of the observable universe,

32:33

which is like ten to the eighty

32:36

cubic meters or so, and that means

32:38

around ten to the seventy nine protons

32:42

in the observable universe. That's

32:44

ten with seventy nine zeros.

32:46

It's not even like a name for that.

32:47

Number, Sure there is, we can make one.

32:49

Up, right, there will be soon.

32:52

What's the number bananion?

32:56

Coincidentally, there's exactly one bananion

32:59

of protons in the universe.

33:00

Oh my gosh, such a coincidence.

33:03

Which means that there's a billion

33:05

bananians of neutrinos

33:08

in the universe, because it's about a billion neutrinos

33:10

per.

33:10

Proton, So ten to the what eighty

33:13

eight.

33:13

About ten to the eighty eight neutrinos

33:15

in the observable universe.

33:17

Observable universe, but the observable universe

33:19

is getting bigger every day. Right,

33:22

So that number is going up.

33:23

Actually depends a little bit how you think about distance.

33:26

The universe is expanding faster than the

33:28

speed of light, so the fraction of stuff

33:30

in the universe we can see is actually shrinking,

33:33

right, And eventually a lot of stuff is going to fall outside

33:35

of our horizon. So the number of particles

33:37

in the observable universe is actually decreasing.

33:40

WHOA, the universe is its outgrowing

33:43

how far we can see.

33:45

Yeah, exactly. The universe is expanding

33:47

faster than our horizon is, so

33:49

particles are disappearing from the observable

33:52

universe. That's another reason why

33:54

the number is not fixed.

33:55

Well, it may not even be fixed, right,

33:57

Like, maybe the universe is infinite, in which

33:59

case there's maybe an infinite number of neutrinos.

34:02

Yeah, exactly. In that case, you could still measure the

34:04

density of neutrinos like three hundred and thirty million

34:06

per cubic meter, but the total number

34:09

in the whole universe would be infinite. If

34:11

the universe is infinite, and if

34:13

the universe beyond a horizon is similar

34:16

to the bits that we see here, could be

34:18

that what's beyond the horizon is very different, right,

34:20

And then we live in a weird patch of the universe.

34:23

Right right, It depends and we don't

34:25

know, is what you're saying. But

34:29

what do you think is the ratio of like

34:31

in the universe, the ratio between neutrinos

34:33

and Daniels. Is

34:36

it infinite to one or is

34:39

there a fixed number?

34:41

That's the question philosopher has been wondering about

34:43

for thousands of years, and we're not going to answer it today

34:45

on the podcast.

34:48

That's right. We don't have the time. That's why we're not answering.

34:50

That's right, exactly. No, I think

34:53

if there are other Daniels out there, there's still

34:55

not me because I'm not experiencing them,

34:57

even if they think that there Daniel. I'm

34:59

experien think this one, which makes this one

35:01

different, which makes me unique. I'm only experiencing

35:04

one Daniel.

35:05

Unless they're having the exact same experience you are,

35:08

in which case, in which case, there the outside

35:10

can't tell the difference.

35:13

But we can from inside, right

35:15

inside the Daniel horizon, you can tell

35:17

which Daniel you are.

35:19

But your feeling of uniqueness is the same

35:21

feeling of unique is the other Daniel's

35:23

having.

35:23

Yeah, that's right, But I'm only feeling my feeling of

35:25

uniqueness. I'm not feeling bears. Oh, I

35:27

see.

35:28

So to you, there's only one Daniel, yeah, but

35:30

maybe to someone outside of the universe there

35:32

is an infinite number of Daniels.

35:34

Yeah. And it means and we don't know, And

35:36

to me is all that matters, because I'm the only consciousness

35:38

I'm actually aware of in the universe.

35:41

But I'm not asking what matters to you.

35:45

I'm wondering what matters to me, Daniel.

35:50

I don't know if you're even real.

35:51

So that's right, We're all in them

35:54

some AI's imagination. All

35:56

right, Well, I think that answers the question for Sam.

35:59

The estimate of the number of neutrinos in

36:01

the observable universe is ten to the

36:03

eighty eight neutrinos plus or

36:05

minus ten to the what eighty

36:09

seven.

36:10

Seven pluster minus

36:12

infinity.

36:12

Probably there's our pleasure minus infinity.

36:15

All right, Well, let's get to our last question

36:18

of the episode, which is about gravitational

36:20

waves and can you serve one? So

36:22

let's get into that, but first let's take another

36:25

quick break. All

36:38

right, Our last question of the day comes from Klai

36:40

wants to know about gravitational waves.

36:43

Howdy Daniel and Jorge. I

36:45

was wondering how would feel to be hit by

36:48

a gravitational wave? We have

36:50

detected infinitely weak waves

36:53

from Earth, but imagine

36:55

if we were close to two black

36:57

holes revolving around each other

36:59

and eventually colliding and merging. How

37:02

would it feel to get hit by a gravitational

37:04

wave? And would

37:06

it be the same as a wave? And finally, would

37:09

your organs be damaged?

37:11

Interesting question. It

37:13

sounds like Clay is planning a trip.

37:15

Perhaps.

37:18

I think Klay wants to experience the universe,

37:20

wants to feel gravitation waves,

37:22

not just read about it online.

37:25

Well, I think one of the things is that, first

37:27

of all, we're all experiencing gravitation waves

37:29

right now.

37:30

Right, Yeah, that's true. Gravitational waves

37:32

are everywhere. They fill the universe because

37:34

they're generated anytime any

37:36

mass is accelerated. So

37:39

you're in orbit, you're generating gravitational waves.

37:41

You get out of bed, you're generating gravitational

37:44

waves. Gravitational waves are everywhere,

37:47

right.

37:47

We're experiencing them. We're generating them

37:49

like if a car accelerates in front

37:51

of me, technically gonna

37:54

feel or I'm going to experience

37:56

the gravitational wave generated by the

37:58

car.

37:58

Right, It's very hard

38:00

to feel these things because they're very, very gentle.

38:03

Remember that gravity is like the dominant

38:05

force and the structure of the universe, but it's also the

38:07

weakest force, if you even call it a force,

38:10

so much weaker than the forces that hold your body

38:12

together for example.

38:13

Right, they're super mellow, hard

38:16

to detect, but we can detect some of the ones that

38:18

come from deep in outer space,

38:20

that come from black holes or heavy

38:22

things circling each other and then colliding.

38:25

Exactly. The way to detect gravitational waves

38:27

is to look for extremely loud

38:29

sources of them, things that make very dramatic

38:32

gravitational waves. And so two

38:34

black holes, which are two enormous

38:36

masses orbiting each other very very

38:38

quickly just before they collide, are

38:41

very loud sources of gravitational

38:43

waves. So even though we're very

38:45

far from them, we can be like a billion light

38:47

years away, we can still detect

38:50

those gravitational waves here on Earth with

38:52

super sensitive detectors.

38:54

Right here on Earth. By the time that they get

38:56

to us, they're super weak because I guess, like

38:58

a ripple in a laketational waves

39:00

get weaker as they expand right from their

39:02

source.

39:03

Yeah, as you get further from the source, they get

39:05

weaker and weaker.

39:06

Right, And as you said, the ones we're detecting now

39:08

with LIGO, which is the big physics instrument

39:11

we have here on Earth, those happen

39:13

billions of light years away. And

39:16

I think the Khalist question is, like,

39:18

what if you're closer to that source of

39:20

gravitational waves, Like, what if you're

39:22

right next to those two black holes glide in? What

39:25

would it feel like to have this giant

39:27

gravitation wave pass three?

39:29

Yeah, it's a really cool question to think about it. I think

39:31

we should like zoom in on what happens

39:34

first to like individual particles

39:36

in your body, and then think about what

39:38

that would feel like.

39:40

There's a way. Wait, but the scenario is how close am

39:42

I to these gravitational waves?

39:43

So imagine we're just like a few tens of thousands

39:46

of kilometers away from these two

39:48

black holes that are orbiting each other.

39:50

Aren't black holes usually bigger than a few tens

39:53

of thousands of kilometers or are you imagining

39:55

like two small ones?

39:56

Well, the kind of collisions we've seen are between

39:59

black holes that have like thirty to fifty

40:01

solar masses, and those have an event

40:03

horizon radius of like one hundred kilometers

40:05

or less, So if you're thirty thousand

40:07

kilometers away, you're definitely not inside the

40:09

event horizon.

40:10

Okay, so these are pretty small black holes.

40:12

Yeah, but these are the kinds of black holes we've been

40:14

able to see collide.

40:16

Ooh, all right, so then we're a few

40:18

tens of thousands of kilometers away from these

40:20

two black holes smashing

40:22

into each other exactly.

40:23

And on a human, if you're like thirty

40:26

fifty thousand kilometers away from two

40:28

black holes that have like the mass of thirty or

40:30

fifty times the sun, then

40:33

you're going to feel what's called a strain of

40:35

about one millimeter. The strain

40:37

is how much your body is getting squeezed

40:40

by the gravitational wave. And this is

40:42

what we measure also here on Earth with LEGO,

40:45

we have these innerferometers, these very long

40:47

laser legs that get squeezed and

40:49

lengthened as the gravitational wave passes

40:51

by. The ones here on Earth are so

40:54

faint that the measure strains of like one

40:56

times ten to the negative twenty one, which

40:59

means that like the two mile leg

41:01

of the inferometer gets shorter by that

41:03

factor. It's a really really tiny factor.

41:05

But unless how much like space

41:08

is being stretched or compressed, right, Like,

41:10

not necessarily something in space,

41:13

right, because it's something in space is sort of

41:15

holing on to itself. But you're talking

41:17

about the stretching of space itself.

41:20

Yeah, the changing of the distance between two

41:22

particles. For example, So imagine

41:24

you have two particles and you're a few tens

41:26

of thousands of kilometers away from these black

41:28

holes that are e merging, and they're generating

41:31

gravitational waves. What's going to happen

41:33

is they're going to change the distance between

41:35

the two atoms. Right, So, for example,

41:38

that the distance gets longer than those

41:40

two atoms, if they were like bound together somehow,

41:43

then they're going to feel an attractive force to pull

41:45

them back to where they were in equilibrium.

41:48

If the gravitational wave is very slow,

41:50

they're going to be able to basically stain in equilibrium

41:53

and nothing really happens. But if the gravitational

41:55

frequency is high, if the sort

41:57

of squeezing and pulling and pushing is fast,

42:01

they'll effectively feel a force and they might start

42:03

to oscillate back and forth. That's kind

42:05

of what happens in Lego.

42:07

Like the stretching of space is kind of like how

42:10

much space wants to stretch

42:12

you.

42:13

Yeah, the distance between those two particles

42:15

or the two mirrors in Lego gets

42:17

longer or shorter based on the gravitational

42:20

wave. But then the interaction between the two

42:22

particles, or the structural strength of the thing, whatever,

42:24

has a natural length that it wants to be at,

42:27

so to try to return to that natural length.

42:29

Like if you imagine a spring between these

42:31

two particles, you pull them apart,

42:33

well, the spring is going to pull them back.

42:35

Together, right, So then you're saying, like, if I'm

42:37

a few tens of thousands of kilometers from

42:39

these black holes, and I would feel about

42:41

a one millimeter stretch in my body,

42:44

or space would want to stretch my body about

42:46

one millimeter mm hmm.

42:47

And based on the frequency, you're going to get

42:50

shaken by one millimeter. It's

42:52

not like you just get pulled by one millimeter in

42:54

one direction and then you stay there. A gravitational

42:56

wave is a wave. It's oscillating,

42:59

and depending on the frequency, if it's like a fast

43:01

wave or a slow wave, it's going

43:03

to shake you at that speed, so it might like pull

43:05

you in one direction and then squeeze

43:07

you in that direction and pull you in the other direction.

43:10

So there's this pulling, the stretching, and the

43:12

squeezing. So right now we're talking about

43:14

the amplitude about one millimeter,

43:17

but the frequency of that is also important,

43:19

and that depends on the orbits of these black holes.

43:22

How many times are they passing around each other.

43:24

That determines the frequency of this gravitational

43:26

wave. If you're nearby these black holes,

43:29

you're basically going to get shaken from the

43:31

inside.

43:31

Right, And you're saying kind of depending on

43:33

the frequency, it might be dangerous

43:36

or not. Like if it was shaking really

43:38

slowly, you probably your body can probably

43:40

adjust to that shaking. But

43:42

if it's shaking super fast, then it might scramble

43:45

your insides.

43:46

You might scramble your insides. You might also

43:48

experience it in a weird way, like

43:50

it might be like being at a concert.

43:53

Sound waves at a concert also shake

43:55

your body and you experience them as

43:58

sound. If you're out in space near

44:00

two black holes, you might literally

44:03

hear the gravitational waves

44:05

because like the drums in your ear will

44:07

get shaken.

44:08

Whoa as put everything else in your

44:10

body.

44:11

As would everything else, Just like at a concert.

44:13

Right when you're in the moshpit at that concert,

44:15

your toes are getting shaken, even though your ears

44:17

are the only ones actually transmitting sound to

44:20

your brain. The same way a gravitational

44:22

wave can be squeezing and pulling on your whole body,

44:24

but your ears might be the only ones picking it up.

44:27

I've never been in a moshpit, but I'll take your

44:29

word for it, so

44:31

you might feel it. But is it dangerous?

44:34

Like if it's high frequency enough, and these

44:36

things are pretty high frequency by the time they smash

44:38

together, it's like super

44:40

high frequency, right.

44:41

Yeah, they can get to be very high frequency. And

44:44

actually the frequency they experience is

44:46

even higher than we observe because

44:49

there's gravitational time dilation. These

44:52

black holes, of course have super high curvature,

44:55

and now one black hole is near another one,

44:57

it's experiencing the gravitational time dilation

44:59

of that black hole, so time

45:01

is super slowed down. So what we're

45:03

observing is the slow down gravitational

45:06

wave being emitted by these event horizons.

45:09

That's already taken into account. If

45:11

it wasn't, then the frequency would be much

45:13

much higher.

45:15

Well, I guess from what we know of these

45:17

smashing black holes or the ones we've seen,

45:20

then the frequency we've seen, and how

45:22

fast there actually are closer to the source,

45:24

would they actually kill you at this

45:26

distance? Like at some point they'll start to rip

45:28

apart the bonds between the proteins

45:31

in your body, right, or you

45:33

know, it'll basically scramble

45:35

your brain.

45:37

I don't think I can say. It depends a lot on the internal

45:40

biological friction, like how

45:42

much energy is actually going to get absorbed,

45:44

and how squishy your body is, how

45:47

resilient it is, depends a lot on

45:49

the exact kind of tissue. I

45:51

think all I can do is treat your body

45:53

as a sphere with ears and say

45:56

you'll probably hear it happening.

45:58

But you can probably make that calculation, right, Like

46:00

you can calculate this spignification

46:02

point of a black hole, right, like

46:05

the point at which it would actually tear you apart

46:07

falling into a black hole. You can probably do that for gravitational

46:10

wave, right.

46:10

Yeah, But the energy that gets absorbed depends

46:13

on this internal friction. Like if

46:15

there's no internal friction to your object,

46:17

it can get squeezed and squished and then be

46:19

totally unharmed. So how much

46:21

energy is deposited, how much damage

46:24

is done depends entirely on the

46:26

internal friction of that object. It's

46:28

not just dependent on the tidal forces.

46:31

Right right, But I imagine, I mean, we don't

46:33

have to do it now, or there's no pressure for you to

46:35

come up with an answer. But like, if you could

46:37

make the calculation for like a typical brain,

46:40

what are some of the maximum accelerations

46:42

a brain can withstand before it turns into

46:44

you know, mush, and you can maybe

46:46

backtrack to find what kind

46:48

of frequency of gravitation waves would kill

46:51

you.

46:51

Yeah, probably somebody who knows something about the brain

46:53

could figure that out.

46:56

What do we know about brains? We just use

46:58

them.

46:59

I'm going to guess the answer is it depends,

47:01

and we don't know exactly.

47:03

You read my brain. That's exactly

47:05

what I was.

47:06

Thinking, exactly. I just

47:08

got a gravitational wave idea into my brain.

47:10

But again, I feel like this is just firm

47:13

standing tens of thousands of kilometers away.

47:16

May you say, maybe we might survive this. I don't

47:18

know, because don't these things go

47:20

pretty high frequency? Even a one millimeter strain

47:23

might be enough to mois your brain.

47:24

One milimeter strain is pretty big, so

47:26

I think it might be enough. I mean, I think one

47:28

millimeter strain is much more than you ever

47:31

experienced at a concert. Even very

47:33

very high intensity sound waves

47:35

don't actually like move the molecules

47:37

in your body by a millimeter. That's a pretty

47:39

huge displacement. And you've got lots

47:42

of really sensitive things inside your body that are

47:44

much smaller than one millimeter, So one

47:46

millimeters squeezing and stretching could

47:48

totally destroy like really sensitive

47:50

little biomachineries.

47:52

So smash

47:54

bit, not moshpit, like

47:58

your brain gets washed.

47:59

Yeah, I think it might be like being in a blender.

48:02

Great, then I imagine

48:05

if you get closer to these circling

48:07

black holes and it just gets more dangerous, right,

48:09

because then the waves could get much more intense.

48:12

Exactly, the amplitude of the waves just grows

48:14

as you get closer. The strain gets larger

48:17

and larger.

48:17

What if you're just a thousand kilometers

48:20

away, how big would the strain be.

48:21

Well, it goes like one over r a

48:23

little, which is a little bit weird, And

48:26

so a thousand million three times

48:28

closer would be thirty times if

48:31

you're like thirty or ten times closer. If

48:33

you're ten times closer, it's going to be ten times as.

48:35

Strong, times times ten to the three. No,

48:37

I mean a q because because

48:40

your are went down a tenth,

48:42

So then doesn't the intensity go

48:44

up by a queue?

48:46

The strain goes like one over r oh

48:48

linear? You sure it's inverse linear?

48:51

Yeah?

48:51

Oh, it's linear, all right, So then you would

48:53

experience it a one centimeter strain.

48:56

Yeah, ten times closer you get one centimeter

48:58

strain.

48:58

Oh wait, yeah, that would be a lot.

49:02

That would definitely be a lot. CLI's

49:05

asking how would it feel to get hit by

49:07

a gravitational wave? Would your organs

49:09

be damaged? It depends a lot on the

49:11

distance you get close enough, it could definitely

49:13

scramble you. You get not too

49:15

close, then you could probably hear it, like

49:18

physically hear it without being destroyed.

49:20

But I don't know exactly where that line is, and

49:23

I don't recommend you figure it out.

49:24

Mmmm.

49:25

That's right. Keep it a thought experiment, Keep

49:27

it a brain experiment to save your brain. All

49:31

right. Well, I think that answers all of our questions.

49:33

Some pretty interesting ideas here. Overall,

49:36

the picture is that the universe is still mysterious.

49:39

There's a lot we don't know, and there's still

49:41

a lot of questions we can ask about it

49:44

for us to explore.

49:45

But we love that you ask these questions,

49:47

and we love trying our best to answer them.

49:49

We don't always know the answer. That's sort of the game

49:51

of physics, figuring out where the edge of

49:53

knowledge is and trying to push it forward a tiny

49:56

little.

49:56

Bit at least. That's one of the games one Daniel

49:58

can play.

50:00

What can we figure out if we have even more Daniels.

50:04

All right, well, we hope you enjoyed

50:06

that. Thanks for joining us. See you next

50:09

time.

50:14

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50:18

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50:25

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