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Some. People just know the best rate for

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you as a rate based on you with

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our state, not a rate based on Terry

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who keeps. It

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makes the car behind them. Out

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with Dr was and all state at and

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could increase with high risk driving Allstate Fire and Casualty

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Insurance Company and Affiliates Northbrook, Illinois. I

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don't think the average person and

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to be perfectly clear, you are

0:41

far from the average person so

0:43

this will be easy for you.

0:46

Appreciate just how. Messy.

0:49

Science. Is. Popular.

0:51

Conceptions of Science and I'm looking

0:53

at you and particular, Science Journalism

0:55

paint this simplified picture of how

0:58

science works. Were there is a

1:00

problem. A bunch of scientists get

1:02

work, they work really hard in,

1:04

they produce an answer, and their

1:07

theories are either right or wrong.

1:09

Black or white in there, either

1:11

accepted by the evidence or they're

1:13

totally rejected by everybody. Either a

1:16

scientific idea works, Or. It

1:18

doesn't work. But. That's not even

1:20

close to how the scientific process

1:22

actually unfolds. And wall All save

1:24

a full discussion of the process

1:27

of science for a later episode

1:29

of Feel Free to Ask To

1:31

accelerate their timeline, I want to

1:33

use something called the Cosmic Microwave

1:35

Background Cold Spot as an example

1:37

of how we can have a

1:39

really, really solid understanding of the

1:41

big picture and not be entirely

1:44

sure what's going on with some

1:46

of the details, not be confident

1:48

in what the potential. Answers are

1:50

and whether it's a worthy of

1:52

excitement or not and not even

1:54

agree about whether what we're seeing

1:56

is even real. And how

1:58

all that can? Then, and

2:01

it doesn't affect the

2:03

big picture because scientific theories

2:05

are not perfect. Near.

2:08

That sounds pretty messy. But

2:10

this. Is what science actually looks like.

2:13

To be perfectly honest, in today's episode,

2:15

I'm not going to focus too much

2:18

on the physics of what the cold

2:20

spot could be. Spoiler alert. Our best

2:22

guess is that it's a super void

2:25

along the line of sight, but this

2:27

is disputed and I actually want to

2:29

talk a lot about. Why?

2:32

The cold spot. Might. Be

2:34

interesting and why we think it's interesting and

2:36

so to do that I have to dig

2:38

into the physics of the Cmb itself because

2:41

microwave background in I have to discuss. Like

2:43

What? Are the statistics of at

2:45

How do we approach our understanding of

2:47

the sea and beats so that it

2:49

tells us why? The. Cold Spot

2:52

really sticks out and so that's why

2:54

I'm gonna spend most of the episode

2:56

on and then we'll talk about some

2:58

solutions and talk about how the solutions

3:00

kind of sorted don't work and how

3:02

this actually isn't a problem solved for.

3:05

So first let's dig into the Cmb.

3:07

I don't wanna say Cosmic Microwave

3:09

Background a million times in this

3:11

episode, so I'm just going to

3:13

say see and so forever. For

3:15

now, you're going to hear Cmb.

3:17

That is Cosmic Microwave Background Cosmic

3:19

Microwave Background. Cmb. It's It's one

3:21

of the earliest predictions of the

3:23

Big Bang Theory. It's very sorry

3:26

for. like, once you realize that

3:28

we live in expanding universe, the

3:30

Cmb just pops out of it

3:32

as a natural consequence of done

3:34

entire series on the Cmb. It's

3:36

a wonderful aspect of our universe.

3:38

But the short version is our universe

3:40

right now is big and cold. Everything

3:42

spread out is. this was not the

3:45

case billions of years ago as you

3:47

go back in time, or universes smaller

3:49

and hotter and denser. At

3:52

one point, Of. then silly

3:54

far enough in the distant past everything

3:56

is so small and so hot in

3:59

so dense it's a plasma. It's

4:01

like the gas that's inside

4:03

the sun or a lightning bolt. The

4:05

electrons are ripped off of the atoms

4:08

and everything's a hot mess. Now

4:10

the universe back then was a

4:12

plasma and it was expanding and

4:14

cooling eventually cooled off to become

4:16

not a plasma anymore. That

4:19

process released radiation.

4:21

The radiation completely soaked

4:24

the universe. It

4:26

was also really hot at the time it

4:28

was released. It was around 10,000 Kelvin but

4:30

the universe has expanded. It stretched out

4:33

that light and now it's down in

4:35

the microwave and it surrounds us. This

4:37

leftover light from when the

4:39

universe transitioned from being a hot

4:41

plasma to a slightly less hot

4:44

neutral gas. This radiation

4:47

was emitted by every point

4:49

in the universe. So the

4:51

room you're in right now,

4:54

the space that the earth, the solar

4:56

system currently occupies was once a long

4:58

time ago a plasma and

5:00

then it wasn't and it released this

5:03

radiation and this radiation that was generated

5:05

right here is now billions of

5:07

light years away because it went away from

5:09

us. If you look at

5:11

the Andromeda galaxy, a long

5:14

time ago the Andromeda galaxy was

5:16

that region of space was

5:18

a hot dense plasma. It

5:20

generated cosmic microwave background, CMB.

5:23

That light now went past

5:25

where we are and is now on

5:27

the back end billions of light years

5:30

away. What we see when

5:32

we look at the CMB, when we look

5:34

up in our sky and we put on

5:36

our microwave goggles and we look at this,

5:39

we see it as a

5:41

shell that surrounds us in all

5:43

directions. What we are seeing is

5:46

the light that was generated

5:48

in distant parts of the

5:50

universe that is just now

5:52

reaching us and this distinction

5:54

is absolutely crucial for understanding the cold

5:56

spot, what it is and why we

5:58

care about it. because

6:02

The CMB was not generated

6:04

in one particular place. It

6:06

was generated everywhere at once

6:09

so the metaphor I like to use and

6:11

we'll come back to this metaphor a lot in this episode

6:14

is Imagine if

6:16

everyone in the world started

6:18

shouting and just once Like

6:20

we could do it right now like three two one. Ah Like

6:23

we just shout everyone shouts once and let's

6:25

say the shouts are loud enough To

6:28

be heard around the world because I need

6:31

this to work for the metaphor everyone

6:34

shouts everyone on the entire planet Earth shouts

6:36

at the exact same time just once a

6:38

big burst just like the CMB it was

6:40

a big burst of light. Yes, it took

6:43

10,000 years for the light to actually Transition

6:46

and for the process to unfold in

6:48

the light to admit but in cosmological

6:50

scales, that's essentially instant Everybody

6:52

shouts. So if you're standing you shout

6:55

your shout now goes out into the

6:57

world. You never see it again. It's

6:59

gone and From

7:01

your perspective you start hearing shouts

7:04

First you hear the shouts from the people nearest

7:06

you and then you give a little bit of

7:09

time And then you start to hear the shouts

7:11

from the people Say

7:13

in your town or your city and

7:15

then you start to hear people shouting

7:18

from your state your country Moves

7:20

further and further and eventually you

7:22

start hearing shouts from people over

7:24

the horizon You

7:27

can't see the people that are shouting

7:29

that shout was emitted by people well over

7:32

the horizon But now their sound is finally

7:34

reaching you. So as time goes

7:36

on you see this ever Expanding

7:39

or hear this ever expanding

7:41

shell of shouts because the

7:43

people nearest you started shouting

7:45

or they shouted once the shout Hey you you heard

7:47

it. Ah, you heard them But then

7:50

that sound wave moves past you

7:52

and now there's someone standing behind

7:54

them on the other side room

7:56

And then that sound wave hears

7:58

you so you're always hearing shouting.

8:01

You're always here like, ahhhh, this

8:03

continuous shout, but it's because you're

8:05

picking up people from a wider

8:07

and wider circle until you

8:09

reach all the way over the horizon and

8:11

then it just keeps going. You don't see

8:13

the people anymore, but you can still

8:15

hear their shouts because enough time has passed for their

8:18

shout to wave over you. This

8:20

is important because the

8:23

Cosmic Microwave Background, the CMB,

8:26

is almost perfectly

8:29

unified. It

8:31

has a nearly perfect temperature right around 2.7

8:34

Kelvin, which is a lot cooler than when

8:38

it was emitted, and it's

8:40

not perfect. There are tiny,

8:42

tiny differences in temperature. These

8:44

differences in the temperature, if you start looking,

8:47

if you look at the CMB sky and

8:49

you look in any particular direction and you

8:51

try to measure its temperature, it's right around

8:53

2.7 Kelvin, but there will

8:55

be one part in a million differences

8:57

from place to place. One

9:00

part in a million. Where you look in

9:02

one direction, it will be one

9:05

millionth cooler. Look in another

9:07

direction, it will be one millionth warmer.

9:09

There are these tiny little imperfections, and

9:12

these imperfections are the juiciest part of

9:14

the CMB. The existence of the CMB

9:16

tells us that the Big Bang Theory

9:19

is probably correct, but

9:21

the differences tell us so

9:23

much rich information because magically,

9:25

actually scientifically, we understand why

9:27

the CMB is not perfect.

9:29

We actually expected tiny little

9:31

differences in temperature from place

9:33

to place, and

9:35

there are two general kinds

9:38

of differences that

9:40

appear in the CMB. One

9:43

are tiny little density differences,

9:46

which translate into

9:48

tiny little temperature differences that

9:51

are exceeded by inflation. This

9:53

Event that we hypothesize happened in the

9:56

incredibly early universe that set the stage

9:58

for the growth of the CMB. Prose

10:00

of galaxies in large structures in

10:02

the University started actually of we

10:04

believe as tiny little quantum fluctuations

10:07

in the in the fabric of

10:09

space time itself. It's an

10:11

inflation I gotta admit is not the greatest

10:13

idea, but the best When we got up

10:15

there's there's a lot I could say about

10:18

inflation and I haven't previous episodes. This.

10:20

Event of inflation seeded what it

10:22

did with laid the groundwork is

10:24

is totes these sub atomic like

10:27

truly be subatomic differences made them

10:29

are like little tiny density differences.

10:31

So that's tiny packets of the

10:33

universe where a little bit more

10:35

dense than average and over here

10:37

is a little bit less dense

10:39

than average. When the Cmb was

10:41

generated we see that is tiny

10:43

little temperature differences. So we get

10:46

a map of what the universal

10:48

looked like by looking at these

10:50

temperature. Differences: We get a map

10:52

of what's the universe actually looked

10:54

like Of the density difference is

10:56

the matter differences throughout the universe.

10:58

These are relatively small, their tiny

11:00

little speckles. And if you look

11:03

at a map of the Cmb

11:05

if you'd be going to your

11:07

favorite search engine and type Cmb.

11:09

You will not see the average.

11:12

Two. Point Seven Kelvin math because

11:14

ah, it's pretty boring. His hits

11:16

that as a blob of the

11:18

single color, you will be seeing

11:21

maps of these tiny little differences

11:23

in their tiny little speckles. These

11:25

little speckles were seated by inflation.

11:28

Be speckles, grow up. Eventual A

11:30

D become galaxies to become clusters,

11:32

become the larger structures in the

11:34

universe. But they need another billion

11:37

years or so. From.

11:39

The Cmb in order to grow

11:41

up to that kind of scale.

11:43

And so at this time at

11:45

the Cmb what we're seeing are

11:47

these tiny little baby fluctuations which

11:49

is amazing. and then there's

11:51

another kind you will see on

11:53

the cmb map there are these

11:55

large splotches speed large swatches are

11:58

actually generated by sound waves around

12:00

in the early universe. I'd love to

12:02

do an episode on that. So

12:05

you will see, the point is you

12:07

see different kinds of splotches, tiny splotches

12:09

and big splotches. And we

12:12

have an understanding of

12:14

where these density differences, temperature differences,

12:16

these splotches come from. We understand

12:19

plasma physics. We actually understand the

12:21

physics of the early universe, at

12:24

least the early universe that

12:26

generated the cosmic microwave. And

12:29

here's where I need to bring

12:31

in my sound wave metaphor again,

12:33

because we can't predict exactly

12:35

what the fluctuations will look

12:38

like. We can't

12:40

predict, even though we understand the

12:42

physics of the CMB, and we

12:44

understand how the small splotches are

12:46

generated, how the big splotches are

12:48

generated, all the wiggles appear.

12:50

We know how it comes about. We understand

12:53

the physics of how these are

12:55

created, but we can't say,

12:57

oh yeah, you look in

12:59

this direction, there will be a cold spot

13:02

that is 50 micro

13:04

Kelvin colder than average. And if

13:06

you look in that spot, you

13:08

will see a warm spot that

13:11

is 15 micro Kelvin warmer than

13:13

average. You can't, we can't do

13:15

that. We can't predict exactly what

13:18

the CMB will look like. We

13:20

can only predict

13:23

the statistics, the properties

13:27

of the CMB. And

13:29

to go back to the sound wave

13:32

metaphor, everyone shouts across the world. Once

13:35

the shouts start coming from

13:37

over the horizon, once there's been enough time

13:40

that you're hearing shouts from beyond

13:42

the horizon, you

13:44

can't say, oh, There's

13:47

going to be a loud shout with

13:49

this pitch coming from this direction. And

13:52

If I look to the west, there'll

13:54

be a slightly quieter shout coming from

13:56

that direction. You Can't do that because

13:58

you can't attach a. Sound To

14:00

a person you can see the person

14:02

that's generating the sound and in our

14:05

universe. When we look at the Cmb,

14:07

we can't see that part of the

14:09

universe any more is our universe has

14:12

expanded that little region. If you point

14:14

in any one direction and look at

14:16

the Cmbs, there was a part of

14:19

the universe that generated the Cmb lived

14:21

that Cmb light as now left that

14:23

part of the universe in as crawled

14:25

across the cosmos on it's way to

14:28

us. In in the meantime

14:30

that patch. Of the Universe is now

14:32

expanded away from us because we live in

14:34

an expanding universe. And. We can't

14:36

see it anymore. We. Only get the

14:39

Cmb like we have no idea what's going

14:41

on in that. Part of the universe

14:43

anymore. It's beyond our observable horizon.

14:46

Of the light left long enough ago that

14:48

is just now reaching us, but we have

14:50

no idea what's going on there now. We.

14:52

Can't attach. A

14:55

visual like oh, right now there's a

14:57

galaxy over there and a cluster of

14:59

and so we know. I'll add that

15:01

see and be like that it generated

15:03

would have had this patterns we can't

15:05

do that. Just like

15:07

if everyone shouted at once. I.

15:10

Forsee to say okay, I know, I

15:12

know, I know that person they're They're

15:14

going to shout really loud and the

15:16

up there it is it matched it.

15:18

Okay, it's A but once he gets

15:20

far enough away where you can see

15:22

the people anymore for generating the shouts,

15:25

you lose the ability to predict exactly

15:27

what shouts. Are. Going to come from?

15:29

What direction? And how loud they're going

15:31

to be, in what pitch they're going to

15:33

be. And with the Cmb we can predict

15:35

exactly what's the pattern will be if you

15:38

look up the Cmb. We. Can't

15:40

predict. That exact pattern with

15:42

with the cold spots over there

15:44

and sunspots over there in the

15:46

sizes over here, we can't do

15:48

that. Instead, we can only predict

15:51

the statistics we can save with

15:53

the average spot sizes. With.

15:55

the average temperature differences would is

15:57

a range of temperatures differences that

15:59

we can expect. What are the

16:01

range of spot sizes that we

16:03

can predict? This is

16:05

absolutely critical because this gets into

16:08

one of the issues with the cold spot. This

16:11

does introduce a fundamental

16:14

limitation to the certainty of

16:16

our calculations, but it's the best we're gonna get.

16:19

We can only look at the CMB statistically.

16:23

And just about everything with the CMB is

16:25

fine and dandy. We understand where the splotches

16:27

come from. They tell us a

16:29

lot about what the universe was cooking when

16:31

it was very young. Over

16:34

the decades, we've built ever more refined telescopes

16:36

and satellites for getting a better look at

16:38

this CMB. It's just about

16:40

one of the biggest success stories in

16:42

science and some in fact some argue

16:44

that it's the most precise measurement ever

16:46

made in science. We can debate that

16:48

another time. It's a cornerstone of the

16:50

Big Bang Theory. You're welcome to create your own model

16:52

of the history of the universe, but your first job

16:54

is going to be explaining the nature of the CMB

16:56

and good luck with that. You'll need it. The

16:59

CMB is awesome. I've had first-hand experience

17:02

working with the CMB for

17:04

a few years. I was a member

17:06

of the Planck collaboration. The Planck was

17:08

a satellite launched by the European Space

17:10

Agency in NASA to create the highest

17:12

resolution most detailed global sky map of

17:14

the CMB ever. We did it. Good

17:16

job us. Everything's

17:19

great. We actually understand the CMB.

17:21

We understand the statistics of the

17:23

CMB. We understand the physical processes.

17:25

We can't predict exactly which cold spot

17:28

and hot spot will appear where. But

17:31

we can say on average, yeah, we expect

17:33

a certain number of cold spots, a certain

17:35

number of hot spots. They're gonna be roughly

17:37

this size or have this these there gonna

17:39

be so many small ones, so many medium

17:41

ones, and so many big ones. Like we

17:43

could do this and then there's the cold

17:45

spot. Now there

17:48

are a lot of cold spots on the

17:50

CMB. In fact, it's half the spots. The

17:52

other half are hotter than average. But

17:54

the cold spot stands out. It

17:57

even stands out visually if you look at a map of

17:59

the CMB. where the entire sphere of

18:01

the sky is compressed into a weird,

18:03

vaguely oval shape, the cold

18:05

spot is down in a little to the

18:07

right. And if you see like a bluish

18:10

spot, almost always these maps are painted blue

18:12

for cold. It looks weird.

18:14

You can see it on the sky. If

18:16

you look through the direction of the

18:19

constellation Eridanus, you're looking in the direction

18:21

of the cold spot. You

18:23

might need microwave sensitive goggles to see it, but

18:25

it's there. Now the cold spot

18:27

has got a good name and you know I'm

18:29

a fan of solid names in astronomy and physics.

18:32

The cold spot is cold. Depending on how you define the

18:34

edge of the spot, it's about

18:37

70 micro kelvin colder

18:39

than average. And

18:41

that's compared to the average,

18:44

not important cold spot. That's only roughly

18:46

18 micro

18:48

kelvin colder than average. So right

18:50

there, it's about four to

18:52

five times colder than the average

18:54

cold spot on the CMP. And

18:57

in its deepest part, in the very center of the cold

18:59

spot, it's about 140 micro kelvin colder

19:02

than average, which is a lot for CMP. I

19:04

know it's like one part in 100,000, one part

19:06

in a million, getting around in that ballpark.

19:11

But for the CMP, that's a lot. That's

19:15

almost 10 times colder than

19:17

average. And

19:19

the cold spot is also big. It's about

19:21

five degrees across, which doesn't sound like

19:23

a lot, but that's about 10 full moons

19:26

lined up side to side. The

19:29

average spot on the CMP is less

19:31

than one degree across. So not only

19:33

is the cold spot weirdly cold, it's

19:35

also weirdly big. And

19:38

this is where things get tricky. We

19:40

first spotted the cold spot with the WMAP probe

19:42

in the late 1990s, early 2000s, and then

19:46

the Planck satellite. And then we wondered

19:48

like, okay, maybe there was some measurement

19:51

error. Maybe aliens were

19:53

messing with us. Maybe

19:55

There was just something weird happening with our instrument

19:57

when it happened to look in that direction of

19:59

the sky. They are. But then the

20:01

Planck Satellite confirmed the existence of the

20:03

cold Spot, so wasn't just a fluke

20:06

of the instrument or measurement error or

20:08

weird alien interference. it was a real

20:10

thing on the real sky. so that

20:12

eliminates my personal fave for an explanation

20:14

for anything weird that happens in science,

20:17

which is measurements her. Enemies:

20:19

We actually have to get some work done. And.

20:22

The next question of why spend so

20:24

much time talking about the statistics and

20:27

the shouting metaphor and all that I'd

20:29

swear there is a menace to my

20:31

method. The.

20:34

Next question is do we care. folks.

20:36

I need to take a quick

20:38

break and mention that the show

20:40

is sponsored by At Our Help.

20:42

Can you believe the year is already

20:45

halfway over at? I Swear sometimes

20:47

you blink and is just what

20:49

is time. I should do a ten

20:51

part see her his on the

20:53

nature of time in especially the

20:55

human perception of time. Because it is,

20:57

it's a little bit challenging to

20:59

understand and with that passage of

21:01

time. Com. Memory.

21:04

Regret, pride, anticipation, he all the human

21:06

emotions as surrounding time and so would

21:09

now that we're halfway through the years

21:11

mean we should pause to see where

21:13

we are in of where we're reaching

21:15

the goals and achieving the vision that

21:18

we wanted to achieve this year. And

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21:55

So there's a big cold spot

21:57

on the Cmb. In. one

21:59

particular direction. Do we care? Remember,

22:02

we can't say for certain

22:04

what splotches on the CMB

22:06

will appear where. We can

22:08

only predict the statistical information.

22:13

There is no theory or

22:15

observation that could tell us that when

22:17

we look through the direction of that

22:20

particular constellation that there will be a

22:22

cold spot of that size. We can't

22:24

make that kind of scientific prediction. We

22:26

don't have information. We don't have access

22:29

to that. It's beyond our horizon. Just

22:31

like you can't say, I am going

22:33

to listen in the northeast direction and

22:35

I expect in the next five minutes

22:37

to hear a very

22:40

high-pitched loud scream. You can't say that anymore

22:42

because you don't know who's over the horizon.

22:45

You can only predict the statistics.

22:48

So we have to play a little

22:50

dance here. We see a large cold spot. We

22:52

have to decide is

22:54

the cold spot too big and

22:56

too cold based on what

22:59

we reasonably expect the CMB to

23:01

look like. Let's say

23:03

you're listening to these shouts as

23:05

they roll across you from over

23:08

the horizon and randomly out of

23:10

nowhere you hear a shout that's

23:12

10 times louder and 10 times

23:14

higher pitch than anything else you've

23:17

ever heard. You have

23:19

to ask yourself, is this just a

23:21

weird statistical fluke? Like there's one crazy

23:23

loud human way over the horizon that

23:26

you didn't expect? Or

23:28

is this crazy loud shout telling you

23:31

something funky is happening that maybe you don't understand

23:33

human voices as well as you thought you did?

23:35

Because you built a statistical model. You know how

23:37

humans work. You know how loud they can be.

23:39

I know for this metaphor to work humans have

23:41

to be way louder than they actually are. Roll

23:43

with me. We got

23:46

this. Is the

23:48

cold spot too cold? Is this human

23:50

voice that you hear that's 10 times

23:52

louder? Is that too loud? Is that

23:54

impossible based on what you know about

23:56

human voices? Is

23:58

the cold spot too cold? based on the statistics

24:01

of what we know of how the

24:03

CMB works. There's been a lot

24:06

of back and forth on this, as

24:08

is usual with how messy science actually

24:10

is in practice. But

24:13

the general consensus is that, yes,

24:16

we should not reasonably expect the

24:18

cold spot to be

24:20

so cold and so big

24:22

just out of random chance. And

24:25

that based on our understanding of the physics

24:27

of the early universe, it's just way too

24:29

out of line. Yes, randomly big cold spot

24:32

should occasionally appear. But our chances of just

24:34

seeing one out of pure random chance is

24:36

less than one percent and might be even

24:38

lower, depending on who you ask. And

24:41

so so while we could say we

24:43

just got super unlucky and got a

24:45

cold spot, it's rare enough that it

24:47

demands some attention. So

24:50

it's not measurement error and it's

24:52

probably not random chance. What

24:54

is it? Well, it might be

24:57

something mundane, something strange, ish,

24:59

an interesting ish, but still fitting

25:01

within the framework of known physics.

25:04

And there are a lot of options

25:06

because there's a lot of stuff between

25:08

us and the CMB. The CMB was

25:10

generated over 13 billion years

25:13

ago. That light came from a distant

25:15

patch of the universe, so distant that

25:17

we can't even see that part of

25:19

the universe anymore. It had

25:21

to travel. It had to travel billions of

25:23

light years to get to us. And

25:26

so that light has been filtered.

25:29

It has been altered. And

25:31

yes, we're aware of this in our studies of the CMB.

25:34

All of the work that goes into

25:36

analyzing the CMB is in separating the

25:38

raw cosmological stuff from billions of years

25:40

ago, from all the interference effects in

25:42

between. That light

25:44

has been affected in tiny, tiny ways.

25:47

And one of the ways that

25:50

that light has been affected is that some

25:52

of the light passes through cosmic voids. Cut

25:54

the cosmic voids are big patches of nothing.

25:56

And it turns out these big patches of nothing

25:59

leave an. print on the CMB

26:02

that has nothing to do with the

26:04

CMB itself, but everything to do with

26:06

the fact that we have to look

26:08

through the voids to

26:10

get a view of the CMB. And now I'm

26:12

going to give you a gift. If

26:15

it's near your birthday or other notable

26:17

holiday, consider this my personal gift to

26:19

you. The gift is

26:24

the integrated Saxwolf effect,

26:27

named after Rainier Sax and Arthur Wolf. Cosmologists,

26:31

that's a mouthful, we just say

26:33

ISW, integrated Saxwolf effect. If

26:35

you want to bust that out to impress

26:38

friends and family, loved ones, by

26:40

all means give it a shot. It hasn't

26:42

worked on any of my friends and family and loved

26:44

ones, but you can

26:46

try it. Integrated Saxwolf

26:49

effect. This

26:51

is a mechanism where voids can

26:55

leave an imprint on the CMB and actually

26:57

lead to a colder spot. Here's

26:59

the idea. The idea

27:01

rests on two facts. One,

27:04

we live in an evolving universe.

27:07

The universe is constantly changing as

27:09

the light is making its way

27:13

from the CMB to us. It's

27:15

not just encountering a static universe

27:17

that's fixed. Stuff is

27:20

actually happening. Over the billions

27:22

of years that this light has made

27:24

its way to us, structures have grown,

27:26

galaxies have grown, clusters have grown,

27:28

the voids have emptied out, things

27:31

have happened. It

27:33

relies on the fact that dark energy

27:35

exists. We don't know what dark energy

27:37

is, but it is an observational reality.

27:40

The universe is accelerating in its expansion.

27:44

What this means is that

27:46

the voids themselves, which are

27:48

super empty, change

27:50

with time. They actually get bigger with

27:52

time. They get bigger

27:54

faster than expected because of the existence

27:57

of dark energy. What

27:59

happens? The voids are big

28:02

The minimum void size is like 20

28:04

million light years and they're bit. Most of them

28:06

are bigger than that. They're gigantic So

28:09

imagine you're a photon you're a bit of light

28:11

released from the CMB and you start traveling through

28:13

the universe and you're headed In the direction of

28:15

Earth you're going to reach Earth in like 13

28:17

billion years So you

28:19

you pack the sandwich and

28:22

you're trucking along you're going as you're

28:25

traveling Structure is evolving

28:27

that galaxies are emerging clusters are emerging

28:29

the voids are emptying out. So let's

28:32

say you encounter a void When

28:35

you first encounter a void you reach

28:37

like the entrance to that desert. The

28:40

void is kind of small It's

28:42

just those it's a young void Okay, so

28:44

you enter the void and

28:46

you actually gain a little bit of energy

28:48

as you enter the void It's like rolling

28:50

downhill You gain a little bit of energy

28:53

as you enter the void because there's less

28:55

stuff around you The

28:57

density is lower and

28:59

so you're a photon you respond to the

29:01

curvature of space time like that You actually

29:03

gain a little bit of energy as you

29:06

fall into the void and then

29:08

you travel across the void and it's super Empty and

29:10

nothing much happens to you Then

29:12

you reach the other end of the void Now

29:15

if the universe was static you

29:17

would then exit the void you

29:19

would come back up that hill You

29:21

would you would reach like a wall

29:23

of galaxies and then you would feel

29:26

that slight little density Difference and you

29:28

would lose your energy again and in

29:30

a static universe everything would be perfectly

29:32

the same You would gain

29:34

as much you would gain energy entering the void

29:37

Because you're rolling downhill into the void you're entering

29:39

a low density region And then you would come

29:41

back up into a high density region and you'd

29:43

give that energy back and everything would be great

29:47

But we don't live in a static universe we live

29:49

in a dynamic universe and especially we live in

29:51

a universe with dark energy That

29:53

is really dynamically affecting the voids in

29:55

a measurable way it means

29:59

That. In. The time it takes

30:01

for us a photon to cross.

30:05

This. Desert this void, The

30:07

void has gotten bigger. And

30:11

the walls on the other edge of the void

30:13

have piled up. All. The matter is

30:15

left the voice So in your journey

30:17

the time it takes you to make

30:19

this crossing of avoid. The.

30:21

Void is gotten bigger. There is more matter piled

30:24

up on the far side so you gain a

30:26

little bit of energy. Entering the void, you enter

30:28

a load and sea region. You go downhill little

30:30

bit. Then you cross the

30:32

void and then you hit the other wall.

30:34

but that wall is much bigger. The.

30:36

Void is much bigger. The. Walls

30:39

on the edge have been piled up from

30:41

all the material of all those millions, maybe

30:43

even hundreds of millions of years it took

30:45

for you to cross the void. The.

30:48

Void is gotten bigger and so you

30:50

lose energy on the other side and

30:52

you lose more energy. Than.

30:54

You game? When. A

30:56

photon crosses avoid in the void

30:58

is growing. especially if the void

31:01

is growing because of the influence

31:03

of dark energy. You.

31:05

Lose energy on the other side. This

31:08

thought process. Argues

31:10

that the cold spot is due to

31:13

a super void between us in the

31:15

Cmb. That. Turns

31:17

a regular spot that we wouldn't

31:19

otherwise care about into a giant

31:21

freezing monster. That. Gets

31:23

us all little bit worried so

31:25

that when we see the cold

31:27

spot in that direction, what we're

31:29

not looking at is something primordial.

31:31

Something generated in the Cmb itself.

31:33

That's why it looks so weird.

31:36

because it's not generated by the

31:38

statistical processes by the physics that

31:40

we understand of the early universe.

31:42

It's created by something else by

31:44

the fact that there is a

31:46

giant void between us. In.

31:48

That direction. That.

31:50

Is forcing all the light from

31:52

the Cmb coming from that direction

31:55

to appear much colder through this

31:57

effect known as the integrated. Wolf

32:00

Effect. Where. Voids grow,

32:02

They. Grow with time and in the time

32:04

it takes for a full time to cross.

32:07

Avoid. It's. Gotten bigger. it entered

32:09

it. Any thought it the edge

32:11

of the desert was fifty miles way. It

32:13

turns out it's one hundred miles away and

32:15

you have to. Oh

32:18

like yours a metaphor I'm making up on the

32:20

spot You enter a desert in see the desert

32:22

is the valley and there's a mountain range at

32:24

the beginning of the desert, in a mountain range

32:27

of the end of the deserts. So you come

32:29

into the desert and you come down the mountain

32:31

range. You gain energy by coming down the mountain

32:33

range than you skate across the desert and then

32:35

you go up the mountain range on the other

32:38

side and in a perfectly symmetric universe. On the

32:40

mountain ranges would be exactly the same size on

32:42

either side. So. You gain energy

32:44

going into the deserts and then you lose

32:46

energy coming out. But then everything's equal. But

32:49

in the dynamic universe. Ya.

32:53

Imagine it took you millions of years

32:55

across this desert that the landscape is

32:57

going to change. The mountains on the

33:00

other side might be getting bigger. The.

33:03

Desert my be growing larger and so

33:05

you fall into the desert you come

33:07

down off of one rains. You.

33:10

Entered the desert you have a little bit of

33:12

an extra energy but by the time you finish

33:14

crossing at the mountain range on the other side

33:16

is now even bigger. And.

33:18

The have to climb up that new and up

33:20

overall. Losing. Energy that is

33:22

the integrated sexual. And

33:24

that's a possible explanation for the cold spot.

33:27

The thing is, this has to be a

33:29

supervillain. The. Thing would have to be

33:31

gigantic, like a billion light years on the side

33:33

kind of thing. Maggie at one of it's not

33:35

the largest single object in the universe. And.

33:37

Now you can rightly as like okay.

33:40

This cold spot on the sea and

33:42

be so statistically improbable that it can

33:44

be generated in the early universe. Of

33:46

what about super voids that are a

33:48

billion light years across? Can they be

33:50

generated in our universe? Or does that

33:52

stretch our understanding of physics? Is it

33:54

all Turtles all the way down. In.

33:57

the answer there seems to be this is harder to

33:59

get out because the physics of void

34:01

formation is more complicated than the

34:03

physics of the CMB. So

34:06

the statistics here are Lucier and

34:08

Gucier. The general consensus

34:10

at the current state, at

34:13

the time of recording, after having read like

34:15

all the papers on this, is

34:17

that the existence of such a supergiant

34:19

void is maybe kind of sort of

34:21

a problem, but definitely less

34:23

of a problem than the existence of the

34:26

cold spot itself. So that's

34:28

kind of an advancement. And we'll take it.

34:30

It's not much, but we'll take it. It

34:33

appears that the existence of such a giant

34:36

void, super void, in this direction

34:40

is not threatening enough to be worried about.

34:42

It's big and it's kind of weird, but

34:44

not big enough and weird enough to say

34:46

there's no way our universe could generate a

34:48

void of that size. But

34:50

is that it? Okay, is that it? Is

34:53

a super void responsible for the cold spot?

34:56

Well, if you snuck a glance at

34:58

the remaining runtime of this episode, then

35:00

you know that there's more than enough

35:03

time for a Patreon ad. That's patreon.com/PM

35:05

Sutter. Thank you so

35:07

much for all of your contributions.

35:09

I really do. I sincerely appreciate

35:11

every single contribution to keep

35:14

this show going. That's

35:16

patreon.com/PM Sutter. Anyway,

35:19

you know there's more to the story. Here's

35:22

the thing. We can't seem to

35:24

agree on whether there's actually a void in the direction

35:27

of the cold spot. I know I

35:29

literally just told you about the super void sitting

35:31

between us and the CMB in that direction, leading

35:33

to the wonderful integrated sax wolf effect in the

35:35

appearance of a cold spot that doesn't really belong

35:38

there. But that's a hypothesis and

35:40

we'd like to test it like any

35:42

good hypothesis by rummaging around the galaxies

35:44

in that direction to see if we

35:46

can actually find a super void there.

35:49

And this is actually somewhat challenging because the

35:51

super void is huge. So we need to

35:53

scan a massive volume in order to capture

35:56

it. But we're

35:58

only focused in one particular direction. so

36:00

we're limited in scope. This is a

36:02

challenging survey thing where you have to

36:04

look in one particular direction but get

36:06

enough volume so you can map out

36:08

this giant void. And the

36:11

giant void isn't just big left

36:13

to right, it's also big in

36:16

depth. And we

36:18

have lots of surveys of lots of galaxies out

36:20

there in the universe. And some

36:22

of them do cover the sky in

36:24

this direction, but they all have limitations.

36:26

They can only map so far back,

36:28

they can only capture galaxies of a

36:30

minimum brightness, they only map certain types

36:32

of galaxies. So all the

36:35

surveys in this direction are incomplete. We

36:37

don't have a full accounting of all

36:39

the galaxies in the direction of the

36:41

cold spot. And we

36:44

have great tools for reliably mapping

36:46

out voids. You can think of

36:48

certain peace utter for that contribution

36:50

to science. But

36:52

super voids are much trickier. Not

36:55

only are they big, they're not very deep. They're

36:58

very shallow and broad. And that makes

37:00

it difficult to identify. If you just

37:02

have a map of galaxies, it's actually

37:05

challenging for super voids to identify the

37:08

presence of a void that big.

37:11

Which means that over

37:13

the years you have competing claims and counter claims.

37:16

Some papers saying there's definitely 100% a

37:19

giant void there. Other papers saying nah, there's no

37:21

void there, you big dummy. And it just goes

37:23

back and forth. And if

37:25

that wasn't enough, just to throw yet

37:27

another wrinkle into this, even the biggest,

37:29

deepest, most superlative super void that is

37:31

anyone has ever claimed to find in

37:33

the maps of galaxies over in that

37:35

direction. Even that

37:38

isn't big enough, deep enough, or super enough

37:40

to give that big of an integrated sex

37:42

wolf effect on its own. Which

37:44

means we need a lucky coincidence. You

37:46

need a super giant void just happening

37:48

to sit along a line of sight

37:50

to an already colder than average spot,

37:54

combining their powers to form the cold spot.

37:57

But the entire point of this exercise was to

37:59

to remove the need for weird coincidences.

38:02

So maybe, maybe it's something

38:04

crazy. Maybe it's

38:06

not random chance. Maybe it's not a super

38:08

void. Maybe it's telling us something about the

38:10

universe. There's this crazy idea out there that

38:13

it's what we see as the cold spy

38:15

is the intersection point with another universe. That

38:18

this is evidence for the multiverse that

38:20

a long time ago, our little bubble

38:23

universe was bumped up against another little

38:25

bubble universe. Now we're widely separated, but

38:27

for a while we were like little

38:29

conjoined twins and

38:31

that left an imprint in the CMB in the

38:33

form of the cold spot. I'm

38:35

not going to spend a lot of time on that

38:37

idea. In fact, like zero time on that idea because

38:39

it doesn't really work.

38:41

It doesn't really explain the properties of the

38:43

cold spot. It's an interesting idea. It's an

38:46

awesome idea. But if it's

38:48

interesting, say it with me kids, if it's interesting, it's

38:50

probably wrong. And it doesn't

38:52

really explain the properties of the cold

38:55

spot, but we can't toss out in

38:57

general crazy ideas because all the non

38:59

crazy ideas aren't exactly working either. In

39:01

summary, we don't know

39:03

what's causing the cold spot. We don't know if it's

39:05

a big deal. And we don't even know

39:07

if we should care about it. That

39:10

is why we are screaming in my

39:12

metaphor because we don't understand the cold spot.

39:16

The moral of the story goes back to the

39:18

way I introduced the episode, which

39:20

is that science is messy. And

39:22

we often don't have all the answers and

39:25

that we can nail the big stuff while still

39:27

worrying about the small details. Does

39:29

the cold spot invalidate the Big Bang Theory?

39:31

No, we understand the CMB,

39:33

the existence of the CMB itself

39:35

as a prediction of the Big

39:37

Bang Theory. We understand the statistical

39:40

fluctuations, the hot and cold splotches

39:42

to obscene level

39:44

of precision. You can't

39:46

use the cold spot to throw out the Big Bang

39:48

Theory. Is the cold

39:50

spot worth looking into? Almost certainly. There's

39:53

a chance that there's nothing interesting there.

39:56

There's a chance there's something really fun

39:58

going on. on there that

40:00

we don't fully understand. Will we ever conclusively

40:03

figure out what it is? Possibly no. Generations

40:06

from now, we may not have a

40:08

satisfactory answer to the cold spot. This

40:10

is the way science is. It's never perfect.

40:13

There's always some little thorn in some theory

40:15

side. Sometimes those thorns blossom

40:17

to reveal new kinds of physics, in

40:19

this case, a multiverse. Sometimes

40:22

those thorns just wither away as scientists slowly

40:25

chip away at it. Maybe we get better

40:27

at mapping the voids in that direction. Maybe

40:30

we discover some more nuances to

40:32

the integrated sex wolf effect. Maybe

40:34

after enough decades of work, the

40:37

cold spot problem just fades away.

40:39

And maybe it just sits there, never

40:42

fully resolved, never fully

40:44

answered, but never rising to the

40:47

level of needing more attention. No

40:50

matter what, it's OK by me. Why? Because

40:52

nothing is perfect in this universe, not

40:55

even our understanding of it. Thank

40:57

you to Eric S, Martin N,

40:59

SA, HM, and Michael C for

41:02

the questions that led to today's episode. And

41:04

thank you, of course, to all

41:06

of my top Patreon contributors. I

41:08

really cannot thank you enough. All

41:11

of your contributors, contributions are amazing. That's

41:13

patreon.com/PM Sutter. But let me give a

41:15

shout out to my top contributors this

41:17

month. We've got Justin G,

41:20

Chris L, Alberto M, Corey D,

41:22

Stargazer Robert B, Tom G, Nyla,

41:24

Bike Santa, Sam R, John S,

41:26

Joshua Scott M, Rob H, Scott

41:29

M, Lewis M, John W, Alexis

41:31

Gilbert M, Rob W, Demethius J,

41:34

Jules R, Mike G, Jim L,

41:36

Scott J, David S, Scott R,

41:39

BBJJ108, Heather Mike S,

41:42

Michelle R, Pete H, Steve S, What

41:45

What Bird, Lisa R, and Koozie. That's

41:49

patreon.com/PM Sutter. Keep

41:51

those questions coming. That's askaspacepanachemail.com. Go to

41:53

the website. There's a form you can

41:56

fill out there. askaspaceman.com.

41:58

Check out the archives. show

42:01

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42:03

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42:07

is how the show grows I really

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