0:00

We've heard of all

0:02

the usual stuff. Electrons,

0:04

protons, quarks, neutrinos, and if you're

0:06

a fan of this show then

0:08

you've also heard of some of

0:10

the other rarer particles, you know?

0:13

the wimps, the tachyons, the

0:15

monopoles, the whole family of

0:17

supersymmetric partners, that the the

0:19

electrons, the squarks, and yes. even

0:22

the we know bosons. But

0:25

that's not enough to satisfy

0:27

your curiosity, is it? Like

0:30

a collector of rare and priceless artifacts

0:32

you feel compelled to go just a

0:34

little bit deeper, a little bit. weirder.

0:38

I understand that desire and I am

0:40

here to help. So come over

0:42

here, I've got something to show. you. Five

0:45

of the weirdest, strangest, rarest,

0:47

most hypothetical particles in

0:49

the universe. These particles are

0:51

so rare, we're not

0:53

even sure they even exist.

0:55

And I think you're gonna like them. I

0:58

have to give my usual disclaimer

1:00

whenever I give a list of

1:02

things. These are presented in no

1:04

particular order, so feel free to

1:06

rank them by whatever criteria you

1:08

prefer. you know, interestingness, cheerfulness, propensity

1:10

for potential cheese making in and

1:12

so on. but let's get

1:15

started. Number one is

1:17

the dark photon. Everybody loves

1:19

the photon. know, it gets

1:21

along with so many particles,

1:23

it has infinite range, it

1:25

makes flashlights work, but it

1:27

may not be the only

1:29

kind of photon out there. And

1:31

that's why we think there might be

1:33

the dark photon, which is like the

1:35

regular photon, but dark. So

1:38

the motivation here is what the

1:40

heck is going on with dark

1:42

matter and dark energy. that

1:44

know, learned over the past

1:46

few decades. that visible matter, normal

1:48

matter, something we call baryonic

1:50

matter. know, the stuff of

1:52

protons, neutrons, and electrons with

1:54

all of our complicated forces,

1:56

you know, make. up less

1:58

than 5%. of the total

2:01

energy contents of the universe. We

2:03

know a huge component, dark matter,

2:05

is about 25 % of the

2:07

universe, and this is some invisible

2:10

form of matter that we have

2:12

yet to identify that makes up

2:14

the mass of almost every single

2:16

galaxy and anything larger. And

2:18

then there's Dark Energy, which is

2:20

the name we give to the

2:22

accelerated expansion of the universe, which

2:24

makes up about 70 % of the

2:26

stuff in the universe. and

2:30

I do need to take

2:32

a quick break to mention that

2:34

this show is brought to

2:36

you by BetterHelp and it's 2025,

2:38

we're here and there's a

2:40

whole year waiting for us. One

2:42

way to say it is

2:44

there are 365 blank pages waiting

2:47

to be filled in. That

2:49

kind of void can be scary,

2:51

but let me tell you

2:53

as someone who has researched the

2:55

void in the real universe,

2:57

cosmic voids, that the voids are

2:59

full of potential. This is where

3:01

you can make changes happen. This

3:03

is where things become possible because

3:05

once something happens, once something is

3:07

filled, you remove all possibilities. this

3:09

is, I want you to look

3:11

forward to the year and celebrate

3:13

the possibilities that might come down

3:15

the road and what you can

3:18

create. And I've been able to

3:20

develop this kind of perspective through

3:22

therapy. And I'd like you to

3:24

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3:51

Okay, so we've got

3:53

these two giant components to

3:55

the universe and we have

3:57

to ask. The physics. that

4:00

we know about, is which

4:02

is the baryonic physics, the

4:04

light loving physics, is absurdly

4:06

complicated. We have a particle a

4:09

we have multiple forces, we have

4:11

all sorts of interesting interactions, we

4:13

have chemistry, we have the

4:15

whole deal. chemistry, is the

4:17

rest of the rest matter and

4:19

dark energy? Are they big

4:21

and simple and dumb? and simple

4:24

they big big complex

4:26

and rich and interesting?

4:28

Are there additional forces operating between

4:30

and matter and dark energy?

4:32

Are there different species of

4:34

dark matter particles that interact

4:36

with each other? Are there

4:38

new forces of nature that

4:40

only operate in what we

4:42

call the call sector of the

4:44

universe, the the of dark

4:46

matter and dark energy? and What's

4:49

adding a little bit

4:51

of gasoline to this

4:53

speculation? speculation? is that that and

4:55

matter and dark energy are

4:57

weirdly There's a

4:59

lot of dark energy and lot of dark energy,

5:01

and there's a lot of dark matter,

5:03

and there's more dark energy than there

5:06

is dark matter, is dark matter, If

5:08

we look at the span of

5:10

history... throughout evolution, billions of years

5:12

ago, there was there was essentially

5:14

energy. energy and of years from

5:16

now, from the universe will be

5:19

almost completely dark energy. You

5:21

get more dark energy as

5:23

the universe expands. as the universe expands

5:26

live in this extremely

5:28

coincidental time. time where

5:30

dark matter and dark energy just

5:32

happen to be roughly within the

5:35

same order of magnitude ballpark of

5:37

each other. of each other. Or there's

5:39

something fishy going on. There are

5:41

additional forces between dark matter

5:43

and dark energy dark keep them

5:45

on track with each other, that

5:48

make them interact so that

5:50

they always have roughly the same

5:52

amount of energy density in

5:54

the universe. universe. don't know. know,

5:56

but we we are developing

5:58

theoretical models. to explore these these

6:01

options and these theoretical models include

6:03

new forces of nature. ways that there

6:05

are new ways that dark matter

6:07

can interact with itself. There are

6:09

ways that dark matter and dark

6:11

energy can talk to each other

6:13

and so on. each other these forces

6:15

need force carriers, and we call

6:17

those force carriers carriers, photons. photons. Now

6:19

anytime you create a new particle,

6:21

you around around bored one day and

6:23

you're like, you know what, I

6:26

think there should be a new

6:28

particle in the universe. You

6:30

can't just come up with

6:32

a cool name, come up that is

6:34

priority number one. but

6:36

after you come up with a cool name, you need

6:38

to list a cool name you need need to

6:40

list its property you need to list its

6:42

mass it's type, it's charge, how

6:44

does it how does it interact

6:47

with the other particles that

6:49

we know of in the

6:51

universe? And so with the so with

6:53

the dark photon, this isn't

6:55

just one kind of particle, it's

6:57

actually a family of particles

6:59

that have the general characteristic more

7:01

they talk more to the dark

7:03

sector of the universe than

7:05

they do to the light side

7:08

of the universe. But within

7:10

that family, There are a

7:12

broad range of possible masses

7:14

and a broad range of

7:16

possible interactions with normal matter.

7:18

We're not gonna cut it

7:20

off completely. say, okay, maybe the dark

7:22

maybe the dark photon exists and

7:24

it almost always talks to dark

7:26

matter and dark energy. energy. But maybe sometimes

7:28

a a dark photon interacts with

7:30

like a regular photon, or

7:32

you and me, just just rarely. rarely.

7:34

would have seen it by

7:36

now. seen it by maybe it's

7:38

not impossible. And so

7:40

go out we come up with these up

7:42

with these families of particles, and

7:45

then we try experiments to go

7:47

looking for them. when it when

7:49

it comes to the dark if it doesn't

7:51

If it doesn't have mass, if the

7:53

actual dark photon actually exists and

7:55

it doesn't have mass, then we will

7:57

never be able to see it or

7:59

directly. detected. will always be hidden

8:01

in the dark sector of the universe

8:03

and will only ever get circumstantial

8:05

evidence for its existence. if

8:08

it does. have

8:10

mass if it has just a little bit

8:12

of mass. then

8:14

it can interact or

8:16

potentially interact with normal

8:19

matter. It opens up

8:21

some channels. because if it

8:23

does have mass, then the

8:25

dark photon can spontaneously decay

8:27

into other particles. It

8:29

maybe it spontaneously decays dark

8:31

matter, but also maybe it

8:33

spontaneously decays into a positron

8:36

and electron pairs, or it

8:38

converts into a normal photon.

8:40

Yeah, we don't know. We're

8:42

just guessing here. We're just

8:44

creating opportunities for the dark

8:47

photon to be detectable in

8:49

our experiments. And

8:51

we have a wide variety of

8:53

potential experiments where we can go

8:55

hunting for dark photons because once

8:57

you introduce a new particle

8:59

into the universe that has mass

9:01

that can spontaneously decay, that can

9:04

interact with other stuff. You

9:06

start messing with the physics of

9:08

the universe, so So talking particle

9:10

collider experiments. You're gonna get different

9:12

results if dark photons are at

9:14

play. You're gonna get different

9:16

results with Big Bang Nucleosynthesis with

9:18

the production of the first elements

9:20

in the first few minutes of

9:22

the Big Bang because there's an

9:24

extra player playing around, messing up

9:26

with the physics. You're gonna mess

9:28

with cosmic rays. They can also

9:30

mess up the interiors of neutron

9:32

stars. They can change how

9:35

quickly or slowly they lose

9:37

their heat. The most fun

9:39

way, in my opinion, of

9:41

detecting dark photons is through

9:44

something called black hole super

9:46

radiance, which deserves its own

9:48

episode. because there's another cool concept

9:50

behind black hole super radiance, which

9:52

is something called black hole bombs, which

9:54

sounds really fun, but is not

9:56

today's subject. Don't let me get sidetracked,

9:58

but feed. please feel free to

10:01

ask. But the general gist behind

10:03

Super Radiance is that is photons can

10:05

get trapped in orbit around spinning black

10:07

holes and then they get their

10:09

energy boosted and then they just like

10:11

boosted and then they just like blow up.

10:13

If the if photon exists,

10:15

it's nearly impossible to find.

10:17

We've searched in our

10:20

laboratories, in our experiments, in

10:22

astronomical observations, and we've

10:24

found. and we've found nothing. we see

10:26

no no evidence for the existence

10:28

of the of the dark And so

10:30

we've so intense limits on the

10:32

properties it's allowed to have.

10:34

So so we've drew out out this

10:36

broad family of particles with potential

10:38

masses, potential interaction strengths potential interaction

10:40

channels, energy levels where they tend

10:43

to show up and we

10:45

can just start checking it off

10:47

the list. Like, okay, can't

10:49

be that. that can't be that mass, can't

10:51

have that interaction channel, can't have

10:54

that interaction strength, they are

10:56

just moving right down the list

10:58

moving now the possibility of the

11:00

now the existing is very, very

11:02

slim. existing is very very slim If

11:04

it does exist, its ability to

11:06

mix into regular matter must be

11:08

very limited as something like. as

11:10

something like a trillion a trillion even

11:13

lower lower. On On the other hand,

11:15

it may exist only in the dark

11:17

sector and will never be able to

11:19

directly detect it. And we can only

11:21

build circumstantial evidence for it. which

11:23

is an unsavory state of affairs,

11:25

but that's the way it is

11:27

with state rare particles. the way it is

11:29

with these particle today. Our number

11:31

two the today is the

11:33

kervaton. That's right, this is

11:36

not a a Transformers bad guy. a

11:38

It is a real hypothetical particle. I

11:40

don't don't know if that's an

11:42

oxymoron, but here we are. are. So

11:44

let's go back in time. in time

11:46

a bit to explore the

11:48

Kerbitan, because we need to

11:50

talk about inflation. inflation. You know, Your

11:52

inflation is this hypothetical event

11:54

that occurred in the extremely

11:57

early universe where the cosmos

11:59

rapidly in a in a blink

12:01

of an eye it expanded by a

12:03

factor of 10 to the 60 the

12:05

60 in less less than to the minus

12:07

35 35 You know something crazy crazy.

12:10

and inflation... was powered

12:13

by an powered by an

12:15

entity. There was something behind

12:17

inflation. We believe it

12:19

was driven by a by a quantum

12:21

field. This quantum field

12:23

we call the the inflatan, because

12:26

that That sounds convenient. The

12:29

Inflatan drove drove inflation. Now

12:31

what Now what inflation did, it did two

12:33

things. One, it made the universe really, really big.

12:36

and then big. the end

12:38

the end of and this is kind of

12:40

a big deal. kind of a big deal, it

12:42

laid down the seeds of structure

12:44

formation. So what we see

12:46

as galaxies and clusters today

12:48

got their start at the

12:50

end of inflation in that

12:52

very, very early early epoch. Now

12:54

we have have no idea what

12:56

powered inflation, we have no idea

12:59

what the what is. Again, remember,

13:01

remember one is the cool name

13:03

cool then priority number two is

13:05

everything else. everything We don't know what

13:07

the know was. We don't know what

13:09

properties it had. We don't know why

13:11

it kicked into high gear. it In the

13:13

early universe, we don't know why it

13:15

went away and stopped when it did.

13:17

away in fact, the most annoying thing

13:19

about inflation. annoying thing is that it's

13:21

really tricky to get right. get right.

13:23

Because if inflation lasts too long,

13:25

then you end up with

13:27

a cold, frozen frozen wasteland

13:30

of a universe. ends If it

13:32

ends too quickly, then you're

13:34

not able to solve some

13:36

of the problems that inflation

13:38

was designed to solve. solve. And

13:40

so you need to tune inflation

13:42

a little bit to get it to

13:44

behave in the way we expect

13:46

it to behave. behave. And the real

13:49

problem is is that are many natural

13:51

or simple models of inflation

13:53

that do the job. the

13:55

way that behave the way inflation is supposed to

13:57

behave, where it turns on at the right

13:59

time. expands the the universe in

14:01

the right way and then turns off

14:03

at the right time. There are ways to

14:05

build relatively simple models that do not

14:08

require a lot of fine of fine inflation

14:10

just does its thing. just does its thing, we

14:12

have a lot of trouble getting those

14:14

models. that allow allow inflation to

14:16

do its thing without really needing

14:18

to go in and fine and

14:20

sharpen get get these precise values it's just

14:22

it's just like, you if you

14:24

have an with with these generic properties,

14:26

the the universe inflates and you're

14:28

done. you're done. We We have a hard time. reconciling

14:31

those those models? what with

14:34

what inflation needs to do

14:36

at the very end, which the seeds

14:38

of lay down the seeds of

14:40

structure. frustrating is frustrating because we would

14:42

like everything to just line up

14:44

and be nice nice you have a

14:46

simple generic model. model that

14:48

there is is some quantum field. and

14:51

through its very nature of existence,

14:53

you know, the properties it's supposed

14:55

to have. to just drives

14:57

inflation, expands the universe, and then lays

14:59

down the seeds at the end.

15:02

It seems like we can't have both.

15:04

we can't have both. So the inflation

15:06

wasn't alone. Maybe the the wasn't the

15:08

only thing out there in the

15:10

early universe. Maybe there was something

15:12

else, the there was something else, is a

15:14

companion to the to the And

15:16

the idea here is that

15:18

here is that during while the Inflaton

15:20

is powering the accelerated expansion

15:22

of the universe, of the

15:24

universe, the kervaton out. just

15:27

hanging out. grab an a soda.

15:29

Then at the at the end, once

15:31

the goes goes away and

15:33

inflation is over, the Curviton

15:35

takes. over the cosmic the

15:37

cosmic scene? space-time a a little,

15:39

lays down the seeds of future

15:41

structures, and and then goes away. away. The

15:43

The advantage of this is that that

15:45

now you have a lot

15:48

more freedom for inflation to be

15:50

natural or simple where

15:52

inflation just naturally arises out of

15:54

the universe the of the fundamental

15:56

properties of quantum fields that you

15:58

that you don't need worry about

16:00

anything else? and you don't you don't

16:02

need the to to do all

16:04

the work of inflating the creating the

16:07

creating the seeds of structure, because

16:09

now you have something else teeing

16:11

over that second job. is that The

16:13

disadvantage is that idea that we have no

16:15

idea how inflation works, and we do

16:17

not even know the identity. to give

16:20

the it's a little cheeky to to introduce

16:22

yet another unknown entity the the cosmos, but

16:24

what are you gonna do? to do?

16:26

Honestly, the Curviton probably doesn't

16:28

exist, but these models are

16:30

still helpful because we are

16:32

trying our best to poke

16:34

and prod at the extremely

16:37

early early It's not like

16:39

we have direct observational evidence of this epoch,

16:41

so we don't have a lot to

16:43

go on, so we just have our models,

16:45

we just have our creative ideas. we just

16:47

have our we explore

16:49

in any viable

16:52

direction, including... including introducing

16:55

new... entities into the early

16:57

universe like the the Kerbiton. Maybe

16:59

we might we might strike upon some...

17:01

Something interesting, maybe we might

17:03

find an interesting combination that

17:05

is testable that is testable lot more

17:07

about how inflation works. inflation works.

17:10

if the if the did exist,

17:12

it doesn't exist it doesn't exist anymore.

17:15

as soon as it did its job

17:17

by design, it has to go away

17:19

and not leave an imprint on the on

17:21

the later because... If it

17:23

did, you you have the Curviton

17:25

lasting minutes or hours or years

17:27

into the Bang, then you're then you're

17:29

gonna mess up Big Bang Nucleosynthesis,

17:31

you're gonna mess up the Cosmic

17:33

Microwave mess up the we don't see any

17:35

evidence of Big Bang Nucleosynthesis of

17:37

Cosmic Microwave Background or anything else

17:39

being messed up and so or anything

17:41

else had to go away, but it still

17:44

had an impact, so that counts. But it still

17:46

had an impact, so that counts. I

17:48

need to take another very brief

17:50

break. break. and mention that this

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plan. our

19:20

number three weird particle

19:22

today. is the

19:24

glue ball. If you

19:26

crack open a proton, you'll find three

19:28

quarks. bound together with

19:30

the strong nuclear force. The

19:33

carrier of the strong nuclear force

19:35

is a particle known as the

19:37

gluon of which there are nine

19:39

varieties. Just for reference,

19:41

the electromagnetic force has only

19:43

one carrier. the photon. And

19:45

the weak nuclear force has three

19:47

carriers. In the

19:49

delightful parlance of nuclear particle

19:52

physics, the quarks have a

19:54

property known as color charge,

19:56

which basically means that they

19:58

can feel the strong nuclear

20:00

force. Particles without color can't feel

20:03

that force, just like electrically

20:05

neutral particles can't feel the

20:07

electromagnetic force. Here's the

20:09

fun thing about the thing those

20:11

carriers of the strong nuclear

20:13

force. strong they have They have

20:15

color charge too. right, you right, you heard

20:17

it here. The carriers of the

20:19

strong nuclear force can feel the

20:22

strong nuclear force. strong nuclear And

20:24

so our best models of the

20:26

proton tell us that they are

20:28

us that hot of of strong force

20:30

interactions you you have quarks exchanging gluons to

20:32

glue themselves together, but then the

20:34

then the themselves feel that same strong

20:36

force and so they interact with

20:38

each other and so on. each

20:40

other and so on. not the only

20:42

the only of strong nuclear -forced

20:44

interactions. The protons are

20:46

made of three quarks with their their

20:49

and so are the neutrons. There's

20:51

this whole other family of

20:53

particles the the which which

20:56

contain just two quarks plus

20:58

all their And in general, the

21:00

general, the strong nuclear force

21:02

is really, really good

21:04

at making large composite particles,

21:06

big with big particles with

21:08

big complicated interactions. got all these So

21:11

we've got all these combinations of

21:13

quarks and with the strong together with the

21:15

strong nuclear force and we give different

21:17

names to these different combinations. but

21:20

if glueons feel the strong

21:22

nuclear force force anyway, why don't

21:24

we just skip the quark part? the quirk

21:26

I mean, why make it so complicated? Just

21:29

keep it simple. And that's how

21:31

we came up with the that's how

21:33

we which is a hefty

21:35

particle, massive composite particle,

21:37

made of nothing more than

21:39

a collection of of nothing more

21:41

than a well, glued together,

21:43

I guess. well, glued We're

21:45

talking guess. We're particle. of a made

21:48

of nothing but... force

21:50

carriers, which which is of of weird

21:52

and also kind of cool. What

21:54

makes the the so elusive is that

21:56

it's incredibly ephemeral.

21:58

It lives less than and then a microsecond,

22:00

which isn't that surprising, you know, know,

22:03

every single combination of quarks and

22:05

and the proton is also unstable

22:07

in isolation. Yes, even the neutron,

22:09

if you take a neutron out

22:11

of a nucleus. take a neutron out of

22:13

a let it free float, it will decay

22:15

in about 15 minutes. decay in But

22:18

the minutes. are expected to

22:20

have exceptionally short lifetimes.

22:22

short lifetimes. would have seen them

22:24

floating around in our around in now and we

22:26

don't so we know they can't live long. live

22:28

long. but that one of the

22:30

challenges with the with the glue that

22:33

the predicted mass of the glue

22:35

ball is in the is in of just just

22:37

about every other composite particle.

22:39

made in particle colliders. So

22:42

So we turn on our particle

22:44

colliders, we make these showers of

22:46

particles. We see all sorts of

22:48

protons and neutrons. We see all

22:50

sorts of we We see more exotic

22:52

ones. we see more exotic ones,

22:54

and the glue ball... is probably sitting

22:56

in there with them. we

22:59

have a but we have a hard

23:01

time telling it apart from the

23:03

other ones. you you just see

23:05

a particle, if if you giant some

23:07

giant experiment and you crack these

23:09

atoms open and you let their

23:11

guts spill out and they start

23:13

transforming into all these showers of

23:15

particles. usually the

23:17

first the first thing you get to the

23:20

the easiest thing to quantify in a

23:22

new experiment is a is a mass. mass.

23:24

You You say, okay, you look at all at all the

23:26

proxy, you say, you say, we've got some particles

23:28

over here with this mass, we've got some

23:31

particles over here with that mass. got some Usually

23:33

you don't get to see the

23:35

other properties. You need more detailed experiments

23:37

to get those other properties. more detailed

23:40

this case... to get those other

23:42

When we run these

23:45

experiments, we see run

23:47

these experiments, We see

23:49

new particles appearing. particles that

23:51

have the right the right mass to

23:53

be a a glue ball. But the

23:55

problem is, these candidate particles, these new

23:57

particles show show up that we've

23:59

never seen before, also masses

24:01

that are compatible with

24:03

with like just new kinds

24:06

of mazons or new kinds or new kinds

24:08

of - other other

24:10

combinations of quarks and

24:12

It's hard to tell hard to tell

24:14

when we see that interesting new particle

24:16

and it shows up on our plot. our If

24:18

it's a glue a glue which

24:21

would be would exciting. exciting, or just

24:23

another which is is kind of

24:25

exciting but not as exciting

24:27

as a a glue ball. So

24:29

nowadays there's a whole experiment

24:31

called called glue is designed to

24:33

find balls not just based on

24:35

their their mass we have a

24:37

bunch of candidates that might

24:39

be glueballs. might be glue balls but

24:41

to verify that what we're

24:43

seeing is actually a glue a glue

24:45

on what it decays into. into

24:48

because a ball when it finally

24:50

disappears and decays into a shower

24:52

of other things. things The the

24:54

products that it creates be

24:57

be different what what a mason

24:59

or baryon Berion creates. only but

25:01

it's only through those Just

25:03

tiny, tiny. one in a million in

25:05

a million differences will be able to

25:07

be able to definitively say that

25:09

a glue ball exists. that's And

25:12

that's hard, we haven't done it

25:14

yet. yet, but reason we are so

25:16

interested in glue in glue that is that

25:18

are the last major undetected prediction

25:20

of the standard model. The The

25:22

standard model of particle physics emerged in

25:24

the emerged in the and

25:26

made all sorts of

25:29

predictions about the nature of

25:31

fundamental particles, the Large

25:33

Hadron Collider was designed to.

25:35

designed to finally determine the last

25:37

predictions of the standard

25:39

model and then also

25:41

hopefully move beyond it. One

25:44

of One of those last major untested

25:46

predictions was the Higgs boson, which we

25:48

found. And then the other one was

25:50

the existence of the of the glue which we

25:52

have yet to find. We have candidates.

25:55

We see some interesting signals, but

25:57

we can't yet determine if

25:59

those were... are glue balls, but but the hunt

26:01

is on. Our number four number four

26:03

particle today is known by the

26:06

cryptic name of which like

26:08

a secret which sounds like a

26:10

secret military base, but yet it's just cool again

26:12

a cool name for a particle. We've

26:14

been trying to move past the standard model

26:16

of particle physics. of pretty much as soon

26:18

as we invented it. as soon as

26:20

model is hugely successful, perhaps

26:22

the most successful scientific. perhaps

26:25

the most successful scientific theory

26:27

of all time. all time. Some Some

26:29

predictions by by

26:31

the model are validated to within one

26:34

part in a quadrillion, which

26:36

is indeed pretty impressive. But

26:38

despite that success, or that success

26:40

or because of that success, we've

26:42

been trying to find any crack in

26:44

any flaw in the so that we can that

26:46

we can move We know know the

26:48

standard model is incomplete. There's

26:50

a whole list of things do do not

26:52

understand about particle physics. Please feel free

26:55

to ask about to are the major

26:57

outstanding questions in the standard model. in the

26:59

would be a very, very fun episode. would

27:01

be a very, so we've been trying,

27:03

we've been trying to find a

27:05

flaw trying to find a flaw because we use

27:07

that flaw to learn something

27:09

new about the universe and move

27:11

past it. it. One One of

27:14

the difficulties of this is that

27:16

experiments testing the standard model

27:18

are huge, extremely carefully calibrated, and

27:20

take years of data to

27:22

lead to a result. So So

27:24

is a little slow. slow. But in 2015,

27:26

physicists got a signal that something

27:28

might be wrong with the

27:31

standard model. It was It was at Atomki,

27:33

Hungarian Institute for Nuclear Research. Research.

27:36

and the team had assembled an

27:38

apparatus to search for dark

27:40

photons of all things. things. The

27:42

setup involved firing protons at at lithium-7,

27:44

which then transformed into a

27:46

beryllium -8, then that and then that

27:48

beryllium -8 promptly decayed and produced

27:50

pairs of electrons and positrons. These

27:52

pairs go off -flying at various

27:54

angles, and then you can

27:56

use nuclear physics calculations to predict

27:59

the spread. of those angles.

28:01

And then if you're getting extra

28:03

of these particles compared to where

28:05

you expect them to be at

28:07

various positions, it might be

28:09

because dark photons are getting involved

28:11

that then decay into normal matter

28:13

as they might or might not

28:15

do and just generally mess up

28:17

your experiment. And what do you

28:19

know? The Hungarian team found extra

28:21

electrons and positrons more than they

28:24

expected from theoretical calculations from the

28:26

standard model. To recreate the signal,

28:28

there had to be a new

28:30

particle involved in the process with

28:32

a mass of 17 mega volts,

28:34

which to give you a sense

28:36

of scale is about 34 times. the

28:38

mass of the electron. And

28:40

so, this mysterious new particle got a

28:42

name, X17. In

28:45

the following years, the Hungarian team

28:47

has built up an impressive list

28:49

of accomplishments that all point to

28:51

the reality of this new particle.

28:54

They've calculated the statistical significance of

28:56

the signal and it's up

28:58

above six sigma, where five sigma

29:00

is considered the gold standard

29:02

in particle physics. And here they

29:05

are at even one sigma

29:07

higher. like that the probability

29:09

of this result being due to

29:11

random chances is so incredibly

29:13

small. They've changed up the

29:15

experimental setup, the number of detectors,

29:17

they've played around with their experiment

29:20

and they still see a signal.

29:22

They tried it again with helium

29:24

for a different atomic nucleus and

29:26

they saw the exact same signal.

29:28

They've tried different beam input energies.

29:30

See if that's causing the issue.

29:33

Nope, they still see the signal. And

29:35

they've worked with collaborators around

29:37

the world to build experiments.

29:39

then those experiments also see

29:41

a signal. X17 would

29:43

be huge. If this

29:45

were a real particle, because this

29:47

would be a primo dark matter candidate,

29:50

you're talking about a lightweight particle

29:52

that hardly if ever interacts

29:54

with normal matter, that is the

29:56

definition of dark matter. And so

29:58

this would be huge. But

30:01

But despite all of this, most of

30:03

the most of the mainstream physics community

30:05

has its doubts. its doubts. All the

30:07

independent confirmations

30:10

around around the world have

30:12

some sort of fingerprint from

30:14

the original Hungarian team in in

30:16

them. They participate in

30:18

the collaboration they they go help

30:20

build the detector or they work very

30:23

they work very closely and

30:25

a exchange a lot of

30:27

information as the other group

30:29

builds their experiment. And And

30:31

nobody else outside of the

30:33

Hungarian team has been able

30:35

to reproduce the someone not connected to

30:37

connected to them, not talking

30:39

to them, building their own

30:41

experiment with their own design

30:43

to search for the signal.

30:45

Whenever someone does that, they

30:47

don't see anything. And other

30:49

And other researchers have pointed

30:52

out that and has the exists the

30:54

has the properties that the

30:56

team says it does. it in

30:58

other we should have seen it

31:00

in other history. experiments throughout history. this

31:02

if there's this particle does it does

31:04

this thing, do can't just do that

31:06

one thing in your experiment. It has

31:08

to do that thing throughout the

31:10

entire universe. So like we talked about

31:12

with dark photons dark general. Once

31:14

you you create a new particle, it's

31:17

there throughout the the entire so it should

31:19

be it up neutron stars It should be

31:21

messing up cosmic microwave background. You should

31:23

see it in the large You should see it

31:25

in should have seen it in particle

31:27

experiments from the it in particle There should be

31:29

evidence for it and we don't see

31:31

it anywhere else in the universe see it

31:33

anywhere the Hungarian group has a group

31:36

has a... history of claiming claiming new

31:38

of of particles only for those

31:40

claims to just kind of vanish

31:42

over time so they don't

31:44

exactly have the most reputable track

31:47

record. track record. And are

31:49

some there are plausible explanations

31:51

for the anomaly for to

31:53

the geometry of the detector

31:55

of the it might be

31:57

more efficient at at detecting...

32:00

electrons and positrons at certain angles.

32:02

And so it looks like a

32:04

bump in the signal. It looks

32:06

like you're getting extra. getting extra

32:08

the theoretical calculations, but that's

32:10

only because your detector setup

32:12

is more efficient at that setup

32:14

is more efficient at so it would

32:17

look like a strong signal.

32:19

It It would look like a

32:21

Six Sigma but but it would

32:23

actually be totally bogus because you

32:25

you didn't account systematic uncertainty or systematic

32:28

error in your experiment, which is

32:30

why it's a bad idea

32:32

in general to rely only on

32:34

statistical significance, but that's a

32:36

separate discussion. a separate Given that we don't

32:38

see any new evidence for the particle as

32:41

much as I would like for as to

32:43

exist like for I'm not going to get my hopes up. going

32:45

to get my hopes up yet. And And

32:47

our last particle today, particle

32:49

number five is five, is the

32:51

That's patreon.com slash slash p.m. P

32:53

M S is T E R.

32:55

It is through your contributions

32:57

that this show keeps going.

33:00

I can't thank you enough

33:02

for all of your support.

33:04

I do do appreciate it. just

33:06

kidding. just kidding, it's

33:08

this out. Okay, you've Check this

33:11

out. Okay, you've got your

33:13

fundamental elements like and aluminum. And

33:15

there are so many of them. best we

33:17

the best we could do for a

33:19

hundred years would list and catalog them.

33:22

But then we discovered that the

33:24

fundamental elements weren't so fundamental after all.

33:26

after And actually, all these elements are

33:28

just combinations of three more

33:30

fundamental particles, the the proton, the the

33:32

neutron, and the electron. And so

33:34

this was a massive step forward

33:36

in simplifying the universe. You have

33:38

have the of elements, and then you discover

33:40

that the zoo of of Elm... is

33:43

really just interesting combinations

33:45

of only particles. But then

33:47

in the mid-20th then in the mid

33:49

-20th century, particle colliders started popping

33:51

out ridiculous numbers of particles. And

33:54

like the pion, the cayon, and then we caion, and

33:56

then we actually had to stop giving

33:58

them names and just assign letters to them,

34:00

like the K minus, the D and

34:02

the B. If we're just throwing letters

34:04

out there, that were producing so many

34:06

different kinds of particles. The

34:08

best we could do for decades was list

34:10

and catalog But then we

34:12

discovered that the fundamental particles

34:14

weren't so fundamental after all, and

34:16

they're actually just made of

34:19

combinations of a few fundamental, even

34:21

more fundamental sub -particles, the quarks

34:23

and the electrons. The

34:25

electrons got to stay electrons.

34:27

but the protons and the neutrons and

34:29

the pions and the kons and

34:31

the d's and the b's were all

34:33

just made of quarks. This was

34:35

a massive simplification. We were

34:37

able to reduce the complexity of

34:40

these particles that we were observing

34:42

because we discovered that they were

34:44

really just interesting combinations of. a

34:46

fewer number of sub And

34:50

now? Well, we don't

34:52

have a zoo of elements or a

34:54

zoo of particles, but we have

34:56

a zoo of these fundamental sub -particles.

34:58

We now know that there are six

35:00

quarks. and there are six leptons. The

35:02

electron is just one of those.

35:04

There are also the muon and the

35:06

tau and the three neutrinos. Plus

35:08

there are all the antiparticles, plus there

35:10

are all the force carriers. And

35:13

right now all we can do is

35:15

list and catalog them. So

35:17

maybe. just maybe. The

35:19

fundamental sub -particles, the quarks

35:21

and the leptons. aren't

35:24

so fundamental after all. And

35:26

they're really made of

35:28

even smaller object called prions.

35:31

Not prions as in mad

35:33

cow disease, but pre as

35:35

in pre -quarks, as in before

35:38

-quarks. Prions. The

35:40

idea is that there are only

35:42

a small number of prions. In

35:44

one model, there are just four

35:46

of them called plus, anti -plus

35:48

zero, and anti -zero. and

35:50

that these prions combine in interesting ways to

35:52

make all the varieties of quarks and

35:54

leptons, which then go on to be

35:57

protons and neutrons and atoms, and then

35:59

go on. to be the elements. One

36:01

of the biggest biggest motivations for preons,

36:03

from the fact that this

36:05

general strategy of reduction has

36:07

been working well for quite

36:10

some time, so why stop

36:12

now? so why stop that many

36:14

particles are extremely similar to

36:16

each other, but just differ

36:18

in some tiny way. way like

36:20

the the positron and electron, have

36:22

the exact same mass? mass. the

36:25

The exact same spend, they just differ

36:27

in their charge. their charge. the electron

36:29

and the muon, muon, same charge, exact

36:31

same spin, they just differ in

36:33

the mass, or the up and

36:35

down up and down quarks, they have

36:38

different charges and just

36:40

different masses. when

36:42

you see all these particles. that

36:44

that have but not not quite

36:46

the same properties, it's very

36:48

tempting to suspect that they

36:50

may arise from some other

36:52

interactions. I mean, I mean, theory theory

36:54

has followed a similar logical

36:57

pathway can't we can't just

36:59

throw out the concept altogether. Preons

37:01

have been proposed to explain just

37:03

about every outstanding problem in

37:05

the the model model there are only

37:07

three generations of particles to

37:09

the nature of dark matter, matter,

37:11

but nothing ever quite seems to

37:13

stick, and that's because no

37:15

experiment has given any has given quarks

37:17

and leptons are composite particles,

37:19

so that stinks. so that We try

37:21

as hard as we can to smash

37:23

smash and and apart, but they just keep

37:26

on being themselves. being And then

37:28

there's this massive problem with

37:30

the mass. the mass. Experiments have

37:32

shown that quarks and leptons

37:34

are point to less than

37:36

thousandth the the width of a

37:38

proton. and so so quark which we know

37:40

is which we know is no

37:42

bigger than 1 if it's made the

37:44

width of a proton, or if

37:46

it's made of a those preons of

37:48

prions, those prions have to be

37:50

moving around. to be but they have

37:52

to be moving around an to

37:54

an incredibly small volume. Heisenberg

37:57

uncertainty principle tells us.

37:59

us that it If these particles are

38:01

confined to that small of a of

38:03

a then they they have

38:05

an incredibly high momentum. They

38:07

have to be buzzing around

38:09

in that tiny, tiny little

38:11

box with incredible velocities, with

38:13

incredible energies, with incredible

38:15

mass. with This means means the

38:18

preons have to be so massive

38:20

that they're more massive than the

38:22

quarks and leptons that they supposedly build

38:24

up to be. So in order

38:26

for this to work, there has

38:28

to be some sort of binding

38:31

energy of some sort of interaction

38:33

that cancels out all that mass. seems

38:35

a But that seems a little weird

38:37

and non trying to you're trying to

38:39

build quarks and leptons out of

38:41

preons, but the prions have to

38:43

be more massive than the quarks

38:45

and leptons themselves. So you need

38:48

to introduce some in to interaction, which

38:50

is making this whole point of

38:52

simplification a little too complex. complex. So

38:54

So jury still out on

38:56

There's honestly honestly work in this a

38:58

lot of work in this direction

39:00

I just of the issues I just

39:02

mentioned. people And also to many. their want

39:04

to risk their careers on an idea

39:06

that seems unlikely to pan out. string

39:09

which is unfortunate all the theory has sucked all

39:11

the air out of the particle physics room

39:13

for the past few decades and doesn't have much

39:15

to show for it, but that's a different a

39:17

different show. But like I said, this program

39:19

of reductionism has been working well for

39:21

so long, let's not quit now. now.

39:23

Prions? You all have a y 'all have a place

39:25

in my heart. And And that's it.

39:28

that is my is my list of

39:30

rare particles, but don't particles, but don't

39:32

worry folks, that's only the end

39:34

of this list. five I picked

39:36

five weird particles for today's episode. but

39:39

but there are plenty more out there. out there. have

39:41

to save those oddities. for

39:43

another day. day. Thank you you to

39:45

Lucas L and Jacqueline R R for the

39:47

questions that led to today's episode.

39:50

And thank you to all. to all.

39:52

my patron supporters, that's patreon.com/p.m.

39:54

I would like to thank

39:56

to thank my top contributors this

39:58

month. They are Justin Chris L. Berto M.

40:00

Duncan M. Corey D. Robert Robert

40:02

B. Sam R. R. John Joshua Scott

40:05

M. Rob H. Scott M.

40:07

Lewis M. M. John W.

40:09

Alexis Gilbert M. Jessica M.

40:11

Jules R. Mike M. Jim L.

40:13

R. David S. R. David Heather

40:15

S. Scott H. Steve S. S. Pete

40:17

C. S. Watt, Kuzi Kevin B. Lisa.

40:19

Kevin B. G. G.

40:21

Thank you. Everyone, please keep

40:24

those questions coming.

40:26

That's That's.com or email or

40:28

email a gmail.com. You You

40:30

can also ask through Patreon respond to

40:32

even respond to you on Patreon

40:34

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40:36

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40:38

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40:40

coming, keep the reviews coming that

40:42

really helps the show visibility. And

40:45

I will see you next time for more. time for

40:47

more. knowledge of time and space. time and

40:49

space.