Why are neutrinos so light?

Daniel and Jorge talk about how the weirdest particle gets its mass

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Episode Transcript

Speaker 1 (00:08):
Hey, Daniel, do you think antiparticles feel bad? What do
they have to feel bad about? I think anti particles
are super cool. Yeah, but you know, who wants to
be labeled anti anything? Nobody wants to be the bummer
in the room, you know. I guess that's true. If
you're a cartoonist, does that make me an anti cartoonist?
That doesn't sound very cool. What do you have against cartoons?

(00:29):
Does that make me the anti physicist? I don't know.
I guess it's like with twins, right, there's always one
evil twin. I think that's only true and soap operas.
Maybe I'm watching too many telenovelas. But you know, in
particle physics there is one particle like the photon, which
is its own anti particle. Really, it's its own evil twin.

(00:50):
That's right from the mouth of an anti physicist. Hi
am more handmade cartoonists and the creator of PhD comics. Hi,

(01:12):
I'm Daniel. I'm a particle physicist, and I'm not sure
yet whether I'm a physicist or an evil physicist. And
my physicist or my appro physicist. I guess it depends
on who destroys the world first. Well, I am definitely
anti destroying the world, Daniel, I know that for sure.
I am pro learning about the universe while not destroying it. Okay,

(01:33):
even a while prefix although you know, somebody gave me
the option, like, what if you could learn all the
secrets of the universe, but in doing so destroy it.
That would be a difficult choice. That would be a
difficult choice. Oh my god, somebody take this man's finger
off the button and away from any responsibility. Please. I
second that, I second man. But welcome to our podcast,

(01:56):
Daniel and Rhead hopefully don't destroy the universe, a production
of I Heart Radio in which we avoid destroying the
universe instead take it apart gently, piece by piece, and
put it back together in a way that makes sense
to you. And we like to talk about the galaxies
out there, the stars and the planets and all of
the incredible nebula out there in the cost. But we

(02:19):
also like to talk about the small things, the little
things in life and in the universe, the things that
we are all made out of, like the particles, that's right,
and the things that everybody is puzzling about. We think
that everybody wants to know how the universe works. And
you deserve an explanation that's not just the very basics,
the dumb down version, but an answer that takes you
all the way to the forefront of knowledge, that helps

(02:41):
you understand what science doesn't know right now. Yeah, because
scientists have this standard model of matter in the universe,
is sort of collection of particles and force particles that
they call the Standard Model of physics. Yeah, what do
you think about that name? The standard Model? You give
that an A rating. It's pretty standard, I guess for

(03:04):
physicists to claim something is standard, Yeah, I guess so.
And next I'm gonna tell you it's not actually great,
it's non standard. Now we have the standard model and
it has particles in it that make up stuff. Those
are matter particles like electrons and corks and that kind
of stuff. And we have particles that represent forces like

(03:24):
photons represent electromagnetism, and W and Z particles represent the
weak force, and the gluons represent the strong force. And
then in two thousand and twelve, we found the missing particle,
the Higgs boson. And you'll hear a lot of people
describe the Standard model as finally complete, like the Higgs
boson is the cap on the top of the period

(03:46):
and so, and do you haven't found anything new since?
Even though you've been like colliding particles but higher and
higher energy, you haven't found anything you used since? Do
you sound like sort of demanding, like, hey, what do
you discovered for me lately? You know? But yeah, where
my tax dollars are going to your salaries? That's true,
But remember that searching for new discoveries and particle physics

(04:07):
is like exploring. We're like wandering around the surface of Mars,
turning over rocks, hoping to find little green men or
weird new kinds of life. And it's true that since
two thousand twelve we have not found any new particles
at the large Hage Junklelider. And that gives some people
the feeling like, well, maybe the Standard Model is all
wrapped up. Maybe that's all there is. Maybe we can

(04:28):
just tighten the bow and move on. But there are
lots of really weird little problems with the Standard Model,
lots of interesting discoveries we've made along the way. Yeah,
it seems like a lot of big physics projects in
the US and internationally have sort of turned inwards to
look at one particular particle in the standard model, which
is the new trino. That's right. Often described as the

(04:51):
weirdest little particle, but not because they're rare. Really, yeah,
you call it the weirdest little particle. Yes, in a
in a totally positive way, in a in a very
loving we love you literal neutrinos. No, seriously, so weird
we like you anyways. Is that kind of what you're saying. Yes,
Physicists love the weird, the strange, the unexplained. That's where

(05:12):
the clues are, right, that's where the hints are to
tell you how to unravel the secrets of the universe.
If you look at everything and it just sort of
like makes sense instantly, well, that's boring. We want to puzzle,
We want something strange and weird, and so neutrinos are fascinating,
but again not because they're rare. They're everywhere. There's a
hundred billion neutrinos passing through my fingernail every second. But

(05:32):
there's so much that we still don't understand about them,
really basic questions that just don't have answers to. Yeah,
we are awash in neutrinos. There's no lack of neutrinos
in the world around you. But there is one question
about them that still puzzles physicists, and that's the topic
of today's episode. So to be on the podcast will
be tackling the question wire neutrinos so light? Why are

(06:00):
they light? Not light? Just why is there mass so little?
That's right, it's not like they've been on a diet.
It's not about why neutrinos are bright or not bright.
It's about why they don't have a lot of masks. No,
it's not that their low calorie like coke light. They
are actually low calorie. You could eat like a cubic
light year of neutrinos and gained no weight. It just

(06:25):
goes right through you. That's right. There's zero points on
the Weight Watchers diet. So go have your cheat day,
eat as many neutrinos as you want. Maybe I should
invent like a neutrino based snack. It sounds like toastinos,
but it would be a little neutral snack food, right,
no trino. Yeah, there you go, you know, speaking about

(06:46):
snack foods and quantum physics. We did get a hilarious
email from a listener today who suggested a really fascinating
snack food based physics experiment all snack foods these days
like a physic script experiment, like how ful rest? And
can we make a snack or flame and hot glowing
particles point the late entropy of my snack as much

(07:07):
as Bob. Yeah, And it's not about flame and hot
neutrinos though, that's the snack food I want to develop now.
This listener writes in and he says, I make a
sandwich and I shoot it into deep space. Then I
make a second sandwich, and instantaneously the first sandwich is
converted from new sandwich to old sandwich. And so he's
suggesting this is a version of sort of quantum sandwich

(07:30):
entanglement because the original sandwich is out there in deep
space and suddenly becomes the old sandwich he's made the
new more. Oh man, this is funny that this is
funny to you, Like this is even a job. How
there's just some words that are funny. And I think

(07:50):
sandwich is one of the weasels, as if this was
a weasel sandwich, that would be even funny. I see,
I see, I see. It's it's there's kind of a
joke about how name naming things is kind of like
transmitting information at the speed of light faster than this exactly, exactly,
the universe recognizes that that's no longer the latest sandwich. Instantaneously,

(08:11):
its status has change. It's a sandwich teleportation. Anyway, back
to the topic of neutrinos, back to the topic of
today's podcast. Yeah, why are neutrinos are lights? So I
guess um. First of all, neutrinos are light. Neutrinos are
very low mass. We identify particles essentially by their mass.
We look at the particles when we say how much
mass does it have, and there's a huge spectrum of values,

(08:34):
but neutrinos are the very, very bottom end of it.
We measured these things in terms of electron volts, and
a typical value, like for an electron is half a
million electron volts or a muan is a hundred million
electron volts. How much is a neutrino? Neutrino is less
than one electrono what it's like, Wow, it's like a

(08:57):
percentage of a percentage. Yeah, it's like one million. And
they even go higher like corks are billions of electron vaults,
almost two hundred billion electron vaults, and you know this
is weird. There's a huge spectrum here from a very
very very heavy to very very light, and even between
the leftons and the corks, the electrons and the top
corks example, there's a big range. But neutrinos are all

(09:19):
on their own at the very very bottom of this scale.
And that looks weird. That puzzles us. Really, it's the
only light particle, or I guess, the only low mass particle. Yeah,
because there are you have particles that have no mass,
that's right. We have photons that have no mass, but
neutrinos are the only fermion that have this small amount
of mass. Neutrinos are matter particles, right, and we didn't

(09:41):
know for a long time whether they had any mass,
but we recently discovered that they do have mass, but
it's a very very small amount. So zero makes sense
to us. A number similar to the other masses makes
sense to us. But a really weird, super tiny mass.
That's a clue. That's like there's something going on here
that you could figure out. Yeah, all right, so that's

(10:01):
a mystery. Why are neutrinos so much lighter or have
so much less mass than all the other particles. And so,
as usual, Daniel went out there into the wild of
the Internet, the pandemic Internet, to figure out how many
people o there knew about this mystery and why they
think that maybe neutrinos have such little mass. That's right,

(10:21):
So thanks to everybody who volunteered for the person on
the Internet interviews and listen to these fun answers and
think to yourself, do you know why neutrinos are so light?
Here's what people had to say. I'm not sure why
neutrinos are so as light as they are, as they're
like not zero like photons. Neutrinos get their mass, I

(10:45):
would assume by interacting with the Higgs field, like I
think everything else is supposed to. So why they are
so light would be because they interact very weakly with
the Higgs field. Do they do these interact sum so
they have some mass? Now? Why they interact so weekly

(11:08):
with the Higgs field is another question. I honestly don't know.
Neutrinos are light because they interact weekly with the Higgs
field because of how little they interact with the Higgs field. Man,
I don't know the billions of them flowing through space
all the time, and hardly any of them interact with

(11:29):
us big detectors on the ground filled with bleach or
something like that. I remember might imagine they get their
mass by the Higgs field. So I think that neutrinos
are made of dark matter and they are paired in
such a way that they almost cancel out in each other.
That means they don't show gravitation attraction. Maybe something to

(11:54):
do with inertia. All right, some pretty knowledgeable answers here.
There's a lot of references to the Higgs field. Like, wow, yeah,
some listeners to this podcast have learned something about the
Higgs field. That's awesome. Yeah. So a lot of people
say it's because it doesn't interact as much with the
Higgs field, right, And that's a totally solid answer, because
most particles out there, that's how they get their mass,

(12:17):
like the top cork, the electron, the bottom cork, the muan,
all those particles get their mass by interacting with the
Higgs field. It's almost like a synonym, right, It's almost
like the same thing, like how much mass you have
is how much you interact with the Higgs field. Yeah. Precisely,
before we discover the Higgs boson and understood this mechanism,
we didn't really understand like where mass came from, Like
it was just a description. When you try to push something,

(12:39):
this happens that it tends to take a force in
order to accelerate it. That's really what MASSI is in
inertial mass when we're talking about and then we discovered
this mechanism, this weird feel that if it existed, would
have exactly that property as you push on particles. It
would mean that when you pushed on a particle, it
would take a force to give it acceleration because of
the way this field interacts with those particles. So that

(13:01):
by itself is pretty super cool to take this like
very intuitive macroscopic experience of stuff having inertia and explain
it in terms of this weird microscopic particle interaction. You know.
I love when you can make that connection between the big,
the every day and the tiny, the microscopic. But hey,
maybe that's why I'm a particle physicist and even an
evil one. Alright, So maybe Daniel steps three, or let's

(13:24):
talk about mass and particles and and and just in general,
like how do particles get mass? And before we can
even talk about why one in particular has such little mass. Yeah,
and and remember first of all that most of your mass,
the stuff that makes you up, doesn't come from the
Higgs field. What makes up mass is not just the
sum of all the mass of all the particles inside you,

(13:46):
but also the energy that holds them together, because the
inertial mass comes not just from those particles, but from
any energy that's stored within the interesting because he equals
mc square. Like if you have energy stored, it's like
having mass stored. Yeah, mass essentially is a representation, it's
a feature of having energy. Any energy that's stored has inertia.

(14:08):
It takes some force to get it up to speed.
And that's not something we totally understand. And we could
do a whole other podcast about, you know, the mysteries
of mass and how it works and whether it's connected
to this whole other concept of gravitational mass, which is
the force of gravity between objects. But the thing to
understand is that the mass is this mysterious thing, and
most of it is stored in the energy of your bonds,

(14:31):
but about one percent of it is stored actually in
the mass of those part of So wait, um of
my mass, like how much I weigh and how much
I'm attracted by gravity to this planet is from the
energy inside of me, not from the actual particles. Yes,
but you just refer to gravitational mass, right, which is
a separate concept from inertial mass. Gravitational mass is how

(14:55):
much you're attracted by the gravitational force of the Earth.
Inertial mass is how much force does it take to
give you an acceleration. It's the M and F equals M. Right.
But they're the same, right, It turns out there the same.
I mean, they're different physical concepts, right, one is inertia
on the other's gravity. Turns out the number turns out
to be the same, which is a whole fascinating topic

(15:17):
we can dig into another time. But today we're mostly
talking about inertial mass. Okay, well yeah, yeah, how hard
I am just set a move and most of it
comes from the energy I have. It's stored inside of me,
that's right. If I'm feeling low energy, I should weigh less. Yeah,
And as you absorb energy from the Sun, for example,
you do weigh more. Like you go out in new
sun tan, you actually gain a tiny little bit of weight.

(15:39):
That no, that is true. Yeah, no, it's not measurable,
but every time you absorb a photon, you're getting more energy.
Even though photons have no mass, you absorb a photon,
you go up in mass. One more reason to wear
a hat when you're out in the sun. That's right,
Daniel Whiteson's stay in the dark diet. You should market that.
Eating blame and hot newtree, know, snap chips and staying

(16:01):
in the dark. That's the particle physics anti diet. And
I'm sure'll be anti profitable as well. I just gave
it away for free anyway. So all right, So that's
kind of wild to think about just that, you know,
like we're like batteries almost, Like most of what makes
us us is the energy we have stored inside of us. Yeah,
and we talked about that a lot of times, that

(16:22):
most of what makes you you is not the actual
nature of the particles that are used to build you,
but how they're put together. And that includes the energy
of those bonds. Right, You're like a bunch of lego
pieces bound together really tightly, and it's all about how
those lego pieces gripped together. That's what gives you most
of your mass. But the lego pieces themselves, those electrons

(16:43):
and quirks that make you up. They also have their
own mass, and that's kind of what we're talking about
here today, which is like, what's the intrinsic mass by
itself of the neutrina, that's right. And for electrons, for example,
they get their mass by interacting with the Higgs field.
And what that means microscopically is an electron can be
flying along and you can emit a Higgs boson and

(17:05):
then you can reabsorb that Higgs boson. And that's what
interacting with the Higgs field means. It can create virtual
Higgs boson. Alright, we talked about virtual particles last time. Yeah,
this is not like a real Higgs boson that you
could ever see. Only the electron creates it and can
reabsorb it. But the key thing is that in order
for an electron to be able to emit a Higgs boson,

(17:27):
it has to have an antiparticle. The electron can't do
that if the positron doesn't also exist. All right, let's
dive deep into these particle physics phenomenons and and processes.
But first let's take a quick break. All right, So, Daniel,

(17:55):
we're talking about the neatrino and why it has such
little mass. And we know that most particle get their
mass from the Higgs field, and you're telling me that
this massive that comes from creating virtual Higgs particles and antiparticles.
So every time my particles feel mass, you're saying they're
creating anti Higgs and Higgs boson. It's more about the

(18:15):
electron itself has to have an antiparticle. Will dig into
the details in a moment, but the short version of
the story is that any particle that gets its mass
from the Higgs boson also has to have an antiparticle.
The kind of interaction that it does with the Higgs
field means that to be consistent, it also has to
be possible for a Higgs to decay into the particle

(18:37):
and it's antiparticle. So if you don't have an antiparticle,
this interaction can't happen and you just can't get your
mass from the Higgs boson. The Higgs boson doesn't have
an anti Higgs boson, but in order for the electron
to be able to admit a Higgs boson and then
later reabsorb it, it has to have an antiparticle. There
has to be a positron why every particle that gets

(18:59):
mass from Higgs boson has to have an antiparticle, and
the reason why is fascinating. The way we think about
these particle interactions is three lines intersect. So for this
interaction where an electron emits a Higgs boson, you have
one initial particle, the electron, that's one line, and two
outgoing particles, the electron and the Higgs boson. Those the

(19:20):
other two lines. So maybe make a little diagram in
your mind of an electron line splitting into an electron
and Higgs boson. That's like a mini Fine Min diagram.
Now to be consistent with special relativity. For this interaction
to exist, then others also have to exist. If you
move an incoming particle from this diagram to the outgoing side,

(19:42):
it becomes an anti particle. So this little interaction means
you should also have another one where the Higgs comes
in and outgoes an electron and a positron. But that
interaction can only happen if there is a positron on
Nature's menu. Feel like maybe an audio podcast is maybe
not the best place to use sychematic to explain something,

(20:06):
so maybe let's break it down. I think what you're saying,
is that, you know, if we want an electron to
be able to split into an electron plus a Higgs boson,
which is kind of what happens when you try to
move an electron, then that process needs to be kind
of like reversible, or you have to be able to
get that process from any sort of order. Is that

(20:26):
kind of what you mean? Yeah, that's exactly what I mean.
And some of those reversals turn electrons into anti electrons,
and so anti electron have to be a possibility in
order for this interaction to work. It has to be
like a thing that can exist. Yeah, if the electron
didn't have an anti particle, then it couldn't emit a
Higgs boson. What because, um, I see, if it didn't

(20:50):
have if there wasn't an anti version of the electron,
that means that the whole process has to be canceled.
You can't have that process. Yes, yes, exactly, because this
process also require is this other process a Higgs boson
turning into the particle and its antiparticle. But if the
antiparticle doesn't exist, this process can't happen in any shape
or form. Like everything has to balance out cosmically, kind of.

(21:12):
That's right, because this process an electron emitting a Higgs
boson and then continue along its path. Somebody else from
another perspective could see it differently. They could see it
as a Higgs boson creating a particle and antiparticle because
of special relativity. Remember, everybody can see the same thing
from a different perspective, and so that process has to
also be possible, and that actually happens in the universe, right, Like,

(21:33):
sometimes the Higgs boson will hit a what an anti
electron and become an electron. Yes, sometimes we create Higgs bosons,
for example the Large Hadron Collider real ones, not virtual ones,
and they turn into a particle antiparticle pair like an
electron and a positron bottom cork and anti bottom cork.
This totally happens. It's how we discovered the Higgs boson. Okay,

(21:54):
So it's almost like a prerequisite for having mass is
that there needs to be an anti version of you
to have math exactly right. In order to get mass
from the Higgs boson, you have to have a partner.
You can't dance without a partner, right, you want to
dance with the Higgs, you have to have an anti particle, right,
and it doesn't have to actually exist, It just has
to be possible. Yeah, it has to be sort of

(22:15):
on Nature's list on the menu of things that could exist,
all right, Yeah, yeah, I guess um. For me to exist,
there has to be for me to have maths, there
has to be the possibility of an anti Jorge out there,
even if one doesn't exist, that's right. And so if
you can get rid of the anti Jorges, that means
that you're not going to get any mass from the
Higgs boson. There's a whole other particle physics diet for you.

(22:37):
There you go, the anti anti a twin diet. All right.
So then but then neutrinos. That's that's kind of where
the mystery of neutrinos come in, because neutrinos don't have
an anti version necessarily, right, Well, that's the question. We
don't know either. Neutrinos are just like the other particles
electrons and top quarks and whatever, and they haven't particles

(23:00):
and they get their mass from the Higgs boson, or
they're not. There's some other weird kind of particle that
doesn't have an antiparticle that that is its own antiparticle.
So those are the sort of the two possibilities, and
we don't know currently which it is. What are the
possibilities that natrinos don't have an anti version until they're

(23:22):
just weird and they somehow violate this you know, sort
of karmic requirement of the universe, or like the natrino,
it's so zen with itself that it satisfies its own
anti requirement. But yeah, the two possibilities are one that
it's a normal particle like the electron, it has an
anti particle and it gets its mass from the Higgs.

(23:42):
But in that case we don't understand, like why does
it get so little mass. The other possibility is that
it doesn't have an antiparticle, so it can't dance with
the Higgs, so it can't get its mass from the Higgs,
and it gets its mass in a totally different way. Oh,
I see, those are the two possibilities. Either it has
an antiparticle and it gets its mass from the Higgs,

(24:04):
or it doesn't. It's its own antiparticle and that makes
it this other weird kind of particle called the mayorona
for me, all right, well, um, it sounds like two
appealing options to a not physicist, but what have we measured,
We've met, Have we measured or or found an anti neutrino?
We haven't, right, We have not ever established whether anti
neutrinos themselves exist. We've seen neutrinos, but remember that's always

(24:27):
very indirect like neutrinos hardly ever interact. This is one
of the things that makes them so weird is that
they mostly ignore the rest of the universe. You have
a hundred billion neutrinos flying through your fingertip right now,
and you don't notice because they don't interact with you.
And so it's very difficult to feel neutrinos. And the
reason is that they only interact via one of the

(24:48):
forces that we know, and the weakest one, the weak
nuclear force. And so we have been able to see neutrinos,
and the last twenty or thirty years we've discovered that
they do have mass. But you can't like get a
pile of neutrinos and measure them. You can't say, here's
a spoonful of neutrinos and put them on a scale.
They're very, very light and very difficult to interact with.

(25:10):
So we have these very subtle experiments that can't actually
measure the masses themselves. They just measure the difference in
masses between the kinds of neutrinos, like electron neutrinos and
muon neutrinos and town neutrients. Oh, right, because we found
different types of neutrinos, right, we know there are three
types of neutrinos, and we've seen them change back and
forth from one to the other. We did a whole

(25:32):
fascinating podcast episode about how neutrinos change flavor from electron
to muan to flame and hot no to town neutrinos.
And so what we do know is this is sort
of the differences between the masses, and those are very
very small numbers, and so we we only know that
their differences. We don't know they're like absolute masses, that's right.
We only know their differences. We don't know their absolute values.

(25:54):
We've tried to measure their values and we know that
they're less than some number, but we don't know what
the mass is actually are. But we have measured the
differences between them, so we know, like the difference between
one and two and two and three. That doesn't even
tell us like the order, like which one is heavier
and which one is lighter. We can only measure these
two differences. We know, like, whatever they are, they're really

(26:15):
small compared to other particles. That's right, They're really small,
and they're not zero. And so, for example, if they
do have antiparticles and they do get their mass from
the Higgs boson, then it's a question of like why
such a small number. Every particle to get this mass
from the Higgs boson gets a different amount of mass
because it interacts with the Higgs boson more or less,

(26:36):
Like the top core interacts a lot with the Higgs boson,
the electron not nearly as much. So there's just like
a parameter, like a number, like a dial on the
universe that says how much you interact with the Higgs boson.
And we want to know, like why are these numbers
all different? Why are the values from neutrinos so small.
It's not an explanation to say, oh, neutrinos get their

(26:59):
mass because they hardly interact with their Higgs, Like why
why neutrinos different or weird or special? It's a totally
unanswered question. But it could be that there's no answer, right,
Like it could be that maybe the like the masses
a netrino, it's just a like a basic constant in
the universe that it just is because it is. But
that's not an answer. I don't know. I find that
totally unsatisfactory to say that the universe has like nineteen

(27:21):
different numbers and they just are what they are, Like,
why are they that and not something else? Was there
a moment in the beginning of the universe when these
were randomly chosen? Could they actually be any value? I
feel like sometime in the future of physics will discover
a reason why these numbers are what they are. We
just don't know it yet, you know, There's must be
some pattern, some simplification, some way that we can explain this.

(27:45):
So it's very unsatisfied to say, well, neutrinos get their
mass from the Higgs, and they just don't interact with
it very much for some reason we don't know. Right,
that's weird and unexplained, and that's just option A. Option
B is that it's a totally different kind of particle
that maybe it doesn't even get its mass from the Higgs.
That's right, And early on in the days of particle physicists,
there were two competing ideas for how particles could exist,

(28:08):
one from Paul Dirac, a Familish English physicist who predicted antiparticles,
and another from E. Tore Marana, an Italian physicist who
predicted that particles could be their own anti partner. All right,
let's get into what neutrinos could be and how that
would explain why they have such little mass. But first
let's take a quick break. All right, Daniel, neutrinos are

(28:43):
We know they're weird because they have such little mass,
but we don't know if it's because that's just how
they interact with the Higgs boson, or whether they get
their mass from a totally different way. Is that is
that any impossible? Can you get mass from not the
Higgs field? Yeah? There are other ways to get mass,
and one was predicted by Mayorana, and he came up

(29:03):
with a whole different way to like think about particles. Remember,
most of the particles that we think about today were
envisioned by Paul Diract. He was trying to put together
a theory of quantum mechanics that worked well with relativity,
and he came up with an equation called, of course,
the direct equation that described how particles moved through space.
And it's when he put that equation down on paper

(29:25):
and he looked at it, he noticed he said, wait
a second. This equation suggests not just that particles can
move through space, but that they should each have a partner.
There's like a symmetry in that equation that says, if
there's a particle, there should be an anti version of
version with the opposite charge. That's where the whole idea
of antiparticles came from from this guy, Paul Dirac. And
then of course we discovered electrons do have antiparticles, and

(29:49):
protons have anti particles and all that. Dirac was right.
I wonder if he had come up with a second equation,
what he would have called it? The rise of Skywalker.
Probably the rise of Diract. My second equation Diract strikes back,
all right. So that's one way that particles can be

(30:10):
they can have anti versions of itself. But then then
Majorona came up with another way. Yeah, he came up
with a different equation. He wrote his mathematics differently, and
he thought about the way you could have quantum mechanics
and relativity, and he put the math together in a
different way, and he came up with a way to
describe particles moving through space that didn't imply antiparticles, and

(30:31):
it totally works mathematically, Like, there's no reason we know
of why particles should be like diract particles instead of
like Myrna particles. Wow, but but it still predicts the antiparticles.
My irons particles don't have antiparticles. Well, yeah, they work
without antiparticles. So his equation is different. It doesn't have
this symmetry. It doesn't require there to be the opposite particle,

(30:54):
but it's still right and true. Well, it works mathematically,
but we've never seen one in the universe. So before
we discovered the positron, nobody knew whether every particle was
like the ones described by directs equation or by the
ones described by myronas equations. And then we discovered, oh,
all the particles, we know they do have an antiparticle,

(31:15):
so we'll put them on Diract town. And so far,
my irona has won zero of these battles, Like every
single particle we've discovered so far has been a direct type,
but it's possible that some of them could be Myrona particles.
We don't know. We have no reason to understand why
the universe likes direct particles and not Myrona particles. I mean,
Myrona was a cool dude, all right. So then the

(31:36):
idea is that maybe neutrinos are maybe one of these
Mayorana particles that don't have anti versions of itself. Yes, exactly,
neutrinos could be their own antiparticles. They could be Myrona particles,
so there's not like a separate particle that's the anti
electron neutrino. And if that's the case, if they are
Myrona particles, this special, weird kind of particle nobody's ever

(31:59):
seen before, then there's a very nice explanation for why
they would be so light, why they would have such
a small matting, because I guess Mayorana's equation kind of
allows for some particles who have very little mass. Yeah,
if you take his equations and you say, well, what
if there aren't three neutrinos, there are six, and three

(32:19):
of them are super duper heavy, like cosmically heavy, like
you know, each one weighs as much as like a
planet or something crazy. Then if you do that, then
because of the way the equations work out, you get
three really low mass neutrinos that pop out of the
equation to wait, so he posts that neutrinos don't have
maybe an anti version, they just have a heavy version. Yeah,

(32:42):
there's instead of there being three, there's like six, and
three of them are super duper cosmically heavy. And that
it's called the seesaw mechanism because those guys like steal
all the mass essentially in these neutrino fields and leave
only a tiny little bit left over to the neutrinos
that we know and of, And so this imbalance comes
from the way the matrices are diagonalized, etcetera, etcetera. Falls

(33:05):
out of the math. But essentially it's a very natural,
simple way to solve his equations and to get a
set of very heavy and very light nutreatments. So it'd
be sort of elegant. Instead of like flipping the charges,
you kind of almost flipped the mass kind of. Yeah. Yeah,
that's a good way to think about it. And unlike
with the Higgs boson, you don't have to just like
put a number in by hand. It's like it comes

(33:27):
out of the math naturally. If you have six of
these particles and half of them are heavy, then the
other one has just come out naturally to be very
very light, and that's what we look for. We look
for sort of natural explanations where you don't have to say,
this is just a number and I don't know what
it is. I'm just gonna stick it in there and
see that it works without any explanation. We look for
ways that it's a natural consequence of the math, the

(33:50):
way that anti particles are a natural consequence of directs math.
That tells us directs math is probably right about most
of the universe. Maybe my Irona's math is right about neutrinos,
you know, maybe finally he can get one on his
tally card. But I feel like Mayorana's equation would require
there to be like these crazy particles like a neutrino
with the massive a planet that that doesn't sound like

(34:13):
something we found, And it's not something we found absolutely,
And it's the less Daniel. What if it's dark matter?
What if the whole Earth is just one big neutrino.
But it's a classic trick in particle physics. To explain
something we see, you add a bunch of crazy stuff
that happens with particles that are really heavy because we
can't see those particles. We can't create them in our colliders.

(34:35):
We don't have enough energy. They're too rare, they would
they haven't been around since the Big Bang, And so
it's sort of like sweeping stuff under the rug, you know,
you push up all your problems into the really heavy
particles which nobody ever sees and are never created, and
so sort of can't be found. Kind of thing can't
be found exactly right, because to like create a planet
sized neutrino would require a crazy particle collector, yeah, particle

(34:58):
collider the size of a galaxy probably to create that
much energy, or like require conditions like the Big Bang, right,
because right now today it would be very unlikely for
us to see something like that if it existed or
could exist. Yeah, essentially impossible. Nothing is technically impossible when
you're talking about quantum mechanics, but essentially, but there are

(35:19):
ways for us to figure out if neutrinos are their
own antiparticles or not. All right, that would settle the
question of what kind of particle in New trinas are.
That would settle a question because if neutrinos have their
own antiparticles, then their direct particles and he basically runs
the board and wins everything. But if they do not
have their own antiparticles, if they are their own antiparticles

(35:42):
like the photon is, then my irona wins one. Now,
you know, if people get confused, we're only talking about
matter particles here. There are there are some particles like
the Higgs and the photon, which are their own antiparticles,
but they're not matter particles, so they're not governed by
this direct versus myron and distinction. Feel like, now they're
they're steaks. Daniel Well, I really like the math of

(36:04):
the Myrona particles, and so I'm sort of rooting for him.
I also like the underdog, you know, it's like, let's
give him one. Guys, come on, throw my bone. That's right,
Let's give him what. Also, let's give them the weirdest, best,
awesome one. Neutrinos are fascinating, so if you have to
pick one to win, it would be neutrinos. All right,
So you're saying, even if neutrinos are their own antiparticles,

(36:24):
that would still put them in the dirac column. Know,
if neutrinos have an antiparticle, that would put them in
the direct column right right, the opposite of what just
I just said. Yeah, if the anti of what you
just said, if neutrinos are their own antiparticles, then they're
in the myrona carloge and we have a possibility to
maybe even see this, to discover to tell the difference
between those two hypothesis, to figure out if neutrinos are

(36:46):
their own antiparticles or if they have antiparticles. Al Right,
it sounds like we have um overtime penalty goal here,
so maybe real quickly describe what this experiment is. Well,
it involves beta decay. Beta decay is the process where
you take a neutron and it turns into a proton
and it happens all the time. It's radioactive decay. And

(37:07):
what you get is a neutron turns into a proton
plus an electron and a neutrino. And this is actually
how neutrinos were first discovered, because we saw that neutrons
turned into protons and electrons. But there's some missing information
because we can't see the neutrino itself, and so people thought, oh, well,
there must be some little neutral particle carrying off some energy.

(37:29):
That's the origin of the name neutrino. Like little remaining
like a little remainder. Now, sometimes there's some nuclei they
can't do this, But what they can do is they
can do double beta decay. They can take two neutrons
simultaneously turn them into two protons, which should give you
also two electrons and two neutrinos. So what people are

(37:51):
looking for is neutrino lists double beta decay, the idea
that these two neutrinos that are produced one from each
to the neutrons might combine and annihilate each other. If
they are their own antiparticle, then they can do that.
They can just like slurp into each other, disappear, disappear. Yes,
but it sounds like maybe the idea is that there's

(38:12):
an experiment in which two neutrinos are created at the
same time, and if we suddenly see these two neutrinas disappear,
then that means that they are their own antiparticles and
they did sort of cancelate till they're out. Yeah, exactly.
So if neutrinos are myrona particles, then double beata to
cake can happen without any neutrinos flying out to be

(38:33):
like neutrino lists, double beta decay, and you might ask like, well,
how is it possible to even tell, Like you can't
see neutrinos directly, so how can you tell, like if
there weren't two neutrinos there, if there were, or there weren't. Yeah, well,
if there's a neutrino there, it carries off some of
the energy. Like that's how neutrinos were discovered. Remember, you
add up the energy of everything else and it doesn't

(38:55):
add up, like all the energy that came out doesn't
equals to the energy that went in. That's the evidence
for the existence of a neutrino. So if you see
this happen and there's no missing energy, no energy is lost,
then that tells you that there probably was no neutrinos created,
and neutrinos annihilated themselves. That you have neutrino lists double beat.

(39:17):
It sounds kind of impossible, right, Or what if the
ntrinos were created, they took some of the energy, but
then they canceled each other afterwards. Yeah, well it could
be that they like just go off in opposite directions
and so they do cancel each other. It's a very
hard experiment to do. So far, nobody's ever seen neutrino
list double beta decay. Nobody's ever seen this happen. But

(39:39):
it's difficult, right to have evidence for this not happening.
You have to create the situation where you think it
could happen, and then prove that you would see it
if it did happen, and then not see it. So
it's a very subtle experiment. It's hard, but I totally
lost a few steps back there. But it's like you
have to see something that's not the air, or you

(40:01):
have to you have to you have to not see
note that is there but not there at this time.
It's a very subtle experiment and total props to the
folks looking for a neutrinnutilists double bated a gay. It's
a fascinating question in particle physics, but it connects to
as much bigger, deeper question of like how do particles
get mass? And do particles have their own antiparticles? And

(40:22):
you know, why are there antiparticles anyway, which is a
question I've never really wrapped my mind or interesting. It's
it's like a little detailed question that's subtle, but it
might sort of upend the whole basis for the standard
model and our whole sort of understanding of what particles
are and what's possible exactly. And so the discovery of

(40:43):
the Higgs boson it's not the crowning achievement of the
standard model. That doesn't put the last piece in the
place and answer all of our questions. We don't step
back and go, oh, yes, beautiful, we're done. We've done it. No,
We're like, there are so many weird little bits that
don't make any sense, hanging ugly things off the back
of it, that we want to try to understand and
smooth over and figure out, because hey, we like the

(41:05):
weird stuff, not the shiny and cool stuff. All right, Well,
it sounds like there's still big questions out there about
our understanding of particles in the universe, And um, I
think it's time for people to the side. You know,
are you pro Dirac or anti new Urana? And it
is that the same thing? And what would happen if

(41:26):
Dirac and Myrna went to a conference together within an
highlate each other with the same energy and the opposite direction.
Would we even be having this conversation? That's right? Well,
I'm on team Irona because I hope that the universe
is weird, and then we find new stuff. If it
turns out that neutrinos have antiparticles and get their mass

(41:46):
from the Higgs, just like all the other particles, and
that's much less exciting than discovering a whole new kind
of particle that does something weird. So you're pro weird
or anti standard, that's right. I'm rooting for the model
of physics, not the standard model. All right, Well, we
hope you enjoyed that, and I think a little bit
differently the next time you look up into the sky

(42:07):
and um realize that you're based in these weird, mysterious
neutrinos that are maybe something totally different than the rest
of the universe, and maybe they hold a clue to
something even deeper about the nature of matter and reality
and the whole universe. Thanks for joining us. Let's see
you next time. Thanks for listening, and remember that Daniel

(42:35):
and Jorge explained. The Universe is a production of I
Heart Radio. For more podcast for my Heart Radio, visit
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