Do photons bump into each other?

Daniel and Jorge bump brains and talk about whether beams of light interact or pass through each other. 

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Episode Transcript

Speaker 1 (00:08):
Hey, Daniel, I have a question for you, very important.
All right, what is it? How close are we to
having real life lightsabers? You're asking a physicist that question.
I would ask the same question to my favorite engineer. Wait,
do you think it's an engineering solution? Do we need
like some kind of breakthrough in theoretical physics first? No,
I mean the science fiction authors have done their job
already and they passed it on to the physicists. Oh yeah,

(00:30):
and the physicists I figured out how to do it. Well,
you know, we've been smashing photons together to see what happens,
and how does that do as a lightsaber? Well, so
far it makes a really awesome sound, like but kind
of cut through swords and deflect like guns. That's the
engineering problem. Hi am or handy cartoonists and the creator

(01:04):
of PhD comics. Hi. I'm Daniel. I'm a particle physicist
and a professor at UC Irvine, and until a moment ago,
I had never made a lightsaber sound with my mouth. Yeah,
we could tell that was terrible, Daniel. All right, let's
hear your lightsabers sound. Right, sounds a lot more accurate. Well,
we'll let the listeners vote I think the coolest sound though,

(01:26):
is when they clash, you know, because they're like woman,
it's or something. When they hit that's even worse, Daniel,
everyone knows it's oh, that was much better. All right,
You're right, that's definitely better. And those movies are ingrained,
are burned into my brain, for better or for worse,
like somebody inscribed them with a lightsaber, like somebody was
their hand and said I would only remember these movies

(01:47):
for the rest of my life. It would be pretty
awesome if the movies themselves were a Jedi mind trick,
but I think they were. They certainly got a lot
of my money out of my pocket. These are the
movies you want to pay for. But anyways, welcome to
our podcast. Daniel and Jorge explain the university production of
My Heart Radio, in which we pull off the physics
mind trick of attempting to understand the universe. We convince

(02:11):
ourselves and hopefully convince you, that the crazy cosmic mysteries,
the grandest questions of the existence of humanity, the things
that philosophers have been wondering about for thousands of years,
the very nature of our reality and its meaning, can
be understood by tiny little squishy brains living on a
little rock orbiting a very normal star. We talk about

(02:33):
all of these questions and we explain all the answers
to you. That's right. We used the force to understand
the forces of the universe and to look out to
galaxies far far away and actually also a long long
time ago to understand how it's all put together and
why it's all hanging there the way it is. Because
everything around us presents mysteries. How do these things work?
What happens when they bump into each other? And as

(02:54):
a particle physicist, my favorite way to understand how things
work is to do exactly that. Smash them into each other,
or collide them into each other, or blow them up,
whatever you prefer. Yeah, because the universe has a dark
side and also a light side, and it seems to
be in constant struggle with itself, bumping into each other,
colliding fields, interacting with each other, all of it to

(03:16):
create this amazing spectacle that we can see just by
looking out into the night sky. And we've made remarkable
progress in understanding the very nature of the universe by
describing space itself and everything out there in terms of
oscillating quantum fields, these things which fill the whole universe
with their energy and slide and smush against each other

(03:37):
to come together to describe the reality that you and
I experience. Wait, Daniel, you mean it's not all made
out of medic clorians, little tiny beings that you know,
bind everything together. The medic Clorians were biological, not quantum mechanical.
They never described it in Star Wars. Maybe they are
quantum mechanical. Maybe they are quantum biology. Yeah, maybe right, Well,

(03:59):
it seems almost the same. I mean, you're saying that
the universe made of these fields that are bound together
with these little tiny things that bump around each other
and somehow direct the cosmos. That's kind of what George
Lucas was saying. That's kind of what everybody was saying.
If you're going to say kind of and be really
generous about it, you know, yeah, kind of. But I

(04:20):
love this picture of the universe as all these different
quantum fields. You have like a field for the photon,
you have a field for the electron, you have a
field for the corks and you know those fields we
can think about is having particles in them would slide
around and keep a little discrete blob of energy. And
we've talked to the podcast about how particles are these
little ripples in the quantum fields. But one of the
most interesting things that these fields can do is talk

(04:41):
to each other. The photon field in the electron field
don't just fill the space of the universe and ignore
each other. They interact, They touch, they bind together, they
transfer energy back and forth. Yeah, and thankfully, I guess right,
because if all the fields ignored each other, like nothing
would ever happen. We wouldn't be here. We're here because
of those interactions. In a way, every interaction between two

(05:02):
different kinds of particles, the way the electron is bound
to the nucleus of the atom, the way chemical bonds form.
The reason you don't fall through your chair is all
because those quantum fields don't ignore each other. It's because
they interact with each other, because they pass energy back
and forth. In some sense, it's a bit of an
artificial distinction to say we have two different fields. Might

(05:22):
want to think of them holistically, is one bundle of fields,
one force with the dark side and the light side, right,
I think you're kind of saying the same thing, one
force to rule them all. Now I'm mixing our mythologies.
We need to have like a Lord of the Rings
Star Wars crossover event. Who would win? Oh my goodness,
fan fiction writers get on it? Are those owned by

(05:44):
like different corporate conglomerates, in which case will never happen.
Not on the internet. Anything can happened on the Internet.
That's true until Disney's lawyers come after, you know, Disney
buys Lord of the Rings. Then we might get like
a Marvel Star Wars Lord of the Rings for a
crossover right, Oh my goodness, would throw iron Men in there,
And I'm all in Gandolf versus iron Man. Well, who

(06:08):
would win? Doctor Strange or Gandalf or the Wizards. I
don't know who's got a better grasp on the quantum fields,
but it is interesting and things like Star Wars they
use lasers, right, laser guns to shoot at each other,
and also lightsabers to cut through appendages, and also doors
and walls. And it's interesting to think that light can

(06:29):
interact with matter, Like if you shoot a laser, it's
gonna burn a hole through your wall, right, And you
can even use light to push a solar sale, to
push a spaceship off of the solar system. Exactly. Light
is really weird. It has energy, it has a momentum,
but it doesn't have any mass, and yet of course
it can influence our world because of that energy. In
that momentum, A laser will deposit a lot of energy

(06:50):
in a very small spot and burn right through it.
And that exactly happens because those photons can interact with
charged particles. The quantum field of photon and the quantum
field of those electrons or muns or quarks can interact
and pass energy back and forth. I always wondered when
I watched those lightsaber battles. I thought, how does that work?
How do two lightsabers, two beams of light hit each other? Well,

(07:14):
this is getting a little philosophical, Daniel. Our lightsabers beams
of light actual like light that just stands there and
sits there. Or are they like some kind of material, like,
you know, like a plasma beam. Wouldn't they be called
plasma sabers? Then? I mean they are called lightsabers, and
I imagine George Lucas knows his quantum mechanics. Yeah, but
maybe they're called lightsabers because they give off light. I

(07:36):
guess that's a good point. You know, light bulbs are
not made of light. As we're getting deep here, this
is very stimulating, illuminating conversation here, well too, bright minds.
You know, let's see what we can do. I guess
we were talking about interacting things interacting, and you know,
it's kind of interesting that electrons can definitely interact with
other electrons, right, like an electron will repel another electron,

(07:59):
and like a proton will repel no, the proton like
things seem to be able to interact with it themselves,
but not directly. Actually, electrons do not interact directly with
other electrons. Electrons interact with photons, and photons interact with electrons,
sort of like having an interpreter, and you can talk
to the photon and the photon can talk to the
other electron. But electrons don't interact with each other directly.

(08:22):
I see, you gotta go through their agents, like talk
to my people exactly. It's like electrons are celebrities. They
don't just email you there people email your people. But
I guess this brings up the an interesting question, which
is what do photons interact with specifically? Yeah, exactly when
these two lightsabers are about to cross, and to make
that sound that I can't make what exactly is going

(08:44):
on at the microscopic level in George Lucas's mind. Yea,
so it's the On the podcast, we'll be asking the
question do photons bump into each other? And Daniel this
seemed a little risk a like, what do you mean
bumping to each other? Like they bump and grind like casually,

(09:04):
like oops, sorry, bumping to each other? Yeah. Well, you know,
photons can do all sorts of things. They can be
circularly polarized, so I guess they can do like spins
on the dance floor. And you know, I'm not one
to tell you what's appropriate and what's not appropriate. Talk
to your parents about that. But this is more of
a physics question. You know what happens when two beams
of light cross each other? Do the photons ignore each other?
Do they hit each other? Two photons push against each other?

(09:27):
You know what happens when you cross the streams. Oh,
and now we're getting to another mythology. Ghostbusters do not
cross the streams exactly. I want to see bankman versus
Gandolf versus a jedi. Now, oh, obviously Agreman would win.
I mean, the smart engineer always wins. I don't know.
I Bankman is quite the smart professor. Yeah, because I
think this is something that I wondered about as a kid.

(09:49):
Like if you take a flashlight and you take another
flashlight and you point them not even at each other,
but just like pointing them in the same direction, or
cross their beams, Like, what's happening there? Like, what's happening
to the Do the light beams ignore each other or
do they kind of interfere or somehow scatter each other.
So you're saying you wanted to understand light and so
you make light collisions? Well, I don't know. Is it

(10:11):
possible for light to collide? That's the question of today's episode.
Can create a collite, a photon collider? So that's the
big question we're asking today is can light bump into
each other? Does light interact with itself? Because not every
particle interact with other particles. Neutrinos, for example, ignore most
of the matter in the universe, sliding right by as

(10:32):
if it wasn't even there. Each particle, each ribble in
the quantum field, can either see other fields or ignore
the other fields. It's not like an option, it's not
like it depends on its mood. Some of these fields
couple with each other, and other fields just don't couple
with each other at all. Well, it's kind of interesting
because I know we've talked about this a lot before.
How there are two kinds of particles. There are matter particles,

(10:52):
like the stuff that we think of the stuff, and
then there are force particles. And so a photon is
a force particle. And so the question, I guess maybe
a larger question is to force particles interact with themselves.
It is a really interesting and deep question. Some of
the force particles can actually interact directly with themselves, and
others interact indirectly with themselves. But as we'll learn today,
there's several layers of nuance to the answer. All right, well,

(11:15):
we'll get right on it. But as usual, we were
wondering how many people have thought about this like question,
this question of whether light can interact with itself? And
so as usual, Daniel went out there into the internet, Daniel,
or to your campus. These are questions from our cadre
of Internet volunteers. So thanks very much for everybody who
continues to participate and fill my inbox with these really

(11:35):
fun answers. I greatly appreciate it, and if you'd like
to hear your voice on the podcast, please don't be
shy right to us. Two questions at Daniel and Jorge
dot com. Yeah, so we ask folks, do you think
that photons bounce off of each other? Here's what people
had to say. Since photons do not have electric charge
and mass, I think they do not bounce off each other.

(11:58):
I think that photons should bounce off each other because
in physics we learned that photons are particles that act
as waves because they have a particle wave kind of
duality to them. So if their particles, they should be
able to bounce off each other. But also at the
same time, they're very small, so the rate that they

(12:20):
do bounce off each other so small because it's very
hard to hit two very small particles together. I would
think not. I think they pass right on by each other. Yes, yes, yes, yes?
Why or how? Wait? Pick up? Oh? Maybe they don't

(12:43):
wait protons? Maybe they need neutrons. Do you know what
a photon is? A photon? What's a photon? Way? A
photon will need to stick to a proton what is
a photon? Wait? Is it too protons? I would say
the photons can bounce off each other, because I know

(13:04):
my understanding is the photons don't have mass. But I
know the idea of a light sale requires bouncing photons
off of them. So it's something about the momentum or
energy of a photon can actually impart some momentum into
an object. So I would say because of that, photons

(13:26):
probably can bounce off each other if shot at each other,
just right, if I remember rightly, you've said on some
prior episode that photons do not bounce off each other,
but just pass right through. One might think they would
bounce off because of their particle nature, but they also
have wave nature, and I guess that's what lets them

(13:50):
pass right through each other. I don't believe photons can
directly interact with each other, being waves as well as particles.
They just passed through, uh, interfering or not on their
way through, but then continuing on their happy ways. I
really don't know. I suppose they could. I know, if

(14:11):
they hit hard enough, they'll break into other things, all right.
I like that kid's answer. That was pretty funny. Yes, yes,
of course, Wait what I love hearing people think about
it on the fly, their initial reaction and then their
physics brain engages and they're like, hold on a second,
is that really the way this works? Really? They have
two brains. I have lots of small brains all wrapped

(14:33):
up together. To my, oh boy, that's a weird picture.
Like if we open your skull, we wouldn't find a brain,
We just find a whole bunch of little brains. Yeah,
I'm like nineteen little brains in a trench coat, not
actually a full person. Boy, that's a bit disturbing. I
guess you know, you've got different parts of your life
and so you gotta engage like, oh I need dad brain,
or I need husband brain, or it's physics brain time.

(14:57):
I find having split personalities is a bit of a problem.
I see. So everybody's always just getting the same cartoon
is braining all the time. Everyone's just getting the whole brain.
There's no menu option. You get what you get and
you don't get upset. But yeah, pretty interesting answers here
from people. Some people think they yes, definitely they do,
and some people think they definitely don't. And here's an

(15:19):
interesting answer. Because they're waves. Can two waves interact with
each other, yes, right, no reason why not. Like, two
waves definitely can interact with each other. If you've seen
waves in the ocean, you know they can add up together,
they can even cancel each other out. So waves can
definitely interact with each other. And photons can do that
as well. You know, we've seen like the double slit experiment,
is interference between photons, and so waves can definitely interact

(15:43):
with each other. That's not an issue. But I guess
in water in the ocean, if you get like one
wave going one way and another way of going the
other way, they do sort of mix in the middle,
but afterwards they just keep going as if they hadn't interacted, right, Yeah.
The effect that you see is a superposition of the
two waves, and so there isn't necessarily direct coupling between
the waves, but what you see is the addition of

(16:04):
the two waves. In that sense, you experience the combination
of them. But the individual waves can still be thought
of as individual waves. Yeah, but then they keep going
as if they hadn't interacted, right, Yeah. No, that's a
good point. They don't interact with each other the way
they would interact with for example, a boundary or a
wall where they really would reflect. Yeah, they just sort
of ignore each other. I mean in the moment, if

(16:25):
you're setting in the middle, you would experience both waves
and they would add or substract, but they eventually the
waves keep going right. Yeah, that's true. And so the
question is does the same happen to photons? That is
indeed the question of the episode, And what happens when
two photons getting near each other? Do they ignore each
other or do they bounce off each other? Or do
they do something else? All right, well, let's diget into it, Daniel,

(16:45):
I guess, first of all, what does bouncing off actually mean? Like,
what does it mean for one particle to bump into
another particle? Do they actually bump? Yeah, so the microscopic
view of bumping into things on the dance floor or
sitting in your chair or whatever is sort of the
conceptual view that you might have. You know, you probably
imagine that the reason that you don't pass through a

(17:05):
wall is that like the surface of your body is
touching the surface of the wall and it's pushing back. Right,
But what do we really mean by touching? Like microscopically?
Zoom in? What's happening. Well, you know, the surface of
your body is a bunch of atoms, and those have
electrons around them. So really the tip of your finger,
for example, is a bunch of electrons, and the edge

(17:26):
of the wall, the surface of the wall, is also
a bunch of electrons. And what happens when you push
one against the other. The electrons themselves don't have to touch, right,
They can repel each other without actually touching. So this
microscopic view of the world from a physics point of view,
there's no actual contact between these particles. It all happens
via the fields between them, or equivalently, the particles that

(17:49):
they're passing between each other. So when your finger pushes
against the wall, it's ripples in the electromagnetic field or equivalently,
photons that are transmitting that information that are pushing back
back on you. Yeah, but you know, I think we
have everyone has this intuitive feeling that things touch each
other because like, my finger has a volume and the
table has a volume, and that two objects can't sort

(18:13):
of occupy the same space at the same time. And
so if I press my finger against the table, like
somehow the universe is resisting my finger being in the
same place as the table, But two things can occupy
the same place at the same time. Your body is
full of neutrinos right now as well, and they're passing
right through you and ignoring you. They are taking up

(18:34):
your volume. The only reason you perceive a volume, the
reason you think there's a boundary between your particles and
the other particles is when there's a force between them.
Neutrinos don't feel force, so they're just trapes right through
the edge of Jorge and then out the other side,
No big deal. The reason the table and the chair
doesn't is because there's a force that prevents them. So
it's really all about the force you can imagine things

(18:55):
is sort of like with virtual springs between them, preventing
them from getting too close, but there's no actual contact.
Contact doesn't really mean anything. All there is is forced
between particles, right. I think that's what you're saying, is
that this idea that my finger can't occupy the same
space as the table is really just kind of an illusion, right,
because they could, I guess. But something is I'm not

(19:16):
preventing my cluster of atoms in my finger from somehow
being or you know, penetrating or infringing upon the volume
of the atoms cluster together on the table. Yeah, and
I wouldn't say the volume is an illusion. You know,
people talk about like atoms being mostly empty space, and
I think that's cool to give you the sense that

(19:37):
like it's made of tiny particles, But it's also a
little bit misleading that space isn't empty. It's filled with
fields or with virtual photons that are zooming around and
keeping everything in its position. You can define what your
volume is, but that volume, the edge of it, is
not defined by like the stuff that you're made out of,
but the fields from that stuff, the forces of that stuff,
And the volume also depends on what you're touching. Right,

(20:01):
you want to touch a blob of neutrinos, then your
volume is different. Then you want to touch something like
a table or a chair. Right, So, because the volume
depends on the fields, and not everything feels those fields,
then the volume is a little bit dependent on what
you're touching. Right. I think you're saying that, you know,
instead of thinking of our fingers or at the table
as collections of stuffy particles, maybe it's better to think

(20:22):
of them as like clusters of ripples in the fields
of the universe, Like my finger is not really a finger,
is just a whole bunch of ripples kind of tightly
cluster together. And so this whole bunch of ripples doesn't
want to just um go through the bunch of ripples
of the table. There's are forces that push my group

(20:42):
of ripples against the tables group of ripples. That's right,
And I like the sound of the word ripples, And yeah,
you are made of little matter ripples, right, your particles,
And you can think of as like little ripples in
quantum fields of matter. And the way those things stay
apart again is not that they are physically touching each
each other, but that they exchange other kinds of ripples,

(21:02):
these force ripples between them. So you can think of
yourself as like a cloud of these little matter ripples
that are maintaining their distance from each other by passing
back and forth these other little ripples, and also maintaining
their distance from other things. But there's no microscopic equivalent
of touching. The surfaces are not like actually coming into contact, right,
but in a way sort of like my ripples, like

(21:25):
my way functions of my ripples are touching the way
functions of the other ripples, and so that's that's kind
of like touching, right, They're getting into each other's business.
Another way to say, instead of saying there is no
touching is to say, that's exactly what touching is. That's
how touching works. Your experience of touching means these particles
are communicating with the other particles, but they don't have
to be on top of each other. And this is

(21:45):
something that physicists struggle to understand for a long time.
They call this spooky action at a distance, because we
like to think of physics as local, that you only
affect things that are right next to you. You can't like,
do something here and instantly affects things in andromeda. We
like to think of physics is only happening in like
a very close vicinity to an object. And so this
idea that like an electron could push another electron without

(22:07):
actually touching it was a little bit weird for physicists
for a while. And then they invented this concept of
a field that the electron creates this field around it,
which then pushes on other electrons. Right, And like you said,
it's sort of all depends on which fields you're talking about.
Like some fields do interact with each other and some don't,
Like there could be a whole house made of neutrinos
falling on top of me right now, but it'll just

(22:29):
keep going and won't touch or interact with any of
my ribbles. Exactly in, each particle that's out there has
a different set of ways to interact. Like the electron
can interact via photons. It can also interact with the
weak force, so you can interact using ws and interact
using zs for example. So it's got like two ways
to talk to other particles. You can speak two different languages,

(22:50):
whereas the corks they can speak a third language. Right,
they can interact via gluons because they feel the strong force,
and the neutrino only speaks one language, just the weak force.
So depending on which kind of particle you are, you
see the universe very differently. Right. Either it's filled with
stuff that wants to talk to you, or it's filled
with people speaking gobbledygook that you can't understand and mostly
just ignore. All right, well, let's touch on this a

(23:12):
little bit more and we'll speak to what some of
these forces are up to. But first let's take a
quick break all right, we're talking about the question of

(23:33):
what's going on in Star Wars when a lightsaber hits
another lightsaber, Daniel, is the light actually touching it itself?
Is is it colliding? Or is that actually something that's
impossible in the universe. Did George Lucas make all that
stuff up? Then? You know, he has a huge budget,
so I'm sure he did all the R and D
necessary to make sure that Star Wars is realistic. But actually,

(23:55):
didn't Star Wars happen a long time ago? So in
principle all this stuff has already and developed. Yeah, well,
it depends on who the movies for, you know, like
that the movie could be for aliens who are really
far away, in which case it will have happened a
long time ago from them. I see. Wow. I wonder
if he wrote that into his contracts, you know, future
kinds of revenue from alien galaxies. He was pretty savvy,

(24:16):
I heard. I'm sure those contracts say everywhere in the
known universe, and some lawyer out there is like, oh,
what if we discover a new universe? Does this contract
extend to merchandise sold in the multiverse? Yeah, although actually
George look has sold everything Star wars did Disney try?
So Disney owns the universe, that's right. Yeah, Well, we're

(24:37):
talking about whether photons interact with photons, whether light can
hit light, I guess, or interact with itself. And so
we talked about what it actually means for particles to
interact with each other, and it sort of all depends
on what fields are in and how they interact with
each other. One thing I think that's interesting that you
said is that sometimes particles don't actually interact with each other,
but they have sort of intermediary feels they talk through.

(25:01):
Like an electron doesn't actually interact with another electron exactly.
Electrons can interact with a very small number of particles directly.
They can interact with photons, ws and zs, and that's it.
Like electrons can only interact with force particles. They can't
interact with other matter particles, not directly. Like if you

(25:21):
look at the equations of the standard model, we have
all of these fields and we say very specifically which
fields can talk to the other fields, and the electron
can only talk to the photon field, the W field,
the Z field, and actually also the Higgs field. Wait
are you saying that like an electron can actually be
on top of another electron, is in there some sort
of like universe rule that says no to electrons can

(25:42):
be in the same place. This certainly is that rule,
and so quantum mechanics prevents that from happening. But that
would never happen anyway, because electrons, though they can't talk
to each other directly, they can talk to each other
via the photon. And so the way we build up
our description of the universe is we have these little
basic building blocks, like what are the simplest things that
can happen, and then from that you can build up
more complex things. You can say, well, an electron can

(26:04):
only talk to a photon, but that means a photon
conduct an electron. So then you put together this two
step process when electron talks to a photon, which passes
the information to another electron, sort of like when the
parents are arguing and the interact via the kids. You know,
tell your mother that dinner will be ready at six pm.
I don't know what you're talking about, Daniel, what sort
of house are you running there? I mean, I've just

(26:25):
seen that in the movies. I've never had an argument. Right, Well,
we'll tell our agent that I don't agree with them,
all right, Remember that this is like our description of
the universe. We try to boil it down to the
simplest set of interactions, and then we can use those
to try to describe all the complex phenomena that we
see out there, some of which can be described with
just the basic pieces, and some of which requires us

(26:46):
to put two or three of these pieces together to
describe everything that happens. But it's kind of weird to
think that if there wasn't a photon field, then you
could have electrons kind of running into each other, kind
of right occupying the same field in the same spot.
It's pretty hard to think about a universe without a
photon field because it would break a lot of our laws.
Remember we have this episode about gauge invariants actually need

(27:08):
photons around for electrons to behave properly to like conserve
electric charge and all that stuff. Member forces aren't everything
in physics. They're also just rules of quantum mechanics. Electrons
can't be in the same state as another electron, and
that's not like due to a force, it's just something
electrons don't do. Alright, So then all electrons have to

(27:29):
go through the photon field to talk to each other. Um,
what about things like courts, So quirks can do the
same thing. Quarks interact with all the same particles that
electrons do, plus gluons. So if two quirks are approaching
each other, they have a lot of different ways to
talk to each other. They can exchange ws, they can
exchange zs, they can exchange photons, or they can exchange

(27:50):
those crazy particles, the gluons, and so again. Corks don't
talk to each other directly. Right. Matter particles never interact
directly with matter particles. What they do is they interact
via the fields they create, which is equivalent to saying
that they interact via these force particles. Right again, just
to be totally clear, you can imagine like the electromagnetic

(28:10):
field that a cork generates because cork has electric charge
like two thirds or minus one third, and another cork
is flying through that field and fields of force. That's
what the field is. Right. Another equivalent way of thinking
about it is thinking of that field is a bunch
of virtual particles being created by the first cork. There
are two equivalent ways of thinking about particles interacting either

(28:32):
via fields or via virtual particles. But I guess maybe
like a philosophical question is, could you have a universe
without a photon field or a gluon field and still
like makes sense mathematically, like is it just coincidence that
somehow course can talk to each other via the glue
on field or is it not even possible for courts

(28:53):
exist without gluons. I mean philosophically, you can put together
all different kinds of universes. You can put together universes
with just quirks in them, or just electrons and them.
Of course you wouldn't get any interesting complex structure. Like
everything that we know and love about the universe comes
from the fact that these particles do interact and make
protons and neutrons and atoms and chemistry and ice cream
and all that good stuff. So you wouldn't get anything interesting.

(29:16):
And if you have these fields and they couldn't talk
to each other, you couldn't form really any kind of
complex structure. Also without these forces. Remember, these forces exist
to preserve symmetries that we observe in nature between these particles.
So there are symmetries among the corks and symmetries among
the electron and the other particles that are preserved by
these forces. Check on our episode Engage Symmetry to explain

(29:37):
a little bit more what I mean. You have to
have these forces if the universe has these symmetries, though
we don't know why the universe has these symmetries. So
you could in theory create other universes without these symmetries
and without the forces, but they would be pretty boring. Yeah,
there would be there would be any sequels probably, well,
I guess it's sort of It's sort of an interesting
philosophical thing to think about. Like, you know, there are

(30:00):
matter particles, and those matter because that's what they make
stuff out of. But the force particles, you know, they
seem to only be there so that the matter particles
can talk to each other, and so like are they
there just to make the other ones interact? Or are
they they because they have to be there, or are
they're there by coincidence? It is an interesting philosophical question.

(30:20):
You know, we observe these things in the universe. That
doesn't answer the question of why they are there. What
we can do is think about, like what other possible
universes could you put together, and then think about why
we have this one, and we do see these amazing
mathematical symmetries that tell us that the force particles really
do complement the matter particles in this way, that they

(30:41):
preserve these internal mathematical symmetries. But you know, you can
also have other kinds of universe, So we can imagine
other kinds of universes that do follow their own self
consistent laws, you know, like universes with just photons in them,
universes with just luons in them. Right, you can imagine
those universes. They could exist. You can write down the
equations for them on paper, you can think about them

(31:01):
in your mind. You can do computer simulations. That doesn't
tell you why we have quirks. So much of what
we do in particle physics is just observation. We see
this out here in the universe. We try to describe
it mathematically. We don't know why this universe and not
another universe. We just don't know. Just describing what you see,
we are we describing what we see. We're trying to

(31:21):
boil it down to as few rules as possible to
describe all the complexity, and then we're trying to look
at those rules and say, hey, does this make sense?
Could have been different? Why is it this way not
another way? Mostly we're still pretty clueless about the answers
to those questions. So many things about the particles that
just don't make any sense and don't seem to have
any reason at all. You know, why are there three
kinds of electrons? We have no idea, all sorts of

(31:43):
interesting questions, all right, Well that what seems to be
observed is that matter particles don't interact with each other.
They do it through force particles. And so the question
is what the force particles interact with? Can they interact
with themselves like the photon? Can the photon interact with itself?
So again not directly, right, A photon only interact with
particles that have electric charge. So the photon can interact

(32:05):
with the electron, or the muon or any of the quarks.
It can also interact with the w boson, which is
not a matter particle. The rule for the photon is
that it only interacts directly with particles that have electric charge.
Particles like the z and the neutrino it cannot see,
it cannot interact with them. And interestingly, the photon itself
doesn't have electric charge. It's neutral, so the photon cannot

(32:28):
directly bump into another photon. Well, okay, so you're saying
that a photon can't interact with it itself. Can any particle,
Can any force particle interact with itself? Or can any
particle in general interact with itself? Actually, yes, some of
them can. Like a gluon interacts only with particles that
have strong charge color, right, like the quarks, for example,

(32:48):
and not the electrons. But the gluons themselves have color,
so gluons can interact with themselves. Two gluons who find
each other in the universe can bounce directly off each
other without using some other intermediate particle. Wait, they can,
like they can bounce off, but they don't use an
intermediary to bounce off. They can just bounce off. Gluons
can talk directly to each other. And that's one of

(33:09):
the reasons why the strong force is so strong and
so weird and so much of a pain in the
butt to do any calculations with, because gluons just can't
stop talking to each other. You know, quirks are constantly
generating gluons, and those gluons talk to each other and
the other quirks, and it's a huge tangled mess. Photons
are much easier because once you make them, they don't
talk to each other. They can fly along inside each
other and hardly interfere with each other. So gluons are

(33:32):
very chatty and that's kind of a pain. Are you
saying they're very sticky and that's the problem. They are
indeed very sticky. Absolutely, Are you sure there's no like
hidden particle that they're using to intert react with it themselves,
Like isn't that weird that? Like electrons can interact with electrons,
but gluons can interact with glue ups. It is weird,
And the mathematics you need to describe gluons becomes very

(33:55):
different from the mathematics you need to describe photons. And
W's disease. And that's another thing that makes a strong
force so weird and so powerful. It's very different kind
of particle. Another example is the Higgs boson. The Higgs
boson can also interact directly with itself, like Higgs boson
flying through space can bounce into another Higgs boson, or

(34:16):
it can radiate the Higgs boson. It can like pop
off one of itself. WHOA. But then, so what's the
difference between the higgs boson and like the electron or
the photon that ignores itself. Well, the rule is the
photon can only interact with particles that have electric charge,
because that's the photon's job is to preserve electric charge
in the universe. Higgs boson interacts with anything that feels

(34:37):
the weak force, and that includes the higgs boson itself.
The Higgs boson has this weird ability to talk to itself,
and again this is not something where we understand why
it is this way. But if it wasn't this way,
the higgs boson couldn't do its job. We talked to
the podcast about the higgs boson and its relationship to
Mexican hats. How it has this weird vacuum energy that

(34:57):
gives it the power to apply mass two particles, and
that comes partially from its interaction with itself. That's what
makes the higgs boson weird, and just the right way
then it can give mass to these particles. So it's
again not something we totally understand. So I guess you're saying,
as far as we know, the photon can't interact with itself,
at least directly, and so that kind of answers the

(35:17):
question of the episode, right, like, can't interact with itself directly? Yeah, directly,
Although you know, how we organize these things in our
minds doesn't necessarily determine what happens out there in the universe.
We have this strategy of let's make the simplest possible
basic ideas and then build everything out of it, like
the way you might describe the universe in terms of
legos and say I only need these lego pieces to

(35:39):
describe anything I can build out of legos. That doesn't
necessarily limit what you can make out of legos, and
it would be like artificial to say, what can I
make out of only these pieces nobody really cares right
with out there in the universe is all sorts of
crazy combinations of those pieces. So while it's true that
in our model to photons can't bump against each other
directly or definitely ways for photons to interact indirectly, and

(36:02):
we see that in the universe, but I guess, just
to be clear, like if I take a flashlight and
I crossed the beam with another flashlights beam, like nothing
happens zero. Well, two photons don't touch each other directly,
but they do have ways passing information against each other,
so effectively photons can interact. Again, not directly. They have
to like use an intermediary like other electrons or other particles.

(36:25):
But in the same way that my electrons can't interact
with your electrons directly, they do it via photons. My
photons can't interact with your photons directly. We have to
do it via electrons. But does that mean that I
can just pile photons on top of each other? Can
photons just be like in the two photons, Can they
be in the same place at the same time? Photons

(36:45):
actually can because they don't follow the same rules as electrons.
They have different spin. They're integer spin, which means they
are bosons, and quantum mechanics says that matter particles for
meons cannot be in the same state at the same time.
But no rules like that ex us for bosons. So
you can pile as many bosons as you want on
top of each other. And that's why, for example, we've
been able to do things like make Bose Einstein condensates,

(37:08):
which is a bunch of bosons on top of each other,
have the same wave function macroscopically act like a quantum object.
You can do the same thing with photons. Can have
as many photons as you want in the same state.
That's why I like lasers work. For example, m M yeah,
I hear. You can stick a bunch of bozons two
in a small cart. They do that in some particle collider.

(37:31):
The circuses particle collider does feel like a circus subtimes.
It is a ring, right, it's a ring. It's a
three ring circus out there in Tineva. We do our
best to keep the energy high. So you're saying that
photons cannot interact with themselves directly. What does that mean?
Does that mean they can interact indirectly? Yes, they can
interact indirectly. That the process is a little bit different

(37:52):
than electrons interacting. Like when electrons come by, one of
them can just radiate a photon which is absorbed by
the other electron and go on. It's b this, right,
doesn't cost anything but energy to radiate a photon. Now
imagine the case with photons. Two photons are approaching each other,
can one of them just radiate an electron which is
then absorbed by the other one. Can't actually do that
because that would violate conservation of electric charge. Photon can't

(38:15):
just create an electron out of nothing. In order to
interact without other electron has to do something slightly different.
It has to die yet. Wait, the light has to die. Yeah,
the light has to die in order for it to
interact with the other photon. It has to convert into
an electron and a positron. So the photon doesn't just
like emit an electron which is then absorbed by the

(38:35):
other photon. It converts into a new pair of particles,
an electron and oppositron, and then those guys can interact
with the second photon, can they or does the other
photon also have to turn into a pair of electron
and an anti electron, you know that electron oppositron pair.
They can interact directly with a photon because photons can
interact with charged particles, and so if you have a

(38:57):
photon coming in, it could convert into this pair, one
of which or both of which can interact then with
that photon, and so you can deflect that other photon
with the first photon. But the first photon doesn't just
like emit something go on its way, it has to
kill itself as to transform into an E plus e
minus pair. Okay, so let me see if I'm understanding

(39:17):
the picture. You have two photons heading towards each other, right,
Darth Vader is swinging his lightsaber. Luke Skywalker is you know,
moving to Perry and one of the photons turns into
an electron anti electron pair, and then those somehow deflect
the other photon that's still alive. Is that what you're saying,
like it can actually bump it. That's exactly what happens,

(39:40):
because the electron impositron can interact with the photon. What
they can absorb the photon, or they can deflect the photon.
All sorts of things can happen there. Now, this dependent
on the first photon doing that split splitting off into
a pair of electron anti electron particles. Or is this
like a quantum mechanical thing where like a photon is

(40:00):
always kind of splitting into a pair of these particles
all the time, but with a certain you know, probability. Yes, exactly.
A photon isn't just a little packet of energy in
the photon fields flying through space. It's constantly creating e
plus e minus pairs and then going back to being
a photon, and sometimes it creates e plus and minus pairs,
and those things really their own photons, which create more

(40:22):
e plus dem mondus pairs, which then collapse back. So
it's just like buzzing swarm of particles all the time.
So what happens when two photons come near each other
is that sometimes they pass right through each other and
ignore each other. Sometimes one of the photons will interact
with one of these e plus e midus pairs that
briefly exists. So it's sort of probabilistic what happens when
two photons come near each other. But the way that

(40:44):
they can interact is through the creation of this matter
antimatter pair. Momentarily, wait, what like sometimes that photon will
bump into another photon and sometimes not, or does it
always happen, but just a little bit like is it
quantum in that way? Or just want to photon feel
a little bit of force or does it only sometimes
feel a force? Well, there's an infinite number of possibilities,

(41:07):
because it's an infinite number of ways that a photon
can split into these pairs, which can then split into
the pairs. And so technically what happens when a photon
passes to another photon, It has an infinite number of possibilities,
and so then if you measure that photon, then you're
gonna get one of those possibilities, and in principle, one
of those possibilities is zero deflection, though in practice actually

(41:30):
measuring zero deflection is probably impossible because you're measuring things
with physical systems, and so you're never going to get
the photon at exactly the angle that it came in at.
Mm hmm. I see you're saying, there's always some sort
of interaction, but it's quantum mechanical, so there's sort of
a probability range of things that can happen, like if
I shoot a photon and another photon, it is going

(41:51):
to bump into each other through these split of the
particle antiparticle pair um. But what actually happens is sort
of probabilistic, like it can be the did a little
bit or a lot, or maybe not at all exactly,
and sometimes crazy things happen, like sometimes the two photons
come together, they both create the E plus E minus pair.
To those that annihilate and like destroy each other and

(42:12):
you end up with just an E plus E minus
pair which comes out. So it's like two photons come
together and then an electron and positron come out, So
it's like light gets converted into matter. Wait what so
if I collide to photons, I'm going to get some
bits of matter out of it. Sometimes. Yeah, don't those
two things annihilate each other also instantaneously? Well, you know,
this possibility for lots of different things to happen. But

(42:33):
if they've come in opposing each other and then the
electron and positron fly out the other direction, that they're
not likely to then annihilate each other. But yeah, that's
also a possibility. WHOA. So, like, if I point my
flashlight at another flashlight, stuff is happening, Like stuff can happen.
The light is going to bump into the other light.
And also I could be creating matter out of my flashlights. Yeah,

(42:55):
you are creating matter and antimatter if you cross the stream,
So be careful out there, folks. Yeah, it sounds kind
of dangerous. Little did I know? I could have ended
the universe as a kid crossing some flash lights together.
The other thing to understand is that you know, we
build up this picture of how particles interact using these
basic like tinker toys. You know, this one can talk

(43:16):
to this one, and then you can change those things
together to make more complex interaction. The more pieces of
the chain you need to use, the less likely it
is for things to happen, because it's like two quantum
mechanical things have to happen, both of which are not
that likely. So particles interacting directly is more likely than
particles interacting indirectly. If you have to have multiple steps
in your chain, it's less and less likely. So light

(43:39):
by light scattering, for example, is less likely than light
scattering off of electrons because that's more direct. All right,
So it sounds like the answer is actually a little
bit complicated, like everything in particle physics, and so let's
get into how we have actually observed this in experiments
and seeing light bump into other kinds of lights. Get

(44:00):
into that, but first let's take another quick break. All right,
we're talking about the question of whether photons can bump
into each other. Like if I point a flashlight and

(44:21):
across its being with another flash line, what's gonna happen?
Is it just gonna keep going, or is it gonna
bump into each other? And it sound like that, like
the answer is they're gonna bump into each other, like
not directly, like the photons can interact with the other photons,
but they kind of do through these other quantum mechanical possibilities. Exactly.
Everything in your body is a constant swarm of particles

(44:42):
turning into other particles, and so if you want to
interact with something else, you've got sort of lots of
options being presented simultaneously. So the fact that photons don't
interact directly with other photons is not really limitation, because
they can talk to each other via electrons or via
other charged particles. Yeah, I'm not feeling quite myself today.
Is it because of my qualty mechanical nature or maybe

(45:04):
just the fact that didn't sleep enough last night? Well
I thought you said everybody always gets the same jorhe Yeah,
and sometimes that whorrie sleepy and sometimes less sleepy, but
it's still the same whor Hey, maybe we need to
put you in the particle beam and charge you up
a little bit. Yeah, it's my answer everything. That's what
I need a sun time bed. I feel like you're
telling me that if I take a flashlight and I
crossed its beam with another flashlight, they're going to interact

(45:26):
with each other. Like the light beam is going to
hit the other light beam and mater can come out
or light's gonna get scattered. But that's kind of not
my experience, you know. I feel like if you point
to flash at each other, like the beams just go
through each other. Yeah, mostly that's not your experience because
it's pretty rare because it has to have two steps
to happen. It's less likely than particles interacting directly. It's

(45:48):
also very strongly a function of the energy. The higher
energy the photons, the more likely this is to happen.
So photons in the visible spectrum don't actually have that
much energy, and so it's harder for them to create
eat these E plus e minus pairs because electrons have mass,
and so it's costs more of their energy to make
the E plus e minus pairs, so it's less likely
for them to happen. So if you want to see

(46:09):
this happen, you need really high energy photons. That's where
it's more likely for photons to bounce off each other. Oh,
I see, so you're saying, when I crossed my flashlight beams,
they are mostly going through each other, mostly ignoring each other.
But they are maybe in a very low scale, like
very improbable. There are little photons here and there that
are scattering with each other or creating matter and antimatter,

(46:31):
almost certainly, because they are a huge number with a photon.
So even if the probabilities are tiny, one or two
photons are probably doing something crazy in those beams. You
won't notice it because it's such a tiny fraction and
it's impossible, and they're drowned out by the other photons.
But almost certainly, some of those photons are dancing together.
That's pretty cool. I means I can make matter and antimatter,
like in my house. I just take two flashlights and

(46:54):
cross the beams. Yeah, and you're making positrons momentarily. And
you're saying, like, the higher the energy, So if I
X ray flashlights than that would they would interact more? Yeah,
X rays would interact more. And this is something we
have actually done. We have studied this. We have created
matter just from colliding light that in order to do it,
we need higher energy beams of light than even X

(47:15):
rays can provide. Yeah, these are like real experiments you've
done in colliders, So tell us about this. So, first
of all, how do you make two light beams into matter?
So your first thought might be like, let's take two
lasers and shoot the match each other and see what happens, right,
or across them at least, Yeah, or two lightsabers, light sabers,
that would be even cooler. Yeah, that's the closest thing
we can do to lightsabers. Right. The issue is that

(47:37):
while lasers are really good at making coherent sources of
monochromatic light, you know, photons all with the same phase
and all with the same wavelength, they're not actually great
at making very high energy photons, like you can have
an intense beam. We got lots of photons per second
from lasers, but you can't make photons with a lot
of energy per photon. Because his limitations on the cavity

(47:59):
and how you can actually make lazing happen, which requires
reflections and residences. Even X ray lasers are hard to do.
We need things like well above X rays, well above
gamma rays, like super high energy photons. So the way
we do that is not by creating light sources at all,
but by going to our colliders and using the photons
radiated from the other particles that were smashing together. So

(48:21):
and to make high energy light you use colliders. But
isn't it doesn't get scattered all over the place, Like
isn't it hard to like harness that or aim those
photons at another source of photons. It is tricky, and
we don't actually create photons and our colliders. You know,
if the l C, for example, we're colliding protons, right,
but protons have electric charge, which means that they're constantly

(48:43):
radiating photons, especially when they're flying really fast and bending.
So protons and the l A C for example, is
surrounded by a swarm of photons which have really high energy.
And to get even higher energy, which you need is
not a proton which just has one electric charge. You
need something with even more electric charge because it will

(49:03):
generate higher energy and higher number of photons. So for that,
we don't collide protons. We collide gold or lead nuclei.
Like you take gold, you strip off all of the electrons.
So now you have something with like a very very
strong positive charge and you put that in the collider
instead of protons, and you swing those around and they

(49:23):
generate huge numbers of photons which can then smash into
each other, meaning they glow like the the ring glows.
But then how do you, like, how do you focus
these so that they, you know, collide with another set
of photons. Yes, you can't focus them at all. We
do this anyway because we're interested in collisions of heavy
nuclei for other things like park gluon plasma, and we're

(49:46):
gonna do an episode about that soon. So we already
have this program to put gold in the collider accelerated
and smash it into other gold particles, because that's really
cool and fun to do. But sometimes the gold particles
miss each other. So say, for example, you have the
gold particles swinging around the collider and they don't actually
smash into each other. They miss. They call this an
ultra peripheral interaction. As they pass by each other because

(50:09):
both of them are surrounded by these glowing swarms of photons.
Then those photons smash into each other. So like two
gold atoms that do a near miss, then their photon
swarms will bang into each other. And that's how you
study photon photon collisions at very high energy mm you
actually like miss the gold particles and you're hoping that

(50:31):
they're they're glow their relative respective glow then collides. Yeah, exactly.
It's like you have two celebrities moving through a party
and their entourages smash into each other get into a fight. Yeah,
what always seems to happen, right, exactly. That makes the
most exciting videos the next day anyway, And so remember
we can't like aim these gold particles very precisely. It's
just that sometimes we miss and then we don't get

(50:53):
a gold gold collision. But hey, we can look at
that and see if we saw a photon photon collision instead.
So it's like the accident the mess ups from the
gold gold physics gives us interesting photon photon physics, and
you can tell that it was two photons crashing into
each other. It's a big mess and it's really hard
to analyze, but sometimes they do. And in fact, they've

(51:13):
seen electrons fly out, like they've seen these gold atoms
miss each other and then pairs of electrons and positrons
fly out, and they've analyzed it and they're convinced that
this is due to the photons smashing into each other
and creating matter. Wow. Cool, Yeah, because that's the only
thing that could explain where these electron pair came from exactly.

(51:33):
It also has to do with the angles, like sometimes
you get electrons just flying out randomly, and so you
could really convince yourself that this is due to the
process that you think it is, Like you understand the
quantum mechanics of it. You calculate and say, what are
the probabilities for the electrons to fly at at this
angle or that angle, and you measure a bunch of
them and you see them at the angles you expect,
and then you can convince yourself that you haven't been fooled.

(51:55):
So this is an experiment. This is something we've just
done last year in one the Star collaboration did this,
not the Large Hadron Collider but at Rick and Brookhaven.
Rick is r h i C. It stands for the
Relativistic Heavy Ion Collider and they specialize in gold collisions
and all sorts of other crazy stuff. Now, I guess
the question is do they actually have to use gold

(52:16):
or is this just how they roll? You don't have
to use gold. It's just sort of awesome. It's funny though.
At the led C on the European side, they tend
to use lead, so it's gold in the American side
and lead on the European side. And you know sometimes
you smash lead together and gold comes out. You can
make gold from lead at the collider, though it's not economical.

(52:36):
That sounds very American, like, you know, the Germans are like, no,
let's use lead, of course, that's more practical, and Americans
are like, whatever, it's use gold, you know. You know,
I think Rick is on Long Island, and you know,
maybe they like their glam. You know, they like their
blaying out there. What are you saying about Long Island
or I think I just said it. You know, they
like things shiny, and hey, who doesn't. I'm all into

(52:58):
shiny stuff. I think you're saying that's how Rick rolls.
I think we all just got Rick rolled. I'm never
gonna let you down. But anyway, at the l a C.
They do the same kinds of studies where instead they
use lead ions and they see interesting things. They've seen
light by light collisions where you get two photons coming
out at weird angles. So at Rick they've seen two

(53:19):
photons turned into two electrons. And at Atlas, the experiment
I work on at the l A C. They've seen
photons bounce off each other, deflect each other, and go
out at weird angles. WHOA, yeah, because I guess. So
you had these lead particles miss each other and you
saw light coming off and weird like strange angles. Yeah,

(53:40):
I guess right. And but they didn't actually bump with
each other. They turned into an electron anti electron pair,
and then those maybe bumped into each other and then
created photons that sped off in weird directions exactly. And
we can only explain those weird directions using that description
you just gave, which is photons interacting with each other

(54:00):
via this weird box of electrons and positron. So that's
pretty cool because it's a rare process. It's hard to reproduce.
It's a really good test of like do we actually
understand the quantum mechanics, And it's something that was predicted,
you know, decades and decades ago physicists like in the thirties,
we're thinking about this, they're like, oh, is this possible?
I think it might be possible. It would be really

(54:20):
hard to do, and it's one of these like open
questions that stood for decades is this really happening out
there in nature? The amazing thing about the standard model
is that it seems like an ugly clue sometimes, like
there's so many things we don't understand, and yet it
works so well. Every time we go to check it
on the details, it's exactly right. It really nails it
down to the decimal places, all right. So that means

(54:43):
that you've done that experiment. You've shown to light beams
at each other, and you see that light does collide
with itself. Right, Although we missed an amazing opportunity. We
don't have microphones in the colliders, so we can't tell
what sound it made when those two photons matched into
each other. Was like or like a, I'm like, what
sound do lightsabers really me? I can't know you're joking about?

(55:05):
Would light actually makes sound? No, it all happens in
the vacuum, so it wouldn't make sound. But that would
be awesome. Oh jeez, Daniel, that's the cardinal sin of
Star Wars is the sound of explosions in space. You're
trying to tell people that sounds happening at the large
Fathroom collider Science disinformation right here on the podcast. But

(55:27):
you know, there could have been surprises. It could be
that we didn't see it, or that the photons came
out of even weirder angles, which would mean that maybe
the photons interact in different ways from the way we expect.
You know, maybe there's some other particle that appears that
let's photons talk to each other, like the axion particle,
or something else weird and new that we don't know
if it's out there. That's one of these reasons that

(55:49):
we do these really high precision cross checks of these
little details of particle physics, because it could be in
one of those details we find something weird, and that
unraveling that thread is exactly how we create a whole
new understanding of the universe. You know, That's how we
discovered quantum mechanics, understanding why the photo electric effect wasn't
exactly as we expected it to. So we never know

(56:10):
which little cross check is going to reveal the right
thread to pull on, or the right light saber to
turn on that makes just the right sound. I guess
it's kind of interesting to think now that photons can
interact with each other, although not directly, Does that mean
the I have a question of whether all particles in
Does that mean that all particles can interact with themselves

(56:30):
just indirectly like it's everything is fair game in the universe. Yes,
everything is fair game in the universe. Photons can interact
with themselves in directly, right, they can generate E plus
e minus pairs, which can then interact back with them.
Good neutrinos, like neutrinos interact with regular electromagetic things through
these quantum transformations. Absolutely, neutrino feels the weak force, and

(56:52):
you can generate a W particle, right, and that W
particle can interact with electrons, and that's exactly how the
neutrino feels the rest of the universe, And neutrino could
indirectly interact with corks in the same way or other stuff.
The only thing we don't know about is dark matter.
Is dark matter of particle which forces? Does it feel?
Does it feel any forces at all other than gravity?

(57:15):
Dark matter might be out there totally inert, unable to
interact with anything except for gravity. As far as we know,
we don't know if it's fair game or not, but
it could be. It could be just be super rare.
Maybe it could just be super rare. There could be
some other kind of force that dark matter can used
to interact with itself, Like the whole universe could be
split into different sectors. This whole group of particles that
can talk to each other with forces, the ones we

(57:37):
know and love, and another separate sector that can only
talk to each other and can't interact with us except
through gravity. That's possible. What about menta chlorins? Can they
interact with themselves only if they make sound? Right? Do
they scream in space? Maybe that's me. That's the sounded
light savers actually make when they crashing to each other.
It's it's a billion miny chlorians screaming at the same time.
Oh wow, Now that I understand the true cost of

(57:59):
using the force, I will be more careful about it. Yeah,
it's pretty tragic. Actually, Why that put the whole different
spin on Star Wars, isn't it? It really does? Yeah?
I wonder is any of this cannon anything? Yeah, because
your physicist right right, Absolutely, this is all official now, folks. Yeah, yeah,
But the question is can meta Glorian's feel not just

(58:20):
forces but feelings. Well, we'll have to have one on
the podcast as a guest and ask it yeah, or
George Lucas move whichever one will come first. All right, George,
give us a call. All right? Well again an interesting
look into how the universe surprises you. You You know, sometimes
you think that two things can interact with each other,
but through quantum mechanical magic, they sort of do. And

(58:41):
it's almost the same thing as if they were interacting
with each other. Yeah, and the universe out there is
a crazy, swarming, quantum mechanical and nightmare of complexity. But
somehow we can pull together these beautiful, simple stories about
particles interacting with each other and use those as lego
bricks to describe all the amazing complex to be out there,
even gold gold near misses at very high energies. It's

(59:04):
incredible what physics has been able to do. So I
think this is the part where we thank people for
joining us, and this is the part where we join
off our lightsabers. Thanks for joining us, See you next time.

(59:25):
Thanks for listening, and remember that Daniel and Jorge explained
the universe is a production of I Heart Radio. For
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