Could some particles have tiny electric charges?

Daniel and Jorge wonder about why particles have charge, and whether particles could exist with tiny electrical charge.

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Episode Transcript

Speaker 1 (00:08):
Hey, Daniel, you have an electric car, right, Yeah, I
drive a Nissan Leaf these days, and last time I
had a Chevy bolt, so you bolted from the bolt
and to turn over a new leaf, I left it behind. Now,
how much does it cost to charge up with one
of those electric cars? Well, that's kind of a charged question,
but usually less than ten dollars. Actually, oh wow, you

(00:30):
only charge you ten bucks to charge your car? You
go to one of those charging stations. No, I usually
charge it at home where I'm in charge. You can
charge ten bucks to charge your car where you're in charge,
and charge it on my credit card. You should charge them.
I'm positive that won't work. Hi'm for Hammo cartoonists and

(01:01):
the creator of PhD comics. Hi, I'm Daniel. I'm a
particle physicist and a professor at UC Irvine, and I
actually do sell charges back to the electric company. Nice
solar panels. I do have solar panels, but unfortunately the
electrons I produced don't end up in my car. They
have to go back to the company and then I
buy fresh electrons from them. I don't have one of

(01:23):
those massive home batteries yet. Yeah, you don't want old electrons?
The cool kind of stale, right. The thing, I don't know.
I've had some really vintage electrons created during the Big Bang,
and they were pretty tasty. Aren't all electrons created in
the Big Bang? Some of them might have been, but
also electrons are being created all the time, and so

(01:44):
some electrons might be very, very fresh, and some of
them might have had many, many lives before you. Do
you have like an electron summerlier that tells you the
vintage of electrons? And how do you taste electrons? Do
you just stick your tongue in the electrical outlet or what?
What advice are we giving the public here? That's a
shocking suggestion, Jorge, sticking your tongue in the outlet. I'm

(02:06):
positive that's not a good idea. But it is an
interesting philosophical question of whether you could taste the age
of an electron or even somehow tell its age. We
don't think so, because they're quantum particles, so they're all identical.
Every electron is the same as every other electron, and
so there's no way to tell if an electron is
fourteen billion years old or fourteen billiseconds old. Yeah, it

(02:29):
would be kind of rude. To ask anyways, But welcome
to our podcast Daniel and Jorge Explain the Universe, a
production of iHeartRadio, in which we try to be positive
about all the charged questions there are about the age
of the universe, how big it's been getting, and what
it's been eating. We like to think about everything involved
in understanding the universe, from the deep nature of the

(02:50):
fabric of space itself, all the way up to the
shape and size of the universe, and everything fascinating in between.
We want to tickle the curiosity that we know is
inside your mind and make you wonder at this marvelous universe.
Why is it this way and not some other way.
That's right because it is an electrifying universe, full of
amazing things happening in it, things coming together, things being

(03:12):
pushed apart, And we like to zap all of that
knowledge into your brain so that you get a small buzz.
And the electricity is one of the oldest topics that
humans have been thinking about. After all, it's obviously out
there in the world. You don't need a superconducting super
collider in order to study electricity and magnetism. You just

(03:32):
need to watch a rainstorm and look at lightning or
zap yourself as you walk across a carpet. So humans
have been aware of this strange phenomena of electricity for
a long long time. And wait, wait, wait, wait, they
had electricity back in the steam age. How did they
power their light bulbs? You know, almost all electrical generations
still uses steam. It's incredible how versatile the steam engine

(03:56):
really is. That what the electrons are always wet. I
don't know what's going on with the plumbing in your
house that your electrons are wet. But that does not
sound like a good combination. You know, not so much
wet as steamy. I get steamy electron. Well, electricity has
been something that's been tickling the minds of humans and

(04:17):
physicists and proto physicists for a long long time, you know,
watching a rainstorm and wondering like wow, what is that crazy?
Zapping all the way up to Benjamin Franklin trying to understand,
like what's going on. It's been something we've been working
on for a long time. We've made a lot of progress,
and yet there's still really basic questions about how it works.
You know, the origin of the word electricity, Like I

(04:39):
wonder when humans started to think of electricity as electricity
because I imagine, you know, for millions of years we
saw lightning, but we didn't think it was anything different
other than light or you know, strips of light. Yeah.
I think there's a long history of crazy ideas to
explain what we see out there, and it wasn't until
a few hundred years ago that people trying to be
sort of systematic about it and come up with like

(05:00):
something you could describe as a theory to explain what
was going on. You know, before that we had basically
mythology zoos throwing lightning bolts and this kind of stuff.
I see, so Zoos was the first electric company. I
wonder if zeus charge for lightning bolts, right, I don't know.
They are pretty spectacular to look at. But anyways, electricity
is one of those old subjects that humans have been

(05:22):
thinking about and wondering about, and apparently it's still something
that we wonder about today. That's right. We have graduated
from thinking about electricity as the product of an angry
god to thinking about it as a strange, invisible fluid
that flows through matter, to modern ideas that electricity is
carried by tiny, little discrete charged particles, each of which

(05:43):
carry this strange quantum label of electric charge. It doesn't
sound like we've progressed much there from saying electricity is
something that God throws down from the sky to something
that little tiny particles have. Well, maybe emotionally we've progressed.
You know, we don't think electrons are angry as Zeus was.
So you know, maybe it's just a calmer theory of
the universe, or maybe you just don't know if your

(06:06):
electrons are mad at you. It could be, especially if
you ask them their age. But that means that all
electrons in the universe would have to be mad at you.
That's like a whole universe filled with screaming, mad electrons.
That's kind of terrifying. Maybe it's only the ones that
you use for your car. They don't like where you're going.
The ones we put to work, Yeah, exactly, just because

(06:27):
you don't want to walk, Daniel, even if I'm walking,
that uses electrons. Right, there's electrons in everything. Anytime you
do some work, that's going to be electrons involved. So
that's why the electron labor union is so powerful. I
wonder how they hold together. But there is a lot
we don't understand about the universe. And it's kind of
surprising to think about the idea that there are things
we don't understand about electricity. I feel like the electricity

(06:49):
is something that we use every day. I mean, we're
using it right now to record this, and also everyone
is using this to listen to this podcast, and yet
there are things we still don't know about it. Yeah. Well,
you don't actually have to understand the universe in order
to use it, right. You took advantage of gravity holding
you under the earth surface long before anybody had any
understanding of gravity, and even four hundreds of years when

(07:10):
we had a pretty deep misunderstanding of gravity. So it's
just sort of part of the process of science to
develop these descriptions of what we see, try to explain them,
and then refine them as time goes on. There will
always be open questions things we don't understand. What I
hope that listeners appreciate is that some of these questions,
some of these things we still don't understand, are really

(07:32):
pretty basic and have to do fundamentally with the nature
of electricity. What is it anyway? Yeah, And so today
on the program, we'll be tackling Could there be particles
with different electric charges? That's right. We know about a
few different kinds of particles with a few different kinds

(07:53):
of electric charges. But the curious person always wonders, like, well,
why is that? It? Is there more on the list?
Is the universe capable of doing other things? And it
just isn't? Or are there other particles out there with
really weird electric charges? Yeah? I guess when we say
different electric charges, we mean different charges than the electron, right, Like,
could there be a particle out there with a charge

(08:15):
that's not the same as the electron? Yeah, we actually
do have a few examples of that, right, Like quarks
have strange charges like two thirds and minus one third,
and the electron is this charge negative one. But it's
interesting to think about, like could there be particle with
charges of like one millionth or one billionth or like
pi or other strange numbers. There seems to be like

(08:37):
a pattern to the electric charges, or they seem to
prefer these sort of discrete units, But we don't really
understand why that is. Oh, I mean we're asking today
whether you can have a particle with like point zero
zero zero one of the charge of the electron. Yeah,
is that possible to do those particles exist? What would
it mean for the universe if they did or they didn't?

(08:58):
But you said that, we know about particles that have
one third of the charge of the electron. That's a
quart or some of the courts. That's right, Some of
the quarks have charged one third, and some of the
quirks have charged two third. Basically, every particle we've ever
seen either has zero charge or some multiple of one
third of the electrons charge. Nicee. So today we're asking
if you can go smaller than that? Could there be
particles with less than a third of the electron charge? Yeah?

(09:20):
One fifth, one ninth, one billionth even are there limits?
Is there a rule that prevents a particle from having
some super tiny electric charge but not zero? And I
assume that's not a question with a small answer, and
maybe even answer that will shock us. That's right, it's
a small question with big consequences for the philosophy of
electric charges. Was usual. We were wondering how many people

(09:43):
out there had thought about this question or wondered whether
particles can have tiny electric charges. Thank you very much
to our list of volunteers who answer these questions for
everybody else's enjoyment and education. If you would like to
contribute to your voice to this segment, please don't be shy.
We don't describe. We let everybody participate. Right to me
to questions at Daniel and Jorge dot com. So think

(10:05):
about it for a second. Have you heard or think
that electron can have tiny electric charges? Here's what people
had to say. Yep, why not. I will accept particles
of any coolure. I'm sure there's no discriminating against fractional
electric charges. I would guess that particles with fractional electrical

(10:26):
charges would be possible, given that in chemistry they have certeometry,
and so it maybe does not real out the fact
that this could be the same for sometime a particles.
I have heard health spin as a quantum property, but
never health electrical charge. So I will say no, But

(10:48):
since you are asking it, maybe yes, my guess would
be probably. I'm sure there's a law physics it says no,
you have to be a plus or minus or no charge.
But I don't see why you couldn't have a fractional charge.
I suppose, so, yeah, I think that is the case. Today.
I think we have quarks with like one third charge

(11:11):
or two thirds charge, And I think the actual charge
of an electron is some crazy fractional number and we've
just chosen to assign it the value of one for convenience.
So yeah, I think that's possible. Well, isn't charges caused
by particles like electrons considered particles? Am I getting that wrong?

(11:31):
I'm guessing no. Well, I'm going to walk into the
obvious trap here and say that I think no particles
cannot have tiny fractional electric charges. I think that an
electric charge is either present, positive or negative or absent,
and is an indivisible quality. I'm hoping, of course, that,

(11:53):
true to the nature of this podcast, this obvious trap
will turn out by the end of the podcast to
have been an a double bluff and vindicate mind ignorance.
All right, A lot of people said yes, because, of course,
maybe we asked the question wrong. I think that most
people don't even imagine the existence of like particles with

(12:15):
one millions of the electric charge. Yeah, that's not something
nice they open night usually wondering about. I mean, maybe
one thousands, but not a million. There's some limit there.
You're like, one thousands is reasonable. One millions. This crazy. Yeah, yes,
that is what I think about at night. Well, you know,

(12:35):
a way to explore the universe is just to try
to be creative, to think about, like what assumptions are
we making because we've only seen certain examples, what conclusions
are we drawing because we've only seen a subset of
what the universe can actually do. So sometimes it takes
a little bit of creativity to like break out of
the box we've been living in and wonder what could

(12:56):
be outside that box. Sometimes we don't even realize the
boxes that we are in. So I love this question
precisely because a lot of people are like, huh, that's interesting.
I never even consider that there could be other kinds
of particles with weird electric charges in them. And that's
what makes it exciting, because that's the best moment in physics,
when we realize we've been overlooking something and maybe it

(13:17):
shows us something new about the real universe out there.
I wonder if maybe what we're asking here really is like,
are there maybe particles with weird electric charges that we
didn't know how weird electric charges? Is that kind of
what we're asking, like, maybe there are things there are
particles out there which just haven't seen them or known
about them, that actually have these weird charges we just
haven't noticed. Yeah, exactly. One possibility is that there's a

(13:38):
new kind of particle out there with weird electric charges
we just haven't noticed yet. The other possibility is that
maybe some of the particles we do know don't actually
have zero electric charge, they have very very very very
small electric charges. All right, well, let's jump into this topic, Daniel.
Let's start with the basics. What is an electric charge? Well,
we don't really know. All thanks for joining us. See

(14:02):
you next time. It's fun to joke about that, because
that really is the answer. We don't actually know what
an electric charge is physically. It's part of our description
of what we see happen in the universe. So we
notice that some particles that accelerated if you put them
in an electric field, and other particles don't. Right, And

(14:26):
we even have an equation that describes it. Right. Force
is equal to charge times the field strength. So if
a particle is accelerated when you put it in an
electric field, we say that particle has charge. If a
particle ignores the electric field, we say the particle has
no charge. And the bigger the charge of the particle,
the greater the force that it feels. But it's just
sort of like our description of what we see. We

(14:48):
put this into our mathematical story about the universe. That
doesn't mean we know like what it is, right, But
it's even more confusing than that, because it's kind of like,
how do you define an electric field? Isn't an electric
field defined as how the or this change on a
particle that has charge? Yeah, exactly right. We say the
fields are generated by charged particles. We don't ever even

(15:11):
see the fields themselves, right, you can't observe a field.
The only thing you can observe is the field pushing
on particles. So if you want to get down to
the nitty gritty, what do we actually see is that
some particles push on each other, and we have this
intermediate thing we call a field, which allows particles that
are far away from each other to push on each other.
But fundamentally, we say, some particles push on each other

(15:31):
and some particles pull on each other, and the charges
in the fields. It's just sort of like our mathematical
story of what's happening there that to describe what we see.
So maybe you would define a charge more accurately. As
you know, if you have an electron here and an
electron there, they're going to push against each other, and
that push sort of depends on this thing that you

(15:52):
call a charge. Yeah, you can put a label on
every kind of particle and that label tells you how
to predict whether the particle will be pushed by another
particle or it's field equivalently, and that works, and it
works really, really really well. It works incredibly well. It's
one of the best tested theories we have in physics.
We can do pages and pages of calculations to predict

(16:14):
how electrons will push on each other and how they
will shoot photons at each other, and we can do
experiments to test those predictions, and the experiment and the
prediction agree to like eight or nine decimal places. It's
really extraordinary how accurate it is. And so you look
at that theory and you're like, hm, well, if it's
so accurate, maybe it's really describing what happens in the universe.
Maybe this thing we invented, this idea of charge, is

(16:37):
a property of the particle itself, not just part of
our story about the particle. Right, it's sort of like
mass is for gravity, Right Like, if you have two
particles out there in space, they're going to attract each
other depending on this thing about them called mass, And
that's kind of the same for charge, right Like, if
you have two particles, they're going to either attract each

(16:57):
other or repel each other by a certain amount, pending
on whether they have this thing called charge. Yes, excellent, exactly,
And in particle physics we generalize this concept of charge.
Do not just refer to electromagnetism, as you say. You
can think about gravity in terms of gravitational charges or masses,
and you can think about the strong force in terms

(17:20):
of strong nuclear charges on quarks. Those are even more
complicated because instead of having two values like plus or minus,
have three values red, green, and blue. The weak force
also has a kind of charge that we call weak hypercharge.
So in a more general sense, charge tells you whether
a particle feels a force. Like the electron has an

(17:44):
electric charge, but it has no strong nuclear charge. It
doesn't feel the strong nuclear force. A quark has both
an electric charge and a strong nuclear charge, and so
it feels both forces. So really, charge in general is
a label about saying whether or not a particle feels
that force, and it's something philosophically we like attached to

(18:05):
the particle. We say, this is a property of this particle.
The electron has the charge physically, I don't really know
what that means, like where in the electron is it.
It's just sort of this like ineffable quantum label we
attached to it. We don't really know where it comes from,
like what generates the actual charge itself? Well, I think
in quantum theory and correct me if I'm wrong. But

(18:25):
it also because it sort of has to do whether
a particle interacts with certain quantum fields or done right,
Like maybe that's another way to define it. If the
electron doesn't interact with the strong force field, then it
just doesn't have a strong charge. Yeah, I think that's
another way of saying the same thing. You can think
about all these quantum pictures of the world either in
terms of particles that are pushing on each other or

(18:48):
in terms of fields, because remember, these particles are actually
just little wiggles in quantum fields, and those fields can
sometimes talk to each other. So, for example, the electromagnetic
field for which the photon is a particle can interact
with or talk to any field that has charges. So
the electron field of which the electron is the wiggle

(19:08):
is the particle, right, that will interact with the electromagnetic field,
and so will the field of the w boson because
it has electric charge. So as you say, the fields
that interact with a certain force, we say their particles
have that charge, and the fields that don't, we say
the particles don't have that charge. So, for example, the
neutrino field, neutrinos have no electric charge. Neutrino fields and

(19:30):
electromagnetic fields totally ignore each other. Right, So then maybe
you can define charges being like whether or not auto
particle interacts with the electromagnetic field. Yeah, for the electric charge,
And in terms of like particle theory, they often talk
about it as coupling. The electric charge is the way
that the photon field couples to the electron field. How

(19:51):
those two fields sort of like let energy slide back
and forth between them. I feel like we're getting a
little steaming out there. Are we back to talking about
steamia not steaming a not safe for workway? You know,
we're just talking about connections. We're just talking about energy
sliding from one kind of feel to the other. All right, well,
what sounds like we kind of have a definition of

(20:12):
what charge is. We just don't know where it comes
from kind of right, That's the thing, like, we don't
know why some particles interact with the electropicnet feels and
why some don't. That's right. We have a very effective
description of it, but we don't know why some particles
have it, what the rules are for what charges you
are allowed to have, and where it comes from at all. Yeah,
I guess some particles just have that spark and others

(20:33):
some particles just have a positive attitude. All right, Well,
let's get into a little bit of the history of
this idea of an electric charge. Where did it come from?
How did humans start to figure this out? And then
let's get into the bigger question of whether electrons or
things with electrical charge can have tiny, almost imperceptible charges.
But first let's take a quick break or I we're

(21:05):
talking about charges, and we're charging ahead here with this topic,
talking about whether electrons or charged particles that have the
fuel electricity can have electrical charges that maybe have been
escaping our notice for thousands of years. So Daniel, maybe
step us through here a little bit on the history
of charges. When did we start noticing that some things
have electrical charge? So we certainly had noticed the properties

(21:29):
of electricity for a long long time, right, static electricity
and lightning, these are things everybody was aware of, and
until around the mid seventeen hundreds, the idea to explain
these things was dominated by concepts like effluvium or this
basically this two fluid theory of electricity and magnetism. It

(21:51):
was like this invisible fluid that flowed through objects, two
different kinds of invisible liquids flowing through objects, one positive,
one negative, that could cancel each other out right, Because
as you said, I imagine that this is something we've
noticed for maybe hundreds of thousands of years. Imagine, you know,
even caveman would get you know, static electricity in their
hair would stand up right, But for them it was

(22:13):
probably just you know, magic, or they had no way
to grant that there would be a reason for that exactly.
And the process of science is want to try and
develop like an explanation for these things. How can we
unify different phenomena that we see, the static electricity in
your hair and the lightning in the sky, Which of
these things are related and which of these are totally
different phenomena. So that's the process of physics, right sorting

(22:36):
out all the phenomena we see and trying to coalesce them,
boil them down into a few simple explanations, and try
to find the relationship between those to give, like, you know,
a single description of everything that's happening. And so this
really is an ancient process. It's a great example of
the whole process of physics of trying to coalesce many
different things down into one explanation. But I think you're

(22:57):
saying that maybe we did have sort of some idea
that it was something that flowed between things, right, Yeah,
it was sort of considered to be a liquid. We
didn't have the idea of particles yet. It wasn't until
you know, the late eighteen hundreds when J. J. Thompson
discovered the electron that we thought of it is like
isolated to a little particle. It was sort of more
similar to early concepts of heat. You know, this liquid

(23:19):
that flowed between things. And it's really fascinating because the
original idea was of two liquids, one positive and one negative,
which could flow between things, and they could cancel each
other out. It was mostly trying to explain like electrical
attraction and repulsion and that theory. You know, it sounds
right because we know that there are protons and there
are electrons, which is actually not quite right because the

(23:41):
protons don't really flow. Right. What happens with electricity in objects,
It say it's the electrons that are moving. And so
it was actually in the mid seventeen hundreds with Ben Franklin,
came up with the one fluid theory of electricity. Basically,
there's just one kind of thing that's moving around. Now
we know, of course those are electrons, and that's a

(24:02):
more accurate description of what's actually happening, but it sort
of ignores the protons and the positive charge. So it's
sort of fascinating from that point of view. Historically, I
think you're saying that maybe like our early ideas about
electricity was that it was sort of like a fluid.
I guess I'm sort of like magical fluid in a way,
and that maybe at first we thought there were positive

(24:22):
fluids negative fluids, but more actually, when you see electricity
on an everyday basis, it's usually the negative electric charges
that are flowing around exactly in immaterial it's the electrons
that are moving. The protons are usually in the crystal
and can't really move very well. The nuclei don't flow,
so it really is the electrons that are moving. And
Ben Franklin did all these experiments with cloths and glass rods,

(24:45):
and of course his famous experiments with lightning. He's one
of the first people to try to explain all these
things in terms of a single phenomena. Did he use
hundred dollars bills? Also? He was all about the Benjamin's
for sure. But then it was in the late eighteen
hundreds that J. Thompson did his experiments with cathode ray
tubes and he showed that there were these tiny little
dots of matter that carried charge with them. He showed

(25:09):
they could be deflected by electric fields. We have a
whole episode about the discovery of the electron which want
to dig into the details of that one. But it
was a really interesting moment because he showed where the
charge was. It went from being like this weird invisible
not quite magic but imperceptible fluid, to being isolated to
these little bits. There was something out there that was

(25:29):
carrying these charges. We'd like identified a little bit of matter.
It had mass and it had electric charge to it,
So that made it like concrete in a new way.
So wait, he could actually see individual electrons. How do
you see an electron? Well, he couldn't see an individual electron,
but he could see them land on a screen in
his cathode ray You know, cathode ray tube is basically
the way TVs used to work. They have a little

(25:51):
gun of electrons that would shoot at the screen, and
you would have fields that bend them, so they would
shoot at different places at the screen it would scan across.
And that's not very different from his original setup where
he had a little hot bit of metal that boiled
off electrons and then they were accelerated by a field
and then bent by another field. So what he showed
was that you could bend their path using fields, which

(26:14):
meant that they were carrying the charge, and he could
change where they landed by changing those fields. A really
clever set of experiments. Right, But I wonder if he
thought maybe there were just droplets of this fluid right,
Like he maybe didn't think of them as particles necessarily,
did he? Because the quantum idea wasn't around yet, that's right.
But he actually is the one who came up with

(26:34):
this concept that these things were all isolated on these
tiny little dots. He didn't use the word particle. He
invented this other word called the corpuscule, which he hoped
was going to take off and that we'd all be
corpuscular physicists by now. But fortunately that name was dropped
later by other people. But he definitely identified these things
as tiny little dots with mass and with charge bundled

(26:56):
together into the same physical location. It's really the first
moment where we started putting these labels on tiny dots
of matter, sort of the invention of the concept of
a particle. There. Did he call it an electron or
when did the name come into use? He definitely called
them corpuscules. The name electron came later, which I don't know.
I'd prefer the word electron two corpuscule. It's really amountable.

(27:19):
And it was Milliken a few decades later who did
his famous oil drop experiments where he showed that the
charge is discreete that you couldn't have like one and
a half charges or two point seven charges but you
could have like one, two, or three these very precise
experiments that were balancing various forces and showing that they
were integer quantities of them. So at that point we

(27:40):
knew that charge was a thing, that it was attached
to these tiny little particles, and that their charges were discrete.
You didn't have like some particles running around with one
point two seven charges and other ones with zero point
eight nine. You either had one electron or two electrons
or three electrons. You know, this is around the same
time that quantum mechanics was being developed, when we had
the understanding that light was packets of photons. You couldn't

(28:03):
have like one point two of them. So the whole
idea of discretization was sort of taking over physics. Sounds indiscreet,
but I guess my question is how did Milliken figure
this out? I mean, you're talking about the early nineteen hundreds.
How did they have experiments that can measure things down
to the one electron level? This is a really hard
experiment to do. He took little drops of oil and

(28:25):
he sprayed them out of a little sprayer, which basically
strips them of some electrons, which basically ionizes them, and
so now they have electric charge, and let them fall
through this little chamber until they reached terminal velocity, and
then he turned on electric field to try to make
them levitate, and by tweaking the electric field, he could
find exactly the right force he needed to balance the

(28:48):
downward going velocity. You could make these particles float. Essentially,
and what he noticed was needed a certain field or
like twice that field or three times that field, which
he hypothesized told him like how much each drop had
been ionized. So essentially he was measuring like how much
electric force you needed to levitate these drops, and he
noticed that it always came intoger quantities, So he wasn't

(29:11):
studying individual electrons. You couldn't see individual electrons, but he
was studying the overall electric charge of these little drops
of oil. But that sort of only works if the
each drop is the size of one electron, right, Like
if you have a whole cluster of things with electrons,
would you still notice that kind of discrete electric field. Yeah,
you can have a whole oil drop. But what he's
measuring is the ionization of that drop, like essentially, how

(29:35):
many non neutral particles are in that drop, Because that's
what's going to affect the force that the drop feels
when you put it in an electric field. So he
was noticing that you could ionize these drops by one unit,
or two units, or seven units, but not by three
point two units. Interesting. All right, well, I think that's
kind of the general history of electrons, right, And that's
where the idea of the electron took off, right as

(29:57):
a discrete thing. And then the rest is history. The
rest is history. And now we regularly produce electrons and
ar collider and study them in gory detail. In the
mid nineteen fifties, we had quantum electrodynamics, this theory of
photons and electrons as oscillating quantum fields, which is basically
the modern story of electromagnetism. All right, well, let's get

(30:19):
to our question of whether electrons or other particles can
have charges that are smaller than one third of the
charge of an electron. I guess, Daniel, why are we
asking this question? Or I guess what do we know
about charge in general? So what we know is that
electrons have charged minus one, which is just something we assigned, right,
We could have given electrons any charge. It's really just
totally arbitrary, and that protons have the opposite charge. Protons,

(30:43):
of course, are made of quarks, and those quarks have
the weirdest charges we know. They have charges like plus
or minus two thirds or plus or minus one third.
There are also particles out there neutrinos that have charged zero.
So all the fundamental particles that we know about have
charges zero one thirds, two thirds, or like the electron,

(31:04):
they have effectively charge one. These units are arbitrary, but
everything seems to have a charge that a multiple of
one third of the electric charge. That seems to be
the minimum charge out there. Of the zero, of course,
which you can consider still a multiple of one third.
There's no particles out there that we've seen that have
charged like two sevenths or fourteen ninety firsts or you know,

(31:27):
pie times the electron. I guess, just to be clear,
there's only four particles that we know about that have
electric charge. Is that true? Well, there are the four
kinds of fermions, right, electrons, neutrinos, of quarks, and down quirks.
There are also the other generations like the charm, the top,
the muon the towel. Those all have the same electric
charges as the base particles. So yeah, there are four

(31:48):
kinds of fermions, and each one has a different charge. Right,
So I guess what I mean is that we haven't
found any other particles other than these four and their
generational cousins that have electric charge, right that we The
only other particle with electric charge is the W. The
W is one of the first particles of the weak force,
and interestingly, it also has electric chart. So there's two

(32:09):
of those. There's the W plus and the W minus,
So those sub charges plus one and minus one. Those
are the only other charge particles out there. The other
particles like the Higgs boson and the photon and the
gluon and the z boson, all of those have zero
electric charge. Wait, the W particle also has electric chart,
and it's exactly the same as the electron. It's exactly

(32:31):
the same or opposite of the electron. And that's important
because the W and the electron interact with each other.
For example, a W can decay to an electron and
a neutrino, and that conserves electric charge. You start out
with charge minus one, you end up with an electron
with charge minus one and a neutrino with charge zero.
So electric chart starts at minus one ends at minus one.

(32:51):
It's conserved. That's something else really fascinating that we know
about electric charge is that it can't be created or destroyed.
It's always conserved in the universe. Now, is that a
cool incidence that the W happens to have the exact
same charges the electron? I don't think we know the
answer to that. But if it didn't have exactly the
same charges the electron, then it wouldn't be able to

(33:12):
interact with the electron. Like the W had a charge
of one point two, then it couldn't decay to an
electron and a neutrino because charge is conserved. And so
basically it would mean that it couldn't interact with our
kind of matter, and then it wouldn't participate in anything
that we knew about, And so it might exist in
the universe but not be something we could see or

(33:33):
interact with. Right, And so the fact that the W
has the same charge as the electron is what allows
it to participate in our part of the universe, and
so that's the reason we know about it. So it
might be that there are particles out there with weird
charges that don't interact in the same way as our particles,
and that's exactly what people are looking for. M I see.

(33:54):
That's I think this gets into kind of the heart
of what we're asking here today and why maybe we
may have observed other particles that have different terms. Because
I know we talked about before, how the idea that
the proton has exactly the opposite charge of an electron.
It's sort of a coincidence in the universe, and if
that was any different, we wouldn't have all those things

(34:14):
we have today like us. That's right. It's sort of
explained and sort of not explained. Right, It's not explained
in the sense that, in principle it could have been
something else. Right. It could have been that the quarks
don't have exactly one third and two thirds the charge
of the electron, so when you put them together you
get a proton that's not exactly the opposite charge of
the electron. That could work in physics, but it's explained

(34:36):
in the sense that that universe would be so different
from ours that it's sort of impossible to even imagine
what that would be like. Would be very different from
the universe we experience. So to have a universe like ours,
requires that balance. That doesn't mean we know why that
balance exists, right, So it's a really fascinating question philosophically. Yeah,
all right, Well, let's get into this question of whether

(34:58):
charges can be different than the ones from the electron,
and specifically much smaller than one third the charge of
an electron, Like maybe there are particles out there with
that kind of charge, we just haven't seen them. So
let's get into that question. But first, let's take another
quick break. All right, we're talking about charges in the universe,

(35:29):
and Daniel were saying that, you know, the electron has
a charge of negative one because that's what we gave it,
and we know that the proton, which is made out
of quarks, has an overall charge of plus one, and
the fact that they're exactly the opposite is sort of
the reason that we can't have atoms and things like that. Right,
if it was any different, what would happen If it
was any different, then you couldn't get neutral hydrogen, for example. Right,

(35:50):
there was this moment in the universe very early on,
when electrons and protons cooled down. They slowed down enough
that their mutual electrical attraction action could make them warm
neutral hydrogen, and the universe suddenly became transparent. Right, this
is the moment when the cosmic microwave background radiation was
created and flew through the universe. And neutral hydrogen is

(36:13):
essential for basically the formation of the whole universe. It's
basically what makes up the universe, neutral hydrogen. Wait, wait,
why is that important? I guess if let's say the
proton had like one point one the charge of an
electron plus one point one, you would still get hydrogen,
but the hydrogen would just have an overall charge of
plus point one, wouldn't it. Yeah, you could get hydrogen,

(36:34):
it wouldn't be neutral hydrogen. And I think that has
a lot of downstream effects for how chemistry happens and
how life is formed and everything else that we rely on.
But yeah, I'm not an expert on chemistry and biochemistry.
But you could still have a universe way with suns
and planets and stuff, couldn't you. You could have a universe.
And I imagine that fusion could still happen because fusion

(36:57):
fundamentally is really just a process between proton You don't
really need the electrons. Like inside the heart of stars,
protons are anyway ionized to you don't really have the
electrons around when you do fusion, So you can still
have fusion if protons don't have exactly the opposite charge
of electrons, so you can still have light in the universe. Right,
that's good. Remember that electromagnetism is much stronger than gravity,

(37:20):
So for gravity to take over and to tug things
together into dense objects probably requires everything to be electrically neutral.
Nothing is electrically neutral, and everything is repelling each other.
Gravity might not be able to overcome that and form
dense objects like planets and stars and ice cream. Well,
I wonder if that's true. One you could still form them,
they would just maybe be different proportions of the different elements, right,

(37:43):
Like you know, if hydrogen was like plus point one,
then maybe you could have other materials that are like
negative point eight, and then you could have you know,
two of these and one of these. Yeah, it might
be possible to still form neutral objects. But for that
to work, then the charge can't just be arbitrary. They
have to be like some rational fraction of each other.

(38:05):
You know, the proton is charged pi and the electrons
charged negative one, then no, arrangement of protons and electrons
will give you a neutral object. It's just impossible. But
if they are a rational fraction of each other, if
the proton is like five fourths or nine eighths or something,
then yeah, you can have a certain relationship. You can
make weird atoms out of eight protons and nine electrons

(38:25):
or something like that, Right, And I wonder if that
would be okay, right, Like, like we can have molecules
in our body that have an overall charge, right, we
certainly could, Like a molecule in our body can lose
an electron in one of its atoms and it would
still be a molecule. Like maybe I wonder if biology
or nature needs neutral particles. I know that a lot
of our biological processes rely on charges, right, Like our

(38:48):
entire nervous system is basically electrically charged and uses ions.
So probably things like that could function. But I think
the whole structure of the universe would be very different
if you had these different kind of chemicals. But even
this is relying on an assumption, right, It's an assuming
that you could still build something neutral so that gravity
could take over. If instead charges could have any value,

(39:09):
then there's no guarantee you could put particles together to
make things that are neutral. And I think that's one
of the deepest questions, like why are these particles rational
fractions of each other's charge one third, two thirds, five
fourths even, you know, these kinds of things instead of
zero point eight seven two or irrational numbers. Yeah, I
guess that's the main question we're asking today, is like,

(39:30):
why can't that be because as far as we know,
the particles that we do know about have these multiple
charges of each other. Right, that's kind of the idea exactly.
And so if you ask theoretical physics, like what prevents
us from having particles with charge zero point oh one
or zero point one seven nine two, or you know,
just keep going, and the answer is nothing, like there

(39:52):
is no theoretical prohibition against it. But that's mostly because
we don't really understand where charge comes from and how
these labels get us signed, and so we haven't invented
rules that say you can't do it. We just haven't
seen any particles like that in the universe. Right. And
the weird thing I guess is that you know, an electron,
it comes from the electric quantum field and a quark

(40:13):
comes from the quantum quark field, and yet they seem
to have charges that are kind of multiples of each other.
That's the weird thing too about the universe, right, Yeah,
that is definitely a weird thing because as far as
we know, those fields are not that closely related, Like
there are similarities there between the electron, the neutrino, and
the quarks are either paired together in similar ways, Like

(40:35):
the W for example, can decay to an electron and
a neutrino. It can also decay to a pair of
quarks because that pair of quarks have a charge difference
of plus or minus one. So there's definitely relationships between them,
but we don't really understand all those relationships. What this
suggests is that there's some deeper relationship between the electron
and the quarks than we even understand. Like maybe the

(40:58):
electron and the quarks are all made out of some
tinier little particle, and some arrangement of those little tiny particles,
which each have their own electric charge, is what gives
you the electron with charge one or the quark with
charge minus one third, the same way that like atoms
are built out of the same building blocks and you
get all sorts of different behavior and overall charges and whatever.
Maybe electrons and quarks and neutrinos are all built out

(41:20):
of the same tiny little building blocks, and that would
explain all the relationships between them, including this strangely fortuitous
relationship of their electric charges. Maybe there are puscals out
there in the universe, and maybe you are corpuscular particle,
I mean, opuscular physicist. It's so much fun to say.

(41:44):
But there are theories out there about these so called
milly charged particles, particles that have really really tiny electric charges.
We're talking about things down to like a thousands or
less of the charge of the electron, and there are
experiments out there searching for them as well. Well. I
feel like there's maybe two possibilities, right, Like, there's a
possibility that there is a whole new kind of particle

(42:06):
that we don't know about that has a charge that's
one thousands of the electron or you know, a point
nine to infinity charge. That's one possibility, is that you
have a whole new kind of particle that we hadn't
seen before. And then there's the other possibility. Then maybe
there are electrons out there with one point one electrical charge.
So which which one are we talking about here? We're

(42:28):
talking about both of those possibilities, but we're also talking
about a third possibility. Maybe there's another kind of particle
out there. They call it a para electron, and it's
got plus or minus para charge. So like some whole
new kind of charge the way we were talking about,
like the strong force has its own charge. Now I'm
badge in a new force with a new charge and

(42:49):
a new particle with that force, and it has its
own new particle, like the photon. So you have a
para electron with its para charge and its para photon. If, however,
that new photon and the paraphoton talk to each other
a little bit, if they mix a little bit, that
can exchange information a tiny bit, then that para electron
would look to us as if it had a tiny

(43:11):
electric charge. So it would really have its own parrot
charge of plus or minus one, but we would see
it as having a tiny electric charge because we would
only capture a little bit of it through this photon
para photon mixing. Wait, I don't get it. So we're
imagining a whole new particle a whole new kind of force,

(43:31):
and you're saying that maybe that new fours leaks a
little bit or interacts a little bit with ours in
that it's its own force. But it's sort of to us,
it looks like it's like it overlaps with the electromagnetic
forces that we're saying a little bit. Yeah, you've got
it exactly, that's exactly right. So it has the same
strength as electromagnetism, but we mostly can't see it. So

(43:53):
we see it as if it was a tiny little
version of electromagnetism, like electrons with a tiny charge. Now,
why do you need this whole setup to imagine a
particle with point o one charge? Can I just imagine
a particle with point on one charge? You can? Theorists
don't like that. I was reading some papers about that,
and theorists always just dismissed that possibility as not very esthetic.

(44:17):
I think that they want a reason why a particle
would have some arbitrary, tiny little chart rather than just
like putting the number in by hand. You know, often
theoretical physicists don't like to add parameters to the universe
that don't have an explanation, and so they look for
a reason why it would have to be this way,
So it's a little bit more indirect. But theoretical physicists

(44:38):
preferred like sits better in their minds for reasons. Honestly,
I don't totally understand. I see they prefer to think
about it coming up with a whole new fours in
a whole new particle that has a little bit of
coupling with the electromagnetic force, rather than just coming up
with a whole new particle that has a little bit
of an electromagnetic Yeah, that's exactly right, you know. And

(45:01):
a lot of things that happen in theoretical physics are
guided by a sense of aesthetics, like what would be
a pretty way for this to work mathematically? What would
give us a beautiful description of the universe? And that
in the end is subjective, you know. We like to
think about science as objective and based in fact and
making progress in lockstep as we approach the truth. But

(45:23):
a lot of it really is also a search for
beauty and elegance in the universe, and that's kind of controversial.
There are some folks out there who think that's misguided.
The universe doesn't have to be beautiful and other folks
that think that the search for elegance and beauty in
our theoretical description of the universe has led to great discoveries.
So it's a very controversial approach, but anyway, it's part

(45:44):
of the literature of milli charged particles. Now, you said
this is one kind of possible millicharged particle, having this
whole new particle with whole new force. But then they're
the other two that I mentioned, which is like, maybe
there are particles with just a little tiny bit of
electric charge, or maybe like the electrons we know sometimes
have a little bit or a little bit more or
less electric charge. And you're saying we're looking for all

(46:06):
of these things, or just we're only looking for the
new force, new particle model, we're looking for all these things.
Is a lot of different experiments searching for these things.
Some people are looking for these para electrons. Other people
are looking to see if maybe the neutrino doesn't have
zero charge, maybe it has a tiny, tiny, tiny charge. Remember,
whenever we measure something in physics, it's never exact right.

(46:28):
You can't measure something to be exactly zero. You know,
we've just set a limit on it, you can say, well,
if neutrinos had a charge, it would be less than
some tiny value, or we would have seen it. So
people are trying to like nail that down. Is it
possible that the neutrino might have a tiny little charge.
There's a whole broad set of experiments looking for these things. No,
I guess, maybe walk us through how do you even

(46:49):
look for these things? So first of all, to discover
one of these particles, you have to see it by itself.
You need to isolate it and demonstrate that it really
has its own electric charge, sort of like the way
we have seen quarks inside the proton. Right, you can say, oh,
maybe quarks have a charge two thirds, but until you
see them operating on their own, you can't really say
that you have found it. And so we try to

(47:10):
do this in accelerators. For example, we smash protons together
and we see new stuff that comes out. And everything
that's created in the accelerator is immersed in a magnetic
field that bends its path. So electrons fly out of
the collision and they curve, and how much they curve
depends on their charge. So one thing you can do
pretty easily is look for particles that bend weirdly in

(47:33):
your magnetic field because they have a tiny electric charge,
they'll bend a tiny little bit. If they have some
huge electric charge, they'll bend a lot. And so that's
one quick thing that you can do is just like
look for weirdly bending particles created in accelerators. But I
guess the hard thing is, like we mentioned earlier, is
that the universe is quantum, right, Like, if something has

(47:55):
point o one electric charge, that doesn't mean it's going
to interact with something that has one electric charge, right
Like the universe only likes to make exchange. It if
you have exact change, that's right, But some of those
interactions are still allowed. Like if you have a particle
flying by with zero point zero one electric charge, it
can radiate a photon that doesn't violate conservation of charge,

(48:16):
and then that photon can knock off an electron in
your material can it can it generate a photon, but
they aren't photons also quantized. Photons are quantized, but they're
not electrically charged. So an electron can generate a photon
or this para electron could also generate a photon, wouldn't
break any of the rules. Yes, you have to quantize them.
You have to generate one electron or two electrons. But

(48:38):
having a tiny electric charge doesn't prevent you from generating
an integer number of photons. But they would have to
be really tiny photons, right like point or one of
a photon. Kind of Now, you would still generate one photon,
you just have a smaller probability of generating photons. So
particles with smaller electric charge generate basically fewer photons, so
they ionize material less. This is actually another way people

(49:01):
are looking for these things. It might be that we
are generating these millicharged particles in our accelerators, but we're
not seeing them because they just don't leave a trace
in our detectors, which mostly require particles to ionize the
material to knock things out of the way as they
fly through with their electric charge. So some folks have
set up dedicated experiments far away from the collider, like

(49:25):
near the collider, but through like meters and meters of rock.
They stead of special detectors, hoping that a millicharged particle
will fly all the way through that rock, not ionize
anything because of it's low electric charge, and then suddenly
decay in their detector, and nothing else basically could survive
all of that rock. So if they see something there,
they'll be pretty convinced they see something that can survive

(49:47):
all that rock and also decay into photons, and so
probably a particle with very low electric charge. I feel
like this gets a little bit into the idea that
maybe charge is really or of a probability which we
probably can't deep too deep into, but maybe talk to
us a little about the other ways that we're looking
for these particles. Another way to look for these things

(50:09):
is in cosmic rays. A lot of discoveries have been
made just by looking at the particles that come from
space because they smash into our atmosphere and are basically
like little particle collisions that can produce all sorts of
crazy stuff and so muans, for example, we're discovered by
looking at particles coming from the upper atmosphere. And if
you use a cloud chamber, this is just a chamber

(50:30):
where the air is super saturated with water, so charge
particles flying through it will tend to create droplets, so
you can see the path of particles. You might have
seen one in a museum sometime. You can see muons
flying through it. Well, the drop density, like how many
drops you make per centimeter, for example, depends on the
charge because it depends on how often you're shooting out photons.

(50:52):
And so if you saw a particle flying through there
with very low drop density, that would tell you that
you have a particle with low electric charge. So people
are using cloud chambers to study cosmic rays and see
if they can spot some of these very low electrically
charged particles cool and how else are we looking for these?
There's really fun experiments that are basically the successors of

(51:13):
Milican's oil job experiment. They're taking a blob of matter
and they're looking to see if there's basically the kind
of atom that you were talking about earlier somewhere inside
this blob of matter. Like imagine some other particle with
a tiny charge orbiting a proton right bound to the nucleus,
making some new kind of atom. And if it's also
very massive, if this low charged particle has a high mass,

(51:35):
it would be like bound to the nucleus and very
very close to the nucleus. So people are looking for
this like weird kind of stuff embedded in matter, and
they theorize that it might have been formed early in
the universe. But because these things would be very heavy,
they were on Earth, they might have sunk down through
the Earth's crust and all have pooled up near the
center of the Earth. So you can't just like scoop

(51:58):
up a chunk of dirt and look for these weird
objects inside of them because they probably aren't any So
what they're doing is they're looking for asteroids. They take
like a slice of an asteroid and they see if
they can find these weirdly charged heavy objects inside an
asteroid slice. And they use an experiment similar to Milligans.
It's called a leavetometer, where they have like a blob

(52:20):
of the stuff magnetically suspended in this oscillating an eclectric field,
and they watch the motion of it to see if
they can detect something which can't be explained by an
integer number of charges, very similar to the oil job experiment.
Like maybe there is this kind of new kind of
material here on Earth. Is that what you're saying with
the new forest and the new particles, is that what

(52:41):
you're looking for, You're looking for like regular asteroid rocks
that somehow have this new kind of matter somehow stuck
to it. Yeah, exactly, maybe deep within it there's one
of these things. And they can try to figure out
if a huge blob of matter has one or maybe
two of these things by oscillating in an electric field
and seeing it behaves strangely. It's a lot of details

(53:02):
there we don't have time to get into, but the
basic version is that you can take a chunk of
matter and study its behavior in electric fields to see
if it has any of these new weird atoms in
it that might have milli charged particles within them. So
you're you're basically looking for a new kind of matter, right, yeah,
exactly that we had never seen before. And you're wondering,
I wonder if it's in this rock or this rock,

(53:24):
or how about that rock? Is it in this rock? No?
How about there? Yeah that's exactly right, And that seems crazy,
but you know, it could be that it's everywhere, that
it's in all the rocks, and so might as well check.
And so what they can do is they can say, look, oh,
well we didn't find it, and so maybe it's just rare,
and that they can do bigger and bigger experiments and
check more and more rocks. You know, but imagine the

(53:45):
universe where they're in every rock and nobody bothered to check. Right,
What a crazy discovery that would be. All right, well,
good luck finding this magical kind of matter in every
rock out there in the universe. I guess we give
us a sense of you know, why we're looking for
this stuff. I mean, it sounds kind of impossible because
we haven't seen it doesn't need to affect the rest

(54:07):
of the universe in any strong way, otherwise we would
have discovered this new kind of matter. Are we just
trying to check the box that it doesn't exist. We're
trying to check the box that it doesn't exist, but
also we're trying to get a little bit of an
answer to the question like why is there charge? And
why does it have these properties? Why does it all
seem to come in these rational fractions of each other.
It's just not something that we understand, and so if

(54:30):
we could find this thing, it would be a huge clue.
Tell us, Oh, that's not a rule in the universe.
It's not required to have that. That's just the examples
you happen to discover early on. You know, there's lots
of times in the universe when we drew big conclusions
based on incomplete information. All of Newtonian physics, for example,
is based on not ever seeing things go really fast
or not ever seeing space get bent really really hard.

(54:53):
So we want to be careful not to jump to
conclusions based on the small amount of information we have.
We want to check and see if it's possible well
to do other things, and that'll tell us like, oh,
this is a rule in the universe, or Nope, that's
not a rule in the universe. Don't worry about it.
I feel that this idea wouldn't really help you, right,
Like if there is a new kind of matter with
its own force and its own particle and field and everything,

(55:15):
and that only sort of tinggently interacts with our that
only looks like it has a small electric charge, that
still wouldn't help you understand why electrical charges are the
way they are, right, It would just open up a
new question, like why does it only interact a little
bit with this new magical field. But if that other
field exists and it does interact with the photon, that
means it has some connection to charge itself, and so

(55:37):
it would shed some light on the nature of charge.
But yeah, absolutely would opened up a whole bunch of
other questions. All right, well, stay tuned, and in the meantime,
I guess keep driving those electric cards because it's putting
those electrons to work. And don't overcharge your credit card.
All right. We hope you enjoyed that. Thanks for joining us,
see you next time. Thanks for listening, and remember that

(56:07):
Daniel and Jorge Explain the Universe is a production of iHeartRadio.
For more podcast from my heart Radio, visit the iHeartRadio app,
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