What Is String Theory?

We've all heard of it, but nobody really knows...

Learn more about your ad-choices at https://www.iheartpodcastnetwork.com

See omnystudio.com/listener for privacy information.

Episode Transcript

Speaker 1 (00:06):
One thing that I really love about physics is that
sometimes the laws of physics don't just work, they're actually pretty.
What do you mean physics can be pretty? You know?
I thought physics and science was like a hard hitting
objective thing, you know, human endeavor. Absolutely, we got big tasks.
We want to understand the universe and makes sense of it.
But sometimes we come up with an idea, something that

(00:27):
just looks beautiful, something which is has an innate elegance
to it. You mean, like you'd see a theory walking
down the road and you'd be like, oh, man, that
that theory hasn't going on. Yeah, there's some sexy the
curves in that theory. You mean like graphs though, right,
Like that that kind of occurs, right, that graph is
a nice curve to look those peaks. And one of

(00:48):
the most controversial theories of all time, one of the
ones that gets people up in arms, is also one
that's probably survived because it's so beautiful. An alogot isn't
the theory of attraction. No, it's a theory that was
once described as a piece of twenty first century physics
that had fallen by accident into the twentieth century. So

(01:08):
it's a future Babe, future baby exactly. Hi. I'm Orge,

(01:29):
I'm a cartoonist and I'm Daniel. I'm a particle physicist,
and we are the authors of the book We Have
No Idea, which talks about all the things we don't
know about the universe and how we might hope to
one day understand them. Yeah. So, welcome to our podcast.
Daniel and Jorge explained the universe, in which we take
everything and anything in the universe and try to explain

(01:49):
it to you in a way that makes sense and
hopefully makes you laugh to be on the program. We're
going to talk about, Oh, string the that's right, string theory.
And this is a question that we've been getting from listeners.
We ask people, please send in your request for topics,
and maybe more than fifty percent of the request work.

(02:10):
Can you explain string theory? What is stringth theory? Talk
about string theory more than yeah, and it's fascinating. It's
because string theory really is a part of sort of
cultural zite guys. It's like an idea that people know
exists even if they don't understand it. It's a big
part of that show The Big Bang Theory, right, like
the people in that show there they supposedly study string theory.
I don't know. I don't watch that show me neither,

(02:33):
but that's what I've been told. Your cultural advice expert
has told you that this is a culturally relevant thing. Well, yeah,
it's it's something people have heard about. Well have you
heard about string theory before you started spending your time
talking to physicists? Know, yeah, I've heard about it. You know.
It's one of these things that you hear a lot about.
It's these like crazy theory about the universe, but it's

(02:53):
really and you know, you hear certain things about it, like, oh,
everything is made out of strings, but you don't really
kind of know what it is and what does it
mean for things to be strings. You're a very visual person.
What image do you get in your head if I
tell you everything is made out of strings? Do you
get like a universe an idea of like a universe
where everything is crocheted out of yarn? Or how does
it work? In your head? I would to just ask

(03:14):
what are those strings made out of? Right? Right? Of course?
So you are a physicist at hard right, because every
question just leads to the next question. That's right, beautiful physicists,
a hard supermodel on the outside. No comment. Um, but
I thought it was an interesting question to tackle because
it's something everybody has heard about, but very few people

(03:34):
actually understand. I think that's why people wanted us to
talk about, is saying, can you make this not just
something we have heard this phrase, but something where we
can know what it means and gets an insight into
why people are spending their time doing it. Right. Yeah, So,
as usual, we went out into the street and ask
do you know what strength theory is? Yeah? So before
you hear these answers, think for a moment, could you

(03:55):
define strength theory? Do you know what it is and
why it's persisted for so long. Here's what people who
I asked had to say. Um, No, I have no
idea what that is. No, I do not. I've heard
of it. My only way of Big Bang theory Okay,
I don't know. I'm sorry. The connectedness of Adams and

(04:15):
sub atomic particles Okay, it's something that Sheldon worked on. Yes, Okay,
So first of all, it's kind of interesting because you
normally you go out into your university campus to ask people,
but this time you went somewhere different. Yeah, that's right.
You see, Irvine was closed for a holiday, so instead
I went to the mall here in Irvine, the Spectrum,
and I asked a bunch of random strangers, um questions

(04:38):
about science. And again I was struck by how many
people were willing to answer my questions. I thought people
would say, who are you? Go away security security? Right?
Maybe they sense a certain beauty about you, Daniel, You're like,
who is this beautiful specimen of a person? Know? Who is?
Apparently I just don't look very threatening, you know. Um,
I look like I could could get knocked to a

(04:59):
religious a passing breeze or something. Um. So everybody was
willing to engage, which was awesome, and people had some
pretty fun ideas, and everybody had heard of it. Nobody
had said hell what, and your other speculation was correct.
Some people had heard of strength theory specifically because of
the Big Bang theory. So thank you Big Bang Theory.
You've mined all of this juice from nerd culture and

(05:21):
you have actually communicated something to the public. And congratulations.
Nobody understands what string theory is, but they do understand
that it is a theory. Well, I think that show
doesn't even try to explain it, right, They almost use
it for the opposite effect, Like, let's depict our characterist,
this impenetrable, unrelatable genius that speaks gobbling Google, so we'll
just having to talk about strength theory and that nobody

(05:43):
and nobody's going to understand that. So it's it's likely.
So you're saying string theory represents the impenetrability of physics.
I think it's more important to explain these things to
people rather than just toss these words around and try
to intimidate people. So yeah, I think that's what I mean.
It's like they use it to intimidate people about physics, Yeah,
when physics is nothing but warm and cuddly and just

(06:03):
wants to explain the universe to you. Man, there's nothing
intimidating about physics, right. It's about revealing secrets and giving
understanding and insight and appreciating beauty. And that's the thing
about string theory is it doesn't just potentially explain a
lot of things. It also offers some elegance, some gorgeousness,
like a peak into what nature is doing underneath. Because
you know, you can have ugly theories and you can

(06:25):
have elegant theories, you know, and you might ask the difference,
like how what is the difference? Well, I can ask
you the same question about art, right, Like I look
at the Kendinsky and I say, hey, that's beautiful, and
somebody else says whatever, I could do that in an afternoon.
It's garbage. It's subjective, right, you can't. It's like the
whole question of what is beauty is something that's very
difficult to nail down. So you shouldn't judge a painting

(06:46):
by the same metric you used to judge of physics theory. Um.
And you know, two physicists can disagree about what theory
is pretty and what theories ugly. So it's it's totally subjective.
It's not an objective fish like a you know, I
like this kind of theory. I like that kind of theory. Yeah,
Like you know, I like theories with handcuffs in the
midstet of strings, right, like my handcuff theory of the universe.

(07:09):
That's where that's where you're going theories or yeah, okay,
So let's break it down for people. What is string theory? Right?
So string theory is basically is the idea that the
smallest elements of matter with things that things are made
out of are not points, not particles, but instead their lines,

(07:32):
their strings, strings of what strings of basic universe stuff? Right, So,
like the electron is is not like a little ball,
and we know it's like a quantum object, which is
like a point with some kind of probability. But you're
saying if you zoom in even more, maybe you would
see a little squiggle there. Yeah, And the sort of

(07:53):
two ideas there. One is what is the most basic element?
And the second is is their most basic element? So
this assumes there is a most basic element. You know
that you you look at something next to you, pick
up in the nearest object you have, you know, maybe
it's an apple, maybe it's a platypus, maybe it's a
you know, I don't know what, and and think about
what it's made out of. It's made of molecules, right,
Tear those apart, you get atoms. Tear those atoms apart,

(08:15):
you get protons and neutron's electrons. Tear those apart, you
get quarks. Right, and you could keep going and eventually
you get two smaller and smaller particles. Right. The question
is do you ever get to the smallest particle. Right,
that's one question. Is there a smallest thing? And we
covered that in a whole podcast, but here we're just
gonna assume that there is. Right, at some point, you
get down the most basic thing where you're not allowed

(08:36):
to ask what it's made out of because it's made
out of the most basic universe stuff. It's like the
one circle on a lego set. It's like, you can't
get any smaller than that. That's right, it's the unit exactly,
And that's you might feel like that, that's frustrating. Why
can't I ask what it's made out of? You know?
But it's also not frustrating because it would be the answer.
I mean, if you actually got there and you said, look,

(08:58):
everything in the universe is made out of this one
basic thing. That's a deep insight, right, that's what we're
going for. That's the day we wish for that we
peel back a layer of reality and see everything is
made out of this thing, because then you can ask
why this thing? What does that mean? Oh? I see?
So string theory is saying that everything electrons course, eventually,
if you break them down, you'll get to this one

(09:20):
type of string. That's right. We think of things being
made of particles, We think of them as tiny dots
right in space. But string theory says they're not dots,
their lines okay, and they're they're these loops and wiggles
instead of being dots. And then everything is made out
of these strings. And you might ask, well, how can
you get different kinds of particles, for example, out of

(09:42):
one kind of string? Right, And the idea there is
that the strings can vibrate, the strings can wiggle, right,
the reverberations in the string just like you know a
rubber band or a string. Is it like an actual vibration,
like it goes up and down or is it just
like the different shapes you can make with a string. Oh,
I see No, it's actual motion of the string. Yeah,

(10:03):
And so it's different, different vibrational modes. So they get
excited and they can get into this state or that state.
As the string vibrates in different ways, it makes different particles.
So some tiny particle calling it's an electron, for example,
is actually a string vibrating this way, and a cork
is a string vibrating the other way. And the neutrinos
a string vibrating a third way, so the same thing

(10:26):
with different vibrations can appear as different particles. Okay, so
it's not like different strings and a guitar. That's not
what we're talking about. We're talking about one string. It's
like a one string guitar and just the different ways
in which it can vibrate that gives rise to all
the different stuff we see in the universe exactly. And
like a guitar, you can pluck the string differently and

(10:47):
you can get different notes, right, you can if based
on how fast it's vibrating and you know where you
put your finger in the end, you can get different
notes out of the same string. And it's key here,
that's one string, right, it's a single string. Because we're
to explain everything in the universe in terms of one object.
So we're trying to explain how you get all this
complexity in terms of one thing. And that's the answer
from string theory is that the string has different modes

(11:11):
to it to drink, can do different things. And you know,
you might think that's sort of weird, Like I expect
stuff if it's all made of the same thing, to
be the same thing, right, Like if everything is made
of the same stuff. Why is this red and that blue?
And this tastes delicious and this tastes terrible, right, And
it comes from the way it's vibrating. It's kind of
like maybe light. You know, a light is just made

(11:32):
out of one thing, photons, but depending on the frequency,
then it's different colors. Yeah, exactly. And the way things
move and vibrany can totally affect the way they we
perceive them. You know, think about for example, water, right,
water is made out of water molecules, but so is ice,
and so is steam. Right, They're made out of the
same thing, but we feel them, we experience them very

(11:52):
differently because of the way they're moving, right, steam and
liquid water. How the water particles moving more than an ice, right,
And so it's the most into those particles that generates
the macroscopic qualities that we used to define it. So
the things we used to define the electron and things
we used to define a quirk actually come just from
the vibrations of these strings. Again according to this theory. Okay,

(12:13):
so so then, but then my question is still, what
are these strings made? Is it just like made out
of universe I told you? Or hey, you're not let
to ask once we get down to the lowest level,
no more questions. No, but you know what I mean,
like is it like a like a physical string or
just like a mathematical string? Do you know what I mean?
Like is prepare for philosophical detour here, like what's actually

(12:37):
vibrating like universe stuff? Yeah? Yeah, Well, because I still
look in the end, all physics theories are just models. Right,
you gonna ask the question is this really happening or
is this just a mathematical model? In my head, I
used to do calculations and predict the results of experiments. Boom.
That is a big philosophical question, right, and there's no

(12:57):
way to answer that. So we think of these things
as models in our head reflect reality. Okay, you know
the top cork doesn't exist or not? Or is it
is a calculation a model in my head? We could
you know, smoke banana peels and talk about that for
a long time without making any progress. So this model
is just asking me to imagine that the most fundamental
thing at the universe are these little strings. They can

(13:19):
vibrate in different ways, but then these trains can move
around and they can't be cut into pieces. Right, you
can't get anything smaller than a string. It's the most
basic unit. Like, there's something about the stuff of the
universe that is just you can't vibrate or do things
shorter than these little strings. Yeah, exactly. Or thinking about
it from the other direction, you know, how do you
make a universe? Well, you start with a huge pile

(13:40):
of tiny strings, and then the way those strings interact
gives you all sorts of interesting structure. But that's what
you start from, right, that's the universe's initial condition is
like a huge pile of strings. And these trains can
move around space. Yeah, they move and they interact with
each other, right, and that's where all interesting stuff. But
are these related to the quantum fields? How does that
really fields? Yeah? So everything we'd be built out of

(14:02):
these strings, including all the particles and all the forces.
And that's actually why string theory is so popular because
string theory, we think, can explain some of the mysteries
of quantum fields and some of the mysteries of how
to bring gravity into the fold and describe it in
terms of a quantum field. So the short answer to
your question is, all the quantum fields arise from these
string interactions. All these fields, all these particles just come

(14:26):
from this one string guitar being plugged the different frequencies.
That's right. So while you're imagining a single string guitar
of the universe, let's take a quick break. All right. So, um,

(14:49):
that's that's a crazy concept to ask people to digest.
But let's assume that that's the theory. Um, why who
came up with this and why do we think it's
a good theory about the universe? Yes, the string theories
had a lot of people contribute to it. It's sort
of an old theory that started out trying to explain
something else and then was tossed aside when it didn't work,
and it was later picked up again, um and reused

(15:10):
two as a theory of everything. And this sort of
idea of string theory is to take a different approach
to solving this question of what is the universe made
out of? As an experimentalist, my approaches take something concrete,
break it into pieces, gets smaller and smaller and smaller.
You know, as you discover new stuff, you're revealing secrets
to the universe, and just keep going until you get

(15:31):
to the smallest bit. Sort of via top down approach, right,
This idea is different. This is sort of a bottom up.
They say, let's just start at the very bottom. Let's
go to the most basic element and try to explain
the universe from the start. You know, if a hypothesize
the universe has made of strings, can we put them
together in a way that explains the universe and describes
everything we see around us? But I guess how did

(15:53):
someone even think of using strings? How do you make
a lot of things out of one thing? And a
little ring that vibrates different ways is one way to
get a lot of things out of one simple thing?
Is that kind of the origins of it? Yeah, exactly,
you should imagine. Physicists are basically random, terrible idea generators,
and most of those just don't work. So at some

(16:14):
point somebody's like fed up with thinking about the universe
in terms of particles, and they're like, well, what if
they're not you know, what if they're not dots, Let's
just try it with lines. Does that work? You know?
And basically every idea that you can imagine, somebody has
tried to make that work as a theory and everything,
and usually given up after about two seconds because the
theory of everything based out of little puppies or whatever
doesn't work. It's very hard to make that put together.

(16:36):
But like they maybe they say, what if there's just
one particle that makes up everything, how would you how
would you explain how this one particle can turn into
other things? And so that's kind of difficult maybe, But
a string, you can imagine it vibrating or moving in
different ways to give rise to different particles, right, yeah, exactly.
And people were playing with it and like, what can
we do with this? And they try, like I said,

(16:57):
they try to use it to solve other problems. Specifically,
they try to under stand the strong nuclear force using strings,
and it didn't work. And then later somebody else said, Hi,
I heard about this idea of strings. I wonder if
I can use that to solve this other problem, which
is why can't we get gravity to play well with
the other forces. You know, if you want to understand
the way the universe works, you have to try to

(17:17):
explain everything in terms of one theory, right, to bring
it all together into a single explanation, because that's a
big problem right now in physics, right, Like it's like
marrying quantum physics with gravity. That's right. It's a marriage
we've been trying to arrange forever, but the two participants
just do not want to do not want to play
along exactly. They don't pressure. Yeah, So we have these
sort of two towering achievements of physics. On one hand,

(17:40):
quantum mechanics, right, a revelation about a hundred years old.
It tells us that the universe is very different from
the way we thought it was, that there's uncertainty, that
there's fuzziness, a limited amount of knowledge we can actually
obtain about the universe. And it's most specifically that the
universe is quantized, it's broken up into discreete little chunks.
And on the other hand, we have gravity and general relativity,

(18:03):
which is an incredibly successful theory that describes the motion
of planets around stars and black holes and all sorts
of crazy stuff and time dilation in the way space
and time are connected, all this incredible stuff. But it
assumes the universe is not quantum mechanical, right. It assumes
that that energy can be subdivided into arbitrarily small bits,

(18:24):
and you can have an infinite number of locations and
an infinite amount of information. Right, And so the two
theories are not consistent, and most of the time they're
talking about different stuff so they don't overlap. Sometimes, like
when you're talking about a black hole, then the two
give you very different stories. Okay, so, how is strength
theory able to marry gravity and quantum mechanics? Right, So

(18:44):
that is exactly the right question. How does string theory
allow us to bring together quantum mechanics and gravity? Well
to understand that, you really have to understand why we
failed without string theory. And the problem is that when
you bring together quantum mechanics and gravity, you get lots
of infinities. Right. A theory doesn't work when it can't
predict the results of experiments. So if you ask a

(19:05):
theory what happens when I smash two particles together, it
should give you a reasonable answer. If the answer is infinity,
or you know, nothing will happen or something, then it
doesn't make any sense. It has to give physical answers,
and infinity is not a physical answer. The problem is
when you try to bring gravity into quantum mechanics, you
get lots of these infinities. And the infinities come because

(19:26):
of the point particles, because you're trying to treat these
objects as if they're just dots in space, and that
leads to lots of craziness. You know, how do you
have mass in a tiny little dot in space that
has infinite density? Right now? We have lots of other
theories that do play well with quantum mechanics. Electromagnetism, for example,
very happily married with quantum mechanics. And the reason that
works is that we have tricks to hide those infinities.

(19:49):
We can bundle up those infinities that that pop up
in the from the point particles in various other ways
mathematical tricks. Those tricks don't work for gravity because gravity
is very different from the other forces. The strength of
the force grows with the energy of the object, right,
So in this case, when an object has more and
more energy, it feels more and more gravity, right because

(20:09):
gravity is proportional amount of energy in an object. So
the typical tricks we use to hide those infinities under
the rug that works for quantum electrodynamics doesn't work for
gravity when we try to do quantum gravity. So how
does string theory to solve that problem? Simple? It just
says there are no points. It says at the smallest scale,
you don't have to worry about dealing with gravity a

(20:31):
tiny points because there are none because that it's smallest scale.
The universe is not made of points but strings, and
so it's a nice way to sort of circumvent that problem.
And that's why string theory can bring together quantum mechanics
and gravity so nicely. And I got people excited, and
that's where the beauty was. People were like, wow, and
it's beautiful. There's like these strings floating around. You get
these membranes and its It seemed really cool to people.

(20:56):
So you said something interesting, which was that people thought
that dringth theory was beautiful and elegance. So can you
try to explain like why people thought that, Like is
it simple or is it just it's so open ended
or it just seems to be working or it doesn't
fall into the ugliness of other theories. I think people
just have fun working with it, you know. I think

(21:16):
it's I think it stimulates people's imaginations can have fun,
and physicists can have fun. Yeah, and you know, when
you do string theory, you write down these diagrams, and
instead of these diagrams being lines with swils, that diagrams
are like loops, and they have sheets to and to
connect them, you know, membranes, and you get to think
about these high dimensional surfaces and people have a lot

(21:38):
of fun with them, and it's been so invigorating for
physicists that's actually led to a lot of good results
just in mathematics, Like mathematicians have learned about things from
the things that physicists have done while exploring its string theory,
and so it's it's stimulated. The whole field of mathematics
and mathematics is about the beauty and interconnectedness of numbers.

(21:59):
They don't care if it actually just scribes anything in
the real world, right, It's about these abstract ideas and
how they come together. And one of the lead physicists
who works on string theories name is Ed Witten. He
won what's basically the Nobel Prize for math, which is
the Field Medal, which is even harder to win than
the Nobel Prize because they only give it every two years,
and he's a physicist, and he won the top prize
in mathematics for advances in string theory, which tells you that,

(22:22):
like there's a huge amount of mathematical machinery that's been
invented here. And these folks they love it like it's
a it's fascination for them. It's a there's a deep
pleasure in manipulating these equations and in thinking about it. Oh,
usually it's the other way around, Like usually you guys
have to come over the theory and convince mathematicians that
this is something fundamental here. It seems to be coming

(22:45):
from the other way. It's like, here's something that even
mathematicians I think might be fundamental about the universe. Well,
I don't know if mathematicians think it's fundamental about the universe.
They just think it helps solve interesting problems. They're like, oh,
this is a cool tool. It can solve some problems
in math, or it gives us a new way to
think about mathematical problems. You know, And anytime you get
a new tool, it's fascinating. And you imagine, for example,

(23:05):
you're an artist and somebody invents a new musical instrument
and you're like, oh, cool, what can I use this for.
I can invent a new kind of music. I can
have a new kind of rhythm or a new kind
of song. Or in the same way, you create a
new physics theory, a new basic object you get to
play with. It's exciting. He gives you things to play
with and ideas to try. And so like this is
a said, hey, look I have a one string guitar,

(23:28):
and were like, whoa, I can play the whole universe
on that thing. But you know, string theory has a
lot of people who love it and adherence and a
lot of people in departments who are working on it.
But there are also a lot of people who don't
like string theory. It's got sort of a backlash as well.
Any you know, you've made it as a physics theory
when you have haters, right, physics haters physics. All right,

(23:51):
let's get into it, but first let's take a quick break.
Al Right, So, strength theory has its haters, people who
don't think it's all that or who think it might

(24:11):
be wrong, or maybe it's not all that beautiful. So
what are some of the arguments against string theory. Yes,
so I would say there's really two categories of attacks
people make against string theory. One is there's just too
many of them, and the other is that we can't
test it. Too many stringth theories, too many string theories.
It's not a singular concept, you know, stringth theory, it's

(24:35):
actually string theories. I remember loctrology, string theories, string theories.
There are a lot of There are a lot of
these things. There's lots of ways that you can put
it together, lots of different ways you can shape the string,
and lots of ways you can have them interact with
each other. And um, you know we were saying earlier,
you'd like a simple theory. You'd like to make your

(24:57):
choices for how you build the theory, not the arbitrary
will be forced by the mathematical construction, you know, like
why is there a three here? It's the only way
that it works. So we have a theory where there
are lots of ways it could work. Then you have
a question like which way do we choose? And that's
the problem with string theory. There's lots of ways to
build one. They all have the same basic idea, right,
which is the universe made out of little strings and

(25:19):
everything comes out of the way vibrates. But you're saying,
there's a lot of options after that basic concept, like
how do they how do these strings interact or what
do they sound like? Or exactly? Um, and the reason
is that you can't make string theory work in four dimensions. Right,
Our universe that we experience has four dimensions, is three

(25:40):
dimensions of motion x, y z and then one dimension
of time, So we live in four dimensions. But strings,
for they get them, to get them to have these
mathmatical properties that we want to unify quantum mechanics and gravity,
they have to operate in more dimensions for the math
works like the dimension in which they're vibrating kind of thing,
and then are four just the ones where it's moving

(26:00):
around it. In some theories, yes, they vibrate in those
other dimensions, and that changes how we see them in
these dimensions. But there's a lot of different kinds of
string theory, and so that's not a general statement. And
some of them are eleven dimensional theories and some of
them are twenty six dimensional theories. Right, And so the
ideas these strings are vibrating these other dimensions, but we
don't see those other dimensions, like I don't I can't

(26:21):
move in twenty six dimensions. How can you say that
your theory, which has twenty six dimensions explains my four
dimensional universe. So to answer that, to solve that problem.
They have to roll up those other dimensions and tuck
them away and make them small, to make them like hidden,
kind of like too small to the experience in our
everyday lives. Yeah, which is why you don't see them

(26:41):
or experience them or see them in physics experiments. And
there's lots of different ways to do that, because twenty
six dimensions a lot of freedom, and so you can
organize that in lots of different ways, and there's you
can make choices, and you have to make choices. How
do you take this twenty six dimensional theory boil it
down to four dimensions. Turns out there's like ten to
the five hundred different ways to organize that, which is

(27:02):
a lot of different choices, different flavors of stringth theory,
or different choices you can make different flavors. You went
to the ice cream shop for string theory, and they
have ten to the five hundred different flavors. And if
you want a sample of each one, you're not even
going to order. You're gonna be full before you leave.
Ten to the five. Thing about what that number is?
Right for scale, there's like ten to the ninety particles

(27:23):
in the universe, So it's the problem in strength theories
said all of these strength theories would work. Is that
kind of the problem yes, um, yeah, And that thing
that gets into the second criticism, which is, you know,
can we test string theory. We can only see the
universe down to a certain scale so far. I mean
we use large the large Hadron collider, and we smash
particles together, we get down to distances of like ten

(27:44):
to the minus twenty meters, right, really really small distances.
So all the string theories, the ten of the five
hundred string theories, they all can explain things that happened
that we've seen so far, all of them right. To
distinguish between them, we need to look much deeper. Oh
I see. So like mathematically there's a whole bunch of
possible ones, but experimentally we can't test which one is

(28:06):
right exactly. And that's the problem because strings, if they exist,
we think they're about ten to the minus thirty five
meters in size, which is super duper tiny. And maybe
you're thinking, I don't know, we can see down to
ten to the minus twenty meters. How much smaller is
tend of the minus thirty five they're basically it's just
tiny it's much much smaller. It's ten to the fifteen

(28:29):
times smaller, right, And to give you a sense of scale,
like the solar system is about ten to the fifteen
meters across. It's a big difference, you know, if you
could see only solar system size stuff, where if you
could see like one meter size stuff. So strings are
really really tiny, which is why we're not anywhere close
to seeing them. Doesn't the theory have also ways in
which it kind of builds up to our world? It does,

(28:51):
but you can't distinguish between those theories. Um, they all
predict the same thing, and they're also competing theories. You know,
there's a theory of quantum loops you not strings, but loops, right,
that also explains quantum gravity. And we can't distinguish between
the various string theories and this theory of quantum loops
because we can't see small enough yet, right. And so
it's a criticism of this whole bottom up approach. Right, Yeah, cool,

(29:14):
you started at the bottom, but you haven't built up
far enough for us to test your theory. Is this
just mathematical masturbation or you're actually doing something useful? Right?
So sometimes people argue like, Okay, string theories nice, but
it's not physics, it's math because it can't be tested.
But that's but then that's what they need to do.
They need to build up their math to sort of

(29:35):
our scale in our world. But you're saying that's really difficult. Absolutely,
it's difficult because they've got a long ways to go.
They have to go from ten to the minus thirty
five up to ten to the minus twenty. It's a
tall mountain to climb. And they've been working on it
for twenty years. And you know, like with any theory
that had um fanfare and and excitement around it twenty
years ago, Um, they're gonna be people who say, oh,

(29:57):
you failed if you haven't succeeded yet, right, and so
people who just sort of impatient. Are we ever going
to get there? Is string theory ever going to provide
something we can actually test or these guys just gonna
be twiddling around on chalkboards for the next two years.
But I think the problem is maybe it seems kind
of random that you would think that the universe is
made out of little strings, and that you would just

(30:18):
come up with this concept out of the blue and say, hey,
let's dedicate twenty thirty years of a lot of people's
time to investigating this idea. You know what, it was
totally random. They just opened the dictionary and picked a
random or and said, let's make it into this theory
out of ice cream. No, as I said before, it's
a bit random, but it works. You know, mathematically, hangs together,

(30:40):
and a lot of theories don't. You can't build a
theory of the universe out of ice cream or out
of puppies triangles. You couldn't make it work. Oh man,
we never thought that. I that's what I mean. Have
you thought about all the possible shapes stick figures. I'll
be right back. Hold on, I'm gonna try and invent
trying the theory right now. I'll get back to you.
Stigure theory. Why not the x K C D theory

(31:01):
of the universe? How could we c string theory? Well,
one thing is you could build a super duper collider
the size of the solar system and and see things.
That's small, but that's the gazillion dollar solution. The other
things you could try to be really clever and find
some unique prediction of string theory that we could see
in our experiments. Something which would only be true if

(31:25):
strings were happening at the lowest level, right, Because in
physics we don't always need to see things directly in
order to prove that they exist or believe that they exist.
You can kind of infer information or Yeah, a lot
of our stuff is a lot of indirect information pointing
in the same place. Right, Like, when you solve a murder,
you don't need to see the murder on video to
prove that somebody did it. You know, you have evidence

(31:47):
from blood spatter and from DNA and from you know,
other circumstantial evidence builds a solid case. It was Mr
Green with the string in the dining room solved. That's right,
We we have solved the mystery. Today on the podcast,
all Right, what do you think the future holds for

(32:07):
a string theory? Do you think it's it's promising or
are people starting to lose faith? I think it's gonna
oscillate back and forth. I think people will lose faith
for a while. It's gonna vibe rate exactly, it's gonna
wiggle and jiggle, it's gonna lose. You know, it's popular
right now and for a while. Everybody who's aplanning grad
school and physics wanted to do string theory because they
heard about Brian Green's book and they heard about a

(32:28):
big bank theory and it was popular. And then there's
a bit of a backlash now, so fewer people are
getting excited about string theory, fewer physics departments are hiring
strength theorists. But it's a promising candidate, and we don't
have that many promising candidates for the theory of everything.
So it'll stick around and people will come up with
great ideas and then everybody get excited again, like, oh
my gosh, look this guy came up with a cool

(32:49):
way to make stringth theory. Do this new thing. So
we will go back and forth. Um, I don't know
if we'll every be able to test it as a
theory that we will require a real moment of insight
to how to find some unique property of string theory
that we can see. Well, I personally hope you guys
figure it out and you know, stop stringing us along.

(33:10):
You don't like that we're just in our offices, you know,
drawing things on the chalkboard, going that's right. I thought
if anybody a cartoonists would appreciate, you know, enjoying the
beauty of diagrams and uh, you know, doodles and stuff
like that, because that's in the end what we're doing.
We're like trying to do the universe into into understanding.
We'll remember, I'm a musician, not a cartoonist. Oh I

(33:33):
forgot that. Yes, um, maybe you could sing something, go ahead, Yeah,
I think us sing us to your theory of the
universe materia. I'm on the edge of my scene. You'll
be running away from your seat if you hear me singing.
But alright, cool, that's a really great overview of the
string theory, right, That's that's part of this quest to

(33:53):
kind of find out what the universe is actually made
of at the deepest level. Yeah. Absolutely, And so thanks
everybody listening, and I hope that we've explained to you
finally what is string theory? Keep plugging way. If you

(34:13):
still have a question after listening to all these explanations,
please drop us a line. We'd love to hear from you.
You can find us at Facebook, Twitter, and Instagram at
Daniel and Jorge that's one word, or email us at
Feedback at Daniel and Jorge dot com.