What's the most promising theory of EVERYTHING?

Daniel and Jorge talk about string theory, loop quantum gravity, M-theory, p-branes, geometric unity and ice cream!

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Episode Transcript

Speaker 1 (00:08):
Hey, Daniel, what's the one thing you most want to
understand about the universe? I think I might say everything
does everything count? Is one thing? Well, it does if
we understand all of it together and how it's all
like connected, you mean, like how we're all one with
the universe? Man, exactly past the banana peels. Man, that's

(00:30):
the goal. So when you go through an ice cream
store and they say, pick one scoop of ice cream,
do you try to order everything? Also? Yeah, I do.
I try to convince them of my unifying theory of
ice cream, you know that unifying your veins to right,
and do my best to bring it all together. Well,
at least it's insightful and delicious. Hi am Jorge. I'm

(01:04):
made cartoonists and the creator of PhD Comics. Hi I'm Daniel.
I'm a particle physicist and I eat a lot less
ice cream than I thought I would when I was
a kid. What do you mean you had a projection
as a kid and you're not meeting the expectations. No,
when you're a kid and you think, Wow, when I
grow up and I get to decide what I eat,
I'm just gonna eat ice cream all day. But turns
out that's not really what I want. Really, what happened?

(01:26):
You change your mind? You haven't found your perfect ice
cream flavor yet. Maybe I just ate too much ice
cream in college and I'm just done. Oh so you did,
I accomplish your goal. It's just that you know, you
found out that once you achieve your goals, then you
know life goes on. Yeah, maybe I blew through that
one a little too quick, and I gotta move on
to something else. I maybe it's the opposite. Life stops

(01:47):
going on, and you eat too much ice cream and
you realize that maybe that's it. Maybe life should be
measured in scoops of ice cream. Maybe everybody lives the
same number of scoops of ice cream and you blew
it all in your twenties. But welcome to our podcast.
Daniel and Jorge Explain the Universe, a production of I
Heart Radio in which we try to take a big
scoop out of the universe. We serve you up a

(02:08):
delicious ball of sweet sweet understanding of the mysteries of
the universe. We talk about everything that's out there in space,
the crazy stuff colliding and producing gold, the weird stuff
in tiny little particles. We think about where it all
came from, where it's all going, and what it's all
gonna do, and we try to make sure all of
it makes sense to you with a cherry on top

(02:31):
and some sprint. Because even ice cream is made out
of physics, right, The ice cream is made out of particles,
which are made out of subparticles, which are made out
of sub subparticles. Try the same particles that everything else
in the universe is made out of. Stars, planets, moons, asteroids.
It's all sort of one big, continuous, giant, delicious, mostly

(02:51):
frozen universe with sprinkles on top. Absolutely, it's amazing, Yes,
But this picture that we can take the universe and
like reduce it to tiny particles so far seems to work.
All the crazy stuff that's out there, it seems so different,
but we can explain most of it by boiling it
down to a few little bits and how those bits

(03:12):
fit together. And you know why, I don't know why
we live in the universe like that. It could have
been that we lived in a different kind of universe,
one where every kind of thing has its own particle.
And you don't really get any simplification when you try
to take it down to the lower level. But fortunately
we do live in a sort of lego universe where
there are a few basic building blocks and everything comes
out of the arrangements of those. Yeah, it is pretty

(03:34):
odd to think about, right, Like, even frogs are made
of the same thing as you know, quasars and giant
asteroids floating in space. It's all sort of made out
of the same little bits and pieces. And it's not
just like the same types of bits. It's actually the
same bits and a basically the same proportions. You have
the same ratio of protons, neutrons, and electrons and basically

(03:56):
every element and every element it makes everything. And that
means that basically everything you've ever eaten is just a
different arrangements of the same number of protons, neutrons, and electrons. Yeah,
and it seems like there aren't that many of those particles,
right Like, as far as we know, the standard theory
of physics says that right now, we think there are
about only what is it, twelve particles in the entire universe. Well,

(04:20):
it sort of depends on how you ask, right, Like,
most of the stuff we see out there in the
universe is made out of only three of them of
quirks down corks, which give you protons and neutrons, and
then electrons. You only need those three to make most
of the stuff. But then we have found other particles,
and you're right, we're up to twelve now matter particles.
But we don't know if those twelve particles are actually fundamental,

(04:42):
if they're made of something smaller, or if there are
more particles out there. There could be like twelve million particles.
We just haven't found most of them yet. I guess
it's kind of like how we, you know, discovered the
periodic table of the elements at some point, and we
thought we had everything figured out, and then it turned
out that each of those elements is actually like a
copy or a repeat of the same sort of smaller

(05:04):
particles electrons, protons, and neutrons, And even though it turned
out to be made out of other particles. And another
flabbergasting and amazing fact of the philosophy of science is
that we seem to be able to understand the universe
differently but effectively. All of these different levels like chemistry
kind of makes sense, right. You don't need to know
all the details of the particles for that to work,
and then you drill down into the atomic physics and

(05:26):
that kind of makes sense, and nuclear physics makes sense,
and then you get down to like the tiny, tiny
particle physics, and there's all these sort of layers at
which you can think about the universe made of pieces,
and the rules of those pieces are understandable. But we
can also drill down and find even smaller pieces. So
it's incredible to me that there are these layers of understanding.
You don't have to go all the way to the

(05:48):
tiniest bits in order to make sense of the universe
around you. And just like how you use the word flabbergasting,
I am flabbergasted. I am grateful and amazed that the
univers is sensible. You know, sometimes listeners right to me
and they ask, like, do you think it's possible for
us to understand the universe? That one day far in

(06:08):
the future humans will understand everything? And you know, I
don't know the answer to that. Obviously we can't know,
But you know, I don't think dogs will understand the universe.
We're a little smarter than dogs, but I don't think
we're maximally smart. So there's certainly a chance that we won't,
so I'm just kind of grateful and flabbergasted that we
figured anything out right. I think maybe dogs understand the

(06:30):
universe to the extent that it serves them, you know,
like most dogs probably feel like they have a pretty
good sense of the universe around them and they are uncomfortable.
Maybe that's it's our future, you know. We'll just understand
it as far as getting our treats and our rubs
and the tummy go, and then maybe we'll stop. Well.
I think dogs would definitely be better off if they
were smarter. Like my dog thinks that every time the

(06:52):
refrigerator opens, it's getting a treat, but that's definitely not true.
And if it understood, like you know, how to open
the fridge on its own, or what time of day
typically gets a treat, or what it should do to
encourage us to give it a treat, I think we'd
get more treats and waste less time. Yeah, but then
you just eat ice cream all day, Daniel. Maybe dogs
are smarter than you think. I'm pretty sure a dog

(07:13):
would eat ice cream all day. Have the chance, let's
do that experiment. Let's put some ice cream in front
of a dog and see what happens. Maybe the key
to happiness, Daniel, is not getting what you want, to
be optimistic about getting what you want. Maybe dogs are
one with the universe more than we are. Well, maybe
this is turning into a dog psychology podcast. Welcome to
the dog whispering philosophizing Daniel and Jorge explain your pets

(07:36):
to you. Oh my god, that is a winning podcast idea.
Let's pive it here, Daniel, your cat is really just
not that into you. Yeah, and now tell me about
your rats. Do they get flabbergasted as well? Our rats
have unfortunately passed away because rats only live a couple
of years. They're wonderful pets. They're smart, they're intelligent, they're responsive,
they're actually affectionate, but they are sort of short lived.

(07:58):
It was a bit sad. That's why we now have
a dog. I'm sorry. I guess they went back to
being particles. They live on. Their particles live on through
the universe. It seems like it's all connected. Everything's made
out of the same basic particles, which I think makes
physicists wonder if you can go further and break things
out even more and maybe get down to one particle
or one type of particle that ties the entire universe

(08:22):
together into one theory. We would love to do that.
To explain everything in terms of one equation, we could
just write on a T shirt, hopefully not a big
T shirt, on a onesie or maybe like one with
extra long coattails. That would be a new fashion statement,
or in super duper tiny font that you need reading
glasses to read. Now, we want a simple theory. We

(08:43):
want to reveal the fundamental nature of the universe. A
goal of physics is not just to optimize our ice
cream intake, but to sort of understand, to have that
moment where we're like we get it, We're like, oh,
that's how the universe works. And to do that, we
want one simple idea that tells us what rules are. Yeah,
it's a big goal in physics. It's the ultimate dream,

(09:03):
perhaps of a physicist to discover it. And so today
on the podcast, we'll be asking the question, what's the
most promising theory of everything? Everything, everything, everything, like everything right,
like all of it. Yeah. I guess you could also
call it the most promising theory of the universe. Yeah,

(09:26):
except that these days we've gone beyond the universe. We
have the multiverse, and so you know, maybe you should
call it the every verse or the olive verse or something.
Everything's most promising theory of Everything's you can't have Everything's.
That could be the sequel through the Theory of everything
in the movie The Theory of Everything's the theory of

(09:46):
the theory of everything. Yeah, so it's a goal in
physics to come up with one, I guess, one equation, Daniel,
what do you think this theory will look like? One equation? One? Hey? Well, one,
you know, fortune cookie, piece of paper will What will
this theory look like? What will this theory look like? Wow?
I wish I knew. You know, Currently we use math

(10:06):
as the way we express our ideas. Matter and forces
are both described by fields, which are expressed as quantum
field theories, and so one hope is that we could
generalize quantum field theory and use it to describe things
at the smallest level. But you know, we've explored a
tiny little fraction of the universe. As you say, the
universe is mostly cold and things are moving slowly, and

(10:29):
it could be that what we've learned is not representative,
and it's always dangerous to extrapolate from like a tiny
little corner or the universe to the rest of it.
You wouldn't say you understand elephants if you've only ever
looked at one elephant's tale, for example. And so I'd
love if quantum field theory was the path forward. But
I suspect we need some sort of completely new kind

(10:50):
of mathematics in order to make progress towards this final theory.
And you have to discover new math before you can
discover a new physics. Absolutely, we're constantly inventing or discovering
new math to make progress. It's this fantastic sort of
duet between math and physics. Mathematicians invent some new tool,
they're like, hey, this is useless but fun, and the

(11:11):
physicists are like, wait, I can use that for something.
Bring that over here. I'm gonna build that into my theory.
And I'm never actually sure whether mathematicians are like delighted
to have their tools find use or a little disappointed
that they've been like sullied by brought into the physical world.
Do you think they see you as a duet partner
or as like a backup singer. Oh, I definitely think
that mathematicians think of physicists as sort of like unnecessary

(11:32):
frosting on the cake, you know. I think mathematicians see
themselves as more primary and fundamental than physicists, the way
I think a lot of physicists think about chemistry and biology,
you know, sort of these like layers of the onion.
I heard one mathematician described his department as the halls
of truth without irony, the halls of snobbery, which trickles down,

(11:54):
is what you're saying, is a trickle down effect for
snobbery in the sciences. There's a whole hierarchy of snobbery. Absolutely. Meanwhile,
everyone uses their phones and computers which are made for
by engineers to do their science exactly, and it's not
just limited to science. Snobberries everywhere. But anyways, this is
a big question, a lofty goal, and we were wondering,
as usual, if people out there on the Internet had

(12:16):
ideas about everything, which sounds like a redundant question. As usual,
Daniel went out there and asked people if they knew
what the most promising theory of everything is. And so
thank you to everybody who have volunteered, and especially to
our recurring superstar Lucien who has volunteered. I think consecutively
for every single one of the last forty episodes. If

(12:37):
you'd like to participate, please don't be shy. Right to me.
Two questions at Daniel and Jorge dot com. Think about
it for a second. What do you think is the
most promising theory of everything? Here's what Lucian and a
lot of other people had to say. Um, I don't
know much about theories of everything. You only want to

(12:59):
know of it about is string theories as the one
I think is maybe string theory, which I've also heard
referred to as brain theory, has that it evolved a
little bit instead of just strings. Now they're saying maybe
it's membranes. I didn't know there was more than one

(13:21):
theory of everything. That's pretty cool. Something to do with
the theory that unifies general relativity and quantum theory. Maybe
it makes me think of social media. If you go there,
you help. You'll have people having theories about everything. But

(13:43):
the most promising one it's the superstring theory a guess
um um um ones that Brian Green and and others
are walking working on it. I'd say the most promising
theory of everything is the Big Bang theory. Uh. It

(14:06):
encompasses all of the sciences anties them together neatly into
a theory for cosmology and you know, especially for chemistry, physics,
all of it. It just seems to go together. Well.
I like string theory, but I'd say the Big Bang
theory is about her. Dr Michio Kaku speaks of an elusive,

(14:30):
elegant equation, perhaps an inch or so long, that operates
in both the quantum and relativistic realms. I would have
to side with Professor Cocku and nominate string theory as
the most promising, but I think that squeezing all that
math down to an inch will be a bit of
a stretch. I will vote for string total Well. I

(14:53):
happen to think Luke quantum gravity is on the right track,
but that's not actually a theory of everything. String theory
seems to be losing favor, as I think is also
M theory, the many worlds explanation of things. It's always
right because there's always a place where it's right. I
don't really know the answer. I think the most promising

(15:13):
theory of everything is the M theory that can only
be done by that one guy whose name I can't remember,
and nobody else seems to understand it all right, I
think I just realized something, Daniel, What's the acronym for
a theory of everything is t o e toe? So
really you're looking for the big toe of the universe. Yeah.
That's sort of tough to reconcile with the snobbery of

(15:35):
particle physics, isn't it. What do you mean? Are you
saying toes aren't ignoble somehow or not worthy the highest regard?
Definitely exactly. Toes make me think of, you know, toe cheese.
It's kind of smelly. You can stub your toe, you know.
Toes not like poetry written about people's toes very often?
Haven't there been love songs devoted to toes? Are some

(15:56):
people into toes? I'm into theories of everything, so maybe
put me in that kind gregory of being into your
toe theory finishist, But our listeners have definitely thought about
the theory of everything. There were some good answers here,
A lot of people engine string theory. I feel like
people are maybe familiar with that idea that maybe it
could be a theory of everything. Yeah, and thank you
to all those listeners. And I want to make a

(16:16):
shout out to one of our youngest listeners, two and
a half year old Hannah from Australia. Her dad wrote
to me and said that she was home from childcare
was sick, and she asked him can we listen to
Daniel and Jorge. So thanks Hannah for listening to our podcast.
And you said, obviously the answer is no, right. I'm
not her dad. We're not qualified to take care of children, Daniel,

(16:37):
especially not other people's children. I think Hannah should get
some more ice cream. What do you think, Joey. I
think she should maybe be listening to some math podcasts instead.
But I said, a lot of ideas out there about
the theory of everything, So let's break it down for people,
and so real quick, Daniel, what would you say is
theory of everything? How would you define it? Well? Everything
for physicists means like all the experiments. We want to

(17:00):
explain basically anything that you can do. We want to
be able to predict what happens. We don't want any surprises.
We want to be able to say, if you smash
these two particles together, here's what's gonna happen. If you
drop a feather on the moon, here's what's going to
happen if you bring all this matter together. Here's how
a black hole forms. We want to be able to
predict what happens. We want to know what the rules are,

(17:22):
and so at the most fundamental level, that means explaining
all the kinds of bits of stuff there are out there,
all the matter, and then all the rules about how
those bits talk to each other, so like all the forces.
So put simply, we want a single description, a single idea,
a single mathematical equation that explains all the matter and
all the forces in the universe, like one theory, one framework,

(17:46):
or one equation that can tell you what's gonna happen,
or maybe not what's gonna happen, but what's likely to happen. Right, Yeah, exactly.
Our universe is quantum mechanical, which means we can't say
exactly what will happen, but it's still deterministic because we
can say what's likely to happen. We can say, if
you shoot an electron at a proton at this angle,
here's exactly the distribution of possible outcomes, And so the

(18:08):
wave function is still deterministic, even if how it collapses
is not right or more accurately, Like if I smashed
these two particles together a hundred million times, that you
should get, you know, approximately ex proportion of this happening
or exproportion of that happening. Yeah. If you're a frequentist
and that's how you interpret probability, then yeah, exactly, in

(18:28):
a hundred millions similar experiments, you would get this distribution
of outcome. If you're a basy and then you say, well,
there's a probability of various outcomes. Did you just call
me a frequentist. Yeah, you just outed yourself as a frequentist.
And I know whether I should be offended or flattered.
I guess it depends on your posterior. I guess I
feel flattered, you know, fifty of the time, offended another
fifty percent of the time. No, don't, I'm a frequentist.

(18:49):
I think it makes a lot more sense. All right, Well,
let's get into some of the details. Who have what
a theory of everything would apply to and what are
some of the leading candidates right now? But first let's
take a quick break. All right, we're talking about the

(19:15):
big toe of the universe, the big theory of everything
that could maybe one day explain everything that happens and
predict exactly how it's all gonna turn out, every little
nook and corner of the universe. Right, I know, that's
what a theory of everything promises. That's what a theory
of everything promises. Yeah, it's to explain everything in terms
of one idea. And you know, the history of physics

(19:38):
is that we saw a lot of weird stuff and
we try to explain sort of each bit, and then
we look for patterns and we try to like organize
the stuff into groups. We said, well, you know what,
maybe lightning and static electricity are actually the same thing.
Then we developed like a coherent explanation for electricity, and
so the basic step forward there is not to say

(20:00):
lightning is static electricity. Obviously they're related, but they're different.
You try to fit them together into a common idea,
right to say these two things are part of the
same larger concept. They both come from the same effect
or the same I don't know, equality in the universe
or something. Yeah, and you can generalize that a little bit.
Like we've made further progress by noticing that there's a

(20:22):
deep relationship between electricity and magnetism, right that, like particles
that have charges on them, for example, are affected by magnets,
and particles that move can make magnets. So this is
deep connection between electricity and magnetism, and we unify that
into electromagnetism. Again, that doesn't say, oh, electric charges are
the same as magnets. It's not saying that they're identical.

(20:45):
It's just saying that it makes more sense to fit
them together, that there are two sides of the same coin,
and mathematically they sort of clicked together like pieces of
a puzzle, like they can be predicted by the same equation. Yeah,
there's a symmetry in the equations. In fact, if you
look at the equation of electromagnetism, you notice that the
electric field and the magnetic field have exactly the same

(21:05):
and opposite rules. So there's four of those equations, and
if you swap the electric field, the magnetic field and
all of them, you get the same equations. So that's
kind of cool. I guess you know. There's a lot
to the universe. There's a lot in the word everything,
and so would discover everything like matter, forces, base time.
Are you trying to wrap that all up into one equation? Yes, exactly,

(21:27):
I want all of it you know, put all those
scoops under one big cone. Um. We definitely want to
explain matter. Like we were talking about before, we would
love to understand what is the most basic element of
the universe. First of all, how many basic elements are
there in the universe. And by elements, I don't mean,
you know, like lead or iron, I mean the most
fundamental thing in the universe, the basic ingredient, the smallest

(21:51):
piece out of which everything is made. We'd love to
understand what that is. You know, we don't think that
the current list of particles we have are fundament We
don't think that those are the answer, right. They might
be reducible too, simpler bits and pieces exactly because when
we look at these particles, we notice weird patterns, patterns
that don't make any sense, patterns that don't have any explanations.

(22:13):
And those patterns are typically historically very valuable clues that
lead you to figuring out how to sort of assemble
the current list of fundamental particles out of something smaller,
to figure out how they might be made out of
different combinations of smaller bits. And it would also have
to cover the forces, right or or do you count
those as particles because forces have particles too, right, Yeah,

(22:36):
we would love to explain the forces, and we can
explain the forces in terms of fields and then ripples
in those fields and being interpreted as particles. Absolutely, So
you can think about the universe is made of fields
or made of particles either way, So forces you can
think about as fields or as particles. But we definitely
like to unify these forces and to understand them together.
Where we're talking about a minute ago was sort of

(22:58):
the unification of electricity and magnism, and we've made a
lot of progress there. We've even unified electromagnetism with the
weak nuclear force, this force that's responsible for beta decay,
radioactive decay, and other sorts of radioactive processes. We understand
them now to be like part of one larger mathematical construct,
the electro weak force, and we're sure that's correct. We

(23:21):
know that that's true, that it reveals something deep about
the universe because realizing how those two things clicked together
is what allowed us to predict the existence of the
Higgs boson, which was a pretty big step in unifying everything.
So what this include then also gravity as well? Do
you hope to sort of explain gravity in one quantum framework. Yeah, absolutely,

(23:41):
we would love to explain all of the forces together.
Now we have some forces for which we have a
quantum mechanical description, like electromagnetism and the weak force and
the strong force. We haven't yet managed to merge all
those quantum mechanical forces together. These are the forces that
you can describe in terms of a quantum field or
part goals passing back and forth. And we have not

(24:02):
yet unified the strong force with those other ones, so
that's left to be done. We would also like to understand,
like is gravity even a force doesn't belong on this list,
like you mentioned earlier, We want to unify all the stuff,
all the forces, and then space and time, well, our
space and time really their own separate thing. Are they
just manifestations of some quantum gravitational quantum mechanical force. Are

(24:25):
there really something different? We don't understand that at all.
So yes, we would like one clear understanding where all
the pieces fit together, and all the pieces have to
be there, like it's a complete puzzle, not just a
few pieces that stick together, Like you don't want to
have any bits left over where you're like, what is
this for or how does this fit in? I don't know,
just you know, keep it there on the side. Now,

(24:45):
you want, like the equation is to tell you why
that thing is there or why it's not there exactly,
and we want the math to lead us there. We
want to find like symmetries that say this is the
only way these equations work because they have to follow
this rule, you know, Like we have symmetries that's say,
for example, every inertial frame of reference follows the same

(25:06):
law of physics, and that really limits the kinds of
laws of physics that you can write. You can only
write ones that follow those rules. And we think that
that's the symmetry of the universe. So we'd like to
sort of find symmetries that tell us how to write
the laws of physics. And it would be great if
there was only one possibility, if we're like, you know what,
this is the only one that sort of works. It
hangs together, it has all the pieces we need, doesn't

(25:28):
have any extra bits that don't correspond to things we see,
and so that would be really beautiful. And then we
could look at that and say, Okay, what does this
tell us about the universe? What is this reveal about
the source code of the universe vanilla? So it's trying
to tell us, Daniel, it's the writing on the sweetness
wall there. No, I would guess the universe is probably
raspberry flavored. You know, there's these huge gas clouds of

(25:51):
Ethel's in the center of the galaxy, and you know
is responsible for the smell of raspberries. Are you saying
God has a favorite flavor or scent. I'm saying the
universe has a smell and it's not vanilla. And it
doesn't feel like nothing. It smells like everything. Yeah, exactly
smells like barbecue. All right, Well, this is a pretty
lofty goal. I guess what makes is this? Just think
it's even possible? Like, why should the universe be reducible

(26:13):
to a few simple equations or laws or rules. Why
couldn't the universe just be kind of crazy and random? Yeah?
I think simply the answer is hope. We hope that
it's possible. We would love for it to be possible,
and like many human projects, it's just driven by hope,
not faith, you know, just hope. We would love to
have an explanation for the universe that is simple and complete.

(26:37):
We don't know why any explanation for the universe holds,
Like why do science even work? Why can you do
an experiment today and then tomorrow the same laws of
physics still work. We don't even know why that's true. Right,
So we're, you know, on sort of shaky ground philosophically.
But we've made a lot of progress, right. This hope
has fueled us towards a ever deeper understanding of the

(26:58):
nature of reality and an ever simpler description. Like as
we peel apart matter, we do find a smaller number
of simpler objects that explain complexity at a higher level.
You really only need about three particles to explain hurricanes
and hamsters and lamas and all that stuff. So so
far it seems to work. We've made pretty good progress.

(27:19):
But then, Daniel, the problem is you also have to ask,
is there a theory of hope? Can you explain hope
for the theory? And then your brain explodes. It's a
theory of inception and it's not just hope. Right, We've
made some good progress, and also we have some good tips,
Like we look at some numbers, and we look at
some trends, and things seem to be going in the
right direction. What do you mean. Well, for example, we

(27:41):
would love to explain how all of the forces are
really the same thing, you know, not that they're exactly identical,
but that they're like four parts of the same thing,
the way like the power rangers come together into one
big ranger or whatever you call that. So we'd love
to do that, and one obstacle to doing that is
understanding why they're all such different strengths. Like the weak
force is pretty weak, and the strong force is pretty strong,

(28:04):
and gravity is like a crazy week. It's hard to
understand how you have these four bits and fit them
together if they're all such different strengths. Well, it turns out,
and we talked about this on the podcast one time,
that the strength of the forces depends on the energy
of the experiment you use to probe them. Like the
charge of the electron depends on how closely you look,

(28:25):
how far you penetrate into this like cloud of virtual
particles that surround the electron. Well, all of the forces
are like that. It's called the running couplings. The value
that dictates how powerful the forces depends on energy. The
amazing things that as you go up in energy, all
these numbers are pointing together. It seems like they're coming
together to one common value. There are a lot of

(28:48):
hints that maybe it is possible to unify everything together
because things sort of leaned that way. Yeah, things are
leaning that way. We think that if the universe was
really hot and dense and there was a lot of energy,
that all the forces would be similarly powerful the way.
For example, magnetism seems weaker than electricity, right, Well, it
turns out that if you're going at the speed of light,

(29:09):
the two things have equal strength, which is why photons
can exist, because they're just electricity and magnetism like slashing
back and forth in perfect balance. So at the speed
of light, those two forces are the same. And we
think that in the very early universe, or at very
hot dense environments, the strong force, the weak force, electromagnetism,
and maybe even gravity all have the same strength, which

(29:33):
would help us fit them together into sort of like
one big idea. All right, interesting, Well, I guess maybe
let's go into now what are some of the leading
candidates for this theory of everything. I know that there
are a couple of ideas out there. Some are fringe,
some are more mainstream and a lot of people seem
to know about. So what are some of these leading

(29:53):
candidates for the universe's total Well, there's definitely one that's
far out ahead of everybody else in terms of like
a number of people who were investing their careers in
it and believing like it might actually lead to a
theory of everything. And that's definitely string theory. Yeah, that's
the one with the best PR department too. It seems
like a lot of people had heard of the string
theory exactly. A lot of people have written really beautiful

(30:16):
popular science books on it, and there's lots of specials
about it, and people talk about it. It's also sort
of cool and it's easy to sort of visualize because
it tells you that the universe it's not made out
of these weird tiny dots that are hard to get
your mind around, but instead that it's made out of
these little vibrating strings. And now these little strings, are

(30:37):
they like part of a field? Are they just like
strings floating in space? Are they part of a giant
like universe? You know, guitar or what? Are these strings?
So there are quantum objects, right, So in that sense,
you can think of this as a quantum field theory, right,
and these little strings instead of saying, like, you know,
a little energy located in a point in a field

(30:59):
instead of matter, gin like a one dimensional version of
a particle instead of a zero dimensional version. Imagined a
one dimensional version of a particle. That would be a line,
And then this thing can vibrate. You can have different
kinds of energy. And the cool thing is that if
you look at these strings from really really far away,
they look like particles because you can't sort of like
see how wide they are. But if you zoom in,

(31:21):
you would discover that all the things we call different
particles are just the same string vibrating different ways, like
vibrates this way you get an electron, vibrates that way
you get a graviton. So you're saying, like all quantum
particles like a cork or an electron. If you zoom
in enough at the core of it instead of a
point particle, you'll see like a little what vibrating though,

(31:42):
And how can it be one dimensional if the electron
and the cork are multi dimensional? Well, in our current theory, right,
electrons and quirks are zero dimensional. They're just point particles
that have no length, no width, no height, and so
that's kind of bonkers. It doesn't make any sense. You know,
how can you have mass with no volume? It would
have infinite density and you know, turn into a black

(32:03):
hole and all that stuff. We dug into that whole
thing in another podcast episode. So this just takes it
and stretches it out and makes it one dimensional. Says
it has length but no width and no height, and
then it can vibrate because that string can move because
the quantum field itself can oscillate. Right, but is it
vibrating in any particular dimension or direction or is this

(32:24):
in like another dimension it's vibrating. Yeah, So the mathematics
that string theory are complicated, but it turns out that
they work best if space has more dimensions than just
the three that we're familiar with. If it has like
eleven dimensions and these other extra spatial dimensions would be
sort of very hard for us to see. That would
be very very small. So it's kind of difficult to

(32:46):
have visualize. But imagine like every location in space, right, X, Y,
and Z those are the three dimensions. Now at every location,
you can also like go around, or you can like
turn or there's like another direction, another dimension of your location,
another value you need to specify to say exactly where
you are. Interesting. So it's reducing quantum theory to like

(33:09):
little string theory. Yeah, exactly, and then these strings oscillate
often in these other hidden dimensions. Now, there are some
theories of extra dimensions of space and time in which
those dimensions are very simple. They're just like little loops,
and those are fun. We've talked about them on the podcast.
String theory requires these extra dimensions to be really complicated.

(33:30):
Objects are called callaby Yaw manifolds. They would have very
very complicated geometries and anyway, the strings would like vibrate
in these crazy dimensions that would be invisible to us,
but based on their vibration in those dimensions, they would
appear different to us. So if it vibrates, you know,
this way all those other dimensions, then it would be
an electronic vibrates that way, it would be a muan,

(33:51):
and that would be pretty awesome to understand. Like, oh,
electrons and muans. They look like one is a copy
the other one. That's because one is like the reds
of the other one, or it's you know, a different
standing wave of this vibrating string in this other dimension.
It would help us unify those things and understand, like
the relationships we see in the particles are actually just

(34:12):
different modes of those strings. Is it kind of like
you know, how different sheets of paper look all the
same from the side, but maybe if you look at
them from another dimension, they could have different shapes and colors. Yeah. Absolutely.
Or if you're a two dimensional object in the three
dimensional world, the stuff that's happening that third dimension can
definitely affect what you see and you just aren't privy

(34:32):
to it, and so you're seeing a little slice of
what's going on, and you can't understand the relationships between
those things because they exist in a dimension that you
can't move in or you can't see. But string theories
also it's just sort of beautiful mathematically, like it all
really fits together very nicely, and a lot of people
are really attracted to it because some certain things just
sort of like fall out of the theory. For example,

(34:54):
string theory is a very natural theory of quantum gravity.
You basically have to have grab in your theory. If
you have a string theory, interesting, it really pulls out
your heart strings. That's what you're saying. All right, let's
get into what some of the other leading candidates are
and let's talk about which one seems the most promising
out of these promising candidates. But first, let's take another

(35:16):
quick break. All right, we're talking about the theory of everything,
or at least a couple of theories of Everything's and
talked about string theory as one of the most popular ones.

(35:38):
But there are a couple of other theories that are
up there, right. They're still in contention for everything, for
the hole shabangba exactly. So what are some of these theories.
One of my favorite is sort of a generalization of
string theory. String theories and idea that's been around for
decades and people were poking around making progress, and they
were like a few kinds of string theory that had

(35:58):
been developed, and they only described like a little bits
of the universe, or there was this kind of string
theory of those kind of strings and how they interacted.
The field was sort of fracturing to several different ideas.
Then in Ed Witten, is like one of the smartest
people ever, unified them all together. He showed that all
the different string theories that people have been working on.
We're really just like sort of limiting cases that were

(36:20):
like extreme versions of one grander theory. So we had
these like five different string theories and he brought them
together into one theory that he called M theory, like
the multi string guitar theory of string theory exactly. And
you know, nobody knows why it's called M theory. And
eventually somebody asked him like, hey, Ed, why did you
call this thing M theory? What does M stand for?

(36:41):
He said, well, actually he didn't know when he was
waiting for us to like really deeply understand it and
then we could figure out what M stood for. I
think he really just wanted to say my theory. It's
my theory, and like I'll just hide it as a
physics nomenclature maybe or since his last name starts with
a W, maybe like has a secret upside down W

(37:02):
in there. Uh. Interesting, Like the anti version of him
came up with this theory exactly right, And so M
theory is sort of like a super version of string
theory and includes other things like supersymmetry, this idea that
every particle that's a fermion, like the matter particles have
relationship with all the bosons the fourth particles, and for
every boson there should be a fermion. For every fermion

(37:24):
there should be a boson. So it brings that together
also into one larger theory. Instead of just thinking about
individual strings, this allows us to think about like two
dimensional versions that they call brains, which is short for membrane,
not like b our ai in your brain. Right, Like
maybe things aren't strings, but they're like little and nap

(37:45):
can cost, right, yeah, like little sheets or three or
four dimensional. And so they have these arbitrarily dimensional objects,
you know, one dimensional, two dimensional, three dimensional, and so
they call them about this rather ridiculous name P for
the number of dimensions, and then P brain the dump dump,
that's a P brain theory. Then it really is a
P brain theory. But you hear these like super smart

(38:07):
people really talking to each other about P brains, you know,
without any irony or giggles. It's good thing they didn't
call it the opposite brain P brain P theory. Well,
you know, there are a lot of people out there
who don't think that string theory is the path towards
a theory of everything. They think it's ridiculous waste of
time and all just sort of mathematical conjecture. They're like
theory and everything that's a theory of nothing. Yeah, exactly. Well,

(38:30):
the real criticism of string theory is that it operates
at such a tiny level that we can't really test it. Like, sure,
you're telling us maybe what's happening at tend to the
minus thirty five meters, but how do we know. We
don't have a collider that can do experiments yet at
that small scale, and so it's just sort of like
a story we're telling, but not something we can test. Really.

(38:51):
The only test of string theory so far has been
a search for these super symmetric particles, these extra fermions
and bosons that might be there to balance on the
ones we have in the standard model, and we were
supposed to find those at the Large Jhon Collider, but
we didn't. We didn't see any supersymmetric particles. So that's
a bit of a blow for string theory. All right. Well, then,

(39:13):
if strings or little napkins or key brains are not
maybe the best way to go, what's an alternative? Then well,
some people are coming at it from a completely different
direction instead of taking quantum mechanics and trying to incorporate
gravity and making this big quantum mechanical string theory view
of the universe. They're starting from gravity, and they're saying,
instead of making gravity into a quantum theory, let's just

(39:36):
try to quantize space itself, like you were talking about
earlier space and time or fundamental elements of the universe.
We don't really know if that's true, if these things
come out from something smaller. We don't understand what space is.
So a lot of people are working on this theory
called loop quantum gravity, which tries to take space and
describe it as these little bits of like a quantum foam,

(39:57):
and I have the whole universe sort of come out
of the quantum foam, like instead of having a like
a perfectly smooth universe and space and time on which
you have these quantum fields that are lumpy. Maybe space
itself is kind of crunchy and lumpy and not perfectly smooth. Yeah,
maybe there's like a minimum distance to the universe below

(40:17):
which it doesn't really make sense to talk about things
being closer together than that, because it's just not possible.
Like all of spaces like pixels on some universe screen
and so that's exciting and people have been working on
that the last few decades. There's been some advances and revolutions,
and it seems sort of like as an alternative to
string theory because it's a different way you might be

(40:38):
able to bring gravity and quantum mechanics together. It's a
completely different approach and it's made some progress. But the
problem is that it's sort of just brings gravity and
quantum mechanics together. It doesn't actually unify all of the forces,
Like it can't explain why do we have electromagnetism, why
do we have the weak force? Why do we have
the strong force? But it's you know, progress in that direction, right,

(41:00):
I guess you can if you you know, make space
itself quantum. Then that doesn't explain how what like particles
can interact with each other across the distances. Is that
kind of the limitation. It's not really a limitation, it's
just like they haven't gotten there yet. They're still building
the foundational building blocks. It's not clear necessarily how you
would get there. It's not ruled out, it's not impossible,
but so far the scope of loop quantum gravity is

(41:22):
not to describe all of it is just to make
this step of bringing gravity and quantum mechanics together. Once
you do that, you can collect your five note about prizes,
you know, take a day off, and then you can
start working on the other part of the theory. Right well,
so those are some of the respectable toes, you know,
that's the big toe, the middle toe of physics, his
feet and feet. But there are also sort of like

(41:44):
these less respectable toes or you know, kind of the
pinky toes of the universe floating out there, the theories
that are not quite as popular or mainstream, but that
might be exciting. So Daniel real Quick tells, what are
some of these fringe theory right well, theories of everything
are a popular target for people who are not in academia,
who think like maybe the physicists have just sort of

(42:05):
gotten it wrong, and what it needs is like a
fresh idea from somebody who's not entrenched in all of
these ideas and the history on the incremental progress, coming
in with a brand new idea and blow it all up.
And so, for example, Steve Wolfram came out last year
with the theory that he thought might be like the
foundations of a theory of everything. He's a smart guy.
He's a guy who developed mathematica, and he is a physicist,

(42:27):
has a degree in physics. And his basic idea, which
we dug into once on the podcast, is that maybe
the universe is made out of these cellular automata. He
envisions that the universe is made out of one kind
or a small set of kinds, of tiny things with
very simple rules. And he studied this for a long
time and shown, and many other people have shown that

(42:48):
if you start from simple things with simple rules, you
can get complexity. And we know that already, like hurricanes
are not written into the laws of the universe. They
arise from corks and electrons into being in really complicated ways.
So what he did was he showed that, you know,
you can sort of have like cellular automata that right
the rules of the universe. You start from a few

(43:10):
simple ideas and then a rule for how those ideas
can change. They can sort of like write the rules
of the universe. And he looked at what his cellular
automatic produced and they sort of looked physics ee, and
he was like, ah, look at this, maybe this is
how the universe was generated. All right. So that's one
kind of a fringe idea that you know, maybe you
can make a universe at a very simple building blocks cells.

(43:32):
What are some of the other fringe theories. Well, there
were a couple of engineers who took it upon themselves
to write a theory of everything. This is a theory
that's called the Fragments of Energy theory by two guys
in North Carolina called Silverberg and Icean, And they were
thinking about energy and they're noticing that like energy seems
to flow, doesn't ever just sort of like hang out.

(43:53):
And they thought, well, you know, maybe energy is the thing,
and like energy always flows through the universe, and you
can think about it flowing through these lines, and maybe
you can quantize it and like break it up and
need these little packets and think about how it flows together.
So they wrote down some rules for how energy flows
and how to break it up and how these packets
of energy would then interact, and they were able to

(44:14):
do some cool stuff with it, Like they twisted it
a little bit and added a few bits, and they
were able to reproduce some predictions of general relativity. So
they thought that was pretty cool, and they put this
out there to quite a lot of fanfare. Actually it
hasn't landed very convincingly, Like I think most of academic
physics was like, yeah, that was a paper review, review

(44:37):
or number one says maybe her number two days And
is that the most hurtful review you can get in physics,
Like not something dissecting your math or telling you why
your hypothesis is wrong. Is it's a difference you could
imagine revising general relativity or like reimagining it in some
different conceptual space and reproducing it. That's cool, But it's

(44:58):
not like a new theory of everything. So I haven't
really like made any progress. In fact, their theory doesn't
quite reproduce general relativity. They need to like add some
by hand numbers to squeeze it in there to get
things right, like you know, the procession of mercury and
the bending of light around the sun. Stuff Einstein got
right a hundred years ago without having to tweak or
tune his theory at all. They got to sort of

(45:19):
like put this in a little bit by hand. So
it's not really clear that it's progress. It's not like
a way forward. It's just like, here's another way of
looking at general relativity. That makes more sense to us,
and also doesn't quite work as well, so not necessarily
like really that exciting. It doesn't seem inevitable or a
shoe in right away, and it also doesn't necessarily tell
you what to do next. Like the exciting thing about

(45:41):
string theory is that the thing is to explore their
puzzles to solve. They're like, oh, we can try this
different compactification of those other dimensions. We can try this one,
we can try that one. There's areas where you can
make progress here. It's just sort of like, oh, that's interesting.
I'm not sure what to do next with this. What
are some other fringe theories? So another one that got
a lot of attention was going to buy a guy
named Eric Weinstein. He also has a PhD in physics,

(46:04):
but now it works at a hedge fund, and he's
a you know, very well known guys on podcasts all
the time, and he has a theory called geometric unity
that he came out with about ten years ago. And
he basically just takes all the theories that we have
now and sort of stacks them on top of each other,
sort of like an ice cream sandwich and says, I'm
just gonna stick them all into one container. What do

(46:25):
you mean, like quantum gravity, like quantum physics and general activity,
you can stack them. Well, he doesn't have quantum gravity
in there yet, and so he's just taken all the
quantum theories and stacked those together. And you know, like,
I'm not really sure way you accomplished in doing that.
It's just sort of like groups them. It doesn't necessarily
like show that they're part of one larger hole or

(46:47):
that they have a deep relationship. He likes the way
they've stuck together, but there's no simplification that's achieved there
in my understanding, I see, it's still pretty unsupported, I guess.
And another issue with it is that he hasn't yet
written a paper about it. So it's been out there
for about ten years. And he was invited to give
a talk about it at Oxford, and he came and
he presented it. The problem is that like nobody invited

(47:08):
all the physicists at Oxford and so, and that hurt
your feelings. So now you're just down on the theory. No,
And in academia, you know, we need to see a paper,
We need to like see all the detailed description so
we can think about it and play with it and
read about it and talk to each other about it.
And he's actually recently promised to put a paper out.
Maybe they asked him why why did those and he

(47:29):
write a paper and he just said, and you're like, oh,
you got us, you got us. And other mathematicians that
have looked at what he said sort of digested what
he said a podcast and in his one presentation has
said that they found it mathematically inconsistent. You know, there
are reasons why we haven't stacked all these theories together.
They don't play nicely together. There are anomalies, there are
things that don't make sense. They're inconsistencies that happen if

(47:51):
you try to jam them together and you don't find
the right way to do it. It doesn't seem like
he solved those problems. But we'll just have to wait
to see what his paper says. All right, Well, those
are some pretty interesting and promising fringe theories, and we
also have some core, more popular theories. I guess just
two sort of close us out here. Daniel, Let's talk
about really quick about whether or not you think it's

(48:12):
even possible to have a theory of everything, and even
if we find one, would it be useful at all
in helping us in our everyday lives. You know, it
might not have immediate engineering applications, right, even if you
understood the universe and its smallest scale and all its
littlest rules, that wouldn't help you understand when a hurricane
was coming, or you know how to get to the

(48:34):
neighboring galaxy necessarily. On the other hand, it might reveal
something deep and fundamental about the universe that would give
us immediate applications, if you like, uncovered a new force,
or let us tap into and control dark energy, the
biggest fraction of the energy budget of the universe, that
could very much really change our lives. We never know
what this understanding will reveal, I mean, their hand. It

(48:57):
could allow us to create terrible weapons, and then we
could wipe each other out, So you never know what
the future holds. Could be useful, It could destroy all
of humanity, you know, we don't. We don't really like
to think about those practical consequences. Yeah, exactly, from the
worst possible outcome to we are now masters of the universe. Basically,
that's the spectrum we're talking about here. Then you just
blame the engineers and politicians. Exactly. I was just eating

(49:21):
some ice cream. It wasn't my fault. How was just
sitting here snacking on ice cream and being flower gas
did and all of a sudden, we're all dead. And
if that worries you, you you know, there are people who
argue that maybe it's impossible. You know, there's this famous theorem,
this Godal's incompleteness theorem that says that all mathematical systems
are either inconsistent or incomplete. You know that either they

(49:42):
contradict themselves or there are things that cannot be proven.
What what is this theory based on? How can it
say that everything is wouldn't it also be inconsistent itself?
Oh man, we need a whole another podcast episode to
dig into goals in completeness theorem. So let's put a
pin in that. But it's a formal theorem and mathematics,
which people think is right. You can argue about what

(50:05):
exactly it applies to and whether it applies to physical
theories or just two axiom based mathematical systems. But some
people use as an argument to say, like, maybe there's
a limit to how well our mathematics can describe the universe.
You know. It doesn't say that the universe isn't physical
or doesn't make sense. But maybe, like our mathematical systems,
which are based on these axioms, are just not the

(50:27):
right language for exploring the universe. You know, it's not
guaranteed that the universe can be described by mathematics just
because that's the way we like to think about it currently.
So what would it be. I guess we can talk
about it at another time. But if not math, then
what I don't know. We'll have to meet those alien
physicists that have developed something else. What's the foundation, what's
the language of their physical theories? Maybe it's not mathematics, right,

(50:50):
just because we can't imagine it doesn't mean it's not reality,
all right, And like you said, it might not even
be possible to confirm these theories in the end, right,
because we're talking about scale for which we really don't
have a microscope to go and check that's right. Yeah,
until we build a solar system sized particle collider, you know,
send in your checks, we can't really test these theories.

(51:10):
And it might be that it just keeps going on forever,
Like you might find what do you think is the
smallest theory, but it just keeps going down and down
the rabbit hole exactly. It might be that there is
no smallest scale and that there's just like an infinite
layers to this onion. Hey, that's an idea onion ice cream.
Maybe that's the unifying theory of everything, Daniel the infinite

(51:32):
onion flavored ice cream. Wow, I'm flabbergasted. And while it's
fun to think about the theories of physics, that sort
of physicists are thinking about a lot of people out
there thinking about theories of everything, and sometimes they email
them to me. I got an email from one of
our listeners who had a fun idea. He says, quote,
maybe our observable universe is actually the nexus of two

(51:54):
different overlapping universes, one for quantum mechanics and one for
general relativity, and that's why we can't unify them. So
it's interesting. Yeah, it's fun to think about, and it's
sort of tantalizing because everybody knows this is a big
goal in physics and physicists that are struggling to get there,
and it would be fun to sort of like have
that moment of inspiration and see the truth of the universe,

(52:15):
and then you know, reveal it to everybody and eat
to my scream while you win your Nobel prize. Then
you can be flavor gasted and live in the halls
of truth. That's what we all aim for. I think
that should be the name of our ice cream pop
up stand, flavor Gasted. Let's do it all right, Well,
hopefully we'll make some progress in the future. In the meantime,
try not to stop your toes, Daniel, and don't eat

(52:36):
too much ice cream. Well, we hope you enjoyed dad.
Thanks for joining us, see you next time. Thanks for listening,
and remember that Daniel and Jorge Explain the Universe is
a production of I Heart Radio. For more podcast For
my Heart Radio, visit the i heart Radio app, Apple Podcasts,

(53:00):
or wherever you listen to your favorite shows.