What can slime molds teach us about dark matter?

Daniel and Katie talk about where the missing matter in the Universe might be, and how slime molds might help us find it. 

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Episode Transcript

Speaker 1 (00:08):
Hey, Katie, how do you feel about mushrooms. I'm a
big fan. They actually make a mean pizza fung Guy
over here that reminds me of the best pizza I
ever ate. It was covered in morals. I still think
about that pizza, like twenty years later. Yeah, they actually
have these really good fried mushrooms, these local ones, and

(00:28):
it was absolutely amazing. But yeah, that is that is
entry level stuff, Daniel. If you're a real mushroom fan,
you would be into the weirder varieties. I'll bring on
the challenge, you know, hand in the woods, oyster mushrooms.
I'm into all of it. You young young, Well, what
about manticor's tongue? Is that real? Did you just make

(00:50):
that up? Wait until you see monkey's head? Well, put
it on a pizza and I will take a bite. Hi.

(01:13):
I'm Daniel. I'm a particle physicist and a professor at
UC Irvine, and I will taste any mushroom that isn't
labeled as toxic. I am Katie Golden, and I too
will eat any mushroom as long as you eat it first.
I am the host of the podcast Creature Feature, and
I'm stepping in for Jorge or, as some theorize on

(01:36):
the Internet, we are actually sort of like two states
of the same person. Maybe if you eat the right
mushroom returned into Jorge, is that how it works? I'll
never tell the banana mushroom. Well, Welcome to the podcast
Daniel and Jorge Explain the Universe, in which we take
a big juicy bite out of the weirdest, strangest, slimiest

(01:57):
mysteries in the universe. We think that the whole universe
deserves to be understood, deserves to be explained, and deserves
to be explored, at least mentally by these funny little
apes living on this weird little rock in the corner
of the galaxy. We think all of it should make sense,
and we do our best to tackle the biggest, weirdest, slimiest,
amazing questions about this bonkers and beautiful universe and explain

(02:20):
all of it to you. My friend and co host
Orgy can't make it today. As it as usual, we
are very grateful to have Katie usual host of Creature
feature podcast. Katie, thanks again for joining us. Yeah, absolutely,
I am pumped to be on. I guess like the
slimiest episode you guys have ever done. Did you eat
some slimy mushrooms to prepare yourself to get yourself in

(02:41):
the right mental frame. I just kind of licked the
walls of a cave, a random cave, to get myself
in the right mindset. I think everybody out there just
had their stomach turnover that mental imagic key not into
cave cave tasting. I see, Oh well, and I suggest

(03:01):
that nobody out there google cave tasting because you have
no idea what might pop up. But today on the podcast,
we're gonna be taking advantage of Katie's knowledge of biology
to try to bring together two very disparate topics, to
try to unify our desire to understand the whole structure
of the universe, its shape, its form, its history, together
with the things that we see here down on Earth.

(03:24):
You know, a lot of folks write to me and
wonder about whether there are connections between the shape of
the universe on the biggest scale, you know, this cosmic
web with filaments and sheets of stars and the patterns
that we see down here on Earth, or the organization
of the atoms, as if maybe there's some deep structure
to the universe, and it reveals itself on many levels. Yeah,
I love that. I think that they're often seems to

(03:47):
be this parallel between the facets of physics, like the
kinds of behaviors that particles will exhibit and the behaviors
that biological organisms will exhibit. So these patterns that we
see for these you know, inorganic particles will pop up

(04:09):
when you're looking at organic particle organic organisms, and I
just find that so fascinating. It is fascinating because it
hints at something really really deep. If you discover some
basic mathematics about the way the particles organized themselves, and
it also applies to the way sea lions build colonies
and the way that galaxies organize themselves. That suggests that

(04:29):
you've revealed something really really true about the universe, that
there's an organizing principle of play that can unify them.
You know. One of the first people to do this
was Isaac Newton. His theory of gravity could describe not
just the motion of apples falling from trees, but also
the motions of bodies in the heaven. And so to
have this moment where you feel like, oh, I've discovered
something which is true not just about what's around me,

(04:51):
but also about what's in the sky and maybe about everything.
That must have been an incredible moment. Of course, we
know now that he was wrong about everything, but you know,
the idea that you could potentially discover these organizing principles
that work across incredibly distant length scales, because galaxies are
hundreds of thousands of light years across, and particles are

(05:13):
tend the minus twenty meters across, and so to imagine
that you could have rules that describe everything on those scales,
it's very tempting, it's very tantalizing, and I think that's
why people look for these connections, and that's why we're
gonna talk about some of those today. Yeah, even Alan
Turing would sometimes use his incredible genius level skills to

(05:35):
make these connections between things like math and particles and biology.
Like he explored the how animals can have things like
stripes or spots, like these clusters of melanin, and he
worked out this whole kind of model with like the
move randomized movements of particles and sort of using that

(05:58):
as a way to understand and how you could get
a pattern like stripes through the like semi random movement
of say like melanine cells. And it's really it's just
so interesting how deep these things go, like these very
broad mathematical or physics based principles. Yeah, it's like the

(06:19):
universe is a grand experiment and it's revealing the underlying
rules as it plays out, and if you pay attention,
you can spot them here, and you can spot them there,
and you can learn things about galaxies by looking at
things under a log in the forest. The universe is
the world's biggest escape roam. That's exactly. There are clues everywhere,
you know. I was talking to my son about science

(06:40):
fiction movies and he was asking me why I'm so
picky about the science being right, and I was telling
him that it was like a detective movie. You know,
if you get a bunch of clues and they point
you in one direction, and then at the end the
clues didn't make sense or they're not consistent with the answer,
then it feels pretty frustrating and disappointing. And I see
every science fiction movie as sort of like a new mystery,
like what are the rules of this universe? How does

(07:02):
it all come together? What clues are we getting? And
so I want the clues to be accurate and not
just to lead you Australia to be nonsense and you
don't want to like accidentally frame a neutrino for murder
or something. I don't know. They're pretty sneaky, those neutrinos
really weird, pretty suspicious. But you know, there is one
organism which has inspired a lot of strange reactions in

(07:23):
people to wonder whether or not it's intelligent, or whether
or not it's structure reveals something about the nature of
the universe. And this is very weird entity called the
slime mold. And you know, my first interaction with the
slime mold actually came from a listener email. We had
an episode about the book Semiosis, which is a science
fiction novel in which plants organize and become intelligent in

(07:45):
sort of a strange way that's not exactly penetrable by
human intelligence, but you know, they can act and they
can think and they can plan in this novel. And
one listener, Ian Hans Portman, from the UK, wrote to
me and said that it reminded him of one of
his favorite pets, which were slime molds, and would I
be interested in him mailing me some example slime molds

(08:06):
so of course I said, sure, please send me these
crazy creatures via the post, and he did so. He
sent us some slime molds via the mail. Because they're
very hardy, right, they can survive a long time. And
my wife grew them for a while, and then I
think she threw them out and they ended up taking
over our compost bin for a while. So they're out
there now exploring southern California and gobbling up all the

(08:29):
amazing treats that they can find. Wonderful. I'm sure that
won't sort of come back to bide us and say,
a hundred million years. But slime olds are fascinating because
they are these tiny little creatures, but they also seem
to exhibit some form of intelligence, and the way they
organize themselves might provide clues as to where the whole
universe organizes itself. The patterns of slime mold networks might

(08:52):
reveal something which tells us about the structure of the
universe and where all the dark matter is. And I
guess where all the compost keeps Jupiter has been keeping. Yeah,
maybe dark matter is just the compost of the universe,
you know, it's just the universe is recycling would that
make black holes the sort of uh incincreators of the

(09:15):
universe universal garbage disposals. So I was curious if people
had thought about this or understood that there might be
a connection between weird, sticky blobs on forest floors and
the structure of the universe on the grandest scale. So
I went out to our cadre of Internet volunteers and
ask them what they thought about a potential connection between
slime molds and dark matter. So thanks to everybody who participated,

(09:38):
and if you would like to get similarly puzzling questions
via email from me, don't be shy, right to me
two questions at Daniel and Jorge dot com. So before
you hear these answers, think to yourself, what do you
think slime molds might tell us about dark matter? And
I have no idea what slim mode is, but I'm
guessing it might be the movement of dark matter around

(10:02):
the universe, and objects help discus and fluid it is
where it fills in the gaps. I actually don't know
slime molds. I know they can they've been shown to
be able to compute stuff, but what that has to

(10:24):
do with dark matter? I have no idea. I didn't
I didn't expect to expect a question like this. I
have no idea whatsoever slime molds. Uh, no, nothing, I've
got absolutely nothing. Sorry, best I can do these lime

(10:44):
molds and dark matter. I'm all in favor of mixing
up stuff, but I don't see any connection between those two.
Very curious to know what. I have no idea what
slime molds have to do with dark matter, but I
imagine they are growth or something in their molecular constitution
that might be maybe affected by dark matter. I'm not sure.

(11:07):
I have no idea. I have no idea what slime
molds are. When I think of slime, I just think
of the green goo. I'm sure that has nothing to
do with what we're talking about. I don't know what
they say about arma matter. Um. I just know that
they try to map something. I don't do too much,

(11:32):
too many details about it, but it is interesting. How
close can can you get with this with this model?
I don't know. Is there's something about slime molds that
we just do not know, Like it's like the mystery
mold of the universe. It's what holds all mold together.
Ah Man, Maybe it just tells us there's more mystery

(11:55):
here than we really thought there was, all right, So
a lot of confusion in these answers. Not a lot
of people have even heard of slime molds or had
any idea what they might tell us about the universe.
That surprised you, Katie, Yeah, yeah, I mean I love
slime molds, so I feel like everyone should love them
as well. Obviously they are in a way cute. I

(12:16):
suppose I try to find the cuteness in every organism
or I guess like globular cluster of organisms. So yeah,
I really hope people gain some slime mold awareness through this.
I'm glad that you're pro slime mold, that you're really
thinking about what the slimes need. They need human representatives
to really speak up for them, advocates. Yes, our interest

(12:39):
here is not just to think about what the slime
mold needs, but to try to solve the mysteries of
the universe, to think about where in the universe everything
is and how it got there and how we can
learn about it. Yeah. Yeah, I I am really curious
because slime molds are one of the most mysterious organisms
on Earth that their behave year and what exactly is

(13:01):
going on with them is really interesting, and it's relative.
There's a lot of room to explore still, so there's
a lot unknown about them. There are a lot of
studies and a lot of controversy. So I feel like
the fact they are just so already so mysterious, it's
just very intriguing that if we unlock some of these

(13:23):
mysteries of the slime mold, we may be able to
unlock some of the mysteries of the universe exactly. Maybe
slime molder aliens and they're here to tell us the
secrets of the universe. They do look very alien like
in just like they're sort of a blob, a growing blob.
So if that is your image of an alien sort
of a blob, I think there's been a few sort

(13:44):
of be movies where an alien blob comes from outer
space and then consumes people or takes over the world. Well,
I'd love to talk about b movies with blob aliens.
Let's first talk about the structure the universe, where everything
is and where everything isn't because you probably know the
universe is not just the stuff that we see out there.
Of course, there are galaxies and there are stars, and

(14:06):
there are planets, and there's huge clouds and gas and dust.
But that only adds up to about five percent of
all of the stuff in the universe. The rest of
the universe is other stuff, stuff that we do not
understand a huge chunk of that, Like is dark matter
something we know is out there. We know it's matter,
we know it's stuff, we know it has gravity, but

(14:27):
we don't know what it's made out of. And all
that just adds up to about of the universe. The
other seventy percent of the energy density of the universe.
If you took like a cubic light year of the
universe and asked where is all the energy, seventy percent
of that would be in something else called dark energy,
which is accelerating the expansion of the universe, tearing it

(14:48):
apart faster and faster every year. And while we'd love
to dig into dark energy on every podcast because it's
an amazing mystery, today we're focusing on sort of where
is the stuff in the universe? Where is the matter
by which we mean dark matter and normal matter. How
do we even know that dark matter exists? If it's
something that's so mysterious and so seemingly extremely difficult to

(15:10):
like directly observe it. What are the signs that dark
matter exists, Like, is it sort of a negative space
scenario where we are able to see the dark matter
based on the things around dark matter? Exactly, we can't
see dark matter directly. The name dark matter itself is
a little misleading because it makes you think of like
a big dark cloud that would block your vision. But

(15:32):
actually dark matter is more like invisible or transparent matter
because light passes right through it doesn't give off any light,
it doesn't reflect any light. You can't see it directly
using light because it just doesn't interact with photons at all.
And the only way that we can see it is
through its gravitational effects on other things. And so that means,
for example, that it holds galaxies together, because we think

(15:53):
that all galaxies are swimming in these big dark matter
halos that are compressing them and keeping them together as
they spin really really fast. We also know that dark
matter has played a huge role in determining the structure
of the universe, Like why is there a galaxy here
at all? It's because there was a big pool of
dark matter that pulled together all these gas and dust

(16:14):
to form stars. Without dark matter in the universe, that
structure would take a lot longer to form, be like
another ten billion years before the gravity of just the
gas and the dust was able to pull it together
to make stars. So dark matter really has shaped the
universe even though we can't see it directly. So it's
kind of like the invisible hand of the universe if

(16:36):
we want to get all economics about it. But that
is really interesting. Could you, I mean, if you gave
me a spoonful of dark matter, like, could I feel it?
Or would it just sort of destroy me? Would it
start impacting the things around it? Would my office chairs

(16:57):
start to float up and get sucked in around and
are pushed around? What is that sort of physical attribute
of the dark matter? Because my sense of matter is
matter is a physical thing that impacts things physically, whereas
energy differs from matter, and that it's not it's not
like a it is it's hard for me to describe

(17:19):
without the kind of reiterating the physics concepts. Yeah, it's
a great question, but unfortunately, dark matter is not something
that you can like put on your pizza. Dark matter
interacts with you gravitationally, which means that it pulls on you.
It tugs on you gravitationally, but because it doesn't interact
with you using electromagnetism, it passes right through you, the

(17:39):
same way that like neutrinos can. Neutrinos come from the
Sun and they shoot through the Earth and they don't stop.
They don't obey the boundaries of your body or the
walls or the ground because they don't see them. The
universe is transparent to them. They don't have that way
to interact, so they just ignore that kind of matter
and pass right through it. The same is true for

(18:00):
dark matter, which remember, is not out there in the universe.
It's here surrounding us. It's all around us. It's in
this very room that you are in. But if a
piece of dark matter flew right through your brain, you
wouldn't notice, and either would it, because you two cannot
interact except through gravity, which is super duper weak. The
only way we can even know dark matter is there

(18:20):
is when there are enormous, like galaxy sized blobs of
it having gravitational effects on the visible matter. What you
didn't see it was me with a broom trying to
sweep out all the dark matter, as you told me
that it's here with me right now, So like it's
it's scattered throughout the universe. But then you can have
like these big sort of blobs of it as well

(18:41):
that have a stronger impact on their surroundings. Yeah, and
these blobs have an amazing history that really shaped the
whole structure of the universe. If you cast your mind
back to the very very beginning of the universe, everything
was filled with like an even smooth amount of energy.
No spot was any different from any other spot, because like,
why would any spot be special. The universe doesn't have

(19:04):
a center. No location is different from any other location,
so everything is the same. But if everything is the same,
then gravity can't really do anything because it's being tugged
in every direction the same amount. But what happened very
early on was that you've got quantum fluctuations. You know,
pairs of particles were created out of the vacuum just randomly,
energy converted into matter and back, and so some places

(19:25):
were a little denser than others. And then the universe
expanded very very rapidly. So those little quantum fluctuations, which
normally you would never notice, I would have no gravitational
impact got blown up to enormous proportions. The early universe
expansion is like a factor of tend to the thirty.
That's ten with thirty zeros in front of it. Something
used to be like a nanometer is now light years across.

(19:48):
And so then gravity had something to hang onto. You
could say, oh, this spot here is denser than its
neighboring spots. I'm gonna start tugging on those particles. And
that's how structure was formed. It it was the sea
the gravity needed to grab onto. And then you fast
forward some millions of years and gravity has gathered that
together into these huge sheets of dark matter. And where

(20:09):
those sheets overlap with each other, you get even stronger densities,
and those we call filaments. And where those filaments intersect
with other filaments are the most powerful densities. And those
are the intersections where galaxies form. Because you get this
intersection with a lot of dark matter, and it's like
a lake with all the filaments sort of like contributing
to it. Everything is flowing towards the densest spots, and

(20:32):
that's where galaxy is formed. So these sheets and these
filaments of dark matter really have determined the whole structure
of the universe. Well, so we we kind of started
out as a puree and then became like Campbell's chunky
chicken noodle soup. But yeah, that is I mean, even
the way you describe it does sound very biological. Things

(20:52):
kind of coagulating and coalescing and pulling on each other.
It sounds like something like milk curdling, which is really interesting.
So dark matter has this huge impact on the universe.
How do we How have we kind of observed that happening.
It's a great question because dark matter is kind of invisible.

(21:15):
So some of this is a little bit theoretical. Some
of this is like running simulations and saying, if we
put all these rules into the universe, what kind of
universe do we get? Do we get the kinds of
structure that we see today. But of course we'd like
to see the actual structure. We'd like to look out
into the universe and observe how things really are. And
the fascinating thing about these filaments is like connections between galaxies. Right,

(21:38):
Like our galaxy is floating in space and the's another
galaxy nearby Andromeda. But there's not just empty space between
US and Andromeda. There's an invisible filament of dark matter,
but there's also a filament of normal matter. Not all
of the gas and the dust ended up in the galaxies,
a lot of it is actually between the galaxies. And
so for example, like only ten percent of the matter

(22:00):
is in galaxies, Like if you take a random proton
in the universe, only one other ten are in the
galaxy right now. Another fifty percent of them are around
the galaxies, like in a big blob of gas that
hasn't yet fallen in but might soon. And the rest
of it, like of the stuff in the universe, we're
not even sure where it is. It might be in
these filaments between galaxies. Might be that there's huge amounts

(22:24):
of gas lying along these filaments made by dark matter,
but it's hard to tell. It's hard to see these
things because the gas is so faint. That's so interesting.
So we've got like these almost these like tendons or
sort of strings that are connecting these galaxies and but
not not just connecting them, but also influencing the matter

(22:45):
around them by by pulling on it. Can we actually
like when say we got just a really good telescope,
could we actually see these filaments, or would since dark
matter is invisible, would we not really see anything. We
can see them a little bit, but it's very unlimited.
So these filaments have lots of gas in them, and

(23:06):
if the gas is hot, meaning the particles are moving
really really fast, then they emit light. They emit X rays,
for example, and we can see that with our X
ray telescopes, And you might be confused, like, how can
this gas be hot? We're talking about something in deep
space between galaxies or remember that things can be hot,
but they can also be dilute. It's not like hot
in the sense that you could like hang out there
in your swimsuit and have a nice time. You would

(23:28):
definitely freeze if somebody dumped you in these filaments because
there isn't a lot of heat there. But there are
vast moving particles and those emit X rays. So we
have seen these filaments directly. The problem is that it's
hard to see the whole cosmic web using these X rays,
because where at one little spot of it, it's easiest
to only see their really close parts. We'd like to

(23:49):
see the whole map of the universe. Another way we
can look at these is to see how light is
absorbed as it comes to us from things behind these filaments.
For example, quasars are very very bright sources of light.
They are black holes that have swirling gas around them,
and that gas is being squeezed by the tidal forces
of the black hole and heated up to incredible temperatures

(24:11):
and emitting these very very bright pencil beams of light.
And when they pass through the filaments, some frequencies of
light get absorbed based on what's in them. So we
can use this to sort of like X ray these
filaments to say, oh, here's one and it has some
hydrogen in it. Oh, and look it also has some
iron in it. How did that get there? So we
can see sort of the nearest ones using X rays,

(24:31):
and we can have a few like pencil beams through
the universe to give us a sense for where some
of the other ones are, but we don't have a
great way in general to figure out where these filaments are.
That's really interesting, I mean, it seems like basically trying
to detect these filaments, it's like trying to sort of
toss a marble at another marble, like another a mile

(24:52):
away and hit it. So by observing sort of like
how the effect it's having on light as it's passing through.
We can kind of tell a little bit about them. Yeah,
but you need a source of light, You need like
a conveniently placed quasar to show you where these things are.
It's sort of like the way a laser beam in
a dark room will show you where the dust is,

(25:13):
but it won't show you where the dust is where
the laser is not pointing, you know. And so if
you have a few lasers to a room, you can
see where the dust motes are, but most of the
room is still invisible to you. Wow. So we're really
just relying on luck to be able to see any
any sign of these filaments. Yeah, and it's a huge
mystery how much gas is in these filaments. You know,

(25:34):
we're talking about a big chunk of the universe's budget
is like unexplained. And people are used to the idea
that dark matter is sort of like this missing chunk
of the universe and that five percent of the universe
is our kind of matter. Now we're talking about like
of that five percent, not some mysterious form of matter,
but just like normal matter, protons and neutrons. We can't

(25:54):
explain where all that stuff is, like a huge chunk.
But a third of the visible universe, the stuff we're
supposed to understand, is gone missing. This is called the
missing Baryon problem, and so understanding if it's in these
filaments could really help us get a clear picture of
you know, the whole universe. I mean, have we tried
printing out posters with missing baryon call this number reward.

(26:18):
We've tried sending traps, you know, with nice hasty Russian
pizzas on them, but they don't seem interested. So let
me go grab delicious pizza right now. And when we
get back, why don't we talk a little bit about
those slime molds and uh see what they're about. And
now that we've learned a little more about dark matter,

(26:52):
all right, and we are back and I have just
polished off this wonderful slime mold pizza. Actually, no, don't
do that. Don't eat unidentified slime molds. But Daniel, I mean,
you have gotten to know a slime mold personally, so
you've actually had a personal relationship with a slime old.

(27:12):
What did you learn in that relationship with that slime mold?
The listener sent you, Um, I learned the slime molds
are not as slimy as you might expect. You know,
they're one of these weird creatures with multiple stages in
their life that look very different. You know, like how
caterpillars and butterflies are in the same creature, just in
a different part of its life, and slime molds only

(27:33):
are slimy and like one mode of their life. So
sometimes it can look just sort of like a normal
weird blob or like an actual mushroom or something sort
of crawling its way across your countertop. So it's a
little bit underslimed. Yeah. That is one of the most
baffling things about slime molds is they have a life
cycle that's just very confusing, and it's almost like they

(27:57):
turned into completely different sort of organisms throughout their life.
I mean, this is not something unheard of for other animals.
Of course, you know, the first person to see a
caterpillar and then see a butterfly, I would have no
idea this is the same animal. It goes through these
very different stages, and it goes through a crawling stage

(28:19):
and then the chrysalists this immobile, sessile stage and then
a flying stage. So that is must have been very
mystifying for the first people to to see these organisms.
And of course slime molds are also really mysterious, and
we're learning so much about them even now. But yeah,

(28:39):
so the first thing I think to know about them
is that it is not a single organism. It is,
generally speaking, these slime molds that you you will see
like this kind of blob or splat mark is going
to be a amalgamation of a bunch of individual organisms

(29:00):
that are all interacting with each other, like an ant
colony or a b colony, but on a microscopic scale
and smooshed together. So it's like a community you're saying,
not just like a single organism. Yeah, I mean it.
They will have stages in their life where they will
be sort of a single organism, but yeah, the most
of their life, and indeed, like they when we can

(29:24):
actually see this thing that looks like a single organism,
that is a cluster of these single celled organisms. So
they used to be classified as fun guy. You know,
we've talked about the mushroom pizza and everything, but that's
actually a somewhat outdated classification. So now they are just

(29:48):
kind of their own thing. It's a very strange classification
because it is like eight hundred species who are all
sort of loose related phylogenetically, but kind of lumped together
as It's like the extra pile in terms of organisms,
where we try to make these classifications, and now we

(30:11):
have this group of kind of weird those that we
don't know how else to classify them, so they all
get lumped together as slime molds. I mean, if I
just google slime mold, for example, I see a bunch
of interesting things. I see some weird yellow things with
like what looks like veins in them, you know, these
like transport networks. And then also see like weird purple

(30:33):
blobs and weird pink things that look like mushrooms, and
you know some things that just really do look like
gelatinous cubes taking over the earth. You know. So are
you saying this is sort of like a biological frontiers,
not something we really understand how they evolved and how
they're related to, sort of like a grouping of mysterious
objects that are sort of similar to each other. I mean,
I wouldn't say it's completely mysterious. We have I mean

(30:57):
researchers have discovered a lot about them, but it is
a little more of a wild West situation than maybe
some other organisms that we've studied. So basically they are
What we do know is they are eukaryotes like humans, plants,
and animals. These are all eukaryotes, but they are protests.
So a protest is any kind of eukaryote that is

(31:19):
not an animal, plant, or fungus. So it's just basically
we know definitely what they aren't. So we know that
they are not animals, plants, or fungus, so we kind
of give them their own group. But in terms of
figuring out how they are related at each of these
slime old species, you know, that is still a growing

(31:42):
topic of research um And in fact, that a slime
old you google that yellow one probably is the Phicerum polycephalum,
which is that yellow blob. And I think we've actually
shot that species of slime mold into space to see

(32:03):
exactly what is going to happen with it in a
low gravity setting. So do you think that they're going
to land on the Moon and partner with tar degrades
to build the next alien empire? I fear what would
happen if they partnered with tar degrades. So they have
a very strange life cycle. So during one stage of

(32:24):
its life, it's an a cellular organism. So instead of
actually like at least for this phi serum paul cephalum,
so it differs depending on the slime mold, but like
for that specific slime mold, it just has like one
kind of cell that instead of just like dividing into
multiple cells as it grows, it's just like one big

(32:46):
kind of goopy blob. But you know, other types of
slime molds are a group of individual you know, cellular organisms,
and they can really a mass to large sizes. So
some can be up tom and mass and they can

(33:07):
be measured in square meters in size, which is alarming.
Twenty ms. Wow, that's like big enough to tackle somebody.
I mean, has a slime mold ever taken down a person?
I don't think they have, just because they move so slowly.
What about like a cartoonist that was like sleeping in
really late, and do you think it could eat Jorge

(33:29):
if he was not paying attention? I think maybe, Yeah,
Jorge was staying up late at night finishing a cartoon
and kind of slept in. Maybe all right, well, let's
hope somebody warns him. That's why you set alarm clocks
so your local slime mold won't devour you as you
sleep in. So I think slime molds are fascinating because
they have these weird life cycle and biologically they're really interesting.

(33:50):
But also they seem to be able to like to
do things. And you talked about slime molds at these
individual entities which sometimes come together to act communally, And
it's amazing to me when they can do things as
a group that an individual couldn't do. Some example, these
things like learning. Yeah. Yeah, So they can either live
freely or they will join together to form a multicellular aggregate.

(34:14):
And this is where, yeah, it gets really weird and
really interesting. So like there have been multiple studies to
see how they act as a group. I mean, you know,
when you think about something like an ant colony and
you leave a piece of food out, the ant colony
is going to sort of act as a group. They'll
form these lines of ants guided by pheromones to go

(34:37):
pick up this food. But we can still kind of
see these individual ants for sly molds when they get
together they're so small. What we're seeing is basically a
blob or a slug seeming to act as one organism,
even though it's made up of many individual organisms. So
they will sometimes when they detect food, they will come

(34:59):
to other and kind of act together as if they
are a single organism. And there was actually a study
that was done that was like kind of trying to
see like whether slime old could figure out how to
get to food, and they would put these little oat

(35:21):
flakes around in a little dish with the slime mold,
and the slime wold was able to relatively efficiently figure
out how to um get to these oat flakes, and
it actually somewhat resembled like the Tokyo train system because

(35:43):
it was finding out roots to the oat flakes in
a relatively efficient way. I think that's super fascinating and
that connects to the idea we were talking about at
the top of the episode about having similar mathematical problems
on different scales. You know, people want or like how
could a slime mold replicate the Tokyo rail network? What

(36:03):
does that mean? Well, think about like how you build
a rail network. You want it to be efficient, you
want to be able to get from one place to
the other with a minimal number of connections and the
shortest distances. So you build this network between your cities
and the slime mold, it seems like it's sort of
solving a similar problem. It's like, if I have food
in these locations, then where should I build my connections

(36:23):
between them so I can most efficiently move my nutrients
around and get my cells from one food source to
the next. You know, where should I focus my energies.
And it's amazing that the network that comes out of that,
if you place like the oats in the same structure
as like the Japanese cities, that it basically replicates the
Tokyo rail network because it suggests that it's solving a

(36:43):
mathematical problem, not like it's got a little chalkboard in there,
but that effectively it's doing computing. You know, what is
a computer other than like a physical representation of a
mathematical problem. You get the universe in terms of transistors
or whatever to solve a problem you've represented symbolically. And
that seems like that's what the slime mold is doing.
It's like basically doing slime mold computing. It's solving this

(37:06):
optimization problem. Yeah. Actually, some researchers are interested in studying
whether it could be used to build like a bio
computer and use the slime mold to form these logic
gates in a biocomputer, so instead of using you know,
a circuit board, you would have a gooey, living sort
of bioboard. Yeah, you can form computers out of all

(37:29):
sorts of stuff. You know, people think about computers as
like transistors and switches flipping, and that is one way
to use a computer, one way to design a computer.
But any time that you build something which solves a
math problem where you're using the physical universe to represent
your problem again an answer effectively, that's a computer. And
so yeah, you could represent a computational problem as a

(37:51):
challenge for a slime mold where the answer is how
the slime mold builds its network, which is pretty cool.
I also really like these studies that show that slime
molds can like learn, and remember they had these experiments
where they were basically torturing slime molds every ten minutes
on the hour. They would like cool it downs. It
was uncomfortable for the slime molds and the slime wolds

(38:11):
would like react to that, and then when they stopped
doing it, they took a break. The slime molds anticipated
it anyway, They were like, oh, is it going to
get cold? And they reacted before the cold snap would come.
Would suggest that they have like some internal clock or something,
some way to keep track of time and anticipate what's
going to happen based on what's happened to them before.
That's incredible to me. Yeah, that's absolutely so strange because

(38:36):
it is a question of exactly how do they store
that kind of data, right, Like how are they storing
this memory of the cold snaps? And I don't mean
memory in terms of like a human memory like thinking
back to something, but how a computer might store memories.
So it is really it's spooky, it's really strange, And

(38:58):
I think comparing it to accume puter is so apt
because at this point, in terms of how we've developed computers,
computers don't probably have a sort of conscious understanding or
or a cognitive system like It's AI is still a
pretty distant goal at this point. And so sometimes these

(39:18):
slime olds will do things that make it seem like
they are behaving in this very like conscious way or
even altruistic way, but then when you look at the
mechanisms behind it, it's actually this weird just probability maths.
So slime olds like this study you mentioned with the

(39:40):
researchers just torturing them when they are behaving as a
collective as that mass, they will try to avoid hostile
environments and get out of it. And one way they
can do that is they will actually, like if they
are on an environment and they want to kind of
make sure that there's spores will be able to get

(40:02):
to another place, they will form a slug and then
that slug will stop somewhere and then will grow a
stock like a plant, and then form like a fruiting
body at the end that releases these slime old spores
that can then go colonize another area. And it seems

(40:24):
like the because it remember this is made out of
a bunch of individuals. The ones that are like on
the base of the stock or forming the stock, the
ones that are not at the fruiting body that get
to release their spores. It seems like they are sacrificing
for their comrades to be able to get to the
tops where they can release their spores, but in fact

(40:48):
they are probably not acting altruistically. It is simply sort
of a probability distribution where they are all trying to
climb up to the top, and only some can reach
the top. But as they are all collectively trying to
make this climb, they happen just by the sort of

(41:08):
the the probability distribution of how these slime molds are
going to stack up they form the stock and this
fruiting body, and it's just it's purely math. There's no
slime mold cooperation or camaraderie going on. What is it
like to be a slime mold? Will never know, but
it's amazing that they have something that seems like an intelligence,
ability to learn, to remember, to anticipate, though they have

(41:31):
no central processing unit. There is no brain to these things.
As you say, It all just emerges from the operations
of these individual entities following local rules. That's really incredible
to me. So let's take another break and we get back.
We'll talk about how slime molds and the slime mold
computing problems that they solve might give us a clue
about the whole structure of the universe and where the

(41:54):
dark matter is I have to hear this. All right,
we're back and it was my turn to go off
and polish a pizza. But I imagine that I'm getting

(42:14):
over here in southern California are not really as you know,
amazing as the ones you get over there. How far
are you from a really excellent pizza if you want
to go from zero to pizza Katie, how long does
it take you? Well, there's a really good, like for
catcha pizza place that's maybe a like five minute walk
for me, and then yeah there's and then there's another
just traditional pizza place that's maybe a seven minute walk.

(42:37):
Uh so yeah, you know what, if you're a human
and you want to live the slime old life of
trying to find the shortest distance between two points, finding
out a walkable city is a way to go because
you can just walk right to a pizza place. If
I live there, then I think the map of my
walking around with follow the slime old map of the city.
You know, the efficient paths between pizza joints. Yeah, your

(42:58):
your oat flakes would be all the pizza joints around here. Yeah.
So we've been talking about the mystery of the structure
the universe. Where is some of the missing stuff in
the universe, the normal matter, the protons, the neutrons, the electrons,
A lot of that might be between galaxies, but we
can't see it directly. We also suspect that there are

(43:19):
filaments of dark matter, these tendrils between galaxies that feed
new matter into the dark matter haloes and connect us
and show us sort of the history of where things
split apart, but we can't see them directly. And now
we have, on the other hand, this sort of slime
mold computer that lets us think about networks and how
to build them efficiently. So you might be wondering, like,
what do these things have in common? There were some

(43:41):
researchers in Santa Cruz I had an idea for how
to use slime molds to build a map of these tendrils,
these cosmic filaments. The idea actually starts with galaxies. You know,
if you want to know where the filaments are, you
want to know where the connections are between galaxies. Instead
of looking for the filaments directly, why not just look
for the galaxies because galaxy are something that we can see.

(44:01):
Galaxies are like the nodes of this network, right, we
can see them because they generate a lot of light.
They have billions and billions of stars in them. We
could see them across the universe. And there's a huge
number of galaxies, right, quasars that we used to see
the filaments when they shoot these like pencil rays of
light and we can see them highlighting the filaments. Those
are pretty rare. There aren't that many quasars in the universe.

(44:24):
But galaxies are goodness because if there were too many quasars,
that would mean a bunch of black holes that we
would all get be getting sucked into. Yeah, an incredible radiation.
But you know, if you hold up your finger, then
like the size of your finger nail, for example, the
size of your fingernail has like a million galaxies behind
it just in the observable universe. Like if the universe

(44:47):
is infinite, there's an infinite number of galaxies behind it,
but just in the part that we can see. If
you like focused hubble on that one spot in the sky,
there'd be a million galaxies each with hundreds of billions
of stars. You know, it's just it's mind boggling the
hole this in your mind, but it's a really good
way to get a sense for what the network is.
It's like asking, we want to know where the trains run.

(45:08):
Why don't you start out by looking for the stations
and then figure out where the trains run in between
the stations. Just don't stand in between the stations on
the railroad tracks with your camera because that's probably not
a good idea exactly. So that's the easy part is
to figure out where the galaxies are. We spend a
lot of time looking at galaxies. We have big catalogs

(45:28):
of where galaxies are. But these folks are wondering, well,
if you know where the galaxies are, does that tell
you necessarily where the filaments are. You can't just draw
a line between every pair of galaxy. You'd have like
lines everywhere, Right, These filaments tend to cluster together places
of larger mass. These filaments tend to form between the
larger clusters of galaxy, and they form between the neighbors.
There's a bit of an optimization problem here, right, Like

(45:50):
how do you find the filaments? You need to explain
the galaxy clusters that we have. You can't just spread
them everywhere. And so folks have this idea. They're like,
maybe we need to use slime mold computing to find
out what is the optimal way to place filaments between
the galaxies that we can see to figure out where
those filaments probably are. So in order for that to work,

(46:14):
the filaments, the dark matter filaments would have to have
some kind of behavioral similarity to slime molds. So filaments
have that push, pull, attraction and repulsion sort of characteristics.
And is that sort of the connection with slime old.
So if slime old has like an attraction to food

(46:37):
and uh, sort of a wanting to avoid scientists trying
to torture it, what are sort of the analogous behaviors
of dark matter filaments. Well, it's all gravity, right. Dark
matter creates those galaxies where there is more dark matter,
then you get more dark matter halos and you get
more bowls for galaxies to form in. So there's a

(46:58):
tight connection between where the filaments are and where the
galaxies formed sort of like support and encourage and create
each other. So that's the push, right, They helped create
each other, and there's also a pull they pull on
each other. They sort of like tug on each other
to make each other more compact. And so instead of
just like spreading out in every direction. The dark matter
pulls itself into these halos and into these filaments between them,

(47:21):
and so that's why it's sort of like a push
and a pull, as you say, like an optimization problem.
You can't just spread out everywhere. You need to figure
out like what is the best arrangement of dark matter?
If I give you some dark matter, how would you
sprinkle it around the universe to create the galaxy map
that we see. What's the best place to put it?
And so they discover that slime bolds could help us
figure this out if they turn this like dark matter

(47:44):
filament problem into a food problem. So they did this,
of course in simulation. They didn't use real slime molds,
So they didn't put a pile of slime mold next
to a powerful telescope and say, what do you think?
What would you guys do? You guys are in charge?
Tell us where to look? And that's scenario. What would
how would you behave? So what they do is they
put blobs of simulated the slime mold where they see

(48:06):
the galaxies, and then they simulated slime molds send out
tendrils in every direction and if it finds another galaxy,
then it strengthens that connection. And so this is the
part where it's like simulating how a slime mold explores
its space. It's sending out tendrils and looking for stuff,
and when it's successful, a slime mold will build a
stronger network. That's how it replicated, for example, the Tokyo

(48:27):
train map. And so in the universe, these simulated slime
molds start from galaxies and when they find other galaxies
and they like enhance that connection between them. So there
must be more of a filament here. So they're not
actually modeling like the real physics of dark map. They're
like saying, if you had a stimulated slime mold and
you put in this artificial problem, would it solve that

(48:48):
problem effectively? Can you use slime mold computing to figure
out where the filaments should be? What are the benefits
of trying out sort of a slime mold model versus
modeling physics. Is it that having some kind of physics model,
we're still asking the questions that we would need to
be able to make a physics model. At this point.

(49:09):
You can do it with physics as well, but it's
difficult because you don't know what the initial conditions are. Like,
what we can do with physics is we can say,
let's say we had a random universe and let's run
a simulation of that and understand how the particles interact
and how gravity works. What do you get? And you
get a universe with tendrils and galaxies, but you don't
get our universe, right, that's a different random universe. So

(49:31):
because we don't know what the initial conditions of our
universe are, it's hard to run that simulation and so
you could like try to run it backwards. So this
is just like an alternative approach to say, like, maybe
we can find a shortcut, a clever way to solve
this problem using ideas from slime molds so that we
don't have to figure out how to run the universe backwards. Man,
slime molds are so smart. They're teaching us about about physics.

(49:54):
It's so interesting and mind blowing to me because with
slime molds, when we talk about their intelligent it is
not the kind of intelligence of a researcher sitting there
programming this, uh, this mimicry of for the slime mold.
It's just the the intelligence of a pattern of like

(50:15):
individual particles. Let's let's just call one of the unicellular
organisms like a particle doing a behavior. What gets even
more kind of like Russian nesting dollars. You look at
that individual, uh unicellular organism, and it is also basically
just a domino effect of particles colliding with each other

(50:36):
and interacting so like molecules setting off other molecules. And
then that's how that unicellular organism is able to move around.
And then you zoom back out, and then many of
these unicellular organisms such just it almost makes my eyes
crossed just thinking about how many complex like basically little

(50:56):
little individual units bonking into each other many many times,
and how that can create such incredibly complex and seemingly
very intelligent behavior. Yeah, the same way that like a
computer can seem intelligence can do complicated things, but at
the lowest level, it's just following very simple rules about
flipping bits from zeros to ones. And of course we

(51:18):
don't know if consciousness could arise from that kind of system,
and we also don't know why intelligence and consciousness does
arise from our biological system, which in the end, it's
just a bunch of neurons zapping each other. So there
is really a deep mystery there about the connection between
the underlying rules and the emergence of consciousness. But I
think it's really cool and you can take advantage of
that and say like, well, let's model these systems. Let's

(51:41):
figure out what they're doing, and see if we can
use that to solve this other problem. And it's awesome
to see the connections between problems on the cosmological scale,
like the filaments between galaxies and how the universe formed
and how this weird GROOPI thing crawls across the forest floor.
It really suggests that there are some mathematical connections that
they're the problems are similar in some deep way. In

(52:03):
the end, the galaxies and the slime molds are both
just solving and optimization problem to figure out what's the
best way to hang together. I mean that makes me
feel kind of more I guess connected to the universe,
where you know, it's not the way that these galaxies
are behaving, it's it's similar to how something is seemingly simple,
as like the slime mold that we can find licking

(52:26):
the walls of your local cave or maybe not, maybe
don't do that has not been cleared by our legal department.
By the way, do not endorse cave looking here at
your own risk. I mean there are many they're like
splunking in cave looking are both only activities for highly
trained individuals, exactly. Professional cave liquors were used for this

(52:48):
podcast and folks, But even these slime molds have taught
us something about the nature of the universe. These guys
ran this simulation and they now have a map of
these cosmic filaments between the galaxies. And what they did
is then they turned Hubble to one of these locations
where they thought, maybe here's a cosmic filament. Our slime
mold simulation tells us that should be there, and they

(53:10):
were able to see little hints of X rays emissions
from what was otherwise deep empty space. So they found
new filaments using this simulation. So if they get a
Nobel prize, is that going to go to the slime
mold or to the researchers who ripped off the slime
molds mathematical model. Well, you know, in the great history
of professors taking advantage of their students, I think will

(53:31):
probably just toss him a few oat flakes and assume
that that's enough. But this is a deep mystery in
the universe, not just where are the filaments, but where
is all the missing stuff? And so understanding where these
filaments are might give us a clue is to like,
where those missing particles are. Are they really stretching between
the galaxies what seems like otherwise empty space. Is there
really a third of all the normal matter in the

(53:52):
universe in these long bands between galaxies. It would be
incredible to discover that a whole third of the pie
is really there and what we otherwise thought was deep
empty space. I mean, that makes me feel good, warm
and fuzzy. It's like we're holding hands with other galaxies.
It's not just just cold empty nothingness. We're all just

(54:13):
part of the big galactic slime mold. Ah. That's gross,
all right, So thanks everybody for joining us for this
fun conversation about the structure of the whole universe and
how it's creeping along the forest floor of the cosmos,
as well as the mysteries of slime molds and how
we can take advantage of them to understand the questions

(54:33):
of the universe. And thanks Katie for coming along and
telling us about your cave looking habits. Yeah. Absolutely, I
hope people have an appreciation for even the slimiest, moldiest
pritters out there, because maybe they contain the keys to
the universe. And it never ceases to amaze me how
is even possible for us to understand the universe at
any scale, especially at these largest scales, using the tiny

(54:56):
little networks encased in our skulls. And so I'm glad
that our slime mold brethren have come to help us
in that great cosmic detective mystery, the escape Room of
the Universe. Is that just your way of saying everyone's
got slime for brains? I mean, you ever tasted brains,
They're pretty slimey. Alright, Thanks everybody for joining us. Tune

(55:20):
in next time. Thanks for listening, and remember that Daniel
and Jorge explained. The Universe is a production of I
Heart Radio. For more podcast for my Heart Radio, visit
the I Heart Radio app, Apple Podcasts, or wherever you

(55:40):
listen to your favorite shows.