The universe is interconnected.
All the galaxies are literally linked by an
unimaginably huge but almost invisible structure
called the cosmic web.
Scientists are trying to map the shape of
the largest thing in the universe, and as
you might expect, it’s proved challenging.
So to speed up the process, some researchers
wondered what would happen if they imagined
the cosmic web was made by slime mold.
Now, I realize that for some of you the existence
of the cosmic web is news, and you may be
wondering why it exists at all.
A concept I’m sure you’re familiar with
(because we have mentioned it once or twice
before) is dark matter.
Dark matter accounts for around 85% of the
mass of the universe, yet, because it doesn’t
interact with regular matter in any other
way we know of, it’s impossible to detect
at this time.
We know it’s there, though, because its
gravitational pull must be what's holding
galaxies together.
Dark matter can be thought of as a kind of
scaffolding.
Where its own gravitational pull causes it
to coalesce,
 it will also draw in gas and dust.
Draw enough of it in and you can form stars.
Draw enough stars together 
and you can form galaxies.
And up and up it goes.
Galaxies can be organized into clusters, and
those clusters can group into super clusters.
Zoom out far enough, and the shape dark matter
congealed in looks like a road map of the
universe, with large groupings of stars concentrated
where the most dark matter is, and thin filaments
stretching between them
connecting them all.
Of course, finding exactly where those filaments
are isn’t easy.
They’re made of dark matter, which as we
already covered is currently impossible to
spot, and the gas these filaments attract
doesn’t have the mass to form stars; instead
it only has a faint signature as it absorbs
and re-emits light from other sources.
So, even though we’ve known about the cosmic
web since 2008, we only first saw more than
a single filament of its structure 
as recently as 2019.
To make finding the filaments easier, scientists
at UC Santa Cruz (go banana slugs) 
decided to think outside the box and test how slime
mold would behave if its goal was to connect
all the galaxies in the universe.
I know it sounds bizarre, but this actually
isn’t the first time this particular species
of slime mold, Physarum polycephalum, has
been used to create maps of existing structures.
Researchers published a study where they had
laid out oats on a map of several countries.
Each pile of food was placed
on a major population center.
They then allowed the slime mold to grow on its own.
As a colony of single-celled organisms, slime
mold relies on each other to share nutrients,
so setting up optimal paths between food sources
is key to their survival.
In this experiment, they spread out across
the map and when they found a pile of food,
they created routes to transport nutrients
that were remarkably similar to the existing
highways we humans have built.
So, if it worked for replicating how humans
connected cities, why not try it for connecting
the stars?
Of course, stars are arranged in three-dimensional
space, so a petri dish of agar and some oats
isn't going to do it.
Instead, the scientists used an algorithm
that mimics how slime mold grows, and they
arranged the “food” in three dimensions
on where we know galaxies are.
When they ran the algorithm, it came back
with a complex map of where it thought slime
mold would create networks.
That’s all well and good, but the question
is, does this method really work?
Will this tell us where to look for filaments
of dark matter and gas?
To check their results, the researchers went
back and compared their mold map
with data from Hubble.
And sure enough, wherever their model predicted
there would be dark matter, 
they saw a gas signature.
The researchers got their idea of using this
slime mold algorithm after seeing the work
of an artist who used the same algorithm to
make dazzling 3D images.
It’s pretty incredible that two very unrelated
fields came together to produce these results.
I told you the universe was interconnected.
Is slime mold... growin' on ya?
Maren has another video on the topic here.
Let us know if you like this video in the
comments below, and subscribe to Seeker for
your slime mold news.
Thanks for watching and I'll see you next
time.
