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.