(Burchett et al., ApJL, 2020)
11 MARCH 2020
Astronomers have used an algorithm based mostly on the expansion patterns of slime mould to map one thing that is mainly not possible to see: the cosmic net of gasoline and darkish matter underpinning the very construction of the Universe.
That’s as a result of, regardless of appearances, this brainless organism – or relatively the way in which it grows outward in branching networks of slimy tendrils – is able to ‘fixing’ spatial issues which might be really extremely advanced from a computational perspective.
Just how huge does slime mould dare to dream, although? Well, the reply is “pretty big”. In new analysis led by astronomer Joe Burchett from UC Santa Cruz, scientists discovered P. polycephalum‘s exploratory instincts stand to assist remedy one of many grandest unknowns in astrophysics.
(NASA, ESA, and J. Burchett and O. Elek – UC Santa Cruz)
Above: The slime mould mannequin’s 3D map of the cosmic net’s filament community, with insets displaying galaxies (yellow) and algorithmically generated filament strands (purple).
“Modern cosmology predicts that matter in our Universe today has assembled into a vast network of filamentary structures colloquially termed the ‘cosmic web’,” the authors write of their new paper.
“Because this matter is either electromagnetically invisible (i.e., dark) or too diffuse to image in emission, tests of this cosmic web paradigm are limited.”
In different phrases, how can we attempt to experimentally visualise this gigantic, unseeable cosmic net that serves because the scaffolding of all the Universe, given it consists of invisible darkish matter or wispy gasoline filaments which might be tough to make out on our scopes?
This was by no means actually an issue for slime mould. Until it was.
One of the UC Santa Cruz workforce, computational media researcher Oskar Elek, was impressed by the work of German media artist Sage Jenson, who had created inventive simulations based mostly on P. polycephalum‘s foraging behaviour.
The researchers took Jenson’s 2D mannequin and recreated it in three dimensions with extra modifications. They then fed the algorithm a dataset of the coordinates of 37,000 galaxies in what’s referred to as the Local Universe, and the slime mould mannequin did its factor: becoming a member of the dots like all the time, however this time on a celestial scale, giving us a digital, optimised reconstruction of what the cosmic net may really appear like.
“The galaxies effectively serve as ‘food’ sources for a swarm of virtual ‘slime mould’ agents released into a 3D space defined by the celestial coordinates of each galaxy,” the researchers write.
“The agents continually move through space and eventually reach an equilibrium state, tracing an approximate optimal transport network from galaxy to galaxy.”
Of course, the 3D map the algorithm generates is just a contrived simulation – not a agency proof of the place the cosmic net’s darkish matter and gasoline filaments really reside on the market in house. Nonetheless, it may very well be our greatest approximation, the researchers say, they usually have at the very least some proof to again that declare up.
While it might in all probability be not possible to validate all the cosmic net reconstruction, spot checks evaluating the slime mould’s filaments with legacy Hubble information on hydrogen gasoline places recommend the algorithm’s community is correct.
“We knew where the filaments of the cosmic web should be thanks to the slime mould, so we could go to the archived Hubble spectra for the quasars that probe that space and look for the signatures of the gas,” Burchett says.
“Wherever we saw a filament in our model, the Hubble spectra showed a gas signal, and the signal got stronger toward the middle of filaments where the gas should be denser.”
Should we be stunned that one thing as fundamental and lowly as slime mould intuition might help level us within the path of cosmic buildings which have in any other case eluded scientific discovery? Well, sure and no, the researchers say.
“It’s somewhat coincidental that it works, but not entirely,” Burchett explains.
“A slime mould creates an optimised transport network, finding the most efficient pathways to connect food sources. In the cosmic web, the growth of structure produces networks that are also, in a sense, optimal. The underlying processes are different, but they produce mathematical structures that are analogous.”
In any case, the findings may present us with a wholly new manner of understanding the buildings of the cosmic net, and largely because of the existence of slime mould. We are all within the gutter, it appears, however a few of us are trying on the stars.
“For the first time now, we can quantify the density of the intergalactic medium from the remote outskirts of cosmic web filaments to the hot, dense interiors of galaxy clusters,” Burchett says.
“These results not only confirm the structure of the cosmic web predicted by cosmological models, they also give us a way to improve our understanding of galaxy evolution by connecting it with the gas reservoirs out of which galaxies form.”
The findings are reported in The Astrophysical Journal Letters.