Slime mold is quite the creature. It has no brain and yet it can spread and hunt for food. It is made of a collection of unicellular organisms that, if cut, will fuse back together. If this wasn’t extraordinary enough, now slime mold is helping cosmologists understand the universe.
Slime mold builds complex filamentary networks to seek out food using near-optimal paths. Cosmologists have found that these structures are incredibly similar to the cosmic web, the expected distribution of dark and regular matter in the universe. The work is published in The Astrophysical Journal Letters.
Galaxies are usually found at the nodes of the cosmic web, and filaments have been traced and studied over the last few decades. The main issue is that they are made of dark matter and gas so diffuse that it might as well be invisible. Understanding the full structure is difficult enough, and when surveys of tens of thousands of galaxies are considered, the task becomes even more so.
This is where slime mold comes into play. Simulations based on slime mold behavior allowed the researchers to determine how the filaments of the cosmic web should spread from one galaxy to the next.
"It's really fascinating that one of the simplest forms of life actually enables insight into the very largest-scale structures in the universe," lead researcher Joseph Burchett of the University of California Santa Cruz, said in a statement. "By using the slime-mold simulation to find the location of the cosmic web filaments, including those far from galaxies, we could then use the Hubble Space Telescope's archival data to detect and determine the density of the cool gas on the very outskirts of those invisible filaments. Scientists have detected signatures of this gas for several decades, and we have proven the theoretical expectation that this gas comprises the cosmic web."
The idea came to team member Oskar Elek, a computational media scientist at UC Santa Cruz, after he found the work of Sage Jenson, a Berlin-based media artist, on slime mold. Jenson based his digital work on an algorithm that simulates how slime mold grows, and Elek developed a 3D version that can be applied to galaxies.
By looking at the distribution of galaxies, human eyes can almost see how the web should be shaped, but algorithms so far have required a lot of effort to come close to that. The slime mold simulation does this work in minutes. As more and more surveys measure the distances and positions of more and more galaxies, an approach like this will be even more useful.