Astronomers have found an uncanny resemblance between two very different sets of networks: one crafted by biological evolution and the other crafted by the primordial force of gravity in the universe.
The researchers used slime mold to map the largest structures of our universe. This was done with the help of one of nature’s humblest creatures, and data gathered by the NASA/ESA Hubble Space Telescope.
Single-cell organisms known in the scientific world as Physarum polycephalum—slime mold—can build very complex web-like filamentary networks during their search for food, always discovering a near-optimal pathway that allows them to connect two distant locations.
Curiously, astronomical studies of the cosmos have found that in shaping the universe, gravity seems to do the same thing, as it builds up a vast cobweb-like structure of filaments which ties galaxies and galactic clusters together with the help of “invisible” bridges of gas and dark matter that are hundreds of millions of light-years across.
In other words, just as the simplest organisms on Earth create complex pathways and structures, so do much higher forces in the universe build a network of structures that connect our galactic neighborhood through a behemoth cosmic web.
So, what exactly is a cosmic web? Basically, the cosmic web is a massive backbone of the cosmos and is made up mostly of dark matter, and laced with gas upon which galaxies are then birthed. Despite the fact we can’t really observe dark matter, astronomers believe that this strange substance makes up the bulk of the universe’s material.
However, since the gas within these elusive strands is so dim, astronomers have struggled to find them.
Nonetheless, the existence of a web-like structure was first suggested after astronomers surveyed galaxies in the 1980s. Since then, astronomers have made great progress in understanding the universe and what constitutes it. Forty years later, astronomers have revealed the genuinely gigantic scale of the filamentary structure.
The filaments are thought to form the boundaries between massive voids in the cosmos.
To better understand this complex structure, scientists decided not to search the universe, but turn to organisms on Earth. Astronomers studied slime mold to help them create a map of the filaments of the local universe and discover the traces of gas between them.
Astronomers first created a computer algorithm that was mostly inspired by the behavior of slime mold. They then fused two very different networks: one crafted by biological evolution and the other crafted by the primordial force of gravity and tested it against computer simulation of the growth of dark matter filaments in the universe.
Scientists applied the slime mold algorithm to data featuring the location of more than 37,000 galaxies that were mapped previously by the Sloan Digital Sky Survey. This allowed experts to craft a three-dimensional map of the underlying cosmic web structure, in a unique, never-before-seen achievement.
Researchers then proceeded in analyzing the light emitted from 350 distant quasars cataloged in the Hubble Spectroscopic Legacy Archive.
These distant cosmic flashlights are the brilliant black-hole-powered cores of active galaxies; their light shines across the vastness of space and manages to do so even through the foreground cosmic web.
It was there, precisely in that light where the telltale signature of otherwise invisible hydrogen gas was found. This allowed astronomers to analyze specific points along the filaments.
These target locations are far from the galaxies, which allowed the research team to link the gas to the Universe’s large-scale structure.
“It’s really fascinating that one of the simplest forms of life actually enables insights into the very largest-scale structures in the Universe,” explained lead researcher Joseph Burchett of the University of California.
“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 over half a century, and we have now proven the theoretical expectation that this gas comprises the cosmic web.”
The study will appear in the Astrophysical Journal Letters.