“Some part of our being knows this is where we came from,” says Carl Sagan at one point during his epic cosmology-narrating documentary, Cosmos. “We long to return. And we can. Because the cosmos is also within us. We’re made of star-stuff. We are a way for the cosmos to know itself.”
I remember reading that second-t0-last sentence somewhere as a kid before I’d even seen the show in the 1980s. “Star-stuff,” an economic, deeply poetic way of driving such an elegant point home. It was mind-blowing to me at the time, back in grade school, just beginning to wrap my head around how scientists thought the puzzle pieces fit together.
But what if it turned out that what we’ve become over the course of evolutionary eons is about more than just the elemental stuff that stars and planets and nebulae are made of? What if the very structure of our brains, as well as the things our brains can lay claim to — constructs like the Internet, social networks, etc. — resembled the underlying structure of the universe itself?
That’s what a recent study published in the science journal Nature’s Scientific Reports suggests — that not only are we star-stuff, but that there may be a kind of cosmic feedback loop in the design of our brains and what we’ve created using them.
“By no means do we claim that the universe is a global brain or a computer,” said Dmitri Krioukov (via UCSD News), one of the paper’s co-authors and a senior research scientist at the University of California, San Diego. (He’s also the guy who, back in April, successfully appealed a failure-to-stop traffic ticket by writing a four-page research paper that suggested, using basic high-school math, why he wasn’t guilty as charged.)
But while the paper isn’t an attempt to describe the universe as some sort of vast, cosmic intellect, Krioukov says brain-universe parallels exist: “[The] discovered equivalence between the growth of the universe and complex networks strongly suggests that unexpectedly similar laws govern the dynamics of these very different complex systems.”
Start with complex networks, notoriously thorny when it comes to sussing out stuff like prediction and control, i.e. guiding a dynamic system from one state to another in a given amount of time. According to Krioukov and his fellow researchers, “Structural and dynamical similarities of different real networks suggest that some universal laws might accurately describe the dynamics of these networks.”
The problem? Figuring out the nature and origin of those laws.
So the research team ran supercomputer simulations of the universe (approximations, obviously — the universe may be infinite, so forget simulating that) and discovered, to their surprise, that the causal network representation of space-time in an accelerating universe was unexpectedly similar to the structure of complex networks like the Internet, social networks — even our brains.
The implications for network science and cosmology are significant, says Krioukov: “We discovered that the large-scale growth dynamics of complex networks and causal networks are asymptotically (at large times) the same, explaining the structural similarity between these networks.”
How big is the universe in mathematical terms? According to the research team, no smaller than 10250 atoms of space and time (so big enough to fill a piece of paper with a one followed by 250 zeros). They had to scale that number down for computational reasons before running their causal network simulation on a supercomputer housed at the San Diego Supercomputer Center (SDSC) and named Trestles, sporting 10,368 processor cores, a peak speed of 100 teraflops per second, 20 terabytes memory and 39 terabytes of flash memory.
Even still, the original projections put the simulation at three to four years of runtime. The research team managed to dramatically speed this process by parallelizing and “optimizing” the simulation — so much so that they were ultimately able to run the whole thing in a day.
“In addition to being able to complete these simulations much faster than previously ever imagined, the results perfectly matched the theoretical predictions of the researchers,” said Robert Sinkovits, a computer scientist with SDSC.
But couldn’t these results — the unexpected similarities between complex networks and the universe — just be a coincidence?
Sure, says Krioukov, but notes the likelihood of this is “extremely low,” adding “Coincidences in physics are extremely rare, and almost never happen. There is always an explanation, which may be not immediately obvious.”
If they’re not coincidental, then the study could mean we may eventually discover some universal way of explaining how complex systems work — a common denominator for describing the behavior of complex networks, our brains and the universe itself.