By performing supercomputer simulations of the Universe, researchers have shown that the causal network representing the large-scale structure of space and time is a graph that shows remarkable similarity to other complex networks such as the Internet, as well as social and biological networks. A paper describing the simulations in the journal Nature's Scientific Reportsspeculates that some as-yet unknown fundamental laws might be at work.
"By no means do we claim that the Universe is a global brain or a computer," said paper co-author Dmitri Krioukov, at the University of California, San Diego. "But 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."
For the simulations, the researchers found a way to downscale the space-time network while preserving its vital properties, by proving mathematically that these properties do not depend on the network size in a certain range of parameters, such as the curvature and age of our Universe.
After the downscaling, the research team performed simulations of the Universe's growing causal network. By parallelizing and optimizing the application, the researchers were able to complete in just over one day a computation that was originally projected to require three to four years.
"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," said Krioukov, who believes the findings have key implications for both science and cosmology.
"The most frequent question that people may ask is whether the discovered asymptotic equivalence between complex networks and the Universe could be a coincidence," he explained. "Of course it could be, but the probability of such a coincidence is extremely low. Coincidences in physics are extremely rare, and almost never happen. There is always an explanation, which may be not immediately obvious."
Such an explanation could one day lead to a discovery of common fundamental laws whose two different consequences - or limiting regimes - are the laws of gravity (Einstein's equations in general relativity) describing the dynamics of the Universe, and some yet-unknown equations describing the dynamics of complex networks.