Networks: The brain, the internet, and the cosmos
I was completely captivated by something David Deutsch said in a TED talk in 2005. This particular observation was not the theme of his talk. But I found the language he chose to describe the working model of the universe (that physics and mathematics have provided) to be loaded with implications about human knowledge, even human awareness, and our ties to nature itself. I’ve referred back to it in more than one blog, but I will reproduce it here again. The chemical scum to which he refers is humanity. It’s a phrase he borrows from Stephen Hawking. Here Deutsch is describing the energy (that was pressed out by magnetic fields around a galaxy collapsing into a black hole) that shot out in jets (producing a quasar). His observation is that this happened:
in precisely such a way that billions of years later, on the other side of the universe, some bit of chemical scum could accurately describe and model and predict and explain what was happening there, in reality. The one physical system, the brain, contains an accurate working model of the other, the quasar, not just a superficial image of it (though it contains that as well) but an explanatory model embodying the same mathematical relationships and the same causal structure… The faithfulness with which the one structure resembles the other is increasing with time. This chemical scum has universality. Its structure contains, with ever-increasing precision, the structure of everything…Physical objects that are as unlike each other as they could possibly be can, nevertheless, embody the same mathematical and causal structure and do it more and more so over time…This place is a hub which contains within itself the structural and causal essence of the whole of the rest of physical reality. The fact that the laws of physics allow this or even mandate that this can happen is one of the most important things about the physical world.
Deutsch’s unique choice of words are brought to mind for me often. But today they seemed particularly appropriate when I read a few reports of a study that was led by physicist and data analyst Dmitri Krioukov. The study found a structural similarity among networks that included the brain, the internet and the universe. A Live Science report describes, in broad outline, some of the ways that computer simulations were used to do the study. The report explains:
The results, published Nov.16 in the journal Nature’s Scientific Reports, suggest that some undiscovered, fundamental laws may govern the growth of systems large and small, from the electrical firing between brain cells and growth of social networks to the expansion of galaxies.
“Natural growth dynamics are the same for different real networks, like the Internet or the brain or social networks,” said study co-author Dmitri Krioukov, a physicist at the University of California San Diego.
“For a physicist it’s an immediate signal that there is some missing understanding of how nature works,” Krioukov said, “It’s more likely that some unknown law governs the way networks grow and change, from the smallest brain cells to the growth of mega-galaxies. This result suggests that maybe we should start looking for it”
I have come to see everything as the growth of structure, whether organic, inorganic, or conceptual (like language and mathematics) and I’m fairly sure that shared structure exists across the boundaries of these categories. Mathematics has the particular power of revealing sameness despite apparent differences. The study San Diego study supports this view of shared structure and uses mathematics to find it. As stated in UC San Diego’s press release:
“This is a perfect example of interdisciplinary research combining math, physics, and computer science in totally unexpected ways,” said SDSC (San Diego Supercomputer Center) Director Michael Norman.
“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,” added Marián Boguñá, a member of the research team from the Departament de Física Fonamental at the Universitat de Barcelona, Spain.