The universe is built a lot like a giant brain – so is it conscious?

This story is part of our Cosmic Perspective series, in which we confront the staggering vastness of the cosmos and our place in it. Read the rest of the series here.

An astrophysicist and a surgeon walk into a bar. No, this isn’t the start of a bad joke. A few years ago, astrophysicist Franco Vazza met his childhood friend Alberto Feletti, who had become a neurosurgeon. As they reminisced and chatted about their work – Vazza modelling the structure of the universe, Feletti poring over the composition of the brain – a thought struck them: why not compare the two?

Vazza, based at the University of Bologna, Italy, did just that. He used statistical methods to compare the neurons in one area of the brain, the cortex, with the cosmic web, the pattern of matter distribution across the universe. Vazza looked at the number of nodes in each network and how densely each node was connected. The results surprised him. “It is a tantalising level of similarity,” he says. The structures differ in size by some 27 orders of magnitude. But if you ignore that, “the two patterns sort of overlap”, says Vazza.

For some physicists, this likeness is too tempting to ignore. Some have even suggested the possibility that the universe “thinks” or is in some sense conscious, an idea with roots in the philosophy of panpsychism.

Traditionally, researchers explained consciousness in one of two ways. Materialists say matter is all there is and consciousness – somehow – emerges from it. Dualists say there are…