Meet Mira, the supercomputer that makes universes

Bowen Goletz, Paul Rich and Ryan Milner working on Mira's stacks.

Bowen Goletz, Paul Rich and Ryan Milner working on Mira's stacks. Argonne National Laboratory

Next month, one of the world's fastest supercomputers will run the largest, most complex universe simulation ever attempted.

Cosmology is the most ambitious of sciences. Its goal, plainly stated, is to describe the origin, evolution, and structure of the entire universe, a universe that is as enormous as it is ancient. Surprisingly, figuring out what the universe used to look like is the easy part of cosmology. If you point a sensitive telescope at a dark corner of the sky, and run a long exposure, you can catch photons from the young universe, photons that first sprang out into intergalactic space more than ten billion years ago. Collect enough of these ancient glimmers and you get a snapshot of the primordial cosmos, a rough picture of the first galaxies that formed after the Big Bang. Thanks to sky-mapping projects like the Sloan Digital Sky Survey, we also know quite a bit about the structure of the current universe. We know that it has expanded into a vast web of galaxies, strung together in clumps and filaments, with gigantic voids in between. 

The real challenge for cosmology is figuring out exactly what happened to those first nascent galaxies. Our telescopes don't let us watch them in time-lapse; we can't fast forward our images of the young universe. Instead, cosmologists must craft mathematical narratives that explain why some of those galaxies flew apart from one another, while others merged and fell into the enormous clusters and filaments that we see around us today. Even when cosmologists manage to cobble together a plausible such story, they find it difficult to check their work. If you can't see a galaxy at every stage of its evolution, how do you make sure your story about it matches up with reality? How do you follow a galaxy through nearly all of time? Thanks to the astonishing computational power of supercomputers, a solution to this problem is beginning to emerge: You build a new universe.

In October, the world's third fastest supercomputer, Mira, is scheduled to run the largest, most complex universe simulation ever attempted. The simulation will cram more than 12 billion years worth of cosmic evolution into just two weeks, tracking trillions of particles as they slowly coalesce into the web-like structure that defines our universe on a large scale. Cosmic simulations have been around for decades, but the technology needed to run a trillion-particle simulation only recently became available. Thanks to Moore's Law, that technology is getting better every year. If Moore's Law holds, the supercomputers of the late 2010s will be a thousand times more powerful than Mira and her peers. That means computational cosmologists will be able to run more simulations at faster speeds and higher resolutions. The virtual universes they create will become the testing ground for our most sophisticated ideas about the cosmos. 

Read more at The Atlantic.