Illustris: The Virtual Universe
May 8, 2014

Illustris: The Virtual Universe

Recently I found myself playing a sandbox-style video game and found myself completely blown away by the sheer amount of detail the creators put into the city my digital avatar was traversing. The amount of attention that was put into every building, every street, and many of the inhabitants (I say “many” because a lot of them were copies of each other) was truly amazing. Even more so was the actual scope of the city. It was huge. Going at speeds that would likely liquefy any real human being should they ever attempt them in reality, it still took me several minutes to travel from one end of the city to another. Online games, especially those like World of Warcraft and Guild Wars, have even larger worlds that your avatars inhabit, and the amount of detail put into these is simply staggering. So, with that said, I was left wondering just how big someone could go with an all-digital world. How big could we design something while still maintaining that same level of attention to small details?

Oh, about something the size as the Universe, perhaps?

The culmination of five years of programming, the Illustris computer simulation developed by a team of researchers from various institutions including the Harvard-Smithsonian Center for Astrophysics and the Heidelberg Institute for Theoretical Studies in Germany. The Illustris simulation is able to recreate 13 billion years of cosmic evolution in a cube that is 350 million digital light-years across. More so, it is able to do this with an unprecedented level of resolution, including both normal and dark matter, which uses 12 billion 3D pixels. This simulation required three months of “run time” to calculate, using a total of 8,000 CPUs all running in parallel. In comparison, if the team had been forced to use a computer like the one I am sitting at to do this, it would have taken it more than 2,000 years to complete.

Illustris’s simulation begins only 12 million years after the Big Bang first gave shape to our universe. As it reached present day, researchers were able to count more than 41,000 different galaxies within the simulated space. It also revealed a very realistic mix of different galaxy types, such as spiral galaxies like our own Milky Way as well as football-shaped elliptical galaxies. It was also able to recreate large-scale structures like galaxy clusters as well as the many galactic bubbles and voids that make up the cosmic web. On the smaller scale, it was also able to accurately recreate the varied chemistries of individual galaxies. Sure, it cannot zoom in to individual organisms on individual plants within individual galaxies, but this level of detail in the simulation remains a truly incredible feat.

“Until now, no single simulation was able to reproduce the universe on both large and small scales simultaneously,” said the lead author on the study Mark Vogelsberger of MIT/the Harvard-Smithsonian Center for Astrophysics. Most previous attempts to do such a thing have suffered due to lack of computing power and the many complexities of the underlying physics of the universe. This forced many such programs to either have much more limited resolution or forced their focus on individual portions of the universe at a time. Earlier simulations than even this had trouble modeling the complex feedback from things like star formations, supernova explosions, and super-massive black holes. All of these issues are ones that Illustris has managed to overcome.

Image Credit: Illustris Collaboration

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