What's the longest your computer has ever been running? A day? A week? A month? If you'd like to join the elite club of Universe simulators, that's just not going to cut it - not by a long shot. In fact, if you booted up the brand-new Illustris simulation on your laptop, you'd have to leave it running for more than 2,000 years to simulate the history of just a small part of the cosmos. That's a pretty dang long time.
Fortunately for the team developing Illustris, linking computer processors together can speed that time frame up. It's still an intimidating task, though: 8,000 connected computers still took more than 3 months to simulate just one ten-billionth of the observable Universe over the course of 14 billion years!
Why undertake simulations like this? In a way, it's simply a return to the roots of physics. The ultimate predictive science, physics rests on the fundamental idea that if we know the state of something at one time, we can exactly predict the state it will be in later on. Of course, for anything beyond the most elementary of situations, this is easier said than done.
Does this mean that Illustris should have formed our own galaxy, the Milky Way? Unfortunately, it doesn't really work that way. In order to achieve the world we see today, the simulation would need to be set up with the exact conditions of our early universe and simulate things with infinite precision. Since we can never have truly infinite time or precision, scientists have to craft a simulation that yields a good approximation to reality. To evaluate the success of the simulation, we look not for exact results, but matching physical parameters. For example, Illustris produces the right mix of spiral and elliptical galaxies and fills those objects with the right mix of chemicals.
So, how will astronomers use this simulation? By matching observations from telescopes like Hubble to similar structures in the simulation, researchers will be able to glimpse possible formation mechanisms. Combined with observations of similar objects at different stages of their lives, this will enable a more comprehensive history of galaxies to be developed.
Be sure to check out the above video - it is astonishing!