Now researchers are planning the most detailed, largest-scale simulation of this kind to date. One of the main mysteries they hope to solve with it is the origin of the dark energy that's causing the universe to accelerate in its expansion.

The new simulation is a project led by physicists Salman Habib and Katrin Heitmann of Illinois' Argonne National Laboratory, and will run on the lab's Mira supercomputer, the third-fastest computer in the world, starting in the next month or two. The program will use hundreds of millions of "particles" — elements in the simulation that stand in for small bits of matter. The computer will let time run, and watch as the particles move through space in response to the forces acting on them.