Bolshoi Simulations of the Universe
This is a visualization of the Bolshoi Simulation, an attempt to chart the evolution of the large-scale structures in the universe using the data from the cosmic background radiation. (“Bolshoi” means “great” or “grand” in Russian.)
The Bolshoi supercomputers create this simulation of the large-scale structure of the universe by first examining the data from NASA’s WMAP explorer, which maps out the cosmic microwave background radiation. Since this radiation is the light left over from the Big Bang, it’s the most ancient data in the universe, and from those starting conditions the supercomputer can use existing theoretical knowledge to simulate the evolution of different parts of the universe. Because the supercomputer’s results match up almost perfectly with what we actually can observe of the history of the cosmos, astronomers are confident in its accuracy as a proxy for the actual universe.
Dark matter is a key part of the simulation – it would have to be, considering it accounts for 25% of everything in the universe and about 80% of all matter. The simulation relies on a theoretical model known as the Lambda Cold Dark Matter model, which says that gravity began pulling bits of dark matter together into clumps shortly after the Big Bang. These clumps became larger and larger over time, attracting regular matter to form galaxies around them. Even though we still don’t know exactly what dark matter is, it is the primary driver of the evolution of the cosmic structure.
Here’s another video from the Bolshoi site, this one depicting the close match between the results of the simulation and the actual observed universe:
We see galaxies in the sky, but cannot see the dark matter clumps surrounding them. However, we can simulate them as they form in a model Universe. In this video we show how good the agreement is between the observed distribution of galaxies in the SDSS sky survey, and the predicted distribution of model galaxies associated with dark matter halos in the Bolshoi simulation.
Finally, if you’ve got an extra half-hour to spare and you really want to dive in deeper with all this, check out this lecture by Joel Primack at the 2011 Santa Cruz Galaxy Workshop, in which he explains how the entire simulation works.