Computing and the Cosmos

The BBC is carrying a nice little story about the "Millenium Run", a supercomputer simulation of cosmological structure formation, in which the dynamics of 10 billion dark matter particles were tracked over 13 billion years of cosmological evolution. Numerical simulations are a crucial part of modern cosmology, allowing us (where by "us" I mean people like me, but who know how to write huge, complicated N-body codes) to understand how well-defined interaction rules between dark matter particles, acting in an expanding cosmos, lead to the wonderfully rich, complex, and structured universe we see today.

Without the use of computers there are many ways to understand, in broad terms, how structure formation takes place. However, in order to make detailed comparisons between theory and observations, hard-core computational cosmology is a must. You might wonder why the simulation just tracks dark matter, but it turns out that dark matter is the crucial part of why clusters of galaxies form in the patterns they do. There is a lot more dark matter than regular matter (the stuff that glows). This dark matter gathers together under the effects of gravity, creating large conglomerations, the attraction towards which causes the regular matter to clump up into the clusters of galaxies we see today. It's a beautiful story, and one that is borne out wonderfully by the comparisons between the Millenium Run simulations and the data from the Sloan Digital Sky Survey.

Carlos Frenk, who is one of the world's leaders in this area, is quoted in the BBC story, saying

"We have learned more about the Universe in the last 10 or 20 years than in the whole of human civilisation"

This is a big bold claim, but I think it is entirely fair. The tremendous progress in cosmology in the last couple of decades has given us a coherent picture of the universe; more detailed than many cosmologists had thought would ever be possible. This data is going to continue to flood in over the next few decades, further focusing attention on the fascinating question of how the observed cosmos connects to our theories of fundamental physics. It's a daunting task, but oh so much fun to be faced with.