Expo/Science & Industry/Cosmos in a Computer

## What Does It Take to Put the Universe in a Box?

If you want to compute the cosmos you'll need a set of scientific theories that seek to explain how the universe formed and evolved

Next, you need to express those theories in mathematical models that best describe the behavior and interactions of the major physical components involved at different times and scales of cosmic evolution.

The mathematics must then be turned into a set of rules or algorithms that govern the way in which the computer handles the problem. This is a computer programming job of no small proportion!

The result is a cosmology code, a software program which, when run on a computer, numerically solves the mathematical equations expressed in a cosmological model. Once the "bugs" have been removed and the program runs smoothly and reliably, it is termed an application.

However, cosmologists must define the computational "box" in which to evolve their model universes through time. This box needs to be sufficiently big to include all the structures of interest, yet resolved finely enough to accurately model their internal structure and dynamics. So, for example, the box must resolve large scale structures, with distances spanning more than one billion light years, as well as individual galaxies less than 100,000 light years across--a range of four orders of magnitude.

In addition, the box must also resolve the mass of structures such as the large Magellanic cloud--about a billion solar masses (the solar mass, or the mass of the sun, is a standard unit of measurement in astronomy) all the way up to a large scale structure, containing many superclusters and voids, about 10^18 solar masses. That's a range of mass spanning nine orders of magnitude!

This multiscale approach allows cosmologists to run models that pose specific questions whose answers can be compared with observations of the real universe.

For example:

### What is their distribution at a given time?

The resulting codes, however, are very computationally-demanding; they demand powerful machines to do all the number crunching.

Michael Norman, NCSA/Univ. of Illinois, on-camera

QuickTime Movie (2.7 MB); Sound File (1.5 MB); Text

Analyzing a supercomputer's numerical output presents a formidable challenge. A typical cosmology simulation today generates billions of numbers. Making sense of all the numbers would be impossible without the aid of advanced visualization and technologies for navigating and interacting with all the data.

So, if you want to "put the universe in a box" you'll need access to really powerful computers, state-of-the-art cosmology codes, and innovative methods of data navigation.