Welcome novices!

Cosmology is the science of the universe. It deals with questions of extreme proportions in a scientific manner. At this site, you can see results from cutting edge computer experiments designed to explore the detailed formation of the large-scale space-time fabric in which we live.

No single computation can cover the entire range of scales over which structure exists in our real ("meat-space") universe, but we can create a "virtual universe" which replicates the properties of the real one over a finite range of space and time. The Hubble Volume simulations attempt to capture the formation of the largest cosmic structures we can ever hope to see. They are novel in at least two respects:

• The experiments probe the largest region of space ever simulated. The diagonal of the cubic region used in the calculation spans a distance equivalent to the distance from us to the most distant known quasars and galaxies. In fact, the simulations come very close to modeling the entire visible universe.

• The experiments are the largest computations of their kind. Five hundred and twelve linked processors in an SGI/CRAY T3E parallel supercomputer evolved one billion mass elements (virtual "particles" used to represent the mass density in the universe) and produced nearly half a terabyte (500 Gb) of output data.

Images available at this site show structure in the dominant dark matter component of the universe. The images show that gravity arranges matter in the universe into a filamentary, or web-like, structure. In a process known as hierarchical clustering, the spatial scale of the web evolves in time, starting out very fine and becoming more expansive as the universe ages.

An important product of this work is creation of synthetic galaxy catalogues for comparison to upcoming, large observational surveys such as the Sloan Digital Sky Survey and the 2dF Survey. Although the experiments shown here don't directly model galaxy formation, artificial galaxy catalogues can still be generated in a model dependent way by assuming a particular statistical relationship between dark matter and galaxies. The issue of "how light traces mass" in the universe is a complex question currently being investigated with other types of numerical simulations.

Further information on the simulations can be found in this press release from the June 1998 meeting of the American Astronomical Society. Technical details are located in the expert section. Items italicized above are explained in a short glossary of terms.

For more background material, refer to the reference for a list of selected books on cosmology. Cosmos in a Computer is an extensive site providing background material on cosmology in general and numerical simulations in particular. For a site with a broader coverage of astronomy and astrophysics, check out Windows on the Universe.