The Well Balanced Universe
Millions of hours of expensive supercomputer time used to prop up big bang model
12 February 2010
The big bang theory of the universe needs to invoke the existence of a
hypothetical substance called cold dark matter. This is necessary in
order for it to explain how galaxies were able to form out of rapidly
expanding, smooth space after the initial explosion out of nothingness.
With so much mass suddenly removed from the centre of the galaxy, the pull of gravity on the dark matter there is diminished and the dark matter drifts away, Governato said. It is similar to what would happen if our sun suddenly disappeared and the loss of its gravitational pull allowed the Earth to drift off into space.
By making these cosmic explosions big enough and frequent enough it was possible for the simulations to generate galaxies with substantially lower densities at their cores, closely matching the observed properties of dwarf galaxies.
"The cold dark matter theory works amazingly well at telling where, when and how many galaxies should form," Governato said. "What we did was find a better description of processes that we know happen in the real universe, resulting in more accurate simulations."
The theory of cold dark matter, first advanced in the mid 1980s, holds that the vast majority of the matter in the universe — as much as 75% — is made up of "dark" material that does not interact with electrons and protons and so cannot be observed. The term "cold" means that immediately following the big bang these dark matter particles have speeds far lower than the speed of light.
In the cold dark matter theory, smaller structures form first, then they merge with each other to form more massive halos, and finally galaxies form within the halos.
See a movie depicting galaxy formation based on supercomputer simulations using a refined understanding of the cold dark matter theory: www.astro.washington.edu/users/fabio/movies/dwarfCDM2.mov
Coauthors of the Nature paper are Chris Brook of the Jeremiah Horrocks
Institute in the United Kingdom; Lucio Mayer of the Institut für
Astronomie and the Institute for Theoretical Physics in Switzerland;
Alyson Brooks of the California Institute of Technology; George Rhee of
the University of Nevada; James Wadsley and Gregory Stinson of McMaster
University in Canada; Patrik Jonsson and Piero Madau of the University
of California, Santa Cruz; Beth Willman of Haverford College in
Pennsylvania and Thomas R. Quinn of the UW.