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Adding Gas Dynamics

Cosmology models that rely principally on "cold" dark matter tend to generate large-scale structures too soon. The recipe for the cosmos improves when "hot" dark matter is added: the simulated structures begin to emerge more slowly, though now a bit on late side. Observations show that galaxies may have started forming as soon as 1 billion years after the Big Bang, when the universe was less than one-fifth its present size.

For a simulation to have predictive value, it needs to be compared against the real universe. To accomplish that requires including some ordinary "baryonic" matter to the mix, for this is the stuff of which the visible universe is made.

Jeremiah Ostriker, Princeton University, on-camera
Movie/Sound Byte
QuickTime Movie (3.6 MB); Sound File (1.7 MB); Text

In practice, modeling baryonic matter requires calculating the physical behavior of the primordial gas, principally hydrogen and helium, as it is drawn into gigantic gas clouds by the gravity exerted by the dark matter. Such clouds provide the material from which galaxies, galaxy clusters and superclusters condense.

As the gas is made of atoms or their nuclei, modeling its physical behavior must draw on well-established physics. For bulk gas, the laws of hydrodynamics determines how fluids, including gases, behave when expanded or compressed, heated or cooled. This behavior includes the formation of shock waves when gas is accelerated into the gravitational wells created by the dark matter.

Jeremiah Ostriker, Princeton University, on-camera
Movie/Sound Byte
QuickTime Movie (2.8 MB); Sound File (1.2 MB); Text

An Early Experiment
Testing Hydrodynamics in 2-D
Stepping up to 3-D
Computing the X-Ray Universe

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NCSA. Last modified 10/7/95.