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## Adding Gas: An Early Experiment

#### Peebles Isocurvature Baryon (PIB) Cosmogony

Digital Cosmology Timeline

In this important simulation, based on a pure baryonic matter model
formulated
by renowned Princeton cosmologist James Peebles, and performed on a Convex
C-240, ordinary matter was modeled in a pure baryonic universe using **N
Body
**methods. A so-called N-body problem assumes that each particle in the
system exerts a force on all the other particles. If the system has N bodies,
then computing the force exerted on each body by all the others requires
N times N calculations for each time step.

These techniques can approximate the behavior of the baryonic gas on a
supercluster scale but, owing to computational limitations at that time,
could
not be used to study the details of emergent galaxy clusters. On the plus
side,
the calculations could be performed in all three spatial dimensions.

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#### Copyright, (c) 1995: Board of Trustees, University of
Illinois

*David Curtis. Last modified 10/9/95.*