Gastrophysical Cosmology

Abstract

Over the past decade, cosmology has largely focussed on gravitational forces, or, if gas was included, by linear perturbation calculations or by highly simplified and symmetric nonlinear models, with some notable pioneering exceptions. We hope that a Universe dominated by elementary particle relics will be largely understandable in such simple terms, and, with the COBE observation of CMB anisotropy, there is hope that our wishes will be realized. We would then know the redshifts when dark matter condensations of various masses formed. However to understand the formation and evolution of galaxies, quasars, Lyα clouds, the IGM, clusters, and all of the other directly observable beasts that inhabit the cosmic zoo we must include in full gory detail the effects of the gas as it shock heats, photoionizes, radiatively cools, suffers fragmentation, forms stars, is transported outward in galactic winds, and inward in galactic and larger mass mergers; and then there are magnetic fields. Once complex gas processes are included, calculations become frustratingly difficult to make definitive, but there is reason for theoretical optimism, especially with the rapidly growing data-bases to guide us. Conferences like Tetons ‘82 that bring together primarily ISM types and primarily cosmological types to assess where we stand in the development of a fully dissipative gas-dynamical theory of cosmic structure formation are essential for progress. In this overview, I will try to address the scales over which we think gastrophysical processes will be most relevant and the impact they may play in our overall cosmological understanding.