Physical Universe

Imagine that two people have been chosen to be observers in a scien­ tific experiment involving two photons, or quanta of light. These pho­ tons originate from a single source and travel in opposite directions an equal distance halfway across the known universe to points where each will be measured or observed. Now suppose that before the pho­ tons are released, one observer is magically transported to a point of observation halfway across the known universe and the second ob­ server is magically transported to another point an equal distance in the opposite direction.

Our purpose in writing this book is to show how physics has been applied to developing our current understanding of the phase structure, physical condi­ tions, chemical makeup and, evolution of the (thermal) interstellar medium. We hope it provides an up-to-date overview which postgraduates, advanced undergraduates, and professionals in astrophysics can use as a "reference of first resort" before going on to read the more specialist monographs or research literature.

Modern cosmology is a quickly developing ?eld of research. New technical devices and tools supply the community with new experimental data measured with high accuracy. The self-consistent explanation of these data needs t- oretical models that are based on hypothetical predictions of particle theory. In their turn, such predictions imply cosmology for their probe. Speci?c st- ies of the cosmological consequences of particle theory, linking them to their observable signatures, are actual. This boiling kettle of theoretical research and experimental efforts produces ideas that will be preserved for following generations.