By now we have completed the preliminary part of the course. Now, in contemplating about the proper methodology to be used during the rest of these lectures, we note that the very nature of preliminary lectures on cosmology is, to some extent, analogous to a piecemeal scanning of terrestrial countryside from a watchtower on a dark night, using our own searchlight. In view of the limited sweep of the latter, all it can show, at a given instant, is an elongated ellipse of land, trees and rocks. It is only by the combined use of piecemeal observations, and memory, that the watcher can construct a preliminary picture of his surroundings. But this time the watcher is invited to take a second look,with “starlight” as the only source of “illumination”.
KeywordsBulk Viscosity Radiation Density Newtonian Theory Radiation Energy Density Time Asymmetry
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