Cosmological Issues

Cosmology is the study of the origin and the development of the Universe. As such, it is concerned with the large scale, both with respect to distance, and with respect to the past and future for the Universe.

The Big Questions

Cosmology asks the big questions: What is the overall structure of the Universe? What is its history and what will be its future? What are the mathematical principles that govern space and time? It is not concerned with details of how the Solar System works, or even the Milky Way Galaxy or the Local Group. The fundamental questions of cosmology as applied to today's Universe become relevant only on distance scales of superclusters and beyond, and on time scales of billions of years.

The Central Themes of Modern Cosmology

The central tenet of modern cosmology is the idea that the Universe is expanding, and that this implies that at some time in the distant past it was incredibly dense and hot. This "explosion" from a hot, dense initial state is called the big bang (or sometimes the hot big bang, to emphasize the high temperature during its occurrence). Some of the most important problems in cosmology are associated with understanding the big bang, understanding how structure formed in the Universe, and determining the nature of the mass contained in the Universe. (Recall that we can identify only 10 percent or less of the mass that we know, from its gravitational influence, must be there!).

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