The cosmological constant is an extra term in Einstein's equations of general relativity which physically represents the possibility that there is a density and pressure associated with "empty" space. The inclusion of this vacuum energy term can greatly effect cosmological theories.
The following pages present a discussion of the role the cosmological constant plays in modern cosmology. They are designed to offer an overview of how the cosmological constant alters standard cosmology, and to discuss whether a non-zero cosmological constant exists today. Some background will be provided in these pages, but the reader is expected to have a familiarity of the basic concepts of physics and cosmology. The casual reader, however, should not be dissuaded from venturing on, as many of the qualitative concepts can be easily understood, even if the mathematics are not.
In the Socratic vein, these pages are organized into several fundamental questions regarding the cosmological constant. They are arranged as to provide the reader with a cohesive presentation if they are read in order, but also to provide reference.
How does the cosmological constant fit into general relativity?
How does the cosmological constant affect the evolution of the Universe?
What are the observational constraints on the cosmological constant?
How physically plausible is the cosmological constant?
Was the inclusion of the cosmological constant Einstein's "biggest blunder"?
Where can I find more information about cosmology and the cosmological constant?
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