In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Λ) is equivalent to an energy density in otherwise empty space. It was originally proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. Einstein abandoned the concept after the observation of the Hubble redshift indicated that the universe might not be stationary, as he had based his theory on the idea that the universe is unchanging. However, a number of observations including the discovery of cosmic acceleration in 1998 have revived the cosmological constant, and the current standard model of cosmology includes this term.
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Famous quotes containing the word constant:
“Genius detects through the fly, through the caterpillar, through the grub, through the egg, the constant individual; through countless individuals the fixed species; through many species the genus; through all genera the steadfast type; through all the kingdoms of organized life the eternal unity. Nature is a mutable cloud which is always and never the same.”
—Ralph Waldo Emerson (1803–1882)