Edwin Hubble

Edwin Powell Hubble (November 20, 1889 – September 28, 1953) was an American astronomer, noted for his discovery of galaxies beyond the Milky Way and the cosmic red shift. Edwin Hubble was one of the first to argue that the red shift of distant galaxies is due to the Doppler effect induced by the expansion of the universe. He was one of the leading astronomers of modern times and laid down the foundation upon which physical cosmology now rests.

Discoveries

Galaxies exist beyond the Milky Way

Hubble's arrival at Mount Wilson in 1919 coincided roughly with the completion of the 100-inch Hooker Telescope, then the world's most powerful telescope. Hubble's observations in 1923–1924 with the Hooker Telescope established beyond doubt that the fuzzy "nebulae" seen earlier with less powerful telescopes were not part of our galaxy, as had been thought, but were galaxies themselves, outside the Milky Way. He announced this discovery on December 30, 1924.

Related Topics:
1919 - Hooker Telescope - 1923 - 1924 - Nebulae - Galaxy - Milky Way - December 30

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Hubble also devised a classification system for galaxies, grouping them according to their content, distance, shape, size and brightness.

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The universe is expanding

Hubble was generally credited with discovering{{fn|2}} the redshift of galaxies. In 1929 Hubble and Milton Humason formulated the empirical Redshift Distance Law of galaxies, nowadays known as Hubble's law, which, once the redshift is interpreted as a measure of recession speed, is consistent with the solutions of Einstein?s General Relativity Equations for an homogeneous, isotropic expanding space. This led to the concept of the expanding universe. The law states that the greater the distance between any two galaxies, the greater their relative speed of separation.

Related Topics:
Redshift - 1929 - Milton Humason - Redshift Distance Law - Einstein - General Relativity Equations - Expanding universe

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This discovery later resulted in the formulation of the Big Bang theory.

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Earlier, in 1917, Albert Einstein had found that his newly developed General Theory of Relatively indicated that the universe must be either expanding or contracting. Unable to believe what his own equations were telling him, Einstein introduced a cosmological constant (a "fudge factor") to the equations to avoid this "problem". When Einstein heard of Hubble's discovery, he said that changing his equations was "the biggest blunder of my life".{{fn|3}}

Related Topics:
1917 - Cosmological constant

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Other discoveries

Hubble discovered the asteroid 1373 Cincinnati on August 30, 1935. He also wrote The Observational Approach to Cosmology and The Realm of the Nebulae around this time.

Related Topics:
Asteroid - 1373 Cincinnati - August 30 - 1935

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