Astrophysics in the 20th Century
Edwin Hubble (1889-1953) is a central figure in the development of observational cosmology. From 1922 to 1936 Hubble solved four of the central problems in cosmology.
From 1922 to 1925 Hubble devised a classification system for galaxies by grouping them according to their content, distance, shape, size, and brightness. The galaxy classification system had become the Hubble morphological (The study of form, structure and the like. ) sequence of galaxy types. Previous to this, no satisfactory system existed, thus Hubble's powerful, yet simple scheme was an incredibly important scientific achievement.
By his discovery of Cepheids in 1924 and with parallel work in M33 and M31, Hubble proved decisively that these stars are outside of our galaxy. Thus bringing to a close the debate of whether there are other galaxies in the Universe beyond the Milky Way.
From 1926 to 1936 Hubble spent studying the distribution of galaxies and thus determining them to be homogeneous in distance. Hubble's 1934 paper was so detailed and convincing that it brought the problem of the mean galaxy distribution, which was by then more than 100 years old, to a close. Attempts were then made to measure the radius of curvature of space.
By 1936 Hubble, together with Milton Humason, showed beyond doubt the linear velocity-distance relationship (redshift-distance relationship). This led to the formulation of the Empirical Redshift Distance Law for galaxies, now days known as Hubble's Law.The law states that the greater the distance between any two galaxies, the greater their relative speed of separation ie Recessional Velocity = Hubble's Co...
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"Will this Universe ever end?." Internet WWW page at URL www.closertotruth.com/topics/universemeaning/213/213transcrips.html
Internet WWW page at URL http://oposite.stsci.edu/pubinfo/spacecraft/Primer/Hubble_Expand.htm
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Internet WWW page at URL www.spacetoday.org/History/MillenniumTimeline/20thCenturyLate.html
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