Astronomy Edwin Hubble Essay Research Paper THE — страница 2

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themselves must be independent of the personality. Otherwise, the results have no objective reality. Yet the internal excitement in arriving at solutions is never this cold within the personality itself. Every scientist lives in a world of imagination. The grander the problem, the more wonderful must be the imagination. And Hubble lived with an ineffable problem – the discovery of the structure of the World on the largest scale. From this work, by him and by others of his generation, it is widely believed that some glimpse of a “creation event of the universe” became available to science by an objective method, not, as in other times, by metaphysics or speculation. Hubble must have understood more clearly than anyone what he was dealing with and what he had accomplished.

The realization that an understanding had finally been reached of the way the universe is organized, and above all, the discovery of its expansion, must have influenced in some way how Hubble lived with everyday events. His apparent aloofness, often mentioned by his critics, would, one suspects, not be so unusual in those who themselves could have been among the first to have had such a vision. But we, in fact, know little of Hubble’s inner world. He was remarkably silent about the meaning of what he and Humason had found with their velocity-distance relation. Neither in his personal conversations nor in his writings did he discuss its implications for ideas about either the evolution of the universe from a primitive state or its meaning concerning a “creation event”. What

little we can find of his thoughts about these matters – so common in the modern literature – must be inferred from his published papers. Four central accomplishments. From 1922 to 1936 Hubble solved four of the central problems in cosmology, any one of which would have guaranteed him a position of the first rank in history. (a). From 1922 to 1926 Hubble proposed a classification system for nebulae, both galactic (diffuse) and extragalactic. The galaxy classification system has become the Hubble morphological sequence of galaxy types. (b). With his discovery of Cepheids in NGC 6822 in 1924, with parallel work in M33 and M31, Hubble settled decisively the question of the nature of the galaxies, whose correct solution, to be sure, had previously been given using what many

believed to be inconclusive arguments, by Curtis, Lundmark, and ?pik. (c). From 1926 to 1936 the distribution of galaxies, averaged over many solid angles, was determined to be homogeneous in distance. The test was made by showing that the coefficient of the log N(m) count distribution with magnitude has a value of about 0.6 at bright magnitudes. This proved that galaxies truly mark a space which is significant to the universe itself. Galaxy counts to the magnitude limit of the Mount Wilson 100-inch telescope were then used to attempt a measurement of the radius of curvature of space by finding deviations of the coefficient from the Euclidean value of faint magnitudes. (d). The linear velocity-distance relation was set out in a discovery paper in 1929, followed by a series of

papers with Humason between 1931 and 1936 that verified and extended the relation to large (i.e. 60,000 km s[-1] redshifts. This discovery lead to the notion of the expanding universe which is the centre-piece (being the necessary condition) for the cosmological models of the present day. The published papers. (a) The Hubble classification sequence. No satisfactory classification system for galaxies existed before 1926, at which time two similar systems appeared in the literature, following discussions at the 1925 meeting of the International Astronomical Union in Cambridge, England. Before this time a purely descriptive system set up by Wolf (1908) had been used, but the classification showed no continuity between the Wolf types and was generally considered to be in need of

revision. Hubble (1920) in his Ph.D. publication had remarked that the Wolf classification “while admittedly formal, offers an excellent scheme for temporary filing until a significant system shall be constructed” (emphasis added here), and later in the same publication “[the Wolf system] is wholly empirical and probably without physical significance, yet offers the best available system of filing away data and will later be on great service when a significant order is established” (again emphasis added here). One cannot help but note that the construction of these two quotations shows that Hubble already possessed the confidence to accomplish what lay ahead when he would enter the field. This surety of language characterized much of his later writings – a surety which