History Weblecture for Unit 63
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Science textbooks often present theories as obvious and dominant, the "true" explanation. As we've seen, however, most scientific theories were formed slowly, and were often subject to resistance by other scientists, or by groups within the culture. The estimation of the size of the universe was no exception. In the 1920s, two astronomers used what is now realized as erroneous data to support opposing theories. Heber Curtis of the Lick Observatory claimed that many nebulae were much further away than individual star systems, and were themselves island systems of stars. Harlow Shapley used data that supported a smaller galaxy and required an interpretation of nebulous objects as gas clouds.
Read about the Curtis-Shapley debate at the NASA site. You can skip the bibliography sections.
Henrietta Leavitt was one of the women astronomers working on projects like Pickering's survey of stars. In her work, she started to notice a relationship between certain kinds of stars and their intrinsic brightness.
Read about Edwin Hubble at NASA's site on the Hubble Telescope.
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