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Unformatted text preview: • Modern views of solar system • Solar system at center of galaxy • Diameter of 55,ooo llightyears o Shapley's Galaxy • Diameter 300,000 lightyrs (2x too large) • Earth no longer at center • Spiral nebulae are within our galaxy o Hubble's universe • Spiral nebulae are distinct galaxies 6. Distances to galaxies o Identify cepheid o Measure brightness and period o Read off luminosity using period o Combine brightness and luminosity to get distance 7. Galaxies are moving away from us o First noted in 1914 o 11/15 spiral nebulae were red shifted o Curtis used this as evidence that they were outside the galaxy o Fully established by Hubble and Humason in 1929 • Measured red shifts and Cepheid distances for many galaxies 8. The Hubble Law o Further galaxies move faster o Hubbles original data very poor • Only nearby galaxies • Distances were inaccurate o Confirmed by modern data v=H d o Big question: What is the constant H ??...
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