INTEGBI C13 Lecture Notes - Lecture 14: Electromagnetic Spectrum, 30 Foot Fall, Copernican Principle
20 Oct 2016
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Document Summary
Cosmology is the study of the origins and fate of the universe. Light has taken around 1 billion years to reach us. We are seeing into the past: the galaxies as they were 1 billion years ago. Object moves away from us we observe a longer wavelength (redshifted) Object moves towards us we observe a smaller wavelength (blueshifted) The doppler effect: how we measure the speed of astronomical objects. Measuring distances to distant objects is difficult, analogous to how we date fossils. H0 is about 21 km/s per million light years. Expansion viewed from two different galaxies is the same. Not fully correct to say that galaxies are moving through space with speeds that satisfy. The wavelength of light accumulates its redshift on its way to us as the universe expands. Light was emitted when the universe was about 7. 3 times smaller (7. 3 times closer together)
