ASTRON 2B03 Lecture Notes - Vacuum Energy, Project Sign, Before Present
25 Sep 2013
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Cosmology study of the origin and evolution of the universe. 1) distances to other galaxies -> standard candles (observed brightness vs. true brightness) 2) doppler shift shifting red or blue. In our telescopes, we install a prism (or a grading) which measures the spectrum of light. After it passes through a prism, you can see how much light is in each of the spectrum colours. In astronomy, we have 2 ways to collect data: imaging. Simplest: spectroscopy - measuring the spectrum of light. Farther away a galaxy is, the faster it is moving away. Its not that galaxies are moving away relative to us, its that everything is moving away from everything. 1) as time goes on, galaxies should be more and more farther apart. If we moved time backwards, galaxies should be moving closer: we can look back in time, lookback time! Density of galaxies goes up in the past -> exactly what hubble predicted w/ expanding universe.
