PCS 181 Lecture 2: PCS 181 Unit 2
19 Feb 2017
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Lightyear=ly: distance that light travels in 1 year. Astronomical unit=au: avg distance between earth and sun. Grand design galaxy: you can see all of its features. A galaxy is a large assemblage of stars which orbit a common center. Contains from a few thousand to trillions of stars. All faraway galaxies are redshifted and receding from us. Hubble law: radial velocity of a galaxy is directly proportional to distance. Nebula (nebulae): clouds of unformed h2 and he gas. T=2. 728 +/- 0. 004 k 3k=cmb=temperature of empty interstellar space. Penzias and wilson discovered remnant heat from birth of universe. There was a heat event at beginning of space and time as proven by cmb. Thus, universe originated in an explosive event called the big bang. Homogeneous: matter is approx. evenly and uniformly distributed. Every region is same as every other region. Universal: laws of physics are same everywhere. Matter an anti-matter begin annihilation to produce energetic photons.
