PHYS 1201 Lecture Notes - Lecture 1: Cosmic Calendar, Orion Nebula, Milky Way
27 Jan 2017
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Chapter 1: a modern view of the universe. A large glowing ball of gas that generates heat and light through nuclear fusion. A moderately large object that orbits a star ; it shines by reflected light. A relatively small and rocky object that orbits a star. A relatively small and icy object that orbits a star. A star and all the material that orbits it, including the planets and moons. An interstellar cloud of gas and/or dust. A great island of stars in space, all held together by gravity and orbiting a common center. The sum total of all matter and energy ; that is, everything within and between all galaxies. Light travels at a finite speed (300,000 km/s) Thus, we see objects as they were in the past: The farther away we look in the distance, the further back we look in time. We see the orion nebula as it looked 1500 years ago.
