Lecture Notes for Jan 22, 2009

January 22, 2009 Speed of light = 3.00x10^8 m/sec a. The earth's circumference = 1/7 seconds moving at the speed of light b. earth to moon = 1.25 seconds when moving at the speed of light c. earth to sun = 8.3 minutes when moving at the speed of light d. the diameter of pluto's orbit = 11 hours when moving at the speed of light e. sun to Proxima Centauri = approx. 4.2 years when traveling at the speed of light f. earth's sun to the end of the milky way = 100,000 years when traveling at the speed of light g. milky way galaxy to the andromeda galaxy = 2.2 million years when traveling at the speed of light h. radius of the observable universe = 14 billion years when traveling at the speed of light -Space and time are defined by the expansion of the universe Astronomical Distances -uses metric units (see appendix A in book) Distance with in the solar system: Astronomical Unit (AU): avg. earth-sun distance 1 AU is approx. 150 million km which is approx. 500 times distance to the moon Distance Between Stars light year = distance that light travels in one year