ASTRON 1101 Lecture Notes - Lecture 2: Astronomical Unit, Sun-2, Interplanetary Spaceflight
31 Aug 2016
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Document Summary
Our place in space: the solar system is big. It"s 150 million km, or 1 astronomical unit, from earth to sun: the milky way galaxy is really big. The center of the milky way galaxy is 27,000 light-years away: distances between galaxies are really, really big. Determining the distance to astronomical objects is difficult. The circumference of the earth is 40,000km (24,900 mi) The kilometer was initially defined so that the distance from the equator to the north pole is 10,000 km. 380,000 km = 9. 6 times the earth"s circumference. Average distance from earth to sun is 150 million km = 1 au. As its next close approach to earth (july 2018), mars will be 58 million km (0. 39 au) away. Round trip travel time/2 = one-way travel time. One-way travel time * c (speed of light) = distance. Light travels through a vacuum at a constant speed, called c . c = 300,000 km/s (186,000 mi/s)
