Earth Sciences 1086F/G Lecture Notes - Lecture 2: Triangulum Galaxy, Parsec, Local Group
3 Apr 2015
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Document Summary
That is, it was created at some time in the distant past and will forever exist as seen now. With the exception of an occasional shooting star", nothing much seems to be happening. But actually, having just learned that all time and space were produced together in a big bang, we know better: it is all a matter of scale. So in this chapter we will see how we define that scale! The distances between stars and galaxies in the universe are so vast it would be unwieldy to describe them in miles or kilometres (it would be like measuring the distance from toronto to tokyo in inches or centimetres! Instead, scientists use light-years to measure distances in space. A light-year is the distance that light travels in one year. Light travels at about 300,000 km per second; there are 31,500,000 seconds in a year. Multiply that and you will see that light travels 9. 4608 1012 km per year.
