How do you use astronomical units and light years as measures of distance between the sun, stars and earth?

1 Answer
Trevor Ryan.
Dec 25, 2015

By definition, a light year is the distance that light travels in 1 year.

Since the speed of light in air or vacuum is #3xx10^8m//s#, it implies that a light year, ie the distance covered by a photon of light in a time period of 1 year, is

#x=ct#

#=(3xx10^8//s)*(365daysxx24hrsxx60minsxx60s)#

#=9.4608xx10^15m#.

The order of magnitude of such a distance is hard to comprehend on earth, but considering the size of the entire universe of several galaxies, of which earth's milky way is one of the smaller ones, along with the distances between celestial bodies of the various galaxies, we can see that such orders of magnitudes are an appropriate measure for such large distances and spaces.

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