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Saturday, November 28, 2015

How far is a light-year? | Astronomy Essentials | EarthSky

How far is a light-year? | Astronomy Essentials | EarthSky



Here's an interesting way to mentally visualize a light year:



One astronomical unit (distance of the earth from the sun) equals about 150 million kilometers (93 million miles). Another way of looking at it: the astronomical unit is a bit more than 8 light-minutes in distance.
Quite by coincidence, the number of astronomical units in one light-year and the number of inches in one mile are virtually the same. For general reference, there are 63,000 astronomical units in one light-year, and 63,000 inches in one mile. This wonderful coincidence enables us to bring the light-year down to Earth. If we scale the astronomical unit – the Earth-sun distance – at one inch, then the light-year on this scale represents one mile.

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