One
light-year (ly) is defined as the distance that light can
travel in 1 year. This distance is fixed because light always
travels at the same speed—the speed
of light, which is 300,000 km/s
(186,000 mi/s).
We can
calculate the distance represented by a lightyear by recalling that
Distance =
speed x time
For example,
if you travel at a speed of 50 km/hr for 2 hours,
you will travel 100 km. To find the distance represented by 1
light-year, we simply multiply the speed of light
by 1 year:
1 light-year =
(speed of light) x (1 yr)
That is,
1 light-year is equivalent to 9.46 trillion km, which is easier
to remember as almost 10 trillion km.
BOOK: The Essential Cosmic Perspective with MasteringAstronomy (Sixth Edition)
Download PowerPoint: http://es.scribd.com/doc/98066015/CH1-Our-Place-in-the-Universe
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