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Physical Environment > Light Year |
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This site tells the story of the history of the universe. Click Earlier and Later to follow the story. Note: Many facts have been simplified to make them easier to understand. |
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A light year is a measurement of distance, not of time.
It is the distance light travels in one year. Light is used to measure distance since it is the fastest thing in the Universe. Light travels at about 300 million meters per second. It takes light about 5½ hours to travel across the solar system, so a light year is much bigger than this. The nearest star to us (apart from the Sun) is Proxima Centauri, which is about 4¼ light years away. The Milky Way Galaxy is a disc about 100,000 light years across and around 2000 light years thick. A light-year equals about 9.46053 x 1012 km (or 5.878 x 1012 miles). |
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Physical Environment > Light Year |
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Basic Information |
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