Meter Defined by Speed of Light
The meter is defined to be the distance that light travels in 1/299,792,458 of a second in a vacuum. Distance traveled is speed multiplied by time.
Source
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"OpenStax College, College Physics. October 10, 2012."
http://cnx.org/content/m42091/latest/?collection=col11406/1.7
OpenStax CNX
CC BY 3.0.