These are the definitions of the meter and second in the SI system. The source is the site of the International Bureau of Weights and Measurements at
http://www1.bipm.org/en/si/base_units/
"The metre is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second."
"The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."
