Definition:Speed of Light/Historical Note

Historical Note on Speed of Light
Until the $1983$ definition of the metre as exactly $\dfrac 1 {299 \, 792 \, 458}$ of the distance travelled by light in $1$ second, the speed of light has been the subject of measurement.

This measurement has been accomplished to greater and greater accuracy over the course of history.


 * $1675$
 * and
 * observing the moons of Jupiter
 * $220 \, 000$
 * $-27 \%$
 * $-27 \%$


 * $1729$
 * aberration of light
 * $301 \, 000$
 * $+0 \cdotp 40 \%$
 * $+0 \cdotp 40 \%$
 * $+0 \cdotp 40 \%$


 * $1849$
 * toothed wheel
 * $315 \, 000$
 * $+5 \cdotp 1 \%$
 * $+5 \cdotp 1 \%$
 * $+5 \cdotp 1 \%$


 * $1862$
 * rotating mirror
 * $298 \, 000$
 * $\pm 500$
 * $−0 \cdotp 60 \%$
 * $−0 \cdotp 60 \%$


 * $1907$
 * Rosa and Dorsey
 * EM constants
 * $299 \, 710$
 * $\pm 30$
 * $−280$ ppm


 * $1926$
 * rotating mirror
 * $299 \, 796$
 * $\pm 4$
 * $+12$ ppm
 * $+12$ ppm


 * $1950$
 * Essen and Gordon-Smith
 * cavity resonator
 * $299 \, 792 \cdotp 5$
 * $\pm 3 \cdotp 0$
 * $+0 \cdotp 14$ ppm


 * $1958$
 * K.D. Froome
 * radio interferometry
 * $299 \, 792 \cdotp 50$
 * $\pm 0 \cdotp 10$
 * $+0 \cdotp 14$ ppm


 * $1972$
 * Evenson et al.
 * laser interferometry
 * $299 \, 792 \cdotp 4562$
 * $\pm 0 \cdotp 0011$
 * $−0 \cdotp 006$ ppm