Earth's orbital diameter is: ~30 x 10^7 km
number of seconds in a year is: ~ π x 10^7 s
so, Earth's orbital velocity is: ~30 km/s
speed of light, c, is: ~30 x 10^4 km/s
so, Earth's orbital diameter is: ~ 1,000 light seconds
and, Earth's orbital velocity is: ~ 0.0001 c
