---snip---The earth is moving very fast, it spins, tilts, and wobles, orbits the sun, our solar system moves withen our arm of the galaxy, it is also moving up and down in the galaxy, our arm of the galaxy is orbiting the center of the galaxy, our galaxy is probably moving relitive to the other galaxies in the local group and the local group is moving away from other galaxies, and more I'm sure---snip---
Thanks a bunch, now I'm permanantly dizzy.
The short (math-free) answer is that the frequency of the emitted light changes if the source is moving relative to you. This is called the Doppler Effect, and it is easy to observe with using a source of sound that is moving relative to you.
So with a moving omnidirectional light source the light going forward actually has a shorter wavelength than the light coming out of the rear of the source.