# Is an atomic clock's measurement principle independent of what a light clock provides

Special Relativity has the light clock which basically counts how often a photon goes forth and back along a fixed distance.

Our most accurate clock, defining the second (at least as of today), is an atomic clock.

These seem to be two completely independent ways to measure time and define a second. Are they really independent or are there hard mathematical rules that transform the frequencies relevant in the atomic clock into the distance covered by the speed of light?

If they are independent, how can we be sure they match up?

• Isn't the rule just $\lambda\nu=c$? – probably_someone Jun 13 '18 at 19:43
• What do you mean by "independent"? They both measure time after all. – ACuriousMind Jun 13 '18 at 19:49
• Well, both measure something. With "independent" I mean that we would have to establish that both measure the same time by experiment. – Harald Jun 15 '18 at 11:20