How Do They Measure Clock Accuracy?

There have been a number of experiments using super-accurate clocks to measure time dilation. In one case they flew them on planes and showed they disagreed after landing. In another they put one atop a water tower and one at the base (light moves slower the deeper in a gravity well thus time moves differently).

I suppose it is a nod to the accuracy of these clocks that they can discern this difference which, in these cases, is quite small.

Are you thinking of this amateur experiment?

I’m telling you, you gotta go look at leapsecond.com.

At Project GREAT: General Relativity Einstein/Essen Anniversary Test you can read about the time dilation experiment this guy took his kids along for.

(Sorry; I completely mis-read the title).

But as long as I’m here, I’d like to add that we trust these clocks because Quantum Mechanics has held up remarkably well as a theory; I’m tempted to state it as a fact, but I’m wishy washy.