I was interested because at the time I was an electronics technician and the production of an off-the-shelf atomic clock was big news. At that time Hewlett Packard was the big test equipment supplier. They were at the leading edge of test equipment development. I remember when they announced their test of relativity I was really impressed with how simple it was if you had a set of good clocks.

Bill Gill

C is not the speed of light in a vacuum.
C is the universal speed limit.