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Old 11-11-2010, 04:31 PM
LouisB LouisB is offline
Join Date: Apr 2000
Location: Seminole, FL
Posts: 8,517
Originally Posted by glowacks View Post
Yes, but you know your clock to be accurate because you've used the definition of a second, the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom, to build it.
I used to quote this number during presentations I put on concerning the frequency of quartz crystal units. When asked what the hell it meant, I could only shrug and say that I had no idea, nor did anyone I've ever talked to. For our purposes, I always said, one second was equal to one sixtieth part of a minute. No one ever quibbled.

How does one isolate a single atom, determine the two hyperfine levels of that atom, and make whatever measurements one must make in order to determine what the hell one second actually is? Perhaps even more importantly, how does one determine which atom one needs to isolate? There are so many things I wish I knew and so little time left to even begin.