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Nist: New Optical Clock More Accurate Than Cesium
LordPhatal writes "NIST researchers have demonstrated a new kind of atomic clock that has the potential to be up to 1,000 times more accurate than today's best clock. The new clock is based on an energy transition in a single trapped mercury ion.
Basically, the accuracy of a reference clock in principle determined by making two identical clocks, starting them synchronized, and measuring how long before they drift by an average of 1 second.
This has to do with how cold your atomic fountain is, and how well you isolate the particular magnetic sublevel you define the second in terms of.
Now, if you want to move to a mercury standard clock, you can do two things: first, calculate with QED the ratio of the freqencies between the transitions in cesium and mecury of interest. I don't know if we can do this well enough for these purposes or not. Second, you can redefine the second in terms of the oscillation frequency of some mercury transition at least within the accuracy of a current cesium clock.
The important thing to note is that mand physicists don't really care about how long a second is, as much as they care that two clocks run at the same rate, even if it is wrong.
However, you can take an online tour if that floats your boat.