[time-nuts] Primary standard again

Rick Karlquist richard at karlquist.com
Tue Feb 23 22:25:38 UTC 2010


If you want to get technical, the frequency of a cesium standard
also depends on the gravitational acceleration, but for relativistic
reasons, not newtonian physics.  Any decent cesium is accurate
enough that it will noticably speed up at NIST in Boulder.  NIST's
best clocks speed up noticibly if you move them from the ground
floor to upstairs.

The pendulum is also not primary because it's length has to be
calibrated.  A cesium kit does not require any calibrated parts,
including the microwave cavity, which only has to be symmetrical.

Rick Karlquist N6RK


J. Forster wrote:
> A REAL "primary standard" is something that you can assemble the kit of
> parts anywhere in the Universe, flip the switch, and get exactly the same
> time interval as anywhere else.
>
> That obviously does NOT apply to the pendulum, as it depends on the value
> of G.
>
> -John
>
> ==================
>
>
>> I suppose a pendulum can be a primary standard at some accuracy.  Using
>> the "kit of parts" analogy, if one builds the pendulum and operates it
>> at
>> sea level, the period of the pendulum is entirely determined by the
>> physical dimensions and the gravitational constant.
>
>
>
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