🚀 go-pugleaf

In article <1dhv1tINNrnh@iskut.ucs.ubc.ca> ramsay@unixg.ubc.ca (Keith Ramsay) writes:
>For example, if I ask how long tall you are, the proposal is that the
>only content which can be gathered from the question is to compare
>your height to some reference length(s). A "length" is, essentially,
>just defined by its ratios to the framework of all the other lengths
>which we can talk about-- most especially to standardized ones. But,
>if, for example, some bizarre change were to occur which affected only
>the particular phenomenon which was used to define the standard,
>leaving the ratios of most other quantities basically intact, then
>we'd surely agree to change the standard, rather than regard all the
>other quantities as having changed. (The old example was, "what if the
>platinum bar in Paris were stretched".)

What would happen if that platinum bar and a 9192631770 Hz cesium clock
were transported to some other local group of galaxies, keeping it at
the prevailing outside temperature of 2.7K?  After one third of the
trip would one see exactly the same number of clock cycles along the
length of the bar as after two thirds?  (The trip will be quite long
enough for the bar to reach thermal equilibrium.)

Light is supposed to zip along an honest meter bar in exactly
1/299792458 seconds (the bar in Paris may need an extension welded on
to make it honest at 2.7K).  Hence the above measurement should be
*exactly* 656616555/21413747 clock cycles, in round numbers about
30.6633189884983697621906152155435477966560 (more digits on demand :-),
Could this conceivably become exactly 30.6634 or 30.6632 at some point
during the trip?

With regard to bar length, assume you were carrying a variety of meter
bars of different stable materials (I have no idea what materials are
sufficiently stable for billions of years).  With regard to clock
frequency, assume you were carrying a variety of atomic clocks based on
hyperfine transitions of various elements.  And assume that the
observed change was the same to within 10% of the change for all
combinations of bars and clocks.

Given these circumstances, which parameter would you prefer to say had
changed, light speed, bar length, or clock frequency?  Or would you
prefer to say that there was no basis for choosing among these?
-- 
Vaughan Pratt