Quote by pervect
OK, I see where you're coming from now: if you assume that G and hbar remain constant, the planck length is just
[tex]\sqrt{\frac{G \bar{h}}{c^3}}[/tex]
so that's where your factor of sqrt(8) came from.
As far as what I had in mind, if 1 new meter = 2 old meters, then
c = 3e8 old meter / second = 1.5e8 new meter / second
so doubling the meter halves the "speed of light" from 3e8 "old meters" per second to 1.5e8 "new meters"/ second.

that doesn't quite work for me. i think that, if all of the dimensionless parameters remain constant,
c = 299792458 old_meters/old_second = 299792458 new_meters/new_second
and the new_second cannot be the same as the old_second if the meter had changed.
but i think we (as well as Duff) agree: ain't no operational difference. a change in
c (or in
G or
h or any other sole dimension
ful "constant") is not merely impossible, but is functionally meaningless.
i still don't know what to think of this inflationary universe theory where the universe expands faster than
c at some time in its past.