Thread: How fast is gravity? View Single Post
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 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 $$\sqrt{\frac{G \bar{h}}{c^3}}$$ 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 dimensionful "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.