Re: Dark matter/energy - is it real?


Paul Colquhoun wrote:
On Tue, 04 Apr 2006 11:12:49 -0600, Aaron Bergman <abergman@xxxxxxxxxxxxxxxxxx> wrote:
| In article <1144166853.339030.91390@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
| "dwight.thieme@xxxxxxxxx" <dwight.thieme@xxxxxxxxx> wrote:
|
|> James Nicoll wrote:
|> > In article <1144165833.973391.307260@xxxxxxxxxxxxxxxxxxxxxxxxxxxx>,
|> > dwight.thieme@xxxxxxxxx <dwight.thieme@xxxxxxxxx> wrote:
|> > >
|> > >Define the meter to be the distance between the Earth and Moon times
|> > >some constant. Define the second in an analogous fashion. How is a
|> > >change in the speed of light going to affect these parameters?
|> > >
|> > No idea but that particular definition would make me want to
|> > smack the definers. No only does the distance change over the course
|> > of a month but the system is evolving, so you would never get the same
|> > answer twice.
|>
|> I just made it up, actually. So feel free to smack me :-) Now how is
|> a change in the speed of light going to change the dimensions or period
|> of a gravitationally bound system?
|
| Well, in one system of units, the gravitational flux from a rotating
| system will contain a 'c'. On the other hand, in a different set of
| units, it won't.
|
| If you say that 'c' changes in the context of the first set of units
| (ie, the dimensionless ratio of c to the standard unit of speed
| changes), then the flux would change. if you used the second set of
| units, it wouldn't.


I think that if you did a unit breakdown ("dimensional analysis"? This
is going back 20+ years for me) you will find that the second example
you give does still have the speed of light in it, but the values of
other unit were chosen so that 'c' has a value of 1. This is a bit
sloppy and results in equations where the expressions on the left and
right side of the '=' have different units.

The point is that a change in the speed of light won't change the
orbital parameters in a way that cancels everything out as claimed in
the case of a meter stick made out of electromagnetically bonded atoms.
So this system could in principle be used to detect a change in the
speed of light, ie, a change in the speed is 'meaningful'.

.

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