🚀 go-pugleaf

In article <C15vp9.6x5@well.sf.ca.us> metares@well.sf.ca.us (Tom Van Flandern)  
writes:
> 
> Earlier, I wrote:
> 
> >> If [the Hubble] rate, 50-100 km/s/Mpc, is prorated down to solar system
> >> dimensions, no ... expansion is seen in planetary orbits.  The question
> >> we are discussing is, why not?
> 
> and clarke@acme.ucf.edu (Thomas Clarke) replied:
> 
> > Are you sure it would be observable?  I make out the radius of the
> > earth's orbit to be ~1.5E-11 MPc; therefore the Hubble expansion at 1 AU
> > comes out ~1.5E-9 km/sec for h=100 km/s/MPc.  The ratio of this to the
> > earth's orbital velocity is ~5.5E-11.
> 
>      Actually, the radius of the Earth's orbit is closer to 0.5E-11 Mpc.
> What we measure with radar and spacecraft ranging is the actual change in
> the mean orbital radius, not the doppler shift.  If the Earth's orbit were
> increasing at the Hubble rate of 1E-10/yr, that would be easily detectible.

I converted 8 light minutes to megaparsecs, but I forgot the 3.26 ly/parsec
factor.  Ooops.

10E-10/year of earth's orbit is about 1.5E-2km=15 meters.  Yeah, that
would be detectable by radar ranging.  I forgot about those measurements.
I guess the laser ranging of the retroreflectors on the moon would
constrain the expansion as well.

One forgets.  To quote Douglas Adams, "Space is big.  Really, really big!"
Even the solar system.
 
> 
> > Besides, maybe there has been expansion :-)  I understand there is some
> > difficulty in explaining why the earth did not freeze when the sun was
> > younger and less luminous.  If the solar system was smaller 3-4 billion
> > years ago by the 15-30% value that expansion would imply, this might
> > account for how we avoided a big freeze.
> 
>      Except that observations say the solar system is not expanding at the
> Hubble rate today.  -|Tom|-
 
Shucks!.  And I was getting all excited about solving a climatological
mystery.:-(
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
(407)658-5030, FAX: (407)658-5059, clarke@acme.ucf.edu