Re: New analysis puts dark matter back into elliptical galaxies (Forwarded)

In message <2pb2f.220$S43.44823@xxxxxxxxxxxxxxxxxxxxx>, Greg Neill <gneillREM@xxxxxxxxxxxxxxxxxx> writes 
"John Curtis" <john@xxxxxxxxx> wrote in message
news:1128870346.562255.85240@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx


Greg Neill wrote:
>
> Of course, we know today that
> a simple change of model (to a heliocentric one) does away with
> all the complications, and the problem reduces to calculations
> with simple conic section functions.
>
The change of models is a slow process. Ptolemaics ruled for 1000
years. Heliocentric model is still in place after 500 years. My
hope is that the need for fudge factors such as "dark matter"
will hasten the transition to a galactic model. John Curtis


I wouldn't recommend holding ones breath whist waiting.
No one is likely to select a frame of reference that
complicates calculations for no benefit.  Dark matter
plays no role in solar system dynamics or calculations.


Could dark matter play a role in the motion of Oort cloud objects (if they exist)? Otherwise only the nearest stars do so. Galactic motion is completely irrelevant.
I wonder if there's some confusion between the motions and the frames of reference of those motions. For instance, solar system bodies move on heliocentric paths, because that's overwhelmingly the local centre of mass, but you're free to choose whatever frame of reference is convenient.
For instance, I once saw a NASA animation of the paths of the Voyager probes from a geocentric viewpoint, with a stationary Earth. Looked really weird :-) I don't recall the reason for using that frame.
--
Boycott Yahoo!
Remove spam and invalid from address to reply.
.

Relevant Pages

  • Re: Kepler ,Newton and orbital geometry
    ... imaging to illustrate Kepler's explanation of apparent retrograde motion, ... We're hardly limited to one frame of reference, ...
    (sci.astro.amateur)
  • Re: Gravity Probe B-failure or special new success?
    ... with a parenthetical reference to the motion of our gyroscope rotors. ... reference corresponding to zero velocity in the aether. ... corresponds to an effect of a fixed frame - the same one identified by ...
    (sci.physics)
  • Re: Kepler ,Newton and orbital geometry
    ... effects given by Einstein's Special and General theories of relativity ... Similarly, strictly speaking, all motion is "relativistic," and once I had ... long walk from the frame of reference of an observer stationary with respect ...
    (sci.astro.amateur)
  • Re: Is physics really a matter of belief?
    ... >> frame of reference. ... Frames of reference are human constructs whereby situations are too ... according to the reality of nature in the motion of ... the universe, the earth is moving at>G, then the ball still may have ...
    (sci.physics)
  • Re: New analysis puts dark matter back into elliptical galaxies (Forwarded)
    ... Galactic motion is ... I suspect that any dark matter influence would be very slight. ... The interactions of the Oort cloud objects themselves would ... > really weird :-) I don't recall the reason for using that frame. ...
    (sci.astro)