Re: [Phys-L] absolute "motion"

[John Denker <jsd@av8n.com>]

On 08/23/2013 06:09 AM, jbellina wrote:

> jd did have a link to stellar aberration

I should have, but I didn't.  I mentioned only parallax and rotation.
It was BC who introduced aberration into the discussion.  Parallax
and aberration are very different things.  The physics is different,
and the observed consequences are different in magnitude and phase.
BC's suggestion is better than mine, because parallax is a much 
smaller effect.  It is smaller by a factor of 20 for the nearest 
stars, and verrry much smaller than that for distant stars.

On 08/23/2013 12:10 AM, Bernard Cleyet wrote:

> > stellar aberration [...]  discovered while G. G. alive

The connection of Galileo to the first observation of aberration
is indirect, but not a coincidence, since there is no hope of 
seeing aberration without a telescope.  On the third hand, I'm 
not sure that observation counts as "discovery" if the observers
completely misunderstand what they're seeing.

The history of this is rather ugly.  In the 1600s, folks
went looking for parallax and saw (mostly) aberration instead.
Both effects are small and difficult to observe, and folks
were working with the wrong theory.  It took them many decades
to get it all sorted out.

This has some pedagogical significance, insofar as it is
reason #437 why the "historical approach" is a bad way to 
organize a physics course.  Students (especially at the
introductory level) need the best evidence, not the most
ancient evidence.
  http://www.av8n.com/physics/best-evidence.htm

For advanced students who know enough about history and
know enough about physics to do things properly -- and
have the time and inclination -- the story of aberration 
and parallax says a lot about how science is really done.
This is very different from the outrageous "poster" version 
of "the scientific method" that is taught in many schools.
  http://www.av8n.com/physics/scientific-methods.htm#sec-poster