sci.physics.particle

On Mar 6, 9:02=A0pm, pmb wrote:
> On Feb 26, 2:18=A0am, va...@cox.net wrote:
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> > On Feb 25, 10:03=A0pm, pmb wrote:
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> > > On Feb 25, 2:24=A0pm, "Paul B. Andersen"
>
> > > wrote:
> > > > Juan R. Gonz=E1lez-=C1lvarez skrev:
>
> > > > > Tom Roberts wrote on Mon, 25 Feb 2008 15:47:04 +0000:
>
> > > > >> The best model we have for the propagation of light near a massiv=
e
>
> > > > > no.
>
> > > > >> object like the sun is GR, in which the curvature of spacetime is=
the
> > > > >> important aspect in determining the path light follows. And it ag=
rees
> > > > >> with measurements to part-per-million accuracy over an enormous r=
ange.
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> > > > > Theories without spacetime curvature also agree with that.
>
> > > > Could you name one of those theories, please?
>
> > > Personally I know of no such theories. However spacetime curvature is
> > > not neccesary for light deflection in a gravitational field. So long
> > > is there is a gravitational field present, i.e. non-vanishing
> > > connection coefficients, then a particle can be deflected. A uniform g=
-
> > > field is a perfect example. The spacetime curvature associated with a
> > > uniform gravitational field is zero and yet a beam of light will be
> > > deflected. Geometrically speaking the deflection is described as the
> > > observer corresponding to a frame of reference for which a geodesic
> > > represents a non-straight line in space, i.e. one changes from
> > > Minkowski coordinates to "curvilinear" coordinates. Spacetime
> > > curvature is only neccesary when geodesic deviation is expected.
>
> > >Pete- Hide quoted text -
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> > > - Show quoted text -
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> > HiPete
>
> > I remember Kip Thorne commenting, in his non-mathematical book on the
> > history of gravitational physics, that he occasionally liked to use
> > teleparallel gravity to evaluate gravitational wave phenomena.
> > Teleparallelism is a GR equivalent.
>
> >http://en.wikipedia.org/wiki/Teleparallelism
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> > Bruce- Hide quoted text -
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> > - Show quoted text -
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> Hi Bruce
>
> Thanks. I've heard of that but have not had the time to learn about
> it. Other subjects have taken a higher priority lately. Thanks for
> reminding me of it. Do you know much about this subject? How is
> Schitz's "Gravity from the ground up?" going? Have you finished
> reading it? If so how did you like it?
>
> Best wishes

Hi Pete

The limit of my GR knowledge is founded in the metric equations which
I learned to use when I worked through Edwin's book. I havn't finished
'Gravity from the ground up' because I've temporarily lost the drive
to further my knowledge of gravitational physics. Hopefully I'll get
it back. This thread begins with the pronouncement to 'forget about
curved spacetime' because the path of light, in a gravitational field,
is a function of 'light has mass'. Apparently the originator of the
thread has a problem understanding the purpose of scientific
theoretical models. Which is to accurately make predictios wrt natural
phenomena that can be empirically confirmed. What's important is
accuracy within a domain of applicability and usefulness for doing
scientific analysis. I think that jives with what Thorne was saying
when he sometimes prefers to use the teleparalel equivalent to GR for
analyzing gravitational wave phenomena. That's how I see it.

Best wishes

Bruce


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> Pete- Hide quoted text -
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