sci.physics.particle

On Mar 7, 7:26=A0pm, va...@cox.net wrote:
> On Mar 6, 9:02=A0pm,pmb wrote:
>
>
>
>
>
> > On Feb 26, 2:18=A0am, va...@cox.net wrote:
>
> > > On Feb 25, 10:03=A0pm,pmb wrote:
>
> > > > 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 mass=
ive
>
> > > > > > 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 =
agrees
> > > > > >> with measurements to part-per-million accuracy over an enormous=
range.
>
> > > > > > 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 i=
s
> > > > 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 -
>
> > > > - Show quoted text -
>
> > > 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
>
> > > Bruce- Hide quoted text -
>
> > > - Show quoted text -
>
> > 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

Nice to hear from you Bruce. What has grabbed your attention in
physics lately if not gr?

Best wishes

Pete