sci.physics.particle

On Apr 2, 9:53=A0pm, Tom Roberts wrote:
> Pmb wrote:
> > "Pentcho Valev" wrote in message
> >news:4136f86e-5fc3-4849-92e6-d42985e1f21c@c65g2000hsa.googlegroups.com...=

> > On Apr 1, 12:52 am, Tom Roberts wrote in
> > sci.physics:
> >> Anon wrote:
> >>> Because as you get closer to a massive body light is slowed down, this=

> >>> bends
> >>> the rays of light towards the massive object. The same is true of othe=
r
> >>> massive objects. That is what Einstein said.
> >> As I said before, Einstein said that in 1911, early on the
> >> then-unfinished journey to General Relativity. GR itself does not reall=
y
> >> have this property.
>
> > Note: Einstein's first work on general relativity (e.g. the equivalence
> > principle, gravitational time dilation. deflection of light, etc.) was i=
n a
> > paper published in 1907 called "On the Relativity Principle and the
> > Conclusions Drawn from it," A. Einstein, Jahrbuch der Radioaktivitat und=

> > Elektronik 4 (1907): 411-462. And contrary to Roberts claim, GR *does( h=
ave
> > this property.
>
> Had you read my full statement, you would know that I said GR has this
> property IN THE APPROPRIATE APPROXIMATION, SPEAKING LOOSELY: i.e. for a
> suitable meaning of "speed" -- not a LOCAL speed but a NON-LOCAL speed
> or a COORDINATE speed. And as I said, 'without approximation, or to
> speak more accurately, one must discuss geodesic deviation, not "light
> slowed down".'
>
> The primary fault is Valev's, as he is the one who omitted my
> explanatory text. But my original post is in this thread.
>
> > It is a very simple thing to derive. E.g.
> >http://www.geocities.com/physics_world/gr/c_in_gfield.htm
>
> That link says explicitly that the computation is the COORDINATE speed
> of light. That is, the computed value is a ratio of coordinate
> intervals, NOT what one would measure over a local distance using
> standard clocks and rulers (one always measures c when one does that).
>
> As I keep saying, and you both (Valev and PMB) keep ignoring: ONE MUST
> BE CAREFUL TO AVOID PUNS. There are multiple meanings of the word
> "speed" here and you are both oblivious to that fact. Doing physics
> requires precision in thought and word, and such unacknowledged puns
> destroy the discussion or argument.
>
> The normal meaning of "speed" is what one measures in the obvious way
> using standard clocks and rulers; with gravitation this must be over a
> local path (short enough so variations in gravitational potential can be
> ignored), so the two clocks can be synchronized. The coordinate speed of
> light can be essentially anything, and the speed of light measured over
> a non-local path can differ from c (e.g. Shapiro time delay). But if you
> call those simply "speed" you are sure to confuse your reader (and most
> likely yourself) -- that has CLEARLY happened in this thread.
>
> Tom Roberts- Hide quoted text -
>
> - Show quoted text -

Such brilliance.
I hope Tom Roberts can write a book like as "An Idiot's Guide to
General
Relativity". It would help millions immensely. But Roberts seems to
enjoy
taking poke shots at crackpots. Note crackpots are born not to learn
but to repeat the same mistakes. So as Roberts hair gets whiter as
each
year and decade passes by going into his old age, he would meet the
same
people and same argument again and again. I hope he can spend his
talent writing that book.

Or if Roberts is not a born writer. Can anyone of you write "An
Idiot's Guide
to General Relativity?"

cu