🚀 go-pugleaf

On Apr 2, 4:07 pm, Cutix <tix...@yahoo.com> wrote:
> On Apr 2, 9:53 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote:
>
> > Pmb wrote:
> > > "Pentcho Valev" <pva...@yahoo.com> wrote in message
> > >news:4136f86e-5fc3-4849-92e6-d42985e1f21c@c65g2000hsa.googlegroups.com...
> > > On Apr 1, 12:52 am, Tom Roberts <tjroberts...@sbcglobal.net> 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 other
> > >>> 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 really
> > >> have this property.
>
> > > Note: Einstein's first work on general relativity (e.g. the equivalence
> > > principle, gravitational time dilation. deflection of light, etc.) was in 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( have
> > > 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

> 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?"

Roberts, together with Jean-Marc Levy-Leblond, should first write a
guide to special relativity:

http://groups.google.ca/group/sci.physics.relativity/browse_frm/thread/8034dc146100e32c
Tom Roberts, Feb 1 2006: "If it is ultimately discovered that the
photon has a nonzero mass (i.e. light in vacuum does not travel at the
invariant speed of the Lorentz transform), SR would be unaffected but
both Maxwell's equations and QED would be refuted (or rather, their
domains of applicability would be reduced)."

http://o.castera.free.fr/pdf/chronogeometrie.pdf
Jean-Marc Levy-Leblond: "D'autre part, nous savons aujourd'hui que
l'invariance de la vitesse de la lumiere est une consequence de la
nullite de la masse du photon. Mais, empiriquement, cette masse, aussi
faible soit son actuelle borne superieure experimentale, ne peut et ne
pourra jamais etre consideree avec certitude comme rigoureusement
nulle. Il se pourrait meme que de futures mesures mettent en evidence
une masse infime, mais non-nulle, du photon ; la lumiere alors n'irait
plus a la "vitesse de la lumiere", ou, plus precisement, la vitesse de
la lumiere, desormais variable, ne s'identifierait plus a la vitesse
limite invariante. Les procedures operationnelles mises en jeu par le
"second postulat" deviendraient caduques ipso facto. La theorie elle-
meme en serait-elle invalidee ? Heureusement, il n'en est rien ; mais,
pour s'en assurer, il convient de la refonder sur des bases plus
solides, et d'ailleurs plus economiques. En verite, le "premier
postulat" suffit, a la condition de l'exploiter a fond."

http://o.castera.free.fr/pdf/onemorederivation.pdf
Jean-Marc Levy-Leblond: "This is the point of view from wich I intend
to criticize the overemphasized role of the speed of light in the
foundations of the special relativity, and to propose an approach to
these foundations that dispenses with the hypothesis of the invariance
of c....We believe that special relativity at the present time stands
as a universal theory discribing the structure of a common space-time
arena in which all fundamental processes take place....The evidence of
the nonzero mass of the photon would not, as such, shake in any way
the validity of the special relativity. It would, however, nullify all
its derivations which are based on the invariance of the photon
velocity."

Pentcho Valev
pvalev@yahoo.com