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Article View: sci.physics.relativity
Article #7273

Re: Why does light bend under gravity?

#7273
From: PD
Date: Tue, 25 Mar 2008 21:59
312 lines
15790 bytes
On Mar 25, 4:41 pm, kenseto <kens...@erinet.com> wrote:
> On Mar 25, 8:45 am, PD <TheDraperFam...@gmail.com> wrote:
>
>
>
> > On Mar 25, 8:20 am, kenseto <kens...@erinet.com> wrote:
>
> > > On Mar 24, 3:36 pm, PD <TheDraperFam...@gmail.com> wrote:
>
> > > > On Mar 24, 3:28 pm, kenseto <kens...@erinet.com> wrote:
>
> > > > > On Mar 24, 12:12 pm, PD <TheDraperFam...@gmail.com> wrote:
>
> > > > > > On Mar 24, 11:19 am, kenseto <kens...@erinet.com> wrote:
>
> > > > > > > On Mar 24, 9:50 am, PD <TheDraperFam...@gmail.com> wrote:
>
> > > > > > > > On Mar 24, 9:44 am, "kens...@erinet.com" <kens...@erinet.com> wrote:
>
> > > > > > > > > On Mar 20, 10:50 am, PD <TheDraperFam...@gmail.com> wrote:
>
> > > > > > > > > > On Mar 20, 9:21 am, "Androcles" <Headmas...@Hogwarts.physics> wrote:
>
> > > > > > > > > > > "PD" <TheDraperFam...@gmail.com> wrote in message
>
> > > > > > > > > > >news:4c53fc2e-bcfd-425d-a7ed-afb8933257d2@e60g2000hsh.googlegroups.com...
> > > > > > > > > > > On Mar 20, 3:02 am, Pentcho Valev <pva...@yahoo.com> wrote:
>
> > > > > > > > > > > > On Mar 18, 7:29 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote in
> > > > > > > > > > > > sci.physics.relativity:
>
> > > > > > > > > > > > > John C. Polasek wrote:
> > > > > > > > > > > > > > On Sun, 16 Mar 2008 17:14:22 GMT,TomRoberts
> > > > > > > > > > > > > > <tjroberts...@sbcglobal.net> wrote:
> > > > > > > > > > > > > >> [Ignore Valev when he brings up Pound-Rebka and similar
> > > > > > > > > > > > > >> experiments -- they do not measure speed.]
> > > > > > > > > > > > > > I think, in a very important way, the experiment did effectively
> > > > > > > > > > > > > > measure light speed, even though the authors thought frequency was
> > > > > > > > > > > > > > reduced on the way up ("On the Weight of Photons" iirc).
> > > > > > > > > > > > > > The Mossbauer filter on a speaker cone was oscillated at a minute
> > > > > > > > > > > > > > rate, and spectral re-centering was achieved by the Doppler effect. On
> > > > > > > > > > > > > > the up-stroke, the velocity neutralized the speedup of light as it
> > > > > > > > > > > > > > left the gravity well.
>
> > > > > > > > > > > > > Think about it -- there is no time synchornization, and if the effect
> > > > > > > > > > > > > were due to a change in speed there's no way for the apparatus to be
> > > > > > > > > > > > > sensitive to it; that is, there's no "nominal distance" relative to
> > > > > > > > > > > > > which a "speed change" could be measured. Their observations are
> > > > > > > > > > > > > consistent with a change in frequency (measured via Doppler), and say
> > > > > > > > > > > > > nothing at all about any change in speed. Whether or not the speed
> > > > > > > > > > > > > changed in addition to the frequency cannot be answered by this
> > > > > > > > > > > > > particular experiment.
>
> > > > > > > > > > > > I would agree with you Roberts Roberts if at this place you did not
> > > > > > > > > > > > always stick your head in the sand, expose other parts of your body
> > > > > > > > > > > > and fail to explain clearly the two incompatible implications of Pound-
> > > > > > > > > > > > Rebka result f'=f(1+V/c^2). Let me do this for you:
>
> > > > > > > > > > > > The Pound-Rebka result f'=f(1+V/c^2) implies that:
>
> > > > > > > > > > > > (1) the speed of light in a gravitational filed is VARIABLE as
> > > > > > > > > > > > Einstein suggests in his 1920 "Relativity" and obeys Einstein's 1911
> > > > > > > > > > > > equation c'=c(1+V/c^2), whereas the wavelength remains constant. The
> > > > > > > > > > > > application of Einstein's equivalence principle converts c'=c(1+V/c^2)
> > > > > > > > > > > > into c'=c+v, an equation given by Newton's emission theory of light,
> > > > > > > > > > > > where v is the relative speed of the light source and the observer in
> > > > > > > > > > > > the absence of a gravitational field. Einstein's 1905 light postulate
> > > > > > > > > > > > (c'=c) is false.
>
> > > > > > > > > > > > (2) the speed of light in a gravitational field is CONSTANT and obeys
> > > > > > > > > > > > the equation c'=c, in contradiction to what Einstein claims in his
> > > > > > > > > > > > 1920 "Relativity". The wavelength is variable and obeys the equation
> > > > > > > > > > > > L'=L/(1+V/c^2). The application of Einstein's equivalence principle
> > > > > > > > > > > > leads to the conclusion that the equation c'=c+v given by Newton's
> > > > > > > > > > > > emission theory of light is wrong whereas Einstein's 1905 light
> > > > > > > > > > > > postulate (c'=c) is correct.
>
> > > > > > > > > > > > This is a minimum explanation Roberts Roberts - more could be said in
> > > > > > > > > > > > favour of (1) and against (2).
>
> > > > > > > > > > > | The above is incorrect in a number of ways.
> > > > > > > > > > > | 1. The Pound-Rebka experiment in no way implies that the wavelength is
> > > > > > > > > > > | constant. In fact, the opposite is true.
>
> > > > > > > > > > > What does it imply, then, now that we know what it doesn't imply?
>
> > > > > > > > > > It implies that the frequency and wavelength are shifted and the local
> > > > > > > > > > speed of light remains c.
>
> > > > > > > > > No..... it implies that frequency is shifted and wavelength remains
> > > > > > > > > constant
>
> > > > > > > > Why would it imply something that is counter to measurement?
> > > > > > > > Measurement shows that the wavelength is clearly shifted, as well as
> > > > > > > > the frequency.
>
> > > > > > > The wavelength of a specific source such as the sodium is universal as
> > > > > > > measured by all obserers.
>
> > > > > > We've been through that. It is not universal.
>
> > > > > Sure it is universal when everybody measures his sodium source to have
> > > > > the same wavelength.
>
> > > > We've already discussed that too. It's not universal if a bunch of
> > > > observers look at the *same* source and see that the wavelengths are
> > > > different for all observers.
>
> > > yes it is universal....different observers will determine different
> > > speeds of the incoming light from the same light source. This makes
> > > light agrees with the normal physics that speed is of anything is
> > > dependent on the motion of the source or the detector.
>
> > The speed of anything that moves slower than light *does*
> > depend on the motion of the source or detector. That is *still* >true in
> > relativity. But it is NOT true for anything moving at the speed > of light.
>
> It is also true for anything moving at any speed including the speed
> of light. All one needs to do is to acknowledge that wavelength is
> universal.

To acknowledge that wavelength is universal is to deny the direct
measurement of the wavelength that says that the wavelength is
different. To acknowledge something in the face of direct experimental
evidence is bordering on lunacy.

>
> > Here is how the observed speed v' depends on the motion of the source
> > or detector u:
>
> > v' = (v + u)/(1 + v*u/c^2)
>
> This equation is useless. It assumes that the speed of incoming light
> is a universal constant.

1. It has been directly confirmed to give *exact* results (not just
"less than c") for objects that are traveling less than c. This
demonstrates that the formula works and matches experiment
*numerically*. Note that another equation would not produce the same
numbers and so would not agree with experiment. The above equation has
been *confirmed* experimentally.
2. It also is directly confirmed to accurately predict the results of
2-way light speed measurements and 2-way and 1-way isotropy
experiments. There is no other equation (unless you have one available
from your theory that gives v' in terms of v and u) that generates
predictions that match the results of those experiments.
3. The "normal" physics equation is v' = v + u. This has been
experimentally proven to be *wrong* in predicting the results
mentioned in both (1) and (2) above. To insist that the "normal
physics" equation should apply anyway, despite direct experimental
evidence that it does NOT work is bordering on lunacy.

>
> > If you take ANY v and ANY u that is less than c, you will find that in
> > the above expression, v' will be different than v. That means that the
> > speed observed in such cases depends on the motion of the detector.
>
> > However if you take v=c and then take ANY u (any motion of the
> > detector or source at all), you will find that v' = c still. (Go
> > ahead, do the algebra). This means that in this case, v' = v, and the
> > speed of the signal does NOT depend on the motion of the detector.
>
> > Note the *same* equation predicts BOTH consequences. The fact that you
> > find this mysterious and confusing is neither here nor there.
>
> > > > What you call "universal" is really "what you'll measure only if you
> > > > obey the strict rule that the only source you can look at is one that
> > > > is at rest relative to you." That is like coming up with a universal
> > > > rule for cats by making everyone look only at the cat in their own
> > > > lap.
>
> > > > > >The same sodium source,
> > > > > > recognized as sodium by all observers, has *different* wavelengths for
> > > > > > different observers.
>
> > > > > No....all light sources in the observer's frame will have a defined
> > > > > wavelength.
> > > > > The incoming light becomes a new light source in the
> > > > > observer's frame
>
> > > > Already covered that, too Ken. You're repeating yourself. There's
> > > > nothing in the measurement process that makes it a new source -- it is
> > > > still the same source for everyone, and it is still recognized by
> > > > everyone as a sodium.
>
> > > > > and thus it is defined to have a new wavelength. The
> > > > > new wavelength can be used to determine the origin of the incoming
> > > > > light.
>
> > > > You'll notice that you never use the new wavelength in anything.
>
> > > Wrong I use the new wavelength to determine the source of the incoming
> > > light as described by you and from that I find the universal
> > > wavelength of that light.
>
> > Sorry, that doesn't work.
>
> Sure it works perfectly. Consider the following:
> 1. There is a constant source of water wave in a pond.
> 2. The frequency is N and the wavelength is L.
> 3. You are stationary wrt the source the speed of arrival of the
> incoming wave is N*L
> 4. You swim toward the source. The number of wave arring at you is (N
> +n) and the wavelength remains L. Therefore the arriving speed of the
> water wave is L(N+n).

But here I'm measuring the wavelength by counting wave crests that
pass per unit time. That's measuring *frequency* not wavelength.
What's missing in the above measurement is something that measures
*wavelength* directly. What's done with light is a device that
measures wavelength *directly*. In the pond example, if you actually
DID measure the wavelength directly (and you could, with an
appropriate water wave diffraction grating), you would indeed find
that the wavelength of the wave has not changed. You could confirm
that *directly*, rather than just deducing it from an assumption that
the wavelength remains L. You could *check* that the wavelength
remains L with the grating, and you would find that it is indeed
unchanged. And in the case of the water waves, it is indeed true that
the wavelength is unchanged, the frequency is shifted, and the speed
of the wave relative to the observer is changed.

However, light doesn't behave like water. If you actually *measure*
the wavelength of the light directly (with a grating), you find that
-- unlike water waves -- the wavelength DOES change. And the frequency
changes also, by direct measurement using a different means. But now
if you multiply those two numbers, the changed wavelength and the
changed frequency, you find that the wave speed is still c. Water
waves do NOT behave the same way as light.

> 5. You swim away from the source. The number of wave arriving at you
> is (N-n) and the wavelength remains L. Therefore the arriving speed of
> the water wave is L(N-n).
>
> So you see that the wavelength does not change...what is changing is
> the arriving speed of the incoming water waves.
>
> Ken Seto
>
> > If I measure the length of a Toyota to be 12 ft, 3 inches, and I
> > identify it as a Toyota Corolla by the emblem on the trunk, and you
> > look up in a book that says that the standard length of a Toyota is 12
> > ft, 5 inches, that does NOT make the Toyota just looked at 12 ft, 5
> > inches. It is still 12 feet, 3 inches. I just measured it. The 12 ft,
> > 5 inch number must apply to a different set of conditions than what I
> > have here.
>
> > What you are suggesting doing with a sodium source is measuring the
> > wavelength of a moving source to be 613 nm, using the wavelength
> > ratios to determine that it is sodium, and then dropping the 613 nm
> > *measured* and using the 589 nm for a
>
> ...
>
> read more »
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From: PD <TheDraperFamily@gmail.com>
Newsgroups: sci.physics.relativity,sci.physics,sci.physics.particle,fr.sci.physique,sci.astro
Subject: Re: Why does light bend under gravity?
Date: Tue, 25 Mar 2008 14:59:14 -0700 (PDT)
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