Re: gravitational bending of light, surprising?

On May 19, 2:26 pm, Albertito <albertito1...@xxxxxxxxx> wrote:
On May 19, 8:01 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:



On May 19, 1:46 pm, Albertito <albertito1...@xxxxxxxxx> wrote:

On May 19, 7:16 pm, PD <TheDraperFam...@xxxxxxxxx> wrote:

On May 19, 12:50 pm, Albertito <albertito1...@xxxxxxxxx> wrote:

On May 19, 5:19 pm, carlip-nos...@xxxxxxxxxxxxxxxxxxx wrote:

mluttg...@xxxxxxxxx wrote:
On 18 mai, 18:37, carlip-nos...@xxxxxxxxxxxxxxxxxxx wrote:
mluttg...@xxxxxxxxx wrote:

[...]

Do you agree that a photon can behave as a corpuscule
having a kinetic energy E = mc^2 = hNu, where Nu is
its frequency?
Depends what you mean by "m."
Do you agree that m represents hNu/c^2?

Sorry, but this still depends on what you mean by "m."

Do you agree that, if the author of the paper had
used in his calculation E=mc^2 instead of E=mc^2/2
for the photon energy, he would have obtained exactly
the GR result?
No, of course not!  A basic feature of Newtonian gravity is
that the acceleration of an object in a gravitational field
is independent of its mass.  You can use a mass of mc^2,
or 1/2 mc^2, or you can say the photon has the mass of your
pet cat.  As the article you cite points out,  "As expected,
the light particle mass m cancels out."
(You can, of course, cheat and use different values of m in
different steps of the calculation.  But then you're no longer
talking about anything resembling Newtonian gravity.)

[...]

There is one remark I can't agree with:
"You can use a mass of mc^2, or 1/2 mc^2, or you can say the
photon has the mass of your pet cat.  As the article you cite
points out,  "As expected, the light particle mass m cancels out.""
Indeed, m cancels out in the derivation, but *not* the coefficient,
which is 1/2 when strangely assuming, like the author, that the
photon energy is (1/2) mc^2.
But when assuming that the photon energy is mc^2, which seems
to be much more justified, the coefficient is 1. And with that
coefficient, *which doesn't cancel out*, one gets the same
deflection as GR.

If you are finding an answer that depends on the mass you attribute
to the photon, you are doing something wrong.  This is completely
elementary.  All you need to know is Newton's second law, F=ma,
and Newton's law of gravity, F=GMm/r^2.  If you set these equal,
m drops out -- the acceleration of a body in a gravitational field
is independent of its mass.  This is the principle of equivalence, and
it goes back at least to Galileo.  It's the reason Cavendish and von
Soldner were able to do the cpmutation 200 years ago; they didn't
need to know anything about the mass of light, because the mass
is irrelevant to the answer.

But, the spin of the particle is not irrelevant. Any
derivation of the gravitational deflection angle of
light in Newtonian gravity claiming it is half the
observed angle is an incorrect fake.
That fake means
you are assuming a fermion (spin = 1/2) travelling at
speed c, instead of a photon (spin = 1) travelling
at c.

Ah. Having fun just making stuff up? Who do you think you're fooling?

Light is not composed of fermions, therefore
the gravitational angle predicted under NG being half
the observed angle is an incorrect computation. When
you claim that E = (1/2)mc^2 it is clear that you are
considering a fermion travelling at c.
The principle
of equivalence makes the mass m to drop out, but the
spin = 1/2 still remains.

Ah, but maybe the factor of 1/2 doesn't come from fermion spin
because, as you say, a photon doesn't have spin 1/2. Maybe the 1/2
comes from the 1/2-wit that came up with that idea.

The spin of a macroscopic body is the average spin of its
contituent particles.

This isn't right.

Suppose a body of mass M is composed
by p particles of spin = 1/2 and q particles of spin=1. Then,
its spin is s = (p/2 + q)/(p + q)

And this isn't right either, but as long as you're on a tear making
things up, you might as well make something else up.

Keep in mind that the factor of 1/2 that you are worried about
concerns *light*, NOT a macroscopic body of mass M.

Stars of different ages exhibit different macroscopic spins.

That is true. And it has nothing to do with the average of the spins
of the constituent particles.

An old star has consumed nearly all its hidrogen, and there is
a lot of helium.

This is also true, which again has nothing to do with angular momentum
OR spin.

This means that old stars have a macroscopic
spin closer to 1/2 than new stars.

And that is not only made up out of thin air, but is factually wrong.

Bodies with spins near 1/2
gravitate slower than bodies with spins near 1.

This is another incorrect statement.

IOW, bodies
with spins near 1 free fall faster than bodies with spins
near 1/2. That explains galaxy rotation curves. Old stars are
in average closer to the galactic center and they orbit slower
than new stars that are formed in average far away from the
galactic center and they orbit faster.

At one time, you at least attempted to give the appearance of making
sense. Now you are quite happy to just compose vocabulary salad as a
free-association exercise, not willing to make the effort to try
harder.

At this point you should perhaps be asking to what end your time here
is being invested. Since you aren't really interested in devoting
substantial effort to it anymore, is it really worth your time?

, and this is a rational
number within the range [1/2, 1]. Now, we are ready the test
the Equivalence Principle:

Let two bodies of equal or different masses in free fall,
from the same altitude, but with different spins, s_1 = 4/5,
and s_2 = 2/3. Which body will fall faster?

For a photon (spin=1)
the correct assumption is E = (1)mc^2. The principle
of equivalence makes the mass m to drop out, but the
spin = 1 still remains.

Regards

You claim that you are getting a different answer depending on
what mass you attribute to a photon.  This means one of two things:
you're not using Newtonian gravity (or anything even vaguely like
it), or you've made a mistake in your calculation.  My guess is the
latter -- I suspect you're coming in in the middle of a computation
that already used one value of m, and switching to another half way
through, effectively treating a photon as an object that has two
different masses in two different parts of the calculation.  This is
just a guess, though; I have enough homework to correct without
adding this to my list.

Again, the issue is really very simple.  Honest.  In Newtonian gravity,
acceleration is independent of the mass of the object undergoing
acceleration.  You can attribute whatever mass you like to light;
if your answer depends on that choice, you've made a mistake.

Steve Carlip

.

Relevant Pages

  • Re: Ye Old One. The GR Expert.LMAO.
    ... space" (really "bent spacetime"). ... its gravity comes into the two-body calculation. ... mass attract one another. ... A photon follows a "straight line" in spacetime. ...
    (talk.origins)
  • Re: Nobel Prize for David Thomson?!
    ... > demonstrating how Aether is curved by the presence of bound mass. ... >> It seems as though you based your hypothesis on the Aether Relativity ... Energy from a photon striking matter causes matter to move. ... So then your theory actually offers no explanation for gravity? ...
    (sci.physics.particle)
  • Re: Nobel Prize for David Thomson?!
    ... > demonstrating how Aether is curved by the presence of bound mass. ... >> It seems as though you based your hypothesis on the Aether Relativity ... Energy from a photon striking matter causes matter to move. ... So then your theory actually offers no explanation for gravity? ...
    (sci.physics)
  • Re: Nobel Prize for David Thomson?!
    ... > demonstrating how Aether is curved by the presence of bound mass. ... >> It seems as though you based your hypothesis on the Aether Relativity ... Energy from a photon striking matter causes matter to move. ... So then your theory actually offers no explanation for gravity? ...
    (sci.physics.relativity)
  • Re: How does light, which has no mass, get pulled into a black hole?
    ... Newtonian gravity made another prediction about how ... light would be affected by gravity, if it had mass of any value. ... these two predictions did not agree. ... THE PHOTON IS A SPECIAL CASE FOR ITSELF!!! ...
    (sci.physics)