Gravitons VS General Relativity.

**Gordon D. Pusch**

(Starblade Darksquall) writes:

There seems to be a very big split between those who beleive that
gravity is a force between two bodies mediated by the graviton 2-boson
and can be unified with the other forces, and those who beleive that
gravity is the bending of timespace, and that freefall can be taken to
be a proper reference frame.

There is no such "conflict," any more than there is a "conflict" caused by
a quantum-mechanical object exhibiting both "wave-like" and "particle-like"
properties. The "particle" picture is what is appropriate when one is
discussing quatum particles exchanging a small number of gravitons,
so that quantum effects are important; the "curved spacetime" picture
is appropriate in the classical limit when one has a huge enough number
of gravitons that one can approximate them as a classical "field."
A proper quantum theory of gravitation and spacetime will presumably
smoothly interpolate between these limits, just as quantum mechanics
smoothly interpolates between "particle-like" and "wave-like" behaviors
as the allowed resolution of the measurement apparatus is dialed from
"fine" spatial resolution (and necessarily coarse momentum resolution)
to fine momentum resolution (and necessarily course spatial resolution).
The "loop-space approach" to quantum fields being pursued by Lee Smolin
and others is perhaps a crude initial attempt at such a description.

But there is a test we can do which will distinguish between them.

Sorry, no.

If gravity is a force that can be mediated by graviton particles, then
in a non-free falling reference frame, Newton's laws would be
preserved. This means anything that can be effected by gravity also
has a gravitational effect on the first object. Since we all know that
light is effected by gravity, then analogously it ought to have a
gravitational field, so that Newton's laws are then correct in a
regular inertial reference frame.

However, if gravity is the bending of timespace, and is a natural
state of motion like inertia, then Newton's laws would only be
conserved in a state of free-fall. Newton's laws would be preserved in
a reference frame of free fall. Since light falls with a constant
acceleration, then it would not be required to exert a gravitational
force on anything in order to preserve Newton's laws, and therefore it
would not have a gravitational field of any sort.

Sorry, it doesn't work that simply. A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.

All we have to do, then, is determine whether light exerts a
gravitational force on things around it. Then we could determine
which of the models is correct and which is incorrect.

This experiment has already been done: Since a photon is deflected by
=TWICE= the angle one naively expects from Newton, by conservation of
momentum (which still holds in relativity), the Sun must have experienced
an _EQUAL AND OPPOSITE RECOIL DUE TO THE GRAVITATIONAL FORCE THE PHOTON
EXERTED ON IT_ --- and again, this recoil is =TWICE= as large as Newton
would have naively predicted. If this recoil did not occur, conservation
of both momentum and energy would be violated, and it would be possible
to build both reactionless drives and perpetual motion machines by
directing photons past masses --- and no one except crackpots take
either of those possibilities seriously !!!

Note, BTW, that the factor of =TWO= in the deflection calculation results
because of _SPACETIME CURVATURE_ by the mass of the Sun. Particles moving
at nearly the speed of light "feel" both the spatial and temporal components
of the curvature tensor, whereas "slowly" moving particles "feel" only the
temporal component. The deflection smoothly interpolates from "Newtonian"
to "double-Newtonian" as the "test particle" approaches lightspeed relative
to the gravitating source.

-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

**Old Man**

Gordon D. Pusch wrote in message
...
(Starblade Darksquall) writes:

[snip]

A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.

Wrong. In the center-of-momentum system, total energy gravitates,
nothing more nor less. Newtonian physics has nothing to say
about photons or light. In the proximity of massive bodies, photons
follow null-geodesics wherein, even in the limit of small mass and
large distance, the Newtonian gravitational potential is everywhere
"mulled-out". Unlike the Newtonian trajectories followed by massive
test particles, the deflection angle of light via space-time curvature
is independent of photon momentum. [Old Man]

-- Gordon D. Pusch

**Gordon D. Pusch**

"Old Man" writes:

Gordon D. Pusch wrote in message
...
(Starblade Darksquall) writes:

[snip]

A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.

Wrong.

I'm sorry, but it is YOU who are wrong. This is a =VERY= well-established
general relativistic result, first derived by Tolman, Ehrenfest, and
Podolsky in 1931 [Phys. Rev. v.37, p.602; see also Tolman "Relativity,
Thermodynamics and Cosmology" (Oxford 1934), and "The gravitational
interaction of light: from weak to strong fields," by V. Faraoni and
R.M. Dumse, http://arxiv.org/abs/gr-qc/9811052]. John Wheeler makes use
of this important result in his theory of "geons" --- objects composed
entirely of electromagnetic or gravitational waves that are quasi-bound
by their own self-gravitation.

In the center-of-momentum system, total energy gravitates, nothing more
nor less.

Sorry, wrong. I don't know where you are getting that from, but it isn't
from general relativity. I challenge you to find =ANY= literature citation
supporting your claim that "In the center-of-momentum system, total energy
gravitates, nothing more nor less." (Heck, the total energy isn't even
_localized_, whether in the center of momentum frame or any other frame!
It is the energies of the PHOTON WAVE_PACKETS that appear in the geodesic
equation, not the "center of momentum energy" of the pair !!!)

In the proximity of massive bodies, photons follow null-geodesics
wherein, even in the limit of small mass and large distance, the
Newtonian gravitational potential is everywhere "mulled-out".

Sorry, wrong. The Newtonian potential does indeed appear in the weak field
geodesic equation, and it is in no way "nulled out," even for null geodesics,
or else there would be NO DEFLECTION OF LIGHT AT ALL! In fact, the effective
"gravitational force" analog (the terms involving the Christoffel symbol
in the geodesic equation) is =DOUBLED= on photons because they feel
both spacelike and timelike constributions proportional to the "potential
gradient," which is why the gravitational deflection of photons is twice
what one naively expects.

Unlike the Newtonian trajectories followed by massive test particles,
the deflection angle of light via space-time curvature is independent of
photon momentum.

That's because a photon's momentum per unit energy (i.e., its velocity)
is independent of energy. The corresponding Newtonian analog is momentum
per unit MASS, not energy, which is again velocity --- and the deflection
of all Newtonian test-particles with the same initial velocity is likewise
independent of their momentum. You need to compare apples with apples, not
oranges!

-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

**Starblade Darksquall**

(Gordon D. Pusch) wrote in message ...
(Starblade Darksquall) writes:

There seems to be a very big split between those who beleive that
gravity is a force between two bodies mediated by the graviton 2-boson
and can be unified with the other forces, and those who beleive that
gravity is the bending of timespace, and that freefall can be taken to
be a proper reference frame.

There is no such "conflict," any more than there is a "conflict" caused by
a quantum-mechanical object exhibiting both "wave-like" and "particle-like"
properties. The "particle" picture is what is appropriate when one is
discussing quatum particles exchanging a small number of gravitons,
so that quantum effects are important; the "curved spacetime" picture
is appropriate in the classical limit when one has a huge enough number
of gravitons that one can approximate them as a classical "field."
A proper quantum theory of gravitation and spacetime will presumably
smoothly interpolate between these limits, just as quantum mechanics
smoothly interpolates between "particle-like" and "wave-like" behaviors
as the allowed resolution of the measurement apparatus is dialed from
"fine" spatial resolution (and necessarily coarse momentum resolution)
to fine momentum resolution (and necessarily course spatial resolution).
The "loop-space approach" to quantum fields being pursued by Lee Smolin
and others is perhaps a crude initial attempt at such a description.

But there is a test we can do which will distinguish between them.

Sorry, no.

If gravity is a force that can be mediated by graviton particles, then
in a non-free falling reference frame, Newton's laws would be
preserved. This means anything that can be effected by gravity also
has a gravitational effect on the first object. Since we all know that
light is effected by gravity, then analogously it ought to have a
gravitational field, so that Newton's laws are then correct in a
regular inertial reference frame.

However, if gravity is the bending of timespace, and is a natural
state of motion like inertia, then Newton's laws would only be
conserved in a state of free-fall. Newton's laws would be preserved in
a reference frame of free fall. Since light falls with a constant
acceleration, then it would not be required to exert a gravitational
force on anything in order to preserve Newton's laws, and therefore it
would not have a gravitational field of any sort.

Sorry, it doesn't work that simply. A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.

All we have to do, then, is determine whether light exerts a
gravitational force on things around it. Then we could determine
which of the models is correct and which is incorrect.

This experiment has already been done: Since a photon is deflected by
=TWICE= the angle one naively expects from Newton, by conservation of
momentum (which still holds in relativity), the Sun must have experienced
an _EQUAL AND OPPOSITE RECOIL DUE TO THE GRAVITATIONAL FORCE THE PHOTON
EXERTED ON IT_ --- and again, this recoil is =TWICE= as large as Newton
would have naively predicted. If this recoil did not occur, conservation
of both momentum and energy would be violated, and it would be possible
to build both reactionless drives and perpetual motion machines by
directing photons past masses --- and no one except crackpots take
either of those possibilities seriously !!!

Note, BTW, that the factor of =TWO= in the deflection calculation results
because of _SPACETIME CURVATURE_ by the mass of the Sun. Particles moving
at nearly the speed of light "feel" both the spatial and temporal components
of the curvature tensor, whereas "slowly" moving particles "feel" only the
temporal component. The deflection smoothly interpolates from "Newtonian"
to "double-Newtonian" as the "test particle" approaches lightspeed relative
to the gravitating source.

-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Alright, so now what? Does that mean if matter goes fast enough, it
has twice the gravitational attraction to other objects? That G
ultimately depends on speed? Then how do you reconcile this with the
equation for gravity? What is the REAL equation for gravity then?
Something like F = GM1(1+per1)M2(1+per2)/r^2sqrt(1-S/r) where per1 is
the percentage of matter that is in energy form in the first particle,
per2 is the percentage of matter that is in energy form in the second
particle, and S is the Schartzchild radius?

I mean, it would HAVE to be something weird like that!

Do you have the 100% RELATIVE TO THE TOP NOTCH SCIENTISTS equation for
gravity for every type of thing that they know? Or are you just
another crank, pretending that you know as much as them?

(...Starblade Riven Darksquall...)

**Steve Carlip**

In sci.physics Gordon D. Pusch wrote:
"Old Man" writes:

Gordon D. Pusch wrote in message
...
(Starblade Darksquall) writes:

[snip]

A beam of light only exerts
"no gravitational force" on _another beam of light traveling in
the same direction_. On a massive particle, it exerts =TWICE=
the "gravitational force" one would naively calculate by Newton,
just as it experiences =TWICE= the gravitational deflection that
one would naively calculate by Newton --- and two light beams
traveling in opposite directions each experience _FOUR TIMES_
the "gravitational force" and gravitational deflection one would
naively calculate using Newton.

Wrong.

I'm sorry, but it is YOU who are wrong. This is a =VERY= well-established
general relativistic result, first derived by Tolman, Ehrenfest, and
Podolsky in 1931 [Phys. Rev. v.37, p.602; see also Tolman "Relativity,
Thermodynamics and Cosmology" (Oxford 1934), and "The gravitational
interaction of light: from weak to strong fields," by V. Faraoni and
R.M. Dumse, http://arxiv.org/abs/gr-qc/9811052]. John Wheeler
makes use of this important result in his theory of "geons" --- objects
composed entirely of electromagnetic or gravitational waves that are
quasi-bound by their own self-gravitation.

This is a bit tricky -- you're both right (or both wrong), depending on
the details of the system you're talking about.

For pure disordered electromagnetic radiation, it is definitely true that
the effective gravitational mass is twice the energy. On the other hand,
if you look at ``light in a box of mirrors,'' and assume that the matter
that makes up the mirrors is electromagnetically bound, there is some
cancellation between the energy of the light and the binding energy
needed to keep the walls of the box from being pushed apart. If you
use the virial theorem, you'll find that the total electromagnetic
contribution to the mass is now just the energy, not twice the energy.
I discuss this issue in section IV of gr-qc/9909014.

Steve Carlip

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Gravitons VS General Relativity.	Gordon D. Pusch	Physics - General Discussion	9	July 13th 03 02:42 AM
Gravitons VS General Relativity.	Gregory L. Hansen	Physics - General Discussion	3	July 8th 03 11:25 AM
Gravitons VS General Relativity.	Old Man	Physics - General Discussion	6	July 8th 03 02:48 AM
Gravitons VS General Relativity.	Old Man	The Theory of Relativity	6	July 8th 03 02:48 AM
Gravitons VS General Relativity.	Bilge	Physics - General Discussion	0	July 7th 03 08:47 AM