As we have already know, a photon has a mass. So according to General
Relativity, any mass or energy manifests curved space around itself. The
question is that

Can an photon also manifest curved space around itself as it travels through
space? Are there any experiments done to see if two photon beams very
closely spaced able to combine into one due to the curved space created that
pulls each other towards and into each other?

If they do not, just like the centrifugal experiment that failed to detect
any time dilation, General Relativity is soon to be six feet under.

On a side note, the Gravity Probe B just launched seems to me to have
defeated its purpose by launching into a polar orbit. With the difference
in distance to the center of the earth of the poles and the equator, the
result would have been construed as frame dragging anyway. This, even very
simple, classical Newtonian law of gravity can even explain without frame
dragging predicted by General Relativity. Am I missing something?

Australopithecus Afarensis wrote:
As we have already know, a photon has a mass.

Photons have zero rest mass. That is why that travel at c.

Bob Kolker

Dear Australopithecus Afarensis:

"Australopithecus Afarensis" wrote in message
news:anqpc.37809$pJ1.24800@lakeread02...
As we have already know, a photon has a mass.

It has been experimentally determined to have a rest mass less than 10^-31
gm. It only has rest mass when paired with another counter-moving photon.

So according to General
Relativity, any mass or energy manifests curved space around itself. The
question is that

No. General Relativity does not equate gravitational mass and relativistic
mass.

Can an photon also manifest curved space around itself as it travels
through
space?

No.

Are there any experiments done to see if two photon beams very
closely spaced able to combine into one due to the curved space created
that
pulls each other towards and into each other?

Yes. And it doesn't occur. The probability of two photons colliding is
not a function of their energy, over a certain threshold. Therefore,
photons don't "gravitationally attract".

If they do not, just like the centrifugal experiment that failed to
detect
any time dilation, General Relativity is soon to be six feet under.

Your misunderstanding should soon die then. Relativisitic mass =/=
gravitational mass.

dragging predicted by General Relativity. Am I missing something?

Yes. An understanding. Try _Gravitation_ by Misner, Thorne, Wheeler.

David A. Smith

"Australopithecus Afarensis" wrote in message news:anqpc.37809$pJ1.24800@lakeread02...
As we have already know,

.... you doesn't have learn to formulating a sentence?

.... Am I missing something?

Nah, nothing you would be able to understand.

Dirk Vdm

Australopithecus Afarensis wrote:
As we have already know, a photon has a mass.

No, we don't know that at all. The current upper limit on the mass of a
photon is 2*10^-16 eV ( http://pdg.lbl.gov/2002/gxxx.pdf ). That's
incredibly small, being about 10^22 times smaller than the mass of the
lightest particle we know, the electron (leaving aside whether or not
neutrinos have nonzero masses).


So according to General
Relativity, any mass or energy manifests curved space around itself.

Hmmm. A light beam does indeed affect the geometry of spacetime. But not
because of any mass -- in GR the "source of gravitation" is the
energy-momentum tensor, not just mass.


The
question is that
Can an photon also manifest curved space around itself as it travels through
space?

Let me replace your "photon" with "light beam" to avoid quantum
complexities. Then certainly a light beam affects the geometry of spacetime.


Are there any experiments done to see if two photon beams very
closely spaced able to combine into one due to the curved space created that
pulls each other towards and into each other?

Because of the nature of the electromagnetic field, two parallel light
beams do not attract each other. But beams traveling in different
directions do attract. But the effect is so incredibly small that it is
hopeless to measure it experimentally, by many many orders of magnitude.


On a side note, the Gravity Probe B just launched seems to me to have
defeated its purpose by launching into a polar orbit. With the difference
in distance to the center of the earth of the poles and the equator, the
result would have been construed as frame dragging anyway. This, even very
simple, classical Newtonian law of gravity can even explain without frame
dragging predicted by General Relativity. Am I missing something?

You are indeed missing something: In Newtonian mechanics the rotation of
the earth is irrelevant, even including its oblateness, as long as one
assumes its density is a simple function of radius (i.e. neglecting
inhomogeneities like mountains and oceans). And if one includes those
tiny inhomogeneities, they have an effect which averages to zero over
long periods (i.e. much longer than the larger of 24 hours and the
period of the satellite). This is a simple consequence of the
time-independent structure of Poisson's equation -- the velocity of
matter is irrelevant in Newtonian gravitation, all that matters is its
position "right now".

They chose a polar orbit in the plane of the guide star to give the best
accuracy in detecting variations in the orbital plane. They then null
these out via a feedback mechanism that controls thrusters to keep the
orbital plane constant....


Tom Roberts

"Dirk Van de moortel" wrote in message ...
|
| "Australopithecus Afarensis" wrote in message news:anqpc.37809$pJ1.24800@lakeread02...
| As we have already know,
|
| ... you doesn't have learn to formulating a sentence?
|
| .... Am I missing something?
|
| Nah, nothing you would be able to understand.
|
| Dirk Vdm
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