Spyman gave me an idea about light

[swansont]

Swansont' date=' what is a perihelion shift exactly?

 

Regards[/quote']

 

It's a shift in the perihelion, obviously, aka precession of the orbit, which shouldn't happen in elliptical orbits around ideal masses, except that there are perturbations from other planets and the sun isn't perfectly spherical. But Mercury's orbit has a 43 arcsec/century advance that was unexplained by Newtonian gravity, with the other effects taken into account. But it is explained by GR, because orbits aren't perfect ellipses in GR.

 

But that's as far into detail as I can go. It's one of the prominent tests of GR, so there's a lot of detailed info around on this.

[J.C.MacSwell]

Swansont' date=' what is a perihelion shift exactly?

 

Regards[/quote']

 

The perhelion is the closest point an orbiting body gets to the orbited body in an elliptical orbit. Newtonian physics predicts that orientation (angle relative to "fixed"stars) would stay constant. GR predicts a consistent shift with each revolution.

[J.C.MacSwell]

Is there a perihelion shift that is not explained by GR?

 

None I am aware of. But I thought the gravitational vectors being directed at the "old" position of the bodies was the major part of the GR explanation.

[swansont]

None I am aware of. But I thought the gravitational vectors being directed at the "old" position of the bodies was the major part of the GR explanation.

 

I don't think so. In GR, space is curved, and the curving dictates the motion through space. That curve is constant in time for unaccelerated motion, so the gradient would be directed toward the star.

[J.C.MacSwell]

I don't think so. In GR, space is curved, and the curving dictates the motion through space. That curve is constant in time for unaccelerated motion, so the gradient would be directed toward the star.

 

And not the position of the star when it affected that curvature and gradient? In some frames what you are saying seems obvious or straight forward while in others it seems wrong. I have to give this some thought.

[Spyman]

I'm pretty sure that photons mediate the gravitational force now.

 

Does anyone disagree?

Since You used my name in the headline, I feel forced to clearify that I disagree with You on this one.

 

I give it some probability that maybe gravitation is mediated by some particle but it will not be by the same particle we call photons.

 

Photons have a real hard time getting through objects while gravity can't be shielded.

[swansont]

And not the position of the star when it affected that curvature and gradient? In some frames what you are saying seems obvious or straight forward while in others it seems wrong. I have to give this some thought.

 

As long as the star is not accelerating, the curvature does not vary in time. In the star's frame it's not moving. In an outside inertial frame, the curvature moves with the star.

[J.C.MacSwell]

As long as the star is not accelerating, the curvature does not vary in time. In the star's frame it's not moving[/b']. In an outside inertial frame, the curvature moves with the star.

 

The part I bolded seems right, but that would remain the same (no different) from the vector directed at the "old" position (since they are the same).

 

Just trying to gain incite , I know I haven't refuted anything you've said.

 

Now the unbolded part: It's hard to picture how that would work although as long as the star is affected only by gravity then this seems plausible (the field could "anticipate" the future position of the star)

 

For the outside inertial frame/s:

 

So if our Sun was "blindsided" by a high speed collision with a massive object

that changed it's position the gravitational vector (sun component) for our Earth would be directed at an imaginary path the Sun would have taken if not for the collision for the next 8 minutes?

[swansont]

Now the unbolded part: It's hard to picture how that would work although as long as the star is affected only by gravity then this seems plausible (the field could "anticipate" the future position of the star)

 

For the outside inertial frame/s:

 

So if our Sun was "blindsided" by a high speed collision with a massive object

that changed it's position the gravitational vector (sun component) for our Earth would be directed at an imaginary path the Sun would have taken if not for the collision for the next 8 minutes?

 

Yes. If our sun were to spontaneously accelerate, we wouldn't know about ti for 8 minutes (you have to ignore the effect of whatever caused the sun to accelerate, and perhaps a few other laws of physics, which limits the usefulness if scenarios like this)

 

By whatever means, the sun "communicates" its presence to space at the speed of light, and causes the curvature. Think of the curvature at some point as a rod extending out into space - that rod moves with the sun according to any outside observer, so the curvature is fixed at that point, relative to the sun. The curvature is there when the earth passes that point, and stays there afterwards. If the sun were to disappear, or to accellerate, the information about that (the disturbance in the curvature) will travel at c.

[swansont]

I give it some probability that maybe gravitation is mediated by some particle but it will not be by the same particle we call photons.

 

Photons have a real hard time getting through objects while gravity can't be shielded.

 

This is an excellent point.

 

There are trivial ways of excluding electric and magnetic fields from regions, and thius the forces caused by them, but gravity is unaffected. They can't be mediated by the same exchange particle.

[J.C.MacSwell]

Yes. If our sun were to spontaneously accelerate' date=' we wouldn't know about ti for 8 minutes (you have to ignore the effect of whatever caused the sun to accelerate, and perhaps a few other laws of physics, which limits the usefulness if scenarios like this)

 

By whatever means, the sun "communicates" its presence to space at the speed of light, and causes the curvature. Think of the curvature at some point as a rod extending out into space - that rod moves with the sun according to any outside observer, so the curvature is fixed at that point, relative to the sun. The curvature is there when the earth passes that point, and stays there afterwards. If the sun were to disappear, or to accellerate, the information about that (the disturbance in the curvature) will travel at c.[/quote']

 

So a body in motion in a given inertial frame throws "curveballs" to mediate or communicate the gravitational force (cause the curvature)? They are only straight in the rest frame of the body?

 

In your analogy your rod is always straight, but the path of the components, travelling along the rod at c, is itself curved in all inertial frames except the rest frame?

 

Edit: I hope I'm not causing confusion with respect to the 2 curvatures, the curvature over time of the vector path and the space curvature it produces.

[swansont]

So a body in motion in a given inertial frame throws "curveballs" to mediate or communicate the gravitational force (cause the curvature)? They are only straight in the rest frame of the body?

 

In your analogy your rod is always straight' date=' but the path of the components, travelling along the rod at c, is itself curved in all inertial frames except the rest frame?

 

Edit: I hope I'm not causing confusion with respect to the 2 curvatures, the curvature over time of the vector path and the space curvature it produces.[/quote']

 

The curvature of the rod is immaterial to the concept. GR has been summed up as "mass tells space how to curve, and the curvature tells bodies how to move" or something like that. So, the mass is always telling the space around it how to curve, and that happens at c. Any other body that passes by will experience this curvature.

[J.C.MacSwell]

The curvature of the rod is immaterial to the concept. GR has been summed up as "mass tells space how to curve, and the curvature tells bodies how to move" or something like that. So, the mass is always telling the space around it how to curve, and that happens at c. Any other body that passes by will experience this curvature.

 

What I meant was that the signal, traveling along at c, must change it's direction constantly for the vector to "follow" the star/sun if it is in motion in any particular inertial frame. Does that make sense?

[Johnny5]

It's a shift in the perihelion' date=' obviously, aka precession of the orbit, which shouldn't happen in elliptical orbits around ideal masses, except that there are perturbations from other planets and the sun isn't perfectly spherical. But Mercury's orbit has a 43 arcsec/century advance that was unexplained by Newtonian gravity, with the other effects taken into account. But it is explained by GR, because orbits aren't perfect ellipses in GR.

 

But that's as far into detail as I can go. It's one of the prominent tests of GR, so there's a lot of detailed info around on this.

 

Thanks so much for that link.

 

5600 seconds of arc per century.

 

What frame is that in?

 

One in which the center of mass of the solar system is at rest, or one in which the center of the sun is at rest?

[J.C.MacSwell]

Thanks so much for that link.

 

5600 seconds of arc per century.

 

What frame is that in?

 

One in which the center of mass of the solar system is at rest' date=' or one in which the center of the sun is at rest?[/quote']

 

It's a rotation, so would it make any difference?

[swansont]

What I meant was that the signal, traveling along at c, must change it's direction constantly for the vector to "follow" the star/sun if it is in motion in any particular inertial frame. Does that make sense?

 

The sun is at rest in its own frame, so that's not a problem. If it's moving at a constant v, the waves continue to emanate outward at c, telling space to warp. You can view the mass + the curvature as one object because in any inertial frame it's in steady-state.

[Crusty_Ass]

The light we see points toward where the sun was, 8 minutes ago, i.e. there is aberration. The gravitational vector points to where the sun is now. (This fact is often mistaken to imply that gravity is instantaneous.)

 

LOL...gravity IS faster than c. If gravity would travel at c then the gravitational vector would be identical to the vector of all other items travelling from the Sun to Earth at velocity c, i.e. the light. It isn't.

M-theory speculates....

Well I don't really think adding more dimensions is going to do the trick. More research is required for Planck scale cosmology and Quantum Physics. That's where the answers are.

If gravity is mediated by photons, then why is it so compratively weak to the other forces?

Not only that, if gravity is mediated by photons, how come it's bound by the mass of matter only and not influenced by other specifics like electric or magnetic charge, spin etc? Unreconcilable.

 

We are going to end up always using wave superposition to describe the phenomenon, I just know it.

Well there's really little evidence for gravity in this way. Gravity doesn't cancel itself out, unlike photons.

However, there is antigravity research that combines both electrical and magnetic fields to counter gravity. But these are based on fundamentally different theories.

 

Originally Posted by swansont

It's a shift in the perihelion, obviously, aka precession of the orbit, which shouldn't happen in elliptical orbits around ideal masses, except that there are perturbations from other planets and the sun isn't perfectly spherical. But Mercury's orbit has a 43 arcsec/century advance that was unexplained by Newtonian gravity, with the other effects taken into account. But it is explained by GR, because orbits aren't perfect ellipses in GR.

Ah... more on Mercury.

 

MORE ON MERCURY --

 

Now for a closer look at the Mercury perihelion matter: It is reasonably well known that as Mercury circles the Sun on an elliptical path, the axis of the ellipse rotates in space very slowly, so the path is slightly different each orbit. When all known causes have been allowed for, there still remains a progression of the ellipse of about 43 seconds of arc per century. The cause of this movement has not been determined completely, and Einstein claimed that his theory solved this problem "AGAINST WHICH CLASSICAL MECHANICS IS POWERLESS."

 

Poor gives a long explanation of the problems involved in predicting the position of planets, since they are affected by each other in a phenomenally complex way. Calculations were extensive even when certain assumptions were made, the records of the computations then occupying several volumes. These assumptions include such aspects as the Sun and planets being perfect spheres, and all meteoroids and asteroids are ignored.

 

Einstein quotes his figure of 43", claiming that "IT DOES NOT DIFFER SENSIBLY" from the observed figures of Leverrier (1859) and Newcombe (1882). But Newcombe's final result (1895) was 41.6". The average of Leverrier (38") and Newcombe is 8% different from Einstein's. Furthermore, if a calculated value for the oblateness of the Sun is allowed for, the difference becomes 16%. Thus Einstein's calculated value does not satisfactorily agree with the observed value.

 

Einstein quotes only the perihelion of Mercury as completely justifying his theory, and dismisses all of the several other anomalies as being "UNVERIFIED" or too small to be determined with any certainty. This is flagrantly wrong. When Newcombe was checking Leverrier's calculations, he noted several other anomalies in planetary orbits which he could not account for. Poor gives a table of the measured discordancies compared to those predicted by Einstein's formula, which only affects the perihelion of the orbits:

 

TABLE

 

Comparison of the various measured orbital Discordancies with the figures predicted by Einstein's relativity (Poor 1922): (in seconds of arc per century)

PLANET           DISCORDANCE        EINSTEIN   DIFFERENCE MEASURED
Perihelia --
Mercury           + 41.6            + 42.9           - 1.3
Venus             - 7.3             + 8.6            - 15.9
Earth             + 5.9             + 3.8            + 2.1
Mars              + 8.1             + 1.3            + 6.8

Nodes --
Mercury           + 5.1               0              + 5.1
Venus             + 10.2              0              + 10.2

Eccentricity --
Mercury           - 0.88              0              - 0.88

When all discordancies of the planets are considered, it can be seen that except for very closely approximating the perihelion of Mercury, Relativity fails completely to accord with the others listed in the table.

 

______

 

Einstein had the gall to dismiss these differences as insignificant, yet they were obviously even then *WELL WITHIN* the range of accurately measurable astronomical observations and calculations. Einstein quite clearly appears to have selected the largest of the discordancies and then proposed that his formula fully explained it, claiming this ONE VALUE as proof of his theory. No matter how lax the foundations of science may then or now have become, there is obviously no scientific ground upon which one could be permitted to select one material result of a research and to dismiss other unmatching ones as unacceptable, or why one figure is to be considered absolutely correct and all varying figures essentially wrong.

[swansont]

LOL...gravity IS faster than c. If gravity would travel at c then the gravitational vector would be identical to the vector of all other items travelling from the Sun to Earth at velocity c' date=' i.e. the light. It isn't.

[/quote']

 

You have assumed gravity behaves just like light. It doesn't, so your conclusion isn't valid.

[swansont]

Well there's really little evidence for gravity in this way. Gravity doesn't cancel itself out' date=' unlike photons.

However, there is antigravity research that combines both electrical and magnetic fields to counter gravity. But these are based on fundamentally different theories.

[/quote']

 

Countering gravity and antigravity are not the same thing.

[bascule]

Everything else you said was nonsense

 

Umm, you're the one claiming photons mediate the gravitational force, which is itself total nonsense.

 

Quantum models predict the graviton is a massless spin 2 particle. String theory predicts that all particles in the standard model are open and thus bound to a D-p-brane, whereas the graviton is not, it's a closed string that manifests itself as a massless spin 2 particle.

 

And somehow you picked up on the significance of my question...

 

If gravity is mediated by photons, then why is it so compratively weak to the other forces?

 

then completely ignored it. The string theory explanation is simple: the other three forces are comprised of open strings bound to a D-p-brane, and so their spread is contained, whereas gravitons are closed and are thus diluted across all dimensions. What is your explanation given the ridiculous assertion that the photon mediates gravity? Your assertion seems to be based on little more than that the propagation of gravity is bound by c, when in reality the speed of all massless particles is bound by c...

[BlackHole]

String theory/M-theory is highly speculative. We have no evidence for extra-dimensions and D-branes. In fact we don't have evidence for the physical existence of space & time (see EPR paradox).

 

I am convinced (and always were) that everything must draw upon a energy/power source. I think gravity is a quantum-dynamical effect. If we examine carefully we'll notice that electrodynamics, quantum mechanics, statistical thermodynamics, condensed matter physics, nuclear physics, plasma physics etc. do not agree with general relativity about the physical existence of space-time.

 

The fact that gravitational singularities and non-baryonic dark matter have never been directly detected is not good a sign for the BBT. Another problem is that the BBT predicts a new class of stars, in which lithium should be abundant. Up to now we don't see it.

[swansont]

String theory/M-theory is highly speculative. We have no evidence for extra-dimensions and D-branes. In fact we don't have evidence for the physical existence of space & time (see EPR paradox).

 

...

 

The fact that gravitational singularities and non-baryonic dark matter have never been directly detected is not good a sign for the BBT. Another problem is that the BBT predicts a new class of stars' date=' in which lithium should be abundant. Up to now we don't see it.[/quote']

 

I don't know what you think the EPR paradox has to do with this, but you link has a glaring error in it. Determination of momentum or position is not the same thing as simultaneous determination of both position and momentum.

 

Also, I thought that BB nucleosynthesis gave a pretty good prediction of Lithium abundance. Where does BBT predict Lithium stars?

[bascule]

String theory/M-theory is highly speculative. We have no evidence for extra-dimensions and D-branes.

 

Can you point to a non-speculative theory of quantum gravity?

 

We have experimentally measured the exceptional weakness of gravity relative to the electromagnetic force, and this is something any theory of quantum gravity must be able to explain. M-theory certainly explains this with the dilution of gravity across multiple D-p-branes. So far I'm not seeing any kind of explanation in this photonic hypothesis...

[BlackHole]

I don't know what you think the EPR paradox has to do with this, but you link has a glaring error in it. Determination of momentum or position is not the same thing as simultaneous determination of both position and momentum.

 

Also, I thought that BB nucleosynthesis gave a pretty good prediction of Lithium abundance. Where does BBT predict Lithium stars?

 

Two entangled photons can be millions of miles apart and yet, if the polarity of one photon flips, the other will flip simultaneously. To a lot of classical physicists such as Einstein, the existence of nonlocal phenomena would mean that the two photons are communicating at superluminal speeds which is a no-no. Einstein called it "spooky action at a distance." Many have refused to accept the completeness and even the correctness of QM for this reason. But the superluminal objection is flawed in my opinion, because it assumes the physical existence of space.

 

There is no space and therefore it is easy to see that there is no superluminal or any sort of communication taking place between the entangled photons. Particles do not exist in space, they just exist. There is no spooky action at a distance because there is no distance between particles. This is not the same as saying that the distance is zero; distance simply does not exist: it is abstract. More precisely, it is the abstract vector difference between two positional properties.

 

The Big Bang predicts that no elements heavier than lithium would have been created, yet elements heavier than lithium are observed in quasars, which presumably are some of the oldest galaxies in the universe. The third problem is since the big bang nucleosynthesis produces no elements heavier than lithium, then we ought to see some long lived remnant stars which have no heavy elements in them. Up to now we don't see them.

 

Can you point to a non-speculative theory of quantum

gravity?

 

We have experimentally measured the exceptional weakness of gravity relative to the electromagnetic force' date=' and this is something any theory of quantum gravity must be able to explain. M-theory certainly explains this with the dilution of gravity across multiple D-p-branes. So far I'm not seeing any kind of explanation in this photonic hypothesis...[/quote']

 

I'm not sure that quantum mechanics and general relativity are compatible with each other. Classical general relativity demonstrates than gravity is not a force and quantum mechanics (non-relativistic) demonstrates that space/distance does not exist physically.

 

I say that gravity and magnetism could be related phenomenas.

[swansont]

Two entangled photons can be millions of miles apart and yet, if the polarity of one photon flips, the other will flip simultaneously.

 

No, that's not what entanglement says. It says if you measure the polarization of one, you know the polarization of the other. Once you make that measurement, they are no longer entangled. You don't know if you've flipped the polarization since you don't know what it is. And you can't know unless you measure it, which destroys the entanglement.

 

 

To a lot of classical physicists such as Einstein' date=' the existence of nonlocal phenomena would mean that the two photons are communicating at superluminal speeds which is a no-no. Einstein called it "spooky action at a distance." Many have refused to accept the completeness and even the correctness of QM for this reason. But the superluminal objection is flawed in my opinion, because it assumes the physical existence of space.

 

There is no space and therefore it is easy to see that there is no superluminal or any sort of communication taking place between the entangled photons. Particles do not exist in space, they just exist. There is no spooky action at a distance because there is no distance between particles. This is not the same as saying that the distance is zero; distance simply does not exist: it is abstract. More precisely, it is the abstract vector difference between two positional properties. [/quote']

 

That Einstein didn't like it is immaterial. Entanglement doesn't violate causality.

 

...

 

I'm not sure that quantum mechanics and general relativity are compatible with each other. Classical general relativity demonstrates than gravity is not a force and quantum mechanics demonstrates that space/distance do not exist physically.

 

I say that gravity and magnetism could be related phenomenas.

 

That QM and GR are incompatible rates right up there with a "Sun rises in the East" headline. If gravity is related to magnetism it is necessarily related to electrostatics, too.