Alternative theories being tested by Gravity probe B

[Glen Deen]

CMB Doppler velocity and solar orbit velocity.

But the velocity of the Earth realtive to the CMB Surface of Last Scattering is OOM 10^-3c, the orbital velocity of the Solar System around a binary companion with SMA ~ 10³ AU would be OOM ~ 3 x 10^-6c. So the scenario you suggest cannot explain the CMB dipole. The velocity of the sun around its companion would be ~ three hundred times too small.

Garth

No. My scenario does not explain the CMB dipole. The CMB dipole drift, if it does exist, explains my scenario.

You say the velocity of the Earth, but I'm pretty sure COBE and WMAP give the absolute velocity of the Sun to eliminate the small annual variations. I assume from published information that this is 371 km/s. I claim that we can assign this constant velocity to the binary system barycenter, which becomes an inertial frame. The velocity of the Sun relative to the barycenter is on the order of 1 km/s as you say. So we have a little velocity vector rotating about the arrowhead of a big velocity vector. What matters is in which direction the little vector is pointing as a function of time.

Since the barycenter defines an inertial frame, it doesn't matter whether that frame has absolute motion or not, as long as it is a constant velocity. Right? When we are interested in rotation, we can ignore any constant translation in a fixed direction. It is the rotation that makes the stars appear to precess.

Let's look at a numeric example.

Epoch___ Vsun kms Longitude Latitude
1991.882 371.0000 171.73882 -11.1008
2002.085 371.0000 171.59626 -11.1008
Vec diff 0.905797 81.667532 +0.00000

The vector difference is the Sun's velocity relative to the binary barycenter. As you see it is on the order of 1 km/s. But to get the absolute rotation rate of the Sun I take the difference in longitude dLong = 171.59626 - 171.73882 = -0.14255 degrees, multiply it by 3600 to get arc seconds, and divide it by the time interval = 10.203 years.

Drift rate in longitude = -0.14255*3600/10.203 = -50.30 arc sec/year

Does that make sense now?

-Glen

 

[Garth]

No. My scenario does not explain the CMB dipole. The CMB dipole drift, if it does exist, explains my scenario.

Okay, but your statement confused me:

But since the barycenter is an inertial frame, we expect the dipole apex direction to match that of the Sun's orbital velocity vector.

The dipole blue apex is the direction of the Sun/Earth motion relative to the Surface of Last Scattering at a velocity ~ 10^-3c and can be rendered through vector addition as a motion of the Galaxy COM relative to the SLS.

Garth

 

[Glen Deen]

The dipole blue apex is the direction of the Sun/Earth motion relative to the Surface of Last Scattering at a velocity ~ 10^-3c and can be rendered through vector addition as a motion of the Galaxy COM relative to the SLS.

Garth

So what? Did you understand my numerical example?
-Glen

 

[Garth]

So what? Did you understand my numerical example?
-Glen

I understand your scenario would produce a drift rate as described. However, do you understand the origin of the CMB dipole due to the Sun's motion of ~10^-3c relative to the Surface of Last Scattering?

This thread is not the place for a discussion on novel theories, only those published GP-B predictions of alternative theories that can be compared with those of GR.

Please continue your discussion in the IR Forum

Garth

 

[cesiumfrog]

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

Could we get error bars on all of these predictions?

This is a great idea for a thread, but obviously (at least, I presume it is obvious to everyone here, yes?) the whole exercise is pointless without the uncertainty limits. This goes double for NGT (which I think should be removed completely until its difference from GR is quantified).

 

[Garth]

Could we get error bars on all of these predictions?

This is a great idea for a thread, but obviously (at least, I presume it is obvious to everyone here, yes?) the whole exercise is pointless without the uncertainty limits. This goes double for NGT (which I think should be removed completely until its difference from GR is quantified).

Thank you cesiumfrog that is a good point. In fact most of these predictions are precise predictions using physical constants such as G,M_Earth, c, and the satellite's orbital elements. The major source of error are the orbital elements, which have been determined so the predictions are accurate to 0.1 milliarcseconds each.

What is not so accurate are the systematic drifts caused by other effects such as the polhode motion due to the gyroscope spheres not being exactly spherical. It is the determination of these other effects to that accuracy that is going to take until the end of 2007 to determine. There will be a poster "Gravity Probe B Experiment Error" by Barry Muhlfelder, G. Mac Keiser, John Turneaure at the April APS meeting. We will know more then.

As far as NGT is concerned GP-B will not be a falsifiable test, but at least it provides "wriggle room" if the geodetic precession is only a little different from the GR expectation.

Garth

 

[Glen Deen]

I understand your scenario would produce a drift rate as described. However, do you understand the origin of the CMB dipole due to the Sun's motion of ~10^-3c relative to the Surface of Last Scattering?

This thread is not the place for a discussion on novel theories, only those published GP-B predictions of alternative theories that can be compared with those of GR.

Please continue your discussion in the IR Forum

Garth

On February 16 you said:

Well Walter, as I said, I find it hard to believe that:
1. The Moon does not induce the observed 26,000 yr period precession on the Earth as all the models of the geoid predict and,
2. There is an unobserved ~ stellar mass object, which is a binary companion to the Sun with a SMA of ~ 877AU that is responsible for the said observed precession.

Number 2 is a novel theory, and it is the one I am referring to.

I'm saying that if number 2 is true, then the Sun's change in direction in its absolute velocity vector over time due to its orbit about the binary barycenter should be seen as a change in the direction of the apex of the CMB dipole. What I showed was that such a change can be made equal to the 50.3 arcsec/year general longitude precession rate by adjusting the galactic coordinates of the COBE and the WMAP dipole apexes, keeping them within the stated error bars. Thus it is possible to decide on the truth of number 2 using COBE and WMAP as well as GP-B.

-Glen

 

[Garth]

On February 16 you said:

Number 2 is a novel theory, and it is the one I am referring to.

I'm saying that if number 2 is true, then the Sun's change in direction in its absolute velocity vector over time due to its orbit about the binary barycenter should be seen as a change in the direction of the apex of the CMB dipole. What I showed was that such a change can be made equal to the 50.3 arcsec/year general longitude precession rate by adjusting the galactic coordinates of the COBE and the WMAP dipole apexes, keeping them within the stated error bars. Thus it is possible to decide on the truth of number 2 using COBE and WMAP as well as GP-B.

-Glen

And if true the 50.3 arcsec/yr precession will also show up in all other space telescopes. Does it?

Garth

 

[Garth]

I understand your scenario would produce a drift rate as described...

Garth

Actually, Glen Deen, and Walter, on further reflection, I do not understand how your scenario would produce such a drift rate in the precession of the equinoxes.

The Earth's polar axis would point in a constant direction relative to the distant stars if there were no lunar gravitational attraction to the Earth's equatorial bulge, no matter if the solar system were in orbit about a solar companion.

The gravitational perturbation on the Earth's orbit would produce a slight precession on the ecliptic, but nowhere near the value otherwise attributed to the lunar action on the geoid.

Your scenario does not make sense. Please keep it out of this serious discussion of the outcome of the GP-B experiment.

Garth

 

[Glen Deen]

And if true the 50.3 arcsec/yr precession will also show up in all other space telescopes. Does it?

Garth

That's a very good question! Space telescopes do not have setting circles as Earth telescopes do. All space astrometry is relative to known star positions. Precession is a absolute drift in the ecliptic longitude of all stars, and it can't be detected by any space telescope unless they use precision gyroscopes as absolute references as GP-B does, and they concentrate on the position of a single star over long periods of time. Most space telescopes do not do that.

-Glen

 

[Glen Deen]

Actually, Glen Deen, and Walter, on further reflection, I do not understand how your scenario would produce such a drift rate in the precession of the equinoxes.

It doesn't. According to our binary orbit scenario, the equinoxes are fixed in inertial space thanks to the law of conservation of angular momentum. The Sun's orbit makes the stars precess relative to the fixed equinoxes. In 26,000 years the stars return to their original position. This is analogous to the stars appearing to make a complete circuit over one year because of Earth's orbit.

The Earth's polar axis would point in a constant direction relative to the distant stars if there were no lunar gravitational attraction to the Earth's equatorial bulge, no matter if the solar system were in orbit about a solar companion.

I agree.

The gravitational perturbation on the Earth's orbit would produce a slight precession on the ecliptic, but nowhere near the value otherwise attributed to the lunar action on the geoid.

I agree.

Your scenario does not make sense. Please keep it out of this serious discussion of the outcome of the GP-B experiment.

Garth

I can accept that you don't agree with it. I refuse to accept that it doesn't make any sense. Can we take a poll of the others on this list to see if it makes sense to them?

-Glen

 

[Garth]

That's a very good question! Space telescopes do not have setting circles as Earth telescopes do. All space astrometry is relative to known star positions. Precession is a absolute drift in the ecliptic longitude of all stars, and it can't be detected by any space telescope unless they use precision gyroscopes as absolute references as GP-B does, and they concentrate on the position of a single star over long periods of time. Most space telescopes do not do that.

-Glen

This is nonsense: - "All space astrometry is relative to known star positions" - so is the alignment of the GP-B gyroscopes 'relative to known star positions'.

GP-B does not measure the ecliptic longitude.

The gyroscopes' axial directions are measured relative to the guide star. The guide star is being tracked by the VLBI and that tracking will detect the precession of the equinoxes if it measures the constantly updated RA and dec. of the star on the Earth based celestial sphere. But in fact they are tracking the proper motion of the IM Pegasi relative to a distant quasar, so they will not detect this precession at all.

The precession of the equinoxes is well known and attributed to the lunar and solar differential gravitational forces on the Earth's oblate spheroid.

There are nutations caused by the Sun's and Moon's changing relative positions.

In addition to this lunisolar precession, the other planets, mainly Jupiter, cause the whole ecliptic to rotate, this planetary precession shift is only 0.47 seconds of arc per year (more than a hundred times smaller than lunisolar precession). All this is well modeled, a binary solar companion would cause an further precession, which would be less than even this. Such a precession has not been observed, although that was what I had first thought you must been alluding to.

The gravitational action of a hypothetical binary solar companion would not affect the GP-B gyroscopes any more than they would the alignment of other space telescopes. It will not affect their axial direction relative to the distant quasar, which is the ultimate reference point. Therefore the question of such a hypothetical binary solar companion has no place in this thread.

Garth

 

[Garth]

I can accept that you don't agree with it. I refuse to accept that it doesn't make any sense. Can we take a poll of the others on this list to see if it makes sense to them?

-Glen

If you wish to discuss this unorthodox and unpublished theory you have to do so on the Independent Research Forum. Conduct your poll there, after fulfilling that Forum's guidelines.

Garth

 

[Glen Deen]

This is nonsense: - "All space astrometry is relative to known star positions"

I could be wrong about that. Can you give me a counter example?

- so is the alignment of the GP-B gyroscopes 'relative to known star positions'.

I never said that.

GP-B does not measure the ecliptic longitude of the ecliptic.

I never said it does.

The gyroscopes are measured relative to the guide star. The guide star is being tracked by the VLBI and that tracking will detect the precession of the equinoxes if it measures the constantly updated RA and dec. of the star on the Earth based celestial sphere.

No. Precession is not observed by the VLBI. Precession is always computed using standard formulas.

The VLBI would measure the apparent place RA, Dec of IM Pegasi at each time of observation. To reduce an apparent place to a mean place at a standard epoch and equinox, I believe they must make the following corrections in order.

1. The effect of annual parallax.
2. The effect of annual aberration.
3. The effect of nutation.
4. The effect of precession.
5. The proper motion of the star.

The idea is that the mean place of any star at a standard epoch and equinox should be constant over time. The first four corrections are computed, not observed, and they are functions of time and place. The time argument is the difference between the observation time and the standard epoch time. The observed proper motion would be whatever it took to move the place after the fourth correction to the known mean place at the standard epoch and equinox.

In fact they are tracking the proper motion of the IM Pegasi relative to a distant quasar, so they will not detect this precession at all.

As I said, precession is not observed; it is computed. Quasars, like all stars, precess relative to the equinox.

Quasars have no parallax or proper motion, so steps 1 and 5 can be eliminated in the place reduction. So quasars provide a powerful check on the successive corrections for annual aberration, nutation, and precession. Now if you believe you know the effects of annual aberration and nutation to a very high precision, then you can use VLBI observations of quasars to "observe" general precession, and you can compare it to the results you got from the standard formula.

The precession of the equinoxes is well known and attributed to the lunar and solar differential gravitational forces on the Earth's oblate spheroid.

Yes, and that is a problem for the binary Sun theory. "Lunisolar" precession may consist of two components: the Newtonian-d'Alembert gravitational torques on the spinning tilted oblate Earth from gravitational forces from the Sun and the Moon plus the Sun's binary orbit motion. In the worst case, I think the Newtonian torques could be eliminated if the oblate Earth were hollow with a uniform shell thickness. If GP-B is observing a too-large "proper motion", I'm suggesting that it is due to the Sun's motion in a binary orbit.

There are nutations caused by the Sun's and Moon's changing relative positions.

Yes.

In addition to this lunisolar precession, the other planets, mainly Jupiter, cause the whole ecliptic to rotate, this planetary precession shift is only 0.47 seconds of arc per year (more than a hundred times smaller than lunisolar precession).

Yes.

All this is well modeled,

But is lunisolar precession modeled from first principles taking into consideration Earth's radial density profile, or is it modeled to match quasar observations? If the latter, then it can be questioned.

a binary solar companion would cause an further precession, which would be less than even this.

Smaller than 0.47 arcsec/year? Not hardly. If you assume the Sun is in a circular orbit a rate of 0.47 arcsec/year would correspond to an orbit period of 2.8 million years. We usually imagine much shorter periods and corresponding greater precession rates. But we don't need to speculate. GP-B can tell us how much it is. In fact, GP-B can refute the binary Sun hypothesis simply by not finding any excess "proper motion".

Such a precession has not been observed, although that was what I had thought you must been alluding to.

We are speculating that GP-B has observed it. If that turns out to be true, then I imagine other space telescopes can also observe it using their less precise gyroscopes.

The gravitational action of a hypothetical binary solar companion would not affect the GP-B gyroscopes any more than they would the alignment of other space telescopes. It will not affect their axial direction relative to the distant quasar, which is the ultimate reference point. Therefore the question of such a hypothetical binary solar companion has no place in this thread.

Garth

We are not talking about gravitational forces of the companion on the Earth inducing something akin to planetary precession. We are talking about the Sun following a curved path in space in its binary orbit. Such a curved path would produce apparent precession of the stars relative to the equinox. Imagine you are sitting on a merry-go-round across from the companion. If the merry-go-round rotated counter-clockwise, the objects on the horizon (analogous to stars) appear to the observer on the merry-go-round to rotate clockwise. Its just like what the stars do over the course of a year as a result of the Earth's orbit around the Sun.

-Glen

 

[henryco]

This is the drift rate of the equinox relative to the fixed stars, so it is negative. The precession of the stars relative to the equinox is +50.3 arc sec per year.

-Glen

I thinck this analysis is very interesting. Probably this precession is also responsible for the anomalous WMAP quadrupole correlation with ecliptic and equinoxes directions (see http://www.citebase.org/abstract?id=oai%3AarXiv.org%3Aastro-ph%2F0608318 ) , so I'm quite surprised that you did not
mention it.

The predictions of a Dark Gravity theory I'm working on are in the Garth's list.
Though the theory keeps opened the possibility that there could be an additional small and anomalous preferred frame effect, a recent and closer reinspection convinced me that this is quite unlikely within this framework.

On the other hand, if i understand well, you and polestar are calling upon an unsubtracted extra proper motion effect of the sun about a neighbour star to explain both the equinoxe precession and the CMB precession and you expect this to be seen by GP-B.

I thinck it's intersting trying to find out a common explanation and i also would not be surprised to see such large effect arrising in GP-B data but within the DG theory I'm working on i would tend to propose another mechanism for it (i already proposed it sometime ago to explain the quadrupole anomalies).

In DG, i have a discontinuity of the gravitational field (by the way responsible for the Pioneer anomaly) and this phenomenon takes ~26000 years to achieve its periodic path scanning the solar system.
These 26000 years show up as the result of dividing the sun potential surface by the present value of the Hubble parameter. So the agreement is at the 15% level (due to the present error on H0 direct estimation).

How could this be related to the equinoxe precession? I have no definitive answer but ...
actually, this discontinuity acts as an unexpected foreground able to deviate or reflect light from any background object (CMB, star) since it is like a border between two areas with different indices.
Because the discontinuity is moving, all background objects should apparently move with it along a 26000 years periodic path...
But i don't see for the time being how i could get your 50''/year

F Henry-Couannier

 

[Garth]

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.

The gyroscopes' axial directions are compared to IM Pegasi. IM Pegasi, a radio binary star, has been being tracked by the VLBI relative to distant quasar 3C454.3. and sometimes two others. When the VLBI data is convoluted with the satellite data the motion of the gyroscopes will be measured relative to the 'fixed stars'.

There will be subtle effects of such a supposed binary companion of the Sun, such as a tiny precession of the ecliptic on top of that caused by the other planets as I described above, but nowhere near the 50.3"/yr precession of the equinoxes, but even so this will not affect the GP-B data, only the astrometric data of a telescope fixed to the wobbling Earth.

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth

 

[Glen Deen]

How could this be related to the equinoxe precession? I have no definitive answer but ...
actually, this discontinuity acts as an unexpected foreground able to deviate or reflect light from any background object (CMB, star) since it is like a border between two areas with different indices.
Because the discontinuity is moving, all background objects should apparently move with it along a 26000 years periodic path...
But i don't see for the time being how i could get your 50''/year

Henryco, I bring your last paragraph up to the top because I wish to discuss it first. I know nothing about your Dark Gravity theory (maybe I should learn), but I think I recognize your discontinuity. You mean different indexes of refraction, right? I call such a structure a cosmic lens because the speed of light is slower inside than outside. I imagine that every gravitating body is at the center of its own spherical lens. The effect of Earth's lens is called atmospheric refraction. The effect of the Sun's lens is called annual parallax. Since light rays to distant stars are not straight but are refracted at the lens surface, all stars may be much closer than we calculate from geometric parallax. I'm sure the Earth's atmosphere does refract starlight to some extent, but the speculation is that Earth's cosmic lens may contribute some part of the refraction. Every galaxy, every globular cluster and every open cluster ought to have its own cosmic lens as well.

Let's say for the sake of argument that the Sun's hypothetical companion is a white dwarf star. We easily observe Sirius B, so we should much more easily observe this companion. We don't because it would need to have a proper motion that is the negative of the lunisolar precession rate, and such a large proper motion could not have escaped notice. But if this companion were outside the Sun's cosmic lens and inside its focal length, I claim that its rays cannot produce an image in any Earth camera focused at infinity.

I thinck this analysis is very interesting. Probably this precession is also responsible for the anomalous WMAP quadrupole correlation with ecliptic and equinoxes directions (see http://www.citebase.org/abstract?id=oai%3AarXiv.org%3Aastro-ph%2F0608318 ) , so I'm quite surprised that you did not mention it.

In retrospect I should have. Thanks for mentioning it for me.

The predictions of a Dark Gravity theory I'm working on are in the Garth's list.

Please tell me how to get there.

Though the theory keeps opened the possibility that there could be an additional small and anomalous preferred frame effect, a recent and closer reinspection convinced me that this is quite unlikely within this framework.

On the other hand, if i understand well, you and polestar are calling upon an unsubtracted extra proper motion effect of the sun about a neighbour star to explain both the equinoxe precession and the CMB precession and you expect this to be seen by GP-B.

I don't know what Walter's (polestar's) position is on my speculations regarding a predicted hypothetical secular drift in the CMB dipole apex direction. But we both do expect GP-B to observe a substantial anomalous proper motion in IM Pegasi that should be some fraction up to 100% of the vector that is the exact negative of the lunisolar precession for that place in the sky. In the worst case (100%) the Sun's binary orbit accounts for all of the lunisolar precession, leaving nothing for the Newtonian gravity forces from the Moon and the Sun on the spinning inclined oblate Earth. That extreme may be ruled out since it would seem to require a hollow Earth with a uniform shell thickness.

I thinck it's intersting trying to find out a common explanation and i also would not be surprised to see such large effect arrising in GP-B data but within the DG theory I'm working on i would tend to propose another mechanism for it (i already proposed it sometime ago to explain the quadrupole anomalies).

In DG, i have a discontinuity of the gravitational field (by the way responsible for the Pioneer anomaly) and this phenomenon takes ~26000 years to achieve its periodic path scanning the solar system.
These 26000 years show up as the result of dividing the sun potential surface by the present value of the Hubble parameter. So the agreement is at the 15% level (due to the present error on H0 direct estimation).

F Henry-Couannier

This is interesting. I would like to know more about it.

-Glen

 

[Glen Deen]

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.

That is true according to Newtonian mechanics. I have concluded that if the predicted effect occurs, it will be the result of GRT frame dragging. This probably cannot occur to the necessary degree unless the perihelion of the companion is quite near to the Sun, perhaps even inside the solar system. But if it is true, the GP-B gyroscopes would align themselves with the local inertial frame, which my theory supposes rotates with respect to the fixed stars because of frame dragging.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.

Yes, but maybe it's free-fall in a rotating "inertial" frame.

The gyroscopes' axial directions are compared to IM Pegasi. IM Pegasi, a radio binary star, has been being tracked by the VLBI relative to distant quasar 3C454.3. and sometimes two others. When the VLBI data is convoluted with the satellite data the motion of the gyroscopes will be measured relative to the 'fixed stars'.

I agree. If you are right, there won't be any such motion. If frame dragging is occurring, then I think they will see the gyroscopes move relative to the fixed stars.

There will be subtle effects of such a supposed binary companion of the Sun, such as a tiny precession of the ecliptic on top of that caused by the other planets as I described above, but nowhere near the 50.3"/yr precession of the equinoxes, but even so this will not affect the GP-B data, only the astrometric data of a telescope fixed to the wobbling Earth.

The period is too long to see any tiny planetary-like precession from the companion. I think they will see either a substantial fraction of the 50.3"/yr precession or nothing.

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth

I suggest that it may not produce all of that precession rate. It really depends on what the GP-B people observe. If they see proper motion in IM Pegasi relative to their gyroscopes (due to frame dragging) that is a substantial fraction of 50.3"/yr, then the Moon and Sun must be causing only the remainder.

Since quasars have no annual parallax or proper motion, they can be used to observe general precession because the annual aberration and the nutation can be computed from first principles with no need for observations. If the general precession formulas have been adjusted to minimize the least squared error in the observed precession of a large number of quasars, that is an empirical data fit that can be challenged.

I doubt that the precession formulas were derived from first principles. What I see in Danby's Chapter 13 (Fundamentals of Celestial Mechanics) is that they use the moments of inertia of the spheroidal Earth about its principal axes. How do they know these moments of inertia? I read in Fowler's The Solid Earth -- An Introduction to Global Geophysics on page 110:

Although such a self-compression density model for the Earth satisfies the seismic velocity data from which it was derived, it does not satisfy data on the rotation of the earth. In particular, the Earth's moment of inertia, which is sensitive to the distribution of mass in the earth, is significantly greater than the moment of inertia for the self-compression model. There must be more mass in the mantle than the self-compression model allows.

So, how do they know the Earth's moment of inertia from its rotation? I wonder if people observe the precession from quasars and calculate what the moment of inertia must be from the equations established by Newton and d'Alembert. The geophysicists are saying that moment of inertia is too high according to their radial density profile calculations. That could mean that the lunisolar precession is too high.

-Glen

 

[Garth]

Returning the thread back on track, so far we have the following alternative theories that have been published in refereed journals, or on the Physics ArXiv, that make specific and falsifiable alternative predictions of the outcome of the Gravity Probe B experiment. Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (SCC),
Moffat's Nonsymmetric Gravitational Theory (NGT),
Hai-Long Zhao's Mass Variance SR Theory (MVSR),
Stanley Robertson's Newtonian Gravity Theory (NG),
Junhao & Xiang's Flat Space-Time Theory (FST).
R. L. Collin's Mass-Metric Relativity (MMR) and
F. Henry-Couannier's Dark Gravity Theory (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

And from The stars of Pegasus from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM PegasiRA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

Of course, these alternative theories have to pass all the other tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment. Some of them might already have failed those tests.Garth

 

[henryco]

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.
Garth

You are right except if , as Glen says now, there is an important violation of the Equivalence Principle, the local inertial frames orientations being "mainly" determined with respect to a rotating local bubble...

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth

I know nothing about this computation...but most probably this more conventional understanding is correct. Then, either my 26000 years are a pure coincidence...or more interestingly, the relative positions of sun Earth and moon were stabilised under the influence of a periodic 26000 years discontinuity path in order to get the matching with the equinoxe precession period (Dont know how this kind of resonance effect could actually work but...)

Glen, a review of DG is in gr-qc/0610079 (i confess it's quite confusing the way it is written now but reorganizing some sections will help: a new version will be available very soon!) and a more pedagogical presentation is in my website www.darksideofgravity.com provided you have good online translators from french to english...

Regards,

F Henry-Couannier

 

[Polestar101]

Even if the Sun were in a 26,000 year orbit with a companion binary the GP-B gyroscopes would still point in a fixed direction relative to the fixed stars.

The orbit of the satellite around the Earth, the Earth around the Sun, the Sun around the COM of its supposed binary system, and that COM around the galaxy would not directly affect the pointing of the gyroscopes. They are in free-fall.

The gyroscopes' axial directions are compared to IM Pegasi. IM Pegasi, a radio binary star, has been being tracked by the VLBI relative to distant quasar 3C454.3. and sometimes two others. When the VLBI data is convoluted with the satellite data the motion of the gyroscopes will be measured relative to the 'fixed stars'.

There will be subtle effects of such a supposed binary companion of the Sun, such as a tiny precession of the ecliptic on top of that caused by the other planets as I described above, but nowhere near the 50.3"/yr precession of the equinoxes, but even so this will not affect the GP-B data, only the astrometric data of a telescope fixed to the wobbling Earth.

In any case, do you think that the gravitational action of the Moon and the Sun on the Earth's oblate spheroid would not produce this 50.3"/yr precession?

Garth

Garth –If there were only a few arc seconds of precession caused by local forces (most now believe local forces are responsible for ALL of the observed 50”p/y), then the earth’s axis would have to obey the local forces, even if it were occurring within a larger moving frame (a solar system in motion). Thus the precession observable we would see from Earth (relative to IM Pegasi) would be equal to the local Earth wobble plus the binary motion. In effect, the local wobble helps translate the binary orbital motion into a larger observable. So it is possible much of the observable we call “precession” may in fact be due to the geometric effect of a solar system in motion.

This geometric effect is a little used phrase but I got it from VLBI. In correspondence with VLBI, I was told that the effect of the solar system moving around the galactic core (at the estimated rate of once every 240 million years) would result in a geometric effect of ~.005”p/y within the precession observable as seen from earth. Consequently, if the sun were part of a binary or ternary (as Glen prefers) system that took ~26,000 years to complete one orbit the “geometric effect” would be about 50” p/y. If this were the case then most (but not all) of what we call precession is actually the geometric effect of the binary motion.

The reason this should probably stay in this GP-B thread is because if GP-B discovers that that they have a signal of this magnitude that needs to be separated out it would be a more fundamental discovery than confirming or honing the amount of the GR effects. Or is there another string that looks at unexpected results from GP-B?

Walter

 

[Garth]

The reason this should probably stay in this GP-B thread is because if GP-B discovers that that they have a signal of this magnitude that needs to be separated out it would be a more fundamental discovery than confirming or honing the amount of the GR effects. Or is there another string that looks at unexpected results from GP-B?

Walter

Walter, as I said in my post #39 above

I notice on your website that you link to several of your papers, but I do not find any references to them being published in peer reviewed journals. In which case such discussion is not appropriate here. You may wish to submit your ideas to the Independent Research Forum after first reading their submission rules.

Rather than have a lengthy discussion about all sorts of unpublished speculative theories, which may mislead others reading the Forum and swamp the thread, what I am doing here is collating a number of predictions of the GP-B experiment that have either been published in a peer reviewed journal, or that have been endorsed and accepted on the physics ArXiv e-print archive. This I hope is in line with the Physics Forums Global Guidelines on

Overly Speculative Posts:
One of the main goals of PF is to help students learn the current status of physics as practiced by the scientific community; accordingly, Physicsforums.com strives to maintain high standards of academic integrity. There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional scientific discussion. Posts deleted under this rule will be accompanied by a private message from a Staff member, with an invitation to resubmit the post in accordance with our Independent Research Guidelines. Poorly formulated personal theories, unfounded challenges of mainstream science, and overt crackpottery will not be tolerated anywhere on the site.

Furthermore I find your theory confused for reasons I will post below.

Garth

 

[Garth]

Garth –If there were only a few arc seconds of precession caused by local forces (most now believe local forces are responsible for ALL of the observed 50”p/y), then the earth’s axis would have to obey the local forces, even if it were occurring within a larger moving frame (a solar system in motion). Thus the precession observable we would see from Earth (relative to IM Pegasi) would be equal to the local Earth wobble plus the binary motion. In effect, the local wobble helps translate the binary orbital motion into a larger observable. So it is possible much of the observable we call “precession” may in fact be due to the geometric effect of a solar system in motion.

There are three issues here that you are confusing, these issues may be expressed as three questions:

1. What is observed on the Earth's surface of the movement of the plane of the Earth's rotation (celestial equator) relative to the plane of the Earth's orbit around the Sun (ecliptic)?

Both the direction of the Earth's rotation axis (because it is an oblate spheroid) and the elements of the Earth's orbit around the Sun may change due to perturbations from other gravitating masses.

2. What is observed by the GP-B satellite of the direction of spin of its four gyroscopes relative to IM Pegasi, a binary radio star that orbits, as the Sun orbits, around the galactic centre?

3. What is the motion of IM Pegasi relative to the distant quasar 3C454.3?

The gyros are in free fall, and great care has gone into making sure all non-gravitational forces (remnant air resistance etc.) on the satellite have been corrected for by using micro-thrusters.

The experiment is testing how a vector is parallel transported through space-time, that is how the gyros' spin access is precessing relative to the distant quasar 3C454.3.

In classical physics the gyros would not precess relative to quasar 3C454.3 at all, but this is not classical physics; in GR and certain other alternative theories, the parallel transportation of the gyros' axial direction vector is expected to precess N-S and E-W by various specific amounts.

The plane of the ecliptic is defined relative to the celestial sphere by the 'Earth as a gyro' spinning at an angle relative to its orbit around the Sun. As I explained in my post #72 above this is affected by the gravitational action on the Earth's oblate spheroid of the Moon, then Sun, then Jupiter and then the other planets and then maybe by a possible solar binary companion. These effects are well modeled, the effect of a binary companion would be small < 0.5"/yr and certainly not the 50.3"/yr precession of the equinoxes.

The gravitational action of the Moon and Sun acting on the Earth's oblate spheroid is cross checked in two independent measurements:

1. The extra nutation of the Earth's axial direction caused by the Sun and Moon varying in relative direction to each other.

2. The accurate determination of the Earth's geoid by the measurements of close Earth satellite orbits.

This geometric effect is a little used phrase but I got it from VLBI. In correspondence with VLBI, I was told that the effect of the solar system moving around the galactic core (at the estimated rate of once every 240 million years) would result in a geometric effect of ~.005”p/y within the precession observable as seen from earth. Consequently, if the sun were part of a binary or ternary (as Glen prefers) system that took ~26,000 years to complete one orbit the “geometric effect” would be about 50” p/y. If this were the case then most (but not all) of what we call precession is actually the geometric effect of the binary motion.

The 'VLBI' geometric effect is a precession of the galactic coordinate system as the Sun orbits the galactic centre, measured relative to the direction of the centre of the galaxy. It does not affect the line of nodes (defined by the intersection of the planes of the ecliptic and that of the celestial equator) relative to distant extra-galactic quasars such as 3C454.3.

Garth

 

[Polestar101]

Garth – Thank you for your thoughts. Unfortunately, they do not address the recently reported concerns of the GP-B team “…sources of noise and interference that are buried in the data, along with the relativity signals” (Feb 9th release). As you know, these need to be separated out to find the GR effects. So while I applaud your efforts to keep this thread focused on the GR effects, let us be aware that the other data picked up by GP-B needs to be understood as it may well be of fundamental importance to this topic. This is the reason that Glen and I and others have “speculated” about possible other motions or contributing factors.

It is clear we disagree about the solidity of current precession theory. You may be right that it is well modeled but not from first principles. Consequently, I do not share your confidence that the effect of a hypothetical companion would be limited to .5”p/y. If much of what we call the precession observable turns out to be primarily the geometric effect of a solar system in motion then it would skew this number radically. Nonetheless, I recognize your traditional viewpoint and agree this must be given first consideration until such sources of “…noise and interference…” can be properly understood. But let us keep in mind that those unexpected signals may be hinting at something we don’t know.

Garth, you have been very supportive of GP-B and party line physics and I sincerely respect your opinions. So give me your best guess: Now that we know there is noise beyond the polhode issue, what do you think is the source of that “…noise and interference…”?

Walter

 

[henryco]

So give me your best guess: Now that we know there is noise beyond the polhode issue, what do you think is the source of that “…noise and interference…”?

Walter

Polestar101, i thought you were only guessing that the GP-B team has big unexpected effects. Now you say that you know for sure that they see those effects. Are you still in contact with them and did you follow the recent evolution of their analysis? Is polestar your real name?

In a theory where space is divided into many areas by discontinuities may be can we imagine that freely falling frames determine the inertial frames only up to a rotating motion. In GR, there is no such distinction between what i would call global and local inerty. Gravity and gravity alone is supposed to completely determine the inertial frames. A local inertial frame is in free fall so that locally, gravitational effects are suppressed as required by the equivalent principle. A global inertial frame might be something else: a frame not rotating in such a way that in it, global inertial forces vanish every where.
not rotating with respect to what?
Newton answered with respect to absolute space
Mach answered with respect to the fixed stars
Einstein answered with respect to the total gravitational field (local sources+global background).

Why not a new kind of answer:
A global inertial frame is one which is not rotating with respect to the local superbubble we are living in...but certainly rotating with respect to the fixed stars. Once the global inertial frame is determined, an extra free fall accélération remains to be applied in order to cancel gravity.
Would all this make sense to you?

best regards

F H-C

 

[Garth]

Garth – Thank you for your thoughts. Unfortunately, they do not address the recently reported concerns of the GP-B team “…sources of noise and interference that are buried in the data, along with the relativity signals” (Feb 9th release). As you know, these need to be separated out to find the GR effects. So while I applaud your efforts to keep this thread focused on the GR effects, let us be aware that the other data picked up by GP-B needs to be understood as it may well be of fundamental importance to this topic. This is the reason that Glen and I and others have “speculated” about possible other motions or contributing factors.

Indeed the other sources of noise and interference have to be understood, but these are affecting the smallest margins of error at the less than 1 milliarcsec/yr level. That is why the proper motion of IM Pegasi, relative to the distant quasar, had to re-assessed at that same level.

It is clear we disagree about the solidity of current precession theory. You may be right that it is well modeled but not from first principles. Consequently, I do not share your confidence that the effect of a hypothetical companion would be limited to .5”p/y. If much of what we call the precession observable turns out to be primarily the geometric effect of a solar system in motion then it would skew this number radically. Nonetheless, I recognize your traditional viewpoint and agree this must be given first consideration until such sources of “…noise and interference…” can be properly understood. But let us keep in mind that those unexpected signals may be hinting at something we don’t know.

As I have said, I don't understand your reasoning. If the solar system is orbiting a solar binary companion, which has to be far enough away not to drastically perturb planetary orbits, it would not show up in the precession of the equinoxes, except at that small (< 1 milliarcsec/yr) level. The line of nodes of the intersection of the ecliptic and celestial equator would point to the same distant quasars, and measured against ordinary local stars would show a small precession of galactic coordinates (due to the Sun orbiting the galactic centre) and those local stars' differential galactic rotation described by the Oort constants. If the hypothetical binary companion was actually observable then it would be seen to move at the system's orbital rate relative to the fixed stars.

Garth, you have been very supportive of GP-B and party line physics and I sincerely respect your opinions. So give me your best guess: Now that we know there is noise beyond the polhode issue, what do you think is the source of that “…noise and interference…”?

The interference, I surmise without yet seeing the GP-B's team analysis, might come from the interaction of the SQUIDs measuring the London effect on the cryogenic gyroscopes' surfaces, from non-inertial forces acting on the spacecraft , drag and thruster leakage, radiation pressures from both external and internal sources and the like.

What is really important is for these 'noises' to be understood correctly and corrected for to reveal the pure relativistic signal, which will yield the answer to the question: "Exactly how is a vector (the gyroscopes' spin axis) parallel transported through the space-time around a rotating Earth in polar orbit around the Sun?"

At a higher level of accuracy (smaller error) the rotation of the Sun about a hypothetical companion could also influence this answer as well as the whole system's rotation around the galaxy.

Periodicities would be important in separating out these various sources of space-time curvature.

The final result is anybody's guess at the moment, so the present question is: "Are the GP-B results consistent with the GR predictions, or with one of the alternatives, or with something completely different (as in F H-C's 'rotating inertial compasses' scenario)?"

As I have said there have been other ways of making the geodetic and frame dragging measurements, such as the dynamics of the double pulsar, but these have theoretical degeneracies in them, so the question is still open.

Not long now to find out!

Garth

 

[Polestar101]

Indeed the other sources of noise and interference have to be understood, but these are affecting the smallest margins of error at the less than 1 milliarcsec/yr level.

Do you know for a fact that the unknown signals are less than 1 milliarcsec? That would be good news for GPB. I understand that is the hope and expectation but was there an actual press release that said that? Did I miss something?

Walter

 

[Garth]

Do you know for a fact that the unknown signals are less than 1 milliarcsec? That would be good news for GPB. I understand that is the hope and expectation but was there an actual press release that said that? Did I miss something?

Walter

Walter from the most recent GP-B website Status update as of 9 February 2007.

Now that the gyro polhode behavior is well understood, we have been able to shift our focus to identifying and addressing some subtle systematic sources of noise and interference that are buried in the data, along with the relativity signals. Identifying and removing as many of these subtle systematic effects as possible is critically important for reducing the margin of error in our final results—especially the frame-dragging result. While we have been making steady progress in these efforts, it has proven to be a slow and painstaking process, and it is now apparent that several more months of data analysis will be required to achieve the lowest possible margin of error.

From which I understand that these subtle systematic effects give errors at the highest level of accuracy they are trying to achieve at the 0.1 milliarcsec level.

The precession of IM Pegasi is already known at the 1 milliarcsec accuracy level, they are evaluating the precession of the gyros at an OOM greater than that.

Of course what they do not say is what are the relativity signals buried in the data and whether they are consistent with the predictions of GR or otherwise.

To refresh this thread, the competing theories and predictions are, with the caveat that some or most of these alternatives may already be inconsistent with present tests of GR as detailed in Clifford Will's paper The Confrontation between General Relativity and Experiment:
Einstein's General Relativity(GR)
Barber's Self Creation Cosmology (SCC),
Moffat's Nonsymmetric Gravitational Theory (NGT),
Hai-Long Zhao's Mass Variance SR Theory (MVSR),
Stanley Robertson's Newtonian Gravity Theory (NG),
Junhao & Xiang's Flat Space-Time Theory (FST).
R. L. Collin's Mass-Metric Relativity (MMR) and
F. Henry-Couannier's Dark Gravity Theory (DG).

The predictions are:

1. GPB Geodetic precession (North-South)
GR = 6.6144 arcsec/yr
SCC = 4.4096 arcsec/yr
NGT = 6.6144 - a small \sigma correction arcsec/yr
MVSR = 6.6144 arcsec/yr
NG = 1.6536 arcsec/yr
FST = 4.4096 arcsec/yr
MMR = -6.56124 arcsec/yr
DG = 6.6144 arcsec/yr

2. GPB gravitomagnetic frame dragging precession (East-West)
GR = 0.0409 arcsec/yr
SCC = 0.0409 arcsec/yr
NGT = 0.0409 arcsec/yr
MVSR = 0.0102 arcsec/yr
NG = 0.0102 arcsec/yr
FST = 0.0000 arcsec/yr
MMR = -0.01924 arcsec/yr
DG = 0.0000 arcsec/yr

And from The stars of Pegasus from the Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991, Yale University Observatory) as distributed by the Astronomical Data Center at NASA Goddard Space Flight Center.

IM PegasiRA J2000 : 22h 53m 2.3s
DEC J2000 : +16° 50' 28"
Proper motion in RA : -0.018 arcsec/y
Proper motion in DEC : -0.024 arcsec/y
mag : 5.64
MK spectral class : K1-2II-III

The Proper motion in RA will affect the E-W precession and the
Proper motion in DEC will affect the N-S precession.

Garth

 

[sylas]

Hi Garth. There is another "theory" you might like to add to this list.

Ronald Hatch, famous for work with the GPS system, has proposed a theory which addresses defects as he sees them in relativity. The theory is called "Modified Lorentz Ether Theory" (MLET). It is a part of what Hatch calls "Ether Gauge Physics". The home page for this theory is http://www.egtphysics.net/Index.htm

In a paper at that site, Hatch says:

Another Prediction

Incidentally, I have already predicted [23] that Gravity Probe B will detect a different amount of geodetic precession than that predicted by the general theory. I used a rather long argument to conclude that the predicted spin-orbit component (2.3 arc seconds per year) was only half the size it should be. The rest of the geodetic precession was due to space curvature and contributed 4.6 arc seconds per year. A simple method of arriving at my new prediction is to note that, if one measures time with a clock external to the gravitational field (local clock rate is immaterial), the "space curvature" (gradient of ether density) is twice what the general theory predicts. This leads directly to my prediction that the total geodetic precession measured by GPB will be 9.2 arc seconds per year rather than the general theory prediction of 6.9 arc seconds per year.

—source​

I don't know the date on this; I think it might be around 2000. The figures may need a bit of fixing. If someone knows what are curvature and spin-orbit components, then it looks like you can just double the spin-obit portion to get Hatch's prediction.

The paper mentions frame dragging, but does not appear to give any alternative prediction that I can see.

I don't know if this is serious enough to merit including in your list, but there you go. You can add to the list:

Ronald Hatch's Modified Lorentz Ether Theory (MLET)
1. GPB Geodetic precession (North-South)
MLET = ~9 arcsec/yr

Cheers -- Sylas

 

[Garth]

Hi Garth. There is another "theory" you might like to add to this list.

Ronald Hatch, famous for work with the GPS system, has proposed a theory which addresses defects as he sees them in relativity. The theory is called "Modified Lorentz Ether Theory" (MLET). It is a part of what Hatch calls "Ether Gauge Physics". The home page for this theory is http://www.egtphysics.net/Index.htm

In a paper at that site, Hatch says:

I don't know the date on this; I think it might be around 2000. The figures may need a bit of fixing. If someone knows what are curvature and spin-orbit components, then it looks like you can just double the spin-obit portion to get Hatch's prediction.

The paper mentions frame dragging, but does not appear to give any alternative prediction that I can see.

I don't know if this is serious enough to merit including in your list, but there you go. You can add to the list:

Ronald Hatch's Modified Lorentz Ether Theory (MLET)
1. GPB Geodetic precession (North-South)
MLET = ~9 arcsec/yr

Cheers -- Sylas

Hi Sylas and welcome to the Forums!

It appears that the theory has not been published in a peer reviewed journal or endorsed and put on the physics arXiv, so I won't include it at this stage.

But I'll keep ~9 arcsec/yr in mind next month, just in case.

Garth