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William
2014-Mar-24, 11:33 AM
Implications of failure to directly detect gravitational waves

This thread’s primary purpose is an update of the direct detection of gravitational wave. At this point in time there has been no direct detection of gravitational waves. The current sensitivity of gravity wave detectors is above the minimal level and there should have been detection of gravitational waves.

As noted below, in 2017 the gravitational wave sensor detectors will be improved by a factor of 10. If there is again no detection of gravitational waves that will indicate that there are one or more fundamental errors in general relativity.

If gravitational waves do not occur that would also indicate that the large scale changes in CMB polarization were not caused by gravitational waves.

Comment:
It has been alleged that the recently found large scale polarization changes in the CMB (the observed polarization changes in the CMB were two to three times greater than what was predicted by theory) was caused by gravitational waves during the theoretical inflation period.

That gravitational wave hypotheses to explain the CMB large scale polarization changes is only viable if there was a period of inflation (I will start a separate thread to discuss why cosmic inflation was invented and will start a third thread to discuss actual large scale observations which interestingly are not explained by inflation and have been ignored.)

See next comment for results of LIGO-Virgo runs and an over view of what should create gravity waves if general relativity is correct.

William
2014-Mar-24, 11:40 AM
As noted below the second more sensitive run of LIGO failed to detect gravitational waves. The LIGO sensors will be replaced with a new design that will increase the gravitational wave sensitivity by a factor of 10. The new more sensitive gravity wave detector is scheduled to be in service in 2017. If gravity waves are not detected with the more sensitive detectors that will indicate there are one or more errors in general relativity.

http://www.ligo.org/science/Publication-S6BurstAllSky/



Listening for gravitational-waves with "ears wide open"

No gravitational wave signal was detected in this search using 1.74 years of good quality data, including the previous LIGO-Virgo joint science run. Although disappointing, this "null result" is still quite informative, as it allows us to constrain models of gravitational waves emission and astrophysical source populations. Hence, the team turned to determining what signals could have been detected if they had arrived at Earth. In particular, the result constrains the rate for strong gravitational wave events (i.e. signals that would certainly have been detected) to be lower than 1.3 per year at 90% confidence level: we call this an upper limit. However, weaker events would not necessarily have been detected. The team mapped out the detection efficiency for gravitational-wave signals as a function of their waveform and strength by repeatedly adding simulated signals to the data and re-analyzing them. The second figure on the right shows the resulting rate limits versus signal strength for several hypothetical waveforms.

The third figure shows that our upper limit mainly depends on the detectors' sensitivity at the characteristic frequency of the signal. In other words, at any given frequency, the data analysis algorithm was capable of detecting a wide range of simulated waveforms with comparable performance. So we can be confident that the search would have caught pretty much any type of gravitational wave burst that arrived during that time at the sensitivity level achieved by present detectors.


Paper that presents the LIGO-Virgo data analysis and results.


All-sky search for gravitational-wave bursts in the second joint LIGO-Virgo run

http://arxiv.org/pdf/1202.2788v3.pdf

http://www.space.com/20939-gravitational-wave-detector-search.html

"I think the confidence level is quite high" that the advanced experiments will see gravitational waves, Kasliwal told SPACE.com. "The sensitivity is now such that if Einstein's general relativity is right, then we should see these things." She estimated that the experiments are likely to detect between four and 400 gravitational waves a year. "But zero would be quite a disaster. We'd need to rethink our understanding of gravity."
Those waves should be detectable by experiments called Advanced LIGO (Laser Interferometer Gravitational Wave Observatory) and Advanced Virgo, set to come online in 2017. They will each use giant L-shape detectors in Louisiana, Washington and Italy to search for minute changes in the lengths of the detectors' arms caused when gravity waves pass through. At the corner of the "L," a laser is split into two beams that travel back and forth down the length of the two arms (each between 1.2 miles, or 2 kilometers, and 2.5 miles, or 4 kilometers, long), bouncing off mirrors at each end. If a gravitational wave passed through, it would stretch and compress these lengths, depending on its orientation, creating a small but detectable difference in the length of the two arms.


Initial versions of LIGO and Virgo are already operating, but aren't yet sensitive enough to detect gravitational waves. When they are upgraded to higher sensitivities, though, they should reveal hidden gravitational waves for the first time. These observations wouldn't just prove the existence of gravitational waves, they would offer unprecedented information about the rare and extreme cosmic phenomena that create them.


According to general relativity, massive objects warp space and time around them, like a bowling ball dropped onto a sheet of rubber, causing passing objects, and even light, to travel along curved paths. When two extremely dense objects, such as neutron stars (stars so dense the protons and electrons in their atoms collapse to form neutrons) or black holes, orbit each other in binary pairs, their interactions should create ripples in the fabric of space-time called gravitational waves. The most powerful waves would arise when two neutron stars or black holes merge together.



http://en.wikipedia.org/wiki/Gravitational_wave

Cougar
2014-Mar-24, 12:14 PM
If there is again no detection of gravity waves that will indicate that there are one or more fundamental errors in general relativity.

...or a fundamental error in your logic. If it's as you say, perhaps you could then explain why the orbital period of the Hulse-Taylor pulsar is decreasing precisely as GR predicts from the emission of gravitational waves?

mkline55
2014-Mar-24, 01:01 PM
...or a fundamental error in your logic. If it's as you say, perhaps you could then explain why the orbital period of the Hulse-Taylor pulsar is decreasing precisely as GR predicts from the emission of gravitational waves?
I think the point was that a theory makes predictions, and if those predictions do not bear fruit, then that may be a problem with the theory. Event A causes effect B, which must result in observation C. If C cannot be observed, then what? The sensor design is also based on a plausible theory. Perhaps it's a problem with that theory instead.

William
2014-Mar-24, 01:20 PM
...or a fundamental error in your logic. If it's as you say, perhaps you could then explain why the orbital period of the Hulse-Taylor pulsar is decreasing precisely as GR predicts from the emission of gravitational waves?

There is always ultimately a logical explanation. When theory does not agree with observation something needs to change.

If I remember correctly, the detectability of the gravitational wave is dependent on the speed of transmission of the wave. The emission of the gravitational wave can still occur.

tusenfem
2014-Mar-24, 01:38 PM
Can we please use "gravitational waves" because gravity waves are observed all the time.

mkline55
2014-Mar-24, 01:45 PM
There is always ultimately a logical explanation. When theory does not agree with observation something needs to change.

If I remember correctly, the detectability of the gravity wave is dependent on the speed of transmission of the wave. The emission of the gravity wave can still occur.
As I understood it, gravitational waves (and gravity waves) must travel at or very close to light speed. In theory, anyway.

tusenfem
2014-Mar-24, 02:30 PM
As I understood it, gravitational waves (and gravity waves) must travel at or very close to light speed. In theory, anyway.

Nope, gravity waves travel at the local sound speed or slower.
Gravitational waves may travel at the speed of light.
But yes, we will have to measure gravitational waves first.
From the European side there is now the scaled down LISA project, called eLISA: https://www.elisascience.org/
(eLISA was now selected by ESA, although LISA-pathfinder still needs to be launched, scheduled for 2015, to show that the technical stuff may or may not work ...)

Ken G
2014-Mar-24, 03:07 PM
Also, we must bear in mind that we need a source of the gravitational waves, which would generally be a short-lived and random event we cannot control. So 1.3 years of null results from LIGO don't really mean that much, it would mean a lot more if we had a known astronomical event that was clearly predicted to generate detectable gravitational waves and they were not seen. If that had happened, we would already be in a pickle, we wouldn't need advanced LIGO to tell us we are in a pickle! But instead, it might just be that the LIGO builders didn't get lucky, or the astronomers need to think more about how common or uncommon these events really are.

Jerry
2014-Mar-29, 07:22 PM
...or a fundamental error in your logic. If it's as you say, perhaps you could then explain why the orbital period of the Hulse-Taylor pulsar is decreasing precisely as GR predicts from the emission of gravitational waves?
There are many reasons today to flag the Hulse-Taylor results. Remember, the gravitational wave detectors assembled a generation ago were built on the premise that Hulse and Taylor have correctly calculated the energy budgets of the pair and the strength of the GW signal. We have exceeded the sensitivity needed to find results based upon these admittedly optimistic calculations by more than 1000 times. Nothing.

At the time of Hulse-Taylor; little was known about the magnetic moment of collapsing pairs and the full implications of spin upon GR energy budgets were not included in the calculations.

Hulse and Taylor were running 'round cow' estimates; and without the direct detection of gravitational waves with today's tools there is no valid proof of their assumptions.

On the other hand, if gravitational are locally detected, and most especially those from local, collapsing pairs, this would/will provide any and every vindication. The local failures do mean something is wrong.

borman
2014-Mar-29, 07:50 PM
Where does the energy go if there is no gravitational wave energy to balance the equation?

Jerry
2014-Mar-29, 08:01 PM
I think the point was that a theory makes predictions, and if those predictions do not bear fruit, then that may be a problem with the theory. Event A causes effect B, which must result in observation C. If C cannot be observed, then what? The sensor design is also based on a plausible theory. Perhaps it's a problem with that theory instead.

There have been a dozen redo's on how sensitive a detector must be to capture astrophysical causing the gravitational wave signal predicted by general relativity. There was serious money placed with London bookies in ~2004 by scientist predicting gravitational waves would be observed no later than 2010; and by 2010 the detectors were exceeding the sensitivity expected at the time the predictions were made!

This latest round of failures would be absolutely stunning to a relativistic physicist in 1985. (The old adage about the toad not jumping out of the slowly heated pot comes to mind.)

Jerry
2014-Mar-29, 08:26 PM
Where does the energy go if there is no gravitational wave energy to balance the equation?Good question. You can ask the same question as to why is the moon moving away from the earth (Is there really that much energy transferred via tides?); and is the spin-down of the earth sufficient to provide the orbital kick. If tides are transferring energy from one body another here; the same mechanism certainly operates on stars spinning down; and we don't know how much 'braking energy' is absorbed and dissipated calometricly. It is hypothesized that gamma ray bursts are initially gravitational wave couplings; and we know they are associated with tidal disruptions. Gamma rays are often beamed - not necessarily in our direction. Energy budgets are needed for these emissions.

StupendousMan
2014-Mar-29, 08:47 PM
There was serious money placed with London bookies in ~2004 by scientist predicting gravitational waves would be observed no later than 2010; and by 2010 the detectors were exceeding the sensitivity expected at the time the predictions were made!


Do you have any evidence for this claim, or a name for "scientist"?

Shaula
2014-Mar-29, 10:04 PM
http://www.matterpr.com/index.php/from-our-archives-uk-scientist-gambles-on-gravitational-waves/

£25 is not serious money

Edit: Another way to phrase the story would be "Researcher has faith in their research area - so much faith that they put a very small bet on it being successful"

Jerry
2014-Mar-30, 12:36 AM
http://www.matterpr.com/index.php/from-our-archives-uk-scientist-gambles-on-gravitational-waves/

£25 is not serious money

Edit: Another way to phrase the story would be "Researcher has faith in their research area - so much faith that they put a very small bet on it being successful"


'I would have had much more money on at the odds they were offering but the maximum bet they allowed me to have was £25!” Gravitational waves are ripples in the fabric of spacetime and are one of the more exotic predictions of Einstein’s theory of gravity – General Relativity. Initially thought not to exist, the reality of gravitational waves is no longer doubted by scientists. The gradual changes in the orbit of a binary pulsar called PSR 1913 +16 (a pair of orbiting neutron stars, one of which is a pulsar emitting precisely timed radio pulses) can be explained only if angular momentum and energy is carried away from this system by gravitational waves.

"No longer doubted" Means we have gambled over a billion dollars on gravitational wave detectors, all of which the project PIs assured the various sponsoring agencies they had a fair chance of success. These predictions are based upon both the Einstein prediction and the observation that the angular momentum of binary pairs is shrinking at a 'relativistic' rate.

Strange
2014-Mar-30, 12:53 AM
Good question.

In other words, you don't have an alternative model.

Jerry
2014-Mar-30, 06:41 AM
In other words, you don't have an alternative model.
In 1985, I expected gravitational waves to surface, just like almost everyone else. But I was skeptical about some of the Hulse and Taylor assumptions - the doppler shifts that had to be measured were really small; and likewise the mass estimates and timing signatures just seemed to be too precise to be real.

Of course I have a model - and like all models, there are a number of round cow assumptions involved. Models don't really mean much until they are investigated and challenged with real experimental data designed to test the theory. We have spent three times as many years; hundreds of thousand of man hours and hundreds of millions more dollars in this failed search for gravitational waves than we did nullifying Michelson and Morley. We could be whipping a dead horse.

Ken G
2014-Mar-30, 12:47 PM
It is perfectly normal for null detections to be used to falsify theories, that's what happened to Galilean relativity in the Michelson-Morely experiment. It is also possible to get Nobel prizes for null results, and for them to be worth considerable expense. But for a null result to have that effect, you have to know very clearly the sensitivity of your instrument, and you also have to know very clearly the nature of your sources. Neither of those things have anything to do with the theory you are testing. That the null results of LIGO have not inspired theorists to correct GR tells me that those two pieces are simply not in place here. Which stands to reason, because how do you know the sensitivity of a gravitational wave detector anyway? You have nothing else to calibrate it with, because it needs to be the most sensitive motion detector on the planet. Also, it is trying to detect neutron star mergers, and what other means do you have for knowing when that is happening? So the problem is, we have an instrument whose sensitivity we do not really know, looking for sources we do not know where or when they exist. This is why null results cannot be used-- we need detections.

A normal thing to ask any experimenter is, "and what will you be able to conclude if you get a null result?" If that question were asked to the LIGO proposers, they might have said "we'll know something is wrong with GR", but that's clearly not true, because no one is trying to fix GR. So we should ask the same question to advanced LIGO, and they'll say the same thing, but if advanced LIGO doesn't see anything either, will we see theorists en masse trying to fix GR? That's the litmus test right there. What I want to know is, is there any relatively known sources of gravitational waves (like a Hulse-Taylor pulsar) that advanced LIGO should be able to detect, or does everything still hinge on the neutron-star merger rate? It can't be right that the Hulse-Taylor pulsar should have been detected by a factor of 1000, that would certainly have motivated every gravitational theorist in creation to fix GR.

Strange
2014-Mar-30, 12:56 PM
Of course I have a model - and like all models, there are a number of round cow assumptions involved. Models don't really mean much until they are investigated and challenged with real experimental data designed to test the theory.

And how well is your model doing when tested against the data?

StupendousMan
2014-Mar-30, 04:47 PM
In 1985, I expected gravitational waves to surface, just like almost everyone else. But I was skeptical about some of the Hulse and Taylor assumptions - the doppler shifts that had to be measured were really small; and likewise the mass estimates and timing signatures just seemed to be too precise to be real.


Hulse and Taylor measured the motion of the pulsar by tiny changes in the arrival time of its pulses, not by the Doppler effect (which would have involved changes in the frequency of the radio waves).

Jerry
2014-Mar-30, 08:00 PM
Hulse and Taylor measured the motion of the pulsar by tiny changes in the arrival time of its pulses, not by the Doppler effect (which would have involved changes in the frequency of the radio waves).That self-same timing is Dopplered, by all combed motions of the earth; the rotation, the period of the day to the orbit of the moon, the earth's relative path and even the solar path relative to the emitting pair; and unless every one of these are well counted; along with the estimates of mass and every other conceivable flaw, there is always room for doubt in the conclusions of Hulse and Taylor.

Again; if you apply the 'Jerry test' - if I sought to disprove relativity by the missed gyrations of a pair of pulsars; would anyone accept all the intricacies of timing I must derive to firmly disprove such a hard held theory? I think not; and I know a local detection of gravitational waves is necessary to confirm the summation of their estimates. Hulse-Taylor fails the Jerry test, because if "Hulse-Taylor"-like results were used to 'disprove relativity', no one would accept this conclusion.

But there are calculations that are based upon the Hulse-Taylor mass loss predictions that these emitted gravitational waves must do what gravitational waves must do: bend local space and time. The magnitude of these disruptions is certainly a contested area of theory. Anderson was sure he had captured them in the late 1970s. With every new constraint, the basic assumptions bleed a little more.

It cannot be over-stressed how certain gravitational wave theorist were that we would be holding them in our hands today. When the LIGO cooperative network was assembled; they started adding the names of every contributor to every paper put out by every gravitational wave researcher so they would all hold credit to the imminent discovery - and yes, they did state quite clearly, that if designed sensitivities were met and waves were not detected by 2015; it was time to seriously question the theory.

Shaula
2014-Mar-30, 08:23 PM
Thankfully in the real world we don't have to rely on the Jerry test. Gravitational wave detectors are not the only line of evidence supporting GR as it stands, so this skewed application of a fairly nonsensical test is not required. These observations support GR, multiple lines of evidence support it. So one missing observation is not enough to throw the whole theory out.

I'd love to see any model, yours included, actually pass this 'Jerry test' as you choose to apply it.

Jerry
2014-Apr-02, 12:02 AM
Thankfully in the real world we don't have to rely on the Jerry test. Gravitational wave detectors are not the only line of evidence supporting GR as it stands, so this skewed application of a fairly nonsensical test is not required. These observations support GR, multiple lines of evidence support it. So one missing observation is not enough to throw the whole theory out.

Most of Maxwell's theory survived the Michelson Morley test. It is only a cosmic aether which is precluded by the result. Most tests of GR include Maxwellian components; that are routinely estimated and subtracted to identify the relativist portion. (I am speaking here, of the solar gravitational deflection and the Gravity probe B tests.) But the point is that in order for GR to survive as a viable theory, gravitational waves must be observed. Cosmic lensing can always be explained using Maxwellian approachs, but gravitational waves are the unique signature of relativity. If 'space' does not expand and compress the arms of the LIGO interferometer; GR has failed the same test aether did.


I'd love to see any model, yours included, actually pass this 'Jerry test' as you choose to apply it. The 'Jerry test' is simply a restatement of the need to control all variables. It is generally not possible to even postulate that new physics are needed when even obscure or unlikely variability exists within a system. This same standard is not applied to most tests of general relativity.

For example, when the signal from the Gravity-B probe was not consistent with GR; theorists tinkered with possible, but unanticipated Maxwellian forces that could be subtracted out of the equation and leave a residing GR signal that is consistent with theory. But there was no way to test these assumptions, and the conclusion published on NASA sites (that "GR" had passed another test) is not warranted.

See: http://www.nasa.gov/mission_pages/gpb/gpb_results.html

This article describes the actual experimental errors encountered that were unexpected and are of a severe enough magnitude to play havoc with the results:

http://physics.aps.org/articles/v4/43


First, because each rotor is not exactly spherical, its principal axis rotates around its spin axis with a period of several hours, with a fixed angle between the two axes. This is the familiar “polhode” period of a spinning top and, in fact, the team used it as part of their analysis to calibrate the SQUID output. But the polhode period and angle of each rotor actually decreased monotonically with time, implying the presence of some damping mechanism, and this significantly complicated the calibration analysis. In addition, over the course of a day, each rotor was found to make occasional, seemingly random “jumps” in its orientation—some as large as 100 milliarcseconds. Some rotors displayed more frequent jumps than others. Without being able to continuously monitor the rotors’ orientation, Everitt and his team couldn’t fully exploit the calibrating effect of the stellar aberration in their analysis. Finally, during a planned 40-day, end-of-mission calibration phase, the team discovered that when the spacecraft was deliberately pointed away from the guide star by a large angle, the misalignment induced much larger torques on the rotors than expected. From this, they inferred that even the very small misalignments that occurred during the science phase of the mission induced torques that were probably several hundred times larger than the designers had estimated.

The G-Probe B scientist threw in a bunch of Maxwellian corrections, but the results, as stated by APS are much hedgier than the NASA article:


The original goal of GP-B was to measure the frame-dragging precession with an accuracy of 1%, but the problems discovered over the course of the mission dashed the initial optimism that this was possible. Although Everitt and his team were able to model the effects of the patches, they had to pay the price of the increase in error that comes from using a model with so many parameters. The experiment uncertainty quoted in the final result—roughly 20% for frame dragging—is almost totally dominated by those errors.

This is not the kind of results I could use to launch a new theory!

Ken G
2014-Apr-02, 01:33 AM
What is unclear in all that, however, is whether a 20% error is so large that one cannot say GR passed a test. Frame dragging might be a bit like a talking dog-- it's not that the dog talks well, it's that it talks at all.

Reality Check
2014-Apr-02, 01:57 AM
But the point is that in order for GR to survive as a viable theory, gravitational waves must be observed.

That is not right, Jerry: GR has been a viable theory ever since it matched the perihelion precession of Mercury. What GR is currently is a "not completely tested" theory. The outstanding test is the direct detection of gravitational waves.
Direct detection of gravitational waves would be confirmation of the existing indirect evidence for gravitational waves. GR would still be a viable theory in a hypothetical universe where direct detection of gravitational waves was impossible.

I would like to see your citations for cosmic lensing being explained by "Maxwellian approachs".

If LIGO does not detect gravitational waves then it need not be a problem with GR. It could be a problem with astrophysics, e.g. calculations of the frequency of events that can be detected. It could even be a statistical fluke. Basically we have to look for long enough that it is statistically likely that we would have detected gravitational waves. If is a problem with GR then a new theory will be needed which duplicates all of the successes of GR except gravitational waves (either making them undetectable with current technology or eliminating then entirely).

As for Gravity Probe B (http://en.wikipedia.org/wiki/Gravity_Probe_B): When unexpected signals were received due to manufacturing flaws, the data was corrected for the incorrect manufacturing:

This created a classical dipole torque on each rotor, of a magnitude similar to the expected frame dragging effect. In addition, it dissipated energy from the polhode motion by inducing currents in the housing electrodes, causing the motion to change with time. This meant that a simple time-average polhode model was insufficient, and a detailed orbit by orbit model was needed to remove the effect. As it was anticipated that "anything could go wrong", the final part of the flight mission was calibration, where amongst other activities, data was gathered with the spacecraft axis deliberately mis-aligned for 24 hours, to exacerbate any potential problems. This data proved invaluable for identifying the effects. With the electrostatic torque modeled as a function of axis misalignment, and the polhode motion modeled at a sufficiently fine level, it was hoped to isolate the relativity torques to the originally expected resolution.
(my emphasis added)
So as many variables as possible were controlled in the Gravity Probe B experiment (the goal of any experiment).

The frame dragging result from Gravity Probe B was not impressively accurate (19%), the geodetic drift rate was quite accurate (0.28%). They both confirmed the GR predictions because the predicted values were within the error limits with discrepancies of 0.07% and 5%.

Jerry
2014-Apr-02, 08:34 PM
That is not right, Jerry: GR has been a viable theory ever since it matched the perihelion precession of Mercury. What GR is currently is a "not completely tested" theory. The outstanding test is the direct detection of gravitational waves.
Direct detection of gravitational waves would be confirmation of the existing indirect evidence for gravitational waves. GR would still be a viable theory in a hypothetical universe where direct detection of gravitational waves was impossible. It is a viable theory, but not the only viable theory. It matches the precession of Mercury because this is precisely the astronomical phenomenon that Newtonian gravity could not explain that Einstein targeted with his derivations. His predictions include the processions of the other planets, frame dragging, gravitational waves, time dilation and gravitational lensing.

When General relativity is used to predict the procession of other planets, it works quite well with most, but it is less exact; and the difference is thought to be either Maxwellian or 3rd body complexities that that not yet understood.


I would like to see your citations for cosmic lensing being explained by "Maxwellian approachs". The first test of gravitational lensing was conducted during a 1919 eclipse by Eddington. This confirmed the displacement of a star in Haydes was in more-or-less agreement with GR, but with a wide margin of error. When NASA conducted a similar test using radio signals from (Mariner 10?); the test failed miserably. Later tests were able to confirm a GR displacement, but only after a Maxwellian component of about the same magnitude is subtracted from the solution. (To be clear, I am using Maxwellian to describe any electromagnetic property, including thermaldyamics.) There is little question today that when Eddington announced the success of his observations, he over-stated the case for GR, relative to his margin-of-error.

http://simonsingh.net/media/articles/maths-and-science/1919-eclipse-and-general-relativity/


If LIGO does not detect gravitational waves then it need not be a problem with GR. It could be a problem with astrophysics, e.g. calculations of the frequency of events that can be detected. It could even be a statistical fluke. Basically we have to look for long enough that it is statistically likely that we would have detected gravitational waves. If is a problem with GR then a new theory will be needed which duplicates all of the successes of GR except gravitational waves (either making them undetectable with current technology or eliminating then entirely). What the failures should tell us, is that it is too early to claim GR is an astrophysically proven fact; and we should go back over other tests where the error margin is greater-than-expected, with a broader license to figure out why.


As for Gravity Probe B (http://en.wikipedia.org/wiki/Gravity_Probe_B): When unexpected signals were received due to manufacturing flaws, the data was corrected for the incorrect manufacturing:


(my emphasis added)
So as many variables as possible were controlled in the Gravity Probe B experiment (the goal of any experiment).

The frame dragging result from Gravity Probe B was not impressively accurate (19%), the geodetic drift rate was quite accurate (0.28%). They both confirmed the GR predictions because the predicted values were within the error limits with discrepancies of 0.07% and 5%.Most, but not all of the chronicled successes of GR could be from other phenomenon. (Any gravitational theory that does not use an instantaneous force will also likely case frame dragging.)

The unique signatures of GR are time dilation and gravitational waves. Rubidium and cesium clocks do appear to beat more slowly in orbit; but the corrections for such are anything but straightforward http://relativity.livingreviews.org/Articles/lrr-2003-1/download/lrr-2003-1Color.pdf

Reality Check
2014-Apr-03, 03:35 AM
It is a viable theory, but not the only viable theory. It matches the precession of Mercury because this is precisely the astronomical phenomenon that Newtonian gravity could not explain that Einstein targeted with his derivations. His predictions include the processions of the other planets, frame dragging, gravitational waves, time dilation and gravitational lensing.

And the success of those predictions are why GR is a viable theory, Jerry. The less exact matches with the precession of other planets is because their precession is less accurately measured.


The first test of gravitational lensing was conducted during a 1919 eclipse by Eddington. ...

Many people know that the 1919 expedition results were quite rough. Modern analysis of the expedition's data tends to support Eddington's conclusion. And of course if has been replicated several times.
The deflection of light by the Sun is not usually considered a case of gravitational lensing since an image is not formed (at least I tend to see it discussed separately from lensing). It is certainly evidence for lensing.
But where are your citations for cosmic lensing being explained by "Maxwellian approachs"?


What the failures should tell us, is that it is too early to claim GR is an astrophysically proven fact;

And few people claim that. What people generally claim is that GR is an astrophysically supported scientific theory. What the failures actually tell us is that GR is not a fully tested scientific theory.


The unique signatures of GR are time dilation and gravitational waves. Rubidium and cesium clocks do appear to beat more slowly in orbit; but the corrections for such are anything but straightforward http://relativity.livingreviews.org/Articles/lrr-2003-1/download/lrr-2003-1Color.pdf
What does the complexity of the calculations have to do with the validity or not of GR, Jerry?
Ashby 2003 is saying that rubidium and cesium clocks actually beat more slowly in orbit and correcting them needs the inclusion of several effects (including GR).

Reality Check
2014-Apr-03, 03:40 AM
Later tests were able to confirm a GR displacement, but only after a Maxwellian component of about the same magnitude is subtracted from the solution. (To be clear, I am using Maxwellian to describe any electromagnetic property, including thermaldyamics.)
Citations and clarification please, Jerry.
You seem to be saying that all tests of deflections of light by the Sun only match GR after an similar deflection by "a Maxwellian component" is subtracted.

Jerry
2014-Apr-15, 12:46 PM
Citations and clarification please, Jerry.
You seem to be saying that all tests of deflections of light by the Sun only match GR after an similar deflection by "a Maxwellian component" is subtracted.

NASA dropped these document (and many others) when they revised the website

http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B27642-000A
http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B21015-000A
http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B28647-000A
http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1973-027A-36
http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1968-014A-20
http://nssdc.gsfc.nasa.gov/nmc/datasetDisplay.do?id=PSPA-00058

This is a tertiary reference: http://radioscience.jpl.nasa.gov/publications/dsn.html


The 100 kW uplink was provided by the Goldstone 26-m antenna. In 1968, Goldstein (1969) duplicated the experiment with the superior conjunction of Pioneer 6 and obtained results similar to those from the Mariner 4 experiment. The radially dependent spectral broadening obtained by Goldstein and colleagues reflected the now better understood relationship between spectral broadening and integrated coronal electron density.

Shaula
2014-Apr-15, 12:52 PM
Given that most of those are not available and the ones that are refer to the radio frequency measurements and corrections made for solar observation experiments more than just a list of useless references might be helpful in understanding what you base your unshakeable belief that GR is wrong on. A link to the actual documents? A summary of their content as you see it? Links to published papers based on these data sources?

Strange
2014-Apr-15, 01:32 PM
NASA dropped these document (and many others) when they revised the website

http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B27642-000A
http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B21015-000A
http://nssdc.gsfc.nasa.gov/nmc/publicationDisplay.do?id=B28647-000A
http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1973-027A-36
http://nssdc.gsfc.nasa.gov/nmc/experimentDisplay.do?id=1968-014A-20
http://nssdc.gsfc.nasa.gov/nmc/datasetDisplay.do?id=PSPA-00058

This is a tertiary reference: http://radioscience.jpl.nasa.gov/publications/dsn.html

That doesn't appear to say anything about gravitational lensing.

Jerry
2014-Apr-15, 01:36 PM
Here is a good place to start:

http://arxiv.org/ftp/arxiv/papers/0709/0709.0685.pdf


Note that the revised 4-inch result places the Einstein prediction even further outside the
limits of the error bars for this instrument. In general eclipse expeditions often recovered
a value in excess of the GR prediction and were only sporadically successful in wrestling
Einstein’s prediction within their error-bars. This situation had barely improved even by
the time of the last such expeditions in the mid-1970s. It is only with radio telescopes
measuring quasars being occulted by the relatively radio-quiet Sun, thus with no need for
an eclipse, that the Einstein value has been precisely confirmed (Will 1993). Of course
the so-called Newtonian result fares even worse compared to the high value obtained.

So in general, measurements of the gravitational deflection are slightly greater than the relativistic prediction; and it is only with radio telescopes that a value consistent with relativity is obtained. The irony here, is that the radio band width is the most susceptible to 'Maxwellian' distortions; that is, most greatly effected by magnetic fields.

Shaula
2014-Apr-15, 02:06 PM
Here is a good place to start:

http://arxiv.org/ftp/arxiv/papers/0709/0709.0685.pdf
You made a series of very specific claims about the 'Maxwellian' corrections required to get GR to give the right answer and backed these up with a list of supposedly supporting citations. GR does not rest solely on an experiment performed in 1919 and I see little to no value, as pertains to this discussion, in wading through a historical study of the personalities involved in this experiment. Please back up your claims by providing actual citations, not a list of papers no longer available and a vague assurance that they were relevant.

Jerry
2014-Apr-15, 02:07 PM
You made a series of very specific claims about the 'Maxwellian' corrections required to get GR to give the right answer and backed these up with a list of supposedly supporting citations. GR does not rest solely on an experiment performed in 1919 and I see little to no value, as pertains to this discussion, in wading through a historical study of the personalities involved in this experiment. Please back up your claims by providing actual citations, not a list of papers no longer available and a vague assurance that they were relevant.


http://arxiv.org/ftp/arxiv/papers/0709/0709.0685.pdf


Note that the revised 4-inch result places the Einstein prediction even further outside the
limits of the error bars for this instrument. In general eclipse expeditions often recovered
a value in excess of the GR prediction and were only sporadically successful in wrestling
Einstein’s prediction within their error-bars. This situation had barely improved even by
the time of the last such expeditions in the mid-1970s. It is only with radio telescopes
measuring quasars being occulted by the relatively radio-quiet Sun, thus with no need for
an eclipse, that the Einstein value has been precisely confirmed (Will 1993). Of course
the so-called Newtonian result fares even worse compared to the high value obtained.

So in general, measurements of the gravitational deflection are slightly greater than the relativistic prediction; and it is only with radio telescopes that a value consistent with relativity is obtained. The irony here, is that the radio band width is the most susceptible to 'Maxwellian' distortions; that is, most greatly effected by magnetic fields.

Applying the Jerry test, if I were trying to prove an non-Einsteinian solution; and every measurement failed to meet my expectations, except for selected results in the long radio bandwidths, no one would allow this kind of cherry-picking.

Strange
2014-Apr-15, 02:14 PM
Here is a good place to start:

http://arxiv.org/ftp/arxiv/papers/0709/0709.0685.pdf

I don't get it.


So in general, measurements of the gravitational deflection are slightly greater than the relativistic prediction

Two larger and two smaller, according to the history article you cite. So, in general, no. (The average is less than predicted by GR.)


; and it is only with radio telescopes that a value consistent with relativity is obtained. The irony here, is that the radio band width is the most susceptible to 'Maxwellian' distortions; that is, most greatly effected by magnetic fields.

Citation needed.

Shaula
2014-Apr-15, 02:18 PM
You said:

Later tests were able to confirm a GR displacement, but only after a Maxwellian component of about the same magnitude is subtracted from the solution. (To be clear, I am using Maxwellian to describe any electromagnetic property, including thermaldyamics.)

The G-Probe B scientist threw in a bunch of Maxwellian corrections

Most tests of GR include Maxwellian components; that are routinely estimated and subtracted to identify the relativist portion.

Please provide citations as to the nature and calculation/estimation of these effects. So far all you have given is some data about how the GP-B sensors were calibrated which seems to be 'Maxwellian' only very, very tenuously even by your definition and certainly not applicable to the other experiment.

Jerry
2014-Apr-15, 07:18 PM
Please provide citations as to the nature and calculation/estimation of these effects. So far all you have given is some data about how the GP-B sensors were calibrated which seems to be 'Maxwellian' only very, very tenuously even by your definition and certainly not applicable to the other experiment.



Please provide citations as to the nature and calculation/estimation of these effects. So far all you have given is some data about how the GP-B sensors were calibrated which seems to be 'Maxwellian' only very, very tenuously even by your definition and certainly not applicable to the other experiment.

To be clear, all corrections for electromagnetic effects are Maxwellian, and in the broadest sense this included hydrogen bonding and classical refractive index lensing.

The GP-B calibration corrections were made ad-hoc, after the experiment, not before; and relied upon assumptions about the nature of the anomalies: They used both 'patch effects' and a variable polhode moment. You expect a variable polhode moment in a rotting egg, but not in a carefully machined metal ball. The patch effect corrections may or may not be valid - electrostatic patches tend to be dynamic; especially near a spinning ball. All of these corrections were unanticipated; and as such they are free, uncontrolled parameters.

Once again there is NO WAY I could design an experiment to disprove a strong concept like general relativity, and then take my data and say "Well, if I correct for these patch effects and this variable Polhode moment that I did not anticipate; I get the results I was looking for; therefore, General Relativity has been disproved.

I only have sideways references for experiments that have not met expectations - papers on the Mariner 6 anomalies and other efforts to pin down gravitational lensing and such are no longer on the NASA website. A Cassini paper was archived and then withdrawn. The APOLLO (Apache Point Observatory Lunar Laser-ranging Operation) is a bust. http://physics.ucsd.edu/~tmurphy/papers/rop-llr.pdf Ok - not a bust; because they have identified systemics that limit accuracy well below the anticipated precision, just like Gravity probe-B.

tusenfem
2014-Apr-15, 07:55 PM
Okay, Jerry, if you cannot provide evidence for your assumptions, you either stop here with your claims, or you take it to ATM.
This has gone on long enough.

Strange
2014-Apr-15, 09:07 PM
I only have sideways references for experiments that have not met expectations

To be clear ... you have nothing.

Reality Check
2014-Apr-16, 12:06 AM
NASA dropped these document (and many others) when they revised the website

Your citations are to documents that do not exist, Jerry :eek:!
The one document that exists is irrelevant.
So Jerry:

Citations and clarification please, Jerry.
You seem to be saying that all tests of deflections of light by the Sun only match GR after an similar deflection by "a Maxwellian component" is subtracted.

John Mendenhall
2014-Apr-16, 01:18 AM
Well. Just for the record, OP, did you get a satisfactory answer?

Reality Check
2014-Apr-16, 02:15 AM
The GP-B calibration corrections were made ad-hoc, after the experiment, not before;...
That is incorrect as pointed out before, Jerry.

As for Gravity Probe B (http://en.wikipedia.org/wiki/Gravity_Probe_B): When unexpected signals were received due to manufacturing flaws, the data was corrected for the incorrect manufacturing:
...
The corrections were not ad-hoc - they were done using data collected for calibration.

Jerry
2014-Apr-16, 11:35 PM
To be clear ... you have nothing.
Did you even read the APS article on the Gravity B probe data?



Or http://radioscience.jpl.nasa.gov/publications/dsn.html


The 100 kW uplink was provided by the Goldstone 26-m antenna. In 1968, Goldstein (1969) duplicated the experiment with the superior conjunction of Pioneer 6 and obtained results similar to those from the Mariner 4 experiment. The radially dependent spectral broadening obtained by Goldstein and colleagues reflected the now better understood relationship between spectral broadening and integrated coronal electron density.
What happened with Pioneer 6 and Mariner 4, is that the displacement of the radio signal was much greater than expected, based upon relativity. Further studied identified the likely reason, coronal electron density; and they even came up with a a correction factor:


A substantial set of Helios and Pioneer spectral broadening data has been empirically compared to an electron density (Ne) model of the following form, where r is the radial distance and A and B are fit constants:


Ne = Ar-6 + Br-2.3

For spacecraft near solar conjunction, range measurements as a function of solar offset distance provide an excellent method of mapping electron density in the solar corona, provided all other competing effects, such as trajectory errors, unmodeled spacecraft forces, and relativistic effects can be properly accounted for.
With just a little bit of algebraic intuition, it also follows that in order to use radio waves to measure solar relativistic gravitational deflection effects, you must first correct for coronal electron density and trajectory errors caused by unmodeled spacecraft forces.

http://scienceandtechnology.jpl.nasa.gov/files/MORE-Radio%20Science%20Decadal%20White%20Paper%20091031 .pdf


In
 the
PPN 
formalism
 according
 to
Shapiro
(1967),
Will
(1971,
1993)
and
 others, 
γ
 is 
a 
measure
 of how
 much
 space 
curvature 
is 
produced
 by
 a
 unit 
rest
mass.
 
The
 theory 
of 
general
 relativity, 
where
 γ=
 1,
 predicts
 that
 a
 ray
 of 
light
 grazing
 the 
Sun
 is
 deflected
 by
 1.75
 arcsec
 and
 delayed
 in
 time
 by
 roughly 
200 
microseconds.
 Deflection
 and 
delay
 experiments 
place
 constraints 
on 
γ.
The 
best
accuracy
 measured
 to
 date
 for
 this
 parameter
 is
 2.3×10–5
 from
 the
 Cassini
 experiment
 (Bertotti et
 al.,2003)
You will find this all over the internet, including here:

http://www.universetoday.com/8919/cassini-confirms-general-relativity/

What you will not find, is the paper supporting these constraints, because it (the paper supporting the Cassini Test of Relativity was withdrawn less than six months later.

(If any one knows why, or if it was reissued, please let me know...)

Jerry
2014-Apr-16, 11:50 PM
Okay, Jerry, if you cannot provide evidence for your assumptions, you either stop here with your claims, or you take it to ATM.
This has gone on long enough.

I'm not sure what 'assumptions' I am 'defending'. All attempts to locally observe gravitational wave have indeed failed. Over the last three decades, most attempts to tighten the error bars on GR have failed, and this is certainly true of the Gravity B probe:

http://physics.aps.org/articles/v4/43

The original goal of GP-B was to measure the frame-dragging precession with an accuracy of 1%, but the problems discovered over the course of the mission dashed the initial optimism that this was possible. Although Everitt and his team were able to model the effects of the patches, they had to pay the price of the increase in error that comes from using a model with so many parameters. The experiment uncertainty quoted in the final result—roughly 20% for frame dragging—is almost totally dominated by those errors.When the goal is 1% and the result is 20% 'almost totally dominated by errors', that is a failed 650 million dollar experiment. This is not ATM; this is stymied mainstream physical theory.

Reality Check
2014-Apr-17, 12:34 AM
http://radioscience.jpl.nasa.gov/publications/dsn.html

Did you read The Deep Space Network as an Instrument for Radio Science Research (http://radioscience.jpl.nasa.gov/publications/dsn.html) and see no mention of Gravity Probe B or every existing experiment that measured the deflection of light by the Sun, Jerry?
There is some mention of GR related experiments (gravitational waves and the gravitational deflection of a polarized signal propagating through the solar corona)

Dennison et al. (1978) made further use of these results with a measurement of the gravitational deflection of a polarized signal propagating through the solar corona.

Reality Check
2014-Apr-17, 12:48 AM
When the goal is 1% and the result is 20% 'almost totally dominated by errors', that is a failed 650 million dollar experiment.
No, Jerry - that is an inaccurate, successful experiment as anyone who did not quote mine their source would see:
Viewpoint: Finally, results from Gravity Probe B (http://physics.aps.org/articles/v4/43)

The original goal of GP-B was to measure the frame-dragging precession with an accuracy of 1%, but the problems discovered over the course of the mission dashed the initial optimism that this was possible. Although Everitt and his team were able to model the effects of the patches, they had to pay the price of the increase in error that comes from using a model with so many parameters. The experiment uncertainty quoted in the final result—roughly 20% for frame dragging—is almost totally dominated by those errors. Nevertheless, after the model was applied to each rotor, all four gyros showed consistent relativistic precessions (Fig. 1, bottom). Gyro 2 was particularly “unlucky”—it had the largest uncertainties because it suffered the most resonant jumps.
(omitted text emphasized)

What Clifford M. Will is saying is that the 20% error in frame dragging was mostly caused by the sources of error discovered in the analysis during the mission and that the frame dragging still matched the prediction.

tusenfem
2014-Apr-17, 05:09 AM
I'm not sure what 'assumptions' I am 'defending'. All attempts to locally observe gravitational wave have indeed failed. Over the last three decades, most attempts to tighten the error bars on GR have failed, and this is certainly true of the Gravity B probe:



you know better than to comment on moderation in thread.
infracted

Jerry
2014-Apr-17, 05:08 PM
No, Jerry - that is an inaccurate, successful experiment as anyone who did not quote mine their source would see:
Viewpoint: Finally, results from Gravity Probe B (http://physics.aps.org/articles/v4/43)

(omitted text emphasized)

What Clifford M. Will is saying is that the 20% error in frame dragging was mostly caused by the sources of error discovered in the analysis during the mission and that the frame dragging still matched the prediction.
The patch and polhode characteristics of each gyro had to be teased out of the data, and the variable polhode moment is essentially a floating parameter, so a more proper statement is: "By adjusting the patch and polhode moments for each gyro, experimenter were able to create models that are consistent with a frame dragging moment."

But what is a variable polhode moment? They are assuming glass flow-like moments in a crystalline metal sphere; and the key word is assuming, because they did not recover the probe, and these forces were not anticipated before the fight.

It is true that during the calibration phase, they were able to model the patch effects - static electric charges that were of the same magnitude as the force that they were trying to measure. The calibration period was a short time at the end of the mission, and it is not necessarily a good assumption that in a dynamic space environment, these effects were constant. But if only patch effect corrections were needed to obtain the desired result; I would concede this was a valid test. But they were not: The variable polhode moment is an albatross.

The veracity of the proof of a theory should not be dependent on the acceptability of the theory. Again: If I proposed a test of new theory, saying how the data will be analysed, but then added something like this to the data reduction:

http://einstein.stanford.edu/content/sci_papers/papers/PhysRevLett.106.221101.pdf


Three unforeseen effects emerged, differing in detail for each gyroscope: A changing polhode path, and two patch effect torques...the two torques were a spin-to-roll misalignment of 200 to 500x larger than the predicted values from mechanical asphericity, and a "roll-polhode resonance" torque; where the roll average mentioned above would fail, making a particular gyroscope step-over, or realign, by as much as 100 mas when a high harmonic of its polhode rate came into resonance with spacecraft roll.

The daily bump in the polhode moment is unsettling, and of a high magnitude relative to the frame dragging signal being sought. The analysis is ingenious, but does not constrain frame dragging to the exacting prediction of a general relativist solution; and there is no way an experiment with this type of caveat could be used to overturn an established theory.

Ken G
2014-Apr-17, 09:42 PM
I think what you are overlooking, Jerry, is that the difference between there being frame dragging, and there not being frame dragging, is a difference that this experiment purports to being able to distinguish-- despite its problems. You are saying that had that argument been made, but the result had fallen on the "opposite side" of the question from the GR prediction, people would have doubted it, but they are fine with it since it fell on the same side. I think that is a correct rendition of what is going on-- but it is not as scientifically invalid of a conclusion as you suggest. The reason is because "no frame dragging" vs. "the frame dragging predicted by GR" are not two equivalent hypotheses-- it is easy to imagine there might be no such thing as frame dragging, but if there is, then there's no reason it should agree with GR unless GR worked, or you just got strangely lucky. So unless we are to accuse the experimenters with dishonesty, if they were underestimating their error bars, there's no reason their result (with the incorrectly small error bars) should have agreed with the GR predictions.

Bottom line: if the experimenters got their error bars right, they demonstrated that frame dragging a la GR is supported relative to no frame dragging. If they underestimated their error bars, they either cheated, lied, or got extremely lucky, to have gotten that agreement. So if we don't expect that latter result, we have a scientific conclusion based on the former.

Jerry
2014-Apr-18, 05:46 PM
We already had good evidence of frame dragging. What matters is that nagging symmetry required by GR; precisely 175mas of displacement of a star, a lambda of one.

What frame dragging tells us, is that we are pretty much right in the assumption that gravity is a tensor propagated at or near the speed of light. But if the error bars slide away from the GR prediction; there are half a hundred other ways to express tensional gravity. The latest success of MOND in correctly modeling two dwarf galaxy dynamics is stunning. This is a trick that cannot be accomplished with dark matter; and draws a line between Newtonian + Relativistic physics and real observations. http://arxiv.org/abs/1404.4049 (Mond results)

Our inability to observe gravitational waves; and the difficulty we are having 'improving' upon other 'proofs' of relativity should take us right back to the original Michealson-Morley experiments. They ruled-out a conceptual aether that flowed through space as a background medium; but not an aether that has a field strength that is a function of mass. Such a field would have many of the properties of GR, such as gravitational lensing and frame dragging; but not the locked-in fixed values derived by Einstein. Also a mass-dependent field may not release or propagate gravitational waves. That is why these null results on the gravitational wave experiments can be truly exciting.

Reality Check
2014-Apr-22, 11:52 PM
The patch and polhode characteristics of each gyro had to be teased out of the data,...

And so what has the simple fact that they adjusted for instrumental error have to do with the fact that they got results that matched the predictions, Jerry?
The veracity of this test of GR was never dependent on the acceptability of GR.

They proposed a new test of GR, saying how the data will be analyzed based on their assumptions about how the instruments would work. They detected glitches in the data due to a failure in assumptions and compensated for instrumental defects. That is how experimental physics works. That is why http://einstein.stanford.edu/content/sci_papers/papers/PhysRevLett.106.221101.pdf states

Three unforeseen effects emerged, differing in detail for each gyroscope: a changing polhode path and two patch effect torques.
Followed by a description of how the changing polhode path and patch effect torques were discovered and compensated for. At no point do they say "Hey the data does not match GR, so we will change the data"! They say that we
* detected that the polhode path changed (which they did not expect).
* detected the torques during a calibration run - which is kind of the purpose of calibration!
And the abstract:

Gravity Probe B, launched 20 April 2004, is a space experiment testing two fundamental predictions of Einstein’s theory of general relativity (GR), the geodetic and frame-dragging effects, by means of cryogenic gyroscopes in Earth orbit. Data collection started 28 August 2004 and ended 14 August 2005. Analysis of the data from all four gyroscopes results in a geodetic drift rate of 6601.8 1+/- 8:3 mas/yr and a frame-dragging drift rate of 37.2 +/- 7:2 mas/yr, to be compared with the GR predictions of 6606.1 mas/yr and 39.2 mas/yr, respectively (‘‘mas’’ is milliarcsecond; 1 mas = 4:848 109 rad).
makes it clear that the analysis of the data resulted in matches to the predictions.

One more time, Jerry: Gravity Probe B matched the predictions of GR (without changing the data to match the predictions of GR as you seem to be accusing the scientists of doing :p).

Cougar
2014-Apr-24, 07:42 PM
When theory does not agree with observation something needs to change.

Not necessarily.

If you look through the history of the attempts to detect gravitational waves, it's not too surprising that they have not yet been detected. First, it took decades of working with Einstein's equations to try to figure out what they should be looking for, or what they would expect from a particular event. This launched a whole new field of numerical relativity. I don't know if this problem has yet been solved. (I haven't finished Ferreira's book :) ) Then there is the miniscule, miniscule amount of energy that they are trying to detect. As Ferreira notes:


As the Earth orbits around the sun at a distance of 150 million kilometers, it slowly loses energy through gravitational waves and drifts closer to the sun... but the distance between the Earth and the sun shrinks at a miniscule rate.... during its whole lifetime, the Earth will drift closer to the sun by a mere millimeter.


Not a lot of energy lost there! Of course, inspiraling neutron stars will pump out considerably more energetic gravitational waves, but still, the amount of energy they're trying to detect is ridiculously small.

My question is, do gravitational waves experience any "drag," thereby reducing their energy, or complicating their waveforms, by massive bodies between the source and the observer?

William
2014-Apr-25, 10:31 AM
Not necessarily.

If you look through the history of the attempts to detect gravitational waves, it's not too surprising that they have not yet been detected. First, it took decades of working with Einstein's equations to try to figure out what they should be looking for, or what they would expect from a particular event. This launched a whole new field of numerical relativity. I don't know if this problem has yet been solved. (I haven't finished Ferreira's book :) ) Then there is the miniscule, miniscule amount of energy that they are trying to detect. As Ferreira notes:


As the Earth orbits around the sun at a distance of 150 million kilometers, it slowly loses energy through gravitational waves and drifts closer to the sun... but the distance between the Earth and the sun shrinks at a miniscule rate.... during its whole lifetime, the Earth will drift closer to the sun by a mere millimeter.


Not a lot of energy lost there! Of course, inspiraling neutron stars will pump out considerably more energetic gravitational waves, but still, the amount of energy they're trying to detect is ridiculously small.

My question is, do gravitational waves experience any "drag," thereby reducing their energy, or complicating their waveforms, by massive bodies between the source and the observer?

William:

The first line of defense of the theory in question is to confirm the measurements, to look for measurement errors or oversights, to adjust and refine models and theory assumptions to explain what is observed or in the case of this problem what is not observed. As the gravitational wave experiments' sensitivity increases there will be a point where the first line of defense is no longer scientifically justifiable. When it is no longer scientifically possible to adjust and refine models and to appropriately change model and theory assumptions, then as in chess, to avoid checkmate or a large loss of material a forced move is necessary.

The fundamental objective of science research differs from chess. The objective in science is to solve a problem, rather than to defend a theory or a model and to fight the consideration of other alternative theories. If the theory or model is incorrect, scientific progress, is blocked. In the case of this issue we must wait for the more sensitive gravitational wave experimental data, before new theories are considered.

The point of this thread is the sensitivity of the next series of gravitation wave experiments (experimental upgrade operational 2017, results 2018?) is sufficient to create a theory crisis if there are no observed gravitation waves.

Reality Check
2014-Apr-29, 04:40 AM
Not a lot of energy lost there! Of course, inspiraling neutron stars will pump out considerably more energetic gravitational waves, but still, the amount of energy they're trying to detect is ridiculously small.
The gravitational wave detection experiments are not looking for the gravitational waves from planets or even neutron stars "inspiraling". One reason being that they have already been indirectly detected(http://en.wikipedia.org/wiki/PSR_1913%2B16)!
Look at LIGO: http://en.wikipedia.org/wiki/LIGO

Measurable emissions of gravitational waves are expected from binary systems (collisions and coalescences of neutron stars or black holes), supernova of massive stars (which form neutron stars and black holes), accreting neutron stars, rotations of neutron stars with deformed crusts, and the remnants of gravitational radiation created by the birth of the universe.

Jerry
2014-Apr-30, 07:43 PM
One more time, Jerry: Gravity Probe B matched the predictions of GR (without changing the data to match the predictions of GR as you seem to be accusing the scientists of doing :p).

The gravity B probe involved two primary phases: The data collection phase, and a calibration phase at the end of the mission. During the mission; the scientists were ecstatic: There were bumps in the data, and the magnitude was a little off; but the raw curves appeared to be doing exactly what they was expected to do: capturing a 'frame dragging' moment.

When the probe enter the calibration phase, there was glaring problem: Since the probe was now free spinning, not being aligned with the reference star, the probe itself was subject to the 'frame dragging' effect; so in this 'free wheeling' the baseline residuals should be immediately subtractable from the 'frame dragging' moment. But the gyros continued to perturb, and they did so within the same magnitude that they did during the data collection phase!

At this point, or shortly thereafter, NASA quit sponsoring the data reduction, essentially saying any results derived from unanticipated experimental errors of this magnitude using ad hoc calibration techniques (that cannot be independently verified) are highly marginalized. Stanford and a private investor sponsored the final years of data reduction.

How do I know all of this? I followed the status reports at both the Stanford and NASA websites..http://einstein.stanford.edu/highlights/hlindexmain.html

http://www.nasa.gov/mission_pages/gpb/News_Collection_archive_1.html

Description of polhode effect:

http://einstein.stanford.edu/highlights/hl_polhode_story.html

It is important to know this history when you tried to evaluate the results of this 'frame dragging' experiment. It is very likely the initial 'dragging' observed was the type of patch effect described by the data reduction team. The 'variable polhode' moment is much more problematic: This is a set of spiral curves, French curves if you will, that are unique for each gyro. The 20% formal error still requires the assumption that the magnitude of the spirally correcting for each gyro is correct; even though this curve is only one of many possible solutions: The relativist assumption had to be plugged into the models in order to solve this equation.

How do I know that? The calibration phase was only at the end of the experiment. For proper control of unexpected variation, at the very least you must have calibration intervals at the start and end of the experiment. You have three new uncontrolled variables being plugged into an equation in order to solve for a fourth parameter. There is still at least one degree of freedom out there wagging its tail. Even a slight miss-modeling of the this tail can have a dramatic effect upon the over-all curve. The 20% formal error invites a wide range of possible solutions: Yes, the science team plugged in the results they were expecting and worked backwards to develop the spirograph-like curves.

Reality Check
2014-Apr-30, 09:49 PM
The gravity B probe involved two primary phases:
...more repetition of the obvious...

Yes we (you, me, everyone in this thread and anyone else capable of reading) know this, :doh:!
The facts remain simple: Gravity B probe detected frame dragging that included the predictions within the +/20% error limits.
Try reading your sources, Jerry: No "relativist assumption" was used to adjust for instrumental error that I can see.
Polhode is classical physics.
http://einstein.stanford.edu/highlights/hl_polhode_story.html

The concept of polhode motion dates back to the 18th century, when the preeminent Swiss/Russian mathematician and astronomer, Leonhard Euler, derived a set of equations that described the dynamics of rigid bodies in torque-free motion.
....
2.Herbert Goldstein. Classical Mechanics, 3rd Ed. (Addison Wesley, 2002)
(my emphasis added)

But maybe I am wrong: Please state and cite the "relativist assumption" used in the analysis that reduced the instrumental error, Jerry.

P.S. Oddly enough Gravity Probe B: Final Results of a Space Experiment to Test General Relativity (http://arxiv.org/abs/1105.3456) mentions relativity and relativity effects!
Even stranger: The equations stated in the data analysis section have no SR or GR terms in them.

Jerry
2014-May-02, 03:57 AM
Yes we (you, me, everyone in this thread and anyone else capable of reading) know this, :doh:!
The facts remain simple: Gravity B probe detected frame dragging that included the predictions within the +/20% error limits.
Try reading your sources, Jerry: No "relativist assumption" was used to adjust for instrumental error that I can see.
Polhode is classical physics.
http://einstein.stanford.edu/highlights/hl_polhode_story.html

(my emphasis added)

But maybe I am wrong: Please state and cite the "relativist assumption" used in the analysis that reduced the instrumental error, Jerry.

P.S. Oddly enough Gravity Probe B: Final Results of a Space Experiment to Test General Relativity (http://arxiv.org/abs/1105.3456) mentions relativity and relativity effects!
Even stranger: The equations stated in the data analysis section have no SR or GR terms in them.

They added three new parameters that were not defined as part of the experiment. Why did they do that? The experiment did not produce the expected result. They HAD to plug in the relativistic values in order to learn how many dimensions that they needed to add to the data reduction process in order to get the results to fall within expectations. If they could have cleaned up the data by adding a single parameter; they would have used only one new variable. How did they know that they needed three? They learned this by looking at the residuals between what they expected and what they observed - It is impossible to isolate the corrective factors necessary without this comparative process. It would have been impossible to correctly characterize the patch effects and polhode moments without evaluating the difference between what was expected, and what was observed.

Is this bad science? Not really; but there is real danger in assuming that the corrective factors developed at the very end of the test are valid when applied to the data taken at the first of the test. All of their sensing tools are aging. they are getting struck by cosmic rays. resistance values in whetstone bridges can and do change; and these are factors not even taken into account in the formal error assessment.

Polhode moments are normal, but not a varying polhode moment, at least not in solids. Again, my test asks if this type of analysis would be accepted as having any credibility if an ATM researcher said, "The experiment did not produce the stunning results we expected, but we played with the data for two years and got the numbers we were looking for; and we only had to add three new field-calibrated parameters to prove it!"

Jerry
2014-May-02, 04:07 AM
Yes we (you, me, everyone in this thread and anyone else capable of reading) know this, :doh:!
The facts remain simple: Gravity B probe detected frame dragging that included the predictions within the +/20% error limits.
Try reading your sources, Jerry: No "relativist assumption" was used to adjust for instrumental error that I can see.
Polhode is classical physics.
http://einstein.stanford.edu/highlights/hl_polhode_story.html

(my emphasis added)

But maybe I am wrong: Please state and cite the "relativist assumption" used in the analysis that reduced the instrumental error, Jerry.

P.S. Oddly enough Gravity Probe B: Final Results of a Space Experiment to Test General Relativity (http://arxiv.org/abs/1105.3456) mentions relativity and relativity effects!
Even stranger: The equations stated in the data analysis section have no SR or GR terms in them.

They added three new parameters that were not defined as part of the experiment. Why did they do that? The experiment did not produce the expected result. They HAD to plug in the relativistic values in order to learn how many dimensions that they needed to add to the data reduction process in order to get the results to fall within expectations. If they could have cleaned up the data by adding a single parameter; they would have used only one new variable. How did they know that they needed three? They learned this by looking at the residuals between what they expected and what they observed - It is impossible to isolate the corrective factors necessary without this comparative process. It is impossible to correctly characterize the patch effects and polhode moments without evaluating the difference between what was expected, and what was observed. It was an iterative process.

Is this bad science? Not really; but there is real danger in assuming that the corrective factors developed at the very end of the test are valid when applied to the data taken at the first of the test. All of their sensing tools are aging. they are getting struck by cosmic rays. resistance values in whetstone bridges can and do change; and these are factors not even taken into account in the formal error assessment.

Polhode moments are normal, but not a varying polhode moment, at least not in solids. Again, my test asks if this type of analysis would be accepted as having any credibility if an ATM researcher said, "The experiment did not produce the stunning results we expected, but we played with the data for two years and got the numbers we were looking for; and we only had to add three new field-calibrated parameters to prove it!"

Shaula
2014-May-02, 05:28 AM
However the bit you are not stating, Jerry, is that these were not free parameters that could be used to fit the data to any science model. They came up with a physically valid model of the energy dissipation and tested it against the data. It was shown to account for the vast majority of the change. The gyros also all showed the same temporal trend. So this was not a case of "Add in factors to make it work", it was a case of understanding and modelling the sensor used. So your challenge sentence is phrased badly - it should be "The experimental results were strange so we made a high fidelity model of the sensor to more accurately calibrate it. We tested the model to show it was physically reasonable as well as fitting the calibration data and used it to recalibrate the science data. The new results showed the effect as expected." - and that would be far more credible.

Jerry
2014-May-03, 05:47 PM
However the bit you are not stating, Jerry, is that these were not free parameters that could be used to fit the data to any science model. They came up with a physically valid model of the energy dissipation and tested it against the data. It was shown to account for the vast majority of the change. The gyros also all showed the same temporal trend. So this was not a case of "Add in factors to make it work", it was a case of understanding and modelling the sensor used. So your challenge sentence is phrased badly - it should be "The experimental results were strange so we made a high fidelity model of the sensor to more accurately calibrate it. We tested the model to show it was physically reasonable as well as fitting the calibration data and used it to recalibrate the science data. The new results showed the effect as expected." - and that would be far more credible.

Yes - you make a valid point, and there is fidelity in their treatment of the data; though I remain a little skeptical of the scrolling nature of the correction for the polhode moment.

Demonstrating that your result is consistent with expectations is not the same as adding to the body of supporting evidence. This is what happened with the Pioneer Ten and Eleven anomaly data. Scientists were able to model a broad combinations of unlikely but possible thermal effects that could create the observed acceleration. There was a collective sigh of relief.

But why the relief? We have a major, major major discrepancy between the observed accelerations of galaxies and clusters of galaxies and the Newtonian/Einstein predictions. More than forty years of modeling have not reduced this discrepancy and an entire cosmology has been built around this codification of 'dark matter': The difference between what we observe and what our theories predict.

I am not the only scientist that is concerned with the "pound on the data until it meshes with the theory" approach:

http://xxx.lanl.gov/abs/1404.7525


Fine-tuning is always possible in dark matter models. There are many free parameters, and we are always free to add more...The question then becomes whether the real universe operates that way. My fear is that feedback has become a modern version of the epicycle: a deus ex machina that is invoked to excuse any failing of the standard model, no matter how bizarre.

The data show the operation of a single effective force law in galaxies. There is no reason to expect this behavior with dark matter. Indeed, the combination of a thin, spiral disk of stars and gas with a quasi-spherical halo of non-baryonic CDM can in principle result in a vast variety of effective force laws. Yet from the enormous parameter space available to CDM, Nature only selects the peculiar one specific to MOND.

In the solar system, the effective force law is Newton’s inverse square law (modulo the tiny excess perturbation on the precession of Mercury’s perihelion caused by General Relativity). Everywhere we probe in the solar system, the inverse square law works perfectly. If someone were to suggest that really the solar system operates on an inverse cube law, and it merely looks like an inverse square law because there exists dark matter that is always arranged to make it look just so, would we consider this suggestion reasonable? This is the situation in galaxies, where we observe a single effective force law but attribute it to dark matter that happens to be arranged just so.

MOND is not generally regarded as a 'theory' (although some have tried to develop it into one) as a mathematical characterization that describes the behavior of matter on a galactic scale, but has not been integrated into the current cosmology. Right now, today, we have enough data to reject the current cold dark matter cosmology, and state that until we have a model of the universe that incorporateds an explanation for what is now a well-quantified force acting within galaxies, we do not have game. It is looking more and more like that theory will have to leave out gravitational waves, too.

Shaula
2014-May-03, 06:52 PM
MOND is not generally regarded as a 'theory' (although some have tried to develop it into one) as a mathematical characterization that describes the behavior of matter on a galactic scale, but has not been integrated into the current cosmology. Right now, today, we have enough data to reject the current cold dark matter cosmology, and state that until we have a model of the universe that incorporateds an explanation for what is now a well-quantified force acting within galaxies, we do not have game. It is looking more and more like that theory will have to leave out gravitational waves, too.
Except that all simple MOND-like theories have failed to match observations too. Most of the more complicated ones have too. Hence the VeS, then the TeVeS formulations. Galaxies don't act like it is a simple, one size fits all change to gravitational dynamics.

There is not much point arguing this with you though. As ever you ignore or dismiss any counterpoints that don't fit into your narrative about how science is broken by nasty dogmatic Dark matterians and Relativists holding on to untenable theory. You present the GP-B corrections unfairly, totally mischaracterising them and making it sound like an underhand attempt to force the right answer on to the data. When challenged your position is suddenly just that you are sceptical. So now it is time to pull out the Pioneer results and anything else you can throw around. Now the modelling work done for them is suddenly a jerry-rigged collection of unlikely effects. If I produce a link to their work will you switch to just being 'sceptical' about this?

Jerry
2014-May-04, 06:15 AM
So now it is time to pull out the Pioneer results and anything else you can throw around. Now the modelling work done for them is suddenly a jerry-rigged collection of unlikely effects. If I produce a link to their work will you switch to just being 'sceptical' about this?
I carefully followed Turyshev's work; because I had already tried to create a feasible thermal model myself. (I was also collaborating with one of his office peers.) I did not think that it would be possible, because the there was not a decay in the acceleration that was consistent with the half-life of the Pioneer nuclear fuel. Turyshev was able to construct a longer data trail; and demonstrate that the rate-of-change in the acceleration was consistent (within error bars) with the fuel decay. The solution is plausible, but it is not testable; and even if a solution had not been found, nobody would have accepted the Pioneer anomalies as strong enough evidence to reject current theory. The probes were not even designed for testing gravity.


Except that all simple MOND-like theories have failed to match observations too. Most of the more complicated ones have too.

Mond works with 90% of galaxies and with most obvious galaxy clusters. Nobody should expect it to work with the bullet clusters because it is such an odd duck in the first place. But the real point is, MOND should not work at all: Everywhere the MOND acceleration is observed; the galaxy, the dwarf galaxy or the galaxy cluster is not demonstrating the same acceleration laws we are observing within the solar system. Frankly, I don't know what to make of it. You can reject the MOND theories because they don't work in many instances. You should reject the dark matter theories because they don't predict the MOND behavior we observe +90% of the time and none of the dark matter candidates have been detected. Sometimes the correct answer is: We don't understand what we are observing, and give us more money so we can figure it out.

Shaula
2014-May-04, 10:05 AM
The solution is plausible, but it is not testable
I thought that you said it was improbable a short while ago? Now the problem is that it is hard to test what is 'really' going on with a probe that far away? So you have moved from an indefensible stance to an unreasonable one.


But the real point is, MOND should not work at all
That is simply not true. The majority of cases the DM distribution is fairly uniform, with a similar density profile. So of course you can fit a pseudo-force to it. Which is what you do in MOND. As I have said before on here I personally would prefer a MONDian solution but the simple fact is that as it stands the DM models, with independently (with respect to observation) cross-checked and tested parameters, have far more parsimony and predictive power than any MONDian theory has shown. DM solutions work for more systems, work for the CMBR, work for early large scale structure formation, work for nucleosynthesis and so on. So far MOND does not cover than spectrum. No matter how much you assert that there must be one out there that does, that has not been shown.

Strange
2014-May-04, 12:12 PM
and even if a solution had not been found, nobody would have accepted the Pioneer anomalies as strong enough evidence to reject current theory.

Of course not. But it has been used to test a wide range of other hypotheses and theories. For many of those it provides no support at all. Currently, it looks as is the thermal model is the best fit.

wd40
2014-May-05, 07:56 AM
What is the informed opinion of Cahill of Flinders 2014 paper "Review of Gravitational Wave Detections: Dynamical Space" (http://www.pdf-archive.com/2014/05/05/cahillgravwavereview/)?

Shaula
2014-May-05, 08:33 AM
What is the infoirmed opinion of Cahill of Flinders 2014 paper "Review of Gravitational Wave Detections: Dynamical Space"?
28 out of 53 of his citations are his own papers.
Most of his interpretations/derivations require you to accept his pet theory first.
He uses the flawed Dayton Miller experiment as a core piece of evidence without addressing the issues with it.
He uses the unpublished, unverified De Witte experiment as a core piece of evidence.
He quotes no fit quality metrics or confidences in his fits - and also fits curves that are part of his expected outcome without any evidence that he has tested other fits.
He claims, without really giving a how, to be able to avoid Einstein synchronisation and be able to measure one way speed of light.
He dismisses gravitational time dilation as being really velocity-relative-to-the-aether time dilation.
He throws out data that does not fit his hypothesis by claiming unknown effects must be hiding the 'right' answer.
He claims results where the effect is many times smaller than the error bars.
He dismisses some temporal patterns as not relevant while leaping on others as 'proof'.

Just another paper promoting his pet theory and making grand claims from little or flawed evidence and weak analytical technique.

wd40
2014-May-05, 02:00 PM
Just another paper promoting his pet theory and making grand claims from little or flawed evidence and weak analytical technique.

Sounds pretty damning.

Does the same apply to his other 2014 paper
"Gravitational Wave Experiments with Zener Diode Quantum Detectors: Fractal Dynamical Space and Universe Expansion with Inflation Epoch" (http://www.pdf-archive.com/2014/05/05/cahill-zener-2014/)?

Are standards really falling, or is this the usual fare in the gravity academe of today?

StupendousMan
2014-May-05, 04:38 PM
Are standards really falling, or is this the usual fare in the gravity academe of today?

I suggest reading the Wikipedia entry (http://en.wikipedia.org/wiki/Progress_in_Physics) for the journal in which this paper was published.

Shaula
2014-May-08, 05:14 PM
Sounds pretty damning.

Does the same apply to his other 2014 paper
"Gravitational Wave Experiments with Zener Diode Quantum Detectors: Fractal Dynamical Space and Universe Expansion with Inflation Epoch" (http://www.pdf-archive.com/2014/05/05/cahill-zener-2014/)?

Um, I hate to be unreasonable but there is no way I am going to spend my evening reviewing his papers one by one as you present them to me individually. It usually takes half an hour to an hour to read the thing and come up with some form of reasoned response. I don't think any of my criticisms of his paper require any specialist knowledge, most are either general critical thinking or can be got from ten minutes with Google. I'd suggest that if you are genuinely interested in the topic you should spend some time reviewing his papers yourself. It is not my place (or his) to tell you what to think and there are plenty of resources out there if you want to seriously apply some review techniques to his work.


Are standards really falling, or is this the usual fare in the gravity academe of today?
As StupendousMan rightly says - look at the journal this got into. Standards in the majority of serious journals are still very high. What has proliferated (thank you internet) are these pseudo-journals that offer a way to get something 'published'.

Jerry
2014-May-11, 11:54 PM
Of course not. But it has been used to test a wide range of other hypotheses and theories. For many of those it provides no support at all. Currently, it looks as is the thermal model is the best fit.That is why Turyshev's model becomes a plausible solution: Eliminate all possible solutions, and one remaining possibility, no matter how unlikely is the correct solution - according to Sherlock Holmes. The nice this about Sherlock, is he NEVER allowed a magic solution.

There is one other remaining solution to the Pioneer anomaly that does not require the 'differential space-aging' of the probe used by Turyshev: Dark Matter is widely accepted by mainstream astrophysicist on galactic scales even though forty years of scrutiny have not produced a single non-baryonic Dark Matter particle. Without the assumed differential aging used by Turyshev; this would be the one remaining solution. Why is it discounted? Because it would require layering of Dark Matter within the solar system that is inconsistent with the model for dark matter for the galaxy.

But Dark Matter could be a solution; if it were distributed into 'tufts' within our galaxy, they way it is distributed to explain the localized Dark Matter phenomenon about dwarf galaxies. This is why Mcgaugh is so highly critical of the Dark Matter solutions - there are no reasonable formulas that allow Dark Matter in all needed instances where local dynamics require either Dark Matter or invoking a new set of force laws. Dark matter is sprinkled in where it is needed; but there is no rhyme or reason for the dance.

***

There is a paper submitted a couple of days ago that hypothesizes that stars are resonantly damping gravitation waves; and this is why they have not been observed. I point out the paper, because it underlines that fact that we have greatly exceeded the sensitivities at which it was initially thought that we would observe gravitational waves. A new explanation - a 'dampening parameter' - is needed to mitigate this null result. http://arxiv.org/abs/1405.1414

Reality Check
2014-May-12, 03:49 AM
They added three new parameters that were not defined as part of the experiment Why did they do that?

The calibration of the experiment did not produce the expected result. Then you accuse them of faking the results by "HAD to plug in the relativistic values" without quoting where they did such a thing :eek:!
One more time, Jerry:

Please state and cite the "relativist assumption" used in the analysis that reduced the instrumental error, Jerry.

P.S. Oddly enough Gravity Probe B: Final Results of a Space Experiment to Test General Relativity (http://arxiv.org/abs/1105.3456) mentions relativity and relativity effects!
Even stranger: The equations stated in the data analysis section have no SR or GR terms in them.
It is almost as if you have never read the literature on the analysis of Gravity Probe B.

The term `patch e ect' [8, 9] refers to contact poten-tial di erences between crystalline or contamination re-gions on a metal surface. Prelaunch studies focused on eddy current losses and torques from interaction of the ro-tor's patch{induced electric dipole moment with support voltages and the housing dipole moment. Far more im-portant was the on-orbit discovery of forces and torques caused by interacting patches on the rotor and housing.
Put simply, rotor and housing were spherical mechani-cally; electrically, they were not.
Three unforeseen effects emerged, differing in detail for each gyroscope: a changing polhode path and two patch effect torques.

Reality Check
2014-May-12, 04:04 AM
Demonstrating that your result is consistent with expectations ....

This seems to be the sticking point, Jerry. They demonstrated that the measurements from the gyroscopes were inconsistent with expectations of measurements from the gyroscopes independent of any GR predictions and before the flight. They detected that the gyroscopes did not act as expected. That is why they had to model the unexpected results from the gyroscopes.
The analysis of that data including removing the extra source of error then gave results that matched GR thus adding to the body of supporting evidence for GR.

MOND is just a bad theory for dark matter. It gives great matches to galaxies but fails at higher scales. As for TeVeS:

Which has new problems: The Death of Dark Matter’s #1 Competitor by Ethan Siegel in Starts With A Bang! (https://medium.com/starts-with-a-bang/98edff3a066f)
Observations of a double pulsar "agrees with Einstein’s relativity at the 99.95% level (with a 0.1% uncertainty), and — here’s the big one — rules out all physically viable incarnations of Bekenstein’s TeVeS".

We do not have enough evidence to reject the current Lambda cold dark matter cosmology. There are a several details it cannot explain (e.g. dark matter cusps, Li abundance) but it remains the best model that we have. To reject Lambda-CDM we need to invalidate the evidence for the existence of dark matter and dark energy. And hopefully a theory that explains as much as it does.

Of course what we could do is throw away every single theory that exists if they do not explain everything :rolleyes:!
No gravitational waves detected - throw away GR!
Wrong deflection of light from the Sun - throw away Newtonian gravitation!
QM cannot get exact results for quarks - throw away QM!
MOND cannot explain the Bullet Cluster - throw away MOND!
CDM cannot explain galaxies yet - throw away CDM!
No evidence that neutrinos exist - throw away neutrinos (whoops they were actually found!)

Cougar
2014-May-18, 01:37 PM
DM solutions work for more systems... work for early large scale structure formation...

This is a rather major point that I've never heard MONDians talk about. Models of early structure formation using only baryonic matter simply do not reproduce the structures in the Universe that we see around us. Add dark matter to the models, and the galaxies, clusters, filaments, walls, and voids that we observe are well reproduced. I seriously doubt a MOND model would work at such an early epoch, when the mass density, and hence gravitational interactions, was much greater.

borman
2014-May-18, 02:56 PM
I consider MOND to be a particular attempt to explain the Milgrom Dynamics (MD). It is the most investigated tree in an orchard of trees spanned by MD. Call it the Modification Tree if you like. It has two main branches further subdivided into relativistic and non-relativistic branches. The first was MOND of 1983. Later Beckenstein and others developed relativistic MOND that have more generally become Einstein-Aether theories. The other less investigated branch also wants to modify Newtonian Inertia rather than Newtonian gravity. It is called MI and some nonlocal properties and path dependancies. It has the virtue of looking into stronger gravity wells to try to explain Comets, Pioneer anomaly, and flyby annomaly. I don't know how far its relativistic branch has evolved.

There have been some experimental data that is challenging this particular MOND tree. The latest report using CASSINI found no deviation from GR as regards the EFE of the non cancelled quadrupole tidal effect reaching into the stronger Solar well. This also constrains Nemesis type inerlopers as well.
This works against the modified newtonian gravity but not MI.

Experimental evidence against modified Newtonian Inertia comes from considering all three Rossetta flybys. There was a monitored anomaly for Rossetta I, but null results for Rossetta II and III. If Modified Newtonian Inertia was the answer, there remained no trace of it during the next two flybys to further alter the already altered Newtonian inertia from the earlier flyby. There were no hyperbolic flybys between Rossetta I and II to exactly miraculously restore its Newtonian Inertia to the exact value it had prior to Rossetta I.

Like Shaula, I think there may be something to MD. I, however, am becoming more disinclined to think that MOND is the right tree to persue as more constraints choke off the modify gravity or inertia approach.

Reality Check
2014-May-19, 12:08 AM
IMO, MOND became an invalid theory with the observation of the Bullet Cluster. It works great for galaxies (better than CDM) but fails at higher scales. It has no way that I know of to explain the separation of dark matter from visible matter in galaxy cluster collisions. It cannot explain the CMB power spectrum.
TeVeS has its own problems (see above).

Coming from a theoretical physics background, I like MOND and its variants. I also recognize that they do not have physical validity.

Jerry
2014-Jul-07, 10:57 PM
This is a rather major point that I've never heard MONDians talk about. Models of early structure formation using only baryonic matter simply do not reproduce the structures in the Universe that we see around us. Add dark matter to the models, and the galaxies, clusters, filaments, walls, and voids that we observe are well reproduced. I seriously doubt a MOND model would work at such an early epoch, when the mass density, and hence gravitational interactions, was much greater.
If MOND truly describes gravity, you can kiss all of the models developed to explain the current state of the universe goodbye. I know some have tried to develop a relativistic form of MONDian behavior; but Relativity is based upon an exacting equivalence between gravitational and inertial acceleration. It does not matter how well GR formulas describe behavior; if the observed behavior is found to deviate from this hard equivalence, the fundamental concept is likely wrong - we need another explanation and a new set of equations that produce the correct result.

Here is the result of the exhausting effort to identify gravitational waves using LIGO, Virgo, and IceCube:

http://arxiv.org/pdf/1407.1042.pdf Multimessenger Search for Sources of Gravitational Waves and High-Energy
Neutrinos: Results for Initial LIGO-Virgo and IceCube

To the best of my knowledge, this is the most expensive null result of a scientific experiment ever...(Unless you consider all missions to Mars searches for Martians.)


With Icecube now complete and with the construction of advanced LIGO and Virgo finishing within a year, the next generation of multi-messenger searches can commence soon, expanding our reach towards the high energy transient phenomenon.

This is a much more subdued prospective than the optimism prefacing these huge endeavors.

Reality Check
2014-Jul-08, 02:40 AM
Actually Newtonian gravity is "based upon an exacting equivalence between gravitational and inertial acceleration.", i.e. that the acceleration in F=ma is equivalent to the acceleration in F= m(GM/r^2)
GR is based on the Einstein equivalence principle (http://en.wikipedia.org/wiki/Equivalence_Principle#The_Einstein_equivalence_pri nciple)

The outcome of any local non-gravitational experiment in a freely falling laboratory is independent of the velocity of the laboratory and its location in spacetime.

I would agree that the LIGO, etc. experiments are the most expensive single result experiments that have returned a null result ($365 million in 2002 USD for LIGO). The fact remains that this is good basic science. At least they have given us an insight into the frequency of energetic events in the universe (not as frequent as we expected and so not detectable by the experiments). Remember that the chances of LIGO (http://en.wikipedia.org/wiki/LIGO) returning a result were actually estimated to be quite low - " In 2004, it was reported that theorists estimated the chances of an unambiguous direct detection by 2010 at one in six.[10]". The first phase of LIGO was more of a test of the techniques than an expectation of direct detection of gravitational waves.

Multimessenger Search for Sources of Gravitational Waves and High-Energy Neutrinos: Results for Initial LIGO-Virgo and IceCube (http://arxiv.org/abs/1407.1042) is an interesting pre-print. Events that should create gravitational waves should also create neutrinos. So look for neutrino events at IceCube and see if that LIGO-Virgo data has corresponding gravitational waves. None were found and the results give an upper limit for the occurrence of these joint events.

borman
2014-Jul-08, 09:02 PM
If MOND truly describes gravity, you can kiss all of the models developed to explain the current state of the universe goodbye. I know some have tried to develop a relativistic form of MONDian behavior; but Relativity is based upon an exacting equivalence between gravitational and inertial acceleration. It does not matter how well GR formulas describe behavior; if the observed behavior is found to deviate from this hard equivalence, the fundamental concept is likely wrong - we need another explanation and a new set of equations that produce the correct result.



It is true that the current version of MOND does not observe the SEP or strong equivalence principle while GR does. This is a source of tension that has not yet been resolved so long as MOND wants to share the same domain of application that GR does. The SEP violation seems to general enough to be part of Milgrom Dynamics and not just a particular aspect of the current MOND versions.

One possible way to extricate the tension is to consider that GR and Milgrom Dynamics operate in their own domain of application. As an example, borrowing from simple string theory concepts, suppose that GR operates on a (3+1) brane and Milgrom Dynamics operates on a (2+1) brane and we do not assume that the time dimensions point in the same direction as a general rule but continue to assume the dimensions remain orthagonal in each brane.

An analogy presents itself that the gravitational filed of GR occupies a volume while MD is located on a surface. The combination is like a volume of a lake (GR) and MD is the land under the lake. The main issue is whether the lake is completely transparent or somewhat translucent. When the depth becomes great (a>>a_0), one does not see the force from the bottom. Where the lake becomes very shallow (a<<a_0) one sees the MD acceleration. This perspective then sees that MD does not modify GR, but that GR modifies MD. Hence no EFE. GR is classical and is based upon the idea of a continuum so there is never a completely dry shore but can become infintessimaly thin. But here MD dominates but does not modify or replace GR.

If there is the a priori assumption that the GR is 100% transparent, then one would always see the bottom and the a_0 acceleration. Were this the case, Mercury would be force predicted to exhibit corrections to its perihelion over two orders of magnitude larger than actually observed. This may be one argument why Milgrom chose to try the modification tree of MOND.

There is no need to do away with GR but instead qualify or specify the equivalence principle to say that :
(3+1) gravitational and (3+1) inertial accelerations.

While (3+1) inertia remains inviolate, the same may not be true of (2+1) inertia. Where GR and MD clash or interact, usually in hyperbolic situations, there could be an exchange of (2+1) inertia where there would be no exchange of (3+1) inertia. This could have a bearing on the flyby anomalies. The classical gravity assist goes off exactly as expected, but the dot product between the (2+1)time dimensions of the earth and craft may cause a change plus or minus, independent of the gravity assist. If the time dimensions align at periapsis, no anomaly takes place. The emphasis so far by either Anderson et al or Busack has been on a spatial dimension or even a preferred frame within the (3+1) brane which leads to all manner of problems. On the larger scale of clusters, it allows the difference between the Bullet Cluster and A520. It also fixes the MOND problem of requiring additional Dark Baryons where neutrinos still do not suffice (still present in MOND as studied in the most recent Angus et al paper). It will not fix the problem of cosmological dark matter that is outside the MD purview as MD is outside the GR purview.

borman
2014-Sep-22, 08:42 PM
Where does the energy go if there is no gravitational wave energy to balance the equation?

Resonant Absorption of Gravitational Waves
Apparently Einstein considered this possibility back in 1916 where quadrupolar oscillations can absorb a portion of GW energy. This is discussed in a new Monthly Notice paper:
Stars as resonant absorbers of gravitational waves
http://mnrasl.oxfordjournals.org/content/445/1/L74.full.pdf+html
Press Release:
http://www.ras.org.uk/news-and-press/2510-finding-hints-of-gravitational-waves-in-the-stars
If gravitational waves were to be quantized, one star might consume the entire energy of the graviton.
A further consideration after their paper is whether a field of neutron stars surrounding the central SMBH sourcing GWs can be pumped up with GW energy, like population inversion, then give off stimulated emission of GW energy, similar to a laser, to give the observed energy excess near the SMBH sometimes considered to be a signal of annihilating Dark Matter Particles.

Reality Check
2014-Sep-23, 02:06 AM
It is true that the current version of MOND does not observe the SEP or strong equivalence principle while GR does.....
More of a problem is that MOND does not agree with all of the observations. Thus it is an invalid theory.

Reality Check
2014-Sep-23, 02:17 AM
Resonant Absorption of Gravitational Waves...
Yes, borman - that is a neat theoretical result which gives another technique to detect gravitational waves.
However if gravitational waves were to be quantized, one star might consume as many gravitons that it likes. A gravitational wave is not a single graviton.
No citation but: The "observed energy excess" looks like nothing to do with gravity - it is gamma ray excess that is thought to be an indictor of dark matter.

tusenfem
2014-Sep-23, 06:35 AM
Here is a story about what might have gone wrong in the data analysis: http://www.vox.com/2014/9/22/6827987/bicep2-gravitational-waves-big-bang
It could well be because there is more dust than taken into account: http://arxiv.org/pdf/1409.5738.pdf

Jerry
2014-Sep-23, 03:27 PM
Press Release:
http://www.ras.org.uk/news-and-press/2510-finding-hints-of-gravitational-waves-in-the-stars
If gravitational waves were to be quantized, one star might consume the entire energy of the graviton.
A further consideration after their paper is whether a field of neutron stars surrounding the central SMBH sourcing GWs can be pumped up with GW energy, like population inversion, then give off stimulated emission of GW energy, similar to a laser, to give the observed energy excess near the SMBH sometimes considered to be a signal of annihilating Dark Matter Particles.
Iffy. There are a lot of reasons stars flicker in magnitude. Massive flares are known to cause sun quakes; but the root cause of large flares is not known. If gravitational waves are found to be consistent with stellar brightening and yet we continue to fail to detect gravitational waves directly; then we should also look for other (non-traditional) modes of energy transfer...whatever that might be.

Jerry
2014-Sep-23, 03:30 PM
Here is a story about what might have gone wrong in the data analysis: http://www.vox.com/2014/9/22/6827987/bicep2-gravitational-waves-big-bang
It could well be because there is more dust than taken into account: http://arxiv.org/pdf/1409.5738.pdf

Here is the paper: Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes* http://arxiv.org/abs/1409.5738

borman
2014-Sep-24, 01:18 AM
Here is the paper: Planck intermediate results. XXX. The angular power spectrum of polarized dust emission at intermediate and high Galactic latitudes* http://arxiv.org/abs/1409.5738

From the paper the uncertainties are large enough, at present, that the BICEP claim is not unambiguous. More data from a clearer part of the sky may reduce the uncertainties to a point where the BICEP claim will either hold or be ever buried by the error bars. It is perhaps a bit premature to dismiss the claim until we have a better look with reduced uncertainties.

borman
2014-Sep-24, 01:54 AM
More of a problem is that MOND does not agree with all of the observations. Thus it is an invalid theory.

The theoretical systematic is most insidious of them all. None of the current theories agree with all the observations. Does this mean they are all invalid? Even GR, which has passed all solar system tests does not predict local DM, Dark Energy, nor Cosmological DM.
The underlying assumption of invalidity pressuposes that the theories are to be unversal, even beyond their domain of application, or else they are false. I would argue that it is over reaching to make this assumption and places an impossible burden on any of the current theories including GR to insist that one theory is to answer all problems. It is only cautious to, at first, see that a theory addresses the problems in its own domain of application and perhaps later see if it also can solve problems beyond its domain. If not, this is not a fault or invalidation of the theory but rather an incorrect attempt to over extend its domain of application.

I see no problem with GR as long as it is kept to its 3+1 domain. I see LCDM plus cosmological DM as an attempt to stretch GR beyond its domain of application so that it can be universal into these other domains which is unfair to GR. Current MOND and MI theories are fashioned to encroach upon the GR domain rather than belonging to their own domain which is unfair to both GR and Milgrom Dynamics.
The attempt is again to satisfy the underlying assumption or aesthetic to be universal. The quest for a universal theory may hamper our ability to consider other possibilities.

Reality Check
2014-Sep-24, 02:23 AM
The theoretical systematic is most insidious of them all. ...snipped a bit of ignorance...
No borman - in science it is the degree of matching observations that validates or invalidates a theory. There are some cases where an single observation could invalidate a theory, e.g. a high-z, blue shifted galaxy would falsify the Big Bang.
GR has passed its tests. The main thing remaining is direct detection of gravitational waves.
GR "predicts" your list of "local DM, Dark Energy, nor Cosmological DM" - these are all mass or energy and are contained in GR.
The observational evidence for DM incudes departures from Newtonian gravitation (not GR). Few (or many no one!) people use GR to predict local DM.
LCDM already includes "cosmological DM" - that is the Cold Dark Matter part.
GR is a cosmological theory so using it to explain the cosmos is not stretching it into other domains.
Fantasies about extending GR to a non 3+1 "domain" giving a better theory remain fantasies until it is done and gives better results than GR.

borman
2014-Sep-24, 02:44 AM
Yes, borman - that is a neat theoretical result which gives another technique to detect gravitational waves.
However if gravitational waves were to be quantized, one star might consume as many gravitons that it likes. A gravitational wave is not a single graviton.
No citation but: The "observed energy excess" looks like nothing to do with gravity - it is gamma ray excess that is thought to be an indictor of dark matter.

It is not just abosrption but resonant absorption. Whether gravitational waves are made of gravitons or not is still an open question. Most attempts start with noticing the other forces comply with quantum mechanics and start from a bottom-up method that starts by assuming the graviton to be the candidate for the spin two particle that otherwise created problems for the superforce theory. Historically, the quantum hypothesis resulted from a top-down problem of ultraviolet catastrophy where Planck was coerced and with imagination to consider the constant named after him as a resolution to the catastrophy. I am not yet aware of an ultraviolet catastrophy for GR that will require a Planck like solution to avoid. That is, is there a top-down need for the graviton? From the bottom-up it is rather simple and aesthetic but ultimately makes predictions that are at variance to classical GR. Is it too simple? Even though string theory, as a mathematical branch, was discovered via these early musings its validity as a separate math branch is not dependent on whether there is a graviton. The spin two particle might have a function other than as the graviton.

Whether stars can serve as capacitors to store up resonantly absorbed GW, the question is how the energy is released and what impact it may have on the local stellar environment. Microlensing for a low energy event? But are large capacitor release may create a local disturbance that could lead to gamma rays. Its a matter of how much energy in a small confined area affects the surrounding atoms. The GR lasing of neutron stars could serve as a candidate for sourcing the energy for Fermi bubbles which are not isotropic and could use a coherent source if a SMBH jet can not satisfy the conditions.

Reality Check
2014-Sep-24, 03:13 AM
It is not just abosrption but resonant absorption. ...snipped irrelevant text and fantasy....
Way to ignore physics, borman :p!
If there is a quantum theory of gravity then there will be a particle to mediate the force of gravity. That particle is called a graviton (http://en.wikipedia.org/wiki/Graviton)

In physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory.

borman
2014-Sep-24, 04:18 AM
No borman - in science it is the degree of matching observations that validates or invalidates a theory. There are some cases where an single observation could invalidate a theory, e.g. a high-z, blue shifted galaxy would falsify the Big Bang.
GR has passed its tests. The main thing remaining is direct detection of gravitational waves.
GR "predicts" your list of "local DM, Dark Energy, nor Cosmological DM" - these are all mass or energy and are contained in GR.
The observational evidence for DM incudes departures from Newtonian gravitation (not GR). Few (or many no one!) people use GR to predict local DM.
LCDM already includes "cosmological DM" - that is the Cold Dark Matter part.
GR is a cosmological theory so using it to explain the cosmos is not stretching it into other domains.
Fantasies about extending GR to a non 3+1 "domain" giving a better theory remain fantasies until it is done and gives better results than GR.

GR does not predict either of the DM, local or cosmological, nor Dark Energy. They are not derived from the equations of the 1916 theory. Yes, Einstein toyed with a lambda in a 1921 version to make the universe static, but this was an arbitrary term not derived from the original equations which he later rejected as a severe blunder. If Dark Energy was intrinsic and deriveable from the original equations, then it would be an essential part of GR and its absence would falsify the theory internally.

Most cosmologists don't say just GR but GR + LCDM. Local DM was infered in the early 1930's by Oort and Zwicky. The comological constant has been temporarily reinstalled after the discovery in 1998. But it is arbitrary and not derived from GR. Cosmological DM
was infered after the discovery of cosmological Dark Energy to help explain the S-curve. Back around z=1.86 a significant portion of Cosmological DM effectively underwent some kind of phase transition that evaporated its effect letting Dark Energy get the upper hand in the struggle between the two cosmological entities. It is not generally discussed outside cosmological circles and remains an "elephant in the living room" . It can not be the same as local DM as local energy sources do not affect ay cosmological scales.
It is internally inconsistent for DM to be simultaneously local and cosmological. Some of the early Rachel Bean papers may be of use here. In her infamous paper that gather some notoriety, cosmological DM was already an accepted concept. In at least one MOND paper by Milgrom, he clearly distinguishes between the two DMs. MOND is an attempt to explain only the local DM, while the cosmological DM he sees as a serious threat to the MOND paradigm. Here I suspect the threat is an illusion as both of the cosmological phenomena are not inverse linear but do not depend on distance and so are not of the same domain of application of Milgrom Dynamics.

Reality Check
2014-Sep-24, 04:49 AM
GR does not predict either of the DM, local or cosmological, nor Dark Energy.

That is not what I wrote, borman: GR "predicts" them (note the quotes). They are mass and energy and are described by GR.
If dark energy is a cosmological constant then GR does actually predict dark energy - intrinsically and originally. The cosmological constant is an intrinsic part of GR. It was treated as zero in general but that is just a historical accident.
LCDM is the Lambda-CDM cosmological model (http://en.wikipedia.org/wiki/Lambda-CDM_model) which includes GR.
It is internally consistent for DM to be local and cosmological because we detect it locally, cosmologically and at all scales in between. Thus this universe tells us that DM exists everywhere.
MOND remains as an invalid theory on many points, even theoretically as you pointed out, borman :eek:!

What Einstein described as his greatest blunder was the introduction of the cosmological constant (http://en.wikipedia.org/wiki/Cosmological_constant) to get a static universe. He is thought to have described this as a blunder because he did not think seriously of the other possibilities of an expanding or contracting universe. This also gave an unstable, static universe.

Reality Check
2014-Sep-24, 05:06 AM
...Back around z=1.86 a significant portion of Cosmological DM effectively underwent some kind of phase transition that evaporated its effect letting Dark Energy get the upper hand in the struggle between the two cosmological entities.
Statements about a "phase transition" and DM/DE "struggling are fantasies until backed up by citations, borman, so: Please cite your sources for this assertion, borman.

It sounds like a quite bad description of the eras of domination:
Radiation-dominated era (http://en.wikipedia.org/wiki/Radiation-dominated_era)
Matter-dominated era (http://en.wikipedia.org/wiki/Matter-dominated_era) (this is all matter including DM)
Dark-energy-dominated era (http://en.wikipedia.org/wiki/Dark-energy-dominated_era)

Strange
2014-Sep-24, 06:29 AM
GR does not predict either of the DM, local or cosmological, nor Dark Energy.

GR does not predict the existence of "normal" mass or energy. It just explains their effects. In the same way that it explains the effects of dark matter and dark energy. If it didn't, then neither dark matter nor dark energy would have been proposed as explanations of observations.

Ken G
2014-Sep-28, 03:13 AM
Exactly, theories generally don't predict the existence of things, they take the existence of things as postulates and use those postulates to predict observed behavior. I know of no theories that are capable of making predictions without some arbitrary inputs from some set of observations, and those inputs are used to predict other observations. The goal is unification of the prior observations with the future ones.

galacsi
2014-Sep-28, 11:01 AM
GR does not predict the existence of "normal" mass or energy. It just explains their effects. In the same way that it explains the effects of dark matter and dark energy. If it didn't, then neither dark matter nor dark energy would have been proposed as explanations of observations.

Local dark matter ,i.e missing visible mass has been hypothesed using GR ? I think not , only using Newton's universal gravitation theory.

Shaula
2014-Sep-28, 11:17 AM
Local dark matter ,i.e missing visible mass has been hypothesed using GR ? I think not , only using Newton's universal gravitation theory.
http://www.math.uchicago.edu/~may/VIGRE/VIGRE2010/REUPapers/Tolish.pdf - see section 6. GR reducing to Newton's laws in the static (or near static), low field strength limit. Therefore the presence of dark matter can be inferred from stellar orbits using GR as well as Newtonian methods.

borman
2014-Sep-29, 03:03 AM
Cosmological Dark Matter in the literature

Although using the search box in Google or Wiki does not produce hits, using the arXiv search box produces the red alert of over 1000 hits for either cosmological dark matter or its most common interpretation as Scalar Field Dark Matter (SFDM). The ideas are not original with me nor are they my fantasy.

I give a couple examples from the literature:
A brief Review of the Scalar Field Dark Matter model
http://arxiv.org/abs/1201.6107

From the conclusion:
“In this work, we revisit an alternative paradigm to dark
matter nature known as scalar field dark matter or Bose-
Einstein condensate dark matter model. In this model a
fundamental scalar field plays the role of dark matter in
the Universe. The hypothesis is that this scalar field undergoes
a phase transition very early in the Universe leading
to the formation of Bose-Einstein condensate drops.”

A Further Analysis of a Cosmological Model of Quintessence and Scalar Dark Matter
http://arxiv.org/abs/astro-ph/0006024
From the conclusion:
“On the other hand, we have modeled the cosmological
dark matter using another scalar field _ with a cosh
scalar potential. As we have shown in this work, the solutions
found alleviate the fine tuning problem for cold dark
matter, too. Once the scalar field _ begins to oscillate
around the minimum of its potential (2), we can recover
the evolution of a standard cold dark matter model because
the dark matter density contrast is also recovered
in the required amount.”

Milgrom’s concern that cosmological dark matter poses a serious threat to MOND:
MOND–particularly as modified inertia
http://arxiv.org/pdf/1111.1611v1.pdf
From page 5:
“The other conundrum is that we still do not have in MOND a full account
of the roles purportedly played by cosmological dark matter. There are
several relativistic MOND theories that have not yet been explored in this
context. And, in any event, we may have not zeroed in yet on the correct
relativistic MOND theory that will account for all aspects of cosmology and
structure formation.”
MOND seeks an alternative to standard cold dark matter but does not account for cosmological dark matter, unless there might be a relativistic version that can save the day.

A recent paper regarding energy “cross-talk” between the DM and DE domains:
On extended sign-changeable interactions in the dark sector
http://arxiv.org/abs/1311.3921
This past Friday there was another paper regarding SFDM now sometimes called wave dark matter:
Wave Dark Matter and the Tully-Fisher Relation
http://arxiv.org/abs/1409.7347

Reality Check
2014-Sep-29, 03:36 AM
Although using the search box in Google or Wiki does not produce hits, using the arXiv search box produces the red alert of over 1000 hits for either cosmological dark matter or its most common interpretation as Scalar Field Dark Matter (SFDM).

The new fantasy is that this Scalar Field Dark Matter (SFDM) is the most common interpretation. The standard interpretation is some unknown particle.
The SAO/NASA Astrophysics Data System (http://www.adsabs.harvard.edu/) is a better choice for searches since it is not just pre-prints.
dark matter: 58462 results
cosmological dark matter: 25485 results
dark matter particle: 15859 results
Scalar Field Dark Matter: 6951 results
SFDM: 39 results (:eek:)

P.S. The actual "fantasies" that I was talking about:

Statements about a "phase transition" and DM/DE "struggling are fantasies until backed up by citations, borman, so: Please cite your sources for this assertion, borman.

And you really need to learn the difference between a pre-print and a paper, borman. A pre-print is a proposed paper. It may or may not be published (but usually is).

01101001
2016-Feb-09, 05:38 AM
Yet another announcement of lack of progress (or maybe not): http://www.ligo.org/news/media-advisory.php


THURSDAY: SCIENTISTS TO PROVIDE UPDATE ON THE SEARCH FOR GRAVITATIONAL WAVES

[...]

(Washington, DC) -- Journalists are invited to join the National Science Foundation as it brings together the scientists from Caltech, MIT and the LIGO Scientific Collaboration (LSC) this Thursday at 10:30 a.m. at the National Press Club for a status report on the effort to detect gravitational waves - or ripples in the fabric of spacetime - using the Laser Interferometer Gravitational-wave Observatory (LIGO).

WHEN:
Thursday, Feb. 11, 2016
10:30 AM US EST

WHERE:
The National Press Club
Holeman Lounge
529 14th Street NW, 13th Floor
Washington, DC 20045

Ken G
2016-Feb-09, 02:19 PM
It is widely rumored that they will announce a 5 sigma detection on Thursday, so to say it is an "update" means they are playing their cards pretty close to their chest!

Don Alexander
2016-Feb-09, 05:57 PM
Perfect for coffee break! :D

We will have Gravity Cookies at our institute!

Also, talk about thread necroing! We do have a recent thread about the rumors regarding this announcement, you know...

Ken G
2016-Feb-10, 04:20 AM
Not in astronomy-- this is the first detection of a binary stellar-mass black hole, it's an astronomy result!

ToSeek
2016-Feb-10, 03:57 PM
It is widely rumored that they will announce a 5 sigma detection on Thursday, so to say it is an "update" means they are playing their cards pretty close to their chest!

Yes, the scuttlebutt at Goddard is that people really need to tune into this press conference. It was significant enough that the Future Exploration Science Working Group postponed a presentation on Dawn's findings at Ceres so people could watch this instead.

swampyankee
2016-Feb-10, 08:05 PM
The Michelson-Morley experiments started in about 1879; Michelson first published his results in 1881; the experiments were repeated with greater precision in 1887, and people kept testing for a total of about 4 decades (http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/mmhist.html#c1).

The moral here is that it takes much longer for negative evidence to overthrow a theory than for positive evidence to do so: GR explained the precession of Mercury's aphelion and the bending of light measured by Eddington's experiment; these were positive results which could not be explained by Newtonian gravity. Similarly, when QM was able to predict the Balmer series, QM was solid, vs speculative, even though it explained why there wasn't an ultra-violet catastrophe.

Don Alexander
2016-Feb-10, 11:16 PM
Not in astronomy-- this is the first detection of a binary stellar-mass black hole, it's an astronomy result!

http://cosmoquest.org/forum/showthread.php?159775-Gravitational-Wave-Rumors-Rumble-Social-Media

Second thread on page 2...

01101001
2016-Feb-10, 11:48 PM
Ah, I started that other thread just for the rumor. This is the substance, now, a date and time, and I really like it in this thread that seems dedicated to celebrating lack of results. The ernest protagonists in this thread always seemed to me to believe that: if you don't see something then you'll never see it. What finer place to give this notice of another update of testing results?

This upcoming update is another chance for them -- well, they who remain participants -- to crow about lack of results. They must be very much looking forward to more null results, further shaking the Foundations of Physics. I did not want them to miss this added opportunity. What fun for them!

Or not. We shall see.

Ken G
2016-Feb-11, 02:50 AM
It's not going to be a null result, I suspect gravitational waves are here. What remains to be seen is how much new astronomy will be ushered in this way, or if after a while LIGO will get kind of ho-hum.

Jens
2016-Feb-11, 03:38 PM
Yeah, they just announced they found them!

Grey
2016-Feb-11, 03:40 PM
Look like they've confirmed detection, as expected. Here (https://www.ligo.caltech.edu/detection)'s the short blurb, and here (http://www.ligo.org/news/detection-press-release.pdf)'s the full press release. So I guess there are no implications of failure to directly detect gravitational waves, since we've had success at directly detecting gravitational waves instead. ;)

Swift
2016-Feb-11, 04:01 PM
We seem to have at least two threads going in parallel about this topic (not to mention the UT relay), and so I'm going to close this thread. Please post about these developments in the new thread (http://cosmoquest.org/forum/showthread.php?159775-Gravitational-Wave-Rumors-Rumble-Social-Media).