"Why does MOND get any predictions right? It has had many a priori predictions come true. Why does this happen?" -- Stacy McGaugh
I say that Milgrom is the Kepler of contemporary cosmology -- on the basis of empirical evidence which now exists. Did the Gravity Probe B science seriously consider the possible implications of the many empirical successes of MOND?
According to Wikipedia, "Gravity Probe B (GP-B) was a satellite-based mission which launched on 20 April 2004 on a Delta II rocket; its aim was to measure spacetime curvature near Earth, and thereby the stress-energy tensor (which is related to the distribution and the motion of matter in space) in and near Earth. This provided a test of general relativity, gravitomagnetism and related models. The principal investigator was Francis Everitt."
"... 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.
What ensued during the data analysis phase was worthy of a detective novel. The critical clue came from the calibration tests. Here, they took advantage of residual trapped magnetic flux on the gyroscope. (The designers used superconducting lead shielding to suppress stray fields before they cooled the niobium coated gyroscopes, but no shielding is ever perfect.) This flux adds a periodic modulation to the SQUID output, which the team used to figure out the phase and polhode angle of each rotor throughout the mission. This helped them to figure out that interactions between random patches of electrostatic potential fixed to the surface of each rotor, and similar patches on the inner surface of its spherical housing, were causing the extraneous torques. In principle, the rolling spacecraft should have suppressed these effects, but they were larger than expected. The patch interactions also accounted for the "jumps": they occurred whenever a gyro's slowly decreasing polhode period crossed an integer multiple of the spacecraft roll period. What looked like a jump of the spin direction was actually a spiraling path--known to navigators as a loxodrome. The team was able to account for all these effects in a parameterized model.
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." -- Clifford M. Will
Viewpoint: Finally, results from Gravity Probe B, 31 May 2011, physics.aps.org
Are the unfortunate "interactions between random patches of electrostatic potential fixed to the surface of each rotor" merely a post-hoc explanation (which has never been confirmed by laboratory experiments on gyroscopes similar to those used by Gravity Probe B)?
I suggest that the 4 ultra-precise gyroscopes functioned correctly -- if dark-matter-compensation-constant really does equal zero then my guess is that the gyroscopes found evidence in favor of MOND-compatible-supersymmetry in the form of MOND-chameleon particles.