Will Faster Than Light (FTL) travel ever be possible? Ultimately good observations, and not theory, will decide this, but, as I discussed in a previous blog, MiHsC suggests that the usual speed of light limit of relativity is flawed because it implies a constant speed, and therefore Unruh waves larger than the Hubble scale which are not observable.
If this is true, then where in nature might MiHsC act to accelerate something past the speed of light? One way to accelerate something with MiHsC is to move it towards the spin axis of another body. The object then sees lower mutual accelerations, loses inertial mass, and momentum conservation speeds it up anomalously. This prediction fits the flyby anomalies fairly well (McCulloch, 2008, see references below). MiHsC also predicts that the flyby anomaly can be much greater for larger, slowly rotating objects. Could the anomaly be so large that MiHsC accelerates something past the speed of light in this way?
Galaxies are pretty big objects and phenomena called galactic axial jets (jets shooting out along their spin axes) have been known for years. Biretta et al. (1999) looked at a particularly interesting one in M87. They looked at recognisable ‘knots’ of light within the jet, and found that they were moving at 6 times the speed of light (6c). It is important to note that Rees (1966) showed that the apparent speed of a relativistic object moving at an angle close to the line of sight (ie: jetting towards us) can appear to be superluminal, but that this is an optical illusion. There is a simple formula to calculate the ‘real’ speed from the apparent one and the angle. According to Biretta et al (1999) the most likely angle of the M87 jet to our line of sight is 64.5 degrees, and they said that because of the observed shape of the knots “placing the jet within 20 degrees of the line of sight presents several challenges”. If we assume the best guess angle of 64.5 degrees then the implied (real) velocity is still 3.7c (the apparent one is 6c). To get the implied velocity down below the speed of light you would have to assume an angle of less than 20 degrees, which they say is unrealistic.
There are more cases like this and, in a more statistically significant study presented at the Superluminal Workshop at Jodrell Bank Observatory in 1983, and mentioned in Porcas (1983), Schilizzi showed that the galactic jets with faster than light speeds did not extend from their galaxies any less than the sublight jets did. This suggests, if they're the same length, that the FTL jets are not close to our line of sight, and that their superluminal speeds might be real. However, this raises huge theoretical problems with causality, and of course there is the possibility that something is amiss with the jet observations, but I do believe that observations, and not old textbooks, will show the way.
Introduction to MiHsC
Introduction to MiHsC
Biretta, J.A., W.B. Sparks, F. Macchetto, 1999. Hubble space telescope observations of superluminal motion in the M87 jet. Astrophysical Journal, 520, 621-626. Free pdf
McCulloch, M.E., 2008. Modelling the flyby anomalies using a modification of inertia. Mon. Not. Royal. Astro. Soc., Letters, 389 (1), L57-60. Free pdf
Porcas, Richard (1983). "Superluminal motions: Astronomers still puzzled". Nature 302 (5911): 753. doi:10.1038/302753a0
Rees, M., 1966. Appearance of relativistically expanding radio sources. Nature, 211, 5048.