150,000 gross tons coming at you! The idea of a changing speed of light sometimes meets resistance. Fortunately a greater force stands behind GM=tc^3 than cowers behind its detractors. What happens when an irresistable force meets an immovable object? The object gets squashed!
Over at Cosmic Variance yesterday was a lively discussion on the "Preposterous Universe". I started by asking "It does appear preposterous. Why should anyone like it?" That led to some thankfully intelligent replies. Comment #20 shut everyone up:
If Earth is "defined" as the centre of the Universe, you can always make a choice of reference frames so that this remains so.
Just as anyone can observe retrograde motion of planets, the CMB indicates that the Universe expanded faster than the present value of c. One must infer a repulsive inflaton field (Epicycle #1). Supernova and other data indicate that relationship v/c is accelerating, so one must infer another repulsive dark energy (Epicycle #2). We would be fortunate to live in the centre of those forces.
Varying c indeed changes observations of galaxies at z=0.5, it affects their luminosity and redshift so that they fit the curve precisely. If a prediction fits the graph of many data points, what does it mean?