I came across Ned Wright's webpage http://www.astro.ucla.edu/~wright/tiredlit.htm which states that alternative explanations for the redshift of galaxies would not be consistent with the z-dependence of supernova lightcurves. However, this assertion is not further substantiated and as far as I can see any wavelength independent redshift mechanism should indeed result in the change of the supernova lightcurves: Consider a sinusoidal lightwave modulated by a lightcurve L(t), i.e. E(f,t)=E0*sin(f*t)*L(t) . By expanding L(t) into a Fourier Integral i.e. L(t)= Int[dF*cos(F*t)*a(F)] and drawing the sine function under the integral one gets E(f,t)=E0* Int[dF*sin(f*t)*cos(F*t)*a(F)]. Using the addition theorems for trigonometric functions, this is equivalent to (apart from a constant factor) E(f,t)=E0* Int[dF*(sin((f+F)*t) + sin((f-F)*t)*a(F)]. Applying now a redshift factor (1+z) changes the frequencies to (f+F)/(1+z) and (f-F)/(1+z), i.e. the signal becomes E(f,t,z)=E0* Int[dF*(sin((f+F)/(1+z)*t) + sin((f-F)/(1+z)*t) *a(F)], and by reversing the addition theorem and taking the sine- function out of the integral again E(f,t,z)=E0* Int[dF*sin(f/(1+z)*t)*cos(F/(1+z)*t)*a(F)] = = E0*sin(f/(1+z)*t)* Int[dF*cos(F/(1+z)*t)*a(F)] = = E0*sin(f/(1+z)*t)*L(t/(1+z)). This means that not only is the wave frequency redshifted but also the light curve broadened. For anyone intererested, I have myself suggested that the redshift of galaxies is in fact caused by the small scale electric field due to the intergalactic plasma (a kind of counter-part to the Faraday -rotation in a magnetic field) (for more details see http://www.plasmaphysics.org.uk/research/#A11).