Category:Redshift

This category collects work on redshift — the displacement of spectral lines toward longer wavelengths — and above all on the question of what causes it.

Almost everything the standard cosmology says about the size, age and history of the universe rests on reading redshift as recession velocity, so this is the single most consequential interpretive question in astronomy. The alternatives argued on this wiki include: intrinsic redshift, where the shift is a property of the source rather than of its motion, the position associated above all with Halton Arp and his evidence of high-redshift quasars physically associated with low-redshift galaxies; tired light, in which photons lose energy over distance; quantized redshift, the claim that redshift values cluster at preferred intervals in a way that velocity cannot explain; gravitational redshift; and propagation effects in a medium.

If any of these accounts is right for a substantial fraction of observed shifts, the distance scale and the expansion itself are called into question. See also Category:Big Bang, Category:Astronomy and Category:Cosmology.