Think of this as a thread similar to How good are the best alternatives to the Big Bang theories?

But with a different scope - stars, the interstellar medium (gas, dust clouds), clusters, galaxies, globular clusters, clusters of galaxies ... but not planets, solar systems, asteroids, moons, comets etc.

Another difference: instead of five broad categories of observations, let's take any (and all) relevant astronomical observations - the detection of photons, of any wavelength and polarisation; the detection of neutrinos from SN1987; the detection of 'galactic' cosmic rays.

I am stressing observations, not interpretations. For example, in an alternative theory of astrophysics, strong gravitational lensing like this may be the result of something quite different than a concentration of dark, non-baryonic matter in rich clusters; the challenge to any such alternative astrophysics theory would be to match the observations (by the HST, in the case of Abell 2218).

Once again, this thread is NOT about how well, or how poorly, any mainstream astrophysics theory does, or does not, match any good astronomical observations. This thread is about which alternative astrophysics theory fits these astronomical observations best.

While speculation is interesting (e.g. "I reckon that {Y} theory can account for all the data very well, but I've neither read any papers showing the match, nor done any work myself to check"), I am really interested only in demonstrable matches. So, for example, if you think {Y} ATM astrophysics theory can match the HST Abell 2218 data well, then be prepared to either show that yourself, or point to a paper (or similar) which can.

Finally, the ATM theories I am interested in discussing in this thread are scientific theories. Explicitly, empirical relationships - such as those under active discussion in the More from Arp et al. thread - are beyond the scope of this thread. Also, to avoid duplicating active discussions, the Arp-Narlikar Variable Mass Hypothesis is beyond the scope of this thread.