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.

Modern scientific theories, aside from the BBT, are on pretty solid ground.

There are no gaping holes/gross inconsistancies in other astrophysical theories. The BBT is the only "generally accepted" scientific theory mired "up to here" in ad-hoc conjecture, failed predictions and custom-made laws of physics, so it is the only one enjoying a bumber-crop of alternatives...some of which are not half-bad.

This is quite a bold statement. Is it true? Is the BBT the dodgiest of all current scientific theories? This is OT so if you have any justification for the statement, Peter, it's probably best if you present it in a new thread.

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This is a pretty fascinating claim, because I see the evidence for the big bang as having many effects on other theories. For example, what about redshifts? If redshifts are in fact a measure of recession, then we have solid evidence that galaxies are getting further apart, i.e., the universe is expanding. But if the redshifts we observe have some other source, that means that all our measurements of velocity in the universe are suspect, which has a pretty dramatic effect on all kinds of astrophysical theories. Which is it?

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Interpretation of the redshift in BBT led to some extraordinary properties of the quasars (energy output) which in turn led to model of the AGN as
a supermassive black hole in the center of a galaxy.

And just there I will point to an alternative astrophysics theory with a good theoretical foundation:
What in mainstream astrophysics is Black Hole in some scientists view is
MECO object, inferred from solutions to GR equations, found in 2003.
here
here
here

proponents : Abhaz Mitra, Stanley Robertson

p.s. and I think it's very good

Modified Newtonian Dynamics (MOND), kicked off by Moti Milgrom in 1983*, is the subject of an impressive number of papers.

Its track record wrt the rotation curves of spiral galaxies is particularly impressive.

However, right from the get-go, MOND was seen as having some serious short-comings, both theoretical (e.g. it is incompatible with relativity) and observational (e.g. cluster motions).

Several attempts were made to extend MOND, to address the theoretical short-comings. Perhaps the most well-known extension (if it can be called that) is Bekenstein's TeVeS, see here for a primer.

While I am not a fan of MOND, or TeVeS, if anyone would like to ask about the extent to which either of these match good, relevant astronomical observations, I'd be happy to try to answer.

* Milgrom, 1983

But the BBT is a theory that attempts to explain redshift! So any other theory of redshift is an anti-BB theory, and this thread is about non-anti-BB ATMs...or so I was led to believe by the OP.

As an example, take the electric-sun thread. The electric-sun theory is non-anti-BB. However, the mainstream theory that the sun is powered by nuclear energy is on "pretty solid ground," so the electric-sun thread is probably not going very far. By contrast, the theory that the expansion of the cosmos was powered by Inflation (thus explaining the redshift), is is on shakey ground. And that soft earth is fertile ground for alternate theories.

Alternate theories--outside the BB--are like weeds trying to grow in granite.

No, what I mean is, if we decide the big bang is wrong, and redshifts are not a measure of expansion, but are instead caused by something other than recession, that would have sweeping effects on many astrophysical observations. I don't see how the big bang could be false, but all other astrophysical theories would remain essentially unchanged. That doesn't mean that big bang theories must be true, but changing it would have fairly sweeping effects.

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Conserve energy. Commute with the Hamiltonian.