[somenameforme]

I think you're leaving out a major issue there. Homogeneity was not in favor of the big bang. It's actually a major problem - the horizon problem. [1] Parts of the universe (think opposite sides) are not causally connected. Even traveling at the speed of light, there would not be enough time for a particle in one side to reach the other since the birth of the universe. Yet the temperature within these regions is homogeneous - at a thermal equilibrium. That doesn't make any sense.

This led to the development of cosmic inflation [2], which is what largely drove me from a doe eyed young astronomy enthusiast to a highly skeptical old fart. It solves the problem in an ad hoc fashion. Just have the universal expansion go into overdrive for a bit shortly after the big bang, then slow down, then start accelerating again - and then at the end we finally get something that looks like what we see - a homogeneous system in this case.

It made some highly accurate and improbable predictions which led to widespread adoption but then ran into numerous issues requiring further ad-hoc solutions. And this process has been repeated multiple times since its original formulation, to the point that there's a library of different inflation theories now a days, all getting ever more fine-tuned. If non-casually connected regions of space acted like they were non-casually connected then all would be fine, but the homogeneity that we do have is a big problem for the big bang.

[1] - https://en.wikipedia.org/wiki/Horizon_problem

[2] - https://en.wikipedia.org/wiki/Cosmic_inflation

[wwind123]

I kind of understand your frustration about the ad-hoc nature of the Inflation theory. When I was younger I believed the truth must be simple and beautiful - if a theory is complex and ugly then it's not the real truth. But as I get older, now I think the universe is what it is. Things may or may not have a simple or elegant explanation. Theories exist to explain things and make predictions. As long they serve both purposes well, then they are the working theories.

[somenameforme]

It's not just the ad hoc nature of the hypothesis itself, but also the subsequent ad hoc retrofits and fine tuning. With enough unconstrained fine tuning you can create a signal from noise, even when no signal exists. Take for instance the geocentric universe. Ptolemy's model was completely wrong in numerous ways beyond just assuming everything revolved around the Earth, but it was sufficient to make highly accurate predictions by excessively fine tuning the model to fit observations. And as new observations contradicted the model, all you needed to do was just add more epicycles to also make them fit.

Those retrofits (or the results they explained at least) were then were used as arguments in favor of the model, which is completely nonsensical and backwards. I think the most fundamental factor in good science is falsifiability. But if we just engage in and accept ad-hoc retrofits, then models become completely unfalsifiable. And at that point, what does science even mean?

[Tazerenix]

Yep, no doubt there are definitely issues with inflation. My main point is that the size of black holes in the early universe is largely orthogonal to the whole big bang/inflation debate. Even if the model changes, the lack of IMBH evidence means that any universal history model must have some kind of time asymmetry.