Getting a general picture of the timeline of physics is the first thing, right?!
Maxwell's methods then Einstein with relativity - the firm belief for classical physics, then the Hesseinberg particle physicists ...etc... with the standard particle model of modern physics. A general and thorough view might be useful to know the limits of the current problem, I think.
As for me, I am a beginner in the theory of everything, it is a bit difficult to use google translate to understand what you guys are saying but I will get used to it and be fluent because the great things happening here are worth it and I am really excited. Warm greetings to this wonderful community.
History helps with understanding but it only helps; it's not required.
For the BBT, I encourage those that want to begin their path of understanding by not looking back 13.8 billion years ago, but by starting with the universe of today. It was today's universe that helped Lemaitre recognize his theory known today as the BBT.
If you speak French, you might want to read his 1927 paper.
He put three things together to introduce the world to the first model of expansion for the universe, not of things flying through space but spacetime itself expanding.
Here are his three ingredients:
1) The data from Vesto M Slipher (Flagstaff Az), who found the first redshifts for spiral nebulae (galaxies). This was in the early 1900s.
2) Using those galaxies referenced by Slipher he determined their distance using a formula determined by Hubble.
3) He recognized that the farther a galaxy was away from us , the faster it was moving and proportionately so, as if the universe itself was expanding, contrary to the views of all others, including Einstein and de Sitter. His great knowledge of GR (General Relativity) allowed him to hypothesize that GR allowed this expansion. His French paper, after statistical messaging of the results, gave the very first expansion rate (575 kps/Mpc).
That's it. No cmbr, no early galactic morphologies, no singularity, no Inflation, etc.
But, as one might expect for a model of the entire universe and everything in it, it made many predictions.
As astronomers found evidence favoring those predictions, his theory began its path of acceptance, though there were bumps along the way, of course. It was the discovery of the cmbr that won over the majority of astronomers and cosmologist. This took about another 40 years.