Is the big bang theory provides adequate explanation for the formation of the universe?

Answer 1

Depends on what you mean by "formation."

Big Bang Cosmology (BBC) is the ONLY cosmology that explains what we actually observe about our Universe -- Hubble Expansion, cosmic microwave background radiation, ratio of decay isotopes to "parent" isotopes, etc. Proponents of all other cosmologies are forced to say, "I have no idea why we observe what we do -- it's just the way the Universe is, and I have no explanation for it."

However, BBC states ONLY that our total Universe was, about 13.8 billion years ago, infinitely more dense (note: NOT smaller!!) than it is today, and that space has been expanding ever since at a (more or less) uniform rate. It makes NO statement WHATSOEVER on what occurred prior to the start of this expansion (more precisely, after the end of Inflation). Scientists speculate on what occurred, but (as of now) there is no observational evidence to prefer one idea over another.

So, BBC is not only an adequate explanation for the formation and development of our Universe since the end of Inflation, it's the ONLY explanation that fits what we observe. However, it is not an explanation for what happened before then, and makes no pretense about doing so.