Even Carl Sagan failed.
A correct explanation of the universe may require a knowledge of the Russian language.
A successful explanation requires a knowledge of how to obtain taxpayer or believer support.

The big bang is a modern scientific creation myth. See video at 2 minutes 49 seconds.

We think of Time as having a beginning, a past, a present and a future. Maybe it's just Time. It's just part of the universe. So thinking of a beginning is just something we do because we perceive time as something that goes from the past and on in to the future. Maybe it's just Time and the beginning and the end of time is just how we perceive it.

Could the real expansion, red shift, etc merely be manifestations of something more basic?
Namely, a shift in the value of C. (The speed of light.)

What intrigues me is the future of the universe. If the universe is sufficiently massive, then the expansion will eventually halt and the universe will shift into reverse gear and begin contracting, leading ultimately to a Big Crunch. The universe at the end of the Big Crunch may presumably be in the same collapsed state it was in before the Big Bang. This begs the question, would the crunched universe then explode in another Big Bang and perhaps oscillate back and forth from Big Bang to Big Crunch?

An infinitely oscillating or cycling series of universes suggests that you and I may have existed in a previous cycle (a previous incarnation of the universe), and we may exist again in future cycles of the universe. There is no reason to assume we'd have any memory of past incarnations. Our consciousness or spirit may be discontinuous, ended if not by death (as I believe), then by the Big Crunch. But even trillions of years would seem a blink of the eye if you are not conscious during the interval. Of course, there may be zillions of cycles that don't include you or me. But if the cycling goes on (and has gone on) infinitely, you can still have an endless number of reincarnations. And you will have more frequent reincarnations if you count the cycles when, for example, you have one more eyelash than you do now, one less eyelash, two more eyelashes, green eyes instead of brown, a clockwise whorl in your fingerprint instead of counterclockwise …

That's if the universe is sufficiently massive. According to the last astronomical measurement I heard about, it is not massive enough to stop expanding forever. A forever-expanding universe dissipates into a cold, lonely, virtual vacuum. I don't think the final verdict is in on this question, but I haven't kept up with the latest.