Here is an alternative suggestion for imagining the big bang. Rather than an explosion, think of space as unfolding at the Planck Scale everywhere at once. I know, not easy to visualize. Imagine a plane, it’s easier to think in two dimensions, then you just extrapolate to three. First there is nothing. Then at some event (call it the big bang if you like) space (or dimensionality) pops into existence everywhere at once, unfolding at the Planck Scale, and expanding at the speed of light.
Though I prefer Variable Speed of Light, when the universe was “denser” the speed of light was higher than it is now. Maybe! :^). :^). As the density of space-gravity (as opposed to space time) decreased, the speed of light slowed down.
Time is an illusion, I have always suspected that time is not real at all, I’m not sure why. My best guesstimate of why we think we perceive time, is that this is how the human brain rationalizes gravity. Either there is time, or there is gravity. Not both. Gravity is less problematic than time. Time is not necessary. One can formulate a perfectly rational model of the universe that, conforms to the Correspondence Principle, if you replace “time” with “sequence and causality.”
Sequence simply means that things happen in a fixed order, like on a number line. Item one, follows item two, follows item three,…. and so on.
Causality is just the notion that one thing can cause another thing to happen. You push on a rock at the top of a hill, which causes the rock to start rolling down the hill. “A” caused “B”
If you have a universe with both sequence and causality, you do not need time.