Yes. My only contention here is that they do not say that big bang started all those universes.
Regards,
Anoop
I found something for you. Hope this interests you
Most of the (scientific) answers you've been given so far are great descriptions of the moment OF the Big Bang, based off the 'Cosmic Egg' model (which also handily appeared as a metaphysical speculation thousands of years ago in India).
Obviously, time and space take on a new meaning in a Universe which exists relative to them. But I presume you are more curious about how such a relation between the Universe, space and time could come into existence without already existing in some way.
While nobody can say for sure, the most interesting theory I've heard comes out of String Theory, and sort of does a tricky reductionism of sorts, and should be held as suspect as all theoretical physics, but basically goes as follows: There are multiple dimensions which exist (somewhere between 10 and 29) and all exist not as 'places' but as forces and/or extended objects. So, essentially, consider the dimensions we are familiar with (3 spatial directions and time) and how these things 'exist' independent of the world in which they appear. It's difficult, if not impossible to authentically do; in fact, some philosophers (Kant, notably) suggested that these were basic categories of apprehension, without which consciousness could not exist at all.
Which is a roundabout way of saying that there are 10 to 29 dimensions, and our carbon-based brains are limited in comprehending in any meaningful way what those dimensions may actually be.
Nonetheless--- by inference and mathematics which far exceed anything I could actually explain, physicists have argued that the 4 dimensions which we are aware of cannot be explained in and of themselves, and require 'extra dimensions' to make sense of them.
The dimensions are supposed to exist in the aforementioned 'extended objects' which can be mapped out mathematically, and is referred to as a D-brane. It has been proposed that D-branes are themselves 'vibratory rates' of super strings, which are yet another kind of dimension stretched in an infinite linear plane.
I know, it all sounds pretty #$%ed up. But just wait...
The Big Bang supposedly happened when (for reasons which are themselves unknown) two D-branes/dimensions/superstrings 'collided', and the resulting 'collision of dimensions' resulted in what we lovingly refer to as 'the Big Bang'.
Part of this theory implies that Universes get created all the time, and that there are a possibly infinite number of 'bubble universes'. I personally consider it a bit of hopeful and imaginative speculation which is more fantastical that firmly planted in 'firm' science... but most theories seem so until they get refined.
So; our Universe is basically a subset of a much larger organization of dimensions, and when these dimensions collide, they incite new Universes.
It's possible that different collisions of different dimensions would create wholly different kinds of 'Universes'--- some where time or space operate differently, for instance.
I'd recommend reading up on D-branes and string theory to get a better explanation of all this than I've probably provided. But for now, that's the most up-to-date explanation of the Big Bang's inception that I'm aware of.