Right now, there is just rebirth technically explained in this topic. I will try in next days to also try to figure out a unified theory of physics and add it to this OP.
NOTE: This will be difficult to understand without first understanding the 5 aggregate doctrine and how the world works according to the buddha, contained in the 1500 pages of “higher dhamma” found in SN chapter 2,3,4. (book of causation, book of aggregates, book of sense bases)
What is matter ? It is a field of posibillities. Think of it in this way. Think of matter like a “mathematical” set of possibilities that limits what consciousness can experience. There is consciousness, and this consciousness needs a certain field to experience things based on kamma. And this matter is the limit, it’s the thing setting the boundaries, the thing determining the possibilities that can be experienced. This consciousness, feeling, etc. need a basis, need some boundaries for what can be experienced. And this matter is the boundary itself, only that we call it “matter” and due to distorted perception do not fully understand it. Say there would be no matter, just consciousness and kamma (mental tendencies, cravings towards something). This consciousness would have boundaries for what could be experienced and those boundaries would be then called matter of course.
The thing making it hard to see this is the distorted perception of matter being solid and “the way people normally understand it”, but it’s actually a set of possibilities, a limit that determines possibilities. I don’t know how to explain it better than that, but I hope you see what I am trying to say.
Another line of thinking: Imagine someone would create a virtual world on a computer. He would put some algorithms in and just let it develop. How would it develop ? It would develop exactly like this world, it would develop around those algorihms (laws of physics).
And now we get to rebirth. Why does “consciousness descend into the womb” ? Why the need for that ? Because it needs things to make sense. It would not make sense to just pop up into a “gross” physical world such as ours (unlike deva realms with subtle bodies), it would not respect laws of physics and would not rationally make sense. (why do things “need to make sense”, check the placebo effect or the double slide experiment)
But why does it need to go there to begin with ? Why not just float in the air like it is said to happen after death (yes, there is a short bardo described in the suttas, denied in traditional theravada tradition due to risks of misunderstanding of a self existing). Well, it is due to craving that a person gets into a gross body or subtle body. Craving pulls towards something, wants to experience something within a certain realm of possibilities. And that realm/field of possibilities is determined by the body being gross or subtle. As for realms with “no body, just mind” - that is because of jhanas where there is “nonatentiveness to perceptions of matter” etc. that make there be no craving for such fields of experience, but make craving for other fields exist.
As for the unified theory of physics, that remains to be added to this topic. We know that things “need to make sense” due to the placebo effect and double slide experiment. It may be more complicated or it might really be nothing more to it than that.