This question has nothing to do with the expansion of space or the speed of the expansion. I do understand that space expansion is not constrained by the speed of light limit, but I am not asking about expansion.
I am not asking about the fabric of spacetime, what it is made of, or how it stretches.
I have read this question:
where Allure says:
No physical thing can travel faster than light, but the universe can still expand faster than light because it's not physical.
I would like to disagree.
The physical Universe is defined as all of space and time[a] (collectively referred to as spacetime) and their contents.
I do believe that spacetime itself is a physical thing, and all the events it is made out of are. Vacuum, as we define it, itself is physical too.
There are a few reasons why I believe spacetime itself is a physical thing:
1. Vacuum can produce particle antiparticle pairs. If spacetime itself was not physical, then how would it be able to produce particle antiparticle pairs?
2. Spacetime itself can bend (and expand too), how could it if it was not a physical thing?
3. Spacetime itself includes all events too.
4. It includes all the fields, for all forces, particles, and particles are just excitations of these fields, that are an intrinsic property of spacetime itself. How could spacetime not be physical if it includes the fields too (that manifest as excitations in matter and energy itself)?
- Is spacetime physical?