the universe is not expanding into anything it is simply expanding, diverging
there is no separation
duality is inherently a contradiction
but what is created through divergence is eventually voided through convergence and like a dragon eating its tail this is the most fundamental cycle of cosmic mechanics.
Two fundamental ether modalities magnetism and dielectricity make up the entire universe
the expansion/divergence/creation/magnetism is balanced by contraction/convergence/voidance/dielectricity
This is the yin and yang of cosmic mechanics
Through pressure mediation they form a golden ration torus/hyperboloid of magnetodielectricy.
Gravity is incoherent dielectricity.
The divergence follows the torus and the convergence doesnt really exist because it's a voidance but the path it follows is a hyperboloid.
Search "Theoria Apophasis Field Theory" on Youtube