@Alan
Thank you for resurrecting this thread. I have a couple of comments to make.
It's not only supernovae that generate elements. Current theory is that the merging of two neutron stars creates elements, In my view probably all elements. But in particular certain elements like thorium, gold, and uranium are only created that way.
It's my understanding that the Casimir effect imposes a frequency threshold below which electromagnetic waves cannot exist between the plates. At separations used, this generally means microwaves can not exist between the plates. However, microwaves exist in abundance outside of the plates in the form of the cosmic background microwave radiation (CBMR). While the energy density of the CBMR is low it has the perfect form to account for observed effects, as the field has no point source. Therefore no matter how you orient the plates you get the same effects. No ZPE needed to account for the effects.🤠