Yeah, watching the movie again, Celestials only create Stars. One thing has been bugging me and that’s how we treat the scene that “Looks” like they’re creating Galaxies. Stars are created from a collection of Dust and Hydrogen being compressed until Nuclear Fusion Kicks in. The scenes that look like “Galaxies” being created are equally as valid for just Star creation. Arishem himself states:
“Our universe is a constant exchange of energy. An infinite cycle of creation and destruction. Celestials use energy gathered from host planets to create suns, generating gravity, heat and light for new Galaxies to Form. Without us, our Universe will Fall into Darkness.”
Even in other material, it states the Celestials Created the “Building Blocks” for Life which, everyone commonly knows as Gravity being the Corner Stone and the Opening Crawl in Eternals states Arishem created the first Sun, which leads to the creation of everything in existence but its via chain reaction.
First Sun introduces Gravity > Gravity Causes more Stars to Form > Planets and Solar Systems are created from the gravity of Stars > Life is possible in Goldie Lock Zones where heat and is just right to allow for Water to form (Not necessarily the case across fiction), etc etc.
I think only Arishem should “Possibly” Scale to the Big Bang but that’s it.