Firmament different from celestial sphere
In biblical cosmology, the firmament is the vast solid dome created by God during the Genesis creation narrative to divide the primal sea into upper and lower portions so that the dry land could appear. The concept was adopted into the subsequent Classical/Medieval model of heavenly spheres, but was dropped with advances in astronomy in the 16th and 17th centuries. Today it survives as a synonym for "sky" or "heaven".
not same as not identical to distinct from separate from unlike