Firmament

In Ancient Near Eastern cosmology, the firmament was a celestial barrier that separated the Heavenly waters above from the Earth below. In Biblical cosmology, the firmament (Hebrew: רָקִ֫יעַ‎ rāqīaʿ) was the vast solid dome created by God during the Genesis creation narrative to separate the primal sea into upper and lower portions so that the dry land could appear. The concept was adopted into the subsequent Classical and Medieval models of heavenly spheres, but was dropped with advances in astronomy in the 16th and 17th centuries. Today the word is sometimes used as a synonym for the sky or for heaven.