The Hebrew word is raqia , signifying 'expanse.' It is used for the celestial sphere that may be seen by looking upward, and also simply for the atmosphere in which the birds fly. We read that God called the firmament 'heaven:' this is 'heaven' in a broad sense as we read elsewhere of 'the stars of heaven,' but also of 'the birds of heaven.' Genesis 1:6-20 . The Psalmist speaks of them as distinct: "The heavens declare the glory of God; and the firmament showeth his handywork." Psalm 19:1; Psalm 150:1 . The living creatures in Ezekiel 1 move amidst the firmament: "and the likeness of the firmament upon the heads of the living creature was as the colour of the terrible crystal, stretched forth over their heads above" ( Ezekiel 1:22 ), showing them to be executors of God's judicial government: cf. Ezekiel 10:1 .