Translation of the verse 12 from Surah An-Naba’ : Number of verses 40 - - page 582 - Part 30.
And We have built above you seven strong (heavens),
And constructed above you seven strong [heavens]
(78:12) and built above you seven strong firmaments, *9
*9) "Strong" in the sense that their boundaries are so strongly fortified that no change whatever occurs in them, nor does any of the countless stars and planets in the heavens, violating these boundaries, collide with the other, nor falls down to the earth. (For further explanation, see E.N. 34 of Al-Baqarah, E.N. 2 of Ar Ra'd, E.N.'s 8, 12 of Al-Hijr, E.N. 15 of AI-Mu'minun, E.N. 13 of Luqman, E.N. 37 of Ya Sin, E.N.'s 5, 6 of As-Saaffat, E.N. 90 of Al-Mu'min, E.N.'s 7, 8 of Surah Qaf).
Source : An-Naba’ Verse 12: And constructed above you seven strong [heavens]