﴿ وَجَعَلْنَا ٱلسَّمَآءَ سَقْفًۭا مَّحْفُوظًۭا ۖ وَهُمْ عَنْ ءَايَٰتِهَا مُعْرِضُونَ ﴾

“and [that] We have set up the sky as a canopy well-secured? And yet, they stubbornly turn away from [all] the signs of this [creation],”

Please check ayah 21:33 for complete tafsir.