According to Quran 31:10 :
He has created the skies without the pillars that you may see, and placed mountains on the earth, lest it shakes with you, and spread over it all kinds of creatures. And We sent down water from the heavens, and caused to grow in it every noble pair.
The sky is just the color we see. It is not a structure, or a roof over our heads. So what is the Quran referring to when it mentions, "He has created the skies without the pillars"?