It is not a concept but a fact to believe that Allah created every thing in the universe including skies, earths, stars, planets and galaxies. Seven skies created by Allah (SWT) are mentioned in Quran in many verses (2:29 and 41:12 and 65:12 and 67:3 and 71:15). Allah, The Glorious has created the color spectrum as seven and layers of the earth as seven and many other phenomena in this universe in seven. He knows the wisdom behind it and we are unable to understand it due to our limited thinking abilities. We believe in His Absolute Wisdom, Absolute Knowledge, and Absolute Mercy and we have no doubt that every thing He creates is based on full wisdom.