After mentioning the confused state of the infidels, Allah draws man's attention to His infinite power which He demonstrated by creating what is bigger than that which they wondered about and whose possibility they discounted. Referring to the heaven, the Qur'an says: وَمَا لَهَا مِن فُرُ‌وجٍ (...and it has no cracks...50:6). Lexically, the word furuj is the plural of farj which means a crack, or an opening. This and the following few verses draw attention to the marvels of Allah's creation, the wonderful design in the universe, and to the flawless celestial firmament. If this was made by man there would have been patches, cracks, clefts or rifts. But no one can find any sort of patchwork or stitching in the sky. This, however, does not negate the existence of doors in the heaven. A door is not referred to as a crack: