All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The verse in Surat Qaaf [Quran 50], which is the Saying of Allah (which means): {Have they not looked at the heaven above them - how We structured it and adorned it and [how] it has no rifts?} [Quran 50:6]; the meaning of {it has no rifts} is that it does not have any cracks. This verse neither mentions the closeness of the heaven, its farness, its shape nor its dimension; rather, this verse calls upon people to look at the heaven, which is one of the signs of Allah that indicates His Great Power and Might.
Looking at something does not necessary mean that it is very close; we see the stars and the planets, while they are very far from us, and the Prophet described the planets to be very far and distant in his saying: "The dwellers of Paradise will look at those in the upper abodes above them just as you see the distant shining planets ..." [Al-Bukhaari and Muslim]
The Prophet described the planets in the sky as being distant and far.
The Quran did not state that the sky is in the form of a dome, but it is described as a ceiling and a canopy and that it has a structure, which is well-structured and firmly constructed. Allah Says (what means):
• {It is Allah who made for you the earth a place of settlement and the sky a ceiling and formed you and perfected your forms and provided you with good things.} [Quran 40:64]
• {And We made the sky a protected ceiling.} [Quran 21:32]
• {And [by] the roof raised high.} [Quran 52:5]
The roof in the last verse refers to the heaven, because the earth is like the roof for the house.
As for the fact that the sky is circular or like a dome, then this is taken from other pieces of evidence. If the earth is round, as per the agreement of the scholars, and since the heaven surrounds it from every side, without any difference of opinion amongst the scholars, then this would imply that the heaven is also circular.
As far as we know, Shaykh Ibn Taymiyyah did not say that the lower heaven is like a dome, which is half of a circle; rather, he rather stated that it is circular, as he said: "Know that the scholars agreed that the Earth is round-shaped. [..] If the first heaven above the earth surrounds it, then the second heaven is also round, and likewise would be the case of all other heavens. [..] The orbits are circular as stated in the Book (Quran), the Sunnah and the consensus of the scholars. The word Falak (orbit) means that it is round. Allah Says (what means): {…but each, in an orbit, is floating.} [Quran 36:40]" [End of quote]
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Allah knows best.