The Skies

We are told that the skies were built. In S 50:6 we read: So have they not looked at the sky above them, how we have built it and adorned it and it has no cracks?

S 51:47 And the sky, we built it with strength and we are able.

S 78:12 And we built above you seven strong.

S 91:5 By the sky and what built it,

S 79:27 Are you a harder creation or is the sky that he built?

We read in Ibn Kathir:

Creating the Heavens and the Earth is more difficult than repeating Creation in refutation of the claim rejecting resurrection due to the renewal of creation after its original state, Allah says;ءَأَنتُمْ(Are you) `O people'أَشَدُّ خَلْقاً أَمِ السَّمَآءُ(more difficult to create or is the heaven...) meaning, `rather the heaven is more difficult to create than you.' As Allah said;لَخَلْقُ السَّمَـوَتِ وَالاٌّرْضِ أَكْـبَرُ مِنْ خَلْقِ النَّاسِ(the creation of the heavens and the earth is greater than the creation of mankind;) https://quranx.com/Tafsir/Kathir/79.27

The (lowest) sky has no cracks. S 50:6 above,

S 67:3 The one who created seven skies in levels. You do not see any disparity in Al-Rahman’s creation. So return the eyesight. Do you see any cracks?

In S 69:16 we read of that sky's cracking: And the sky has split and it is on that day fragile. See also:

S 82:1 When the sky is cracked

The skies are held up by means of invisible columns. S 13:2 Allah is the one who raised the skies without columns that you see. Then he ascended the throne and subjected the sun and the moon, each running for a fixed term. He arranges the matter, he details the signs; perhaps you will be certain of the meeting of your lord.

The lowest sky is where the stars are located (!)

S 41:12 So he finished them as seven skies in two days and inspired in every sky its affair. And we adorned the lowest sky with lamps and as a defence. That is the determination of the mighty, the learned.

S 67:5 And we adorned the lowest sky with lamps and made them missiles for the devils and prepared for them the torture of the blaze.

The skies, seven in number, are solid structures that have been built and have no cracks, at least not yet, the stars located in the lowest, which are held up by means of invisible columns.

In the Talmud we read of seven firmaments.

Reish Lakish said: There are seven firmaments, and they are as follows: Vilon, Rakia, Sheḥakim, Zevul, Ma’on, Makhon, and Aravot. The Gemara proceeds to explain the role of each firmament: Vilon, curtain, is the firmament that does not contain anything, but enters at morning and departs in the evening, and renews the act of Creation daily, as it is stated: “Who stretches out the heavens as a curtain [Vilon], and spreads them out as a tent to dwell in” (Isaiah 40:22). Rakia, firmament, is the one in which the sun, moon, stars, and zodiac signs are fixed, as it is stated: “And God set them in the firmament [Rakia] of the heaven” (Genesis 1:17). Sheḥakim, heights, is the one in which mills stand and grind manna for the righteous, as it is stated: “And He commanded the heights [Sheḥakim] above, and opened the doors of heaven; and He caused manna to rain upon them for food, and gave them of the corn of heaven” (Psalms 78:23–24). Chagigah 12b:5

Further reading:

The Built Sky

Oh, That's Hard!

It Gets Easier With Practice