The way the Quran describes the heavens and earth separating sounds very similar to the ancient creation myths.  It repeats incorrect ideas, it doesn’t get the order of creation right, and it doesn’t give the right timings either.  It sounds exactly like someone who is not God wrote it.

Have those who disbelieved not considered that the heavens and the earth were a joined entity, and We separated them and made from water every living thing? Then will they not believe? (21:30)

Also, which came first, the heavens or the Earth?

“He it is Who created for you all that is on earth. Then He rose over towards the heaven and made them seven heavens and He is the All-Knower of everything” (2:29)

Also, apparently the Earth took “two days” to make?

Say, “Do you indeed disbelieve in He who created the earth in two days and attribute to Him equals? That is the Lord of the worlds.” (41:9)

And all the heavens and earth in total six days?

He who created the heavens and the earth and what is between them in six days and then established Himself above the Throne – the Most Merciful, so ask about Him one well informed. (25:59)

So the Earth took two days, and everything took six days?  That sounds actually seriously wrong.  Even if you don’t take days literally, the Earth is just a tiny spec of dust in the entire universe, why would it take so long as a percentage of the total?

The Earth was not formed until around 8 billion years after the universe started.

Allah is He Who raised ( رَفَعَ) the heavens without any pillars that you can see. Then, He Istawa (rose above) the Throne. He has subjected the sun and the moon! Each running (its course) for a term appointed. He regulates all affairs, explaining the signs in detail, that you may believe with certainty in the meeting with your Lord. (13:2)

One of the most widespread motifs in creation myths is that of separation of heaven and earth.

• The Bible (Genesis) that says that in the beginning there was only water, and then God said, “Let there be a vault between the waters to separate water from water.” So God made the vault and separated the water under the vault from the water above it. And God said, “Let the water under the sky be gathered to one place, and let dry ground appear.” 
• The Greeks who said in the beginning there was only water (the God Oceanus), and then Eurynome separated the sky from the sea by dancing on the waves of OceanusG[ref]Greek creation myths[/ref]
• The Dhammai of India, The Diegenos of California – Earth and heaven had to be separated because no room for growth in the darkness otherwise
• The Romans – separation of heaven and earth by a natural force – a God
• in Ancient Greece Kronos (Time) castrated his father and separated heaven and earth, similarly with the Continental Celts
• Creation myth of the Krachi of Africa the God of heaven rests firmly on Earth and human offspring are nearly smothered, and by lots of squirming father is sent up higher and higher
• Maori and other Polynesian people said that the sky father and earth mother clung so tightly that their children had no choice but to force them apart
• The Snohomish of North Western Africa – people banging their heads against the sky so heaven and earth separated
• Melenesian Solomon Island myth
• Micromesian Mariana Islands myth
• In Mongolia Udan separates heaven and earth with 99 golden columns
• Vietnam giant Khong raises the sky from the earth with his head
• Mesoamerica the Mayan feathered serpent and the god Tepeu use their immense power to seperate heaven and earth
• and more…Reference: Creation Myths of the World: Parts I-II,  By David Adams Leeming