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?

Previous generations of commentators have not fully known how to interpret this line.  Many modern commentators hold that it is a clear reference to the Big Bang theory, which asserts that all matter, including the earth, was once fused together in a compact unit that suddenly split apart, eventually resulting in the galaxies, planets, stars and other heavenly bodies over billions of years.  This is a plausible interpretation as the plural word samawat (heavens) is used here, which is usually used in Qur’anic parlance to refer to all the zones of space outside the earth.  (Compare with verse 21:32 where earth’s specific ‘sky’ is mentioned in the singular.)

Emerick, Yahiya. The Meaning of the Holy Qur’an in Today’s English (p. 827). Unknown. Kindle Edition.