Have not the disbelievers ever considered that the skies and the earth were joined together as one united piece, then We split them asunder? And We have created every living thing from water. Will they still not believe?
Meaning:-
Asunder: into forcefully separated pieces, apart; divided
This Ayat is the leading explanation: This probably refers to the event commonly known as the Big Bang.
Big Bang: This startling idea first appeared in scientific form in 1931. The Big Bang Theory is the leading explanation about how the universe began. Scientists believe, with every speck of its energy jammed into a very tiny point. This extremely dense point exploded with unimaginable force. At its simplest, it says the universe as we know it started with a small singularity, then inflated over the next 13.8 billion years to the cosmos that we know today.