How could disbeliever see the creation of the heavens and earth?

> Do the disbelievers not realize that the heavens and earth were ˹once˺ one mass then We split them apart? And We created from water every living thing. Will they not then believe? — Quran 21:30 > disbelievers not realize Allah points toward the disbeliever but whom? who was able to see this process 1400 years ago? > the heavens and earth were 'once' one mass then We split them apart? Science still does not know about heaven and has no clue about it, so how could disbeliever see the splitting process of heaven and earth? > We created from water every living thing Were the Arabs aware that every species is created from water? Which peoples are referred to this verse? Kindly explain it. Jazak Allah.