What if there is not one but many universes, separated from one another. Where they would be and how many there is?

God created seven heavens and seven earths. It's scientifically proven now. By extension, there are 7 universes distinct from one another. And they are situated as the rest on level planes, one on top of the other.

*[71.15] Do you not see how Allah has created the seven heavens ,~ one above another,

Finding scientific proof of the existence of 7 universes would be difficult, if they are really separated from one another, then their consciousness is as well, we are as oblivious of their existence as they are of ours...

Who could have ventured in proposing that there are 7 universes, when a single universe is almost infinite in size, I do not know. It's worth researching.

*[25.59] Who created the heavens and the earth and what is between them in six periods

Theses universes, if they exist, could have been created as the rest in 6 periods, and they more probably than not sit in 6 different time dimensions, the seventh being one of non time.
Thus, they are not only separate in existence, they are also separate in time.

The word universe itself comes a single time in the Koran, and it is in a plural form and not in singular. Contrary to the translation below by M.H. Shakir

*[41.53] We will soon show them Our signs in the Universe

Universes or horizons, Al Afaaq ألأفاق  is a plural form in Arabic of Oufouq أفق horizon

[41.53] We will soon show them Our signs in the Universes 

The translator simply rendered "universes" for "universe", why? Possibly because with all due respect he either didn't truly grasp the meaning, or couldn't find any tangible verse to build upon, since that word is mentioned only once to my knowledge:

They are more than one then. And if they are plural, why wouldn't be any different from the 7 heavens or the 7 earths? Surely they are 7 in total.

The created realm would be infinitely greater than previously thought. Populated by other creatures we do not know about. Each thinking themselves to be on their own. 

Going from one universe to another seems plainly unachievable with material means, since they are separate from one another.They are 7 distinct planes of existence, and nothing guarantees that if you exist on one of them, that you are going to exist in another. In fact more probably than not, you could simply not exist in another universe, and never leave the universe where you have been created.

As for how old they are, mankind being a recent creation in this universe where there are untold more ancient races, those universe, be it the first, second or third that were created first could be infinitely more ancient than the universe where we live in. I think also that same as heavens and earth, the 7 universes are already created.

Recent existences, who knows how old the first created universes are? Some alien races could have trillions of years of civilization.

If we ponder on the name of Allah, we find that there are 7 characters

1. Alif 
2. Hamzat waṣl 
3. Lām 
4. Lām 
5. Shadda
6. Alif khanjariah
7. Hā

Obviously these universes would have been created in a succession over 6 periods of time, and possibly even one of these universes is uncreated since there is no period of time allotted to it, it always was then... Altogether they constitute the sum of creation, there is nothing aside of them.

Nothing but the void of space. Immense regions of void impossible to cross even in several lifetimes, keeping such as veils each universe completely insulated and separated from the rest. 

How are they ordered? On planes one on top of the other, and each separated from the rest by the void of space. What more? Everything needs order. When we research what else is numbered as 7 we find:

[2.261] The parable of those who spend their property in the way of Allah is as the parable of a grain growing seven ears (with) a hundred grains in every ear; and Allah multiplies for whom He pleases; and Allah is Ample-giving, Knowing

What are those 100 grains? And the 7 universes would stem from a single matrix? And in them would be 100 grains... What should we understand by that? 100 populated galaxies per universe? Too few, there are trillions upon trillions of galaxies in the universe, and much more than that is populated. What are those 100 grains then? 

It remains a mystery, a 100 grains in every ear... like what... 7 universes, 7 ears, 100 grain in each universe... 100 what...

7 universes ordonned one on top of the other like the heavens or earth would look like this, in each of them there's a hundred somethings every year... or 365000 years. A hundred somethings every era. A 100 what, grains, new races? Galaxies don't form in such periods of time. If not races, stars? there's trillions of trillions of them. What can we infer from grain. Grains are supposed to germinate, to become life. 

It could be that each universe was populated with 100 sapient races when it was created, and that now they are billions across each universe. 100 sapient races at the origins of time, and a 100 in each different created universe. Of which mankind is one of course, over such periods of time, there could be billions of races now, in each universe, living separate from one another.

Each thinking that his universe is everything there is. Life, death, heaven, hell, all happen there. While in another universe they think the same. God would almost fool everyone into thinking that they're the sum of creation...

Donc le big bang intial aurait donné l'existance a 6 univers, l'un se contractant puis donnant naissance au suivant. Ce que nous observons, le Big Bang est la mort du precedent univers. 

Nous en sommes actuellement au 7 ieme monde, le dernier

A sa fin il est probable que Dieu recrée l'ensemble de sa creation par le meme mechanisme et les figes dans le temps, mais cela ne semble pas etre le cas.

Le sens de "and Allah multiplies for whom He pleases; and Allah is Ample-giving, Knowing" est que ce processus est constant, il n'y as pas de limite dans le temps.

Il y a cependant une dimension a considerer et qui est celle du passage a l'ordre, la notion d'equilibre. Car une création une fois parfaite n'est plus a soustraire du reste, ce qui nous ramene au visuel precedent. Un ordre ou une dimension incrée est l'ordre divin, et ou les 6 autres univers sont nés par succession. Jusqu'au notre.

A sa fin, la création sera parfaite par Dieu, alors il n'y auras plus rien a y changer, excepté ce que Dieu veut, c'est la notion d'un paradis universel. Une creation parfaite, plus besoin donc de la détruire pour la recréer de nouveau.

Et dans ces memes univers, chaque ère se créent 100 nouveaux grains, des races tres probablement. L'univers etant immense, le dessin de Dieu est de le peupler, sans doute y seme t il des races comme quelqu'un qui entretiens son jardin.

Des races bien sur différentes de celle qu'il a crée déjà. Tandis que d'autre ne sont plus, souvenirs antédiluviens de races disparues. Cependant possiblement des ancêtres communs, chaqu'un parti dans sa direction dans l'espace, et dont la seule chance de rencontre avec d'autres dans cette immensité nécessite des milliards d'années.

Entre temps elles auront évolué différemment c'est certain, les reptiliens en sont un bon exemple.

The level plane that makes possible contact is technological achievement. Civilizations do meet, and Aliens are obviously more civilized than you. If you had half that stuff you show in movies, maybe you would meet them...

Why are they more civilized than you? Because they are older races, created eras ago.

*Holy Koran