Do you want me to teach you something?

OK. Do you want me to teach you something?
Say Bismillah first.
It is the story of Ashabul Kahfi (أصحاب الكهف)
Before that, read this. http://en.wikipedia.org/wiki/Seven_Sleepers#Islamic_interpretation

Muhammad was challenged by the people of Makkah who did not believe in his message and prophethood by a question that the people of Makkah passed to him from the Jews. The Jews knew that Muhammad would only be able to tell the story if he was indeed a prophet. The Jews told the non-believers of Makkah to ask Muhammad "who are the youngs who disappeared, and how many were they?". Muhammad had no clue and told that he would answer them tomorrow, waiting for the answer to be revealed to him through Gabriel.

OK. Now, be careful.
We know that Quran in Night of Qadr came down to Muhammad (pbuh), yes?
But why Muhammad (pbuh) waited to answer them?
Of course because he wanted all people to understand the process of Wahyu (Revelation).

Allah is not limited to time
So, it is meaningless that Muhammad (pbuh) get the revelation at some specific point.
But those Wahyu (revelations) should become something understandable for normal people.
So , Allah let such stories happen.
This sentence "Muhammad had no clue ".
Is both true and wrong.
But it is not important at this moment,
Only we as muslims know that Muhammad was given all the science from  the beginning.
And he behaved in a way that people understand that the source of science is only Allah.