If God wanted our prophet Mohammad to know every thing he would have done so.
But is on purpose so that the people continue the search of knowledge and science.
The Nasa invasion of space was something new for people.
In the Quran it says
"O ye assembly of Jinns and men! If it be ye can pass beyond the zones of the heavens and the earth, pass ye! not without authority shall ye be able to pass!"
Explaination:
This authority is the knowlege and science.