Humans (scientists) have the need to understand the World around them, they discover, observe, examine and prove things around us and make laws about them. That's common sense or intelligence. Of course, everything can be questioned from the philosophers point of view, philosophers can even question if 1+1 is equal 2. And at some point they can even make a theory that 1+1 is not 2. That's the philosophy.
Yes, everything is possible. Idea that Matrix movie made is possible. Idea that nothing really exist and that all around is hologram pictures placed in our brain by higher intelligence is possible. Idea that 1+1 is not equal 2 is possible.
But those are just guesses and theories, those are beliefs.
Human brain by it's common senses and intelligence can only be certain in what it's capable to understand and prove. And that's that 1+1 is equal 2, Earth is a ball-shaped object, our nearest neighbor galaxy is 2,5 million light years away from us, there are 4 fundamental forces that propel the whole Universe, and so on and so on...
In last few decades science have pushed the edges of knowledge so much that even they (some great minds) cannot agree and comprehend all of it, so how should we (that don't even think about it much) comprehend those things? First step for us to get to know something is to realize and accept that we don't know. That's good old Socrates saying: "I know that I know nothing"..
Some things we know, to some things we can only wonder..
The thing is simple, as I've already said, Human brain is not able (do not have capacity) to figure it all out. Same as animal brain cannot understand how did the Humans made micro-chips which allows us to play Worms or talk right now from the other side of the planet to another, that's how we cannot understand infinity of the Universe or "God" or whatever.. Our brain just cannot go further than 3rd dimension (at least today).
See this impressing animation of the scale of the Universe that Humans have observed so far:
Makes U wonder, doesn't it? ;x