If no one has ever came across into our universe then how have they placed parts of the device in our universe and they even know the co-ordinates of the device parts? The device is the one that Peter can only trigger and that can devastate our universe and save their universe.
No one placed parts of the device in our universe.
I'm not sure how much of Fringe Season 3 you have already seen, and so I will use spoiler blocks liberally.
You are making two incorrect assumptions:
We find out in the episode "The Day We Died" that the machine exists in a
There are no so-called
He sends the machine