Jacob: "Time isn't linear we just perceive it that way." Nick: "Ah! Like The Terminator! The machines send Schwarzenegger back to kill Sarah Conner so that John Conner can never be born. But if John Conner don't send Michael B back to protect her then they never fuck and John Conner ain't born in the first place." Jacob: "That checks out."
Nick explains the space time continuum by using The Terminator as an example.