Well, this question is missed by most or all of people who have seen the film, but its been bugging me since I watched interstellar for the first time. so here is my question and I hope someone can give me a valid explanation. as the theory regarding black hole suggests, for an outside observer, nothing can cross the event horizon of a black hole. it would take an infinite amount of time for cooper to reach the event horizon if seen from the perspective of Dr. Brand or anyone on earth. By that I mean, Cooper will keep falling and slowing down as he approaches the horizon but he will never cross it. In that time, the humans on earth would have been extinct. So how did Cooper managed to save people on earth; whereas, for the people on earth, cooper never crossed the event horizon, and never will.   now, as for Dr. Brand, she would have started new colonies on Edmund's planet and the new colonized humans have been evolved to 5d beings, whereas, cooper is still falling.  It's too ambiguous. Or its too flawed.