Milquetoast, I can’t explain many of the films assertions in a logical way because the story (in the film version) was chock FULL of plot holes so large you could drive a truck through them. Many of the incongruities just had to be overlooked if one was to get any enjoyment out of the film.
Also, I can’t defend the movie’s positions when they defy the laws of physics. I can only say that when one watches a science fiction or fantasy movie, one suspends one’s disbelief and accepts whatever rules the storyteller has set for the universe the tale is set in.
Within the universe of “The Time Machine” (film version), the statement by Alex that, “I could come back a thousand times and watch her die a thousand ways”, and the statement by Morloch-boss that, “You built the time machine because of Emma’s death so you can’t use it to go back and save her”, both establish the limitations of time travel available to Alex.
So to answer your question, I came to my conclusion based on the logic presented within the story. Of course, I don’t hold that these boundaries carry over into the real world, or even that the logic presented within the film is flawless.
Further, the point you made about using the time machine to go back to a point before the invention of the machine itself is one of those plot holes I referred to. The film establishes rules for time travel, then proceeds to break its own rules. If Alex can make a machine able to go back before its own creation, then he should have been able to save Emma; likewise, if he is not allowed to go back and save Emma because her death is the precipitating factor in the creation of the time machine, then Alex should not have been able to go back before her death. … The film does not obey its own rules. So one can’t analyze it too closely. I was merely trying to answer Methos’ question as I understood the film.
(As a side note, I don’t think that “multiple” time lines necessarily requires an “infinite” number of time lines. But that doesn’t affect the movie points we’re discussing.)
What is more, even if it IS possible to go back and save Emma if one comes back to the “right” time line, Alex came to the conclusion (erroneously or not) that it couldn’t be done, and so stopped trying after the first attempt.
Finally, consider what Alex’s life would likely have been like if Emma hadn’t died. During the four years after their marriage he would have had a honeymoon, had a couple of kids, and more firmly establish his position at the university in order to support his new family. He would hardly have had the opportunity to become obsessed with time travel and devote four solid years of work to developing a time machine.
As to Methos’ “second question”, the OP also asked about the meaning of the head Morloch saying, “You were the cause of me…”; which in the film was phrased more nearly as, “You are the inevitable result of your tragedy; just as I am the inevitable result of you.” I didn’t see any explanation of this in the film, and so I speculated about its meaning in the paragraph below that statement.
Do you have any insight as to what Morloch-boss may have meant by that?
