Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Back to the future - let's try it one more time

  1. Dec 15, 2005 #1
    so the discussion on the movie last time didnt go too well, coz i focused on scienctific concepts rather than the philosophy ... so i decided to make another thread

    1)does back to the future at any point tell that marty actually slipped in parallel reality? or it doesnt become clear until II (i havent seen II)? or was it something we were supposed to interpret?

    2) also, at the end, marty runs away from the terrorists again in the time machine ... and he will apparently go to another universe ... so will it keep happening?

    3) also, different situations can take place in different realities ... but is it possible NOT to have same characters?
  2. jcsd
  3. Dec 15, 2005 #2
    1) no, the premiss of the movie was that there is one universe and Marty is traveling through the one universe's time line.

    2) Yes, what happens in the past must happen, so Marty needs to travel back.

    3) That has nothing to do with the movie.
  4. Dec 15, 2005 #3
    ^Dude, did you watch movie 2?

    1) Yes, when Biff went back to give the magazine to himself, he changed the timeline, so the future was on a branched timeline, different from the one Marty came from. Doc explains it in-movie.

    2)Yes, but nothing'll change because of it. Past happens, ya know?

    3)Um... Yes, you can have different people in different realities. But, then again, what's the movie have to do with this?
  5. Dec 15, 2005 #4
    I think that the alternate time line was just an illustration of what the change did to the present, not that they are in an alternate reality.
  6. Dec 15, 2005 #5
    The whole series uses a branching timeline that is independent of the characters. When Biff changes the timeline in II, marty's reality is changed, but not himself. He is still the samy marty that came from the original timeline, even though that no longer exists.
  7. Dec 15, 2005 #6
    If that were true, Marty would not be disappearing from reality in BTF I.
  8. Dec 15, 2005 #7

    I never said the series was consistent. :biggrin:

    There are a lot of problems with the way it portrays time travel. However, what I said is true of the second movie in the series, that's what happens.
  9. Dec 15, 2005 #8


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    While the series has it problems with how it deals with Time travel, I wouldn't say that it not self-consistant. One thing to keep in mind is that in the first movie there seems to be a type of hysteresis in the effects it causes. Marty arrives in 1955(the first time) on Nov 5th. Shortly after, he interferes with his Parent's getting together. Yet it isn't until the night of the storm, Nov, 12th, that the effects of this interference catch up with him and he starts to vanish.

    When they return to 1985 in the second movie, they are only there for a few hrs and then return to 1955 on the 12th of Nov. This total time period is less than that apparently needed for the disruption of the time line to "catch up with them".
  10. Dec 16, 2005 #9
    In the first movie he almost kept his parents from getting together and that is why he was being effected. In the second movie with the "parallel time line" his parents had still gotten together though circumstances had changed. Because of this I guess there was no reason for his existence to be threatened.
  11. Dec 16, 2005 #10


    User Avatar

    Lets talk about the Terminator movies now :biggrin:
  12. Dec 16, 2005 #11


    User Avatar
    Staff Emeritus
    Gold Member

    Aren't these homework questions?
  13. Dec 16, 2005 #12


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Ah, but in the second movie, old Biff goes back and creates a new timeline in which the Doc is commited. If this happens, then doc never invented a time machine and the verisons of Doc and Marty that traveled back from the future wouldn't be there.
  14. Dec 16, 2005 #13
    That's right. I had forgotten about that. I vaguely remember the impression of "tempral storm" or something like that traveling backwards from where Biff left in the future.

    There's an interesting temporal paradox in a book called "Anubis Gates" by Tim Powers. The main character is a poetry scholar and goes back in time. He winds up being the one to write the poems that he was most intrigued by but he wrote them from the memory of having read them in the future. Powers didn't do that mistakenly though, he points out the paradox himself and leaves it hanging at the end.
  15. Dec 16, 2005 #14


    User Avatar
    Science Advisor
    Gold Member

    There have been other threads that talk about time travel on this forum. (Of course!) Time travel into the past seems to change something not only doesn't make sense, it just isn't possible. Something will always prevent you from succeeding. If you DID succeed then you wouldn't have had the motivation to time travel in the first place. You may have an unforseen delay on your way to whatever event is significant to the trip. It would almost be something out of Laurel and Hardy. Nothing EVER seems to go right. No matter how many trips you make you won't succeed. It seems that nature is toying with you keeping you from completing your task. But it is really a filter effect if you think about it. We go so far as to say that nature just plain won't let us interfere with anything that could have an effect on whether or not we attempt to time travel. For instance, suppose I go back in time one week and start walking down the street. I see a person I know about a block away and for some reason decide I want to punch him in the nose. Seems like a random enough of an event right? If I catch up with him and succeed in this and actually get him a bloody/broken nose, it means that this person and myself have no connection in the future that would relate my hitting him to dwindle my desire to time travel. Any connection we have in the future after I socked him could REINFORCE my desire to time travel though. Of course I wouldn't tell him that I traveled from a week in the future to hit him. Make sense?
  16. Dec 16, 2005 #15
    I think I understand....

    If your impetus to go back and fix a problem and you actually fix it, then there is no reason for you to travel back in time in the first place which would mean that you never go back and never change history.

    BUT... if you go back and change history, that history has happened, and that fix will still exist as you travel forward in time.

    That fact itself necessitates multiple quantum realities if time travel is possible, were you can change anything.
  17. Dec 24, 2005 #16
    not really :)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook