A Time Traveler has a lot more than the 'The Grandfather Paradox' to worry about.  Here's why.

Image of Time Traveler Marty McFly starting to disappear.    Image is from the 1985 movie Back to the Future.
Uh oh. Time Traveler Marty McFly's journey back in time has unintended consequences. BTTF image courtesy of Universal Pictures.

There's a theory about time travel, it's often used in debates in an attempt to prove that a journey through time simply isn't possible.  It's called "The Grandfather Paradox".  The theory is this - if I could travel back in time, and I traveled to a year where my grandfather was a young man, and say, I got into an argument and killed him - how could my father be born?  How could I then be born...and then go back in time?

 

Marty McFly faced a similar time travel paradox in Back to the Future.  Only his situation was a bit different - a chance encounter with his mother prevented her from falling in love with his father at the right time. You know the rest.

 

Problem is I think time is a lot less flexible than time travel movies, tv shows and books make it out to be. I can't prove it...but consider this.  We have a time traveler, his name is Glenn.  From the moment his time travel machine deposits him in the past, he's already changing things.  He's bumped into someone, he's bought a drink at a corner store, he's taken a break on a park bench. All of these things don't seem like very much, do they?  But I believe they are.  I believe every one of Glenn's actions would snowball out of control.

 

Take that person he bumped into, Mike.  Mike is now 2 seconds later getting to the corner.  The first time, without the bump, he would have crossed the light at the last second. Now, after a split second's hesitation, he's decided to stop and wait for the next walk signal. That means he's an extra minute crossing the street.  Because of that, Mike see's a sales sign in a store he wouldn't have noticed before, because previously his view would have been blocked by a passerby.  He goes into the store, he buys a shirt.  He's now 22 minutes behind.  By the time he gets home, he's late for dinner.  Part of the conversation at dinner is about the great deal he got on the shirt, and it leads to other topics that would not have been discussed the first time around.  Dinner gets extended.  Putting the kids to bed doesn't happen until 40 minutes later than usual.  Mike and his wife had been planning to have another child, but as a result of things going later, they do not try that night.  Their son is not born.  But they try a few nights later and fast forward nine months and they have a daughter.

 

Image of NBC poster for the 1997 series Journeyman, with picture of lead Kevin McKidd.
Reporter and Time Traveler Dan Vasser accidentally erases his son from existence in an episode of Journeyman. Image courtesy of NBCUniversal.

There was a TV show in 2008 called Journeyman that dealt specifically with this situation.  In the show, a San Francisco newspaper reporter (played by Kevin McKidd) finds himself involuntarily traveling through time in each episode.  After one time travel adventure, he returns home to find his son Zach has been replaced by a daughter Caroline.  As a parent I could only imagine the horror...that, and he has to deal with the fact that nobody remembers Zach! (By the way, Journeyman was a great show. IMDB has it rated as 8.1, which is high for IMDB.  It only lasted one season, and deserved better).

 

Now think about Mike again and his story.  He was late getting home.  But what about the sales person he interacted with, when he bought the shirt? Or the person he struck up a conversation with, in line? The course of history has changed for these people too, and for all the people they interacted with. 

 

Now think about the time traveler, Glenn.  Mike is only just one of the people he interacted with, and look at the changes. What about all the other people Glenn interacted with?

 

This is why I believe the future would be quite a different place if you change even one very minor thing in the past.  The Grandfather Paradox is a very specific example of an extreme action causing an extreme result, but I believe any change to the past, no matter how small, would have serious repercussions. In other words, a Time Traveler would have already been changing history long before he got to grandpa's house. 

 

Read more on the Grandfather Paradox and time travel quantum physics

 

 

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Comments: 4
  • #1

    Tara Murphy (Monday, 21 November 2016 11:39)

    Very thought provoking! Fascinating and informative. Thanks for sharing!

  • #2

    Eric (Friday, 02 December 2016 12:31)

    Things that make you go Hmmmmmm... (Arsenio Hall reference - anyone? anyone?)
    Anyway, this is a great conversation starter! I always wondered about this question with regards to any time travel movie - notably Back to the Future and the Terminator franchise! In fact, even the smallest iota of change in the past would significantly, exponentially change the future - so even though Marty saved his mom from Biff and his grabby hands, and made his dad into the hero of the day, all of the other events that transpired while Marty was in the past would have massive implications on future events - the only way for this movie to make sense is if the events of his time travel have always taken place... but they didn't the first time around. Or did they? I think string theory and the idea of alternate universes could come into play (or could they?) when it comes to the grandfather theory, but now we are venturing out of the realm where I have any sort of knowledge, so I'll just leave it here as is, and say "good post! lots of food for thought!"

  • #3

    Nicolas Kadima (Monday, 05 December 2016 12:07)

    Check out the 1952 short story "A Sound Of Thunder" by Ray Bradbury. You can read its synopsis here (spoiler alert); https://en.wikipedia.org/wiki/A_Sound_of_Thunder
    It's a got a superb twist ending.

    I don't know if time travel will ever exist, because perhaps if it is created in the future it will also mean that it has always existed. I mean that If you can go back to the dinosaur era via time travel, then travel time travel has been around for more than 65 million years.If you go back even further, say 3 billion years ago, you are now making time travel a reality of the year 3 billion BC. Just a thought. :-)

  • #4

    Mike (Thursday, 03 August 2017 16:36)

    With Back to the Future being the best movie ever made, I had to read this entry from last year.

    It seems to me that if someone went back in time and caused a change, those of us in the present living linearly would not know of this change because we would have just grown up with whatever happened and our memories would be of the change not the original that we never know. This is where deja view feelings come from. They are minor flashbacks of what happened before time and space where changed.

    I'm still waiting to go home and find out my house it renovated, I'm wealthier than I was in the morning and there's an awesome black pickup in the garaged all waxed up and ready for my weekend trip.