back to the future

[chipp_skippi14]

hi everyone! /ttiforum/images/graemlins/smile.gifmy name is stephanie and for my L.a unit im doing an essay on "Strange Phenomena"
and i am just into this time tavel stuff. so im doing my essay on space and time travel.
The grandfather Paradox its those most interesting theory that ive heard. its amazing!
I'd like to know alot more for my report on the grandfather paradox.
"back to the future" was a great movie, the first one, when the kid (i forgot his name) went back into the past, and he had a picture with him. but when he was there to long, it started to disappear, why was that? (even though it was just a movie, id still like to know)

 

[shard]

The lad was called Marty McFly.
The idea that he was changing his own future was something the writers found hard to explain without boring the pants off the audience so they used the photograph idea.
As he changed things in the past, for example he prevents his parents getting together, bit by bit the future he knew was starting to change, the hook of his whole existence was his parents getting together, this he acheives just as he is about to disappear as well. Interestingly, he changes the future for the better for his family,himself and the Doc.
He never returns to the original timeline from whence he came though.
And would you beleive this is the simple version of the grandfather paradox?

I think explaining the grandfather paradox would be more fun if you could give a talk to the class, get them to figure a way around it, you'll get them tied up in knots in minutes, plus you'll enjoy the debate. /ttiforum/images/graemlins/smile.gif

 

[JamesAnthony]

Not quite /ttiforum/images/graemlins/smile.gif

By preventing his parents from getting together, he prevented himself from being born. Luckily for him, the change in time acted like a ripple. He had time to put things right before he disappeared. He was the youngest in his family - that's why his brother and sister began disappearing first.

The grandfather paradox is avoided upon his return is nicely avoided because he is unable to encounter his past self before his past self goes back in time. ie. he never takes away the reason for him going back in time in the first place. Yes it is a different reality, but the sequence of events in this reality do not prevent 2 'Martys' from existing for an extended length of time.

The second film gets a bit messy with Biff being able to return the future he had changed. Although one could surmise that he 'overtook' the ripple effect. A deleted scene on the DVD confirms this when we see old Biff disappearing in agony as Marty and Doc leave 2015.

James

 

[Wavefunction]

Hello Stephanie, it is always nice to meet someone else interested in time travel. I will attempt to explain the Grandfather Paradox as simply as possible.

Let's say Joe builds a time machine and wants to go back and kill his grandfather. Joe gets in, jumps back to when his grandfather was a child, finds him, and puts a gun to poor little grandpas head.

The first speculation on the Grandfather Paradox is that of Fate. Joe could not possibly kill his grandfather. Some amazing fated thing would happen that would not allow Joe to kill his grandfather. The gun may fail to fire, Joe may fall and Jr. grandpa runs away, etc.

The second speculation is that of the Alternate Universe (A.K.A. Everett-Wheeler-Graham, Many Worlds, Many Universes, Universal Wavefunction) theory. This states simply, that an alternate universe is created for every event that has more than one outcome. In this case, the event is Joes grandfather living or dying. In one universe, Joes grandfather lives, and in another he dies, this allows Joe to kill his grandfather and still remain in existence. Everett stated of the Universal Wavefunction "All outcomes [of an event] exist simultaniously but do not interfere further with each other, each single prior world having split into mutually unobserveable but equally real worlds".

The third speculation is, simply, success. Joe kills his grandfather, and Joe is erased from existence. His grandfather was never able to create his father, therefore Joes father was never able to create him.

The fourth speculation is known as the "Observer Effect". This states that "an observer is required to interact with an object in order for events to occur". In this case, it is a true paradox. This means that if Joe goes back and kills his grandfather, and is therefore erased from existence, then how was he able to go back and eliminate his grandfather if he never existed in the firstplace?

I hope this helps! Let me know if you have any questions.