Grandfather lived.

M

MildSkeptic

Chrono Cadet
Changing the past to effect the future in a way that would prevent the intial change: some have called this a paradox, most have a theory with alternate realities/existences etc.
Instead, I propose that it never happens that someone goes back in time and effects the past in such a way. It is possible that future scientists have proven me right and warn time travellers not to kill their proverbial grandfathers, but due to the fact the any human would almost certainly get curious after a while, perhaps only the most responsible people ever achieve time travel. Or perhaps we never achieve time travel. Many see it as inevitable, but what do they know. It's more than likely we'll all die before we bother to discover time travel.
 
MildSkeptic,

The Grandfather Paradox is just an extreme example of this class of paradoxes. Its used because you can easily see the implied effect. It could also be called the Parenticide or Suicide Paradox where the TT kills his/her parents or him/herself.

The less obvious paradox could be where the TT steps off a curb while crossing the street and a car stops to let him bye. The driver is now delayed getting to wherever he was going and fails to ever meet the TT's other future parent. The driver instead meets someone else, gets married and is perfectly faithful for the rest of his life - yet the TT shares the DNA of the driver and the person whom the driver never met.

The general paradox is the simple fact that the TT is present at all. He either fulfills the future or interferes with his recollection of the "future". In either case being there affects all events no matter what specific actions he/she takes.

Everett-Wheeler's "Relative State Formalism" (aka Many Worlds Interpretation) seems to resolve the paradox. The problem is that few physicists actually accept the Everett-Wheeler model.

We have a daunting problem as to time travel in general. Every solution to General Relativity that seems to allow time travel is formulated in an ideal "world" - a world where the only matter, mass or field that exists arises in a sterile black hole. Nothing else exists in that ideal universe. If the model is solved using a "real" universe where other matter, mass and fields exist outside the black hole itself and quantum effects are accounted for time travel is prevented.

We're a very long way from being able to solve Einstein's equation for General Relativity for a real universe so that time travel is allowed.
 
MildSkeptic,

Here's a synopsis of the best Grandfather Paradox short story ever written. It's Robert A. Heinlein's "All You Zombies":

The most bizarre adaptation of the Grandfather Paradox is found in Robert Heinlein's classic short story "All You Zombies."
*
A baby girl is mysteriously left at an orphanage in Cleveland in 1945. "Jane" grows up lonely and dejected, not knowing who her parents are, until one day in 1963 she is strangely attracted to a drifter. She falls in love with him.
*
But just when things are finally looking up for Jane, a series of disasters strike. First, she becomes pregnant by the drifter, who then disappears. Second, during the complicated delivery, doctors find that Jane has both sets of sex organs, and to save her life, they are forced to surgically convert "her" to a "him." Finally, a mysterious stranger kidnaps her baby from the delivery room.
*
Reeling from these disasters, rejected by society, scorned by fate, "he" becomes a drunkard and drifter. Not only has Jane lost her parents and her lover, but he has lost his only child as well.
*
Years later, in 1970, he stumbles into a lonely bar, called Pop's Place, and spills out his pathetic story to an elderly bartender. The bartender offers the drifter the chance to avenge the stranger who left her pregnant and abandoned, on the condition that he (Jane) join the "time travelers corps." Both of them enter a time machine, and the bartender drops off the drifter in 1963.
*
The drifter is strangely attracted to a young orphan woman, who subsequently becomes pregnant. The bartender then goes forward nine months, kidnaps the baby girl from the hospital, and drops off the baby in an orphanage back in 1945. Then the bartender drops off the thoroughly confused drifter in 1985, to enlist in the time travelers corps.
*
The drifter eventually gets his life together, becomes a respected and elderly member of the time travelers corps, and then disguises himself as a bartender and has his most difficult mission: a date with destiny, meeting a certain drifter at Pop's Place in 1970.
*
The question is: who is Jane's mother, father, grandfather, grandmother, son, daughter, granddaughter, and grandson?
*
The girl, the drifter, and the bartender, of course, are all the same person. As an exercise (on the road to insanity) try drawing Jane's family tree. You will find that not only is she her own mother and father, she is an entire family tree unto herself!
Click to expand...

http://www.daviddarling.info/encyclopedia/G/Grandfather_Paradox.html
 
Fantastic!!! I loved reading that, Darby. Just had to save that one and print it out.

I thought of a paradox type scenario as well, not as well written as that one you shared, but it seems that many strange situations could occur if one could indeed travel in time.

If I arrived ten minutes in the past, my destination the end of my driveway, walked throught the front door of my home, took a seat on the couch, and then watched myself step through the time machine to go to the end of the driveway ten minutes in the past.

How many of me(s) could end up sitting on the couch?

Also, if I had gone ten minutes into the past and walked into my home, would the other me(s) already be sitting on the couch?

Now, in pondering this paradox, I wonder if there still would be a central focus of thought. Even if there were a hundred me(s), would only ONE be the original, with the 'control' of what happens.

Or would each me have the ability to make a decision different than the other me(s)?

Is it possible for one of the me(s) to possibly trip on the way into the house, and get a wound, thus being slightly different than all the other me(s) ?

And which me would be the original me...to decide to turn off the time machine to prevent anymore trips into the past.

What happens to all the other me(s) when the device has been disabled ?

The device that I would use in my scenario would probably have to have a timer of some type to disable it, since I wouldnt know which one of the me(s) would or could hit the off switch.

If I never turned if off, how many of me(s) could there be...at some point, the couch would be full, so the next me that came in would have to select a different place to sit.

And what of the neighbor across the street ? What would he see from his point of view? He may only see me the very first time when I appear at the end of my driveway, but as his time flow continues, would he be able to see my house get filled up with me(s)?

The one difference between this scenario and the story you presented is that yours has a closed-end type of loop.

What happens if one has a situation with no end as a possiblity ... ?... like how many questions could be asked regarding such a scenario ?

Well, got a headache now. Gonna go for the aspirin, and be hypnotized by the television set for awhile.
 
OvrLrd,

I'm glad that you liked the story.

There's one other paradox that the synopsis didn't address. Not only is Jane every character in the short story, s/he was created from nothing. There are no points on her worldline where you can point to and say, "It begins here and ends there."
 
...s/he was created from nothing. There are no points on her worldline where you can point to and say, "It begins here and ends there."
Click to expand...

I didnt think about that, or didn't see it. Since you pointed that fact out, then I believe it solves the paradox as improbable, it seems that there must be some entry point into her worldline from the outside for the episode to occur.

Also, our drifter must have been a rather indiscriminate character, since it would seem that he might have noticed that "Jane" had a different set of equipment than what most of humanity would expect when mating with a woman.
 
OvrLrd,

he might have noticed that "Jane" had a different set of equipment than what most of humanity would expect when mating with a woman.
Click to expand...

Good call.

It's been decades since I read the story but I have a vague recollection that Heinlein covered that by having the male organs "undescended" and hidden internally or something along those lines, i.e, Jane didn't know, had delivery by C-section due to the complications of the birth and it was discovered then by the doctors.
 
Ok I have thought of this type of thing for some time now but never knew what it was called im not very smart when it comes to this type of thing.

say you went back and killed your granddad before he met your grandma so that makes it to where you never were born. right? well if you were never born then how did you go back and kill your granddad you wouldnt have. right? well if you never went back to kill him then you were born and your state of mind would be the same so you would go back and kill him thus catching you in an endless cycle of killing him and not killing him.

please tell me if this makes any sience to you.

sorry for my spelling it is very late here.
 
timewiz,

say you went back and killed your granddad before he met your grandma so that makes it to where you never were born. right?
Click to expand...

No exactly. You're there therefore you were "obviously" born. The scare quotes around obviously identify the paradox.

Its not so obvious that you were actually born because your gene pool is one grandparent short thus leaving one of your parents a parent short. Yet paradoxically it seems that you were somehow created.

If I recall correctly, this sort of paradox is sometimes called a vicious paradox because the circumstances are inconsistent with any logical analysis. In this case it is unclear just where you "came from".

The next paradox comes when we do a DNA test to check the gene pool. Grandfather's genetic markers should be there (but who knows for sure).

From your perspective, BTW, there shouldn't be any inconsistent logical paradox. Grandfather dies after you were born with respect to your proper time. The inconsistent logical paradox is only created for the observers.

This doesn't mean that you aren't aware of the fact that a physics/biology paradox exists that is hard to explain.
 
Ok but would that still hold true for this one?


You go back to before hitler ganes controul of germany and you kill him stoping ww2 from happing (i know another leader could take over and ww2 still happens but lets say that dont happen) so then your younger self never learns about ww2 and so you would never have went back an stoped it thus sticking you in that loop of endlessness.

is that way farfetched or is it posible ?
 
timewiz,

There's one more problem concerning paradoxes. On many occassions I've stated that in physics scale is always an issue to consider.

Human beings are large, complex systems of subatomic particles - atoms, molecules. If we stand back and view a large complex system from a distance we can see the paradox if time suddenly starts running backwards.

Its possible but highly unlikely during the life of the universe that we would observe a broken egg "fall" up off ofthe floor and reassemble itself into a complete egg.

But if instead of looking at the large complex system at a distance we move up close and personal so that we can see individual atoms and molecules. The paradox disappears. We can't tell whether time was running forwards or backwards based on our observations of the atoms and molecules. They would "wiggle" around with the same Brownian motion no matter which way the clock was running. In fact, based on T (time reversal) symmetry, that we say that time runs toward the future is simply a convention - it is not a fundamental physical law. For all we know the "real" state is that time is running backwards. We don't notice anything abnormal because that would be the normal state of the universe.
 
timewiz,

You go back to before hitler ganes controul of germany and you kill him stoping ww2 from happing (i know another leader could take over and ww2 still happens but lets say that dont happen) so then your younger self never learns about ww2 and so you would never have went back an stoped it thus sticking you in that loop of endlessness.

is that way farfetched or is it posible ?
Click to expand...

Last question first: farfetched or possible?

The ability to actually time travel to the past is highly questionable, at best. There are sets of soultions to general relativity that suggest that time travel to the past is theoretically possible if spacetime is sufficiently warped. That usually defaults to some sort of black hole solution.

However, all of the black hole solutions, so far, that seem to allow time travel are set in "universes" where the only thing that exists is the black hole and its gravitational field. Even the "time traveler" is just a mathematical construct with no physical form in those solutions. As soon as real matter and quantum effects are introduced into the equations time travel is prevented. Einstein's spacetime metric equation in general relativity is so complex that no one has been able to solve it for a real universe like the one we live in.

As to the first question: Kill Hitler - prevent WWII

The first paradox arises when the time traveler decides that he has to make the time trip. If, in fact, Hitler is killed before taking power there's no Hitler for him to worry about. The question has to arise as to what motivated him to want to kill Hitler?

Take the time traveler out of the equation. If Johannes Jones, a non time traveler, kills Hitler in the summer of 1923 he's dead. No Beer Hall Putsch on 8-NOV-1923. If "history" can be altered by a time traveler it can be altered by a non time traveler. No paradox.

Now assume that Johannes happens to be a time traveler from 2036. Same result. He simply killed someone who to his knowledge had no particular effect on history after 1923. Its simply incidental that he happens to be a time traveler. His action is precisely the same as the non time traveler's action and has the same effect.

In March of 1933 Adolph Hitler does not become Reichchancellor because he's been dead for 10 years. No one on the planet, in 1923, 1933 or any time thereafter, would be aware of any logical paradox.

From the perspective of the people in 1923, 2036 and Johannes himself, he murdered a semi anonymous malcontent WWI veteran turned radical student who had no real effect on the course of history

So, why did he kill him?
 
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