[quatumrulesoverall]

A very interesting fact of Time Paradox, how our future, past, and presence are interlinked and correlated.

[Qfwfq]

But what exactly is your intention, in starting this thread? Without making an actual point, its hardly the way to start the kind of discussion we want in this forum.

[quatumrulesoverall]

Originally Posted by A website

When one reads Science Fiction there is hardly anything so fascinating and yet so frustrating as the 'Time Travel' story. Fascinating, because it often explores the question 'what would things have been like if...?" or "if one could change a small thing like the position of a grain of sand would that have large effects in the future?". These questions are at the heart of personal or historical regret. Suppose Hitler were never born. Would this be a better or worse world today? Would it be a different world 100 years from now or would the forces of history push towards a singular result?

The stories are often frustrating due in part to a vaguely spelled out theory of time which often allows events that are confusing, contradictory and paradoxical. A science fiction story should not leave us with more questions than it resolves. For a reader of Fantasy, this may be acceptable, for Fantasy is not supposed to be taken as explanatory, prophetic or possibly realistic. But a good science fiction story should have explanations that are not incoherent and if in the story there is something which is claimed to be impossible, then there should be an explanation for that also.

At the heart of the problem is the 'Time Travel paradox' which goes something like this. Suppose a person travels to a time before she was born and breaks a causal chain that led to the traveler's birth. This problem has been commonly explored by asking 'What if you killed your own grandmother before she first conceived?' (Curiously the problem is never expressed in terms of killing your own mother). The apparent paradox is then of a logical sort: P entails NOT P and NOT P entails P. If you kill your grandmother then you would not be born, which in turn would bring it about that you not travel into the past, thus you would not kill your grandmother, thus you would be born causing you to again travel into the past to kill your grandmother.... ad infinitum.

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I was so shocked by this concept and keep thinking why the people in the future still cant travel to the past...

[EStein]

Originally Posted by quatumrulesoverall

... Suppose a person travels to a time before she was born.

Suppose that such a thing is impossible.

[Lambus]

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[sanctus]

Originally Posted by EStein

Suppose that such a thing is impossible.

MAybe unlikely, prove it to be impossible....

[quatumrulesoverall]

@Estein: How would you know that is impossible?
@Lambus: the definition of paradox: A paradox is an apparently true statement or group of statements that leads to a contradiction or a situation which defies intuition. (Wikipedia). There is no straightforward definition for "reality".
@Sanctus: because you did not see it doesnt mean that it doesnt exist.

[EStein]

Originally Posted by quatumrulesoverall

@Estein: How would you know that is impossible?

Did I say it was impossible? For sake of discussion, I said "Suppose that such a thing is impossible." In spite of the great movie, Back To The Future, the time arrow seems to have only one direction--forward. Personally, I think there's a better chance of a space alien giving a press confrence on the White House steps tomorrow than traveling back in time.

Here's a great little article from The Why Files called Trapped In Time.
...."Time is nature's way of keeping everything from happening all at once, as Woody Allen became famous for saying."

[Tormod]

Originally Posted by quatumrulesoverall

A science fiction story should not leave us with more questions than it resolves....a good science fiction story should have explanations that are not incoherent and if in the story there is something which is claimed to be impossible, then there should be an explanation for that also.

Most good science fiction stories are simply stories set in a sci-fi environment. I see no reason to demand of science fiction writers that their physics be explained perfectly.

As long as their technology is consistent within the universe they describe, and as long as it is plausible, we should accept the poetic license that all writers have.

[CraigD]

IMHO, depictions of time travel paradoxes reached their fictional literary zenith in the following dialog from David X. Cohen’s “The Why of Fry”, episode #64 of the cartoon series “Futurama”:

Nibblonian: "It's a genetic abnormality which resulted when you went back in time and performed certain actions which made you your own grandfather."
Fry: "I did do the nasty in the pasty!"
Nibbler: "Verily. And that past nastification is what shields you from the brains. You are the last hope of the universe."
Fry: "So, I really am important? How I feel when I'm drunk is correct?"
Nibblonian 1: "Yes. Except the Dave Matthews Band doesn't rock."

Before, 2003, students of time travel science fiction could only refer to this scenario with uncatchy references to stories such as R. A. Heinlein’s 1959 short story “All You Zombies-”, or thrown-off lines like “Temporal Parthenogenesis”. Now, thanks to Cohen, we can refer to the time travel paradox of being, rather than killing, one own grandfather by the catchy phrase “Past Nastification Paradox”. (although RAH’s AYZ paradox is an notch more complex than DXC’s TWOF).

In all seriousness, time travel and its paradoxes can be seriously considered, yielding some interesting conclusions and implications, but it’s a technically demanding pursuit. On of my favorites approaches to a study of some fundamentals involves a hypothetical, frictionless pool table, with perfectly elastic balls where a ball entering one pocket emerges from another with the same momentum some amount of time after or before it enters. It’s possible to calculate the position of any system of balls at any time on the table, though the calculation needs to be done iteratively, as balls from one position in time jump back to interfere with themselves or others from at an earlier time.