Would the Grandfather Paradox Actually Happen?

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Why time travel should not be viewed as a speculation in the same level as the many worlds theory or the superstring/M-theory? AFAIK, no evidence exist to either of them, including time travel. There is some evidence however of traveling to the future with the special relativity theory but when it comes to the past, just seem to be conjectures and all these ideas seem to have their own mathematical models, if I'm not mistaken.

If parallel universes don't exist, then time travel could be likely to face the same reality. There are some things to consider when making a case against time travel, the cronology protection thing that some physicists hold, to prevent a person going to the past because it would lead to an impossible event, violation of causality, some argue that a person disappearing in the present and appearing in the past would violate the second law of thermodynamics, although that doesn't seem to apply in the microscopic level. A multiverse, some argue, to be the answer to those problems. The question is how much weight can we put against each of the ideas over the other.

Not necessarily. What if we were ignorant of it?

Well, i could be wrong, but I think the line between strings theory, the many worlds interpretation, and CTCs is pretty strong. The theoretical possibility of CTCs is just a potential consequence of the well established properties of spacetime's geometry given by GR.

On the other hand, the many worlds interpretation is highly controversial and indeed may very well be just plain unscientific. And who can say about string theory?

It seems to my mind that just because we're discussing time travel doesn't mean we should take everything as equal in plausibility.

Yes, good point.

If existence has any meaning at all, then You exist, right here, right now, irrespective of the past. So maybe you killed grandpa, and maybe "you" were never born, but that doesnt mean that the past catches up with you and vaporizes you.

Meaning I think the past is mutable(if time travel is possible), but the present is not. Meaning, any massive changes you cause in the past leave you in your own reality, and simply change alternate universes. Which is pretty much the same as just imagining it.

No, you could not kill your grandfather. You might be able to wound him, though.

What if I don't kill him but see to it that he is unable to perform sexually?

That would only be possible if you were already born. You couldn't do it if you went back to before you were born, otherwise you wouldn't exist to go back in time.

why is this in PPR?

The Philosophy of Time Travel.

That book isn't nearly as thick as it should be. It doesn't even posit a mechanism by which to achieve time-travel.

(In the movie that is.)

The science forum asks "why?"

PPR asks, "why not?"

The question about this issue would be, at one point discussions about Time are well related to Science and at one point to Philosophy?

In Red vs Blue, one of the guys gets sent back in time and attempts to stop loads of things from happening but in his attempt actually causes all the problems in the first place. Just like in Terminator, skynet sending back a T-101, which leads to skynets creation causes John Connor to send back his father into the past. Predestination paradox. So if you did go back in time, whatever you did do could end up playing a part in causing events in the future to occur.

People use the example of lack of time-travellers from the future to speculate that time travel is unlikely/impossible. Either we have had time-travellers from the future who have kept low, because, to be honest, if some joe bloggs says hes a time-traveller then not many people will believe him or that people in the future decided that time-travel to the past is too dangerous Either that or time-travel to the past is impossible. There are tons of speculations.

We can speculate all we like, until some matey builds a time-machine we'll most likely never know and even if someone did build one, testing these paradoxes wouldn;t be a very good idea.