The Grandfather Paradox

Oh boy, this is a tricky one. If he goes back in time, then he will of course wipe himself up. Of course, if he wipes himself up, then he will not be able to go back in time to wipe himself out so he is not going to be wiped out but since he is wiped out then he would not be able to go back in time to wipe himself out. But his lack of existence hinges on his existence so...yeah. Of course, strictly speaking, every decision that we make, there is an alternate universe out there were we made the exact opposite decision. At least that is a common theory. So all of existence would not collapse, just that particular branch of the universe. There would be other universes based upon that point, perhaps he decided not to go back in time, perhaps he didn't succeed, perhaps his time machine failed. It can give you a headache if you think too much about it.

That is an interesting paradox indeed. If you go back in time and kill your grandfather he would not be able to have your father which means that you would never be born. Since you were never born you could not possibly go back and kill your grandfather, therefore her survives and you are born... It keeps going on like this. Who knows what would happen. Some people say that an alternate universe would be created in the instant you killed your grandfather. In that universe you would never have been born. Others say that you would never be able to change the past and the fact that you are alive means that you were unable to kill your grandfather. Therefore anything you try would only be met by many obstacles and the outcome would always be the same.

This is something that has always intrigued me. Better than it's usually explained by scientists, you can see this by watching Back to the Future, as Marty's photos begin to fade. But is that what would happen? I think not. If it was plausible to physically travel backwards in time, I don't believe we would be able to physically interact with the surroundings. We would be viewing more of a recording of time already passed; and even this would be jumbled and scrambled information. The information is never lost, so even my keystrokes from seconds previous to typing this sentence are now part of the fabric of time. But even if I crafted a nifty little wormhole to slip through, I'd only at best be watching myself type, unable to physically exist in the same time and alter the now-present. In terms of universal law, I don't believe the universe would allow it to get to the point where he pulls the trigger. Nothing happens when he pulls the trigger. The bullet and the grandfather did not exist together in the grandfather's present, so there is no way to alter this. But given time to think about it, my answer may well be different tomorrow.

You give yourself too much credit for having such power. When you go back through time and meet your grandfather, you will not be able to kill him. There are forces in the universe that will limit your ability to mess up that which they do not want you to mess up. By the time you acquire time travel capabilities, you will acquire the wisdom to understand this. Go ahead try it. Attempt the impossible.