I got into a friendly debate with a friend about time traveling. Their main argument that it could never exist was because of the grandfather paradox. For anybody not familiar with this, it is paradox which stats that if a person travels to the past and kills their own grandfather before the conception of their father or mother, that would prevent the time traveler's existence. So, if your grandfather is dead, you were never born to go back in time to murder him in the first place. Ok, I get that. Seems logical. My first question is why would you even do that? My second question is if this scenario creates a loop in time? If you did kill him, making you non-existent, there is no you to go back and kill him. That means that he would live on as he was before, thus allowing him to have offspring creating the ability for you to be born anyway. Then there are alternative timelines. These are my favorite. Maybe you do go back and kill your grandpa. This would just create an alternative timeline in which two realities are possible. One were you cease to exist and one where you do. Instead of changing only one reality, you actually create two that split-off from your actions. So maybe time travel on one plane of reality is impossible and time travel would actually be jumping from you one reality to another. I've always loved the concept of time travel. It's fun to think about and debate. I'm not saying that I truly believe it is possible, but, I am an open-minded individual that believes that anything is possible. I always thought that the Back to the Future movies were really good at playing out all the scenarios. I only have a problem with one of them. Back to the Future II. When Marty traveled forward 30 years to 2015, wouldn't he have entered a world in which he suddenly went missing back in 1985? This is where the alternative timeline would come into play. One more thing about the movie. Like I mentioned above about time loops, is Marty stuck in one? He is the reason he exists. He went back in time and was the reason his parents got together, which, ultimately allowed him to be born. He was born, lived, and then in his future had to return to the past to make sure he was born. Is he in a time loop? This kind of stuff will make your mind melt. Especially when you get deep into the quantum mechanics of things. So forum friends, what say you?