Time travel; a concept thought about for centuries. There are so many thoughts on its (non-?)existance, it's unbelievable. It's the primary gimmick of more than a handful of films, programs and literature, including many high-up examples as the Back to the Future film trilogy, and the several-decade-long UK sci-fi series Doctor Who. Time travel is everywhere.But from a realistic perspective? It seems impossible. Possibly the most famous example disproving time travel is the Grandfather Paradox: "If you went back in time and killed your own grandfather before he gave birth to the relevant parent, how could you have been born and gone back in time in the first place?" But there's a side-road to this. Perhaps nobody currently in existance could/would do it for fear of erasing themselves. Anybody that would, and did, simply wouldn't exist in the first place.
One idea is that time is not a single, linear line. If you did go back in time and do anything to alter the future, it would simply create a new "branch". These two timelines would then run independently. As odd as it sounds, and as incredibly difficult as it is to visualise, it's plausible.
Perhaps time isn't even a dimension. There is no line. There is no possibility of back and forth. It's just something that... "is". It's only the fact we've given it a measurement scale, something that when applied with anything else can be humanly or naturally adjusted, that the idea of time travel comes to light in the first place.
There's another theory, which starts dipping its toe into religion-esque concepts and seems completely unplausible but not disprovable. What about if humans, at one point in the future, did discover time travel. All hell broke loose, either related (people constantly altering the future) or less so (something like global warming). The vast majority of the human race was killed. The remainder, in an effort to recouperate, went back in time to restore the Earth to its original natural status, free of all technology and vandals of time - kicked the device for time travel into the nearest pit and started copulating. Hell, maybe there was only one guy, so advanced in skill and everything, but NOT HUMAN, that went back, invented humanity, dinosaurs, and all other life forms. Maybe he was called Godfrey. But, in effect, what I just said above prior to the time travel never happened. Maybe humanity today is the result of a process of perfection from repeated journeys through time.
Those that know me know I'm not a religious person. But something had to happen to bring us to where we are today, and when you don't believe, you owe it to yourself to speculate.
Any comments on your opinions of time travel (keep them as un-religiony as possible, please - unless it of course pertains to your theories) are more than welcome, and I will likely reply and share my thoughts on your own speculation.