If time travel was ever invented, someone would have come back in time and we would have recognized them. If i ever invent time travel, i will return to this spot right now. *pause* I guess time travel will never be possible. Even if they invented some way of cloaking and forced people to use it, what are the odds that in our infinite future nobody will ever make it back in time without their cloaking? The knowledge would eventually spread to people who wanted it to be revealled in the past and we would know about it. Thus i conclude that time travel will never be possible.