From childhood I've been fascinated by the idea of time travel. My first exposure to the concept was the moment Superman turned back time in the 1978 Richard Donner film. Later I got into superhero comics, in which several superheroes and villains travelled in time, usually with extreme consequences. On television I enjoyed Voyagers and Quantum Leap. Then I participated in a lengthy role-playing game campaign in which the main character was a being called a Time Elemental.
There have also been a number of movies featuring time travel by various methods. The Time Machine, Time Bandits, The Terminator, Back to the Future, Star Trek IV The Voyage Home, Bill and Ted's Excellent Adventure, Timecop, 12 Monkeys, Star Trek First Contact.
And of course, there's the time travelling grand-master: Doctor Who.
All this leads to the question: what would happen if time travel were actually possible? Who hasn't dreamed of going back in time to meet a deceased relative, to see dinosaurs up close, or to kill Hitler?
But let's be realistic for a moment. Assuming that time travel was achievable, access to such technology would be limited to governments, military groups, and maybe scientists. Not just anyone would be allowed to use such a powerful device. Not to mention we'd probably have another Cold War as other developed countries tried to acquire the same technology in a kind of time-race.
There are many theories about what might happen if someone could travel in time. There is a claim that the mere act of travelling in time would change reality, no matter what the person did. Chaos theory postulates that a small change at one place can result in large differences later; in other words, one tiny misstep in history could devastate humanity as we know it. Or nothing might happen at all: a person's presence at a particular time and place was meant to happen anyway. We have no way of knowing.
There are other theoretical dangers too. In a video game called Ratchet and Clank Future: A Crack In Time, time travel technology was gifted to a race so they could better themselves. However the technology was misused to the point where a tiny hole occurred in the fabric of space-time, causing the destruction of numerous planets. In an episode of Star Trek the Next Generation, it was discovered that the use of warp drive propulsion (which is effectively time travel) was causing damage to space-time.
We are three-dimensional beings. No matter how intelligent we are, truly understanding the fourth dimension is most likely beyond us. But we can still dream, right?