h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

It's exciting to dream about travelling easily through time, and pondering all the philosophical implications. But I can't imagine it ever being possible as an everyday event, or on a large scale. I believe extremely small jumps have been made on a sub-atomic level. Perhaps this technology will develop and become useful, but probably for transporting abstract information or so, rather than a tangible object. If time travel ever became possible, anyone who travelled back from the future would possibly be observed in our past or present, and so we would know that time travel is going to become possible in the future. But perhaps they have come back, and there was no way to perceive them. Or they were confined to institutions for the insane. Or the people who saw and heard them were confined. If it were possible to go back and alter the past, the time traveller would have 100% responsibility for re-creating an alternative future. To travel into the future would be frightening - we would have no way of knowing how to prepare ourselves for whatever we may see.

I like to think that the classic "saucer" UFO is a history class from the future on an outing...