Call me a wet blanket, but I must point out certain difficulties in the whole concept of time travel. Now I know that people love stories of time traveling, either forward into the future or back to the past, and many often speculate about it happening in reality. There have been countless films, television shows, books, comic books, commercials, cartoons and who-knows-what centered on people traveling through time. It would certainly be nifty if it were a reality, opening up all kinds of interesting possibilities and complications. Unfortunately, I don't think it can happen without overcoming some major, seemingly insurmountable problems. And by the way, it isn't nice to use the term wet blanket to describe somebody, so I take back that first sentence.
Suppose a person, we'll call him Harvey, wants to travel back in time, to 1860, to warn President-elect Abraham Lincoln that he is in grave danger of looking silly if he grows a beard without also growing a mustache. And suppose Harvey also has what is thought to be a working model of a time machine. The first thing he should do is to put it in a vehicle and drive it to Springfield, Illinois. That way, he doesn't have to lug the thing across country on horseback or on a train. Then, Harvey goes to a field outside of town, but within walking distance of Abe's place. There he dons the helmet, protective suit, goggles and gloves that come standard with the time machine, and sits on the seat inside the machine. He fires it up and sets it for "Right here, November 1860" and pulls the switch.
Here is where one of the biggest problems of time travel rears its ugly head. "Here, November 1860" is a place in the universe where Springfield is when Harvey pulls the switch. However, this place in the universe back in 1860 did not contain Springfield, nor even the Earth. The Earth was not here yet. It was immeasurably far away, rotating around the Sun, spinning on its axis in the solar system, part of a galaxy hurtling through the universe at high speed, only ending up here at the very moment he pulls the switch. Unfortunately for Harvey, when he pulls the switch he gets sent, not to the field outside Springfield, but to a lonely spot in outer space, empty, airless and pitch black. He's dead. And none the wiser, Abe Lincoln never grows his mustache, and the body of poor Harvey just floats around in deep space forever, or until the Earth smacks into it in the 21st Century.
The point is that a time traveler is sent to a time and a place, and the place on Earth that he's aiming for is nowhere near the spot in space that it occupies in the present. How can he go to where the Earth used to be? Isn't it enough of a problem just devising and building a machine to take you to a different time? Now you've got to make sure it sends you, with pinpoint accuracy, to a different part of the universe. The mind boggles, as well it should.
So any machine that travels through time must also travel through space, too. But suppose, (you retort, haughtily) such an amazing technology is invented and that the machine can actually send the traveler to the correct spot in the universe? Where's the problem now, Mr Fishbrick? I don't know, Haughty Questioner. How good is your machine? What if Harvey goes to that field outside of Springfield, his
special suit filled with brochures depicting comely mustaches, he pulls the switch, he goes to the exact right time, 1860, and to the exact right space in the universe, on Earth, where it was then, in Springfield. But then it turns out that back then, in that exact place, there sat a majestic elm tree, wind wafting through its branches. And now Harvey and his time/space machine and the elm tree are all somehow melded together as one - a horrifying half-man, half-machine, half-tree, half-mustache brochure; too many halves for one space. It's something too awful to contemplate, even for an alleged wet blanket like me. How does your machine overcome a problem like that? Or perhaps Harvey travels ten thousand years into the future, but what was once a field in Springfield is now a hill, and he is engulfed deep inside of it. Or it is now a lake, filled with hungry piranhas, and nobody thought to make his special suit nibble-proof. What if Harvey goes way back in time and ends up with his head inside a mastodon who just happened to be wandering by, minding his own business?
