The methods fictionally adopted for time travel range from a machine like Wells’ imagined, journeys through black holes, whipping around the earth or the sun, to a Delorean. In fiction, time is occasionally viewed as fixed and unchangeable, with the protagonist unable to change the past, no matter how hard he tries—as for instance in a few episodes of the Twilight Zone. This fatalistic view of time has been illustrated by a thought experiment: imagine going back in time and killing your grandfather while he’s a child. Not a very nice thing to contemplate, but it raises the paradox: if your grandfather dies before he has any children, that means that you’ll never be born. But if that’s the case, then who killed your grandfather? This paradox has been used to argue that time travel is either not possible at all, or else if you do travel to your own past, you’ll be prevented, somehow, from doing anything that creates such a paradox.
Other time travel stories assume that it is in fact possible to change the past, and such is what occurs in Mark Twain’s story. Thus, travel in time can be seen as potentially dangerous, with the past subject to alteration, either by bad guys intent on say making it so that the Nazis triumph in World War II, or by good guys who change something in the past either by accident or on purpose. Among those stories that assume the past can be changed, some see the universe as singular and moldable, while others see not one universe, but an infinite string of alternative parallel universes. With parallel universes, a change in the past does not wipe out the future that we all know, but instead shoves the changer into an alternate reality. His home universe remains, but is now unreachable. For him, there might as well be just one universe. Such is pretty much what we see in most fictionalized accounts of time travel, whether in Back to the Future or any of several Star Trek episodes.
So, can travel backward in time, the sort of things Wells speculated about in his novel, The Time Machine, become a possibility? Some physicists think so, but none are on the verge of developing a flux capacitor. In fact, something as simple to operate as the Deloraan in Back to the Future seems unlikely in most of the scenarios that serious physicists have projected. Most involve black holes or enormous spinning masses of neutronium. But recently, one physicist has come up with an idea that is relatively simple and might actually work.
Like something from a science fiction novel himself, the now seventy year old Dr. Ron Mallett is a physicist at the University of Connecticut. His father died of a heart attack in 1955 at the age of thirty-three. He was ten years old. The future Dr. Mallett bought the Classics Illustrated comics series of The Time Machine by H.G. Wells, when he was eleven, and he read it repeatedly. The story gave him an idea that has became his passion for almost sixty years. He decided that he would build a time machine so he could go back and save his father’s life. But he kept his plan secret, figuring that no one would take him seriously as a scientist if he let them know why he had become a physicist.
In 2000, after struggling to find a way, he finally published a paper outlining his theory for how time travel might be done. In 2007 National Public Radio did a segment on him. Two of the movie maker Spike Lee’s students heard about it and told him. Spike Lee then read Dr. Mallett’s memoir, Time Traveler: A Scientist’s Personal Mission to Make Time Travel a Reality. In 2008 Spike Lee decided to make a movie about Dr. Mallett’s life and has been working on the screenplay.
For Dr. Mallett to test his theory, he’ll need several million dollars. He’s been hoping that the publicity generated by Lee’s film might help get him the necessary funding to test his idea. Sadly for his hopes of saving his father’s life by traveling to the past, Dr. Mallett has determined that if his machine ever actually works, he will only be able to travel back to where the machine already exists. That is, if it becomes operational in 2016, time travel to the past would only be possible back to 2016. So someone from the 24th century could travel back to 2016, but no earlier than that. So perhaps that’s why we are not currently overrun by tourists from the future. They simply can’t get back to us since time travel hasn’t been invented yet.