The most common objection to science ever developing any form of time travel is called "the grandfather paradox" -- i.e. the ability to travel in time would mean, theoretically that you could kill your own ancestors, thus preventing your own birth. Indeed -- so the argument goes -- by altering any of the ingredients of the past, even by so much as the flutter of a butterfly's wing, you would inevitably change the present. Since the present manifestly exists, and is as it is, then obviously time-travel cannot occur.
In a recent (July 2010) paper at arXiv.org, Seth Lloyd of the Massachusetts Institute of Technology notes that fiction has been grappling with these problems for far longer than science, but that even most fictional accounts, going at least as far back as the Mahabarata epic of ancient India, deal with travel into the future. "Perhaps because of the various paradoxes to which it gives rise, the concept of travel to the past is a more recent invention," says Lloyd, pointing to Charles Dickens' A Christmas Carol and Mark Twain's A Connecticut Yankee in King Arthur's Court. "The contemporary notion of time travel, together with all its attendant paradoxes, did not come into being until H.G. Wells masterpiece The Time Machine, which is also the first book to propose an actual device that can be used to travel back and forward in time."
To get around the grandfather paradox Lloyd and his co-authors suggest quantum teleportation and strict "post-selection" of what a time traveler could and could not do -- i.e. killing your own grandfather would be ruled out from the post-selected options and if you did succeed in killing the person who you thought was your grandfather this would have to mean that he was not after all your grandfather and that your grandmother had perhaps had an illicit affair!
Another recent paper (18 August 2010), published by Robert Lanza MD in the Huffington Post, draws on the latest research in quantum physics to go even further. We live in "a world of illusions" Lanza suggests: "Physics tells us that objects exist in a suspended state until observed when they collapse into just one outcome. Paradoxically, whether events happened in the past may not be determined until sometime in your future -- and may even depend on actions that you haven't yet taken."
In other words events in the past are in a suspended state, with infinitely flexible outcomes, until they are observed. Only then do they collapse into fixed and firm historical "facts." Lanza illustrates his point with reference to the assassination of JFK: "There's enough uncertainty that it could be one person in one set of circumstances, or another person in another. Although JFK was assassinated, you only possess fragments of information about the event. But as you investigate you collapse more and more reality..."
I follow weird research like this because time-travel -- specifically to the Stone Age around 24,000 years ago -- is a central element of Entangled: The Eater of Souls, my first work of fiction. Unlike Jules Verne, however, I do not propose a time-machine as the vehicle. Rather my modern characters gain access to the remote past during out-of-body experiences induced by the consumption of psychoactive drugs such as DMT, psilocybin and Ayahuasca (see my previous essays here on Boing Boing).
At stake is the fate of the Neanderthals, an extinct human species and - through them - of mankind as a whole.
As I reported in Friday's essay we know that the last Neanderthals died out around 24,000 years ago but we don't yet know why this happened. There are indications that our own anatomically modern ancestors who co-existed with them may have wiped them out -- perhaps the first example of ethnic-cleansing in history -- but we don't know for sure. In other words, the fate of the Neanderthals has not yet been observed, is indeed surrounded by even more uncertainty and even more "uncollapsed" reality than the JFK story, and therefore may still be influenced by actions we take now.
This is the central dilemma and jeopardy of Entangled. In my story the Neanderthals are highly-evolved spiritual beings, pure innocence and love. Their goodness is a raw cosmic power that has attracted the attentions of a terrible demon. If he can persuade our own anatomically modern ancestors to exterminate them, then the psychic charge he gains from their mass murder will allow him to manifest physically in the twenty-first century and weave the doom of all mankind. To prevent that my modern characters must travel through time to confront the demon and ensure that our ancestors do not make this terrible mistake.
As the latest in a long line of storytellers to grapple with such problems it's good to know that science fact and science fiction have never been closer together. In the lab as well as in novels we may yet hope to rewrite our own past.