Of Christmas stories, A Christmas Carol is the most famous and most duplicated.  The Internet Movie Database lists over fifty films related to that title, ranging from a 1914 version to an anticipated new release in 2010.  Notable and unusual versions are worth mentioning.  Mr. Magoo's Christmas Carol captures the story fairly accurately in animated form, including much of Dickens' dialogue, without being too frightening for children.  The kid-friendly The Muppet Christmas Carol starring the reliable Michael Caine tells the story playfully, with their own humor laced into the tale. The creative Scrooged has Bill Murray as the modern television executive version of the man whose very name has become synonymous with "miser".  Rich Little's Christmas Carol debuted as an HBO special, in which the master mimic played all the roles memorably as famous celebrities in the parts.  Everyone from Bugs Bunny to Blackadder to Barbie to Big Bird to Brer Rabbit has tackled the story in one way or another, with varying degrees of quality.  The 1951 Scrooge starring Alastair Sim is widely regarded the best of the live action versions.  Now in 2009 Disney, whose 1983 Mickey Mouse version was everything that name implies, has released a new version directed by Robert Zemeckis and starring Jim Carrey and a host of familiar names, which will be our subject next time, and will suffice as a consideration of the time travel effects in the essential story.

The other well-known Christmas movie involving time travel is It's a Wonderful Life, in which George Bailey (played by Jimmy Stewart) has his life erased from history, as if he had never been born.  Labeled a flop by the studio which originally released it, it has been listed as one of the top one hundred American films, and airs every Christmas.  There have been at least two remakes of this, one made for TV under the title It Happened One Christmas, the other A Very Merry Muppet Christmas Movie with Kermit the Frog seeing what the other Muppets would have become without him.  The Family Man with Nicholas Cage is also based on the same concept, but that it examines what would have happened had he stayed with his college girlfriend.

Since Charles Dickens penned his fantasy ghost story A Christmas Carol, it has become one of the great classics of the holiday.  Stage and film versions have been common, with some of the memorable versions discussed above.  Now in 2009 Disney has released a new version directed by Robert Zemeckis and starring Jim Carrey and a host of familiar names, most in multiple roles aided by heavy makeup, period costume, and an animation process that takes the live actors and distorts them just enough to make the characters seem at home in the largely animated world.  Although that is the version we will be examing, nearly all others follow the basic story line closely enough that the time travel elements of any one are largely consistent with the others.

The new version comes in standard, 3D, and I-Max.  If you suffer from motion sickness, avoid the 3D version or plan to close your eyes during the numerous high-speed flying and running scenes.  Carrey is surprising in the role, as the entire story is played very close to the book, with no added comedic lines.  It makes excellent use of his ability to do realistic falls and similar physical tricks, but uses these mostly seriously.  Wisely, Dickens' dialogue is largely preserved.  More impressively, the film is frightening at what is likely the level at which the original book might have been to the original audience.  There are only a few places, mostly surrounding Fezziwig's party, where the impossible happens without supernatural intervention, and these are small impossibilities common in cartoons.  This is not another Muppets version, but is presented seriously.  It is overall very well done.

Most readers already know the storyline:  after displaying his miserly character, Scrooge is visited by the ghost of his deceased partner Marley, who warns him that three more ghosts will haunt him with a view to saving him from Marley's fate.  The three spirits then show him views of Christmas past, present, and future, and it is here that the time travel appears.

It is usually time travel to the past which creates problems.  Dickens covers that well, though:  the past is shadows of things that were, unaware of the visiting observers from the future, and thus they change nothing.  It is merely Scrooge's present memory that is altered, the trip to the past serving to recall who he once was and how he changed.

Time travel to the future does not create problems, except as connected to a return trip; that is where the problems arise.  Scrooge is taken to see a Christmas on which he dies, and struck by how little anyone cares.  This view of himself he takes back to the present, and so alters his conduct to escape it, to change the future he has seen based on the information he gained from observing it.  More complicating, he sees the "present" Christmas Day, the day which when he goes to bed had not yet happened and when he arises had still not yet happened, and we are forced to wonder whether the Ghost of Christmas Present carried him to the future and back, or whether he lived through that day, met the Ghost of Christmas Yet to Come at the end of the day, and then was sent back to Christmas Eve.  Either way, when he awakens he immediately begins changing the future based on his knowledge from the future:  the Cratchits will eat turkey, not goose, and he interrupts the game of Twenty Questions in which he would be the butt of the joke to join his nephew for dinner.

Logically, if he has changed the future, he has erased the source of his knowledge.  The ghosts now cannot have taken him to see what now will never have happened.  Without that vision, though, he will not change, and thus under replacement theory we have an infinity loop.  We fare slightly better under parallel and divergent dimension theories, as we can assume that Scrooge saw the future of one universe but lived that of another.  That, though, leaves a universe in which Scrooge never changes, which seriously undermines the point of the story, that it is never too late to repent.

The solution lies in Scrooge's question:  is this what will be, or what may be?  He is not seeing the future; like in Minority Report he is seeing the most probable future based on the present at the moment he leaves it.  The information he receives alters the probabilities after that moment, and so the future is altered without changing the fact that at that moment in the past a different future was predicted.  Scrooge is saved, as is the story.

Apart from the many versions of A Christmas Carol, the Christmas movie most recognizable for temporal tinkering is It's a Wonderful Life, Jimmy Stewart's box office flop that has been revered as one of the best films of all time.  In it, George Bailey wishes he had never been born, and thanks to the intervention of the angel Clarence he gets to see what his wish would have meant.

The film begins by telling snippets from the life of George Bailey, as he saves his brother from drowning, prevents the local pharmacist Mr. Gower from making a deadly error in filling a prescription, meets and marries the wonderful Mary, saves the savings and loan association so the evil banker won't destroy the town, and in general makes sacrifices himself for the benefit of others.  It leads to a moment when that evil banker manages surreptitiously to steal money needed to keep the savings and loan solvent, and George despairs of life.  He would have committed suicide had the angel not intervened, throwing himself in the river so George would rescue him.  Then when George is blaming himself for the present crisis, Clarence changes the past such that George Bailey never lived.

It might be argued that this is not a time travel film.  After all, no one travels through time.  George Bailey does not watch events unfold without him.  Rather, he finds himself abruptly in a world in which he never existed, in a world in which the things he did were never done because he was not there to do them.  History has been changed; it was changed based on George's wish, although George did not travel to the past to change it.  Clarence changed the past; he did not travel to the past to do it, but he did reach back into the past and cause the change, based on information in the present.

It thus might be argued that this is a grandfather paradox.  George has not exactly killed his own grandfather, but he has undone his own existence, and now he does not exist to make the wish that does this.  We ought to be trapped in an infinity loop, since undoing George's existence undoes the reason for undoing it, and so undoes the undoing.  In fact, if George was never born, he should not be able to know what the world would have been like without him.

It might be resolved by adopting a parallel dimension explantion:  George has moved sideways into a universe in which he never existed, and then returns to his own universe after an hour or so of studying that world.  It means that the bleak dreadful world without George Bailey also exists, though, which is not the message the movie intends to send.

It seems the best explanation is a divine one.  God knows all the worlds that might have been, and could show George one of them without destroying what is or requiring that what never was must be.  Clarence is, after all, an angel, God's messenger to help George, so tapping such divine perspective is not entirely unreasonable.

There are a few points in the story that might be challenged.  Most of them concern the notion that the absence of George Bailey would not have been filled by someone else.  Mr. Gower probably would have hired a different assistant, and that assistant might have recognized the mistake as easily as George.  Granted that Harry drowned, the air force would have had some other pilot in his place, who might have been that medal of honor winner who rescued the men Harry was not there to save.  Someone else might have saved the savings and loan.  Mary might have married someone else.  Still, it is not certain that anyone would have stepped into these roles, and the alternate history is at least credible.

The film works under a version of replacement theory that allows for the divine intervention suggested by the plot, and also under that version of divergent dimension theory in which every possible universe exists and George can travel sideways to the present moment of another.  It is also a solid inspirational story that should make most of us feel as if we may have done more good in the world than we can see at this moment.