December 31, 2007

Closed loop or branching streams?

A good portion of my Christmas vacation was spent with good books. In this case, I finished the "Giants" trilogy, written by prominent sci-fi scribe James P. Hogan. The trilogy is a remarkable past and future history of the human race which is shown to have extraterrestrial origins. The ending of the third novel postulates a "closed loop" timeline which I have found to be in the minority when it comes to instances time travel in entertainment. "Closed loop" essentially is designed to keep all events within a timeline internally consistent. Another recent novel I read which makes use of closed loop time geometry is Joe Haldeman's The Accidental Time Machine. A truly excellent "alternate history" novel which likewise uses closed loop time is Orson Scott Card's Pastwatch: The Redemption of Christopher Columbus.

I've noticed there are essentially two ways to deal with closed loop time adventures: The need to keep events within the loop consistent; second, if there are major changes to events within the loop, events preceding the changes cease to exist in favor of the new events created. Pastwatch did the latter to a tee. The Accidental Time Machine demonstrates how to do the former, as anything from the future that ends up in the past is actually responsible for events that transpire in that timeline's future. Make sense?

Most sci-fi (at least that I've read/viewed) uses the "branching timestream" theory of time travel. This is where any change in a timeline creates a whole new reality. There are an infinite number of such realities in the "multi-verse" all based on the different decisions and actions that people make at different times. "Back to the Future 2" was an excellent example of a "branching" timeline based on changes made to the past. Many "Star Trek" stories have tried to have it both ways when it comes to explaining how time works. The classic "City on the Edge of Forever" showed how Kirk had to let a woman he had fallen in love with die to "preserve" the timeline. Last night, SciFi Channel replayed the eighth Trek film, "First Contact" where the new Enterprise-E had to travel back in time to the date of Earth's first warp flight to stop the dreaded Borg from changing history. "Deep Space Nine" had a superlative two-parter where Captain Sisko had to "preserve" the timeline by assuming the role of a pivotal revolutionary figure. Yet, we know that alternate timelines exist throughout the Trek universe. The "Mirror" Universe, for example (which has been utilized by three of the five Trek series), details how Earth became militaristic conquering empire. (Besides the original -- and great -- "Mirror, Mirror" I highly recommend "Enterprise's" last season "In a Mirror, Darkly" two-parter.) The necessity of excising a disastrous timeline occurred in "Next Generation's" "Yesterday's Enterprise." What was intriguing about this episode was that it appeared a change in the past (in this case, the Enterprise-C was catapulted into the future, the time of the Enterprise-D) completely changed the future as we see Capt. Picard and the bridge crew undergo a transformation right before our eyes as the Enterprise-D's predecessor appears through a time rift. This would indicate to me a closed loop time geometry; however, when character Tasha Yar from this new timeline elects to go back with the Enterprise-C's crew to their appropriate era, this in itself indicates a branching timeline theory since, notably, Tasha had been killed years before in the TNG timeline, yet now she existed -- and went on to affect events in later TNG episodes.

The list is endless, of course. I could write for hours about how various novels and movies have made use of both techniques. For me, this is great entertainment, but trying to make sense of it can sure cause some headaches. Perhaps this is why Einstein (among others) stated that travel into the past is impossible. Personally, I feel this a great conceit considering our pitiful level of knowledge in the whole scheme of things. If we can conceive of it -- and there are scientific models that do allow for journeying to the past -- then I believe ultimately we can make it a reality. I sure would like to be around when we finally solve the riddle of how precisely the time-stream functions.

Posted by Hube at December 31, 2007 05:10 PM | TrackBack

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Hube
I think the most interesting thing about reading time travel stories is almost always trying to figure out whether they will use branching timelines or a closed loop--usually it is the key to figuring out the ending. There is a lot of speculation now that the grand unified "theory of everything" may require that time does not exist in the lineal form that we seem to experience it. Unsettling as it seems, most quantum cosmological equations seem to work equally well with time running backward toward the Big Bang or forward from it. Are cause and effect only artifacts of our sensory perceptions and the hard-wired limitations of our brains?

Who the hell knows?

Yesterday's Enterprise was one of my all-time favorite episodes because it cut you no slack whatsoever. You had to figure it out alongside the characters.

From the realms of written SF, my favorite works on time travel that you didn't mention are:

Robert Heinlein's closed loop classics "By His Bootstraps" and "All you Zombies"

Jack Chalker's "Downtiming the Night Side"

Keith Laumer's "Dinosaur Beach" [I think Laumer influenced Chalker, as a matter of fact]

Wilson Tucker's "Year of the Quiet Sun" and "The Lincoln Hunters"

John Barnes' "Kaleidoscope Century"

Steven Baxter's "Timelike Infinity" which cannot be read without also reading the sequel "Ring"

Barnes and Baxter both use the best known mechanism currently believed to be possible, that of dragging one end of a stable wormhole light years away from the other and then entering the far end. The only problem is that you can use the wormhole to travel forward or backward in time but never further back than the original creation of the stabilized wormhole. (But what if somebody, a billion years ago, left a stabilized wormhole hanging around; happens all the time in the Star Trek universe.)

One of the questions I have been playing around with serious as a historian is the concept of quantum history. Perhaps even on a human scale multiple possible histories do not coalesce until we cause them to do so. Think of the Schroedigger's Cat experiment, and then consider what I call Schroedigger's Manuscript.

On his way back from his first voyage to the Western Hemisphere, it is known that Columbus had the opportunity to make contact with the King of Portugal prior to returning to Spain. Did he tell the King information that later led Portugal to steal a march and land in Brazil? Long debated but never known for sure.

What if you knew there was a manuscript locked in a box since 1493, in Columbus's own hand that answered this question. Until you opened the box the chances would be 50-50 either way. Conventional thinking says opening the box would just tell you what HAD happened, and that what HAD happened had done so no matter what you knew.

But since our worldline could exist as it does today with either possible history (he tells or he doesn't tell), then quantum history would say that by opening the box you pin down one of the histories and the cat (remember him?) dies.

If Stephen Hawking can jump the "sum over histories" argument from the quantum to the cosmological realm, I don't know why it wouldn't make a stop in between at a human scale.

Posted by: Steve Newton at December 31, 2007 09:29 PM