Thursday, November 12, 2009

A Tale of Time Travel

Saw something recently that tickled my funny bone, in an intellectual sort of way, and thought I'd share it with y'all.

Background: My wife has somewhat unusual tastes in entertainment fare, when compared with most of female-kind in this country. She's one of those types highly-sought-after by us geeks, who actually enjoys science fiction. She once went to a Star Trek convention, and was mistaken for being in costume. Yup, she had just dressed in what for her was normal street-clothes, which happened to consist of a very 80's-style red jumpsuit with black turtleneck and black boots, and she just happened to be mistaken for one of the women in Khan's posse....

Okay, she enjoys more than just science fiction; she has enough girlyness in her that she occasionally watches the 5-hour BBC Pride & Prejudice miniseries that we have on DVD. Still, she doesn't usually go for the really weepy stuff. She likes explosions.

And big muscles.

(Hmm. Makes me wonder... How'd she wind up with me? Must be the potential for explosions....)


Ahem. Anyway, her favorite sci-fi sub-genre is Time Travel. Yup, she loves stories where people go back in time and accidentally cause themselves not to be born. Or they become their own parents or something. Pretty much, the more convoluted the story, the more it makes your mind bend just thinking about how they got themselves into this mess, or how they're going to get out of it by the end of the hour, and she's there. She was a big fan of the time travel stories on Star Trek; she was a big fan of Dr. Who; and she loved Bill and Ted's Excellent Adventure (a judgment with which I heartily concur).

So of course, I had to share the following news with her when I saw it online the last few days. It gave her a bit of a smile. Hopefully it'll do the same for you.


But first, I have to pose a time-travel thought experiment.

Suppose someone builds a time machine, and uses it to go back into the past. What would happen?

Well, there are two schools of thought. One is that the timeline doesn't change, because everything the time traveler does when he gets to the past already happened. If the time traveler loses his wedding ring in the past, his contemporaries from his home year will be able to find it exactly where he lost it. In fact, someone may have found it already, in the intervening years between when the time traveler lost it in the past, and when he started out on that journey in the future. Under this school of thought, the time traveller can't do anything that wasn't already done before.

A good movie that appears to take this approach is Bill & Ted's Excellent Adventure. ("Trash can... remember a trash can!")

The other school of thought is that the time traveler can in fact change the past, and by doing so will change the future. This is the school of thought on display in the Back to the Future movies. Marty has to fix the past before he goes home to the future; otherwise, since he accidentally broke up his parents, he would cease to exist.


Well, just for kicks and giggles, let's assume that the latter of these scenarios is true--that a time traveler from the future can change the past to something different from what happened in the time traveler's history. What then?

Since I'm a geek, allow me to go to the diagram.
Let's say the above diagram represents a time-line. Now, let's say that a time travel experiment is started up that makes changes in the past.

So far, so good. The trouble is, since the past has changed, that means that the timeline diverges; from the moment in the past that the time travel experiment makes something different happen than what went before, the time line has changed--and the remainder of the original timeline, the one on top in these diagrams, never happened.

So really, only the bottom timeline exists anymore. And it is identical to the first timeline, up until the point where the time traveling object appears (seemingly out of nowhere, as observed by people in the past). From that point on, the timelines start to diverge.

Now here's where the fun begins. The timeline is now proceeding differently than it did before. This may in fact cause changes to the circumstances of the time travel experiment itself! What happens then? Well, that experiment will then be run at a slightly different time, and send its payload to a slightly different time in the past, causing yet another timeline to form (and voiding the remainder of the timeline we just constructed, too). And then this timeline will cause changes to the circumstances of the time travel experiment, causing yet more changes in the past....
Now, it seems to me that these alterations to the past timeline would accumulate; they wouldn't necessarily void each other. If the first experiment puts a bowling ball back through time, that changes the timeline; then the next iteration puts a nectarine through instead, what then? Well, since the timelines are identical up until the point in time that the time travel causes them to diverge, it means all the old alterations would still be there as well--including the bowling ball. (Though I'm certainly open to the idea that someone with greater powers of logic than me will come along and contradict this point. If I'm really lucky, maybe he'll come from the future!)
So what's left? Well here's the catch. Ever heard of the "Butterfly Effect"? Any change to a chaotic system, no matter how minor, causes little changes... which cause bigger changes... which eventually cause the system to look completely different than it would otherwise have been. This has long been a bugaboo in the world of weather forecasting. The problem is that weather systems are so sensitive to initial conditions, that missing the tiniest cause--like the flap of a butterfly's wings--will eventually cause the predictive model to yield wildly inaccurate results. The addition of that butterfly's wing flap could result in a hurricane showing up at a different time and place than it otherwise would have, for instance.

But don't we have the same thing in time travel? One minor change sends out eddies and ripples into the timeline, which grow--uncorrected--until the future looks nothing at all like it would otherwise have been. And this huge loop of time-travel changes, with each iteration changing the past, and in turn changing itself, would be dumping an awful lot of unpredictable, disruptive factors into the past.

Eventually, something is going to break. Rather, one of these changes will--through random chance--cause a tornado to hit the time travel research lab. Or will cause the wrong congressman to win the election, who decides to cut the research funding. Or will cause a giant fire-breathing turtle to appear and devour the lead scientist.

After all, this time-travel cycle can happen an arbitrary number of times, and is guaranteed to go on until the cycle is broken--by some sequence of events that stops the experiments. Then, you have a stable timeline, with no more loops.
Now, this timeline will have a lot of seemingly-odd, highly coincidental events in it, that to an objective observer just seem to conspire to shut down the experiment. Like that out of season tornado, followed by that crooked election, followed by that fire-breathing turtle. The observer might be tempted to think that God doesn't actually want us to discover time travel, right?

Either that, or God has an absolutely wicked sense of humor. And He's into slapstick.


So what would these "highly coincidental" events look like in real life, that would prevent time travel from happening?

Well, it might look a little like this.
Baguette Dropped From Bird's Beak Shuts Down The Large Hadron Collider (Really)

The Large Hadron Collider, the world's most powerful particle accelerator, just cannot catch a break. First, a coolant leak destroyed some of the magnets that guide the energy beam. Then LHC officials postponed the restart of the machine to add additional safety features. Now, a bird dropping a piece of bread on a section of the accelerator has, according to the Register, shut down the whole operation.


With freak accident after freak accident piling up over at CERN, the idea of time traveling particles returning from the future to prevent their own discovery is beginning to seem less and less far fetched.

Incidentally, I loved the comments on this article. I got a particularly good laugh from this one by HyMinded:

The bird's briefing:

The approach will not be easy. You are required to maneuver straight down this trench and skim the surface to this point. The target area is only two meters wide. It's a small thermal exhaust port, right below the main port. The shaft leads directly to the reactor system. A precise hit will start a chain reaction which should destroy the station.


But what's really funny to me--partly in a "ha-ha" kind of way, and partly in the Spock-eyebrow-amused kind of way, is just how many serious scientists are taking this kind of reasoning seriously. After all, my little exposition up above seems pretty tongue-in-cheek to me, but apparently no one can find the logical flaw in the thing that can break the whole argument down. Take a look at this article from Time describing the same incident, and tell me if that isn't the case.
While most scientists would write off the event as a freak accident, two esteemed physicists have formulated a theory that suggests an alternative explanation: perhaps a time-traveling bird was sent from the future to sabotage the experiment. Bech Nielsen of the Niels Bohr Institute in Copenhagen and Masao Ninomiya of the Yukawa Institute for Theoretical Physics in Kyoto, Japan, have published several papers over the past year arguing that the CERN experiment may be the latest in a series of physics research projects whose purposes are so unacceptable to the universe that they are doomed to fail, subverted by the future.

...But ever since the British physicist Peter Higgs first postulated the existence of the [Higgs Boson] in 1964, attempts to capture the particle have failed, and often for unexpected, seemingly inexplicable reasons...

In a series of audacious papers, Nielsen and Ninomiya have suggested that setbacks to the LHC occur because of "reverse chronological causation," which is to say, sabotage from the future. The papers suggest that the Higgs boson may be "abhorrent to nature" and the LHC's creation of the Higgs sometime in the future sends ripples backward through time to scupper its own creation. Each time scientists are on the verge of capturing the Higgs, the theory holds, the future intercedes. The theory as to why the universe rejects the creation of Higgs bosons is based on complex mathematics, but, Nielsen tells TIME, "you could explain it [simply] by saying that God, in inverted commas, or nature, hates the Higgs and tries to avoid them."
Yeah. That and the fire-breathing turtles.


Gary B said...

Of course, Higgs boson has been observed, and all of your divergent timelines exist simultaneously. You do accept the many worlds interpretation of quantum mechanics, right? I'll let you know if I spot your turtle.

Timothy Power said...

You mean there's actually a universe out there where I made it with Miss Zambrano? Um... must be nice. Then those darn time travelers had to go mess it up.

And I got your fire-breathing turtle right here.

(I loved those movies when I was a kid....)

Crimson Wife said...

Guess I must be one of those rare female geeks like Ms. Tonya, because I found your post hilarious!

Gary B said...

Oh, THAT fire-breathing turtle... Speaking of critters from another dimension, check out Dolores, an alopeciac bear in a Leipzig zoo.

B. Durbin said...

Female geeks are not rare, we're just more easily mainstreamed. I think.

Have either of you read Connie Willis' time travel novels, Doomsday Book (Hugo and Nebula Award winner) and To Say Nothing of the Dog? She has time travel given over to the universities because they can't change the past; there's a fudge factor called "slippage" that theorizes that when you send an historian (hey, it's Oxford) back in time, their destination time gets bumped enough to keep them out of trouble.

Of course, she has great fun with that in the second book, but it's a great concept for dealing with the grandfather problem.

(NB: Doomsday book is very sad but To Say Nothing of the Dog is all but a farce. Choose your reading accordingly.)