The Time Travel Fallacy, part 1

This is the first in a multi-part mini-series on time travel. I plan to release three segments--one per week--over the next several Tuesdays. However, that's not a concrete situation, and I may add more if more aspects of interest arise.

Time travel, as I see it, has a few problems. I'm not going to wade into any physics issues, or the concern about the ability to surpass the speed of light, but rather simply discuss a few issues that I perceive in a metaphysical manner. There are two specific issues, possibly mutually exclusive, with time travel in general. Because of the length of discussion that can go with each, I've chosen to break this post up into three parts. The first will concern how any changes that are made via time travel would have already occurred in the present from which the time traveler came. The second part will discuss the argument that, if time travel were possible, how come we've never exposed anyone in history to be a time traveler? The final segment is slightly different, briefly examining the implications of time travel for the person doing the traveling. Without further ado, let's dive into the first issue.

Issue 1: Changes made in the past would already be perceived in the future as "normal," and hence no changes could subsequently be made.

Roads? Where we're going we don't need roads.

There are dozens of movies, books, and TV shows that use time travel as a main plot tool (and, as it turns out, many more TV shows that use time travel as a device in at least one episode). The most common situation has the protagonists going back in time to interact with characters that are presumably baffled by the appearance and existence of the time travelers. However, under the theory of time travel to which I subscribe, none of these stories would go quite as they're depicted for one key reason: time travel that changes a past reality in any way will be reflected in the future from which the time traveler came, and thus whatever changes he or she may make in the past would have already happened in the reality as it exists in their contemporary time. 

This doesn't mean that one can't necessarily change something through time travel. I think it's silly to say that, if time travel is possible, one cannot actually perform any action in the past that would have a future effect. But you can't have the present exist in one form, go back in time, and return to a completely different present--at least, not in the "universe" that the previous present exists in.

What does this mean? Stay with me, because I fear I'm losing you, if not myself. Let's look at an example in order to try and hash it out. If I'm disappointed that I'm not financially well-off in the present (2012), but I inexplicably also have access to a time travel device, I may decide to go back in time and set myself up with some great investment. I could go back to 1980 and buy into the Apple IPO, reaping huge rewards when I return to 2012. Sounds good, right? Well I don't think it's quite that simple.

First of all, from a purely economic perspective, if this could be done, people would flood back in time to invest in things that turn out to be big, and as we see, not many people actually have the foresight to start early on with a big winning investment (i.e. we would probably see many more people win big in great investments). Similarly, people would pull this trick with Powerball by learning the numbers and going back in time to buy the winning ticket. Not only would this ruin the value of such lottery games, it would have been noticed by now (to be discussed in segment two).

Now, to examine the example from a time travel perspective. Let's say I have a time machine and use it to go back in time and buy into Apple. I also have a friend who agrees to run the machine and wait in my basement, manning the controls while I'm gone (although if performed correctly, I should return to the present at the same time I left, or even before, which could open up a whole different can of worms). How does that friend perceive this supposed shift in the "truth?" It's easy for one to picture the change from the traveler's perspective, because the time travel event functions as the change point, where on one side I don't have the money and on the other I do.

But for people who are in the present, how do they see it? Do I return from my trip (imperceptibly, as I said) and he suddenly knows I have several million in my bank account? Where does the trigger event happen where he goes from "knowing" I'm broke in 2012 to "knowing" I'm rich in 2012? Nothing will have changed for anyone who didn't make the trip, right? Perception of events as they exist (or passed before) are pretty black and white. My friend, who knew about the time travel mission beforehand, will not be able to perceive the difference between "before I left" and "after I got back." No time will have passed in his perception, and there will be no triggering event for him.

It is partially for the above reason, a paradox of sorts, that I have trouble conceiving of time travel. To people who did not make the trip (if indeed such a trip is possible), there is never a trigger moment at which reality changes. Assuming, arguendo, I succeed with my Apple IPO mission, from my friend's perspective (as well as everyone else's), I have always had the fortune I gained in 1980--just as Oceania has always been at war with Eastasia.

I suppose this isn't to say that changing events isn't possible. All it says is that events that are changed will have always been changed, and hence no change will be made. This subtle distinction may in fact be self-defeating, because if any time travel changes will have always been "reality," how will I know to go back and change them? In a circular way, if I go back in time to change something, it will never have existed in any other way upon my return, but if it never existed, how can I need to change something, hence what purpose would time travel serve?

To avoid tying my brain in any knots, I'll end here. But after parsing all of this out, it appears to me that time travel--at least for the purpose of changing past events--is not plausible. If changes made through travel are imperceptible in the "new" present, and have always been as they become after the trip, how can one time travel to make those changes in the first place? I also avoided getting into the "multiple universes" theory of time travel and teleportation, because that will make heads explode.

The post is best read with this song playing in the background.