Thursday, September 22, 2011

Economics with time travel?


This is almost certainly an experimental error.  But in the meantime, why not entertain some Econ Time Travel Thoughts?

First of all, let it be known that from an economic perspective, time travel isn't inherently paradoxical.

Wait, but isn't it?  I mean, if you can travel back to before you were born and fiddle with things so that you're never born, but wait then how can you ever exist to travel back and fiddle with things, but wait then...

And doesn't time travel muddle causality in a pretty serious way?  I mean, if you're going back to yesterday to tell yourself that today you should go back to yesterday to tell yourself that today you should go back to...

A lot of people would throw up their hands, but we're economonomists so time travel doesn't scare us.  Time travel does muddle causality, but it does so in the same way that causality is always muddled in that most standard of economic concepts, the equilibrium.

When everyone in the class is cheating, who caused it?  Who is to blame?  Well why does there have to be someone to blame?  Why can't everyone just be reacting optimally (perhaps even socially optimally) to everyone else's behavior?  An equilibrium is a fixed point, where everyone's behavior causes and is caused by everyone else's.

A world with time travel can be in equilibrium too, of course.  Even if I go back to last week and deliver a message to myself, that message may be what causes me to behave precisely the way my present self is behaving.  And could I go back in time and mess with my birth, create paradoxes and whatnot?  Well, maybe the right way to think about it is that we just don't observe such out-of-equilibrium behavior.  It's not like -- as in many movies -- we exist until the moment we go back in time and mess with our past.  Rather, the whole history either is consistent with itself, or not.  If not, then what's to see?  Where time travel is concerned, you can refuse to believe in out of equilibrium behavior without being a stubborn classical economist.

I'm not saying there are many potential universes that support a time travel equilibrium, but they are certainly not a logical impossibility.  So we can safely consider the possibility of being in one ourselves, and we can safely imagine what some fun ones might look like.


Here's a fun one, by the way.  Has anyone seen The Time Traveler's Wife?  Spoiler alert!  Strictly from the perspective of economonomic time travel theory, it is a very good movie.  (If you're not into that stuff, you'll have to get your recommendations somewhere else!).  Most movies with time travel are, I think, of the "don't think about it too hard" variety...but this one displays, essentially, a stable time travel equilibrium.  What I most like is that it makes you check your causality judgment at the door, in the same way that earlier post about cheating is supposed to make you check your judgment at the door.

When Girl meets Guy for the first time in her life, she is like 7 and he is already in love with her, and he cultivates that relationship as she grows up, which you could say is kinda sick.  But on the other hand, when Guy meets Girl for the first time in his life, she is already in love with him and does the very same thing.  Due to the magic of time travel, there is no sense in which one of them initiated the relationship or caused it all to happen.  Hopefully you walk away from this movie recognizing that there are no fingers to point.  There is nothing here but a time travel equilibrium, a fixed point where everything is in perfect balance, whatever that balance may be.  There's a good deal of information flow to the present from the future and the past, but it always exactly enough to do exactly what it needs to do, namely to preserve the equilibrium.


  1. Sorry if this is not the right forum for this question (I'm quite new to this sort of thing), but I've started going through your past blogs and in one of them, you ask readers to shoot you an email. I'd like to, but can't seem to find your address anywhere. What am I not seeing?

  2. You should watch the independent film called Primer. The budget is low, but it really gets going and does not ask you to make any compromises when it comes to time travel. It's the type of movie that you will need to google when it's done in order to absorb everything that you just saw.