What is the Grandfather Paradox?

*Originally published on 3/5/12



Stories about time travel can often prove frustrating. You go along with the story and then something happens and you start over-thinking things. Soon you find yourself going in loops trying to figure out how it would work.

This frustration would later be embodied in something called "The Grandfather Paradox". While it may sound overly scientific, the general concept is pretty straight forward.

Essentially, the paradox presents a scenario where a person goes back in time. Maybe they're like the Doctor from Doctor Who and just want to look around or maybe there's some wrong that needs to be made right. In any case, during the traveler's stay, he or she kills their grandfather.

Whether it was by accident or on purpose doesn't really matter. Who knows, maybe they never even meet their grandfather, but their presence triggers some long Rube Goldbergian chain reaction that results in his death.

This proves problematic as, if the traveler's grandfather dies before he's supposed to, then he never gives birth to your parent, which means you were never born. Now, while it's possible that he could have already given birth to your eventual parent depending on when you meet him, for the sake of the theory, it's assumed that he hasn't borne a child yet. In this case, the traveler was never born, but if that happens, then how is he able to go back in time and kill the grandfather in the first place?

See? It becomes a mess. Try as they might, writers still haven't been able to think of a way out of this paradox. In his recent novel, 11/22/63, Stephen King hand waves the idea early on. The main character asks about that possibility, only to be met with the simple question of "why would you do that?". It's a funny line, and it was probably King's way of saying "don't over think this", but it avoids the actual concept behind the scenario.

The classic film, Back to the Future also deals with this paradox in a sense. Through no fault of his own, Marty McFly interferes with the courtship of his parents. As they never met, he was never born. Slowly, but surely, Marty's future family is erased from the timeline. He has to set things right before he fades away too.

As Marty sets things right, it becomes moot, but one does have to wonder why it took so long for Marty to be erased outside of plot convenience. In theory, he should have vanished instantly, no? Besides, the same problem comes up. If Marty is erased from the timeline, then he never went back and meddled, which means that his parents did together, meaning that he could go back and meddle and, yeah this could go on forever.

Time travel, and the futile endeavor of trying to wrap your head around it, is a nuisance. Even when it is well thought out and consistent, there are still paradoxes and headaches to be had.