Murdering Grandpa and Other Time Travel Workarounds

(This is a piece I wrote for Medium.com a few months ago.  I'm rather proud of it.  For those of you who are unfamiliar, Medium.com is a lovely website where anyone can post articles about nearly anything.  I recommend you check it out.)


Time travel is always fun to think about. Who wouldn't want to go back in time to do things differently? You could make money with your knowledge of the future, put the moves on that girl you were too afraid to talk to, or murder your grandfather for no real reason. (Bear with me.) But according to scientists backwards time travel is not as straight-forward as one might think. I’m not talking about altering the past in a way that could drastically affect the future a la Ray Bradbury. In fact if I had to weigh what I stand to gain financially against the possibility of damaging the time continuum resulting in an alternate future where, let’s say, the United States is a communist country or the Keurig was never invented, I would probably throw caution to the wind and go for the money.

I’m referring to what scientists call the grandfather paradox. The theory goes like this: Imagine you travel back in time to find your grandfather before he met your grandmother. Unbeknownst to you, one of the side-effects of time travel is a thirst for blood, and you decide to shoot your grandfather, killing him instantly. By murdering your grandfather he could never have met your grandmother. They couldn't have conceived your mother, and she in turn couldn't have conceived you.

But wait, if you were never born, that means you couldn't have gone back in time to kill your grandfather to begin with. But… then that means your grandpa would have fathered your mother, she would still mother you, and then you would be able to kill your grandfather. But that means…. Uh oh—time paradox. The laws of physics breakdown, time and the universe unravel, and life ceases to exist all because you had to indulge some twisted desire to kill your pop-pop, of all people.

The grandfather paradox is a simple, albeit morbid, paradigm designed to illustrate the inherent problem with backwards time travel. The idea has given rise to a few different theories.

1) Chronology Protection Conjecture

The chronology protection conjecture theorized by Stephen Hawking asserts that the physics of this universe govern in such a way that backwards time travel isn't allowed, and so the grandfather paradox, valid as it is, becomes nothing more than a thought experiment.

Hawking does admit that if space-time could be folded enough, backward time travel might be possible, but he adds that warping space-time to the extent required may result in a blast of energy strong enough to destroy the time traveler, and possibly a large portion of space-time itself. I suppose the latter theory supports the idea that pieces of your corpse could travel backwards in time, but, aside from scaring the shit out of some random in the past, it’s of little use.

2) Self-Consistency Principle

The self-consistency principle, posited by Igor Dmitriyevich Novikov, theorizes that the laws of physics do allow backwards time travel. However, they will not allow a time traveler to change the past in any significant way. Touching again on your senicide festish, let’s say I gave you a time machine. Could you use it to leap back in time to “take care of” your grandfather? No of course not. I know this because you’re currently alive. If you were going to destroy grandpa, then it would have happened already, and you wouldn't be here. The self-consistency principal claims that, even if you went back and tried, nature would prevent you from causing any real damage. Your gun would jam, or you would trip on a rock and knock yourself unconscious, etc….

To illustrate the point using a different, although only slightly less macabre, example let’s say a scientist created a time machine to go back and stop the Hindenburg from exploding. If the scientist were able to save the Hindenburg, then what would have been the motivation to create a time machine in the first place? Novikov argues that the past is fixed and nature won’t allow it to be tampered with. Now that isn't saying you couldn't go back to 1942 to drink a Coke and have a look around, but it is saying that you couldn't back to 1942 to drink a Coke and then somehow prevent the Holocaust from occurring.
Novikov’s theory is more fun than Hawking’s, but it’s still too safe. It permits you to travel back in time, but it essentially renders you impotent once you get there, and, knowing you, you won’t be happy until your hands are stained with the crimson blood of your grandfather, which brings us to the third theory.

3) The Many-Worlds Interpretation

This is the cool one. Backwards time travel is explained using the many-worlds interpretation (MWI). For the uninitiated, the MWI is a quantum theory stating that all possible pasts and futures exist in parallel universes, e.g., if you’re just some dude sitting at a desk in this universe, you are a cross-dressing bankruptcy lawyer in another. In another universe you are missing your left foot and in another your car has a standard transmission instead of an automatic, and on and on.

This third theory claims that whenever you jump back in time the universe splits. The resultant universe follows its own separate timeline. Meaning your actions would affect the past of this new universe, but not the past of the universe you came from. This new universe should be similar enough that you could still buy shares of Berkshire Hathaway and, barring an attempt on your part to assassinate Warren Buffet (he is pretty grandfather-like), the company in the parallel universe would probably thrive like it has in your origin universe. You could also blow your grandfather away without any consequence to your existence, relatively speaking anyway. Your alternate universe self couldn't be born (assuming he even would have been—maybe grandpa’s gay in this universe). But, hey, there can be only one.


Sounds like the best deal, doesn't it? Well, aside from all the murder and retrograde abortions anyway. There is one hitch of course. No matter how similar this parallel universe would be to your own, it still wouldn't be your universe. Sure you’d get to off grandpa, but he wouldn't really be your grandpa, and your friends, family, and lovers wouldn't really be your friends, family, and lovers. Your loved ones would be back in the universe you abandoned in favor of wealth and familial homicide. Should that nagging thought get the better of you, it wouldn't matter. Any attempt to time travel back to your starting point would only lead you to the future of the alternate universe you created. You’d be stranded. It’s something to think about the next time you get the urge to act out the movie Terminator with your dear old granddad.