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.
