A Computer Solved Time Travel’s “Grandfather Paradox” With An Extra Time Machine

It’s the age-old problem–“But if I go back in time and accidentally kill my grandpa, then how could I have time traveled in the first place?”

Or, well, it’s an age-old problem for fans of time travel fiction. Lucky for us, computers can fix everything. Well, the answer to the infamous Grandfather Paradox at least.

Computer scientist Doron Friedman programmed a computer with his own automation software to tackle the issue of a man going back in time and killing his own dad. According to Cosmos Magazine, this is how the process unfolded:

When Friedman ran this plotline through his program, it noticed the paradox by reporting a contradiction – namely that if the son travels back in time and kills his father, then how could the son have been conceived?

And when Friedman requested a resolution to the contradiction, the algorithm worked through thousands of possible scenarios to find those that were logically consistent – in other words, where the murderous son’s actions don’t rub him out of existence.

Once the program had worked through the scenarios, Friedman described two of the many possibilities that the computer had worked out. The first is notable for being one that Futurama viewers will likely recognize–it was employed in their Emmy Award-winning episode “Roswell That Ends Well.” This work-around involves that guy becoming his own grandfather; after going back in time and killing pops, the man then goes back and sires a kid who will become his father. (Of course, this requires the unpleasant possibility of getting involved with one’s own grandmother.)

The second possibility is exceptionally cool. It involves the guy’s dad having his own time machine (with George and Marty McFly used as the stand-ins, of course):

In 1954 Marty’s father George travels forward in time one year to 1955, when he impregnates Marty’s mother Lorraine before immediately returning back to 1954 – just as his future son, Marty, arrives and kills him.

Because George’s quick foray into the future allowed him to already conceive his son, the paradox disappears.

Yeah okay, it’s a bit silly because why would you decide to travel one year into the future to sleep with your significant other? But surely some savvy author could come up with a plausible reason for it, and prevent the Grandfather Paradox from ever causing a problem in their sweeping time travel epic.

Just make sure to thank our computer overlords in the acknowledgements, as there’s no telling what they might compute next if you don’t….


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