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The Grandfather Paradox – Changing Existence In An Alternate Universe

by hridika ahire
The Grandfather Paradox – Changing Existence In An Alternate Universe

March 13, 2021

The concept of time travel has always been amusing. Theorists, Physicists and philosophers have talked about time travel at stretch for centuries and are still struggling with answers. Writers on the other hand have loved including time-travel sequences in their books and movies and T.V Shows. However, did you know of a theory that suggests how you can go back in time and actually alter your existence in alternate universe called the Grandfather Paradox?

Can Time Travel Actually Change The Present?

Time travel is a concept of going back and forth in time with the help of a hypothetical device called time machine. The idea of time machine became popular when H.G Wells wrote the novel The Time Machine in 1895. We have seen in movies like Back to Future, the character goes back in time and changes the series of events to go from a lame boy to the super cool boy. As amazing as it sounds, it can have nightmarish consequences when the person returns to the present or returns at all.

time-travel-scoolbuzz
Time travel is a activity to travel back and forth in time using a hypothetical machine called time machine.

The Granfather Paradox!

A situation known as the Grandfather Paradox is very well known amongst the many paradoxes that are known to the mankind. In Grandfather Paradox, the time traveler goes back in time and kills his parents or grandparents so as to alter his future. This is also a major plot line in the movie Terminator. If the time traveler would be successful, he would not be born in one parallel universe, but still will be born in another parallel universe.

Yes. Alternate Universe. Some believe in it, some don’t, but you cannot deny the fact that it has given us a whole lot of entertainment ranging from Buffy the Vampire Slayer to Star Trek to Doctor Who to Digimon.  There has been some evidence supporting the theory of multiverse but we cannot be sure about it.

grandfather-paradox-scoolbuzz
In grandfather paradox, the traveler goes in past to kill his parents or grandparents so as to alter the future.

Time Travel and Alteration Through Murder

What we can be sure about is, if a time traveler is successful in fulfilling his agenda of killing his parent or grandparent to stop his own birth in the future, it won’t be pretty. Therefore, it is imperative that any such experiment is avoided if time travel is possible.

In the earlier versions of grandfather paradox, Tim Maudlin, a philosopher at New York University says it’s impossible on logical grounds. He said “In a way, that’s like asking why, right now, I can’t be wet and completely dry, We’ll that’s just logically impossible.”

What’s concerning about this paradox is that if the time-traveler never existed, how can they possibly have travelled back in time to kill someone? Time-travel violates the rule of causality, which says that cause must always precede its effect.

tim-maudlin-scoolbuzz
A picture of Tim Maudlin, a philosopher at the Newyork university.

Solution To The Grandfather Paradox!

A much-needed solution was needed for this paradox. Based on Einstein’s theory of general relativity that describes gravity as a warping of spacetime by energy and matter, the spinning of a black hole that has an extremely powerful gravitational pull, could cause the fabric of existence to wrap up and produce a bend in the spacetime. This would result in a closed timelike cure (CTC) that could be used to travel back in time.

To test the theory, Ralph and his PhD student Martin Ringbauer conducted an experiment with Deutsch’s model of CTC. According to Deutsch’s quantum solution, instead of a human going back to kill his grandfather, lets assume a particle goes back in time to change its generation. If the it is successful, the machine throws the particle back in the CTC, if not, the machine emits nothing. Deutsch’s insight suggests self-consistency in the quantum realm.

standard dynamic horn torus
An animation showing how the close time curve CTC works.

The Grandfathers Paradox Experiment

If the particle was a person, he would have half probability of killing his grandfather to prevent his own birth, or his grandfather could escape the death which would let the person escape this grandfather paradox. The solution is to keep the known laws of quantum mechanics because what we know can be altered but what we do not know can have severe consequences.

In the study led by Ralph and Ringbauer, they used a body double of a human or photon and ran him through a time loop simulator to see if the person emerging from the CTC was exactly the same as the original person as he may have been in the moment in the past.

Grandfather Paradox - Alternative Theory!

“The state we got at our output, the second photon at the simulated exit of the CTC, was the same as that of our input, the first encoded photon at the CTC entrance,” Ralph says. “Of course, we’re not really sending anything back in time but [the simulation] allows us to study weird evolutions normally not allowed in quantum mechanics.”

Deutsch’s model isn’t the only one to test out this Grandfather paradox. Seth Lloyd, a theorist at Massachusetts Institute of Technology proposed an alternate model of CTCs to resolve the Grandfather paradox. His model stated the use of quantum teleportation and a technique called post-selection. According to Lloyd model, the time traveler returns to the same universe that he remembers in the past rather than Deutsch’s model where the traveler enters a universe that he has nothing to do with the one he exited in the future.

  “I have no idea which model is really right. Probably both of them are wrong,” Lloyd says. Therefore, Einstein should have not wasted his time on planning a party for the time-travelers that are highly unlikely to arrive.

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