My wife and I have just finished the first season of Dark on Netflix. I’m not a sci-fi fan–I know, it’s a real, moral shortcoming on my part–but Dark poses questions about time travel that wakened my inner philosopher. I can say this about one of the story arcs without giving away too much: a character walks through a wrinkle in time and comes out in the same place he had been, but 33 years earlier. One of his friends figures out what happened, and goes to 1986 to try to bring him back. However, if the first person is rescued and comes back to the present, he would not become a father. What would happen to people he never created?
Philosophers and physicists have long debated the efficacy of time travel. The conundrum these two characters face is known as the grandfather paradox:
The dead giveaway that true time-travel is flatly impossible arises from the well-known “paradoxes” it entails. The classic example is “What if you go back into the past and kill your grandfather when he was still a little boy?”…So complex and hopeless are the paradoxes…that the easiest way out of the irrational chaos that results is to suppose that true time-travel is, and forever will be, impossible. (Asimov, 2003, 276–7)
Other philosophers have raised valid objections to Asimov. It seems that the Theory of Relativity also opens up the possibility of time travel because of the existence of closed timelike curves.
So. . .to get back to Dark, what’s the easiest way to articulate the possibility that time travel exists AND that traveling backwards in time can result in changes to the present?
There are two main ways of looking at the supposed effect of time travel. The two ideas are known as the butterfly effect and the many worlds theory. The main difference between the two idea is the matter of if there is a single timeline or an infinite amount of timelines. The butterfly effect is the idea that one small change can change everything in life. For example, if you kill a butterfly, then it doesn’t pollinate a flower, and if that flower was the great, great, great grandfather of the flower field that your dad would have picked from to give your mom, but since he couldn’t you weren’t born. The many worlds theory believes that every choice you make makes a new timeline that is parallel to the infinite amount of other choices you could have made.
The grandfather paradox is a result of adhering to only of one the possible ratifications of time travel, the butterfly affect. Since you killed the person that made you, then you are not made and then you can not kill the person who made you, the timeline is frozen and makes time travel seem impossible. However, if you take the many worlds theory, when you contemplate whether you kill your grandfather or not, you unknowingly create two separate timelines. In one timeline, you choose to kill him and the line is stuck in a permanent loop of your birth and unbirth. In the other timeline, things proceed as normal and you probably come back to present a better person. The only way you could safely change the future/present is if you go back in time and stay there to make sure everything goes as it should, basically sacrificing your existence for whatever you are trying to do.
The grandfather paradox can be solved quickly with the introduction of the possibility of multiple timelines. If time is seen as just one straight line of indefinite length, then other dimensions can be represented as several other parallel lines which all exist on a plane of existence. Traveling back in time to exist in a time which you aren’t supposed to would force you into a different timeline since it would be impossible for you to exist in the past at your age in your timeline. Therefore, any change you make would affect whatever other timeline you traveled to and returning back to your time using the time machine would take you back to your real timeline where it would be possible for you to exist.
If time travel were to be a reality in any form without completely imploding the universe with paradoxes and improbabilities, it would have to hold multiple dimensions to host different realities. If you go back in time and shoot your grandfather before he ever meets your grandmother, that would create a paradox. As you would never be born to shoot your grandfather, but he is now dead. The only solution would be if you could only make changes that would not severely affect the dimension your in, and if you do you are simply transposed into a different dimension you are able to exist in.
Many people accredit this to Mandella effects occurring. These little changes in our world do not have large impacts on how everyday society functions, but for some reason, people can still notice them.
Explaining how time travel could affect the present really just depends on how it works in general. There’s one big question that determines this: is the future already set in stone? If it is not, then the grandfather paradox definitely exists because that means that real changes can be made to the present by going back. If all events are already set in stone, then going back in time would have already been accounted for by the state of the present. In an Artemis Fowl book, Artemis Fowl explains this idea. He states that everything happened that caused him to go back in time because he went back in time. This means that him going back in time was accounted for on the timeline of the past, whether he only knew it in the future or not. In “Harry Potter and the Prisoner of Azkaban”, J.K. Rowling shows this concept of time travel when at the end Hermione uses the Time Turner. Earlier, a rock was thrown at her, but she did not see where it came from. Later, when she goes back in time, she realized she was the one who threw the rock in order to get herself to leave. This shows that all past actions will be shown in the present. Also, this idea means that the person or people who did the time traveling will only have the memory of the first action and how they changed in later(or before depending on how you think of it). Then everyone else would have only lived out the past that the time travelers altered. Therefore, the grandfather paradox is not necessarily true.
Firstly, I’m proud of Dr. E for actually doing something involving Sci-Fi. Secondly, there are so many possibilities as to how time travel could exist and consistently change the present. For example, there is the multiverse theory that could say that every time one time travels, they land in a new universe that is an exact copy of ours, but has to deal with the consequence of the time jump. Another theory is that everything that has ever happened or ever will happen is in this universe, and our day to day lives are just us dealing with the effects of other people’s unseen time travel whims. Honestly, there are so many things that humans can come up with that there’s no way we could possibly just pick one and roll with it forever.
The solution of the grandfather paradox can be examined if the potential for multiple timelines is factored in. If time travel became possible then the timeline where a time machine was created would have parallel timelines associated with it that include all the various possibilities, including the grandfather paradox. If linear series of events were intertwined then the grandfather would be dead in one timeline and both the grandson and the grandfather would be alive in the other.
The easiest way to say time travel exists and that traveling backwards in time can result in changes to the present is to just presume time travel does exist and hand wave away the technical bits. Like in Doctor Who, just say time-travel is “wibbly-wobbly” stuff and be done with it. Time travel is an intriguing concept with a dash of wish-fulfillment that makes it fun to play with in fiction. Some of my favorite media are time travel stories, like Back to the Future, providing narrative-based explanations for the issues with time travel. In the first Back to the Future movie, changes in 1955 cause Marty’s family in 1985 to disappear. Though this gets resolved, there are still permanent changes in the “future.” Even though the details about how time travel works aren’t solid, the story is still compelling. It’s fine that a plutonium-fueled Delorean can make its occupants travel in time because it’s fiction and the logistics are believable enough. Despite numerous hypotheses, I think it’s rather accepted that time travel (at least the type dreamed up in fiction) isn’t possible in reality. Stephen Hawking held a party for time travelers once. Nobody showed up.
The easiest way to understand time travel and make it possible is to assume that another timeline is created when the time machine is used. So if you use the time machine to fulfill the goal of killing your grandfather before he creates your father, you will leave your own timeline and create another timeline that allows that possibility.
Interestingly, the grandfather paradox has been studied and a new model that contradicts this paradox has been proposed by the theorist David Deutsch.
Essentially, the physics that is thought to accompany time travel can be avoided when dealing with the physics of smaller particles, which formulates a theory that would unify general relativity and quantum mechanics, paving the way for time travel. And according to NASA, traveling to the future is more possible than traveling to the past.
However, the grandfather paradox is based on the tenet that the future can be drastically altered if the relative present is altered. Logically, this paradox makes sense because the consequences of a person’s decisions carry over time.
Billings, L. (2014, September 02). Time Travel Simulation Resolves “Grandfather Paradox”. Retrieved February 19, 2018, from http://www.scientificamerican.com/article/time-travel-simulation-resolves-grandfather-paradox
Retrieved February 19, 2018, from https://spaceplace.nasa.gov/review/dr-marc-space/time-travel
The grandfather paradox would not be possible unless you make a new time line when you travel back in time. If you killed you grandfather as a boy you would alter your own time line to the point it would stop.You would kill your self in the prosses
I think that in the circumstance that time travel exists, multiple universes would as well. So, whenever someone travels back in time and changes something, and thus changing the future irrevocably, that creates another universe. When travelling back to the present, the person may or may not go back to the original universe, the one they created, or even a new one altogether. There is also the thought that, if multiverse theory is incorrect, the universe will right itself. For example, if one goes back in time and shoots their grandfather, someone will be able to save him. If one were to stop the Holocaust in Germany, one would happen in France.
The grandfather paradox is a popular paradox in the topic of time travel and so is the butterfly effect. In a simple definition, the butterfly effect is the result of going back in time, changing one tiny seemingly insignificant detail and causing mass chaos back in the current time or the future. If time travel did exist, the grandfather paradox could be easily avoided; just don’t kill anyone, especially not your own grandfather. The butterfly effect can’t be avoided so easily; it could easily be the result of a simple accident. Now, the grandfather paradox is definitely more mind-bending than the butterfly effect, but the butterfly effect would more catastrophic than the paradox.