part 1)
The Grandfather ParadoxThe Grandfather Paradox
This will hopefully be the first installment of a series where I talk about highly philosophical issues which science (currently) cannot understand very well. And I hope to present fun and interesting thought experiments. Discussion and argument is welcome.
I’ll start by discussing what is commonly referred to as the “Grandfather Paradox”. I read a book recently which claims to solve this paradox, but I’m not satisfied with the explanation given, I feel like it’s been “explained away” more than resolved.
For those unaware the Grandfather paradox is essentially as follows:
Assume that you can travel backwards in time. Details about time travel itself or how a time machine might work is not necessary (at least for now).
Go back in time fifty years and murder your grandfather before your father or mother was conceived. This assumedly would result in you yourself also not being born, which also means that you could not have gone back in time to commit the murder of your grandfather, first act of this situation, in the first place. Because I entertain myself with using fancy expressions I’ll refer to events like these as “null-causal event”. Expressed more accurately thus: “Causing and event which directly or indirectly alters the event itself.”
There are many different theoretical solutions to this problem. The simplest of course being “backwards time travel is not possible”, which I admit makes just as much sense at first than any other explanation. And arguments can certainly be made to support (e.g. Where are all the time traveling tourists from the future? etc.). But I’d like to assume that it is possible and most scientific articles I read or experts I see point out that most theories today (including Relativity) while don’t directly explain time travel, don’t do anything to disallow it or disprove it. So I will try to delve into each of these explanations and rationalize them as best I can for them to work. I could keep rambling on but I chose to stop at a certain point for each. If anyone has more ideas please give them.
So the solutions assuming backwards time travel is possible in some form or another;
1. The first is seen in several movies, perhaps most famously in “Back to the Future”. The solution is that; upon killing your grandfather you vanish from existence. This explanation seems at close examination to be rather silly and raises maybe more questions than it answers. However; I will not discount it entirely and may come back to it later.
2. You cannot alter the past in this way. Backward time travel is possible but certain arbitrary things are not. Like; killing your own grandfather, to be more precise; causing and event which directly or indirectly alters the event itself. At first I can understand this argument. Because of my beliefs on the nature of free will (a topic for another blog post
) and determinism and such, I can see this actually working. You may argue that it doesn’t make sense to assume the universe somehow “prevents” you from doing certain events, such as the murder of your grandfather, just because they affect your perception of reality. I assert that all reality and perception is relative (another topic for another blog post) and who’s to say your being prevented from murdering your grandfather isn’t the “magical universe” acting against you but mere chance? Of course chance alone doesn’t seem enough to explain this; if an infinite number of people time traveled and killed their grandfathers chance would dictate that some of them would fail and some would succeed. This line of thought could keep going without really getting anywhere.
But here’s a more important point:
Since all events can be argued to have infinite causes that could be traced back in time infinitely, and let’s assume you’re not a super computer or god who knows what effect every action you take will cause; why should murdering your grandfather be the only thing that alters your future? The very act of talking to him in the past may alter events such to create a null-causal event. If you consider that every action has a consequence, no matter how small doesn’t matter, every action has the *potential* to create a null-causal event. Then it seems to follow that; indeed time traveling at all shouldn’t be allowed. Just stepping foot into the past for a fraction of a second disturbs the future, however slightly.
3. Parallel universes. This was the explanation offered as the “true” solution in the book I read and a couple of shows on TV, offered by scientists that is. Believing in parallel universes means that if you consider every instant of time or every action has an infinite number of outcomes and these outcomes actually happen; at every instance an infinite number of parallel universes split off. These universes somehow exist beside our own though we can’t detect them at present (if this theory is true).
Now to deal with the Grandfather Paradox; If I go back in time and kill my grandfather what I’m actually doing is creating an alternate universe where my grandfather is dead and I don’t exist, and in my present nobody would know me.
I have a gut problem with this solution. First; I would assume that the old timeline (or universe as it were) where my grandfather is still alive and doing well that leads to my birth and this event; is still intact. And from that perspective I haven’t done anything wrong. Also from that perspective; that is, from someone, e.g. a friend of mine, might say I did not time travel but I simply vanished and never returned. A line of reasoning that follows from this is to ask; at what point is the alternate universe created or entered? When I kill my grandfather? Why not the very moment when I arrive in the past? The dilemma in a step by step;
-I time travel and kill my grandfather
-I enter an alternate universe where I do not exist in my present.
-The old timeline still exists with me and my grandfather in it.
-Where exactly was the alternate universe entered or created? If I say it was when I killed my grandfather; this means my present self existed in my own past. We won’t think about the fact that my family could have pictures of this mysterious person in their past, mysterious that is until I was born then shock at the realization that I time traveled and whatever that might entail. Remember the point from #2; every single action has the potential to create a null-causal event; therefore it seems that using this explanation, upon time traveling you may be entering an infinite number of alternate universes constantly. As long as I exist in my own past there is the potential for infinite null-causal events. So If I assert that upon creating a null-causal event I enter an alternate universe it seems impossible or at least highly unlikely that I will ever succeed in getting to the point of killing my actual grandfather [that is; the grandfather from my original time-line. I could still kill “a” grandfather, but it wouldn’t be him, it would be an alternate universe grandfather]. And this seems to take us back to either #2’s argument again or simply “time travel not being possible”.
-If I assert that the moment when I enter the alternate universe immediately or by the act of time traveling; then it’s seems clearly impossible to kill your own grandfather, not only that but impossible to enter own past timeline. Furthermore I can quite easily argue that I have not actually time traveled at all. I merely stepped into or created an alternate universe which is exactly identical to my own, except happens to be fifty years behind mine, to give me the illusion of time travel. I have no problem excepting the alternate universe (or infinite worlds theory, it’s sometimes called). But I feel like this explanation, while totally plausible, is a side point, and doesn’t truly solve the problem or explain how a null-causal event works. Parallel universes may exist; but who’s to say they’re necessary to resolve the grandfather paradox (other than no other better resolution has been offered yet)?
So it seems to me that we haven’t yet truly been able to kill our grandfather and #2’s prospect is getting close to proving itself in a very unexpected or roundabout way. But I still don’t like that explanation
I will be working on a fourth explanation soon, for a future blog post. Hope you enjoy. If anything is confusing or not well worded please let me know.
