CAN YOU TRAVEL BACK IN TIME?

Someone I follow on @twitter, a very fine fellow called @SenorGeekus asked me a question relating to travelling through time. I thought my reasoning about time travel (whether I’m right or wrong) would make an interesting post. So here it is. Agree with me, disagree with me. I”ll be interested in reading your comments below.

I am going to describe two possible methods of backwards time travel and the problems they both pose to the time traveller.

The first is that you could travel backwards in time, but that your presence there would affect the timeline, and when you travelled to your ‘present’ time you would actually emerge into an alternate universe created by the changes your presence caused in the timeline.

To explain, you travel back in time to stop your Father from dying when you were 5. You prevent him from dying, but you drastically change the timeline in doing so. When you return to your normal time, you are in a seperate timeline. The change in the timeline would be quite obvious, your Father would be around, etc etc. What I mean is that you would know that you had emerged into a present that is different to the one you left originally.

What about a more subtle change?

You travel back in time to observe a historical event. You do not bump into anyone, talk to anyone, anything obvious. But say, perhaps, that your breathing affects the timeline because of the CO2 you have released into the atmosphere (think of the butterfly effect where a butterfly flapping its wings can cause a bigger event to happen on the other side of the world). What about where you have walked, objects you have come into contact with? When you return to your normal time, things may look very much the same, but you still would have altered the timeline ever so slightly, and would thus still emerge into an alternate timeline and universe even if you couldn’t tell it apart from the one you left.

The most well known film to deal with this kind of paradox is Back to the Future.

Marty McFly witnesses Doc Brown killed at the beginning of Back to the Future. He then travels to the past, and during the course of his adventure he leaves a note in Doc’s pocket telling him to wear a bullet-proof vest. When he travels back to the future, he witnesses Doc shot and supposedly killed again, but then all of a sudden Doc sits up and shows that he was wearing a bullet proof vest all along, and that he had the note Marty had put in his pocket 30 years before.

So… did Marty create an alternate timeline, one where Doc lives, leaving behind the original timeline where Doc dies? Well we know that Marty returns to find his parents different people, more successful and full of life, and that the antagonist Biff is a much more pleasant character after he has returned from the past, so we know he has changed the timeline.

So in Back to the Future, time travel does seem to lean more towards the quantum theory version of time travel – the multiple timeline and universe outlook. The actions of the time traveller going into the past change the timeline, even if he or she does so in only slight ways.

The other option for travelling back through time involves the predestination paradox. Let us say that you can travel back in time, but you have no influence on the timeline at all. You go back to stop your father dying when you were 5, but you cannot touch anything, you cannot interact with anything in the timeline.

Your actions in the past have no consequence. Reasoning would dictate that you are merely an observer then – but I think that the key lies with the fact that you cannot change the past in this version of backwards time travel.

Therefore, if you cannot change it, then to my reasoning you cannot visit it. If we are talking about sending a human being into the past, then really you cannot send somebody back in time if they have no reality in that timeline.
You cannot breathe in that timeline, you cannot stand on the ground in that timeline, etc etc, you are not allowed to exist in that timeline because time is locked and cannot be changed, it is all predestined to unfold as it has done, and so really its a double negative. We know that a human being, a living human being, cannot observe events in the fashion of Ebenezer Scrooge observing events from his past. It belongs in ghost stories. If we are going to travel back in time, we will have some effect on the timeline, and if we cannot have any effect on the timeline then surely the laws of nature will prevent us from being able to achieve backwards time travel.

So which one is correct?

1. You can go back, but in doing so you will create alternate timelines, and can never return to the original timeline

or

2. You cannot travel back in time, because events are predetermined to happen or are locked in place, by the predestination paradox, and therefore makes travel backwards in time a mute point

I believe the answer to be 2. If you invoke the rule of Ockhams Rule, which dictates that the simplest of two answers to a problem is usually the correct one, then you have to choose 2 as it provides the simplest answer to the problem = and that answer is No.

To me, you can only go back in time if you can exist in the past, and if you cannot exist in the past then you cannot travel to it. To travel to a time where you have no free will would surely be impossible; although the prospect of travelling into the past is an exciting one for free-thinkers.

However, whilst I do not believe that you can travel back in time… I think you could travel forward.

Again, I think there are two options. One involves travelling with great speed away from gravity, and the other involves folding the fabric of space-time itself.

1. You travel at high speed away from Earth, away from gravity, for four years but 100 years pass on Earth. Therefore you have travelled 100 years into the future, yet have only lived four years yourself. From your perspective you have travelled forward in time, though from the other side of the differential Earth has been monitoring your passage through space for a century. The other method is to travel around a black hole, at the point where the black holes gravity begins to distort space-time, creating a differential between the time around the black hole and the time whilst you travel within its orbit.

2. You travel through a wormhole, using it to pull together (or fold) the fabric of space itself to allow you to travel from one point of the galaxy to another almost instantly. However you now use the wormhole to travel between the present and the future instead, since the wormhole exists between space and time and can theoretically be used to travel to both.

It does make your head hurt when you think about time, and the many options that come with it. With my limited knowledge and outlook, I can barely understand the concepts of time travel and it would take a far better intellect than mine to fully consider all of the options.

But to answer the question posed to me by @SenorGeekus on @twitter, I do not think that time travel would affect creation, because I do not think you can travel back in time, and therefore you can only go forward into what is to come. You cannot undo what is done.

Going into tomorrow you would see what is coming, but I don’t know what good it would do you since you wouldn’t be able to travel back to the present with the knowledge you had gained.

And of course there is always the argument that there is actually no such thing as time, and that what we call time is merely a measurement of something, the wait between one moment and another.

I don’t think you can go back but I do think you can go forward.

But why would you want to?

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