Time Travel

[Reach]

Re: Time Travel

Well, given a modern interpretation of physics, we shouldn't even have to worry about this because it won't be possible. Time as a spatial dimension can be manipulated; however, by manipulating it you're always changing a relative perception of that dimension (i.e. time dilation), it never acts as a line you can travel back and forth on. In order for time travel to be possible there would have to be some chronological record of things that have happened, and right now it doesn't look like there is one.

I don't see any reason to believe there should be one, but even assuming there was, nobody has any idea how this would work. Time could have some sort of higher spatial dimension that represents the change in time over time (what), but that still doesn't mean it records events, nor does it mean we could travel through it...or that if we did it wouldn't just change everything in the process, etc. D:

[devonin]

Re: Time Travel

That can't be though. For there to be no paradox, you'd have to not interact with anything at all. Even simple physical sensory presence would change the timeline and create a paradox.

Er...changing the timeline != A paradox necessarily

A paradox is "an argument that apparently derives self-contradictory conclusions by valid deduction from acceptable premises"

Your line of reasoning involving going back to save bob, which means that you didn't know bob needed saving, thus couldn't save bob, except you did etc etc was a paradox. I resolved the paradox by claiming that while you did go back in time intending to save bob, you clearly failed, as evidenced by bob's untimely demise. There is no paradox there.

Let me put it yet another way: While it -could- be the case that were it not for time travellers interfering in the past and changing the timeline, our present would be other than what it was, any changes they made are what happened and so regardless of what the potential alternate reality could have been, this is reality. The very "changes" people from the future made, failed to make, or tried to make are what contributed to the reality they elected to try and change.

Since we are not them, we know only what reality is, and that reality might very well include interference from future time travellers. But since we have no insight into the potential realities of the future, since they haven't actually happened, the illusion is perfect, and we simply see reality as it is now, and our past -includes- any and all changes that make have been caused by future time travellers.

[Tokzic]

Re: Time Travel

That's true, and that's why any timeline-modifying action would become a paradox. As you said, the timeline is as it would be when affected by time travel. Replace saving Bob with absolutely any change in your example and you see why it'd be a paradox:

Your line of reasoning involving going back to [do an action], which means that you didn't know [you needed to do an action], thus couldn't [do an action], except you did etc etc was a paradox. I resolved the paradox by claiming that while you did go back in time intending to [do an action], you clearly failed, as evidenced by [the timeline's final result where the action is not done]. There is no paradox there.

[devonin]

Re: Time Travel

Still not seeing a paradox. You're wanting to go change something that happened, and in the end, what happened originally still happens. This allows for you to still form the idea in your original present that you want to go try to change things. That was the crux of your paradox, which becomes resolved.

The only paradox in changing the past is that you could change the past in a way that makes the formation of your original plan to go change the past impossible. If you fail to effect the change you wanted to, the paradox is resolved.

Edit, here's your paradox.


A = Time moving as normal
X = The instant of Bob's Death

When Bob dies at X, time carries on in stream B. B is the reality in which Bob is dead. In reality B you can decide to go back in time to save Bob's life. So you go back in time to just before X and save Bob. Now you are in reality C, the reality in which Bob is alive. In Reality C you are incapable of deciding to go back in time to save Bob, and thus don't, which causes Bob to be dead, rendering reality C impossible despite the fact that you are currently living it.

That's the formulation of a standard causality paradox. Causing something to happen makes it impossible for it to happen.

What I'm saying is, You go from A to B at point X, Bob's death. Reality B is a reality in which you can decide to go save Bob, because Bob is dead. However, I claim that your attempt necessarily fails for one of any number of reasons, as evidenced by the fact that Bob is in fact dead. Reality C never enters into it, because from up the stream in reality B, all the events of A are already set and happened, including your attempt (which fails) to save Bob.

[Bynary Fission]

Re: Time Travel

Still not seeing a paradox. You're wanting to go change something that happened, and in the end, what happened originally still happens. This allows for you to still form the idea in your original present that you want to go try to change things. That was the crux of your paradox, which becomes resolved.

The only paradox in changing the past is that you could change the past in a way that makes the formation of your original plan to go change the past impossible. If you fail to effect the change you wanted to, the paradox is resolved.

Edit, here's your paradox.


A = Time moving as normal
X = The instant of Bob's Death

When Bob dies at X, time carries on in stream B. B is the reality in which Bob is dead. In reality B you can decide to go back in time to save Bob's life. So you go back in time to just before X and save Bob. Now you are in reality C, the reality in which Bob is alive. In Reality C you are incapable of deciding to go back in time to save Bob, and thus don't, which causes Bob to be dead, rendering reality C impossible despite the fact that you are currently living it.

That's the formulation of a standard causality paradox. Causing something to happen makes it impossible for it to happen.

What I'm saying is, You go from A to B at point X, Bob's death. Reality B is a reality in which you can decide to go save Bob, because Bob is dead. However, I claim that your attempt necessarily fails for one of any number of reasons, as evidenced by the fact that Bob is in fact dead. Reality C never enters into it, because from up the stream in reality B, all the events of A are already set and happened, including your attempt (which fails) to save Bob.

Perhaps so, but who says you're going to fail? If a guy tries to kill Bob, and succeeds, time progresses as normal. But if he doesn't, and you stop him, then everything changes. If he was a gangster, then many lives will fall by him, causing even bigger changes in the time-space continuum. If he was a bum, then nothing will change that much. If he was a civil rights activist, then all of Earth might be different.

If Bob is dead, you fail. If not, then you plunge time into an alternate reality forever, even if nothing changes. Even the most infinitesimally small change causes perturbations in reality, thus you have created an alternate universe in which Bob lives.

The only paradox in changing the past is that you could change the past in a way that makes the formation of your original plan to go change the past impossible. If you fail to effect the change you wanted to, the paradox is resolved.

Edit, here's your paradox.


A = Time moving as normal
X = The instant of Bob's Death

When Bob dies at X, time carries on in stream B. B is the reality in which Bob is dead. In reality B you can decide to go back in time to save Bob's life. So you go back in time to just before X and save Bob. Now you are in reality C, the reality in which Bob is alive. In Reality C you are incapable of deciding to go back in time to save Bob, and thus don't, which causes Bob to be dead, rendering reality C impossible despite the fact that you are currently living it.

That's the formulation of a standard causality paradox. Causing something to happen makes it impossible for it to happen.

This is impossible. Say, the assassin of Martin Luther King Jr. (James Earl Ray) was brought back into the past to kill MLK. If he assassinated him, then he will die. No paradox, nothing. We do not exist in multiple realities. We affect the current time and place we are in. Time cannot place you in such a paradox because you defied it. Time is an abstract concept used to reflect gradually increasing periods from a certain point. We don't exist in multiple realities. We can't be made not to do something because some other universe told us so. What if many assassins throughout history were from the future? We can't prove they were, but we can't prove they weren't. Say some were. Then, nobody would have been assassinated because a time paradox would have prevented it.

A very well-known and accepted theory is that we exist in realities that branch off of ours ad infinitum, and this comes from the fact that your hand blurs when it is waved, and bars of light interfere with each other and produce 4 instead of 6, etc, supposedly caused by interference with you from other universes doing the same action. If this were the case, we would live forever. You stated that you can save bob, but then you could never go back to save him. This was in another reality, which you are no longer within. Now to my point. In one reality you would be dead, another you are reading, another you across the world doing something, but they are all you. This means that in one you would be alive, but another dead. Yet, in many other realities, you are alive, thus making it impossible for you to die at all. I don't believe this theory, but many do, so I state it here to show that this cannot be the case with the casualty paradox.


~Bynary Fission

[devonin]

Re: Time Travel

Perhaps so, but who says you're going to fail?

The fact that Bob is dead says you fail. I thought this was pretty explicitly stated.

[Bynary Fission]

Re: Time Travel

The fact that Bob is dead says you fail. I thought this was pretty explicitly stated.

I know. I stated that you aren't necessarily going to fail. Read my post again, I explained why.


~Bynary Fission

[cry4eternity]

Re: Time Travel

Originally Posted By Bynary Fission:
There was a man named Andrew who said he traveled from the year 2246 to make a fortune off the stock market with his future knowledge of it's trends. To be exact, he made a jaw-dropping 350 MILLION dollars in two weeks. He was investigated, where he made his case. No records of him were found before he appeared.

Did a little research (wikipedia :P) and found this:

Wikpedia:
Andrew Carlssin is a fictional person from a news story hoax. A story on Yahoo reported that a man named Andrew Carlssin had been arrested for SEC violations for making 126 high-risk stock trades and being successful on every one. It was said that he started with an initial investment of $800 and made a fortune of over $350,000,000. He claimed to be a time-traveller from the year 2256. Upon making bail, he had promptly disappeared. The news article was originally published by the Weekly World News and later on was reprinted as on Yahoo News' Entertainment and Gossip section. The story was also included in the book "Pedestrian safety expert gets hit by bus" by Huw Davies.[1] It was made to be an April fools joke.

So... turns out it wasn't real, and all other similar stories I've heard have been found to be false as well.

[Bynary Fission]

Re: Time Travel

Did a little research (wikipedia :P) and found this:


So... turns out it wasn't real, and all other similar stories I've heard have been found to be false as well.

Whoa, really? I read that out of a book called The World's Most Incredible Stories...but it was published in 1992, so it was bound to be out of date. But yeah, I figured it was something akin to a prank (And for the record, I didn't really believe he was from the future, but it was always a possibility :P).


~Bynary Fission

[ieatyourlvllol]

Re: Time Travel

Supposedly, time travel essentially causes your dimension to cease to exist (relative to that which is subsequently invoked). A change of any element of the past would mean that the future would thus shift accordingly, rendering it impossible to have done so in the first place, therefore opening up a simultaneously replicating and self-terminating paradox.

Here's a rather rudimentary example that helps in visualization of one aspect of the causality paradox:

It is year 2100. You are in Dimension 1. It exists in State A.

Whilst in Dimension 1, you decide to travel into the past. Your action manifests itself in self-sustaining affectations of other events.

When 2100 dawns, it is now Dimension 2, which exists in state B, as dictated by the aforementioned action.

But wait...you were in Dimension 1 when choosing to change history. If the universe now exists within State B, the decision made within State A would have been bound to cessation, but due to the current precedence of State B, it consequently -must- have occurred.

By this notion, Dimension 1 and State A therefore must not exist. The universe as we know and experience it must then be Dimension 2 and State B, the ultimate product of all changes made to the history relative to it (and not to the other branches of existence). When you go back in time, you are in Dimension 2 / State B at first, and all changes are made to a realm (Dimension 1 / State A) that is completely removed from the parallel from which it stems but leads inevitably back to the initial reality.

I think that's -sorta- what devonin was getting at.

And while we're at it...here's another interesting concept...

Let's say you're the inventor of (the means of) time travel. Without you, it would have never been brought to humankind. Then, at some point in time, someone decides that time travel isn't meant to be toyed with, so they go back to the past for one last time and do away with you before you are to make time travel possible. But...with it gone, that could not happen. So in that case, being responsible for time travel would make you immune to assassination via that method. : O

Anyways, as for an opinion...I'm really not sure. Modern physics draws out an ambivalent stance, and until we reach that point where a tangible demonstration is brought before us, time travel exists in only theory, though who knows? It -could- be happening this very instant, and we wouldn't even know it.

[ballaw hare]

Re: Time Travel

Let's say you're the inventor of (the means of) time travel. Without you, it would have never been brought to humankind. Then, at some point in time, someone decides that time travel isn't meant to be toyed with, so they go back to the past for one last time and do away with you before you are to make time travel possible. But...with it gone, that could not happen. So in that case, being responsible for time travel would make you immune to assassination via that method. : O

Not really, it just creates an information paradox, information from nowhere. Just because you go back and kill someone who made the time machine doesn't mean the info is lost, or the machine suddenly vanishes, the laws of [macro]physics still apply.

[ieatyourlvllol]

Re: Time Travel

True, but according to fundamental physics, information still needs a medium of conveyance. If you take away the medium, although the information still exists per se, it still should not be able to touch upon any form of palpable use (unless, that is, it were to somehow break free into metaphysical exception - e.g. defy the chains of paradoxical status).

[devonin]

Re: Time Travel

I stated that you aren't necessarily going to fail. Read my post again, I explained why.

You failed. Unequivocably. There's no way you could not fail, because the state of reality reflects your having failed. There's no way out of that.

Not really, it just creates an information paradox, information from nowhere. Just because you go back and kill someone who made the time machine doesn't mean the info is lost, or the machine suddenly vanishes, the laws of [macro]physics still apply.

An example of the ridiculous nature of inventorless invention can be seen in Star Trek IV, the one where they go back in time to save the whales. In order to make a tank that can carry the whales, Scotty needs to show an engineer how to make transparent aluminum. When Bones tells him that by telling him how to make transparent aluminum, he's changed the timeline, Scotty replies "Well, how do you know he didn't invent the stuff?"

The implication is that the inventor was this man, and he invented it because Scotty told him how to make it.

But here's the thing: The man invented it because Scotty knew how to make it. Scotty knew how to make it by learning from a book, presumably originating with this man. The man learned from Scotty, Scotty learned from the man, but at no point in the process did anybody actually -invent- transparent aluminum. They've created knowledge from void.

[MixMasterLar]

Re: Time Travel

If what Dev is saying is correct, then is it not possible tha the timeline was changed billions of billions of times and then as the earth ended one time line was locked as "The" timeline; The one that we are living in now.

Therefore, should Time Travel ever be possible, I suggest that this timeline is the timline made before the end of time itself. Which is pretty much what Dev said, but maybe putting it that way makes it easier to understand

[ieatyourlvllol]

Re: Time Travel

^Pretty much

The man learned from Scotty, Scotty learned from the man, but at no point in the process did anybody actually -invent- transparent aluminum. They've created knowledge from void.

Though since past invariably precedes present, the man could be said to have been (on the timeline) the prior possessor of the knowledge. Unfortunately, because that characteristic is a product of time-based influence, the information paradox that results ultimately leads into a question akin to the classic "chicken or egg?"

So it's quite possible that a great deal of the knowledge that mankind has already garnered was brought to us by future parties, though one might find it strange that there really never is much historical mention of outsiders (obviously not of the time) who just spontaneously introduced new information. Still, that might simply be due to careful monitoring of changes carried in such a way that the possibility of time travel is never brought into clearer view. And according to the causality paradox, if time travel really can be achieved, there has to have indeed been regulation of some sort.