Deductive Logic on the subject of Time Travel.

[Mentat]

When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

[MathematicalPhysicist]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.
from c it can be concluded that you no more life in the present time therefor p1 isnt right anymore and so is p2, instead of them you can propse the premises which come from the conclusion (the first conclusion becomes a premise):
p1:I exist in 1776
p2: i dont exist in 2003.
c: i must have gone back in time (-;

[Mentat]

Originally posted by loop quantum gravity
from c it can be concluded that you no more life in the present time therefor p1 isnt right anymore and so is p2, instead of them you can propse the premises which come from the conclusion (the first conclusion becomes a premise):
p1:I exist in 1776
p2: i dont exist in 2003.
c: i must have gone back in time (-;

I'm sure you already know that this doesn't follow, lqg. Ben Franklin existed in 1776, but he didn't go back in time.

No, I seriously need a criticism of my reasoning on the matter, since it is supposed to be "possible" to travel back in time.

BTW, I always "exist in the present time" (as you put it), since the very term "exist" is in the present tense. I don't think P1 can be invalidated.

[MathematicalPhysicist]

Originally posted by Mentat
I'm sure you already know that this doesn't follow, lqg. Ben Franklin existed in 1776, but he didn't go back in time.

No, I seriously need a criticism of my reasoning on the matter, since it is supposed to be "possible" to travel back in time.

BTW, I always "exist in the present time" (as you put it), since the very term "exist" is in the present tense. I don't think P1 can be invalidated.
but the present time is changing for you when youre travelling in time, if you travell in time the present is ofcourse subjective the past becomes your present and the present becomes your future which you already know it (so you can say the future is forseeable).

i think your reasoning is true the conclusion contradicts the premise.

[Mentat]

Originally posted by loop quantum gravity
but the present time is changing for you when youre travelling in time, if you travell in time the present is ofcourse subjective the past becomes your present and the present becomes your future which you already know it (so you can say the future is forseeable).


Yes, this is all true, and it is the reason why P2 is phrased as it is. I exist now, in a reality that is contingent with P1.


i think your reasoning is true the conclusion contradicts the premise.

Thanks for the support, I can't seem to find a flaw either...I hope someone else can.

[hypnagogue]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

We can circumvent this contradiction if we assume parallel universes (which is the standard way to get around most time travel paradoxes, such as the matricide paradox). If we assume parallel universes, then we get something like this:

P1: I did not exist in 1776 in universe A.
P2: I exist now in a reality that includes P1 as being true (although I think this one is a little redundant, if we are already assuming P1 to be true).
P3: I go back in time (using whatever means) to 1776.
C: It is logically inconsistent for me to still be in universe A; therefore I must be in a different universe, call it B, with a history/timeline very similar to A's.

[diverz]

You guys ever heard of this theory ----> Present conditions affects past

Sounds illogical isn't it? Its always a forward motion of ------> the present conditions affect the future.

Your thoughts?

[Mentat]

Originally posted by hypnagogue
We can circumvent this contradiction if we assume parallel universes (which is the standard way to get around most time travel paradoxes, such as the matricide paradox). If we assume parallel universes, then we get something like this:

P1: I did not exist in 1776 in universe A.
P2: I exist now in a reality that includes P1 as being true (although I think this one is a little redundant, if we are already assuming P1 to be true).
P3: I go back in time (using whatever means) to 1776.
C: It is logically inconsistent for me to still be in universe A; therefore I must be in a different universe, call it B, with a history/timeline very similar to A's.

Hmm...I suppose this could work, but wouldn't adding an extra Universe violate Occam's Razor?

Also, Stephen Jay Gould (along with many others) is in favor of the idea (the name of which I've forgotten...temporary brain fart) that changing even the smallest thing in history can dramatically change the series of events that happen afterward. He believes that the course of history is occurance acting on the otherwise probabilistic/chance-governed nature of reality. I (currently) agree with him on this point, since the alternative seems like determinism.

Oh yeah, the phrasing of P2 could seem redundant, I suppose, but I couldn't think of a better way to phrase it at the time.

[Mentat]

Originally posted by diverz
You guys ever heard of this theory ----> Present conditions affects past

Sounds illogical isn't it? Its always a forward motion of ------> the present conditions affect the future.

Your thoughts?

I guess it's not unscientific, but I do think it may be illogical...my first attempt at a proof:

P1: I exist in the present (slightly redundant in itself, since "exist" is in the present tense).
P2: P1 is true only because of the previous occurances which lead up to my having been born and living as I've lived.
P3: Because of P1 and P2, any change in the past, caused by me, stops me from existing, which stops me from changing the past, which allows me to exist again...which will go on in circles.
C: The idea of my changing the past is self-contradictory/paradoxical.

[physicskid]

I find time travel an indeed very stupid idea
because, wouldn't your memory of what you have perceived
now and in the past flow back to the
surroundings through your five senses
when you travel to the past?!
So you would not even know that you had travelled
back in time becasue you can't bring
your present consciousness to the past.

Sounds logical right?

For example:
Imagine that you are living in negative time zone
(equivilant to travelling back in time)
and you are gliding at a speed of 10m/s for -10s
(because you are in negative space-time).

So the distance travelled= (10m/s)*(-10s)= -100m
Conclusion: If you are travelling back in time,
everything that you did or possess would act
in the reverse manner! (including your brain!)

[Mentat]

Originally posted by physicskid
I find time travel an indeed very stupid idea
because, wouldn't your memory of what you have perceived
now and in the past flow back to the
surroundings through your five senses
when you travel to the past?!
So you would not even know that you had travelled
back in time becasue you can't bring
your present consciousness to the past.

Sounds logical right?

For example:
Imagine that you are living in negative time zone
(equivilant to travelling back in time)
and you are gliding at a speed of 10m/s for -10s
(because you are in negative space-time).

So the distance travelled= (10m/s)*(-10s)= -100m
Conclusion: If you are travelling back in time,
everything that you did or possess would act
in the reverse manner! (including your brain!)

Ok, so you're talking about regressive backward time travel. Yeah, I agree, it is completely illogical.

[Royce]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

Isn't this where I came in, Mentat?

If you went back in time to 1776 (P3) then that would invalidate P1. The rest would still be valid except the inclusion in P2 that P1 is true. It would also be true that in the present time of P2 the fact that you went back to 1776 (P3); (C) would already be in your history which would again make P1 invalid. P1 can never be true if you ever go back in time to 1776. P1 and P2 are true only if you never go back in time to 1776. It isn't a paradox as P1 and P3 are mutally exclusive. One or the other but not both can be true.

[Anti-Jesus]

Originally posted by physicskid
I find time travel an indeed very stupid idea
because, wouldn't your memory of what you have perceived
now and in the past flow back to the
surroundings through your five senses
when you travel to the past?!
So you would not even know that you had travelled
back in time becasue you can't bring
your present consciousness to the past.

Sounds logical right?

For example:
Imagine that you are living in negative time zone
(equivilant to travelling back in time)
and you are gliding at a speed of 10m/s for -10s
(because you are in negative space-time).

So the distance travelled= (10m/s)*(-10s)= -100m
Conclusion: If you are travelling back in time,
everything that you did or possess would act
in the reverse manner! (including your brain!)

Okay im only 15 but i question your idea. Because isn't your memory just chemicals in your brain which your brain reconize as memorys? if thats right when you travel back in time then those chemicals would be the same therefore your memory would be the same? right? Anyways maybe we shouldn't go back in time unless the idea of multiple (and i mean lots!) realitys or timeflow(brain just went dead) right? or we might do one of those weird paradox things where we **** up the universe:D

[hypnagogue]

Originally posted by Mentat
Hmm...I suppose this could work, but wouldn't adding an extra Universe violate Occam's Razor?

Maybe, maybe not. From where we currently stand, it seems to violate Occam's Razor. But suppose one day we find that time travel into the past is possible. Well, if this occurs, we know that the traditional paradoxes that are associated with time travel must be false, otherwise we would have a logically inconsistent system (much like the one you created). At this point, then, it would be more reasonable to assume parallel universes to explain how time travel into the past is possible without raising all those paradoxes.

Also, Stephen Jay Gould (along with many others) is in favor of the idea (the name of which I've forgotten...temporary brain fart) that changing even the smallest thing in history can dramatically change the series of events that happen afterward. He believes that the course of history is occurance acting on the otherwise probabilistic/chance-governed nature of reality. I (currently) agree with him on this point, since the alternative seems like determinism.

That sounds more like he is describing history as chaotic, as opposed to non-deterministic. In any case, I agree that history probably works like that. No doubt that going back to 1776 would greatly change the future course of history. But the important idea is that that greatly changed future happens to another universe, and thus is not in contradiction with the history we have observed in our own universe.

[Royce]

Hypna,
That line of thought ignores the fact that if some one were to go back in time and do something that would alter history and thus the present and future history, it would already be in our history that that had happened.
Going back in time may or not be possible in one universe, I think not; but, changing past history is logically impossible. As I said, any change would already be part of our history and not a change at all. What has happened in the past happened and that would include someone going back and effecting what was then happening.
Multiverses is another thing. If some one where to go back and do something that would start another universe in which his doing whatever he did would already be in its history. That doesn't make any sense at all to me; but then I don't believe in multi-universes.
Here I agree with Mentat, that that would violate Occam's Razor. Not tha Occam's Razor is an inviolate Law; but, that it is not necessary, elegant or beautiful but messy, redundant and over complicated.

[hypnagogue]

Originally posted by Royce
That line of thought ignores the fact that if some one were to go back in time and do something that would alter history and thus the present and future history, it would already be in our history that that had happened.

Well, I see what you are saying about the "already would have happened" part. I agree with that. Sometimes it is easier to say "change," however, to draw attention to how things in our respective universes are similar (or identical) up until the point when a time traveler from one enters the other at a certain point in time.

But say someone traveled back to 1776. It would not have already happened in our universe, since in our universe A no one did go back to 1776. That happened in universe B.

Here I agree with Mentat, that that would violate Occam's Razor. Not tha Occam's Razor is an inviolate Law; but, that it is not necessary, elegant or beautiful but messy, redundant and over complicated.

Then again, Occam's Razor is not really relevant here. We aren't talking about whether time travel is actually possible, only if it could be logically possible. Thus, it suffices to create a logically consistent scenario where time travel is logically possible. Whether that logical possibility is then a physical actuality is a question of empirical investigation, which is a separate issue.

[Royce]

Originally posted by hypnagogue

But say someone traveled back to 1776. It would not have already happened in our universe, since in our universe A no one did go back to 1776. That happened in universe B.

Then again "logically" speaking in a multiverse scenario, it would have already happened in B's history. We can't get around it. No matter which history or which unverse's past we go to, It had to have already happened, been recorded and experienced in that universe's history. It is either that or a split occurs in which one universe's past was not visited and changed and ther other was visited and changed but no one would know it because that universe's history would already contain and record the visit and "change" but for them it would not be a change in there history because their history already includes the "change". Only some supra spatial being outside of space and time would be able to see the change by noticing the split.
Simply put, logic will not allow the future to effect any change in the past as it would have already been included in its history and thus is not a change. No way around it. I hate to be a bubble buster because I have always loved sci-fi time travel stories but logically it can't happen.
We can't go back and save Lincoln or assassinate Hitler because if we do it would already be part of our history and it would be imperitive
that we do go back and save or assassinate. This would make the universe's present determined by it past, eliminating free will.
So instead of going back and killing your grandfather to change history all you have to do is not go back and save lincoln in a universe where you did go back and save lincoln; but in that universe you would not have that option or ability. No matter what you tried or tried not to do you would be forced to go back and save lincoln because that is already your history. And on and on and on ad nausium.


Then again, Occam's Razor is not really relevant here. We aren't talking about whether time travel is actually possible, only if it could be logically possible. Thus, it suffices to create a logically consistent scenario where time travel is logically possible. Whether that logical possibility is then a physical actuality is a question of empirical investigation, which is a separate issue.

Okay, I'll go along with that but then I have shown how it is logically impossible. Logic will not only not allow a paradox but it won't allow a messy, ugly, redundant multiverse either.
It is not a Law of logic that can't be violated as a physical law but that if it were violated then it wouldn't be logical. Our universe has so far as we know is logical. It is cosmos not chaos.

[Mentat]

Originally posted by Royce
Isn't this where I came in, Mentat?

If you went back in time to 1776 (P3) then that would invalidate P1. The rest would still be valid except the inclusion in P2 that P1 is true. It would also be true that in the present time of P2 the fact that you went back to 1776 (P3); (C) would already be in your history which would again make P1 invalid. P1 can never be true if you ever go back in time to 1776. P1 and P2 are true only if you never go back in time to 1776. It isn't a paradox as P1 and P3 are mutally exclusive. One or the other but not both can be true.

I don't understand what you are saying. If P3 is true, then both P1 and P2 also have to be true (since my existence is kind of required for "me" to travel back in time [;)]).

Besides, my point is that I can establish P1 and P2 as being true (by scientific and other such proofs) but they would invalidate P3, and thus I can never travel back in time...does that mean that it is illogical to postulate time travel?

[Mentat]

Originally posted by hypnagogue
Maybe, maybe not. From where we currently stand, it seems to violate Occam's Razor. But suppose one day we find that time travel into the past is possible. Well, if this occurs, we know that the traditional paradoxes that are associated with time travel must be false, otherwise we would have a logically inconsistent system (much like the one you created). At this point, then, it would be more reasonable to assume parallel universes to explain how time travel into the past is possible without raising all those paradoxes.


"At that point it would be reasonable"? Does that mean that at this point it is not reasonable? Are the "extra" postulates really "extra", since there is no indication (now) that other Universes exist?


That sounds more like he is describing history as chaotic, as opposed to non-deterministic. In any case, I agree that history probably works like that. No doubt that going back to 1776 would greatly change the future course of history. But the important idea is that that greatly changed future happens to another universe, and thus is not in contradiction with the history we have observed in our own universe.

Here's a question for you, with regard to that "extra Universe" idea: How can one ever get to another Universe? This is not an irrelevant question of possibility in practice, I'm talking about possibility in principle. If there is another Universe*, then there is nothing seperating that Universe from ours (not space, not time, not anything), and thus there is (logically) also nothing connecting us, which precludes our ever traveling there, doesn't it?


*In these contexts, I will deign to refer to "Universe" in the common sense of what astronomers refer to as "local universes", and not in the "set of all that exists" sense.

[Mentat]

Originally posted by hypnagogue
Then again, Occam's Razor is not really relevant here. We aren't talking about whether time travel is actually possible, only if it could be logically possible. Thus, it suffices to create a logically consistent scenario where time travel is logically possible. Whether that logical possibility is then a physical actuality is a question of empirical investigation, which is a separate issue.

On the one hand, I agree with you that you are just constructing a possible-in-principle framework, in response to my request for all possibilities to be presented.

On the other hand, the problem with Occam's Razor is a real one, in this case, since yours could (note: "could", not necessarily "will") become an ad hoc argument, since you would first add the postulate of an extra Universe. Then postulates of how (even in principle) a connection could be established between Universes, and so on.

[Mentat]

Originally posted by Anti-Jesus
Okay im only 15 but i question your idea. Because isn't your memory just chemicals in your brain which your brain reconize as memorys? if thats right when you travel back in time then those chemicals would be the same therefore your memory would be the same? right? Anyways maybe we shouldn't go back in time unless the idea of multiple (and i mean lots!) realitys or timeflow(brain just went dead) right? or we might do one of those weird paradox things where we **** up the universe:D

Welcome to the PFs, Anti-Jesus. [:)]

I, too, am 15 years old. It makes me feel good to know that there are others, around my age, that are interested in science or philosophy as I am.

Anyway, I don't think your counter-argument works, because physicskid was referring to regressive time-travel (wherein everything starts going backward, until the point in time that is your destination). As it is, everything going backward requires that you too go backward, since you are part of "everything". Ergo, you would get younger and younger, until you ceased to exist.

[hypnagogue]

Originally posted by Royce
Then again "logically" speaking in a multiverse scenario, it would have already happened in B's history. We can't get around it.

Yes, I acknowledged this in my previous post.

Okay, I'll go along with that but then I have shown how it is logically impossible. Logic will not only not allow a paradox but it won't allow a messy, ugly, redundant multiverse either.
It is not a Law of logic that can't be violated as a physical law but that if it were violated then it wouldn't be logical. Our universe has so far as we know is logical. It is cosmos not chaos.

You are confusing aesthetics with logic. For something to be logically possible, it does not have to be beautiful or elegant or orderly. It just has to not contradict itself.

[hypnagogue]

Originally posted by Mentat
"At that point it would be reasonable"? Does that mean that at this point it is not reasonable? Are the "extra" postulates really "extra", since there is no indication (now) that other Universes exist?

Well, you have raised questions as to its reasonableness due to OR, which I can accept. There is indeed no indication of multiple universes as of yet. It is just a theory, but again, that is all that this thread has asked for.

Here's a question for you, with regard to that "extra Universe" idea: How can one ever get to another Universe? This is not an irrelevant question of possibility in practice, I'm talking about possibility in principle. If there is another Universe*, then there is nothing seperating that Universe from ours (not space, not time, not anything), and thus there is (logically) also nothing connecting us, which precludes our ever traveling there, doesn't it?

The traditional answer to a question like this is simply "wormholes." I believe it is consistent with current theory that a region of spacetime could become "pinched off" from our own universe and be connected via a wormhole. How to create or travel through such a wormhole is obviously problematic, but I don't think it has yet been shown to be logically impossible.

[Mr. Robin Parsons]

In order for your logic to work, P1 P2 and C must all exist at the same time.

When you leave the present time, travel back, the present time does not disappear to everyone else, hence it would be required that both Now, and 1776, exist at the same time, all the time!

That would infer that all time exists in all space all of the time, which invalidates the very notion of time itself.

It is not wrong to postulate time travel but prefferable that you do not become obsessed with something that cannot exist, as time itself does not 'exist', substantively, merely idealogically.

[Royce]

P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...


P1 is true only if P3 is false; because, if P3 is true at any time in your life, that event would always be true in your history. The only way that P1 can ever be true is if P3 is always false.

P2 is a conditional statement, i.e. it requires that P1 be true for P2 to be true thus it is not a proposition. However if P1 is true then P2 is true if and only if P3 is false.

If P3 ever becomes true then it makes P1 false. P2 is also false then because of the inclusion of P1 and also because you cannot exist in both states at the same time. Your are either in the present or in 1776.

C is only true if P3 is true and P1 and P2 are false.

In other words your entire set of statements is illogical reguardless of whether time travel is logical or not.

[hypnagogue]

The set of statements is not illogical if revised as I have outlined. If in universe A I exist in 2003 but did not exist in 1776, this is not inconsistent with saying that I existed in 1776 in universe B. (Assuming the multiverse version of time travel, of course-- but again-- we are only looking for logical consistency here.)

[Royce]

I agree, Hypna, as revised in a multverse scenerio your set would be logically valide so long as you make reference to which universe you are speaking of when.
It is perfectly logical to be both not in 1776 in universe A and be in 1776 in universe B; but that must be stipulated before hand.

Mentat was making a logical statement including time travel to show that time travel is not logical. He has done this before. If fact back in March when I first joined PF it was one of the first discussions that I got involved in. We have been buddies ever scince.
which is why I said that this is where I came in.
I don't think time travel in a single universe is logically possible at least yet. It may be possible to go back and observe but not to interact with or be detected by the past. If we ever detect or are contacted by someone or thing from the future then it would be possible. I go along with Hawking on this. He does not believe that time travel is possible but he would never bet against it with anyone because that person may be from the future.

[Mr. Robin Parsons]

Sticking to the one universe we know exists, try a simple excersize, prove to me (using logic) that we are travelling forward in time, at this very moment.

See, time is the application of an Ideology (an ideological system) upon a reality, and fooling ourselves into somehow believing that that makes it a real thing, it ain't!

[phoenixthoth]

perhaps by showing that the total entropy is increasing? but why that should be called forward in time i don't know. whatever forward means, backward means the opposite of that so it doesn't make any difference if we're moving forward or backward in time or what we call what we're doing. seems as though if the total entropy was decreasing, some thermodynamics laws might be invalidated.

[einsteinian77]

I would also like to add that if you were to travel back to 1776 wouldn't you be nullifying all the events that lead up to your existance and therefore making it impossible for you to exist. Thats only if there is one past of course.

[Mentat]

Originally posted by Mr. Robin Parsons
Sticking to the one universe we know exists, try a simple excersize, prove to me (using logic) that we are travelling forward in time, at this very moment.


P1: If I were going backward in time, I would not being responding to this post, since reading precedes responding.
P2: I am responding to this post, after having read it.
C: Therefore, I am not going backward in time.

[Mr. Robin Parsons]

Originally posted by Mentat
P1: If I were going backward in time, I would not being responding to this post, since reading precedes responding.
P2: I am responding to this post, after having read it.
C: Therefore, I am not going backward in time.
It has the arbitrary nature of "up and down", (when we know it is away from the Earth and towards) as the simple reality is that you only see your life as it has passed you.

Intuitively you could construe that as you travelling backwards through time, as if while travelling through this, "you only look backwards", as you can only see the parts of your life as they have passed, you travel with your back towards the futur, you are travelling backwards?

Backwards and forward in time is arbitrary in nature, impossible in reality.....there is no time, just an ideological (ergo Very useful) perception of (a BIG hint) Movement/Motion!

Otherwise, you are fooling yourself, and this can be proven(?)!

[Mentat]

Originally posted by Mr. Robin Parsons
It has the arbitrary nature of "up and down", (when we know it is away from the Earth and towards) as the simple reality is that you only see your life as it has passed you.

Intuitively you could construe that as you travelling backwards through time, as if while travelling through this, "you only look backwards", as you can only see the parts of your life as they have passed, you travel with your back towards the futur, you are travelling backwards?

Backwards and forward in time is arbitrary in nature, impossible in reality.....there is no time, just an ideological (ergo Very useful) perception of (a BIG hint) Movement/Motion!

Otherwise, you are fooling yourself, and this can be proven(?)!

Was this designed to confuse me? Seriously, if you are looking "backward" at the future, that you are coming from, then the future is the past, and the past is your future, and 1776 would have to be in the "future", since I'm moving farther and farther away from it, right?

[Mr. Robin Parsons]

Originally posted by Mentat
Was this designed to confuse me? No, but it obviously did. Seriously, if you are looking "backward" at the future, that you are coming from, then the future is the past, and the past is your future, and 1776 would have to Have been in the "future", since I'm moving farther and farther away from it, right?
As I tried to help you to realize, they are arbitrarily interchangable words, "forwards in time" and "backwards in time" nothing establishes which "direction" truly is the one we "move" in, other then human convention.

[Mentat]

Originally posted by Mr. Robin Parsons
As I tried to help you to realize, they are arbitrarily interchangable words, "forwards in time" and "backwards in time" nothing establishes which "direction" truly is the one we "move" in, other then human convention.

I understood this part of it, but I don't understand how it changes anything, since I am moving away from 1776, regardless of whether it happened in my "future" or "past", right?

[Mr. Robin Parsons]

Originally posted by Mentat
I understood this part of it, but I don't understand how it changes anything, since I am moving away from 1776, regardless of whether it happened in my "future" or "past", right?
Yes, but it also tells you that the universe cannot exist in the same state twice, ergo it is a singularity of sorts inasmuch as the state of the universe at any given time is the only point in any time that it will exist that way, hence if you are existent NOW, then the past is NOT available to you as time travel is impossible, as you cannot travel through that which doesn't actually exist. (You cannot travel through an "Idea"....'cept in your mind hee-hEE!)

[Mentat]

Originally posted by Mr. Robin Parsons
Yes, but it also tells you that the universe cannot exist in the same state twice, ergo it is a singularity of sorts inasmuch as the state of the universe at any given time is the only point in any time that it will exist that way, hence if you are existent NOW, then the past is NOT available to you as time travel is impossible, as you cannot travel through that which doesn't actually exist. (You cannot travel through an "Idea"....'cept in your mind hee-hEE!)

Sooooo....you're agreeing that we can't travel through time, right?

[phoenixthoth]

i think i know what you mean by "the past doesn't exist" but i may not. either way, how do you know that?

[Mr. Robin Parsons]

Originally posted by Mentat
Sooooo....you're agreeing that we can't travel through time, right?
Agreeing?? with whom??

[Mentat]

Originally posted by Mr. Robin Parsons
Agreeing?? with whom??

With...me?

[Jeebus]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

When you say you are referring time travel into the past your argument could fail right then before you even propose the P1 standard. All you would have to say is:

(i) "Time present and time past
Are both perhaps present in time future."

Counterresponse (1) - However, time travel is quite strange to begin with, and it does not appear to be a terribly strong additional argument against time travel that it has strange consequences.

(ii) But in order for time travel to occur the event has to take place. Thus the strange consequences of structure imposes constraints on states on space-like surfaces. However, space-time and matter interact. Suppose that one is in a space-time with closed time-like lines, such that certain counterfactual distributions of matter on some neighborhood of a point p are ruled out if one holds that space-time structure fixed.

Either way you come back to that "Time present and time past
are both perhaps present in time future" statement continuum of Time Travel.

[Mentat]

Originally posted by Jeebus
When you say you are referring time travel into the past your argument could fail right then before you even propose the P1 standard. All you would have to say is:

(i) "Time present and time past
Are both perhaps present in time future."

Counterresponse (1) - However, time travel is quite strange to begin with, and it does not appear to be a terribly strong additional argument against time travel that it has strange consequences.

(ii) But in order for time travel to occur the event has to take place. Thus the strange consequences of structure imposes constraints on states on space-like surfaces. However, space-time and matter interact. Suppose that one is in a space-time with closed time-like lines, such that certain counterfactual distributions of matter on some neighborhood of a point p are ruled out if one holds that space-time structure fixed.

Either way you come back to that "Time present and time past
are both perhaps present in time future" statement continuum of Time Travel.

I don't understand what "time present and time past are both time present in the future" means...that's just completely losing me. Please explain further.

[Jeebus]

Originally posted by Mentat
I don't understand what "time present and time past are both time present in the future" means...that's just completely losing me. Please explain further.

Alright, let me see here.

"The time present and time past are both time present in the future" basically means that even if you are in the past, which you concluded in your example, you technically never left the present or the future. Since you inevitably are in the past - you can still hop in between the present and the future because your origin started from the present.

[Sniper__1]

all time past present and future coexist right now but the only way to travel through time is through quantum teleportation which would have you stuck in different realities forever no matter how small the difference or how big the difference. (like if you went to 1950 the nazis might have won the war in the reality you would then exist in and the world would be different) and you however would still exist in the time you started because you didnt really leave you created another of your self and he left to a time and reality where you didnt already exist thus quantum mechanics explains that time travel is possible and impossible in one single bound



confusing huh

[Iacchus32]

If time travel were ever possible, then we are already living in the past, because it would already have occurred.

Or, would we then be living in the future, as a future event, of whoever traveled backwards in the past?

So, has anyone yet to hear of such things? Remember, if it were possible, it would have already happened, and continue to happen, even as we speak.

Or, could this be a possible means by which to account for some of our alien and UFO sightings?

[Mr. Robin Parsons]

Originally posted by Mentat
(SNIP) With...me? (SNoP)
Are you sure you don't mean the British Scientist who was promoting that Idea, back in the early ninties, he was called 'Radical' for it apparently, although I suspect he won greater acceptance, if to only the question of it, "time" that is, the question of the "existence" (or Non-existence) of time

[Sniper__1]

but Iacchus as i explained when you traveled you would be in a different reality so chances are we wouldnt hear about until they found a way to control which reality they went to which i believe would be impossible. oh and yes we are the past present and future all in one right now.

And mr robin parsons i think time does not exist as again i have stated before.[t)]

[Mentat]

Originally posted by Jeebus
Alright, let me see here.

"The time present and time past are both time present in the future" basically means that even if you are in the past, which you concluded in your example, you technically never left the present or the future. Since you inevitably are in the past - you can still hop in between the present and the future because your origin started from the present.

Still don't got it...sorry, but I don't understand what you're trying to say.

We can travel throughout the past, because it's all "the past" to "the future"?

[Mentat]

Originally posted by Sniper__1
all time past present and future coexist right now but the only way to travel through time is through quantum teleportation which would have you stuck in different realities forever no matter how small the difference or how big the difference. (like if you went to 1950 the nazis might have won the war in the reality you would then exist in and the world would be different) and you however would still exist in the time you started because you didnt really leave you created another of your self and he left to a time and reality where you didnt already exist thus quantum mechanics explains that time travel is possible and impossible in one single bound



confusing huh

Sniper, your very first sentence contained a huge semantic error, and I think that error is corrupting your later ideas. You said that past, present, and future are coexisting right now. The term "now" refers only to the present. I'm not both here and there at the same time, otherwise the purpose of the terms "here" and "there" would lose their meaning. In like manner, I'm not both "then" and "now" otherwise this distinction would be completely meaningless, and everything would be happening in the present (the sinking of the Titanic, both World Wars, even the Big Bang itself).

[Royce]

Mentat, remember way back in March when I first joined PF, you and I got in a discussion about time being a dimension, a real dimension?
I said that there is only one time and one time dimention that exists. The past, present and furture all exist along this dimension; but, as we are only 3 dimensional beings we cannot see or experience other than now; and we are compeled to travel along that dimention at whatever speed it is we are traveling and at whatever direction we are traveling.
Einstein showed that time is relative to the observer and interestingly time showed up negative in his relativity equations. If this has any significance or not I don't know; but, everybody including Einstein himself just ignored that fact.
In order for time travel to be possible in one universe then there must be one time in one (the 4th) dimension and all of time must exist at all times along that dimension. Time travel would then be traveling along that dimension; or, jumping out or off of our time line and jumping back in or on at another location. If this were possible then it would already be in our historic past whether known or not, or if would already be in our future history. Another facet of this one time idea is that to me it would make the universe determinate as our future already exists and we would be compelled to live it as it happens; but, others who believe this say that it doesn't, that we have, can and do exercise free will. This is illogical to me unless the future already includes our choices but then are we really choosing freely?
In one very real way we are all time travelers, traveling along our time line from our past to our future but always experiencing it as our present.

[Mentat]

Originally posted by Royce
Mentat, remember way back in March when I first joined PF, you and I got in a discussion about time being a dimension, a real dimension?
I said that there is only one time and one time dimention that exists. The past, present and furture all exist along this dimension; but, as we are only 3 dimensional beings we cannot see or experience other than now; and we are compeled to travel along that dimention at whatever speed it is we are traveling and at whatever direction we are traveling.
Einstein showed that time is relative to the observer and interestingly time showed up negative in his relativity equations. If this has any significance or not I don't know; but, everybody including Einstein himself just ignored that fact.
In order for time travel to be possible in one universe then there must be one time in one (the 4th) dimension and all of time must exist at all times along that dimension. Time travel would then be traveling along that dimension; or, jumping out or off of our time line and jumping back in or on at another location. If this were possible then it would already be in our historic past whether known or not, or if would already be in our future history. Another facet of this one time idea is that to me it would make the universe determinate as our future already exists and we would be compelled to live it as it happens; but, others who believe this say that it doesn't, that we have, can and do exercise free will. This is illogical to me unless the future already includes our choices but then are we really choosing freely?
In one very real way we are all time travelers, traveling along our time line from our past to our future but always experiencing it as our present.

I disagree with only one point, Royce, and it's mainly to do with wording. Yes all events that happened in the past exist on the time line, but they do not exist "now", since now is the present. So, if I were to leave the time line (though I don't really see how you could, since it would take a certain amount of "time" to go in and out of the "line" wouldn't it?), I would not see infinite frames of the Universe at different points in time, but would see that the entire Universe (except, perhaps, tachyons and the like) are moving in one direction along this axis, at one speed or another. Therefore, our futures cannot be set, and our pasts are only set in that they are the past, and changing something is in the future tense (meaning that the idea of "changing" something, is the idea of taking something that exists now, and making it different; whereas the past has existed, and does not exist anymore, and can thus not be changed).

[Mr. Robin Parsons]

Originally posted by Sniper__1
And mr robin parsons i think time does not exist as again i have stated before.[t)]
Humm since in your profile it says you were born in 1989, and there was a British Scientist promoting this idea in the Early 90's (while you were still learning....) I would expect (false?/wrong?)your statement is simply one of your offer(ing) of 'your voice' (too) to the growing concensus, (?)

[Mentat]

Originally posted by Sniper__1
And mr robin parsons i think time does not exist as again i have stated before.[t)]

Are you sure you stated it "before", Sniper? If you stated it before the time of stating this post, then there is time. If there is no time, OTOH, there is a perfectly logical reason for Mr. Parsons to not have gotten your point to your satisfaction, you haven't said it yet, are still saying it, and have said it...all at the same time. I think I like the first scenario better [;)].

[Mr. Robin Parsons]

Oh yes, BTW the past, the present and the future are all here/now as all of the atoms that were there in 1776 are still here and in use, just slightly altered, as are all of the other past particulate participants, and all of the Future ones too, right here, right now, just awaiting thier chance to present themselves according to there "time"..........atoms (and molecules) all.

[selfAdjoint]

Well, some of the uranium atoms have decayed into lighter atoms, and so forth, some of the hydrogen atoms have become helium too.

[Mr. Robin Parsons]

Originally posted by selfAdjoint
Well, some of the uranium atoms have decayed into lighter atoms, and so forth, some of the hydrogen atoms have become helium too.
O.K. but tell me something (perhaps) more important, has the total amount of energy in the entirety of the Universe changed, if so, how?, if not, why?

[Mentat]

Originally posted by Mr. Robin Parsons
Oh yes, BTW the past, the present and the future are all here/now as all of the atoms that were there in 1776 are still here and in use, just slightly altered, as are all of the other past particulate participants, and all of the Future ones too, right here, right now, just awaiting thier chance to present themselves according to there "time"..........atoms (and molecules) all.

Fine, but if they are "slightly altered", then there is a distinct difference between future, past, and present...future is when particles are "slightly altered" relative to past.

[Mentat]

Originally posted by Mr. Robin Parsons
O.K. but tell me something (perhaps) more important, has the total amount of energy in the entirety of the Universe changed, if so, how?, if not, why?

The total amount of energy in the Universe should have a greater percentage that has been distributed as "random movement" (="heat"), as per the Second Law of Thermodynamics...right?

[Mr. Robin Parsons]

Originally posted by Mentat
The total amount of energy in the Universe should have a greater percentage that has been distributed as "random movement" (="heat"), as per the Second Law of Thermodynamics...right?
Why? hasn't lots of it become, well, you, me, the rest of all of the Fusioned productions of atoms that have gone on for how many billions of years now, in the Star's core(s)??

[Infomeantion]

--------------------------------------------------------
Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...
---------------------------------------------------------

Are you trying to prove that time travel is nonsensical or if your reasoning is? You have two contradictory statements. If those statements are the only information to go by, then both of them are meaningless. If you add more information to your speculation, you can come up with reasoning to support that it is sensical or nonsensical, either way. But in the limited context of those four statements, it's just contradictory.

What I tend to think of though, in addition to this, is that you might rephrase it the following (unless you are omniscient, which as I heartell from the crazy information theory people is possible because there is a finite amount of information in the universe):

One universe, possible:
1: I didn't know I existed in 1776.
2: I know I exist in the reality I'm in right now.
3: Then I went back in time to 1776.
4: Now, I know if I were to transport myself back to that old reality that I mentioned in 2, that I existed in 1776.

The point is that you as a person have less than total information about the universe. If you don't contradict that (which I'd be surprised if you wholeheartedly did), then the first statement as you state it would not have the full meaning of absolute truth, although I'm sure that you could probably get a lot of people to agree with you if that is the thing you are after. Not I, however...how do I know that you aren't some computer intelligence just posturing as a person? I'm not saying that I think any of these is likely to me (I am not running to the newspapers about a time-traveling machine intelligence), but I cannot wholeheartedly assert my absolute knowledge of anything. Maybe you can, and maybe you are omniscient too.

[Mentat]

Originally posted by Mr. Robin Parsons
Why? hasn't lots of it become, well, you, me, the rest of all of the Fusioned productions of atoms that have gone on for how many billions of years now, in the Star's core(s)??

Sure, lot's of it has. But for every congealed mass created in space (like stars and planets) a greater amount of heat is given off, than order is established.

"then" to "than"

[Mentat]

Originally posted by Infomeantion
One universe, possible:
1: I didn't know I existed in 1776.
2: I know I exist in the reality I'm in right now.
3: Then I went back in time to 1776.
4: Now, I know if I were to transport myself back to that old reality that I mentioned in 2, that I existed in 1776.

The point is that you as a person have less than total information about the universe.


You forget that the time of my postulating that I didn't exist in 1776 is before the time of my changing that. I got into a time machine, after having existed in a reality wherein I didn't exist in 1776 (as per P2). Now, if I did exist in 1776, then that's fine, but that means that I already existed there, in spite of my never having gotten in a time machine (yet).


If you don't contradict that (which I'd be surprised if you wholeheartedly did), then the first statement as you state it would not have the full meaning of absolute truth, although I'm sure that you could probably get a lot of people to agree with you if that is the thing you are after.


I'm after a fuller understanding. I don't expect to be right about this particular deduction, since there are so many respected people who still believe it to be possible-in-principle to travel backward in time. I'm just waiting for this deduction to be refuted, not for it to be accepted.


Not I, however...how do I know that you aren't some computer intelligence just posturing as a person?


But I am a computer intelligence...so are you.

[Infomeantion]

Allow me to try to rephrase how I initially read this thread's first post, which is essentially one argument nested within another. One, which I'll call 'Argument A', is the internal consistency of your reasoning with P1, P2, P3 and C. You show plainly that the argument is self-contradicty, with C contradicting P1 and P2 (although I don't think it contradicts P3 but that doesn't really matter). The second argument can be shown as follows:

Premise: Argument A is contradictory.
Proposition: Time travel's possibility relies on Argument A not
being contradictory.
Conclusion: Time travel is not only impossible, but non-sensical.

I agree with the premise that Argument A is contradictory. Your conclusion definitely contradicts your first and second propositions. But the proposition above, that time travel relies on Argument A, I believe not to be true. By including your 'limited information' in your role of Argument A, I was trying to show you that it does not mean that your conclusion is necessarily false, but rather that your premise could have been false. Either way, Argument A is contradictory, but not necessarily applicable to the possibility of time travel. Does this make more sense?

[Mr. Robin Parsons]

Originally posted by Mentat
Sure, lot's of it has. But for every congealed mass created in space (like stars and planets) a greater amount of heat is given off, than order is established.
Humm, proof of that?

[Mentat]

Originally posted by Infomeantion
Allow me to try to rephrase how I initially read this thread's first post, which is essentially one argument nested within another. One, which I'll call 'Argument A', is the internal consistency of your reasoning with P1, P2, P3 and C. You show plainly that the argument is self-contradicty, with C contradicting P1 and P2 (although I don't think it contradicts P3 but that doesn't really matter). The second argument can be shown as follows:

Premise: Argument A is contradictory.
Proposition: Time travel's possibility relies on Argument A not
being contradictory.
Conclusion: Time travel is not only impossible, but non-sensical.

I agree with the premise that Argument A is contradictory. Your conclusion definitely contradicts your first and second propositions. But the proposition above, that time travel relies on Argument A, I believe not to be true. By including your 'limited information' in your role of Argument A, I was trying to show you that it does not mean that your conclusion is necessarily false, but rather that your premise could have been false. Either way, Argument A is contradictory, but not necessarily applicable to the possibility of time travel. Does this make more sense?

Indeed it does. However, could you please explain to me how time travel doesn't rely on its possibility being deductively valid?

[Mentat]

Originally posted by Mr. Robin Parsons
Humm, proof of that?

As much proof as I have that we there are planets orbiting other stars...I've been told, and I've read.

[Mr. Robin Parsons]

Originally posted by Mentat
As much proof as I have that we there are planets orbiting other stars...I've been told, and I've read.
Sorry but your first statement is a little confusing...(sp? possibly?) but to the second one, me too, but I don't believe everything that I have read, I have had many a years to both read, remember re-digest, think, and come to conclusions concerning an array of areas of knowledge.

So tell me then, what is "chaotic" about heat? how is it that the disspation of temperature is seen as a "chaotic event" overburdoning to the extent of overwhelming the very real increase in order that is going on inside stellar bodies, and then tell me how much heat a galaxy bleeds off in comparison to the Order generated within that structure........and more, when your ready............

[Mentat]

Originally posted by Mr. Robin Parsons
Sorry but your first statement is a little confusing...(sp? possibly?) but to the second one, me too, but I don't believe everything that I have read, I have had many a years to both read, remember re-digest, think, and come to conclusions concerning an array of areas of knowledge.


Well, I skip the "come to conclusions" part, since I like to remain open, but I agree that this is the typical method. It's "education", and is necessary.

As to the first statement, I was just saying that I have enough proof that heat, greater than the quantity of congealed mass, is released when said mass congeals.


So tell me then, what is "chaotic" about heat? how is it that the disspation of temperature is seen as a "chaotic event" overburdoning to the extent of overwhelming the very real increase in order that is going on inside stellar bodies, and then tell me how much heat a galaxy bleeds off in comparison to the Order generated within that structure........and more, when your ready............

I don't know how much heat "bleeds off", I've just read that it's greater than the amount of mass that congeals.

You ask "what's so chaotic about heat", my response is: The heat!

"Heat", by a physicist's definition is random movement of particles.

[Mr. Robin Parsons]

Originally posted by Mentat
(SNIP) "Heat", by a physicist's definition is random movement of particles. (SNoP)[/B] Oh, so then it is NOT "Ambient Energy Pressure" you know, what a thermometer reads.........cause heat is something that occurs between atoms, the release of the atoms energy/EMR, and causes them to increase/decrease in motion relatively, cause and effect, just 'looks' "random" but follows all the rules like it is supposed to.

[Mr. Robin Parsons]

Originally posted by Mentat
(SNIP) As to the first statement, I was just saying that I have enough proof that heat, greater than the quantity of congealed mass, is released when said mass congeals. (SNoP)
Humm, lets see, debating tactics, distract your opponents attention by diverting from subject matter in an innocent looking enough manner.......we had been talking (least I was) about the Fusion reactions going on inside "stellar bodies" remember that?, not congealing masses that are releasing heat, aside, have you proof of that "Heat V Order" relativity in/concerning a galaxy?

[Mentat]

Originally posted by Mr. Robin Parsons
Oh, so then it is NOT "Ambient Energy Pressure" you know, what a thermometer reads.........cause heat is something that occurs between atoms, the release of the atoms energy/EMR, and causes them to increase/decrease in motion relatively, cause and effect, just 'looks' "random" but follows all the rules like it is supposed to.

Rules?

Besides, what exactly are you getting at with this post?

[SmarterThanGod]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

You could go by a predestination assumption, in which case, you would have existed in P1 and P2 before you were even born, because in the future, you will travel back to 1776, and since this must have already happened before you were even born, P1 would be false before you travelled back to 1776, and therefore, the present reality would include the events that happened to you in 1776, though you may not remember them, they are technically your past AND future. The main assumption here is that all events in the universe are predestined, and therefore that you cannot change the future because it is included in your present. Anythign you do while in 1776 will ALREADY be included in the present universe, so the outcome will never change.
This may have been mentioned already in another reply, but I am tired, and have only read the first post, so sorry if I am redundant

[Mr. Robin Parsons]

Originally posted by Mentat, on page 5
The total amount of energy in the Universe should have a greater percentage that has been distributed as "random movement" (="heat"), as per the Second Law of Thermodynamics...right?

Originally posted by Mentat
Rules? Yes rules, heat a gas, and it expands, yes! rules!
chemistry and physics are all about "The Rules" and we don't really "write" them.....
Besides, what exactly are you getting at with this post?
To the [ b]'d See the above, your question, and what (it) followed it...

[hey.like]

Time system is not in future past and nowonly , but in space time , it is exist in a semi-dimension. to move in this semi-dimension and take the university strong power, it is ony way to exceed the light to travel. as the time system is one only. it isn't in time value travel but in dimension and to borrow the space-time unit action to arive a far away distance.

[hey.like]

Why the time travel is to go in time , it is semi-dimension as the first event. to return , first to face the first event. it is no mean.
If to take the mass system time help, it is enable and the time is in some progress only. but the livethings to front is in the right time direction . it is hard to fact the against time direction.

[Silverious]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

I was wondering, why you would assume you did not exist in 1776.

But, assuming P1 and P2 are correct. P3 could never have happened.

But assuming P3 DID take place, C is correct, P1 is false, and P2 would have to be modified. Because, at every time interval before P3, P1 and P2 are entirely correct. But once P3 takes place, you exist now in 1776.

I think you assumed too much, which is the main cause of the contradiction. But what do I know?

[olde drunk]

let's approach with a 'reasonable' basis.

a)i exist in 2004
b)i existed in 1950
c) i can travel back to 1950

hmmmm? how many times have you seen two family members talk about a past event? dick and jane were married on a saturday; the weather was misty, friend Spot attended.

now, when dick and jane discuss that day/event, they have two different views of events. regardless of the circumstances they vehementally disagree.

i submit that they each are travelling back to a 'probable past'. each is revisting the past that they experienced. i further submit, that when we can accept this possibilty, we will get closer to actual time travel.

imho, all pasts, presents and futures exist as probablities or potential experiences. it is because we narrow our focus into a very fine 'present' that we negate our ability to visit the past or future. we see clues when we dream of of a future and it becomes a reality to be experienced.

in my construct, the past and future are there for us to visit when we develop full powers and prepare the human awareness for the experience. anyone who said they did today would be labled as a nut. also, are dreams a less valid reality?? are my rememberances of a past event lass valid than my conscious present???


peace,

[Sikz]

The thing with time travel is definitions.

"P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ..."

The contraversy here is the definition of "I". Is the you who goes back the same you who is there? This is why there is not as yet (to my knowledge) any undeniable logical proof against time travel- they are all based on contraversial axioms.

[Mentat]

Originally posted by SmarterThanGod
You could go by a predestination assumption, in which case, you would have existed in P1 and P2 before you were even born, because in the future, you will travel back to 1776, and since this must have already happened before you were even born, P1 would be false before you travelled back to 1776, and therefore, the present reality would include the events that happened to you in 1776, though you may not remember them, they are technically your past AND future. The main assumption here is that all events in the universe are predestined, and therefore that you cannot change the future because it is included in your present. Anythign you do while in 1776 will ALREADY be included in the present universe, so the outcome will never change.
This may have been mentioned already in another reply, but I am tired, and have only read the first post, so sorry if I am redundant

No, yours is a very good point. However, the real question is: If P1 and P2 are true, then is it possible to travel backward in time?

[Mentat]

Originally posted by Sikz
The thing with time travel is definitions.

"P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ..."

The contraversy here is the definition of "I". Is the you who goes back the same you who is there? This is why there is not as yet (to my knowledge) any undeniable logical proof against time travel- they are all based on contraversial axioms.

There can be only one "I", as that is what the whole semantic purpose of the term "I" is, ITFP.

[Mentat]

Originally posted by Silverious
I was wondering, why you would assume you did not exist in 1776.

But, assuming P1 and P2 are correct. P3 could never have happened.

But assuming P3 DID take place, C is correct, P1 is false, and P2 would have to be modified. Because, at every time interval before P3, P1 and P2 are entirely correct. But once P3 takes place, you exist now in 1776.

I think you assumed too much, which is the main cause of the contradiction. But what do I know?

I may have assumed "too much", but I may have assumed "just enough". You see, if I existed in 1776, then I am predestined to travel there, and thus there is no contradiction, as SmarterthanGod has pointed out. However, with the assumptions as stated, I have to assume your last paragraph is flawed. The reason I say this is: If P1 is true before P3 takes place, then P3 cannot take place (logically). Thus, if P1 is ever true, P3 is never true.

[confutatis]

Originally posted by Mentat
When I say "Time Travel" in the title, I'm referring to traveling into the past. I just wanted to see if I could establish deductive validity for my assumption that it is not just impossible, but non-sensical, to travel backward in time.

("P" stands for "Proposition" and "C" stands for "Conclusion")

Here we go:
P1: I did not exist in 1776.
P2: I exist now in a reality that includes P1 as being true.
P3: I go back in time (using whatever means) to 1776.
C: I did exist in 1776! ...

But, then, I have invalidated P1 and P2, and even (by extension) P3, so my conclusion violates all the propositions...is this logically sound?

Any and all helpful criticism is appreciated.

The problem with this issue is that you can't say something cannot happen because it's illogical. In fact, history is full of episodes when actual observation contradicted the logic of the time. The key point here, unseen by many people, is that logic does not apply to reality, it only applies to the way we think about reality. People who believe time travel may be possible are not entirely wrong; however, if what we loosely think of today as "time travel" turns out to be possible, then the skeptics will prove their point: whatever it is, it can't be called "time travel".

Mentat, I suggest your approach to the problem is slightly wrong, because you are not fully taking into account the way we think. Here's how I see the problem:

At any given point in time, I am aware of a certain amount of historical knowledge. One such piece of knowledge is "I did not exist in 1776". This is very much what you say in P1 and P2, with an important difference: the emphasis on "what I know" as opposed to "what is true".

Now suppose "something" happens (let's leave that undefined for now), and suddenly you acquire a new piece of knowledge that says "I did exist in 1776". You have a problem now, because two pieces of knowledge contradict each other. By the way, this is an extremely common occurrence in our daily lives, so the solution shouldn't be that difficult.

Let's examine a somewhat similar situation: At some point in your life, the statement "I have never been to Atlanta" was true. Then another "something" happened, and the statement "I have been to Atlanta" becomes true. Do you have a problem now? Replace "have been" with "existed" and think about the difference between Atlanta and 1776. Particularly why it's possible to be and not to be in Atlanta, while the same cannot be said about 1776. It's very interesting if you approach it from a particular perspective, as it reveals something about time.

The reason you can be and not be in Atlanta, the reason the two pieces of knowledge do not seem paradoxical to you, is because you already know the solution to situations like that. And the solution involves a concept called... time! "Time" is what allows two apparently contradictory statements to be true.

Back to time travel. Can it be possible? I say it can, only not the way you think about it. In order to explain how you can be and not be in 1776, you need the same concept you use to explain how you can be and not be in Atlanta: you need "time". So time travel is possible if you can "travel" through "time 1" using "time 2". In other words, time travel is perfectly possible as long as there are two or more time dimensions.

I suspect a question still remains: can we prove time travel is impossible if there is only one time dimension? And here the answer sounds too obvious to me: if there is only one dimension of time, then you can only travel from 2004 to 1776 by going through every single moment in between. You can't jump from 2004 to 1776 without first going through 2003, 2002, 2001, and so on. Now what happens when you go back through those years? If there's only one dimension of time, you already know the answer.

[Mentat]

Originally posted by confutatis
The problem with this issue is that you can't say something cannot happen because it's illogical. In fact, history is full of episodes when actual observation contradicted the logic of the time. The key point here, unseen by many people, is that logic does not apply to reality, it only applies to the way we think about reality. People who believe time travel may be possible are not entirely wrong; however, if what we loosely think of today as "time travel" turns out to be possible, then the skeptics will prove their point: whatever it is, it can't be called "time travel".

Mentat, I suggest your approach to the problem is slightly wrong, because you are not fully taking into account the way we think. Here's how I see the problem:

At any given point in time, I am aware of a certain amount of historical knowledge. One such piece of knowledge is "I did not exist in 1776". This is very much what you say in P1 and P2, with an important difference: the emphasis on "what I know" as opposed to "what is true".


But I didn't say that I knew I didn't exist in 1776, merely that I didn't. There's a difference. And as to reality contradicting logic, that is not true, and literally cannot be. You see, for anything that takes place, there is a logical framework that allows it.


The reason you can be and not be in Atlanta, the reason the two pieces of knowledge do not seem paradoxical to you, is because you already know the solution to situations like that. And the solution involves a concept called... time! "Time" is what allows two apparently contradictory statements to be true.

Back to time travel. Can it be possible? I say it can, only not the way you think about it. In order to explain how you can be and not be in 1776, you need the same concept you use to explain how you can be and not be in Atlanta: you need "time". So time travel is possible if you can "travel" through "time 1" using "time 2". In other words, time travel is perfectly possible as long as there are two or more time dimensions.

I suspect a question still remains: can we prove time travel is impossible if there is only one time dimension? And here the answer sounds too obvious to me: if there is only one dimension of time, then you can only travel from 2004 to 1776 by going through every single moment in between. You can't jump from 2004 to 1776 without first going through 2003, 2002, 2001, and so on. Now what happens when you go back through those years? If there's only one dimension of time, you already know the answer.

Yeah, I'd considered the dual time-dimension idea (btw, Kudos on your explanation, it was really good...I hadn't looked at in quite the same manner before), but disqualified it for reasons of Occam's Razor and my own distaste for ad hoc arguments.

Finally, in that last paragraph you seem to be describing a regressive type of time travel, wherein everything - including the Time Traveller - regress to former states. You are right, of course, that this is both impossible and non-sensical (especially since, if the time traveller goes back to any time before the time that he started going back, he is no longer going back, but forward as always), but I was also hoping to show that, even if we make the Traveller immune to the consequences of regressive time, it is still impossible and non-sensical to postulate backward time travel.