posted
Someone else said somethign about time travel in a recent post I think about a book they were making or something I don't actually know, but it did make me want to bring this up.
My arguement; The past present and future are all set to happen exactly as they do and cannot be changed.
For instance; the future is a product of the past and present times.
What if I went back and killed my father before he seeded my mother? By far one of the strangest examples of time travel eh, this simply cannot be done, by killing your father you would have never been born to concieve killing your father before your were seeded.
Not to mention, you just cannot time travel. Even going faster than the speed of light, would only dialate time and slow down the passing for yourself, not reverse it.
The future is unchangeable because it's always the product of past and present, meaning no mater what you do it were already to happen in the future.
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posted
But if the future is the product of the past and present then what I choose to do right now immediately alters that product. You might be able to argue that the future is set in that the actions we are going to take will inevitably happen, and no outside observer is truly acting independent of that.
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quote:what I choose to do right now immediately alters that product
Unless what you choose would always be the same, again based on past circumstances; "choose" just being a shorthand for the operations that occur in your brain that you are aware of.
One other thing that could cause the future to not be fixed would be some truly random phenomenon.
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posted
First of all you are somehow confusing two different issues, that of timetravel, and that of determinism. The one doesn't particularly relate to the other.
quote:What if I went back and killed my father before he seeded my mother? By far one of the strangest examples of time travel eh, this simply cannot be done, by killing your father you would have never been born to concieve killing your father before your were seeded.
Or alternativeely you create a new universe in which your father is dead, while the old universe keeps going with you absent from it. No paradox there.
Or the previous universe is deleted, but why should this affect the time-traveller's contributions to the new universe? No paradox there either. The new universe (and the time-traveller) exist, the old universe doesn't.
A program can rewrite itself, or run a new instance of itself with its calculated data and then delete its previous instance, and that's not a paradox, it remains deleted or rewritten.
So if we see the whole of the universe as a program with data, why shouldn't a universe be able to rewrite itself, load past versions of its stored data and resume execution using both its past stored data and "future" data from the previous execution?
You assume that there's only one instance of the universe and it can only be run once. But programs don't have that limitation, so why should universes?
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quote:One other thing that could cause the future to not be fixed would be some truly random phenomenon.
If the Many-Worlds interpretation of Quantum Mechanics is real, then all the possible futures exist, but which one we'll get to see isn't fixed (in the sense that alternate versions of ourselves will see each universe)
If the Copenhagen interpretation is correct, random events happen all the time, and the future isn't fixed at all.
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The main division for this thread is the "what you do in the past is what you've always done" with the "what you do in the past creates a new universe" a la the new Star Trek and the "what you do in the past changes everything."
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posted
I'm with Matt. I believe "choice" is an illusion; that all men are slave to their experiences and perceptions. As to how this relates to time travel, there are possibilities with a branching universe. It goes like this. Bob and Chrissy have a son, Darren, who grows up, time travels back to before his birth, and kills his father. This action creates a fork in the timeline, two "roads," one with Darren born, one without. The adult Darren changed the circumstance around his parents, and so a second outcome occurred. Since the total circumstance is different, different "choices" are made. This differs from a quantum choice universe in that the only branchings in the timeline are those created by time travel. Since choice isn't really choice, only these jumps, which alter total circumstance, create branchings.
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quote:"I believe "choice" is an illusion; that all men are slave to their experiences and perceptions. "
All men *are* their experiences and perceptions and biologies, so they're slaves to themselves?
Somehow who's only enslaved to their own nature, don't we tend to call these men "free"?
The question of free will is largely a meaningless question.
quote: Since choice isn't really choice, only these jumps, which alter total circumstance, create branchings.
The number of universe branchings isn't related to the question of choice. A river that splits in two doesn't give its water molecules "choice", and neither does a river that doesn't split.
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posted
Oh, god. Another high schooler who thinks he's smarter than everyone.
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Blayne Bradley
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posted
Uuuuh Rawrain:
If I put a cat into a box and set an trigger to the measured decay of an isotope so that its exactly 50% chance that it will trigger or not and once triggered releases a toxic nerve agent that would horrifically kill the cat and the box is sealed in such a way that you cannot see, hear, or percieve in ANY way what goes on in the box.
Is the cat alive or dead?
In quantum physics the answer is that the cat is alive and dead at the sametime, both quantum states according to the math are valid until the moment we look into the box, at which point the waveform collapses and it has a definate solution.
The samething applies to the future, it has no definate state, in theory everything in the future MAY or MAY NOT happen, usually we have a good idea what something will happen but thats because its usually not perfect 50/50s but sometimes 90/10s.
The future is not set in stone.
As for changing the past, according to the math as done by the Novikov's Self Consistency Principle its actually possible to go back in time and make MINOR changes, essentially if you through a golf ball into a wormhole that travels into the past in precisely the time/place to intercept and knock the ball out of your hand before you could through it in, the best that could happen is that yould knock the golf ball into a slightely different course into and out of the wormhole but is still mostly the same.
So you may kill your grandmother but someone else will have sex with your mother (probably me) and give birth to you.
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quote:Originally posted by Blayne Bradley: Uuuuh Rawrain:
If I put a cat into a box and set an trigger to the measured decay of an isotope so that its exactly 50% chance that it will trigger or not and once triggered releases a toxic nerve agent that would horrifically kill the cat and the box is sealed in such a way that you cannot see, hear, or percieve in ANY way what goes on in the box.
Is the cat alive or dead?
In quantum physics the answer is that the cat is alive and dead at the sametime, both quantum states according to the math are valid until the moment we look into the box, at which point the waveform collapses and it has a definate solution.
The samething applies to the future, it has no definate state, in theory everything in the future MAY or MAY NOT happen, usually we have a good idea what something will happen but thats because its usually not perfect 50/50s but sometimes 90/10s.
The future is not set in stone.
As for changing the past, according to the math as done by the Novikov's Self Consistency Principle its actually possible to go back in time and make MINOR changes, essentially if you through a golf ball into a wormhole that travels into the past in precisely the time/place to intercept and knock the ball out of your hand before you could through it in, the best that could happen is that yould knock the golf ball into a slightely different course into and out of the wormhole but is still mostly the same.
So you may kill your grandmother but someone else will have sex with your mother (probably me) and give birth to you.
Your cat story actually makes me think about lottery tickets, soemthing weird I always thought when I was a kid, before scratching are the numbers and digits changing? No I know they aren't but doesn't appear so if it were truely random.
as for other things being said, if the future is the result of what I do now, then in fact it doesn't change. even if I stopped breathing and died right now, the future would already have my death added directly as I did...
Also from what I know computers are incapable of making random answers even things that appear random are in fact as a result of a process
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quote:In quantum physics the answer is that the cat is alive and dead at the sametime, both quantum states according to the math are valid until the moment we look into the box, at which point the waveform collapses and it has a definate solution.
That's the Copenhagen interpretation.
The Many Worlds interpretation says that the waveform never collapses in any absolute terms, it only "collapses" in relation to the observer -- which means that when the box opens the whole cat-observer system will possess two states (one in which observer sees a dead cat, and one in which the observer sees a live cat).
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posted
Rawrain, you're talking about the hidden variables theory. I suggest you look that up.
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Blayne Bradley
unregistered
posted
quote:Originally posted by Aris Katsaris:
quote:In quantum physics the answer is that the cat is alive and dead at the sametime, both quantum states according to the math are valid until the moment we look into the box, at which point the waveform collapses and it has a definate solution.
That's the Copenhagen interpretation.
The Many Worlds interpretation says that the waveform never collapses in any absolute terms, it only "collapses" in relation to the observer -- which means that when the box opens the whole cat-observer system will possess two states (one in which observer sees a dead cat, and one in which the observer sees a live cat).
posted
The arguement is whether the cat is pressumed to be in the future dead or alive, which can only be known by seeing the cat dead or alive
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posted
Was anyone else highly disappointed by the fact that this thread has nothing to do with logical fallacies?
Also, David Lewis has a cute account of time travel in terms of four-dimensions that seems to make it work. I haven't read enough else to say whether it's a good argument in terms of the contemporary literature, but it is certainly cute and he was a genius, so those factors combined make me like it.
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posted
Who loves A Wrinkle in Time? I sure do. That and A Wind in the Door were two of my favorite childhood reads.
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quote:Originally posted by Aris Katsaris: All men *are* their experiences and perceptions and biologies, so they're slaves to themselves?
Somehow who's only enslaved to their own nature, don't we tend to call these men "free"?
The question of free will is largely a meaningless question.
One could state that men are slaves to themselves. However, the implication in that statement is that men are also their own masters. What we call choice is merely the final result of a series of logical processes, some conscious, some subconscious. What appears to be a choice, isn't. A theoretical perfect observer with perfect knowledge could predict the outcome of every choice I make. With perfect accuracy. And could theoretically force the choices I make by adding influences to my life. The same, I believe, is true of everything. When we express ignorance of the outcome of anything, all we are expressing is incomplete knowledge of the inputs. A coin toss comes up heads 50% of the time, but if we knew the force of spin and toss, atmospheric conditions, and the catch angle and moment with perfect precision, we would know the result before the toss. Similarly, I believe that the actions of a single atom are predictable if we had complete and perfect knowledge. But we don't, so it appears random.
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quote:A theoretical perfect observer with perfect knowledge could predict the outcome of every choice I make. With perfect accuracy. And could theoretically force the choices I make by adding influences to my life. The same, I believe, is true of everything.
It's not true of electrons.
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posted
I believe it's possible that choices are also random on some basic level, but "my choices are random" is not any more impressive to me than "my choices are predetermined by physics."
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Right. Choice isn't any less an illusion if it's the indirect of the random actions of subatomic particles than if it's a result of non-random events describable through quantum physics.
There is a huge difference though in that in one case all events are predetermined by first cause(s) while in the other case they may vary based on random influences, though obviously still constrained within certain bounds.
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quote:Originally posted by The Rabbit: It's not true of electrons.
I believe it is. Our current understanding of the movement of electrons is insufficient to predict the movements, or even to discern a pattern. But then again, our understanding of everything changes. Planetary movements were once equally unpredictable, but now people have determined the equations that govern them. When we say, "electron movements are random," we should say, "electron movements are unpredictable at our current level of understanding.
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posted
Raventhief: No. This is a fundamental misunderstanding of quantum physics. It isn't that we can't measure their positions yet, it is that their positions exist over a probability distribution until interacted with in certain ways. We can experimentally show that electrons interfere with themselves using the double slit experiment (in short: if you shoot electrons one at a time at a pair of slits and look at the distribution of impacts, you get the distribution that happens when electrons interfere with each other; if you shoot electrons one at a time at a pair of slits where you can detect "which slit" an electron goes through, each electron always goes through one slit, and the interference pattern disappears). That isn't a lack of understanding of the electron's position -- that's showing that, fundamentally, under many circumstances, the electron does not have a single position, and what's more, the simplest explanation for which slit the electron goes through is that it is a random process.
Now, it is possible that even with that result the universe is deterministic. I'm not up on the very latest, but last I heard, for the universe to be deterministic (leaving aside many-world determinism, which is technically deterministic but effectively random for an observer in any one of the dimensions) requires a large number of extra particles in the simpler theories matching available experimental evidence, several of which we would expect to have seen already if they actually existed.
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What's more, there's a theory (that is experimentally extremely well supported) that there is a fundamental resolution limit to our measurement of certain pairs of quantities. That is, the more precisely we measure one of a pair, the less precisely we are able to, for the same period of time, measure the other of the pair. This is not some limitation of available instruments that will keep going down, this is a limit that is part of nature itself (assuming our theories are at least vaguely correct -- and those particular theories accord extremely well with evidence).
In fact, it isn't that the ability to measure is limited, it is that, in the reality of the measurer, the thing being measured really is smeared across multiple values (note: this doesn't prevent there from being determinism, though it is yet another reason determinism is unsatisfactory for the simplest explanation).
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posted
I would still think that the greatest determination of time travel in the sense of "time travelers" that can move backwards in time is the fact that we have not encountered any.
If there were instances of future persons or technologies showing up then it would be a completely different story.
I do not believe this makes all time travel impossible. Merely the idea of a person traveling backwards in time. Possibly at an angle backwards, i.e. go to the middle ages but in a diffent universe where it is still the middle ages. Think that Michael Chrichton movie/book.
I loved the experiment hawking did on a program I saw a couple of months ago where he invited any future time travelers to arrive at his house for a party at a certain time and date. No one showed.
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Blayne Bradley
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posted
This isn't any real proof of anything, its just a variation of the Fermi Paradox, a supposition, not actual evidence.
It is entirely possible that time travel backwards is possible but in ways that would make casual encounters unlikely, aka using cosmic strings.
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posted
There is also a supposition that time travel in the past could be possible, but only through the time machine itself; so you could go backwards, but not to a point in time before the time machine existed. Like in Wells's 'The Time Machine'. The time machine itself traveled normally through time, like anything else. The traveler could only travel to points in time wherever the machine itself was.
Perhaps we have not been visited from the future simply because no time machine has been invented yet.
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quote:Originally posted by Blayne Bradley: This isn't any real proof of anything, its just a variation of the Fermi Paradox, a supposition, not actual evidence.
There's not even a paradox here, really. There's just an assumption that anyone visiting from the future would want to make their presence known.
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quote:Originally posted by Raventhief: One could state that men are slaves to themselves. However, the implication in that statement is that men are also their own masters. What we call choice is merely the final result of a series of logical processes, some conscious, some subconscious. What appears to be a choice, isn't.
Merely? My "series of conscious logical processes" ARE my choices. What else could there be?
Now certainly my *subconscious* processes differ, in that I don't even have the illusion of control over them: I don't have even the illusion of controlling my heartbeat, so my heartbeat is certainly not my choice.
Pretend there's somewhere a world where there exist people with "true" choice, unlike our world where supposedly people don't have true choice. What would that world look like?
If that world is exactly like ours, then you're just not assigning any meaning to the word "true choice" at all. Which exactly my point.
quote: A theoretical perfect observer with perfect knowledge could predict the outcome of every choice I make. With perfect accuracy.
So? That someone predicts my choices doesn't mean that my choices are any less mine. A master chess player who has studied me could theoretically predict my moves in chess, but that doesn't mean they wouldn't be my moves.
quote:The same, I believe, is true of everything. When we express ignorance of the outcome of anything, all we are expressing is incomplete knowledge of the inputs.
Why do you believe choice has anything to do with whether someone else can predict it? Aren't you confusing choice with randomness?
It's the truly random events that do NOT involve choice -- an electron doesn't choose its quantum state; and *that's* random and unpredictable by the laws of quantum mechanics. We on the other hand choose our actions; and that's WHY they are predictable. Because they're not random, they're choices driven by our purposes, which are driven by our psychologies, which are composed out of our biologies, are composed out of our chemistries, which are composed out of our physics.
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posted
Let me put it in another way: I can define "choice" as "Any course of action whose selection is driven by my own conscious purpose".
Let me provide some counterexamples: - My heartbeat, if need be, would be driven by my conscious purpose, as I want to live, but it's not selected by such. My conscious purpose can't make my heartbeat to stop beating by an act of will.
Therefore my heartbeat is NOT my choice.
- In thesepagesofErfworld the commander Jillian *thinks* her courses of actions are driven by her own conscious purposes; but in reality they're not, they're mostly driven by someone *else's* purpose who has cast a spell on her.
Therefore those actions are not *her* free choice, either. Her illusion of free will is her belief that her own purposes drive her actions, in reality her ensorcered actions drive her rationalizations.
So, that's NOT a free choice either.
---
But most people in reality do have free choice, because they truly can select their courses of action in accordance to their conscious purposes.
Now your turn: If you claim that free choice doesn't exist in our world, could you please describe a hypothetical universe where free choice DOES exist?
If there's no difference between the two, then to say that a universe has or doesn't have free choice contributes ZERO bits of information in the description of the world, which means it's a meaningless statement.
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quote:f there's no difference between the two, then to say that a universe has or doesn't have free choice contributes ZERO bits of information in the description of the world, which means it's a meaningless statement.
Not at all. For many people it's very important that choice be independent from predictable, physical processes. These people believe in an "agent" that can not be defined in physical terms which is responsible, at least in part, for conscious choices. This agent, being non-physical, cannot be evaluated be others and thus even perfect knowledge of external conditions cannot predict the behavior of the agent.
Should it be demonstrated that choice is a purely physical phenomenon and that there is no need for a "ghost in the machine" there would be significant repercussions for many people's philosophies. Likewise if the ghost is somehow demonstrated to exist. Assertions in favor of one position or the other are anything but meaningless.
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quote:Not at all. For many people it's very important that choice be independent from predictable, physical processes. These people believe in an "agent" that can not be defined in physical terms which is responsible, at least in part, for conscious choices.
Ah, then the question isn't about choice and free will, but rather about whether there exists a non-physical "soul" (to give it its usual label) that influences those choices.
That's a rather different question, and it *is* meaningful. But people obfuscate it if they just discuss choice by itself when they mean to discuss this other issue.
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quote:Originally posted by Sean Monahan: Perhaps we have not been visited from the future simply because no time machine has been invented yet.
If we haven't been visited yet, it means one of two things: (1) time travel never becomes possible, or (2) it does, but controls over it are such that no traveler has, thus far, revealed itself.
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posted
I'm not sure these two choices include the point I was making above. I would add: (3) it does, but possibilities are such that no traveler can come back this far.
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posted
The question is are you free to make another choice? If Bill will definitely turn left at the fork in the road, does Bill have the choice to turn right? If it is known that Bill will turn left, is it a choice when he turns left? If Bill always orders chocolate ice cream, is it because his experience, taste buds, and sense of adventure (or lack) force him to do so?
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posted
Since I'm the one writing the time travel novel in question, and my main character will eventually become a theoretical physicist precisely because he wants to understand time travel, I'm loving this. It's like my characters are doing my own research for me... Posts: 7790 | Registered: Aug 2000
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posted
Another possible time travel variant: you can go to the past, but only immaterially. Your past is fixed; you would be able to see but not touch, experience but not be seen by anyone then.
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posted
If Bill always orders chocolate ice cream, it is due to:
His recent experiences with chocolate ice cream. His past experiences associated with chocolate ice cream. His past experiences associated with other flavors. His openness to trying new things. His past experiences of trying new things. The attitudes toward trying new things exhibited by people he saw as role models or peers whose tastes he admired or respect he desired. The indicated preferences of the person he was with at the time, and how much he desired to make that person happy. The mood he was in. How recently he had had chocolate ice cream. Whether or not the food he had just eaten would be complemented by chocolate ice cream. Whether he had had chocolate ice cream from this source or not, and what that experience had been like. If anything else had happened to him recently to change his attitude toward trying new things. If the vanilla ice cream was free. If sprinkles were available.
And probably a lot more. Perfect knowledge of all this factors would allow someone to accurately predict his choice, but as I don't see that happening any time soon I don't see this having much practical value other than to remind people that we are products of our history and our previous experiences.
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posted
One other variant, you can go into the past, but every time you try to change something, you are prevented in such a way that what happens is what has always happened
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quote:Originally posted by Chris Bridges: Another possible time travel variant: you can go to the past, but only immaterially. Your past is fixed; you would be able to see but not touch, experience but not be seen by anyone then.
This reminds me of a time travel story I once read - can't remember the name, I'll try to find it - where the protaganist was in a burning building with his time machine. There is no escape. He cannot get out of this burning building and live. So he uses his time machine to go back and change the past, so the building doesn't catch on fire. (edit: I think there was also some caveat that he could only stay in the past for a certain amount of time before he's popped back into the preset.) He successfully prevents the building from catching on fire. Then he goes back to the present. He's right back where he was; in the burning building. He quickly activates his time machine again, and goes back to a different time to prevent the burning of the building in a different way. He is successful. He goes back to the present. He is back in the burning building. He keeps doing this, and eventually realizes that no matter what he does in the past, his present is immutable. Each time he pops back into the present, it takes him a couple of seconds to reactivate the time machine. It's only a matter of time before he dies in that fire.
Edit2: The story is "Ripples in the Dirac Sea" by Geoffrey A. Landis, 1988
quote:Originally posted by Chris Bridges: Another possible time travel variant: you can go to the past, but only immaterially. Your past is fixed; you would be able to see but not touch, experience but not be seen by anyone then.
Like Pastwatch.
--------------
Another time travel book that I absolutely love is Dean Koontz's Lightning.
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quote:Originally posted by Mucus: One other variant, you can go into the past, but every time you try to change something, you are prevented in such a way that what happens is what has always happened
I think that's a rather good way to explain what I am thinking, the present is a result of the past so attempting to change the past would result in the same present that already is, because that is the past to that present...
I'm just thinking of Back to the Future and how it would work out if there were no alternate deminsions... 1st. Marty would already have had a rich life, not starting with a poor one, because in the past that he has yet to put himself he had already done all of the things he is about to do.
2. He was supposed to travel to the past to do all the things he was supposed to do or else they would have never been in the 1st place.
3. if Marty would have gotten with his mom, and inevitably made himself not be concieved how would he have been able to travel back to the past to screw it up in anyways...
and I don't even want to think about the other Back to the Futures XD going by what I am saying those movies would make even less sense...
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