They didn't in the [spawn new timeline] scenario, so nothing to explain. I suppose it depends on which moment on the new timeline is consdiered to be 'the present'. If, say, the present is designated to be 'the present' in this spawned timeline, then the traveler (if there is one) must be present at 'the past', 5 years prior. Did he travel there? I suppose he did. Did he travel from 'the future'? No. He came from a different line is all. The 2024 of this timeline does not have him going back. He dies before then, presuming he doesn't exist the line by a subsequent usage of the machine.However, this does not explain how a time traveller can have travelled to the past before their first ever time travel event. — Luke
That's interpretation dependent. Empirically, the guy will remember being born, sure. Given the copy/past interpretation, yes, he was actually born in some timeline somewhere, one of many, but not this one. In the alter-history interpretation, no he was never born. That state doesn't exist in the one timeline. No earlier time had his birth in it, and only an earlier time qualifies for that verb tense.In the case of this dinosaur visitor, surely this person had to have been born before they could ever travel to the past?
You are using past-tense in a mixed way. Be specific. In the linear timeline, there are dinosaurs and a time machine that has appeared uncaused, all in the present. There are no other people on that timeline unless the guy brings a breeding population with him. Nobody was born. There is no 'must have been' about it since earlier times do not contain his birth.Therefore, there must have been an original version of the past that existed before the dinosaur visitor ever visited.
Again, on which timeline are you measuring this? Given a time machine, this would obviously not be true or a calendar timeline. Marty is in 1955, well before say 1968 when he is born, contradicting your statement.Surely, their birth must precede all the other events of their life
Only from the PoV of the machine and its contents. Per the outside observer, there is but the one jump. Yet again, you need to specify which timeline is being referenced when making statements like that.If it's a causal loop, then it will repeat the same time travel event over and over again.
Contradicting the fact that you just said it reads x+1, a number to which it was set 7 seconds ago and not altered since. That would be a contradiction, and thus cannot be the case.However, the odometer reading of "x" (jumps) is after the time travel event. Therefore, if the odometer actually works, then its reading before the time travel event must have been "x-1" (jumps).
OK, on hte Earth timeline, we're talking about dinosaurs then, just before the machine appears somewhere uncaused with an odometer reading 207. Before that Cretaceous time, no time travel event has ever occurred. History is a particular way then, but the Cretaceous is the present, so it goes only that far, and the rest is yet to be written.I am referring to pre-time travel; before the time travel event has ever occurred.
The time travel event (the appearance of the box) only has a causal effect on subsequent events, not on the prior ones that are the 'history'. The machine doesn't alter history, but it truncates it to a point and starts a new rewrite.Before anyone has ever time travelled, history will be a particular way, and this particular way (or version of history) will be altered by the time travel event to create a different version of history.
None before the Cretaceous, no. We don't know that, but we have strong reasons to believe it. Any prior time travel event would arguably have to have been made by something not human or human-created, and probably wouldn't be on Earth.We might say or believe that up until now there have been no time travel events.
The word 'now' in that sentence is ambiguous. Presumably you are still planning to go back to 1985, and thus it is still 'now' 2024, and there is still a 'we' to know such things.If I were to time travel tomorrow, back to 1985, then I would be altering history as we now know it.
You mean 1984? Yes, it contains that. If you mean 2023, then now, since it is now 1985 and 2023 has yet to be, and least per this 'rewrite' interpretation.After that, history will contain my time travel event, but it must also contain the "unaltered" history that preceded my time travel event
It is now presently 1985 and there is no 'we' there, so no, that statement makes no sense.(the history as we presently know it, before any time travel events).
Traveling to 1990 and arriving there is the same thing. That arrival event IS the time travel event. Are you talking about a different jump? Before that is 1989. 1991 is after that. The traveler has a memory of a nonexistent 1991, it being nonexistent because it's a future time, yet to actually be.you cannot already have arrived at 1990 (as a time traveller) before you have time travelled to 1990.
If you're interested in consequences, you need to address the case of multiple machines crossing each other. I thought we were deliberately ignoring the lack of possibility. If you're actually interested in it, then exploring consequences is moot until you find a way that it's actually viable. SEP seems to suggest that pacing counts, but that's hardly something with interesting consequences.To simplify matters, we might only consider one time travel event rather than several. Also, in this discussion I'm interested in the possibiilty and consequences of time travel, not in preserving the stability of the population or the timeline.
Again, it doesn't follow a time travel event, it is the event. If you're talking about the departure event, the appearance of the machine in 1990 does not follow that event. 1990 is before 2024.Obviously, a time machine will appear in the past to come "out of nowhere" following the time travel event.
The loop does not erase its construction. It isn't something that is constructed at all. It's a solid example that 'things' in that universe don't necessarily need a construction phase.That is not what I am talking about. I am talking about the history of a time machine's construction being erased in a causal loop, such as in the museum donation scenario.
It has a causal history. It's just a retro-causal history is all. As I said, you're going about finding the inconsistency all wrong. Stop trying to find the end of a loop that doesn't have one. That's not where the inconsistency is.This is the sort of appearance from "out of nowhere" that I am referring to; that a time machine or its technology comes to exist without any causal history.
He was necessarily born pre-Cretaceous? That makes no sense to me. It can make sense in the branching case, depending on how one chooses to order events that are not on the same timeline.The same applies to the dinosaur visitor who can exist in the past (which is necessarily post-time travel) prior to ever having been born (which is necessarily pre-time travel).
That is QM (or time) interpretation dependent, and no,. there is no way to falsify the interpretations that are not deterministic in one way or another.Can somebody demonstrate the typical definition of determinism?
Why? He's already got the first 'you' teaching him. How many of you does it take? You're not making a loop by doing this. You're making a crowd control situation.For example, I spend my life working out time travel technology and build a working time machine. I then time travel back to 1990 and teach my younger self how to time travel. My younger self grows up, uses the knowledge to time travel back to 1990, and teaches my/their younger self how to time travel.
Well, you just had two different people (both you) time travel to the same spot. What if the coordinates are exact and second one obliterates whatever was at the spot at which it appear? I mean, you've never really specified what happens when the machine pops into existence somewhere. What happens to the bugs and other contents of that location? If there's a person there, or half of one, or the middle of a jet engine in flight? What if you manifest a mile underground? Never mind you being somewhat stuck, but what happens to the rock that was there a moment ago?A causal loop follows the initial time travel event, but it has a different history prior to the first time travel event (an original history in which I figured out time travel without having been taught it by my time travelling self).
From the world timeline, it's a yes: first and only. I said that. From the circular timeline, there is no first.8 second guy has a first and only appearance, yes. From his looping timeline, there is no first anything. It's a circular timeline.
— noAxioms
Is that a "yes" or a "no" on the first?
I don't see how they can both be nonexistent and also 'did exist' when the time of their existence hasn't yet happened. Nothing at those times exists yet. That's the nature of 'the future'. It's what makes using the same machine to travel to future times somewhat contradictory. It would have to just go into a stasis state (Per Larry Niven's universe), wait for the prescribed time, or in the case of Niven, waiting for conditions outside to be non-fatal. The thing is, where is the machine while it's doing this? Can others see the box waiting there, or does it vanish into another realm while it waits for its destination to come into being? And of course, what happens if the departure in history suddenly ceases to be a part of history?But logically (and causally), those non-existent times did exist, prior to the time travel event.
Again, on which timeline are you measuring this? — noAxioms
They didn't in the [spawn new timeline] scenario, so nothing to explain. — noAxioms
However, this does not explain how a time traveller can have travelled to the past before their first ever time travel event.
— Luke
...I suppose it depends on which moment on the new timeline is consdiered to be 'the present'. — noAxioms
If, say, the present is designated to be 'the present' in this spawned timeline, then the traveler (if there is one) must be present at 'the past', 5 years prior. Did he travel there? I suppose he did — noAxioms
Did he travel from 'the future'? No. He came from a different line is all. — noAxioms
The 2024 of this timeline does not have him going back. — noAxioms
And as I said, the empirical experience of everybody is the same between the copy/paste interpretation and the 'alter the original' interpretation. Either way results in a general de-population of Earth from the travelers PoV — noAxioms
That's interpretation dependent. Empirically, the guy will remember being born, sure. Given the copy/past interpretation, yes, he was actually born in some timeline somewhere, one of many, but not this one. — noAxioms
In the alter-history interpretation, no he was never born. — noAxioms
That state doesn't exist in the one timeline. — noAxioms
You are using past-tense in a mixed way. Be specific. In the linear timeline, there are dinosaurs and a time machine that has appeared uncaused, all in the present. There are no other people on that timeline unless the guy brings a breeding population with him. Nobody was born. There is no 'must have been' about it since earlier times do not contain his birth. — noAxioms
Memories are thought of as 'past; things, so one could meaningfully said that he must have been born, but it's more like Adam and Eve and insisting that they must have been born which reportedly they actually had not. One wonders what their very first memories were. Did they have to learn to eat and not poop in your bed and had invent language? Our time traveler seems to have all that experience already, so he's better off. — noAxioms
Surely, their birth must precede all the other events of their life
— Luke
Again, on which timeline are you measuring this? Given a time machine, this would obviously not be true or a calendar timeline. Marty is in 1955, well before say 1968 when he is born, contradicting your statement. — noAxioms
On Marty's timeline, he is in what appears to be 1955, and has 17 years of memories, which include stories of his birth. If the memories were perfect, yea, he'd remember that birth. Whether that birth event actually exists is a matter of interpretation, just as is my birth event. Per last-Tuesdayism, there is no way I can prove that I was ever born. We all just assume it by convention. — noAxioms
Contradicting the fact that you just said it reads x+1, — noAxioms
OK, on hte Earth timeline, we're talking about dinosaurs then, just before the machine appears somewhere uncaused with an odometer reading 207. Before that Cretaceous time, no time travel event has ever occurred. History is a particular way then, but the Cretaceous is the present, so it goes only that far, and the rest is yet to be written. — noAxioms
The time travel event (the appearance of the box) only has a causal effect on subsequent events, not on the prior ones that are the 'history'. The machine doesn't alter history, but it truncates it to a point and starts a new rewrite. — noAxioms
If I were to time travel tomorrow, back to 1985, then I would be altering history as we now know it.
— Luke
The word 'now' in that sentence is ambiguous. Presumably you are still planning to go back to 1985, and thus it is still 'now' 2024, and there is still a 'we' to know such things.
If the action has just been done, then 'now' is 1985, — noAxioms
After that, history will contain my time travel event, but it must also contain the "unaltered" history that preceded my time travel event
— Luke
You mean 1984? — noAxioms
you cannot already have arrived at 1990 (as a time traveller) before you have time travelled to 1990.
— Luke
Traveling to 1990 and arriving there is the same thing. That arrival event IS the time travel event. Are you talking about a different jump? — noAxioms
Before that is 1989. 1991 is after that. — noAxioms
If you're interested in consequences, you need to address the case of multiple machines crossing each other. I thought we were deliberately ignoring the lack of possibility. If you're actually interested in it, then exploring consequences is moot until you find a way that it's actually viable. SEP seems to suggest that pacing counts, but that's hardly something with interesting consequences. — noAxioms
Again, it doesn't follow a time travel event, it is the event. — noAxioms
If you're talking about the departure event, the appearance of the machine in 1990 does not follow that event. 1990 is before 2024. — noAxioms
The loop does not erase its construction. It isn't something that is constructed at all. It's a solid example that 'things' in that universe don't necessarily need a construction phase. — noAxioms
It has a causal history. It's just a retro-causal history is all. As I said, you're going about finding the inconsistency all wrong. Stop trying to find the end of a loop that doesn't have one. That's not where the inconsistency is. — noAxioms
The same applies to the dinosaur visitor who can exist in the past (which is necessarily post-time travel) prior to ever having been born (which is necessarily pre-time travel).
— Luke
He was necessarily born pre-Cretaceous? That makes no sense to me. It can make sense in the branching case, depending on how one chooses to order events that are not on the same timeline. — noAxioms
Why? He's already got the first 'you' teaching him. How many of you does it take? You're not making a loop by doing this. You're making a crowd control situation. — noAxioms
Well, you just had two different people (both you) time travel to the same spot. What if the coordinates are exact and second one obliterates whatever was at the spot at which it appear? I mean, you've never really specified what happens when the machine pops into existence somewhere. What happens to the bugs and other contents of that location? If there's a person there, or half of one, or the middle of a jet engine in flight? What if you manifest a mile underground? Never mind you being somewhat stuck, but what happens to the rock that was there a moment ago? — noAxioms
If the 2024 that doesn't yet include the time traveler is before the 1990 that includes the time traveler, then if would seem a stretch to call what he has done 'travel to the past'. It seems to be just a re-setting of the present state (the part outside of the machine) to what things looked like back then, but no actual travel anywhere.I retain the idea that there must have been one version of history before any time travel events and a different version of history after the first time travel event (a history which henceforth includes a time traveller), at least different starting from the destination time of the time travel. — Luke
So he's in 1990 despite it presently being 2024? What's it like to be in a place that isn't the present? I think the Steven King book/movie Langoliers had a plot like that.The time traveller departs from the present and arrives in the past.
You said you were rejecting the 'spawned timeline' idea that occupied so many of our posts.The time traveller does not depart from the present of the spawned timeline, but from the present of the original timeline.
This is the truncation I mentioned, the overwrite scenario instead of spawn new line scenario. The inconsistency is calling 1990 'the past'. If the universe is currently being rewriten from there, then 1990 is the present, and there is no original history of making the machine. Those dates have yet to be written since they are in 'the future'. So now you have a machine sitting there un-built, but not un-caused. It was caused by a nonexistent retro-causal occurrence.He did travel to the past from a time which is in the relative future of that past time. He did not travel to the past from a different timeline; his time travel will change the history of the same timeline. The changes will begin from the time traveller's date of arrival, starting with the addition of the time traveller in that time.
The people there now have access to time machine technology, so that timeline is likely to be overwritten at any point. Eventually somebody will erase all of human existence and that will be that. It takes just one traveler going back a million years or so.If I were to make the first-ever time travel journey tomorrow to arrive at the destination time of 1985, why would the population suddenly decrease from my POV as a result of the time travel?
This isn't hard. His birth event doesn't exist (assuming he/somebody/something truncates the present to a date prior to the birth date. If he isn't the guy in the machine, then he doesn't exist either (at all). So not even a memory of being born.In the alter-history interpretation, no he was never born.
— noAxioms
Why was he never born?
We're in a universe with retro-causality here, one that a cause obliterates its own existence from the one history.Okay, in the linear time there are dinosaurs, and a time traveller and their time machine have appeared uncaused. Nobody was born, yet the time traveller exists. How is this consistent with causality and determinism?
That is not a logical sequence on the linear timeline. First he appears with the dinos. Then, much later, the time eventually comes that matches the year he remembers being born. There is no birth event of Bob at that time. The memory was false.The only logical sequence of events is that the time traveller is first born and then time travels to visit the dinosaurs.
Two kinds of time mixed there, unless the history line is never truncated, and the machine simply writes the current universe a new way without traveling at all. That model (I'll call it the stacking model) doesn't easily support forward time travel, but not sure if any of them do. You ought to think about how forward works. Funny, but the stacking model does allow one to witness one's own birth. Not the actual one since it doesn't involve actual travel to the past, but a copy of it. One can restore all the people eliminated by the dinosaur stint. There are no loops in the stacking model.This implies that there must exist a linear time without any time traveller up until the time traveller's birth and subsequent time travel.
So 2024 precedes year -100,000,000, a funny interpretation of the word 'precedes'.Surely, their birth must precede all the other events of their life
Ah, you actually identify a line. Sure, on that line, 2024 precedes -100M. But it's just a memory. His birth event (say in 1975) is nonexistent. He can't for instance take the machine back to it and witness it.In this context, I'm measuring it on the traveller's timeline
Not if your earliest appearance was from a time machine. You keep thinking the rules of this universe apply to this retro-causal one.Being alive is pretty good evidence of having been born.
From the PoV of the machine, sure, That's the same as memory. 2024 feels like 'the recent past' to the machine and its contents. If we're talking about the stacking model, it actually still is the past, and sure, the machine was in fact built at some point. That model is empirically different than the other ones we've been discussing.The arrival of the time machine in 1990 does not follow its departure from 2024? But isn't that exactly what a time machine does?
Take 8 second-man, but make it 50 years. A young guy steps out the machine, and the same guy 50 years older travels back to the arrival event, and not looking like some old guy. That's an odometer, and I cannot explain it better when you seem incapable of understanding why the jump counter in a loop would be a contradiction.Okay, then where is the inconsistency?
We were deliberately ignoring all that, since the possibility of this as described isn't there at all.The "If" part needs backing proofs with evidence before the whole sentence could be accepted as a meaningful statement. — Corvus
Here you seem to be using the word 'timeline' to mean something like 'period of time'. That's not how it is being used in our posts. One timeline with Hitler losing WWII. One with him winning. Others with no Hitler. Other timelines with no humans at all, ever.The word "timeline" is, of course, vital in the study of history. Over an era there is a timeline of wars, a timeline of governance, illnesses, etc. — jgill
Here I think perhaps you're confusing the word with 'worldline', a term for a physical path of an object through spacetime, that sometimes comes up in discussion of relativity and block universes, although the term is not directly related to time dilation, which is just an abstract coordinate effect.Is there any evidence of the existence of timelines in the physical world beyond time dilation?
Sure. The point is not a criticism or condemnation by any means. It is just to clarify the statement is unsupported in any meaningful manner without proofs and evidences, hence all the following arguments would be just speculative conjectures.The "If" part needs backing proofs with evidence before the whole sentence could be accepted as a meaningful statement.
— Corvus
We were deliberately ignoring all that, since the possibility of this as described isn't there at all. — noAxioms
Come to think of it, what prevents you from trying to prove the assumption? Wouldn't it be actually an interesting attempt, and all the emanating arguments from the proofs (if it were possible to come to some sort of proofs with evidences) would be more exciting? :DThe "If" part needs backing proofs with evidence before the whole sentence could be accepted as a meaningful statement.
— Corvus
We were deliberately ignoring all that, since the possibility of this as described isn't there at all. — noAxioms
The word "timeline" is, of course, vital in the study of history. Over an era there is a timeline of wars, a timeline of governance, illnesses, etc. But the word used in this thread is a many-worlds fabrication— jgill
"Here you seem to be using the word 'timeline' to mean something like 'period of time'. That's not how it is being used in our posts. One timeline with Hitler losing WWII. One with him winning. Others with no Hitler. Other timelines with no humans at all, ever."
"Is there any evidence of the existence of timelines in the physical world beyond time dilation?"
Here I think perhaps you're confusing the word with 'worldline', a term for a physical path of an object through spacetime, that sometimes comes up in discussion of relativity and block universes, although the term is not directly related to time dilation, which is just an abstract coordinate effect. — noAxioms
If the 2024 that doesn't yet include the time traveler is before the 1990 that includes the time traveler, then if would seem a stretch to call what he has done 'travel to the past'. It seems to be just a re-setting of the present state (the part outside of the machine) to what things looked like back then, but no actual travel anywhere. — noAxioms
The time traveller departs from the present and arrives in the past.
— Luke
So he's in 1990 despite it presently being 2024? What's it like to be in a place that isn't the present? I think the Steven King book/movie Langoliers had a plot like that. — noAxioms
The time traveller does not depart from the present of the spawned timeline, but from the present of the original timeline.
— Luke
You said you were rejecting the 'spawned timeline' idea that occupied so many of our posts. — noAxioms
I retain the idea that there must have been one version of history before any time travel events and a different version of history after the first time travel event (a history which henceforth includes a time traveller), at least different starting from the destination time of the time travel. — Luke
Keep in mind that I'm not a presentist, and am sort of having fun seeing how a presentist can phrase time travel coherently. — noAxioms
The inconsistency is calling 1990 'the past'. If the universe is currently being rewriten from there, then 1990 is the present, and there is no original history of making the machine. — noAxioms
then 1990 is the present, and there is no original history of making the machine. Those dates have yet to be written since they are in 'the future'. So now you have a machine sitting there un-built, but not un-caused. It was caused by a nonexistent retro-causal occurrence. — noAxioms
Point is, every use of the machine(s) in the backwards direction truncates history a little further. The population would empirically slowly dwindle in the branch timelines, but here you have no branches, only the original, and in that line, the present keeps moving backwards at frequent intervals. — noAxioms
Why was he never born?
— Luke
This isn't hard. His birth event doesn't exist (assuming he/somebody/something truncates the present to a date prior to the birth date. If he isn't the guy in the machine, then he doesn't exist either (at all). So not even a memory of being born. — noAxioms
We're in a universe with retro-causality here, one that a cause obliterates its own existence from the one history. — noAxioms
The only logical sequence of events is that the time traveller is first born and then time travels to visit the dinosaurs.
— Luke
That is not a logical sequence on the linear timeline. First he appears with the dinos. Then, much later, the time eventually comes that matches the year he remembers being born. There is no birth event of Bob at that time. The memory was false. — noAxioms
This implies that there must exist a linear time without any time traveller up until the time traveller's birth and subsequent time travel.
— Luke
Two kinds of time mixed there, unless the history line is never truncated, and the machine simply writes the current universe a new way without traveling at all. That model (I'll call it the stacking model)... — noAxioms
Surely, their birth must precede all the other events of their life
— Luke
So 2024 precedes year -100,000,000, a funny interpretation of the word 'precedes'. — noAxioms
In this context, I'm measuring it on the traveller's timeline
— Luke
Ah, you actually identify a line. — noAxioms
Sure, on that line, 2024 precedes -100M. But it's just a memory. His birth event (say in 1975) is nonexistent. He can't for instance take the machine back to it and witness it. — noAxioms
Being alive is pretty good evidence of having been born.
— Luke
Not if your earliest appearance was from a time machine. You keep thinking the rules of this universe apply to this retro-causal one. — noAxioms
If you're talking about the departure event, the appearance of the machine in 1990 does not follow that event. 1990 is before 2024
— noAxioms
The arrival of the time machine in 1990 does not follow its departure from 2024? But isn't that exactly what a time machine does?
— Luke
From the PoV of the machine, sure, That's the same as memory. 2024 feels like 'the recent past' to the machine and its contents. — noAxioms
you seem incapable of understanding why the jump counter in a loop would be a contradiction. — noAxioms
There is evidence one way or the other. There is rarely 'proof' of anything. In this case, there are valid non-local interpretations of physics with superluminal cause/effect. That opens the door for retrocausality. But none of the interpretations allow superluminal information transfer. That pretty much closes the door.It is just to clarify the statement is unsupported in any meaningful manner without proofs and evidences. — Corvus
I suppose in the end it would matter how it works, before we go about presuming the properties and possible interpretations of the thing.Because of the fact the premise "IF" describes the possible physical and empirical events, and also the conclusion part is soley dependent on the premise, it should have given even brief explanations how the IF part could be possible, for it to be accepted as a valid assumption for the further arguments.
Again, I thought you were abandoning the interpretation with creation of timelines in favor of modifying the one and only line.The time traveller departs from the timeline without time travel and creates a timeline with time travel by doing so. — Luke
Seemingly an admission that time travel with presentism don't particularly mix. I mean it does. SEP discusses it, but says very much that the arrival event occurs decades before the departure event, back when the arrival event was the present, which only happens once. That model doesn't have a history between those times where time travel hasn't yet happened.If it will help make things clearer, I can try to dispense with (McTaggart's) A-series terms. The time traveller departs from the year 2024 and arrives in the year 1990.
You use a lot of A-series terms, which make no sense without presentism. Yes, learn to dispense with the concept. It helps. There's no evidence for it other than intuition, a pragmatic lie that makes us fit.Keep in mind that I'm not a presentist, either.
Maybe. I mean, it;s not possible, so you'd probably get a hard contradiction with eternalism as well. Doing so given an impossible premise wouldn't falsify either view.As I said earlier in the discussion and as I have explained previously on these forums, I believe that a combination of both views of presentism and eternalism are required to coherently account for time.
I don't mean disassembled. I mean something exists which never came into being. But this is in the truncate-model, which I'm rejecting because we could never have existed in such a universe.Why would the time machine be un-built in 1990?
I noticed.You may find it perfectly logical for a person to exist before they are born, but I do not.
But that's just a memory. It is a memory of nonexistent events.I was referring to the sequence of events of a person's life.
Yes. A machine appeared in the Cretaceous and humans evolve only on the timeline without the machine.Why not? Did he somehow prevent it from happening?
'Change of movement through time'. What an interesting way of putting it. You'd like the SEP definition of time travel then, which is whenever clocks don't agree for reasons other than a faulty clock.I admit, I am stretching a point. I'm looking for any sort of evidence of change of movement through time. — jgill
'Change of movement through time'. What an interesting way of putting it. — noAxioms
The time traveller departs from the timeline without time travel and creates a timeline with time travel by doing so. — Luke
Again, I thought you were abandoning the interpretation with creation of timelines in favor of modifying the one and only line. — noAxioms
Back to the train tracks, Alice gets there just as the gates go down, but watches a very similar car ahead of here make it across. So she hits the button and goes back 30 seconds. That destroys the 30 seconds. She ends up at the tracks, and in time to scoot across. The world ends 30 seconds later when the car behind here truncates it there. There is no future after that. The universe cannot go on. — noAxioms
If it will help make things clearer, I can try to dispense with (McTaggart's) A-series terms. The time traveller departs from the year 2024 and arrives in the year 1990.
Seemingly an admission that time travel with presentism don't particularly mix. — noAxioms
SEP discusses it, but says very much that the arrival event occurs decades before the departure event, back when the arrival event was the present, which only happens once. That model doesn't have a history between those times where time travel hasn't yet happened. — noAxioms
There's no obvious correct way to compare moments between timelines. — noAxioms
Why would the time machine be un-built in 1990?
I don't mean disassembled. I mean something exists which never came into being. But this is in the truncate-model, which I'm rejecting because we could never have existed in such a universe.
I know you consider the machine to have been built, despite that process not existing, and 'was built' (a past tense reference) 30 years from now. As Dr Who said in his Xmas party: Didn't you get me this next year? — noAxioms
You may find it perfectly logical for a person to exist before they are born, but I do not.
I noticed. — noAxioms
But that's just a memory. It is a memory of nonexistent events.
His birth event (say in 1975) is nonexistent. He can't for instance take the machine back to it and witness it. — noAxioms
Yes. A machine appeared in the Cretaceous and humans evolve only on the timeline without the machine. — noAxioms
Tachyon is a hypothetical object which is in the domain of a fiction.Physics mathematically allows for tachyons, which can 'go backwards' in time, but nobody has ever found a tachyon or other necessary exotic matter such as things with negative mass and such. — noAxioms
In Modal Logic, when you say X is possible, it implies that X was possible in real sense. For example,I suppose in the end it would matter how it works, before we go about presuming the properties and possible interpretations of the thing. — noAxioms
It is a hypothetical object in the domain of science. Can't help it if the fiction folks are the ones that latched onto it.Tachyon is a hypothetical object which is in the domain of a fiction. — Corvus
Closed time loops are valid solutions to Einstein's field equations. They would probably involve exotic matter, and would already be there, forming small close time loops. Classically (unrealistic), this is equivalent to a 'rift in space & time' (definitely a fiction term), sort of like in the Kate & Leopold movie. There's no machine, no punching in a desired destination. You just compute where and when they are and leverage them.But if X = I can walk on the planet Jupiter, or I can fly faster than light. then it would be rejected by most people unless there were some explanations on how that would be possible, because there is no logical ground or scientific possibilities for that statement to make sense on their own out of blue. Therefore it is not fit for being a premise for any intelligible discussions. — Corvus
Your new suggestion says that the original (and only) timeline is truncated back to the destination event upon somebody time traveling backwards. If it subsequently (30 seconds later) is truncated again, by 30 seconds, then there is no way for the history of the timeline to grow beyond any backwards travel departure. The only way for it to go forward significantly is if there is never again a backwards time travel event. I don't know about forward time travel You've given seemingly no thought as to how that might work.Could you explain further why the universe cannot go on? I don't follow. — Luke
This is a different kind of loop since it doesn't involve the same machine traveling over and over. It only makes but the one trip. That's enough to end the universe, according to the 'rewind/truncate' thing you've been pushing lately.This is a causal loop, I take it? You said that a causal loop only appears to occur once for any outside observer.
I didn't say destroyed. I say it ends. Your idea posits that: If I go back to 1990, everything from there to 1990 ceases to be part of the universe. Is not the entire universe affected by this, or do we just rewind some limited region like Disneyland? So now everyone in Disney thinks it's 1990 (they're pretty good at that sort of thing), but people outside the park think it's still 2024. That's not time travel, it's just fooling the guy in the machine by putting him in a live action role playing game.How is the rest of the universe destroyed or affected?
You can, but it would be really nice if the discussion was free of more contradictions than just the impossibility of time travel (besides the pacing).Does that mean we can't think about it, then?
There is but the one timeline, unless we're changing stories again.Is it so difficult to distinguish a timeline which contains a time traveller from one which does not?
It's your model, the one you are not pushing instead of the branching model. You didn't really give it a name, so I did. In it, travel to 1990 deletes 34 years of history and lets it all get rewritten again, but with a different 1990 state this go around. That 34 year scenario might well not end the universe, if the second go around can not only destroy that machine, but preventing anything anywhere (including other galaxies) from ever making one. This cannot occur in the 30-second story with the train tracks. No way to stop that one, so the universe ends there.Also, I don't know what you mean by the "truncate model".
In the context you didn't include, it was because he travels to a time before his birth, thus altering 'history' to one in which he (or any other human for that matter) is never born.Why couldn't he use the time machine to witness his own birth?
They only evolve from a Cretaceous state that doesn't include a time machine, yes. More precisely, humans don't evolve from a Cretaceous state that is in any way different than the Cretaceous state from which we evolved. That's popularized by the term 'butterfly effect'. Chaos theory is very clear on points like this.Are you saying that humans did only evolve on a timeline without a time machine
And what definition are you using this time? What is this sort of timeline, and how does one go about initiating one?I like "timelines", but only those I initiate. — jgill
Your new suggestion says that the original (and only) timeline is truncated back to the destination event upon somebody time traveling backwards. If it subsequently (30 seconds later) is truncated again, by 30 seconds, then there is no way for the history of the timeline to grow beyond any backwards travel departure. The only way for it to go forward significantly is if there is never again a backwards time travel event. I don't know about forward time travel You've given seemingly no thought as to how that might work. — noAxioms
That's enough to end the universe, according to the 'rewind/truncate' thing you've been pushing lately. — noAxioms
I didn't say destroyed. I say it ends. Your idea posits that: If I go back to 1990, everything from there to 1990 ceases to be part of the universe. Is not the entire universe affected by this, or do we just rewind some limited region like Disneyland? — noAxioms
There is but the one timeline, unless we're changing stories again. — noAxioms
You didn't really give it a name, so I did. In it, travel to 1990 deletes 34 years of history and lets it all get rewritten again, but with a different 1990 state this go around. That 34 year scenario might well not end the universe, if the second go around can not only destroy that machine, but preventing anything anywhere (including other galaxies) from ever making one. This cannot occur in the 30-second story with the train tracks. No way to stop that one, so the universe ends there. — noAxioms
In the context you didn't include, it was because he travels to a time before his birth, thus altering 'history' to one in which he (or any other human for that matter) is never born. — noAxioms
That's popularized by the term 'butterfly effect'. Chaos theory is very clear on points like this. — noAxioms
They have quantum teleporters, which means they actually have teleported a small object from here to there — noAxioms
I like "timelines", but only those I initiate. — jgill
What is this sort of timeline, and how does one go about initiating one? — noAxioms
What is exactly the 'exact matter' including various virtual particles?Tachyon is a hypothetical object which is in the domain of a fiction.
— Corvus
It is a hypothetical object in the domain of science. Can't help it if the fiction folks are the ones that latched onto it.
The particle is lumped onto various headings of 'exotic matter' (including various virtual particles), and exotic matter is seemingly a hard requirement for time travel. — noAxioms
So does it not prove that the whole story is just a fiction itself?None of this rewinds reality, but actual retro-causal (or FTL) information transfer opens things up to paradoxes. — noAxioms
Yet another thread about time. I was thinking yesterday of a very vague idea that I'd like opinions on. So then if we took a "snapshot" of this very moment with it's totality, that being: The position of every single object, cell and et cetera. And had the ability to manipulate matter in such a way that we can reposition new "environmental" circumstances into the ones that we have snapshotted, would that not be considered time travel? If anybody ever has watched "Watchmen" and know of Dr.manhattan I ask this question as regarding his fictional abilities. Those being the ability to manipulate a surrounding environment to a total extent, whatever that may be. — unintelligiblekai
They have quantum teleporters, which means they actually have teleported a small object from here to there. — noAxioms
I didn't mention 'exact matter'. Perhaps you misread 'exotic'. One can simply google 'exotic matter' for a more specific list.What is exactly the 'exact matter' including various virtual particles? — Corvus
Not really. CTCs are allowed, and might actually exist at quantum scales. Their existence is not inherrently contradictory. To open one at a classical scale probably leads to necessary contradictions, and since all the time travel stories are classical, I'd have to actually answer that such stories are necessarily fiction.So does it not prove that the whole story is just a fiction itself?
One can scan a person down to the biochemical level: the location of every cell and connection, the chemical makeup of all fluids everywhere. That's still a classical measurement. It's trying to scan down to the atomic level where things get impossible.And had the ability to manipulate matter in such a way that we can reposition new "environmental" circumstances into the ones that we have snapshotted, would that not be considered time travel? — unintelligiblekai
I cannot parse this. How does something follow something that is fictitious?Shouldn't how one could change the past events follow after fictitious successful time travel has been achieved, rather than before the travel? Have you achieved fictitious time travel into the past or future in actuality? — Corvus
Good question. Yes and no. Yes, the state of the source side was somehow reduced to what might be construed as information (something one might shove through a wormhole??), but not information that could be monitored or saved in any way. The ability to do that would violate Heisenberg's uncertainty. But whatever was 'transmitted' to the destination 'booth' (I don't know the actual words they use), it reproduced the state of the source exactly, which necessarily does not leave the source behind. It is entirely quantum, not a classical copy. If the particle was entangled with some other particle, it still is after the teleport. That would not be true of a copy.Isn't quantum teleportation essentially just the transfer of information though? — Pantagruel
I think you used the word 'rewind'. It seemed to work like a VCR tape recording all of history everywere. Anytime somebody travels back, you rewind the tape to 1985, and start recording from there. If that's how it works, then the tape will never reach year 3000 because somebody (not always the same person) keeps rewinding it.I've never said that the timeline is "truncated". By "truncated", do you mean "shortened"? — Luke
I didn't say otherwise. The VCR tape resumes recording at 1985 and progresses no problem.Let's say the time traveller travels from 2024 to 1985. The time travel event will change the history of the timeline from 1985 onwards, compared to the history of the timeline as it was before the time travel event took place in 2024. But I don't see why any time after 1985 should not exist, post-time travel.
Well, from about 1986 on, the people born will be different ones. That's a very chaotic function.Unless the time traveller does something catastrophic, then I would imagine that many of the same people will be born
If this new timeline also has a time travel event in 2024, then the rewind happens again. If there is no time travel event there, then no rewind takes place then. That's why I came up with the 30 second train-track example, where the subsequent time travel decision is very likely. Over 40 years, it is very unlikely that events will turn out identically, especially if Bob goes back to 1985 explicitly to prevent the creation of the time machine.On that note, do you agree that the time travel event does not occur until 2024, given that the time traveller departs from 2024 to arrive in 1985?
What does rewind do to the 40 years over which we backtrack? It either erases as it goes or that part of history gets overwritten as the recording resumes. Either way it is not part of the universe. That's the problem of using the same tape to record something new: you lose what was on there before.Where did I say that "everything from there to 1990 ceases to be part of the universe"?
I didn't say that.Why does the first time travel event allow history to "all get rewritten again" but the second time travel event does not?
Who gets born is very much a function of exactly when people have sex, and which sperm wins. Which species come about is very much a function of random mutations and environmental chance. All these things are altered by chaotic things in the environment.How does the butterfly effect of the time travel event necessarily prevent the evolution of humanity?
Yes, it must have been my mistyping. I try not to google too much if I can help it. The underlying implication for asking the question was not just the meaning of the concept, but also your explanation on how it works with time travel.I didn't mention 'exact matter'. Perhaps you misread 'exotic'. One can simply google 'exotic matter' for a more specific list. — noAxioms
Not saying they are not allowed, but trying to focus more on the possibility of the travel before what one can do in the past or future when arrived there.So does it not prove that the whole story is just a fiction itself?
Not really. CTCs are allowed, and might actually exist at quantum scales. Their existence is not inherrently contradictory. To open one at a classical scale probably leads to necessary contradictions, and since all the time travel stories are classical, I'd have to actually answer that such stories are necessarily fiction. — noAxioms
But there are loads of the other aspects that you must think of such as the mental contents = memories, thoughts and the consciousness of the past, such as if you travelled to 1761, would you still contain the present mind, or would the content of your mind be wiped out, and replaced by the 1761 mind, or would it become total blank due to the travel?One can scan a person down to the biochemical level: the location of every cell and connection, the chemical makeup of all fluids everywhere. That's still a classical measurement. It's trying to scan down to the atomic level where things get impossible. — noAxioms
Fictitiously.Shouldn't how one could change the past events follow after fictitious successful time travel has been achieved, rather than before the travel? Have you achieved fictitious time travel into the past or future in actuality?
— Corvus
I cannot parse this. How does something follow something that is fictitious? — noAxioms
The particle is lumped onto various headings of 'exotic matter' (including various virtual particles), and exotic matter is seemingly a hard requirement for time travel. — noAxioms
Yep, got the description for "exotic matter", but you still need to explain why and how exotic matter is required for time travel. How does it supposed to work?I didn't mention 'exact matter'. Perhaps you misread 'exotic'. One can simply google 'exotic matter' for a more specific list. — noAxioms
Read up on chaos theory. I can't possibly explain it to you in this context. — noAxioms
Why would any of that occur? I mean, sure, if one was to travel to 1990, they'd find me there, but without 2024 memories, but why would the teleporter leave you in a different state when it by definition doesn't?But there are loads of the other aspects that you must think of such as the mental contents = memories, thoughts and the consciousness of the past, such as if you travelled to 1761, would you still contain the present mind, or would the content of your mind be wiped out, and replaced by the 1761 mind, or would it become total blank due to the travel? — Corvus
Well, the usual physical explanations disallow the concept of 'change the past'. That means much of our discussion is moot. The machine (presuming unrealistically that the requirement is a vehicle of sorts) comes first, then the development of it. More realistic is the idea that the connection is established at both ends and there's no surprise when something appears uncaused 'from nowhere' so to speak.Not saying time travel is total baloney, but I am interested in how it might be possible, as well as what you could do in the past or future when you arrived there. — Corvus
Ask those who have worked out valid solutions to Einstein's field equations. Apparently it cannot be done without utilizing negative energy and such. The Alcubierre drive (NASA reportedly working on it) requires it as well, at it very much would constitute time travel if it worked. All these require bending spacetime in a manner that isn't possible with ordinary positive energy. Neither of us knows the mathematics of it well enough to understand their explanations.but you still need to explain why and how exotic matter is required for time travel. How does it supposed to work? — Corvus
The simplest models exhibiting chaotic behavior may be simple, but real functions are anything but. The weather for instance is not a simple iteration of a single complex function, and yet it is very chaotic, and all that we've discussed (who gets conceived/born, which creatures evolve) is very much a function of the weather, among countless other factors, most notably wave function collapse.The theory assumes a dynamical system, which means a simple iteration of a single complex function. — jgill
The simplest models exhibiting chaotic behavior may be simple, but real functions are anything but — noAxioms
and all that we've discussed (who gets conceived/born, which creatures evolve) is very much a function of the weather, among countless other factors, most notably wave function collapse. — noAxioms
Get involved in philosophical discussions about knowledge, truth, language, consciousness, science, politics, religion, logic and mathematics, art, history, and lots more. No ads, no clutter, and very little agreement — just fascinating conversations.