I think you used the word 'rewind'. — noAxioms
If that's how it works, then the tape will never reach year 3000 because somebody (not always the same person) keeps rewinding it. — noAxioms
Anyway, if I got things wrong, you need to correct me on how the model actually works because I don't see how the tape can make forward progress if anybody anywhere has the power to rewind it arbitrarily far at any moment. — noAxioms
As for Back to the Future, that movie has holes. It isn't self consistent. — noAxioms
The VCR tape resumes recording at 1985 and progresses no problem. — noAxioms
Unless the time traveller does something catastrophic, then I would imagine that many of the same people will be born
Well, from about 1986 on, the people born will be different ones. That's a very chaotic function. — noAxioms
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?
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. — noAxioms
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. — noAxioms
How does the butterfly effect of the time travel event necessarily prevent the evolution of humanity?
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.
Read up on chaos theory. I can't possibly explain it to you in this context. There is no strange attractor for a specific person being born, or for a specific species to evolve. There would probably be mammals around since those existed in the Cretaceous, but probably no mammal that you'd recognize. — noAxioms
If time is some physical entity running itself somewhere in the universe, and if there were different timelines running in different physical spaces, then perhaps you could get into the space via the teleport or whatever bending spacetime and what have you, maybe then you could say your mind and body of 2024 can travel to whatever year you choose without losing the memory, thoughts or consciousness.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? — noAxioms
The word you used was 'overwrite'. I've been trying to explore the implications of various models, but perhaps I have it wrong. To quote:You used the word "rewind". I followed your usage to point out that time travel does involve a sort of rewinding of time. — Luke
On reflection, I want to reject my suggestion that there is more than one timeline. You've helped me to see that this is not really what I had in mind. What I have in mind is that there is only a single timeline but that the effects of the first time travel event overwrite the past of the original timeline (starting from the destination time of the time travel event, e.g. 1990). This might create a causal loop or it might not. However, the main idea I've been trying to convey all along is that there must be an original version of "the past" prior to the first ever time travel event, which gets overwritten and is necessarily different to the version of "the past" that exists post-time travel. This helps to retain "normal" causality, thus removing the need for the magical appearance of time machines or technology "out of nowhere", existing uncaused (as in a causal loop) and thus removes the impossibility of killing one's own grandfather (as in the grandfather paradox). It also removes the unpopular idea that time travel creates a "copy" of the original timeline. And it retains free will. — Luke
So you want to limit the discussion by imposing a single travel event restriction. This would prevent us from exploring the plausibility of the model. Apparently avoiding that exploration is something you want.;Not if we only discuss one time travel event, like I keep asking.
A description that works only in one case isn't a model.If we can stick to only one time travel event, then the model works like this
You seem only to describe the traveler, not what it's like to be left behind, to be 'overwritten'. Back to the Future (BttF) never shows what it's like for his loser parents to be overwritten by the confident parents. These are the parts missing from your model.1985 progresses without the appearance of any time traveller, until 2024 when someone first time travels and they arrive back in 1985. Everything about 1985 (the second time around) is almost the same as it was without the time traveller (the first time around), except that now it has a time traveller in it. In this way, it is very much like Back to the Future.
For a brief time, maybe. BttF seems to adopt an unrealistic fatalistic approach without chaos theory. It's entertainment and isn't supposed to be consistent with physics.It is probable that most of the changes will be localised around the time traveller's location.
You can hold this belief all you want, but the mathematics says otherwise. Things turning out the same way assumes a very hard variant of determinism, even without the appearance of something that can't be there.I don't believe that it would be very chaotic, or that many of the people born would be different ones
On the vertical time axis, yes, as described above. But that sort of runs into problems when there is more than one travel event, an avenue you seem reluctant to face.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?
I don't know your model clearly. I can't discuss this.Besides, I thought your example was supposed to end the timeline somehow, but I still don't follow how it does.
Evolution of specifically humans was less likely that a 1 in a gazillion chance. Countless uncaused random events needed to happen just so. So the odds of rolling the same gazillion sided die and getting the same number is effectively nil.How does the butterfly effect of the time travel event necessarily prevent the evolution of humanity?
Yep, and we're changing the environment, and also letting all the random events have a 2nd try, and they'd all have to come out the same..Which species come about is very much a function of random mutations and environmental chance.
Not really clear what might be meant by that...If time is some physical entity running itself somewhere in the universe — Corvus
That sounds like a multiverse of sorts, levels I-III if that means anything to you. But the whole point of them being a multiverse is that the states in the various physical spaces don't interact. If they do, it's one universe, not multiple.and if there were different timelines running in different physical spaces
OK, you seem to separate mind from the physical state, so it's on you to figure out how the two might keep track of each other.maybe then you could say your mind and body of 2024 can travel to whatever year you choose without losing the memory, thoughts or consciousness.
We seem to have gone off on a supernatural tangent. Not my problem.Under the law that even God cannot intervene, your mind will be that of the people who lived in the world of whatever year you travel to, and you body as well. Perhaps your body will need a few deaths, resurrections and new births to reach the time you are supposed to travel to if it is a few hundred years away from the present moment.
Um, yes. I'm talking about the complicated functions of reality as opposed to the simple functions often used to demonstrate chaotic behavior in textbooks.I assume you are not talking about "real functions" as compared with "complex functions", but what we find in nature. — jgill
Quantum randomness is a critical part of especially mutations. Given a different starting state (or even the same starting 'state' but without hard determinism), a completely different outcome will collapse out of the wave function of all possible futures of that initial state.How did wave functions sneak in?
It is just one of the different scenarios of what the nature of time might be.Not really clear what might be meant by that... — noAxioms
That wasn't anything to do with a supernatural tangent. It was just an expression to emphasise that you cannot reverse time, and no one in the whole universe can. No one said that was your problem.We seem to have gone off on a supernatural tangent. Not my problem. — noAxioms
You have been for sure. OK, please carry on. I am bowing out here.And BTW, 'object' is very much just an ideal. There seem to be anything physical about what constitutes an object.
I'm getting pretty far off topic here. — noAxioms
So you seem to envision two dimensions of time. — noAxioms
One is Earth coordinate time, as measured with numbers like 1990, moving horizontal to larger numbers, and the other is perpendicular, and moves 'up' with each travel event. — noAxioms
You seem to assert a single physical space that is 'overwritten', which is a lot like a VCR tape, except there are perhaps no spools to rewind since you seem to balk at that word. — noAxioms
So there is the tape which holds the entire history of the universe up to a 'present' where the write-head is writing. It writes up to 2024 say and then Bob goes back to 1990. A write head goes back to 1990 (without erasing, which would be truncation, another word you don't like) and starts overwriting there. — noAxioms
It is unclear if this is a second write head (leaving the 2024 one to continue writing a universe without Bob, or if the history stops there and waits for the write head 34 years prior to catch up. — noAxioms
With this model, Bob goes back, and the history of the creation of the time machine in 2023 still exists, but the writing is going on in the 90's and when it finally gets to 2023, it overwrites the creation of the time machine, leaving a time machine without a creation event in any of history. — noAxioms
So you want to limit the discussion by imposing a single travel event restriction. This would prevent us from exploring the plausibility of the model. Apparently avoiding that exploration is something you want. — noAxioms
This is just a repeat of what was said before, without answering any of the questions. It's always described only from the PoV of Bob.The time traveller originally passes through 1990 without any time travel events (as a child, say). They subsequently grow up and build a time machine. Subsequent to this, in 2024, they travel back to 1990 (as an adult time traveller). There is no time traveller (who has time travelled) in 1990 until after the 2024 time travel event. 1990 is only "overwritten" (post-time travel) in the sense that it now contains a time traveller, whereas it did not contain one before the 2024 time travel event. It is also "overwritten" in the sense of whatever effects the time traveller has on the timeline from 1990 onwards post-time travel that they did not have on the timeline from 1990 to 2024 pre-time travel. — Luke
You balked at that before. So no overwrite, but just truncation, and a new building onto 1990, not overwriting some alternate future that no longer will happen. Robert is immediately gone, and never was, and never will be, in the world timeline which is presently at 1990. The time machine now exists without having been created since its creation has been truncated off. It doesn't exist and never will. You seem to not like that, but that part doesn't bother me. Sure, its creation exists on Bob's line, but most of Bob's line is not part of the universe, but just a memory.I have no issue with the word 'truncated'.
The train track scenario illustrated that, but it depends on your answers. The truncation interpretation does result in that, yes. Time cannot move forward. The machine has God-like powers and can actually take control of where the present is and put it somewhere else. Any alien with this technology can effortlessly wipe out human existence simply by truncating us off of history.You claimed that the timeline could be permanently truncated. I still don't follow how or why that could be.
Eternalism suggests no such thing. There is nothing that 'progresses' at all.I'm not suggesting that 1990 and 2024 are both progressing simultaneously. After all, I'm not an Eternalist.
OK, the train track thing is a single event (sort of), and I don't see how the universe can ever get to tomorrow with it.I'm asking that we get clear about a single time travel event first.
This is just a repeat of what was said before, without answering any of the questions. — noAxioms
Bob is born 1985, meets Sue in 2002, married in 2007, and has a daughter Roberta, born in 2010. Bob kills young-Bob in 1990, so what is the experience of Roberta when she gets overwritten? — noAxioms
What is the experience of Sue when she still exists, but has her marriage and all her history overwritten? — noAxioms
Apparently nobody can witness the departure event of the time machine, at least not if it goes backwards. — noAxioms
You've given no clue how it can go forward to some piece of history that has yet to be written. — noAxioms
I have no issue with the word 'truncated'.
— Luke
You balked at that before. — noAxioms
So no overwrite, but just truncation, and a new building onto 1990, not overwriting some alternate future that no longer will happen. — noAxioms
Robert is immediately gone, and never was, and never will be, in the world timeline which is presently at 1990. — noAxioms
The time machine now exists without having been created since its creation has been truncated off. It doesn't exist and never will. — noAxioms
Sure, its creation exists on Bob's line, but most of Bob's line is not part of the universe, but just a memory. — noAxioms
You claimed that the timeline could be permanently truncated. I still don't follow how or why that could be.
— Luke
The train track scenario illustrated that, but it depends on your answers. The truncation interpretation does result in that, yes. Time cannot move forward. The machine has God-like powers and can actually take control of where the present is and put it somewhere else. Any alien with this technology can effortlessly wipe out human existence simply by truncating us off of history. — noAxioms
I'm not suggesting that 1990 and 2024 are both progressing simultaneously. After all, I'm not an Eternalist.
Eternalism suggests no such thing. There is nothing that 'progresses' at all. — noAxioms
...so either there is an explosion and the Alices all die (yay for the universe), or one wins and truncates the other out of existence, and the cycle continues. — noAxioms
I have to admit that there is a solution to the problem that I didn't see before. — noAxioms
Roberta won't have any experience if she is overwritten, because she will cease to exist. — Luke
noAxioms]Apparently nobody can witness the departure event of the time machine, at least not if it goes backwards —
This seems contradictory.Someone could see it disappear, I suppose — Luke
Overwrite means the time between 1990 and 2024 still existrs, but gets changed as time makes its way across that period. Truncation means it is gone, and the new write is added to the end of existing history, which is at 1990. The two are the same after 2024 is reached again, or until there is another travel event.I said that the timeline gets overwritten, but you've somehow interpreted that (to be the opposite of what I said) as "no overwrite, but just truncation".
You have a funny definition of 'did happen'. Those are future events, and if it's 1990, they're not in the past and thus the use of past tense is misleading.You are correct that the pre-time travel period of 1990-2024 "no longer will happen", but only because it already did happen.
I grant that. It has universe-ending consequences, but the grandfather thing isn't itself paradoxical in this view. Presentism does buy you that. The paradox has more teeth when you take presentism away.My argument is that time travel and the act of time travelling to kill one's own grandfather (or their younger self) is hypothetically possible and logically consistent.
Things don't 'remain' or 'go in or out of' existence under eternalism. You seem to not understand the view.Although I understand why an Eternalist would prefer for that section of the timeline to remain in existence
The train example may or may not permanently end time for the entire universe, depending on answers to questions concerning how subsequent jumps are handled.That isn't truncating the timeline; it's truncating human existence. Time continues to "move forward" with or without us.
No. The Titanic sinks in 1912. Humanity goes extinct in 2316. Those are eternalist statements since they contain no references to the present. Events still occur at specifiable times, which is what 'happens' means.Doesn't this imply that nothing ever happens in an Eternalist universe?
Ted is home at 7AM, Ted is at school at noon. Ted must travel to be at different places at different times.Therefore, there is no such thing as travel?
Work through the Alice example. I didn't keep it to myself.Did you mention the solution already or are you keeping it to yourself?
Someone could see it disappear, I suppose
— Luke
This seems contradictory. — noAxioms
I said that the timeline gets overwritten, but you've somehow interpreted that (to be the opposite of what I said) as "no overwrite, but just truncation".
— Luke
Overwrite means the time between 1990 and 2024 still existrs, but gets changed as time makes its way across that period. Truncation means it is gone, and the new write is added to the end of existing history, which is at 1990. The two are the same after 2024 is reached again, or until there is another travel event. — noAxioms
You are correct that the pre-time travel period of 1990-2024 "no longer will happen", but only because it already did happen.
— Luke
You have a funny definition of 'did happen'. Those are future events, and if it's 1990, they're not in the past and thus the use of past tense is misleading. — noAxioms
This is what I mean by you referencing two dimensions of time. One is the time I'm talking about, where 1990 comes before 2024, and the other is the time containing the first kind of time. — noAxioms
Along the x axis, the present is at 1990 more than once, and the 2nd 1990 happens after the first 2024, but all of it 'happens' at some point. That corresponds more to no time travel at all, and history isn't deleted at all, but rather the state of the universe is simply reset to a prior state the exception of the contents of the machine which are protected from the overwrite everywhere else. — noAxioms
I think, but am not sure, than when you get in you machine and set the coordinates for some destination, that you select a value on the y axis and not on the x axis, but it isn't really clear. — noAxioms
One cannot fully understand your view unless forward travel is described. Sticking to this one-backward-jump case leaves several open questions. — noAxioms
Although I understand why an Eternalist would prefer for that section of the timeline to remain in existence
— Luke
Things don't 'remain' or 'go in or out of' existence under eternalism. You seem to not understand the view. — noAxioms
Doesn't this imply that nothing ever happens in an Eternalist universe?
— Luke
No. The Titanic sinks in 1912. Humanity goes extinct in 2316. Those are eternalist statements since they contain no references to the present. Events still occur at specifiable times, which is what 'happens' means. — noAxioms
Therefore, there is no such thing as travel?
— Luke
Ted is home at 7AM, Ted is at school at noon. Ted must travel to be at different places at different times. — noAxioms
That opens the door to the paradoxes, but it also allows a time machine to exist uncreated. Your view I think doesn't support that. — noAxioms
The question is unresolved until you clarify how subsequent time travels work,. In particular, what happens to the object at the location where the machine 'appears'? Does it murder the person there? Does it look for a relatively harmles place to appear? What if a million machines all try to go to the same spot? Eventually space will run out for them all, and Earth collapses into a black hole from too many DeLoreans. — noAxioms
It makes no difference in the single-travel-event scenario, and 60 posts into this, multiple events remain out of consideration.I don't see that there's much difference between 'overwrite' and 'truncation'.
...
It makes little difference post-time travel. — Luke
As I said, you seem to order events per the x axis, and I tend to order events along the y axis. I presume you saw my picture. You will note the absence of numbers along the x axis since it was unclear what to put there. One could put Bob's age there, but that would only work if Bob takes part in every time jump ever.The time machine's departure from 2024 did happen before its arrival in 1990. Otherwise, you are simply prohibiting the possibility of time travel by stipulating that all events - and all use of tensed language - must obey date order.
No. You need the 2nd line to order all the different times that a given year appears. My graph shows that, and all you posts reference this x-axis kind of time. Machine gets created. After that, machine gets used. After that, creation of machine gets overwritten. All nice and causal.If you accept that history gets overwritten, then I think there would be only one axis/timeline.
It can't be. There is no future, since it needs writing first. The machine would, at minimum, be forced to wait for the destination to come around, holding its occupant in stasis all the while similar to cryonics but without the cold.Forwards time travel is just like backwards time travel.
Why would you want that? There seems to be no point.The timeline that would have existed if there had been no time travel events gets overwritten (from the time machine's arrival date onwards) by a new timeline which includes a time travel event and its effects.
No, there can be no overwriting or anything. There is no writing at all. There is but the one timeline (or more if you want), but they don't change. Change is something applicable to something contained by time.I know that things don't remain or go in or out of existence under eternalism. That's why I said that an Eternalist would prefer for the overwritten section to remain in existence
An event 'happens' at the location of the event. Not sure how else to say it. The time coordinate assigned to the event might be frame dependent, but the event itself is objective.I'm aware that the words "happen" and "occur" are usually synonymous, but it's unclear what it means for an event to "happen" or to "occur" on an Eternalist timeline
I think not. I mean, by calling it an event, an implication is made that the event exists at a point in spacetime, and all points in spacetime have a location on the time dimension, just like they have a location in the spatial dimensions.Do the terms "happen" and "occur" mean anything other than that the event exists?
No, that's not true. The length of my table might exist, but it's not something that 'happens'. It was the word 'event' that carries an implication of being part of spacetime, and that, coupled with a premise that spacetime exists, implies that an event exists.If Eternalists take "exist" to be synonymous with "happen"
Not sure what 'cease to happen' means, but events, by definition, 'happen' somewhere. They would perhaps be said to exist in the spacetime of which they are part.then, since Eternalist events do not cease to exist, they must also not cease to happen.
AgreeThere is no past tense of events having existed or having happened for the Eternalist.
Ouch. No! There is no repeat. They happen once. An event cannot have multiple temporal locations. An except to this is the usage of a coordinate system that does not exhibit a 1-1 correspondence of events to coordinates. Under such coordinate systems (such as a variable acceleration one), events can have multiple valid sets of coordinate values, and thus 'happen' more than once, and in more than one location. One of the best illustrations of this is the Andromeda paradox, which leverages such a coordinate system.This implies that, instead of the usual sequential progression of events wherein later events occur after earlier events, on an Eternalist timeline all events are happening en masse at their respective times and each event happens repeatedly.
I am not sure how you distinguish the terms 'happen' from 'begin to happen', but events do happen. A process that has duration (a house fire say) is something that begins to happen, but an event, being a point in spacetime, has no duration.therefore [events]also do not begin to happen
No. 'Is happening' is a reference to the present. Please don't make up your own ideas for eternalism. There is no repeat to it.Like all events on the Eternalist timeline, the sinking of the Titanic in 1912 and humanity's extinction event in 2316 are both always happening
Different usage of the same word. Yes, Ted's life is a progression from his early times (conception) to his death. All those events exist. They all happen. They are ordered, so in that sense, there is a progression. There is no special event which is 'current', which moves along his worldline. In that sense of the word, there is no progression.Travel is something which happens or occurs, and the word "travel" usually means there is something which progresses (in this case, Ted) from one place to another. Yet, you say "there is nothing which 'progresses' at all."
Not sure what black holes have to do with our timelines. I don't anticipate either of our lines being in a black hole.Black holes exist in our universe and haven't ended our timeline.
It makes little difference post-time travel.
— Luke
It makes no difference in the single-travel-event scenario, and 60 posts into this, multiple events remain out of consideration. — noAxioms
As I said, you seem to order events per the x axis, and I tend to order events along the y axis. I presume you saw my picture. You will note the absence of numbers along the x axis since it was unclear what to put there. One could put Bob's age there, but that would only work if Bob takes part in every time jump ever. — noAxioms
No. You need the 2nd line to order all the different times that a given year appears. — noAxioms
Forwards time travel is just like backwards time travel.
— Luke
It can't be. There is no future, since it needs writing first. The machine would, at minimum, be forced to wait for the destination to come around, holding its occupant in stasis all the while similar to cryonics but without the cold. — noAxioms
The timeline that would have existed if there had been no time travel events gets overwritten (from the time machine's arrival date onwards) by a new timeline which includes a time travel event and its effects.
— Luke
Why would you want that? There seems to be no point. — noAxioms
Are we going to discuss the contradictions that might arise by having Bob (or others) make more than just the one jump? It all works great and intuitive for a single jump, but the differences in the interpretations really comes out when everybody has one.
I also notice that you've dropped the discussion of Alice at the tracks, ending the universe. That was one consequence of the truncate interpretation: a universe that cannot progress. — noAxioms
I know that things don't remain or go in or out of existence under eternalism. That's why I said that an Eternalist would prefer for the overwritten section to remain in existence
— Luke
No, there can be no overwriting or anything. There is no writing at all. There is but the one timeline (or more if you want), but they don't change. Change is something applicable to something contained by time. — noAxioms
I'm aware that the words "happen" and "occur" are usually synonymous, but it's unclear what it means for an event to "happen" or to "occur" on an Eternalist timeline
An event 'happens' at the location of the event. Not sure how else to say it. — noAxioms
Do the terms "happen" and "occur" mean anything other than that the event exists?
— Luke
I think not. — noAxioms
I mean, by calling it an event, an implication is made that the event exists at a point in spacetime, — noAxioms
If Eternalists take "exist" to be synonymous with "happen"
No, that's not true. The length of my table might exist, but it's not something that 'happens'. — noAxioms
Not sure what 'cease to happen' means, but events, by definition, 'happen' somewhere. They would perhaps be said to exist in the spacetime of which they are part. — noAxioms
This implies that, instead of the usual sequential progression of events wherein later events occur after earlier events, on an Eternalist timeline all events are happening en masse at their respective times and each event happens repeatedly.
— Luke
Ouch. No! There is no repeat. They happen once. An event cannot have multiple temporal locations. — noAxioms
Point is, there is still a sequence for the sort of events you're imagining: Titanic sinks before WWII.
What eternalism lacks is the premise of a 'present' moment, objectively separating all events to three ontological states of 'past, present, and future'.. Any reference to the thing not posited is meaningless under eternalism. Hence the lack of tensed verbs, since such verbs carry a reference to the thing not posited. — noAxioms
I am not sure how you distinguish the terms 'happen' from 'begin to happen', but events do happen. A process that has duration (a house fire say) is something that begins to happen, but an event, being a point in spacetime, has no duration. — noAxioms
Like all events on the Eternalist timeline, the sinking of the Titanic in 1912 and humanity's extinction event in 2316 are both always happening
— Luke
No. 'Is happening' is a reference to the present. Please don't make up your own ideas for eternalism. There is no repeat to it. — noAxioms
Travel is something which happens or occurs, and the word "travel" usually means there is something which progresses (in this case, Ted) from one place to another. Yet, you say "there is nothing which 'progresses' at all."
— Luke
Different usage of the same word. Yes, Ted's life is a progression from his early times (conception) to his death. All those events exist. They all happen. They are ordered, so in that sense, there is a progression. There is no special event which is 'current', which moves along his worldline. In that sense of the word, there is no progression. — noAxioms
Not sure what black holes have to do with our timelines. I don't anticipate either of our lines being in a black hole. — noAxioms
I did it with one time travel event, a scenario you seem to refuse to comment on directly except to say you apparently don't get it.I fail to see how your examples of multiple time travel events end the timeline. — Luke
March it does, but in the example I gave, it just paces back and forth. That needs to be resolved I think before we consider multiple machines.I only see that they end the existence of humanity, which is not the same. With truncation or overwrite, time still marches on.
One can shade all the regions below the line. Those are events that exist (history that is written) at a given time on the x axis. One cannot ask what the state of 1990 is (a time on the y axis) because it has multiple states, being written more than once.Where on your graph does it show that the timeline is overwritten from 1990 onwards and that the pre-time travel 1990-2024 period ceases to exist?
Neither did I. Bob is traveling to it, but it must happen first before he can arrive, else he ends up in a blank universe not yet written. It would presumably be subjectively instant to Bob, just like it is backwards.I never said that future events must actually happen before there can be time travel to a future time.
It makes sense to leave a copy of Bob behind? No time-travel fiction portrays it that way. Doesn't make it wrong, but it makes it into a cloning machine. The army would love it. Millions of somewhat disposable trained soldiers at the push of some buttons.I don't really want that; it's just how forward time travel makes sense to me.
That's sort of one outcome depending on the answers to questions I've asked: What happens when multiple travel events target the exact same space and time? In my example, they're all the same travel event, but happening repeatedly in a different sort of loop that causes collisions. There can be an odometer this time, but outside the machine, not inside.You said the result would be a bunch of cars all arriving in the same location causing a black hole.
Then comment on the example. Where does my description of it go wrong? All I have is 'I don't get it'. I need to know what part you don't get.This does not explain how the timeline ends. Otherwise, I do not understand how the timeline is supposed to end in your Alice example.
Not sure how to word it differently. The Titanic sinks on some 1912 night. That is a statement of something that happens. Relative to the night before, it has not yet sunk, and the night after, it is at the bottom of the ocean. Somewhere between those two events does the sinking 'happen'. It's not much different than presentism except there is no preferred moment that has to somehow glide across that event in order for the event to cycle through the different ontological states of 'happening' and then 'happened'. All events have equal ontology. Besides that, there is very little difference with the standard definition of 'happens'.That's not very helpful. I'm asking you what it means.
That was a bad answer. I think the two words mean essentially the same thing as each other, but you didn't ask that. You asked if the words mean 'exist'. No, the words do not mean 'exist'. The laws of physics might be said to exist, but they're not something that 'happen' or 'occur'. There's not a place at which the laws of physics specifically occur.Do the terms "happen" and "occur" mean anything other than that the event exists?
— Luke
I think not.
— noAxioms
No, at a point in spacetime. Time is 1 dimensinal, but spacetime is 4D. An event is a point in 4D spacetime, just like a location is a point in 3D space. The latter, plus a moment in time, are all frame dependent things. Events are invariant: They're not dependent on a frame choice.I find it odd that you refer to an event as occurring at a single point in time.
That's the colloquial definition. I'm talking about the physics definition. Yes, an event can be bigger than a point. The sinking of the Titanic took place over a kilometers and a few hours, but from a distance, that's a point, just like Earth is treated as a massless spatial point in something like the twins paradox.I suppose the word could be used in this way, but I typically think of events as having a duration; lasting for a period of time.
I did. I misread the question.You've just told me that the terms "happen" and "occur" do not mean anything other than that the event exists.
Dimension yes, but it is a temporal one. One can still translate seconds to meters if you want. The units are interchangeable under the constant c.Also, since eternalists treat time as a spatial dimension
I suppose you can say the table 'happens'. Mine is of size 40 years and its current length started 'happening' perhaps 34 years ago, and counting, all depending on how one chooses to measure its length of course. But when I speak of an event, I'm usually talking about something that is best treated as a point.why wouldn't they say that the length of your table happens, just like the length of an event (i.e. a process) happens? What's the difference?
You said events happen repeatedly.I never said an event "has multiple temporal locations".
OK. I'm unclear on the distinction between all the events happening at their respective times, and them all happening en masse at their respective times. The latter wording would seem to be opposed to some of the events happening at their respective times, but other not.I said "all events are happening en masse at their respective times."
OK. A fire begins to happen, and goes out at a later time, both ends being different events, with the fire being the process between. And yes, if you use 'event' to describe something with duration, like a concert, then it obviously begins to happen and later ceases to happen.Ah okay, I see now that I've been using the term "event" to refer to what you call a "process". I will adopt your terminology henceforth. I note that a process requires progress.
Horrible word choice, but I suppose so. That is not to say that they all exist at a present time, but 'present' in the sense of 'present and accounted for'.Right. I'm suggesting that, in order to say that all events exist/happen under eternalism, then all times must be, in a sense, present.
They don't happen at all times. Each event has a time coordinate and only happens at that time.All events exist and happen at each of their respective times. Since they all exist and happen at all times,
That's just causality doing its thing. Classically, a later state is a function of prior states,. That works in both directions, but there is the arrow of time which indicates which way is forward.I don't follow why they should happen in a sequence from earlier to later, so that they apparently happen one after another.
Nothing of the sort is suggested. That is an additional premise, for which zero evidence exists. There's no empirical test for it (or, similar to the teapot orbiting past Jupiter, for its absence). Both sides have proposed all sorts of attempts at arguments for their side, but most arguments don't revolve around anything empirical.This suggests that there is a "special event which is 'current', which moves along [the] worldline,"
Again, you drag repetition into a view that implies no such thing.Instead, eternalism entails that events all happen en masse at their respective times, rather than in a sequence, one after another. But in that case, each event must happen repeatedly, without beginning or end.
Oh right... It was one of the solutions to the problem of the universe being unable to progress. Time travel (without the wormhole) violates mass conservation, but we're ignoring physics violations, so there is no limit to how many machines we can put in one place. Too much mass results not so much a black hole, but rather enough gravity to kill Alice and put a stop to what she's doing. The whole point of the train track exercise is to figure out how to get Alice out of the loop.[Black holes] was part of your Alice example
I fail to see how your examples of multiple time travel events end the timeline.
— Luke
I did it with one time travel event, a scenario you seem to refuse to comment on directly except to say you apparently don't get it. — noAxioms
March it does, but in the example I gave, it just paces back and forth. That needs to be resolved I think before we consider multiple machines. — noAxioms
One can shade all the regions below the line. Those are events that exist (history that is written) at a given time on the x axis. One cannot ask what the state of 1990 is (a time on the y axis) because it has multiple states, being written more than once. — noAxioms
I never said that future events must actually happen before there can be time travel to a future time.
— Luke
Neither did I. — noAxioms
Bob is traveling to it, but it must happen first before he can arrive, else he ends up in a blank universe not yet written. It would presumably be subjectively instant to Bob, just like it is backwards. — noAxioms
I don't really want that; it's just how forward time travel makes sense to me.
— Luke
It makes sense to leave a copy of Bob behind? No time-travel fiction portrays it that way. — noAxioms
The typical depiction is that the machine disappears, which results in the writing of history as if the travel had actually happened. If it doesn't happen, the car/machine doesn't disappear. — noAxioms
You said the result would be a bunch of cars all arriving in the same location causing a black hole.
— Luke
That's sort of one outcome depending on the answers to questions I've asked: What happens when multiple travel events target the exact same space and time? In my example, they're all the same travel event, but happening repeatedly in a different sort of loop that causes collisions. There can be an odometer this time, but outside the machine, not inside. — noAxioms
Then comment on the example. Where does my description of it go wrong? All I have is 'I don't get it'. I need to know what part you don't get.
I spelled it out in considerable detail a couple posts ago. No comments on that. — noAxioms
That's not very helpful. I'm asking you what it means.
— Luke
Not sure how to word it differently. The Titanic sinks on some 1912 night. That is a statement of something that happens. The night before it has not yet sunk, and the night after it is at the bottom of the ocean. Somewhere between those two events does the sinking 'happen'. It's not much different than presentism except there is no preferred moment that has to somehow glide across that event in order for the event to cycle through the different ontological states of 'happening' and then 'happened'. All events have equal ontology. Besides that, there is very little difference with the standard definition of 'happens'. — noAxioms
I never said an event "has multiple temporal locations".
— Luke
You said events happen repeatedly. — noAxioms
I said "all events are happening en masse at their respective times."
— Luke
OK. I'm unclear on the distinction between all the events happening at their respective times, and them all happening en masse at their respective times. The latter wording would seem to be opposed to some of the events happening at their respective times, but other not. — noAxioms
They don't happen at all times. Each event has a time coordinate and only happens at that time. — noAxioms
This suggests that there is a "special event which is 'current', which moves along [the] worldline,"
— Luke
Nothing of the sort is suggested. — noAxioms
The Titanic sinks on some 1912 night. That is a statement of something that happens. The night before it has not yet sunk, and the night after it is at the bottom of the ocean. Somewhere between those two events does the sinking 'happen'. — noAxioms
The whole point of the train track exercise is to figure out how to get Alice out of the loop. — noAxioms
We set the universe to a state where time is truncated by 30 seconds, in 30 seconds. The same state (sort of) is set each time, so a way out of the loop needs to be identified. For that, I need to know more rules than those you've given me.What I said is that I fail to see how it ends the timeline. — Luke
She's in a state where she's going to hit the button in 30 seconds. She's enough in that state that she does it. The question is, what's different about the nth time around that she doesn't, given the same initial state? There's not time for chaos theory to do its thing. Events 30 seconds from now are essentially determined, except for this machine appearing not quite in the sight of Alice who's going to hit the button in 30 seconds.As far as I can tell, nothing forces her to keep hitting the button.
What changes, that she makes a different decision than the one we know she makes, for reasons specified?She simply doesn't press the time travel button again.
OK, I presume they must. If they've not happened, wouldn't Bob appear in a blank universe, at a time where nothing had yet been written? The machine moves the present to a universe state that is nonexistent, leaving a universe with only Bob and his machine in it. It would make sense (and match all the fictions) if the machine waited for the writing of the target destination before appearing there.I never said that future events must actually happen before there can be time travel to a future time.
It takes 11 years to write that future state (assuming an 11 year jump. It also clones Bob. Sure, from the traveler's viewpoint (the only one you ever consider), it looks like he just appears there, in 2035 with F-Bob sitting there much in the same way that none of the fictions depict.I never said that the future timeline is "a blank universe not yet written.
" I referred to the future timeline that would have existed if there had been no time travel events.
You said that it goes to a "future timeline that would have existed if there had been no time travel events". If there had been no travel events, Bob would still be in the timeline instead of the machine, so aging F-Bob (the one that is not in the machine) is a copy of the not-aging S-Bob in the machine.Why would it leave a copy of Bob behind?
It disappearing would not be consistent with a timeline where 'there had been no time travel event'.The machine disappears. You did not explain why it shouldn't.
No, not under eternalism. There is no preferred moment in it. You know that, yet you persist with comments like that.It could be argued that, while the event is happening, it is cycling through successive ontological states with each successive state being the "preferred" moment.
Because the comment IS presentist.As you note, this sounds a lot like presentism.
Your words, not mine. I would never have used the word 'present' (as in not-absent) in that way, in that context.You are apparently saying that in order for an event to happen, it must be present.
True (and meaningful only) under presentism.I was trying to say that, if an event exists then it is happening.
No, they don't say that. Each event exists at a specific time, and not at the others. The comment is analogous to saying Paris and London exist in all places, and not distinct ones.Since eternalists hold that events exist at all times
My eternalism titanic example comments never say anything 'is happening'. That is a reference to a present that the view denies.The "preferred" moment is the state that is happening
As far as I can tell, nothing forces her to keep hitting the button.
She's in a state where she's going to hit the button in 30 seconds. She's enough in that state that she does it. The question is, what's different about the nth time around that she doesn't, given the same initial state? There's not time for chaos theory to do its thing. Events 30 seconds from now are essentially determined, except for this machine appearing not quite in the sight of Alice who's going to hit the button in 30 seconds. — noAxioms
I never said that future events must actually happen before there can be time travel to a future time.
OK, I presume they must. If they've not happened, wouldn't Bob appear in a blank universe, at a time where nothing had yet been written? The machine moves the present to a universe state that is nonexistent, leaving a universe with only Bob and his machine in it. It would make sense (and match all the fictions) if the machine waited for the writing of the target destination before appearing there. — noAxioms
It takes 11 years to write that future state (assuming an 11 year jump. — noAxioms
It also clones Bob. — noAxioms
Sure, from the traveler's viewpoint (the only one you ever consider), it looks like he just appears there, in 2035 with F-Bob sitting there much in the same way that none of the fictions depict. — noAxioms
Why would it leave a copy of Bob behind?
You said that it goes to a "future timeline that would have existed if there had been no time travel events". If there had been no travel events, Bob would still be in the timeline instead of the machine, so aging F-Bob (the one that is not in the machine) is a copy of the not-aging S-Bob in the machine. — noAxioms
The machine disappears. You did not explain why it shouldn't.
It disappearing would not be consistent with a timeline where 'there had been no time travel event'. — noAxioms
The timeline that would have existed if there had been no time travel events gets overwritten (from the time machine'sarrivaldeparture date onwards) by a new timeline which includes a time travel event and its effects. — Luke
It could be argued that, while the event is happening, it is cycling through successive ontological states with each successive state being the "preferred" moment.
No, not under eternalism. There is no preferred moment in it. You know that, yet you persist with comments like that. — noAxioms
You are apparently saying that in order for an event to happen, it must be present.
Your words, not mine. I would never have used the word 'present' (as in not-absent) in that way, in that context. — noAxioms
Since eternalists hold that events exist at all times
No, they don't say that. Each event exists at a specific time, and not at the others. The comment is analogous to saying Paris and London exist in all places, and not distinct ones. — noAxioms
It might be objected that there is something odd about attributing to a non-presentist the claim that Socrates exists now, since there is a sense in which that claim is clearly false. In order to forestall this objection, let us distinguish between two senses of “x exists now”. In one sense, which we can call the temporal location sense, this expression is synonymous with “x is present”. The non-presentist will admit that, in the temporal location sense of “x exists now”, it is true that no non-present objects exist now. But in the other sense of “x exists now”, which we can call the ontological sense, to say that “x exists now” is just to say that x is now in the domain of our most unrestricted quantifiers. Using the ontological sense of “exists”, we can talk about something existing in a perfectly general sense, without presupposing anything about its temporal location. When we attribute to non-presentists the claim that non-present objects like Socrates exist right now, we commit non-presentists only to the claim that these non-present objects exist now in the ontological sense (the one involving the most unrestricted quantifiers). — SEP article on Time
Really, learn the view before you start asserting what it must say. It hurts, the way you're murdering a view with which you obviously don't hold. — noAxioms
My eternalism titanic example comments never say anything 'is happening'. That is a reference to a present that the view denies. — noAxioms
There is no 'again'. She's hitting the button for the first and only time, because she's late for a very important appointment (a job interview say) and cannot afford to wait for the slow train. She hits the button the one and only time to go back 30 seconds to before the train gate coming down, and thus proceeds across the crossing to make her appointment. There's was never a repeated hitting of the button. Somebody else (the younger Alice back there) will hit the button for the first and only time, for reasons already explained.She simply decides not to hit the button again. You didn't provide any information in your scenario about why she time travels. — Luke
I never gave any indication that she's stuck on the tracks. She's at the crossing, having to wait for it, a wait she cannot afford.Presumably she does it to avoid being hit by an oncoming train.
It's her first time. There's no loop of which she can be aware, except she knows that any use of travel to the past makes the past happen again, a loops of sorts. Look at Bob who goes and makes 1990 happen a 2nd time, but differently. That's a loop of sorts, but one that only 'happens' twice since his actions there prevent young-Bob from doing his 2024 thing.Maybe she realises she can't keep looping back every 30 seconds forever and tries something different instead.
None, which is why you model, if the machine doing a forward jump doesn't wait for the destination to be written, would match any of the typical fictions.What fictions involve time travelling to a future time where nothing exists; a "blank universe"?
All of them. It's not a wait from the traveler perspective of course. He arrives having aged but a moment with no memory of any waiting.What fictions involve waiting for the future to happen first, before time travelling to it?
Sure you do. Jumping to Y3000 with a machine gets you to Y3000 just like Phillip Fry (who does it via Cryonics, an identical experience). Jumping to Y3000 via waiting gets you very very dead.It would be a pointless time machine if the user had to wait for the future to happen before one could time travel to it. You don't need a time machine in order to wait for the future to happen.
2035 is withing his own lifetime, so F-Bob (who I'm designating as the clone) is not yet dead, but he's 50. S-Bob (the time-traveling original) is 39 and meets his clone fact to face.The only cloning that happens is if Bob travels to some time within his own lifetime
Never claimed it was. Just an unusual choice of rules, since Hollywood does have an influence on most people's vision of what time travel would be like.you are yet to have proven it illogical.
That's not what you said. You said the line is written as if the travel had not taken place (so it has F-Bob in it), but with S-Bob appearing in 2035, the destination event, which thus has both of them in it.If Bob succeeds in time travelling, then F-Bob does not exist.
No, you said the line is written as if the travel had failed, so F-Bob very much exists in the line to which S-Bob travels.F-Bob only exists if Bob fails to time travel
OK, so A exists, the machine waits 11 years for line A to get to 2035, and then when it does, the history (with F-Bob) gets truncated back to 2024 and the machine has to wait an additional 11 years for the B line (no Bob at all) to get to 2035? Why can't the B line just be written from the start since F-Bob and the rest of the A line is doomed before the first moment is written?There is either a timeline without a time travel event or there is a timeline with a time travel event. Call the timeline without a (any) time travel event timeline A and call the timeline with a time travel event timeline B. If there is no time travel event then timeline A results. If there is a time travel event then timeline B results (and timeline A gets overwritten by timeline B).
No, if there had been no travel event, then S-Bob (the traveling one) doesn't exist.If there had been no time travel events then F-Bob wouldn't exist.
Yes, as described just above. The machine has to wait 22 years now for two different histories to play out over 11 years each. Weird, but not contradictory.I need to make a correction here. I said earlier that forward time travel would change the timeline from the arrival time onwards. I should have said that forward time travel would change the timeline (from timeline A to timeline B) from the departure time onwards.
Fine. The Robert in line A sees the machine stay put (fail), and a dejected F-Bob gets out The Roberta in line B sees it disappear and eventually meets S-Bob 11 years later.If there is no time travel event then the machine doesn't disappear.
Well, there was a time travel event in line A, but the observers in it have no way to tell. They would have been able to tell in 2035, but their line ends there, so they have no experience that would constitute a falsification test.The machine only disappears if there is a time travel event.
Processes are comprised of multiple events, and just like Earth (with spatial extension) can be treated as a point in some calculations, so can a process (a concert say) be treated as a point event so long as our precision is low enough that it doesn't matter.I'm just trying to get a better understanding of the distinction between the meanings of "happen(s)" and "exist(s)" in relation to an event/process under eternalism.
Yes. The event of the Titanic Sunday Apr 14 has the Titanic in a state of 'not yet sunk'. It means that the sinking event (Monday, around 2AM) is a subsequent event in the ordering of all the events along the Titanic worldline. One can say that event A is prior to B, or A is in the past of B. Such relations are valid, It is the implicit reference to a preferred moment that is meaningless.You spoke of the time before the Titanic event when "it has not yet sunk"
There are a couple (bold) implicit references to the present in all that. To reword:It seems very much as though there was a time before the event when the sinking had not yet happened, and a time after the event when the sinking had happened, and then somewhere in between those two times when the sinking was happening.
Besides the explicit reference to a preferred moment?What was wrong with my depiction that "while the event is happening, it is cycling through successive ontological states with each successive state being the "preferred" moment," where "the "preferred" moment is the state that is happening, as opposed to those that have happened or have not yet happened."
There are no such ontological differences. There is no division between such ontological differences.Does eternalism allow only for the different ontological states of 'not yet happened' and 'happened'
Wow, what a mix of multiple meanings and preferred moment references in a paragraph trying to clarify a view that denies the referent. I can see how the view might be difficult to learn from that source. Apparently there are using 'is present' to mean 'currently exists', which suggests that eternalism asserts that Socrates exists in 2024, which, itself can be interpreted as either 'Some of the events of the worldline of Socrates have a time coordinate of 2024', or as "All events exist, and a reference time of 2024 doesn't change that'. Only the latter statement is true under eternalism, and the paragraph above seems not to clarify which meaning is meant.It might be objected that there is something odd about attributing to a non-presentist the claim that Socrates exists now, since there is a sense in which that claim is clearly false. In order to forestall this objection, let us distinguish between two senses of “x exists now”. In one sense, which we can call the temporal location sense, this expression is synonymous with “x is present”. The non-presentist will admit that, in the temporal location sense of “x exists now”, it is true that no non-present objects exist now. But in the other sense of “x exists now”, which we can call the ontological sense, to say that “x exists now” is just to say that x is now in the domain of our most unrestricted quantifiers. Using the ontological sense of “exists”, we can talk about something existing in a perfectly general sense, without presupposing anything about its temporal location. When we attribute to non-presentists the claim that non-present objects like Socrates exist right now, we commit non-presentists only to the claim that these non-present objects exist now in the ontological sense (the one involving the most unrestricted quantifiers). — SEP article on time
By 'not present', I am guessing that you mean 'not at the present moment' (as opposed to 'absent', which of course is not an eternalist statement.I was saying eternalists hold that there exist events at each (and every) time, i.e. that there also exist events that are not present.
The statements as worded are both meaningless under eternalism, so instead of being true or false, both are more 'not even wrong'.Nothing is happening in an eternalist universe? The sinking of the Titanic happened but was never happening?
There is no 'again'. She's hitting the button for the first and only time, because she's late for a very important appointment (a job interview say) and cannot afford to wait for the slow train. She hits the button the one and only time to go back 30 seconds to before the train gate coming down, and thus proceeds across the crossing to make her appointment. There's was never a repeated hitting of the button. Somebody else (the younger Alice back there) will hit the button for the first and only time, for reasons already explained. — 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
At time 12:00:25, the train gates go down. At 12:00:30, Alice gets to the crossing, who's in a hurry and she's driving the DeLorean. She hits the button to go back 30 seconds.
At noon, a DeLorean appears at the tracks and proceeds across. 400 meters back, a DeLorean approaches the crossing.
At time 12:00:25, the train gates go down. At 12:00:30, Alice gets to the crossing. She hits the button to go back 30 seconds. The Alice on the other side of the crossing is truncated out of existence.
At noon a DeLorean appears at the tracks, almost exactly in the same place as the other one that appears there. OK, so there is some sort of resolution of a car appearing at the location of a car already there, so either there is an explosion and the Alices all die (yay for the universe), or one wins and truncates the other out of existence, and the cycle continues. — noAxioms
None, which is why you model, if the machine doing a forward jump doesn't wait for the destination to be written, would match any of the typical fictions.
So either the machine must wait for the destination to be written, or if it doesn't, the machine appears in an unwritten future, which is blank. — noAxioms
Sure you do. Jumping to Y3000 with a machine gets you to Y3000 just like Phillip Fry (who does it via Cryonics, an identical experience). — noAxioms
As I said, the machine has always been a cloning device. Bob goes back to 1990 where he meets another Bob. Two Bobs means one is a clone. Using this technique, you can make as many Bobs as you want, and you can do it quickly, in minutes instead of decades. So getting a clone by going forward is admittedly consistent with your going-back description, even if none of the fictions seem to depict that consistency. Hollywood has developed a rule that you can meet yourself if you go backwards, but not if you go forwards. — noAxioms
No, you said the line is written as if the travel had failed, so F-Bob very much exists in the line to which S-Bob travels. — noAxioms
The timeline that would have existed if there had been no time travel events gets overwritten (from the time machine's arrival date onwards) by a new timeline which includes a time travel event and its effects. — Luke
Why can't the B line just be written from the start since F-Bob and the rest of the A line is doomed before the first moment is written? — noAxioms
If there had been no time travel events then F-Bob wouldn't exist.
No, if there had been no travel event, then S-Bob (the traveling one) doesn't exist. — noAxioms
Yes, as described just above. The machine has to wait 22 years now for two different histories to play out over 11 years each. Weird, but not contradictory. — noAxioms
The machine only disappears if there is a time travel event.
Well, there was a time travel event in line A, but the observers in it have no way to tell. They would have been able to tell in 2035, but their line ends there, so they have no experience that would constitute a falsification test. — noAxioms
Processes are comprised of multiple events, and just like Earth (with spatial extension) can be treated as a point in some calculations, so can a process (a concert say) be treated as a point event so long as our precision is low enough that it doesn't matter. — noAxioms
Since time is one of the dimensions of spacetime, the word 'happens' is meaningful. The event happens at the location in spacetime of that event, which I realize is circular, but that's the nature of a tautology. — noAxioms
What was wrong with my depiction that "while the event is happening, it is cycling through successive ontological states with each successive state being the "preferred" moment," where "the "preferred" moment is the state that is happening, as opposed to those that have happened or have not yet happened."
Besides the explicit reference to a preferred moment? — noAxioms
Does eternalism allow only for the different ontological states of 'not yet happened' and 'happened'
There are no such ontological differences. — noAxioms
I can see how the view might be difficult to learn from that source. — noAxioms
Only the latter statement is true under eternalism, and the paragraph above seems not to clarify which meaning is meant. — noAxioms
Also not sure about the first part, that there exist events at each (and every) time. For instance, do there exist events before the big bang? I think not. Do all events have a time coordinate? I can't think of a single coordinate system that assigns coordinate values to every event that is part of spacetime, so even that isn't true. — noAxioms
.Nothing is happening in an eternalist universe? The sinking of the Titanic happened but was never happening?
The statements as worded are both meaningless under eternalism, so instead of being true or false, both are more 'not even wrong' — noAxioms
No, it doesn't. It is kind of like asking what physics has to say about if the sun suddenly wasn't there. Would Earth continue to orbit for 8 minutes or would it immediately commence a straight trajectory?Does physics describe what the above even means? — Michael
Good. This is more in line with the typical pop vision of the time-traveling vehicle. Given our growing block model, the machine still has to wait for 2035 to come around before it can materialize in it. There's problems with that, but not obvious when there's but a single time travel event in consideration.I made a mistake in my last post. ... I agree with the Hollywood version; you don't meet yourself or clone yourself going forwards. You depart from an earlier time to a later time, so there's no other version of you left behind who continues aging normally once you depart from the earlier time for the later time. You can only "clone" yourself (in a sense) going backwards. — Luke
That's Alice0, yes. She's the original. She's never time traveled, not backwards at least.So, Alice gets to the train tracks and has to stop because the gate comes down.
By 'second time around' you mean the 2nd writing of those 30 seconds, yes. Alice1 makes it across the tracks. Alice0 is a half km back from the crossing and will get there in 30 seconds, 5 seconds after the gate goes down.She decides to use her DeLorean time machine to go back 30 seconds so that she can floor it and cross the tracks before the gate comes down (the second time around). All well and good.
You seem only capable of imagining the traveler, just like Hollywood only follow the protagonist. Think about the others in the world at noon. Remember that Alice0 is in that world, half a km up the road, who is fretting about how tight her time is to make her appointment. She thinks about little else at the moment. Alice1 makes it across but Alice0 is about to erase Alice1's victory by hitting the button for the very first time in her life, truncating the history where Alice1 made it across. It sort of turns into a Groundhog-Day situation, except in Groundhog Day, the protagonist has memory of all the times through the loop. Alice doesn't. Alice0 has no memory of ever having time traveled.What I don't understand is, after she does this, why is there another DeLorean behind her getting stuck at the gates?
It doesn't? You say it does. You said Bob going back to 1990 truncates history back to 1990 so it can be overwritten with older-Bob in it now, which is exactly what Alice0 is doing, except this time younger Alice0 is working the controls, not older Alice1. Are we changing the story again?The time travel event in your scenario does not overwrite the timeline.
None that I know of anyway. Langoliers comes closest. The travelers arrive at a sort of blank future, but stay put at the moment of arrival until the 'present' catches up with them and suddenly everybody appears. It's one of the few stories that really leans on presentism, where the author is very aware of his model and tries to be consistent with it.I asked you which works of fictions involve time travel to a blank universe which has not been "written" yet. You tell me that there are no such works of fiction.
No, waiting for a bus takes subjective time, experienced by the waiter. The experience of the traveler is no waiting. The world is simply there when they arrive, sort of like super-fast spaceship and time dilation. I can go forward 11 years in a moment without having to experince waiting, if my ship is fast enough. And SEP apparently designates that as actual time travel, despite my protests.Okay then, which works of fiction wait for the future destination to be written before time travel to that future destination occurs? By "wait", I assume you mean in the usual fashion, like you might wait for a bus?
The machine has to wait. The people never do, since the experience is instantaneous to them.So you are saying that, in all works of fiction, there is no time travel to a future time which occurs before people have waited for that future time to happen?
I didn't say Cryonics was time travel. I said the experience is essentially the same to the traveler: (Step in, step out into some future year). The experience of the outside observer is not the same because they can see the machine with Cryonics, and it 'disappears' presumably if it's a time machine. Both machines have to wait for 2035 to happen, but the time machine apparently waits in some inaccessible dimension or some such. No explanation is yet given as to where it is en route.Cryonics is not a time machine; not the sort we have been discussing, so not relevant to the discussion.
OK, this is new. It just makes up a plausible state for 2035? None of the intervening years actually happen, the state is just put there? How very last-Tuesdayism. BTW, I am a total fan of last-Tuesdayism, not that I assert it, but it is something everybody needs to attempt (and fail) to falsify.It doesn't have to wait. It just travels there and overwrites what would have been.
I gave examples of the difference between the words, where substituting one for the other in a sentence would result in a wrong statement. So no, they're not synonymous.It follows from this that "happens" is no different to "exists".
I never said either. It happens at the time of the event. It exists in spacetime. All events exists in spacetime, but they don't all happen at any given time since the time of one event may be different than the time of another.It happens when it exists and exists when it happens - there is no distinction.
Yes, that's how a presentist might define the preferred moment. But that moment is not postulated in eternalism. If you want to understand eternalism, don't drag in definitions and premises from an incompatible view.I defined the preferred moment as "the state that is happening, as opposed to those that have happened or have not yet happened". What's wrong with that?
Meaningless due to the implicit references to the present. One can say that relative to 2080, 2070 has already happened. That's an explicit relation reference. Tensed verb work as long as the reference moment is explicitly stated.Does eternalism allow for events to have happened, and for events to have not yet happened, but not for events to happen? Why?
Both are meaningless. They are both references to the present. How can you not see this?Does eternalism allow only for the different ontological states of 'not yet happened' and 'happened'
Yes, all references to explicit times, not implicit references to the present.You described them as such in your Titanic example. You described a time when the Titanic had not yet sunk, and a later time when it had sunk, and then you said "Somewhere between those two events does the sinking 'happen'."
Not our spacetime. The geometry outside our spacetime is not really known, It isn't know if 'geometry' is the right word for it even.[/quote]Is "before the big bang" part of spacetime?
First of all, the statement is false since I can think of a time that has no events. Secondly, I know of no coordinate system that accounts for every event (assigns a value to its coordinates), so the bit about a requirement of all events being accounted for is not there for a coordinate system, but it kind of is there for spacetime. Spacetime is physical. Coordinate systems are abstractions.The statement "there exist events at each (and every) time" does not require every event to be accounted for, as long as there exists at least one event at each and every time.
Not even wrong.Nothing is happening in an eternalist universe?
So, Alice gets to the train tracks and has to stop because the gate comes down.
That's Alice0, yes. She's the original. She's never time traveled, not backwards at least. — noAxioms
By 'second time around' you mean the 2nd writing of those 30 seconds, yes. Alice1 makes it across the tracks. Alice0 is a half km back from the crossing and will get there in 30 seconds, 5 seconds after the gate goes down. — noAxioms
You seem only capable of imagining the traveler, just like Hollywood only follow the protagonist. — noAxioms
Think about the others in the world at noon. Remember that Alice0 is in that world, half a km up the road, who is fretting about how tight her time is to make her appointment. She thinks about little else at the moment. Alice1 makes it across but Alice0 is about to erase Alice1's victory by hitting the button for the very first time in her life, truncating the history where Alice1 made it across. It sort of turns into a Groundhog-Day situation, except in Groundhog Day, the protagonist has memory of all the times through the loop. Alice doesn't. Alice0 has no memory of ever having time traveled. — noAxioms
The time travel event in your scenario does not overwrite the timeline.
It doesn't? You say it does. You said Bob going back to 1990 truncates history back to 1990 so it can be overwritten with older-Bob in it now, which is exactly what Alice0 is doing, except this time younger Alice0 is working the controls, not older Alice1. Are we changing the story again? — noAxioms
None that I know of anyway. Langoliers comes closest. The travelers arrive at a sort of blank future, but stay put at the moment of arrival until the 'present' catches up with them and suddenly everybody appears. It's one of the few stories that really leans on presentism, where the author is very aware of his model and tries to be consistent with it. — noAxioms
No, waiting for a bus takes subjective time, experienced by the waiter. The experience of the traveler is no waiting. The world is simply there when they arrive, sort of like super-fast spaceship and time dilation. I can go forward 11 years in a moment without having to experince waiting, if my ship is fast enough. And SEP apparently designates that as actual time travel, despite my protests. — noAxioms
I don't think many works of fiction explicitly rely on this growing-block model that you have going on here, so concepts like a new history growing simply don't apply. — noAxioms
So you are saying that, in all works of fiction, there is no time travel to a future time which occurs before people have waited for that future time to happen?
The machine has to wait. The people never do, since the experience is instantaneous to them. — noAxioms
I never said either. It happens at the time of the event. It exists in spacetime. All events exists in spacetime, but they don't all happen at any given time since the time of one event may be different than the time of another. — noAxioms
I gave examples of the difference between the words, where substituting one for the other in a sentence would result in a wrong statement. So no, they're not synonymous. — noAxioms
I never said either. It happens at the time of the event. It exists in spacetime. All events exists in spacetime, but they don't all happen at any given time since the time of one event may be different than the time of another. — noAxioms
I defined the preferred moment as "the state that is happening, as opposed to those that have happened or have not yet happened". What's wrong with that?
Yes, that's how a presentist might define the preferred moment. But that moment is not postulated in eternalism. If you want to understand eternalism, don't drag in definitions and premises from an incompatible view. — noAxioms
Does eternalism allow for events to have happened, and for events to have not yet happened, but not for events to happen? Why?
Meaningless due to the implicit references to the present. — noAxioms
Does eternalism allow only for the different ontological states of 'not yet happened' and 'happened'
Both are meaningless. They are both references to the present. How can you not see this? — noAxioms
The Titanic sinks on some 1912 night. That is a statement of something that happens. Relative to the night before, it has not yet sunk, and the night after, it is at the bottom of the ocean. Somewhere between those two events does the sinking 'happen'. It's not much different than presentism except there is no preferred moment that has to somehow glide across that event in order for the event to cycle through the different ontological states of 'happening' and then 'happened'. All events have equal ontology. Besides that, there is very little difference with the standard definition of 'happens'. — noAxioms
Is "before the big bang" part of spacetime?
Not our spacetime. The geometry outside our spacetime is not really known, It isn't know if 'geometry' is the right word for it even. — noAxioms
Also not sure about the first part, that there exist events at each (and every) time. For instance, do there exist events before the big bang? I think not. — noAxioms
The statement "there exist events at each (and every) time" does not require every event to be accounted for, as long as there exists at least one event at each and every time.
First of all, the statement is false since I can think of a time that has no events. — noAxioms
Secondly, I know of no coordinate system that accounts for every event (assigns a value to its coordinates), so the bit about a requirement of all events being accounted for is not there for a coordinate system, but it kind of is there for spacetime. Spacetime is physical. Coordinate systems are abstractions. — noAxioms
The phrase "nothing is happening" is not a meaningful one in an eternalist universe, — noAxioms
No, it doesn't. It is kind of like asking what physics has to say about if the sun suddenly wasn't there. Would Earth continue to orbit for 8 minutes or would it immediately commence a straight trajectory?
Another question: Does an infinite sheet of material (a meter-thick slab of concrete say) result in a uniform gravitational field?
Physics has nothing to say about either case since there is no way to describe what any of the above even means.
Luke is exploring a philosophical question about the implications of various philosophical models on the concept of time travel. The current model seems to be a sort of growing block model, which is full of contradictions, most of which have been left unexplored due to the slow pace of working through even the trivial bits. — noAxioms
Well, I think any reasonable philosophy needs to take account of the facts. According to General Relativity, time is the fourth dimension of spacetime. — Michael
Talk of "overwriting" the "timeline" is like talking about "overwriting" the "depthline" or the "widthline" or the "heightline". It seems pretty nonsense. — Michael
Well, I think any reasonable philosophy needs to take into account the facts as we best understand them. According to General Relativity time is the fourth dimension of spacetime. Talking about "overwriting" the "timeline" is like talking about "overwriting" the "heightline" or the "widthline" or the "lengthline". It seems pretty nonsense.
What does it mean to "overwrite" a direction in space(time)? — Michael
:up: :up:The only possible way is if the multiverse is true, if all probabilities has their own branch, but then there's no point in going back in time to do anything as you cannot change the future you came from. It would be closer to traveling to other universes rather than specifically traveling back in time. And any change would only just fraction into new branches ... — Christoffer
That would assume an eternalist view of time, in which time is treated much like a length, or as another spatial dimension. Whereas - prior to the untimely demise of this discussion - I was seeking to explore the limitations of eternalism, such as its logical omission of progress, happening or motion; characteristics that I consider to be absent from eternalism but logically aligned with the opposing view of presentism. However, many eternalists disagree. — Luke
there exists a history — Luke
I assume you're also against the growing block theory of time? — Michael
As you may recall from previous discussions on time, my ontology of time involves a blend of presentism and eternalism (in short, that without presentism there is no 'progression of events', and without eternalism there is no timeline(s) of events). — Luke
I believe that a combination of both views of presentism and eternalism are required to coherently account for time. — Luke
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