If someone outside the hole applies the appropriate transformations to their forever-falling astronaut, they will find that form the astronaut's perspective the fall is finite. — Banno

No such transformation exists since the astronaut never crosses the event horizon, so there can be no transformation of events beyond that from either frame to the other.

If the astronaut applies the appropriate transformation, they will find that for someone outside the hoel the fall takes forever - or more.

He cannot apply the transformation, which is what is meant by events that cannot be consistently assigned a spot on the outside observer's timeline. His events do not exist at all on that outside timeline.

That is a limitation of inertial frames, not of the physical universe. — Kenosha Kid

Exactly, which is why I say that inertial frames do not describe the universe.

Also, you seem to think that if we see light from a star 13.4B LY away, there must have been a time when that star was very close to us. That is not right. It didn't have to "move 13.4 BLY away and then send a signal back". Stars did not emerge from the big bang.

The material/energy from which they are comprised very much did.
Cosmologists estimate that the light we see now from GN-z11 was emitted when the universe was around 0.4 BY old, and was emitted at a proper distance from here of about 2.8 BLY at the time, which is closer than the emission distance of other galaxies with somewhat lower redshift. Light from a galaxy with redshift z=2 for instance was emitted at a proper distance of around 5.8 BLY away. That has the unintuitive effect that the more distant galaxy (the one receding faster) appears larger (greater angular measure) than a similar size object that is closer. Were the same two objects to be viewed in a Minkowski inertial universe, the angular measure of the higher redshift object would be smaller.

the current inertial frame of Earth won't do: There are objects beyond our event horizon (events from which light can never reach us even in infinite time).
— noAxioms

I don't see why an absolute coordinate system would be obligated to propagate that the speed of light. — Banno

A coordinate system doesn't propagate. You mean light propagates at c in a coordinate system. This is more or less true for an intertial coordinate system, with variation on speed due to changes in gravitational potential. So light from another star often gets to us at slightly greater than c due to most of the trip taking place in space at higher gravitational potential than we have here.
Light in an inertial coordinate system can get from any location to any other in a time dependent on the separation of the two locations. This does not describe our actual universe.

Hence, those events that are beyond our event horizon nevertheless might have a particular position in an absolute coordinate system.

They do in some coordinate systems, but they don't have a particular position in our inertial frame.

The answer to your question seems to me to be that any coordinate system might be set up as absolute; relativistic physics specifies how we translate from any frame to any other frame, so calling any frame of reference absolute becomes simply irrelevant.

No coordinate system works. That's been my point. Every choice leaves parts of spacetime unordered. As Enai puts it: There are always events that cannot be consistently assigned a spot on any choice of objective timeline.

Worse, at the event horizon, time dilation becomes so extremely that, from the perspective of the outside observer, events there do not ever occur- not even after an infinite amount of time has passed. — Enai De A Lukal

I need your opinion then. OK a foliation based on the perspective some outside observer cannot account for events beyond the event horizon, and thus seems to not to be a viable candidate for an objective foliation of all of spactime. Is there some other coordinate system that is actually up to the task? If not, is this a valid falsification of objective space and time such as is proposed by Lorentz Ether Theory? This is not even including those interpretations that additionally posit a preferred moment in time.

So you drop an absolutist into a black hole, then ask him, what's your brother doing now? His inability to give a coherent answer seems to falsify his view, but then until we drop him in like that, I suppose he's free to deny the interior events altogether, which seems to be the only recourse.

could multiverse theories be an attempt to explain causation prior to the Big Bang? — 3017amen

There are at least six kinds of multiverses discussed. Tegmark enumerated them as Level 1 (other Hubble spheres), Level 2 (other bubbles in eternal inflation theory), Level 3 (other quantum worlds), and Level 4 (other unrelated structures). There is also the Smolin evolutionary thing where the interiors of black holes are considered to be other universes. If Level 1 is our universe but spatially 'not here', then there should be a Level 0 which is our universe but temporally 'not now'. That's six at least.
Of those, it is probably the Level 2 multiverse that most qualifies as an attempt to explain causation of the Big Bang. It is also the model that explains the fine-tuning argument.
The Smolin evolutionary thing also seems to attempt this, but each universe created is of infinitesimal magnitude (matter and energy and such) compared to its parent, so it's hard to see how that can continue for enough generations for evolution to be effective.

As a very rudimentary example, what in theory, would exist outside of the block universe?

Whether it is interpreted as block or not seems immaterial. Look into eternal inflation theory. Wiki has a terse entry on it. I found a more comprehensive description in Tegmark's Mathematical Universe with some illustrations that help with visualization. There are other 'universes' that have different number of spatial and temporal dimensions, and the vast majority of them cannot produce complex physical states.

The wiki site says it was emitted 13.4 billion years ago, but it could not have got far enough away in only 400M years for light to take that long. Of course, wiki isn't using inertial coordinates when making that statement, so kindly describe the situation in those terms. Where is the emission event?
— noAxioms

Right. So, first, there was a supposed stupendous inflation period in the early universe that cannot be described by any inertial frame. — Kenosha Kid

GN-z11 is about 2/3 of the way to the edge of the visible universe. Immediately after inflation, the size of the visible universe was anywhere from a grain of sand to a city block, depending on your model. A 1 meter head start isn't going to get that object (or rather, the material that would eventually become it) out far enough to be 13.4 GLY away when that light is emitten only 400 MYr later

Second, it is unexpected that the galaxy would have formed 400M years after the big bang

OK, you're allowed to give it more time, but how long do you want? It's going to take 13.4 billion years to get far enough away, at which point there's no time left to send the light back to us here.

i.e. it is a cosmological and astronomical mystery but a) that doesn't stop it being 13.4 billion light years away from us when it did form

Actually it does stop it. It's not a mystery, it's a physical impossibility in an inertial coordinate system for something to move 13.4 BLY away and then send a signal back, all in 13.8 BYr. Waving your hand around and spreading 'I don't know/it's a mystery' dust all over the place isn't a viable model.

I take it you're not familiar with the comoving coordinate system (which does foliate spacetime to any distance) or the FRW models of the universe (from which that 13.4 BY figure comes). I'm not here to debate the viability of an inertial coordinate system to describe the universe. Trust me, it isn't a candidate. I'm here to discuss my argument against absolute time, with people who know their physics sufficiently to comment productively on it. This is not that discussion.

It's perfectly appropriate for that: that's just light further outside the light cone. It being further away just means its further away. Minkowski spacetime is not appropriate for gravity, though. — Kenosha Kid

You don't comprehend my explanation, so I'll try to comprehend your vision.

Perhaps you can explain a distant galaxy then using this coordinate system. Gravity at very large scales is negligible, so space is effectively flat so long as we're not noticing lensing effects and such.
So take GN-z11, a very distant thing with redshift of over 11.
Using your coordinate system, where (and when) is the event when the light was emitted that we see of it today? The wiki site says it was emitted 13.4 billion years ago, but it could not have got far enough away in only 400M years for light to take that long. Of course, wiki isn't using inertial coordinates when making that statement, so kindly describe the situation in those terms. Where is the emission event? If it vanishes today, will we ever see that from here if we wait long enough?

I don't see how that is a consequence of a global inertial frame. Light may not reach us for other reasons unrelated to it, one of which is the cosmic expansion of the universe being faster than light. — Mr Bee

There is no cosmic expansion under inertial spacetime. There is only an explosion of stuff from a point, with nothing moving at faster than c.

If there is a boundary to an inertial frame, then event outside that boundary do not exist in that frame.
— noAxioms

You seem to be mixing up the boundary of the observable universe with the "boundary" of an inertial frame, the latter of which I don't really understand. They are both not the same.

They are indeed not the same. The boundary of our inertial frame is much less than the 47 BLY radius of the observerable universe, and even less than the ~16 BLY distance to the event horizon. The current radius of our inertial frame must be 13.8 BLY because nothing outside that radius could have come from the big bang without moving faster than c, and nothing moves faster than c in an inertial frame.

My understanding is that it is mainly spacetimes with closed timelike curves that preclude the existence of global hypersurfaces, but I haven't heard anything about black holes doing the same.

Your understanding here is fine. Nobody is proposing a closed timelike curve. Any foliation, objective or not, would preclude that.

I got lost at:

The [clock] is dropped from a hovering location outside, which shines light down on the dropped clock.
— noAxioms

It's not clear what frame of reference we're in here. — Kenosha Kid

First of all, I meant dropping a clock, which seem more useful than dropping a glowing rock. I used a rock at first and neglected to change them all to 'clock'. But it moves like the rock: not under propulsion or anything.

The light shines from the hovering station. It can be light from the clock displaying the time if you will. The time is the proper time of the hovering space station that maintains a constant distance from the black hole. We can build a shell around if you like it so we don't need to expend fuel to stay indefinitely at that location.

From the perspective of an observer outside the event horizon (with some magic blackholescope), the clock will accelerate toward the singularity and run slower and slower. Any photons emitted from the rock (which is getting further and further away from the clock) will still travel at the speed of light and catch up with the clock, because the clock cannot move at the speed of light.

I've caused confusion. The rock and the dropped clock are the same thing. The space station can watch it fall in, but if it reads time T when it crosses the event horizon, then the space station will never see the clock read anything after T. It will appear from the space station to slow and approach but never reach T. Event B is that clock when it reads T+1.

From the rest frame of the clock, it is in perpetual free fall. Eventually the rock will simply recede so far into the distance it cannot be detected.

Again, they are the same thing, so the clock indeed will eventually reach the abrupt end of time and tick it's last, so to speak. This is assuming the clock is a point device that isn't destroyed by excessive violence like tidal forces before it gets to the singularity.

If you want to describe a clock and a rock dropped say at separate times, you need to lay out the scenario. I never meant for there to be two things falling like that.

So your perspective is more psychological and related to our conscious experiences. Is this a Berkeley or Kantian strategy you are gleaning from in treating spacetime as a fundamental psychological process but nothing more? — substantivalism

I said it is a psychological choice when I decide what components comprise a system or not. The physics of the relationalism has zero to do with this choice.

I get that this philosophical viewpoint is not emprically well-founded and never could be (it would be consistent with any personal experience) but it always felt relatively possible. — substantivalism

I find the acquisition of new information to be a contradiction in the solipsistic idealist view. Say you find a tomb full of Egyptian writing and spend years trying to decipher it. You've memorized every character and could reproduce it at will from memory, yet you cannot read it. After years of study, you finally break the code and learn the language, and suddenly there is information that was always there, but suddenly is meaningful to you. That implies there is something out there that didn't come from you. I cannot dream of a coherent language that I don't yet understand. Something else has to have produced that tomb, which contradicts your experience being more fundamental than the noumena. That contradiction sinks the view in my opinion.

Two quick questions:

1. Does black hole time travel increase or decrease Time ( I can't remember)?
2. Do black holes contribute to Multiverse theories at all? — 3017amen

Time slows (is more dilated) when deep in a gravity well, So clocks on Earth for instance run objectively slower than say GPS clocks (which are very high up and not moving fast). Those GPS clocks are slowed due to their orbital motion, but the gravity effect is greater at that altitude. Clocks on the ISS run slower than the ones on the ground due to minimal gravitational potential difference in low orbit, coupled with significant dilation from the higher orbital velocity. So at an altitude of 1.5 R (R being Earth's radius), the two effects cancel out and orbiting clocks can be synced indefinitely with those on the ground.

Similarly, from the PoV of the distant observer, a clock falling into a black hole freezes on the event horizon. It doesn't just appear to freeze. Coordinate time slows and actually stops there.
From the PoV of the observer falling in, he sails right in without a hitch, and the universe behind him appears to speed up, but not infinitely so. There's definitely a time outside the black hole beyond which is not part of his past light cone, and thus is not observable.

About the multiverse thing, I think there are theories that a black hole in one universe is a white hole from the perspective of the interior spacetime. I think we're possibly supposed to be in such a white hole in some of these theories, except I don't see how we could be expanding then. There's no singularity (big crunch) at the end of time like one would expect from a geometry with an abrupt cessation of time like that.

Thanks for your initial responses.

I've been in discussion about this on physics sites, but they don't care so much there about the metaphysical implications to absolute time interpretations.

As you can see, any event can be located in an inertial frame, but only those events within our past light cone can be detected by us now. Events outside that cone are still in the reference frame but cannot influence us. — Kenosha Kid

You've drawn flat Minkowski spacetime (with arbitrary inertial frame) in which light from any spatial location will reach any other location. That makes it an inappropriate model of the large scale universe where light that is currently say 17 GLY away will never get here, not in 17 billion years or ever.
Earth has an event horizon, and Minkowski spacetime does not. The universe cannot be foliated with such a coordinate system.

Gravitation can't be accurately described by inertial frames but require curvilinear coordinate systems. — Kenosha Kid

You can still foliate reasonable gravitation in 'bent' Minkowski spacetime, but not black holes. So for instance, a device measuring absolute time here on Earth would run apparently faster than one on the surface of Saturn due to the lower gravitational potential here on Earth. The same device on a ship with relativistic absolute speed would similarly appear to run faster (than the clock next to it) than it would if the ship had low peculiar velocity.

I don't get this. Why would they have to reach us? — Mr Bee

There's no requirement for light to reach any location from any other since there are very much cases where that does not occur. My point was that in an inertial frame, light can reach location X from Y given enough time, and thus such a model is not a model of our universe.

The light will never reach us because of cosmic expansion, so the fact that we don't see them doesn't mean they don't exist.

If there is a boundary to an inertial frame, then event outside that boundary do not exist in that frame. An inertial frame does support cosmic expansion, but it does not support acceleration of that expansion. So given no such acceleration, there would be no event horizon and light will eventually get from location X to Y given time. And even locally, an inertial frame cannot foliate the interior of black holes, so it fails twice.

I'm not sure about that. As far as I know, any spacetime that doesn't allow for closed timelike curves is open to being sliced into global hypersurfaces.

There are indeed ways to do it with a single black hole, but you must assume the black hole is at some kind of privileged location. So consider 3 events: A clock is dropped into a black hole. Event A is that clock 1 second (measured on that clock) after passing the event horizon. The black hole is big enough that it survives at least one second. The rock is dropped from a hovering location outside, which shines light down on the dropped clock. At some point the last light is emitted from this location that will catch up to the dropped clock before it hits the singularity. Event B is that hovering location 1 second after that last light goes out.
Event C is at the location of the former black hole after it has evaporated.
Yes, you can come up with various schemes to order these three events, but do any of those schemes order all of spacetime? OK, C occurs after B since it is in the future light cone of B. That's easy. Not so easy with event A.


I'm not suggesting retrocausality anywhere. Event A is not causally connected with either B or C, so no objective ordering scheme is going to produce a contradiction unless B is in A's future but C is in A's past.

I mean no disrespect — substantivalism

None perceived. I agree with your comment that there is a general aversion to solipsism among philosophers, and I was just pointing out that the aversion itself is a poor reason to reject any view. I personally find the view self contradictory, and reject it for that reason.

We see eye to eye on the geocentrism and anthropocentrism of view points as I also find metaphysics which make us highly centered in the grander scheme of things likewise also highly suspect.

Yes, but again, I identify that as a personal bias, and therefore not good grounds for rejection. Who knows, maybe the universe is made for us. That possibility must be considered, but positing such doesn't seem to explain anything better than more plausible views.

It's like a sorites problem of sorts to attempt to specify where you end and the greater worldly environment begins.

Where I end (spatially, not temporally) is an interesting problem. It seems to be a purely abstract thing. The guy in the sci-fi show straps a time travel device to his wrist and it takes him and his clothes and briefcase to some other time, but doesn't take the nearby shrubbery. How does the device know what's you and what's not? It's intuitive to us, but in trying to tell a device how to do it, it turns out it isn't obvious at all.
Where does a mountain stop? Most of them don't sit nicely on an otherwise flat surface that gives an obvious boundary delimiting mountain from the surface on which it rests.
All these things are part of exploration of identity, but not particularly important to relationalism, which cares not so much what one defines as a 'system' or not.

Yeah, solipsism really makes a philosopher run for the hills doesn't it. — substantivalism

Just because it's distasteful doesn't mean it's wrong. But I think there are serious logical problems with the solipsistic view, coupled with a personal bias against any sort of geocentrism, anthropocentrism, or any other view asserting us having a privileged status.

It was just the words being used by you such as 'me' that made me think you were taking a sort of idealist direction for you metaphysics but I was wrong there.

If I want to be formal, I had to find a definition of 'me' that didn't violate the law of identity, and it pretty much makes a hash of the way 'me' is used in everyday language. Language is littered with unstated premises, all of which I question (hence my user name), and most of which I cannot justify.

Under RQM, experiencing something has nothing to do with it being real. There simply needs to be a relation, especially a measurement. So the apple exists relative to the rock iff the rock measures the apple in some way. The rock having conscious experience of the apple has nothing to do with it. That kind of thinking leads to solipsism. Think Wigner interpretation, which many people hold without knowing it, but even Wigner himself abandoned it due to the solipsism thing.

I don't do polls, but I'm a relationist is probably far more ways than the one you describe.

Yes, time has no meaning without regular change to define it. Space has no meaning without at least three locations so that it can be meaningfully expressed that A is closer to B than is C. Without physical objects to anchor those locations, they're just abstract geometry to us. I consider our reality to be 'real' only because it relates directly to me, however I might care to define 'me'.

As for relational interpretations of special relativity, yes, I tend to favor RQM (Rovelli).

I think I read your post wrong, because upon re-reading it, I agree.

OK, then it works the same way that my thermostat turns on the heat in the winter despite the fact that it's warm in mid-May.

I'm very sorry that you seem totally incapable of understanding an alternate point of view. I cannot help you with that. Not asking you to change your beliefs, but you have no argument for or against one side or the other of any philosophical issue if you don't have even a rudimentary understanding of both points of view.

How does that work if your consciousness is not crawling up a worldline? — Luke

The same way my thermostat turns on the heat in the winter despite the fact that it's warm in mid-May. No need for a 'measurment' spotlight to crawl up the thermostat's worldline in order to allow it to function.

All that is left to account for is the motion of one's consciousness crawling upward along the worldline. — Luke

If that's how it works, it is still a form of presentism, with the consciousness (not part of the block) acting as the spotlight and defining a present. Dualism doesn't fit well at all with eternalism under which the entire worldline of a person is conscious. It would be rather absurd to say that the 1997 portion
of me is not conscious of the events of 1997.

Or alternatively we are stages which are located at a single instant and experience only that one instant of time while other counterparts experience the others. You know, cause experiencing every moment has the whole obviously wrong thing going on with us experiencing only one moment. — Mr Bee

Eternalism does not suggest that every state of a person along his worldline experiences every time in the worldline. That would be empirically quite different, wouldn't it?

If B-theorist eternalist are right, and we are beings that only experience one moment in time — ChatteringMonkey

we are only privy to one moment and so experience it as passage of time. — ChatteringMonkey

Ouch. Under eternalism, we beings are worldlines, and experience every moment along that worldline. So iff I define 'me' to be my worldline, then I am present at some event in 1995 and also 2021, and I experience those events and all others. There is none of this 'privy to one moment', which again smacks of a preferred moment.

The eternalist says that every point in time is equally real — ChatteringMonkey

I'd say 'has equal ontological status'. There's a difference to us non-realists.

Hate to butt in, however, these are all unproven theories? — Outlander

They're interpretations actually, despite all the literature referring to them as theories. No, neither interpretation can be falsified since they do not make distinct empirical predictions. All attempts to discredit one or the other proceed along logical grounds, not scientific ones.

If you perhaps fancy and have the time, could you explain in layman's terms. What differentiates eternalism from the moving spotlight theory?

The spotlight defines a present (preferred) moment, which makes it presentism, just like all the other variants described in the OP. Eternalism asserts the lack of a present,and doesn't seem to have so many variants.

Both have past, present, future.

Under eternalism, such words are only relations, like Earth, 1927 is in the future of Earth, 1925.

Please enlighten me as to the difference between Eternalism and the Moving Spotlight theory. — Luke

Moving spotlight (and pretty much the rest of your list) has a preferred moment. Eternalism does not.

You seem to be implying that temporal passage is possible under Eternalism? How so?

I implied no such thing. I said there is movement. I made no reference to temporal passage, which again is a term only meaningful to views that posit a preferred moment.

The mug moves probably by me carrying it there. That's probably not the answer for which you're looking, but I don't know what else you might be asking with that question.

I wanted to lay out my view of why Eternalism logically precludes motion. — Luke

I smell a begging argument coming on. You did this fairly large post, but then never actually get around to this point until the last couple sentences.

Some members of this site, including SophistiCat and @Douglas Alan have previously claimed that Eternalism does not preclude motion.

You can add me to that list. At noon, the mug has coffee in it. At 1pm the mug is in the dishwasher. How is that not motion of the mug?

In that case, my question is: when does motion occur according to Eternalism?

Somewhere between noon and 1 obviously (in my example). Every moment of it in fact, since at no time is any object actually stationary, what with Earth spinning and accelearting and all.

It cannot be at the present moment, because motion or temporal passage at the present moment implies the A-Theory, making it not Eternalism, but the Moving Spotlight theory instead. So, does Eternalist motion occur in the past or the future somehow?

There's the begging I smelled. Everything here are A-series references which assumes the conclusion you're trying to demonstrate.

Firstly, I don't know if communication per se is an indication of consciousness meant here as the existence of an inner life - what is it like to be something. — TheMadFool

I don't think there's anything 'being' me, so does that mean I shouldn't consider myself conscious?

The great Albert Einstein postulated that the velocity of light is constant at approximately 300,000 km/h. This one postulate and maybe a few more is the allegedly the foundation of his theory of relativity, a theory that has withstood many attempts at disproof. So far so good. — TheMadFool

It's 300,000 km/sec. It's a speed, not a velocity.
The postulate of SR is that that speed will be measured regardless the reference frame used. It doesn't actually posit that the speed actually IS frame invariant, just that it will be measured that way.

Consider 2 cars, A and B, moving on the same practically straight freeway.

1. Situation 1: A is moving at 20 km/h north and B is moving 60 km/h north. The relative velocity of B with respect to A is 60 - 20 = 40 km/h.

Per Einstein, no. Close, but not exactly 40. For instance, scale up the speed to say 0.2c and 0.6c, and the relative velocity of B with respect to A becomes 4/9 c, not 0.4c.

What then of the postulate that the relative velocity of light with respect to an object is "constant"? If I'm travelling in a spaceship with a given velocity, the relative velocity of light with respect to my spaceship will be 300,000 km/h. If I were then to alter my velocity, doesn't the velocity of light have to change accordingly so as to ensure that the relative velocity stays at a constant 300,000 km/h?

Unintuitive, but no. Light speed (not velocity) remains at c relative to anything. This works out if you use the velocity addition formula instead of straight addition like you're doing all through the OP.

Several of the questions presuppose the idea that minds can exist separated from the body. — Harry Hindu

Well yea, since the OP opens with: "If the mind is immaterial:"
The post asks to explore the viability of the alternate POV where there are two separate things, or where matter supervenes on mind. Given the wording of the post, I'd say more the former of those two.

I ask, "What is the point of a mind separated from a body?"

Or the point of a mind not consisting of a body?

All the above post seems to be about the mind being a function/process of the brain (or larger self), and sure, I am on that side of the fence, but I think the OP was asking about the opposite, where the body is a byproduct/purposeful-extension of the mind. The body seems to poorly implement such a purpose.

I've stayed out, and I find the arguments by unenlightened to be on point.
Nevertheless, the discussion seems to have turned to how materialism explains itself, and the original purpose of the OP seems to have been lost.

I think most of the relevant replies came from Wayfarer, but much of that was dropped. The Lusthaus quote was interesting but does not seem to address the question at hand. OK, it seems that it is a mistake to model the relationship as 'mind as an object'. We instead work with ideas and purpose, and the physical world is derivative from it. But then suppose it was my idea to take my purpose of needing an vehicle to animate my need for getting around and experiencing the world. Given that purpose, why would I imagine a vehicle with zero controls, that goes where it wants, when it wants. That's pretty useless for my purposes. I'd give it pedals and a steering wheel so that I could exert my will upon it. A physical being seems to have no pedals and such. It doesn't seem to be the product of the sort of purposeful ideas posited by this non-primary-material model.

What I'd like to say about that, is that both mind and matter are idealisations or abstractions. There is neither mind as a 'substance' (in the philosophical sense), nor matter per se because all matter has particular attributes and characteristics which define its type.

So whilst I agree that there is no 'immaterial object', I'm also inclined to believe that there are no 'purely material' objects either. — Wayfarer

I actually agree with this. On that point:

And then you've still got three ducks but now you've got a row as well. Assume the ducks are material. — unenlightened

If the row isn't 'new stuff', then neither are the ducks, being themselves just more arrangement of stuff that was already there. At what point is there actually stuff? It seems the scientists have never found it, and hence the unstable foundation of what is typically exemplified as 'materialism'.

Anyway, I was hoping to see more discussion on this original intent of this thread.

Near as I can tell, you mean something like 'coordinate time' when using the phrase 'relativistic time'. Coordinate time and physical (proper) time is the same thing for an inertial worldline with the time axis of the coordinate system aligned with said worldline.

Sure. But as you note later, proper time can be well-defined even in the absence of anything to mark its passage, and that is where I see a problem. You could have a relativistic spacetime with nothing else, and formally it would still have time of every description. But would it be physically meaningful? — SophistiCat

No, time without change is meaningless, as is say motion of an object in the absence of other objects. The words might as well be invisible pink unicorns.

Of course, here we run into the more general question of the nature of the physical law. Are laws ontologically prior to things and events that are subject to them? Do they describe potentialities (like what would happen if that empty spacetime did have something in it to demonstrate its relativistic properties)? Or do laws serve only to connect the dots, describe the regularities in our observations? In the latter case - and only in the latter case - it would be unjustified to talk about time in the absence of anything that is time-like. I think I lean towards the Humean regularity view.

I seem to be in the latter camp. Spacetime with nothing in it doesn't have relativistic properties.

The reason we came up with the theory of relativity in the first place was to give a better account of clock-based time (among other things). Without clocks what is the point of relativity?

Can there be time without clocks? Surely there are primitive people and animals with an awareness of time, but they also arguably have clocks, however inaccurate. If the speed of light was a lot slower, its properties could be more apparent and intuitive to primitive beings who may not have developed accurate measurements for it yet. Similarly, our intuitive perception of time as flowing is only there because that perception makes us more fit, not because time necessarily flows.

An empty, flat spacetime with a positive cosmological constant is an interesting case.

Meaningless. If it has stuff, I don't think it can be flat. If it were, an inertial frame could foliate the space, and it cannot.

relativistic time is not identical to physical time (the time that physical clocks measure) — SophistiCat

Actually, you never really defined what you mean by 'relativistic time'. You say physical time is that which clocks measure. I think physics would say that a clock measures proper time, a frame independent property of any timelike worldline. Clocks, not being confined to a single point, cannot be perfect, just like the exact length of a curving road is ambiguous because the road has nonzero width.
I digress. What do you mean by relativistic time? You said the two are usually the same except after heat death, but that doesn't tell me what you mean by the term, especially since a clock cannot exist in heat death conditions. It seems that time in general (both duration and direction) fade to meaninglessness along with most other physical concepts.

If I take a cube, and divide it in half, and then again, ect to infinity and then line them all up biggest to smallest, what is the smallest? ...
You might say "there is a limit". — Gregory

I might not. You're the one making the suggestion and then driving your own assertions to obvious nonsense conclusions.

So we have a huge paradox here.

Exactly so. So maybe try it without positing a last term in the infinite series.

Does the series go off into the physical horizon forever?

Physical now? A physical cube-shaped object has a finite number of particles in it and can only be divided so many times. There is a smallest part at the end of the sorted line and it has a color if you're going to abstractly assign colors to the even and odd ones.

Except that there is actually no motion according to Eternalism. I would imagine that it's much easier to explain why we perceive motion if there actually is motion than if there actually isn't. My point, again, is better expressed by Kristie Miller:

For the eternalist, the key challenge lies in explaining temporal phenomenology and in explaining the apparent directionality of time. There has been significant work in this area, but questions still remain: why do we have such a different relationship with the future than with the past: why is it that effects typically precede their causes when the laws of nature are symmetric: why do we remember the past, but not the future: why does the present seem to us to have a particularly salient quality that other moments lack; what are the cognitive apparatuses that underlie our experience of
temporality and how do they function to create temporal phenomenology; what is the evolutionary significance of the phenomenology of temporal flow and to what extent is the phenomenology of temporal flow essential for agency.
— Kristie Miller — Luke

I think I'm up to that explanation, which, from a physicalist point of view, can be explained through entropy and evolution, but almost nobody actually accepts physical monism deep down. I think I have but it was a multi-year struggle to shake off the biases put there by a very proficient liar.

So the story from the dualist POV (there is an (physical or spiritual, doesn't matter) identity 'I' that consistently experiences the life of physical body X. The analogy here is that physics is like a first person Harry Potter movie and the experiencer is the guy in the cinema. Eternalism is the same thing, except no cinema, no entity watching the show, and especially no projector.

Under presentism, the present is whatever frame is currently being projected. Normally the film runs front to back, but if it were run back to front, the experiencer in the cinema would notice the difference but Harry would not. The movie would end with the guy in the cinema knowing Harry's life story (the future) but Harry wouldn't even know that he's a wizard at the end. Harry obviously has different memories than the guy in the cinema. So the movie always runs forward because we'd be able to tell if it didn't.

Hence it being totally unintuitive to such a dualist to conceive of eternalism, which requires the lack of the experiencer (the definer of the present), and he interprets the description (the word 'static') as the experience of a stuck projector. The view is anything but that.

The eternalist view has no experiencer. It doesn't even have Harry (as an identity). It only has the individual frames in the film and one can talk about the experience of that frame, and yes, the experience of any given frame is one of motion of the passing car. One is forced to use B-series language to express what each frame experiences because there is no preferred frame defined by a projector, and A-series requires that preferred reference. By 'frame' here, I'm talking a frame of film (the local state of things at a particular time), and not relativity's reference frame.

The subjective flow of time is an illusion, illustrated empirically with the twins scenario in relativity. If people could detect the actual flow of time, then they'd be able to detect movement due to the subjective slowing of clocks when they're moving fast, whereas if it were an illusion, any traveler would notice no difference.
— noAxioms

It's unclear to me what the illusion is that you are referring to. What 'movement' is going undetected? What 'movement' would be detectable if "people could detect the actual flow of time"? — Luke

Not movement. I refer to the rate at which the present moment progresses into say a moment one second hence. No device measures this, and the subjective experience of a human is no exception to this. If there was, one could design an objective clock that would stay in sync with any other objective clock regardless of where it was or how much it has been accelerated around.

How to interpret data is subjective. The sole thing Einstein noticed was the observation that external motion changes the size and some of the rate of change within the object. That's it. — Gregory

This is totally wrong. The sole observation from which Einstein did his SR work was the apparent constant speed of light. From that, all the things above were predicted, not measured ahead of time.

Since he didn't do the experiments, he probably didn't even come up with that.

Indeed, he didn't do them himself.

Do you deny that it is unintuitive to be able to divide something finite a literal infinite amount of times? — Gregory

For one, 'infinite' is not an amount, and 'literal infinite' is no different than 'infinite'.

I would instead find it unintuitive to suggest that there would be a limit to it, a pair of non-identical points for which there is not a location between them. To assert otherwise is to assert that two non-equal numbers A and B can be found such that (A+B)/2 is equal to either A or B or both. You have weird intuition.

So I would say that a finite segment can be divided without limit, and yes, this is intuitive to me.

This is not true of any discreet system. For instance, in the domain of integers, the finite segment from 20 to 6051 can be divided, but only so many times. There is no integer between 21 and 22, and (21+22)/2 does not define a new integer, nor is the answer necessarily equal to either 21 or 22. It might be, depending on how the divide operator is defined for the discreet set in question.

According to the Kristie Miller article cited in the OP, the difference between Presentism and Etetnalism is not only their differing views on existence, but also their staticity/dynamism. — Luke

Miller writes this:

Thus eternalists endorse the following pair of theses:

Eternalist Ontological Thesis (EOT): Past, present, and future times and events exist.

Static Thesis (ST): The present does not move: which moment is the present moment does
not change. — Miller

Now either Miller has no understanding of the position, or she's talking about something completely different. The view denies the existence of a preferred moment called 'the present' and hence the ST part is nonsense. I've actually heard of such a view, which is presentism without the movement, but Miller doesn't seem to be talking about that since she correctly states that all events at all times exist equally, which is not true of a model with a present that stays put like that.

Anyway, I'd never accept these points as worded. The first isn't totally wrong, but past/present/future are all relations like < = >, and not objective states like negative, zero, and positive, and the wording makes it sound like the latter.

Then I take it you agree with all of the following:

Eternalists, then, hold that the world as a whole is static in two senses: which events
exist does not change, and there is no sense in which the present moves. — Luke

I'd say there is no 'the present' to do any moving. 'The present' would be just any event's self reference, and that, by definition, cannot move.

Eternalists accept what is known as the B-theory of time. This is the view that the
world is a static block of events ordered by the earlier than, later than, and simultaneous
with, relations. [1]

Also known in physics as 4-dimensional spacetime. 3D Space and time are separate under presentism.

Presentists endorse the A-theory, since they hold that it is a genuine feature of a
presentist world which moment is present, and that this fact changes over time so that
different moments are present at different times. To say that a view accepts the A-theory
is really to say that it endorses the dynamical thesis, and to say that it endorses the
B-theory is to say that it rejects the dynamical thesis.

I haven't seen the dynamical thesis, but this seems right.

Eternalism, on the other hand, is a static view that rejects temporal flow. Since it certainly
seems to many that there is temporal flow and change, this is a cost to eternalism.
At the least, the eternalist owes us an account of why it s

The subjective flow of time is an illusion, illustrated empirically with the twins scenario in relativity. If people could detect the actual flow of time, then they'd be able to detect movement due to the subjective slowing of clocks when they're moving fast, wheras if it were an illusion, any traveler would notice no difference. This of course isn't easy to test given the cost of the experiment, but it is there.
No, it isn't a proof of one view or the other, just a demonstration that the flow of time is a subjective illusion.

The odd numbers are eternally half the natural numbers, so there is no way at infinity they can be equal. — Gregory

I can think of at least 3 things very wrong with this statement. For one, what's the difference between X being half Y and X being eternally half Y? I mean, 5 is half of 10, and no matter how long I wait, 5 will remain half of 10, so I suppose it is eternally half of 10, but saying it that way doesn't make '5 is half 10' more true.

Let's see... There are 100 natural numbers with magnitude less than 100, and there are 100 odd numbers with magnitude less than 100, so that's not what you mean by this statement.

2nd try... Half of the natural number 36 is 18, which is not an odd number, so the odd numbers are not the halves of the natural numbers (whereas the integers would be half the even numbers, interpreted this way). So anyway, I don't think you meant this either, but I'm out of ideas.

And where is 'at infinity'? That's the treating it like a number that leads to such nonsense statements.
Surely Kant didn't make any such statements. Your intuitions lead to contradictions it seems.

If you can subdivide a segment endlessly, to eternity, it's finite and infinite.

What, exactly, is finite and infinite? Subdividing a finite segment doesn't affect its total length, so its finite length is unchanged. Also, what's the difference between 'endlessly' and 'endlessly, to eternity'? That's twice you've used that redundant modifier like it means something different than its absence.

It has to do with relativism because something can't be both finite and infinite at the same time with respect to the spatial, yet it is so. — Gregory

What is both finite and infinite? The length of AB is finite, and is never infinite. The number of points that can be described along AB is not finite, and is never finite, hence the existence of the bijuntion between that segment and any other. Neither is both finite and infinite.

Is this just another version of those threads that treat infinity like a number and then draw contradictions?

Anyway, I still don't know what this has to do with relativism, a view that seems to have nothing to say about the sort of mathematics you're discussing here.

As always, it's impossible to tell when someone claims to represent opponents' arguments made elsewhere, whether they are doing it accurately. — SophistiCat

Case in point:

it always amazes me that proponents of Eternalism so readily accept the static , motionless nature of their own temporal landscape. I'm no scientist, but much of science appears to be reliant on a dynamic world involving rates of change, momentum, spin, acceleration, velocity, etc. — Luke

I don't think the typical eternalist would assert a motionless landscape. An object is here at time zero, and over there at time 1, thus there is motion, spin, acceleration, velocity and all that.

Except that an arrow of time assumes a dynamic world? — Luke

The block view does not lack dynamics. The arrow of time kind of assumes that view since I don't see how you can draw an arrow in a direction that is posited not to exist.

Bijection has nothing to do with length. That just indicates that no line segment necessarily has more or less individual points than another. Length is not a count of points. Your fallacious thinking is in treating points in a line segment as a finite number.

1) Slant has no effect on the concept of bijection
2) Points are points, and don't have another shape.
3) whatever
4) Points don't have a size, so no.

I don't see how any of this is related to relativism

Are there other minds, or other bodies? — Harry Hindu

Only actual antirealist position I can think of is outright nihilism, and from what I understand of that, no, minds and bodies (not even ones own) exist.

I was referring to metaphysical antirealism which is the idea that "nothing exists outside the mind". — Michael McMahon

Since this topic was resurrected, I want to point out the contradiction of antirealism, defined in the OP as "denial of the existence of an objective reality" and the statement quoted here of "nothing exists except X" where X is the mind in this case. Those two definitions are mutually exclusive, the latter being a form of realism typically knows as idealism, which posits the reality of experiences.

I personally have found 'existence of an objective reality' to be a meaningless concept, and hence see no reason to assert it, which is a little different than actively denying it, so I'm not sure if I qualify as an antirealist.

I think the philosophical preference of a physicist, one who knows what he's talking about, typically has better grounding than a similar opinion from someone less familiar with the physics involved.

I for one know my physics enough to know that I've never seen an empirical falsification of either interpretation, and hence any logical argument must proceed from non-empirical assumptions. I've done that process and concluded what I conclude, but my stance keeps changing as I learn more, so the odds that my current favored view corresponding to 'the way that it actually is' (if there is such a thing) is pretty minimal.

But what's the relationship between the block universe (a physical model) and the metaphysical interpretation of time? — Echarmion

Sorry, but I consider them to be the same model, both metaphysical interpretations of space and time.

the answer to every philosophical question becomes "Because God Says". — Banno

Is it always 'because God says'? Take some moral rule X. Is X a rule because God says, or does God say because X is really wrong? The former denies objective morals. If God said one must light a live puppy on fire at least once a month, then that's the rule, but a rule relative to God, not objective.
The latter would be God forbidding lighting live puppies on fire because that's just wrong, implying there's a higher authority than God.
How is this resolved? I resolve this by denying both.