That there is a unique ordering of events with respect to time is something that is false because of the special theory of relativity. So time cannot be the succession of events. Within the same space of concepts, it could be seen as a succession of events.

What stops the following from being inferred from special relativity: there is no unique objective ordering of events with respect to time.

This is not the kind of thing we would expect to see if metaphysics and science had no interface - that they could not influence each other.

. And #2 should be "depending on the reference frame", not depending on particle motion. Motion

Reference frames can be attached to moving particles. This is what the Lorentz transform is for, and what the equivalence principle allows; considering motion of a particle to be at rest with respect to the reference frame of that particle's motion.

Presentism doesn't comment about how time works in SR. Presentism was around well over a century ago, and SR was not in any way suggested by it. Not sure when the term was coined, since the interpretation is far older than the name needed to distinguish it from alternative interpretations.

I agree that presentism doesn't imply SR. What I'm saying is that insofar as presentism claims that there is a unique objective ordering of events, it is contradicted by SR.

Changed key question sentence to be more precise:

What stops the following from being inferred from special relativity: there is no unique objective ordering of events with respect to time.

What stops the following from being inferred from special relativity: there is no unique objective ordering of events with respect to time. — fdrake

One can just simply treat one reference frame as being privileged over the others as the basis for absolute rest. Now, is it arbitrary to do so? Certainly, but there is nothing stopping us from doing so anyways and this does not conflict with SR as a scientific model.

I mentioned the LET earlier. It was a theory that was equivalent to SR empirically. It uses the same equations and makes the same predictions as SR so for the most part you cannot perform any experiments to distinguish the two. However, it included an ether, and it included an absolute frame which in turn means a unique objective ordering of events.

One can just simply treat one reference frame as being privileged over the others as the basis for absolute rest. Now, is it arbitrary to do so? Certainly, but there is nothing stopping us from doing so anyways and this does not conflict with SR as a scientific model.

The arbitrariness of the reference frame used for the definition of universal time removes the possibility of interpreting its time variable as a universal time. All reference frames have just as good a candidate for universal time. That is to say: they all suck for it.

That there is a unique ordering of events with respect to time is something that is false because of the special theory of relativity. — fdrake

Totally agree. SR says physics is unchanged in all these different orderings. There is not a unique ordering of my children either. I could order them by height.

What stops the following from being inferred from special relativity: there is no objective ordering of events.

It doesn't follow. What follows is that if it existed, it would be undetectable. There is no premise of its nonexistence. I don't like its existence because it is a needless addition that explains nothing.

Reference frames can be attached to moving particles.

Yes, but any frame can be attached to any particle. It is moving in all but one of them. Yes, some object is typically used as a specification of a frame. There is almost no other way to do it. So we all know what we mean by "frame of the train platform" even though the platform exists just fine in the frame of the train. But I think it is sloppy to say clock C dilates relative to object R. It should more correctly say it dilates in the frame of object R, or even more anal, in the frame in which object R is at rest.

I agree that presentism doesn't imply SR. What I'm saying is that insofar as presentism claims that there is a unique objective ordering of events, it is contradicted by SR.

It says there is a unique objective ordering, not a unique ordering. None of the SR orderings are objective.

What stops the following from being inferred from special relativity: there is no unique objective ordering of events with respect to time. — fdrake

SR doesn't talk about objective orderings, so I don't see how the above can be inferred.

The arbitrariness of the reference frame used for the definition of universal time removes the possibility of interpreting its time variable as a universal time. All reference frames have just as good a candidate for universal time. That is to say: they all suck for it. — fdrake

Arbitrary, yes, but again, not impossible. There is a difference between the two. To be impossible means that it is in some sense logically contradictory, that there is some conceptual problem that makes it simply not work. I do not see that here.

If the presentist wants to say that there is a unique ordering of events that cannot be detected, then the burden is on them to give reasons to supporting it, but it is an open option for them.

It says there is a unique objective ordering, not a unique ordering. None of the SR orderings are objective.

Ok. What differentiates an objective ordering from one in obtaining in a reference frame in special relativity?

Arbitrary, yes, but again, not impossible. There is a difference between the two. To be impossible means that it is in some sense logically contradictory. I do not see that here.

Logical possibility isn't a particularly good criterion for forming metaphysical postulates. Any metaphysics is likely to be logically possible. Any physical theory is likely to be logically possible. We need a finer net to capture what is relevant.

What matters is what SR does to the idea of there being a unique ordering of events (time as the succession)- it shows that there is none. If there is no unique ordering, there can be no unique objective ordering. The class of orderings that agree with all other orderings is empty, so none can be objective.

Or alternatively, they're all objective (since there are none that are not objective).

Neither of these interpretations of the consequences of SR is consistent with the idea that there is a unique objective ordering of events.

All reference frames have just as good a candidate for universal time. That is to say: they all suck for it. — fdrake

Yes they do. No inertial frame gets near covering the universe, so if there is an objective ordering, it cannot be an inertial frame. SR doesn't say that, but GR does.

Take planet Zog 60 BLY away. We don't exist in its frame and they don't exist in ours. Some other non-inertial ordering of events is needed to cover such places, and it need not even be smooth. Perhaps it advances only over there for a while and later on advances for us, making the the boundary a wobbly thing that makes uneven progress. So long as the boundary doesn't get so advanced one place that events happen before their causes, there's no contradiction. Light cones limit the maximum distortion of the boundary.

Ok. What differentiates an objective ordering from one in obtaining in a reference frame in special relativity? — fdrake

It's an ontological assertion. Presentism posits not just a real ordering, but also a real boundary between past and future events. Just the objective ordering is not enough. Presentism adds a boundary that traverses the events in objective order.

SR make no ontological assertions. It just says that physics will be observed to work identically in any frame.

Logical possibility isn't a particularly good criterion for forming metaphysical postulates. Any metaphysics is likely to be logically possible. Any physical theory is likely to be logically possible. We need a finer net to capture what is relevant. — fdrake

It is a good criterion for determining what is impossible and what is possible. If we are going to say that something "can't happen", or that something is "impossible" then it means that it can never be the case regardless of any scenario. Otherwise we shouldn't be using that sort of language.

What matters is what SR does to the idea of there being a unique ordering of events (time as the succession)- it shows that there is none. If there is no unique ordering, there can be no unique objective ordering. The class of orderings that agree with all other orderings is empty, so none can be objective. — fdrake

I can agree that it suggests that there is none, but I will withhold from using strong words like "impossible" here. I believe there is reason from relativity that supports the rejection of presentism, but I think it is a common misconception that relativity is completely incompatible with it which is why I feel the need to emphasize that point.

So long as the boundary doesn't get so advanced one place that events happen before their causes, there's no contradiction. Light cones limit the maximum distortion of the boundary.

This is a fun way to smuggle in an objective ordering without justification. Why would it be contradictory for an event to happen before its cause as viewed from some reference frame? Contained within the series of cause and effect is the universal succession, only this time of equivalence classes of causes occurring before a given ordinate in the series.

The construction is something like:
$\{ \text{events which can be causes after } t \} = x_t = \{\text{events occurring before }t\}$

Inertial frames are inappropriate to apply to regions of space with non-negligible intrinsic curvature (derived from energy/momentum density). Nevertheless, away from these masses and near the speed of light, GR reduces to SR - the metric tensor tends to the Minkowski tensor.

I can agree that it suggests that there is none, but I will withhold from using strong words like "impossible" here. I believe there is reason from relativity that supports the rejection of presentism, but I think it is a common misconception that relativity is completely incompatible with it.

Great, then the conceptual work is done. It's more justified to believe that SR suggests there can be no unique objective ordering of events than not.

Great, then the conceptual work is done. It's more justified to believe that SR suggests there can be no unique objective ordering of events than not. — fdrake

Sure, I can follow that. Would you likewise agree with me that SR as a scientific theory can be reconciled with a unique objective ordering of events?

If something supplanted the verified predictions of SR that nevertheless had such an ordering, I would believe it. But I think that SR does a lot to undermine the existence of a unique total ordering of events - so I doubt that a conceptual manoeuvre which introduces a universal time without caveats would be a justified one.

Earlier in the thread, I pointed out that for speeds not close to the speed of light, SR reconciles with usual relative motion. The Lorentz transform tends to the identity transform and proper time tends to time. I think this suggests that any naturalistic metaphysics currently has to have a procedure for regionalisation: that is different regimes of phenomena should be allowed to have different constitutive dynamics.

This is a fun way to smuggle in an objective ordering without justification. Why would it be contradictory for an event to happen before its cause as viewed from some reference frame? Contained within the series of cause and effect is the universal succession, only this time of equivalence classes of causes occurring before a given ordinate in the series. — fdrake

Had a hard time following this.
One property of relativity is that from any given event X, there is a fixed set of events in its direct past and future causal cones, and this set is frame independent. OK, the frame of Zog puts 2017 in my future, but I don't exist in that frame, so no contradiction.

What stops the following from being inferred from special relativity: there is no unique objective ordering of events with respect to time. — fdrake

You seem to be overlooking a basic problem which quantum mechanics exposes to us. This is that the nature of "an event" is, inherently ambiguous. From one frame of reference "an event" is a completely different type of thing compared to "an event" from a different frame of reference. This makes comparing the "ordering of events with respect to time", from one frame of reference to another fundamentally incoherent, or unintelligible, because you are not comparing the same thing.

This is the issue which length contraction, time dilation, etc. demonstrates to us. The very same object (event) being observed from different frames of reference (different perspectives), is significantly different. According to your rule #2, we cannot construe this as a measurement problem, the "same event" may be substantially different from a different perspective, as evidenced by wave-particle duality. The transformation formulas do not adequately deal with this problem, because they treat it as a different ordering of the same events (as you represent), instead of a fundamental difference in the nature of "an event".

If something supplanted the verified predictions of SR that nevertheless had such an ordering, I would believe it. — fdrake

Then that would be a different scientific theory entirely. I was not talking about that.

But I think that SR does a lot to undermine the existence of a unique total ordering of events - so I doubt that a conceptual manoeuvre which introduces a universal time without caveats would be a justified one. — fdrake

I am not asking about whether it is justified. I believe we have already agreed upon the costs of an undetectable absolute ordering associated with a universal time. I am merely talking about its possibility, the ability to reconcile the idea of a universal time with SR. Unless you think that there is a logical contradiction in the idea, then you should not object to its being possible. That is all I am asking here.

So that fdrake's preposterous ontology does not become codified in this thread:

1) There is a unique ordering of events in experienced time, the time of duration. This is the time in which Poor Tim died by the simultaneous closing of the electrical circuit.

2) There is a measurement problem which science can't solve because it cannot precisely synchronize. clocks. This is all that STR addresses. STR has no ontology. It's a problem with measurement synchronization. Sci fi lovers just made up this stuff about going backwards in time and stuff.

As long as people look at a mathematical symbol T and consider that real time, because someone called clock time real time, there will be instant confusion and lots of sci books. The ordering of events in my life is the real ordering of events in my existence however it might be measured by someone else, and sometimes I'll be killed by these ordering of events which are really happening. They aren't some measurement equations. Events really happen but it is difficult if not impossible to synchronize clocks as to measure when they happened.

One property of relativity is that from any given event X, there is a fixed set of events in its direct past and future causal cones, and this set is frame independent. OK, the frame of Zog puts 2017 in my future, but I don't exist in that frame, so no contradiction.

Because this is interesting, let's have some maths for it.

The quantity 'proper time' is invariant between inertial reference frames. Assuming 1 dimensional linear motion, this quantity is:

$d\tau^2 = dt^2 - \frac{dx^2}{c^2}$

If $d\tau^2\gt0$ between two events occurring at $t_1$ and $t_2$, then the separation between the events is called time-like. This occurs, roughly, when the temporal separation between two events is greater than their spatial separation.

Assume these two events (A and B at $t_1$ and $t_2$ have time-like separation, then:

$d \tau ^2 = (t_1-t_2)^2 - \frac{(x_1 - x_2)^2}{c^2}\gt0$
which gives
$c^2 (t_1 - t_2)^2 \gt (x_1 - x_2)^2$
if we wanted to find a frame of reference in which $t_2$ occurred before $t_1$, reversing the inequality here, it would need squared average velocity:

$c^2 \lt \frac{(x_1 - x_2)^2}{(t_1 - t_2)^2}$

which can't happen, since it would be higher than $c^2$. So, if two events have a time-like separation, there does not exist an inertial frame which has their ordering reversed. Another consequence is that all events occur simultaneously for light. The orders can reverse for space like intervals - when $d\tau^2$ is negative.

Thus, two events can be said to be in causal contact if they are in time-like separation, but not in space-like separation. And two observers using the same reference frame, regardless of what it is, will agree on the ordering of events. Since the Earth is small with respect to the distance light could have travelled since Earth's inception, and since the movements of humans are nowhere near the speed of light, special relativity is consistent with the ordering of events as considered from our Earthly perspective. But not necessarily about exactly when events occurred - this is still velocity dependent.

From the perspective of light, there is no duration. From other perspectives, there is duration. A very distant observer moving in a particular way could see our history with some events in a different order. Why should the universe be seen from the perspective of a human, and not a photon or a distant observer (with space-like separation)?

Consistently off topic nonsense.

Sure, logically possible. I ain't believing in it though.

Consistently off topic nonsense. — fdrake

It's not off topic. Do you recognize the fundamental difference, which is exposed by the length contraction and time dilation implied by relativity theory, between the nature of "an event", at speeds near and at light speed, and "an event" at speeds which we observe with our eyes?

If so, then do you see that this makes your talk of a "unique objective ordering of events", fundamentally incoherent, because there is no way to say that an observed event from distinct frames of reference is "the same event".

Sorry, but the equations did not quote properly.

Because this is interesting, let's have some maths for it.

The quantity 'proper time' is invariant between inertial reference frames.

If dτ2>0 between two events occurring at t1 and t2, then the separation between the events is called time-like. This occurs, roughly, when the temporal separation between two events is greater than their spatial separation.

if we wanted to find a frame of reference in which t2 occurred before t1, reversing the inequality here, it would need squared average velocity which can't happen, since it would be higher than c2. So, if two events have a time-like separation, there does not exist an inertial frame which has their ordering reversed. — fdrake

I follow what you wrote and mostly agree. There doesn't exist a valid frame which covers t1 and t2, but Zog is moving (proper distance increasing) by over 4c, which is not a valid velocity, so hence I say Zog doesn't exist in our frame. But it exists in the universe as does its frame, so I hesitate to assert that this frame that is invalid for t1 is nonexistent. Just invalid for t1. Yes, t2 is ordered before t1, and in fact both predate the big bang. This is what happens when you consider an object or frame in the context of an event for which it is invalid.

Another consequence is that all events occur simultaneously for light. The orders can reverse for space like intervals - when dτ2 is negative.

It is meaningless (but not invalid) to reverse the order of simultaneous events. Either way they both happen at once.

Thus, two events can be said to be in causal contact if they are in time-like separation, but not in space-like separation.

Right. And any pair of events in causal contact can be said to be at the same point in space in some frame, and any pair outside causal contact can be said to be simultaneous events in some frames.

From the perspective of light, there is no duration. From other perspectives, there is duration.

Local spacetime collapses to a singularity at light speed. Not sure if it is valid to reference that as a 'perspective'. It is not a valid inertial frame.

A very distant observer moving in a particular way could see our history with some events in a different order. Why should the universe be seen from the perspective of a human, and not a photon or a distant observer (with space-like separation)?

Oooh.... Example please, because this seems totally implausible. What is 'our history'? Sure, if we colonize distant stars, event ordering starts getting ambiguous, but it doesn't take a distant observer to notice that. So presume our history is confined to this planet, and we're not just talking about milisecond differences that it takes for light to traverse the diameter of the planet. Sure, events on opposite sides of the planet within a milisecond of each other have frame dependent ordering, but again, it doesn't take a distant observer to notice that.

Sure, logically possible. I ain't believing in it though. — fdrake

Your thread seems to have been trying to demonstrate that relativity renders presentism a contradiction. Sure, I don't believe it either, but I don't consider it to be a proven thing. I just try not to be in the habit of believing in things that add to a model without explaining any of it better.

I actually started the thread without many ideas of what SR or GR imply about philosophical positions (presentism, A-B-C series etc) regarding space and time. Someone (was it you?) brought up the idea that presentism implies a unique order of events, and I tried to argue that SR suggests very strongly that there isn't one (without restricting the application of SR). My intention for the thread was to discuss limitations that SR and GR place on philosophical interpretations of space/time and motion.

Even if it's granted that SR and GR don't really provide a theory of time, they will still place some constraints on what a sensible ontology of space, time and motion could look like. My hope for the thread was to tease out the constraints.

Oooh.... Example please, because this seems totally implausible. What is 'our history'? Sure, if we colonize distant stars, event ordering starts getting ambiguous, but it doesn't take a distant observer to notice that. So presume our history is confined to this planet, and we're not just talking about milisecond differences that it takes for light to traverse the diameter of the planet. Sure, events on opposite sides of the planet within a milisecond of each other have frame dependent ordering, but again, it doesn't take a distant observer to notice that.

Events have to have a space-like interval between them in order for there to exist a reference frame in which the order is mucked with. This can be taken to imply that the possible reshuffling of indices has no physical meaning since to be in causal contact would require that events can't occur before their causes, and this is only guaranteed if two events have a time-like interval between them. But regardless, say event 1 occurs at $t_1$ and event 2 occurs at $t_2$. Also assume that $t_1$ and $t_2$ have a space-like distance between them. That is:

$d\tau^2 = dt^2 - \frac{dx^2}{c^2} \lt 0$ for 1D motion.

It's a mathematician's proof, but $dt$ can be freely set to 0 and you still get a valid reference frame, that is $(t_1 \geq t_2)$. Section 4.6 here discusses space-like intervals and this property. Points that satisfy this property must be outside the light-cone of a particle in a reference frame.

If we're restricted to consider things which are useful for predictions (the weak sense of physical models), then I'd say at this point it's arguably useless for considering space-like or light-like intervals between things since they don't preserve the order of cause and effect in a temporal series. What's interesting ontologically though, is if there is a reason besides convenience and satisfaction of pre-theoretic intuitions for restricting 'valid reference frames for comparing events' to events that have time-like intervals between them. I'm leaning no on this. Prosaically, the perspective of a photon or of a (pathologically) distant motion is just as valid a reference frame sub specie aeternitatis as ones which preserve our causal orders.

So what's needed is a good account of causal connection and its relationship to space-time, a way to truncate the phenomena of relativity's relevance. I think this would begin with thinking of the light-cone as a partition of space-time between causally connected components; and would be aided by thinking of $d\tau^2$ as a quantity which can represent the possibility of causal connection between events.

(2) The ramifications of both relativity theories, like length contraction, time dilation, and the equivalence of mass and curvature distortions should not be treated as arising from 'deficiencies in measurement'. — fdrake

Yes, that seems to be a reasonable requirement in order to prevent the discussion from going off the rails. I have read this whole thread obliquely and I find myself mostly in agreement with you, with noAxioms and with Mr Bee. It's not so very often that there occurs a discussion about Einstein's theory of relativity on a philosophy forum and that some of the participants have a reasonably good understanding of its mathematical inner workings. So, that's cool. It means also that there is, at least, some scientific footing for further inquiring about the theory's implications for the metaphysics of time.

I had planned to first read the paper by Stephen E. Robbins (which fdrake linked to in his original post) before jumping into the discussion. The abstract seemed intriguing and promising enough, and I was quite happy to see J. J. Gibson being quoted in the epigraph. However, I leafed through the main text rapidly and was struck by the author's very crude misunderstanding of the infamous twin-paradox. The author displays a parallel misunderstanding of the barn-pole paradox. Robbins seems not even to have noticed or gasped how the relativity of simultaneity can be (and usually is) appealed to for neatly resolving those merely apparent paradoxes. He thus seems to believe that the asymmetrical ageing of the twins somehow violates the "abstract reciprocity of reference systems"(*). That's fairly disappointing because this is the very specific misunderstanding of the theory has been the linchpin for its rejection by many "skeptics" (very few of them learned physicists) over the last 100 years or so.

This crude mistake also appears to have led Robbins to a rather confused conception of what it is that it might mean for a duration to be "ontologically real" rather than its being merely perspectival or relative to a reference frame. Proper time is a quantity that can be integrated along the world-line of a material object and it is invariant according to both the special and the general theories of relativity. Robbins seems to be missing this point entirely. And, as a result, through construing the question of the ontology of time as a question regarding "elapsed times", which conflates the two distinct although related notions of (1) proper time (which is ascribed to a segment of a world-line, along which a real material clock might be tied) and (2) the time-coordinate interval between two events (which may have either a space-like or a time-like separation), he gets confused. Owing to this confusion Robbins seemingly misses the opportunity of even so much as correctly framing his interesting philosophical questions (which are of interest to StreetlightX, to myself and to others).

(*) Note: At some point, because Robbins can't grapple with what he sees as the paradoxical implications of his own ill-defined principle of "abstract reciprocity of reference systems", he is led to postulate that the augmentation of the half-lives of mesons travelling at high speed though the earth atmosphere might be the result of some sort of electromagnetic effects on nuclear processes. This sort of hypothesis lines up with Lorentz' own early postulation of physical ("ontologically real", Robbins might say) effects on material clocks and rulers that would be ascribable to the "luminiferous aether wind" and that would account for the negative results of the Michelson-Morley experiment, the apparent invariance of the speed of light, etc.

The author displays a parallel misunderstanding of the barn-pole paradox. — Pierre-Normand

I had to look that up, and the flaw in the criticism was trivial. The barn and pole are treated as simultaneous objects instead of events. Using the latter, there is no paradox.

This crude mistake also appears to have led Robbins to a rather confused conception of what it is that it might mean for a duration to be "ontologically real" rather than its being merely perspectival or relative to a reference frame. — Pierre-Normand

Here is perhaps the disconnect between what fdrake has been addressing and what I've been denying, which is the ontological status of duration, or of time. So I think some clarification is needed, because I think the wording you put here is the more standard one.
When people ask me if they think time is real, I don't know how to answer since I don't associate ontologly with my understanding. But apparently it is in contrast to 'prespectival', and no, I don't think it is real in that sense.

The way I have been using it is my sense of presentism, that there exist a subset of events that are in 'the present', that this 'the present' is a boundary between nonexistent past determined events (how could they be determined if they don't exist??), and future undetermined ones. This view seems more ontological to me (only present events are real, the rest are not), but it proposes zero falsification tests (if worded well), and thus is in no way refuted by any empirical theory like relativity or any other.
On the other hand is the assertion that humans experience of duration is unique in experiencing not physical processes like clocks or anything else physical, but of the advancement of this "ontologically real" present. This would elevate it to an empirical claim, and despite being untested, would seem to be complete nonsense. It means that in the twins experiment, the traveling twin at sufficiently high velocity would die (of suffocation perhaps) because his physical processes would occur faster or slower than he could consciously tend to them. The view also tends to put Earth at the center of the universe, but that is not necessary. I find any view that necessitates heliocentrism to be one equating the universe to be all about us.

I had to look that up, and the flaw in the criticism was trivial. The barn and pole are treated as simultaneous objects instead of events. Using the latter, there is no paradox. — noAxioms

Yes, indeed, one ought to focus on events. To say of the moving pole that, at one moment, as measured in the reference frame where the barn is at rest, that it fits entirely (and exactly) within the barn, just is to make a (relative) claim regarding the simultaneity of the two events defined by the instantaneous spatial coincidences of the tail and head the pole with the back and front of the barn, respectively. In the inertial frame where the pole is at rest, however, those selfsame two events don't occur simultaneously. The pole is longer than the barn, and the moment when the back of the moving barn reaches the tip of the stationary pole occurs before the front of the barn reaches the tail of the pole.

ote: At some point, because Robbins can't grapple with what he sees as the paradoxical implications of his own ill-defined principle of "abstract reciprocity of reference systems", — Pierre-Normand

Wrong. Robbins got it spot on and you are confused about what he has written. But this thread seems to be reserved for only those who agree with fdrake while disagreeing with what he is saying.

Here is perhaps the disconnect between what fdrake has been addressing and what I've been denying, which is the ontological status of duration, or of time. So I think some clarification is needed, because I think the wording you put here is the more standard one.
When people ask me if they think time is real, I don't know how to answer since I don't associate ontologly with my understanding. But apparently it is in contrast to 'prespectival', and no, I don't think it is real in that sense. — noAxioms

Proper time isn't perspectival, though, is it? This is the idea of the absolute duration of a localized process, as measured by a standard clock that travels alongside the process.

The times when events occur (or coordinate times), as referred to a specific inertial reference frame, for instance, are perspectival in the sense that they are relative to the choice one makes among many possible inertial reference frames. But there is another sense in which time is perspectival, and this is the sense in which the separation between the three classes of events that are past, present and future is relative to the locally and spatially singular perspective on an agent. And this ties up with the idea of one's power of intervention. This sense of temporal perspectivality is quite independent from whatever the special theory of relativity has to say about time, empirically, except for the manner in which it defines the three regions of the agent-centered light-cone at each instant: limiting possible intervention, or unintended causal influence, to the events located within the "future" region of the light-cone. The two other regions of the agent-centered light-cone can be assimilated to this agent's perspectival past, for all practical purpose, since they comprise all the events that this agent has no causal power influence anymore.

Still, the physical duration of processes seem to me not to be perspectival in any one of the two senses distinguished above (i.e. "frame-perspectical" or "agent-perspectival"). So, that would be one rather trivial sense in which time can be said to be "ontologically real". But this consideration is blind to the metaphysical significance of the distinction between past, present and future, which is better addressed with Kantian considerations on the relation between concept and intuition, or inquiries about the phenomenology of situated agency.