Ontological Implications of Relativity
was going to respond to this with a personal message to @StreetlightX, but the length of the response got out of control. I'm going to keep posting notes on this paper, if anyone's interested feel free to engage, BUT: I won't engage with anyone who does not abide by the following rules.
(1) Special and general relativity should be treated as having excellent evidence for them.
(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'.
(3) Despite (2), differences between time in special relativity and phenomenological/experiential time are welcomed so long as they are not treated as deficiencies in measurement.
Feel free to ignore these rules, but try not to in this thread. There's already an ongoing thread with less restricted discussion. So, the 'conceptual position' of this thread is assuming the truth of special relativity and trying to tease out its ontological implications.
Here are my notes so far on the paper:
This isn't true, any observed in an inertial reference frame can declare himself at rest and something else moving if they are both in inertial frames - that is have constant velocity with respect to each other but when there is (intrinsic) curvature or acceleration, they cannot. Interestingly, curvature and acceleration is the 'equivalence principle' manifesting in GR - it is how it accounts for gravitational fields, rather than in terms of uniform velocities being indexed to a coordinate system.
An example of intrinsic curvature occurs with objects being pulled towards planets - since different parts of the object, along their instantaneous vertical (perpendicular to orbit) axis they feel tidal forces due to differences in the gravitational field over their mass. IE, If someone was in orbit, feet towards the earth, they might feel that they are being stretched along the groin-head axis. Also note, space-time in special relativity has no intrinsic curvature.
However, acceleration which is not due to the intrinsic curvature of space-time (mass/gravity) can be included in special relativity, and of course there are corresponding transformations. This has derivations (for accelerated motion in straight lines) requiring only elementary calculus
This is also somewhat present in general relativity. Things like cosmic inflation - the expansion of distances neighbouring points in space - are modelled by making the space-time metric (metrics assign distances to pairs of points in space-time) a function of the time variable. This means that in GR the 'evolution of the universe' can be spoken of with respect to a universal time - which is exactly what they do in cosmology.
This is true, but 'observer' is equivalent to 'coordinate system attached to a point' in the theory. It's also somewhat irrelevant because when something changes position it moves with respect to something else. This is true even in Newtonian physics. Essentially the difference between 'I drove today' vs 'I drove from home to work today'. Motion was already understood as relative motion since Galileo.
This is one of those arguments where the expected conclusion can be considered a framing effect of the question, rather than a genuine effect of its constituents. We're used to thinking of ageing in a universal time. Let's analyse it in a manner that doesn't involve the re-synchronisation of clocks.
Scenario 1
Call time for the earth twin t and time for the travelling twin T, the travelling twin is travelling linearly away from the ageing one with constant speed v. What's the derivative of T with respect to t? Treating D as also the derivative with respect to time which appears as an under script on the LHS of the equation.
[math]T=\gamma (t-\frac{vx}{c^2})[/math]
[math]\implies \frac{dT}{dt} = \gamma(1-(\frac{vDx+xDv}{c^2})[/math]
[math]\implies \frac{dT}{dt} = \gamma(1-\frac{v^2}{c^2})=\gamma \frac{c^2-v^2}{c^2}=k[/math]
and now the derivative of T with respect to t:
[math]\frac{dt}{dT}=(1/\gamma) \frac{c^2}{v^2 - c^2}=1/k[/math]
since in this scenario Dx = v
Scenario 2
Now, what if we consider the earth twin ( t ) as moving with velocity -v away from the travelling twin ( T )?
[math]t=\gamma (T+\frac{vx}{c^2})[/math]
[math]\implies \frac{dt}{dT} = \gamma(1-\frac{v^2}{c^2})=k[/math]
and
[math]\frac{dT}{dt}=\frac{1}{\gamma(1-\frac{v^2}{c^2})}=1/k[/math]
In this scenario Dx = -v
So you can see the two situations are equivalent in terms of time scaling for both observers. Guy missed a tricky minus times a minus. The first times -v flips the + sign, then when -v occurs as Dx it flips the minus again.
Equivalent motions produce the same derivatives with respect to the time in the moving reference frame.
I won't deny time dilation and length contraction are weird though, and if a physicist attempts to think of them as measurement illusions, they're not doing it right.
With regard to the block-universe that this thing seems to imply. The block universe is essentially conceiving of the vector space (x,y,z,t) as a space-time manifold - as if when all components were free to vary along their ranges, we have a continuous set of snapshots of all events. This isn't implied, what is implied is that for a given equation of relativistic motion there is a space-time 'block' corresponding to its trajectory over space through time. It would be odd to consider space time an invariant block when the things within it can distort all of its motions with their particular properties.
I thought you would've quite liked this, special relativity produces a multiplicity of blocks and the Lorentz transform renders the blocks reconcilable. Which is to say, with a more ontological framing, the unfolding of the universe is relative to the trajectories of its localising elements - the differentials of movements - but the category of relativistic motion nevertheless has a clearly demarcated set of potentials.
Agreed. Insofar as this article is criticising lazy metaphysics from physicists, I appreciate it. Insofar as it's shitting on relativity, I don't. But, the 'shitting on relativity' through thought experiments does show the need for lots of ontological work. Hence this thread.
(1) Special and general relativity should be treated as having excellent evidence for them.
(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'.
(3) Despite (2), differences between time in special relativity and phenomenological/experiential time are welcomed so long as they are not treated as deficiencies in measurement.
Feel free to ignore these rules, but try not to in this thread. There's already an ongoing thread with less restricted discussion. So, the 'conceptual position' of this thread is assuming the truth of special relativity and trying to tease out its ontological implications.
Here are my notes so far on the paper:
(the equivalence principle) implies that any observer has the
right to declare himself at rest and all others in motion with respect to him. There is no
way to tell who is right. The second postulate is the invariance of the velocity of light in
all inertial frames...'It implies that any observer has the right to declare himself at rest'
This isn't true, any observed in an inertial reference frame can declare himself at rest and something else moving if they are both in inertial frames - that is have constant velocity with respect to each other but when there is (intrinsic) curvature or acceleration, they cannot. Interestingly, curvature and acceleration is the 'equivalence principle' manifesting in GR - it is how it accounts for gravitational fields, rather than in terms of uniform velocities being indexed to a coordinate system.
An example of intrinsic curvature occurs with objects being pulled towards planets - since different parts of the object, along their instantaneous vertical (perpendicular to orbit) axis they feel tidal forces due to differences in the gravitational field over their mass. IE, If someone was in orbit, feet towards the earth, they might feel that they are being stretched along the groin-head axis. Also note, space-time in special relativity has no intrinsic curvature.
However, acceleration which is not due to the intrinsic curvature of space-time (mass/gravity) can be included in special relativity, and of course there are corresponding transformations. This has derivations (for accelerated motion in straight lines) requiring only elementary calculus
"What is the classical conception of time? The advance of time traditionally involved
the vision of the “time-growth” of the universe along some universally defined plane we
call the "universal present."
This is also somewhat present in general relativity. Things like cosmic inflation - the expansion of distances neighbouring points in space - are modelled by making the space-time metric (metrics assign distances to pairs of points in space-time) a function of the time variable. This means that in GR the 'evolution of the universe' can be spoken of with respect to a universal time - which is exactly what they do in cosmology.
Indeed, Einstein wished that his theory had been named “Invariantentheorie,” rather than relativity (cf. Horton, 2000). In special relativity, the Lorentz transformations have no meaning with respect to just one observer. There is no invariance with just one observer.
This is true, but 'observer' is equivalent to 'coordinate system attached to a point' in the theory. It's also somewhat irrelevant because when something changes position it moves with respect to something else. This is true even in Newtonian physics. Essentially the difference between 'I drove today' vs 'I drove from home to work today'. Motion was already understood as relative motion since Galileo.
Only the abstract reciprocity of reference systems is important. So now it is
the X twin who ages less. So for whom is the aging less? X or Y? Has time really
changed? Or should we just be saying that aging period too is a space-time invariant,
just as the length contraction?
This is one of those arguments where the expected conclusion can be considered a framing effect of the question, rather than a genuine effect of its constituents. We're used to thinking of ageing in a universal time. Let's analyse it in a manner that doesn't involve the re-synchronisation of clocks.
Scenario 1
Call time for the earth twin t and time for the travelling twin T, the travelling twin is travelling linearly away from the ageing one with constant speed v. What's the derivative of T with respect to t? Treating D as also the derivative with respect to time which appears as an under script on the LHS of the equation.
[math]T=\gamma (t-\frac{vx}{c^2})[/math]
[math]\implies \frac{dT}{dt} = \gamma(1-(\frac{vDx+xDv}{c^2})[/math]
[math]\implies \frac{dT}{dt} = \gamma(1-\frac{v^2}{c^2})=\gamma \frac{c^2-v^2}{c^2}=k[/math]
and now the derivative of T with respect to t:
[math]\frac{dt}{dT}=(1/\gamma) \frac{c^2}{v^2 - c^2}=1/k[/math]
since in this scenario Dx = v
Scenario 2
Now, what if we consider the earth twin ( t ) as moving with velocity -v away from the travelling twin ( T )?
[math]t=\gamma (T+\frac{vx}{c^2})[/math]
[math]\implies \frac{dt}{dT} = \gamma(1-\frac{v^2}{c^2})=k[/math]
and
[math]\frac{dT}{dt}=\frac{1}{\gamma(1-\frac{v^2}{c^2})}=1/k[/math]
In this scenario Dx = -v
So you can see the two situations are equivalent in terms of time scaling for both observers. Guy missed a tricky minus times a minus. The first times -v flips the + sign, then when -v occurs as Dx it flips the minus again.
Equivalent motions produce the same derivatives with respect to the time in the moving reference frame.
I won't deny time dilation and length contraction are weird though, and if a physicist attempts to think of them as measurement illusions, they're not doing it right.
With regard to the block-universe that this thing seems to imply. The block universe is essentially conceiving of the vector space (x,y,z,t) as a space-time manifold - as if when all components were free to vary along their ranges, we have a continuous set of snapshots of all events. This isn't implied, what is implied is that for a given equation of relativistic motion there is a space-time 'block' corresponding to its trajectory over space through time. It would be odd to consider space time an invariant block when the things within it can distort all of its motions with their particular properties.
I thought you would've quite liked this, special relativity produces a multiplicity of blocks and the Lorentz transform renders the blocks reconcilable. Which is to say, with a more ontological framing, the unfolding of the universe is relative to the trajectories of its localising elements - the differentials of movements - but the category of relativistic motion nevertheless has a clearly demarcated set of potentials.
Weyl’s statement, implying that the experienced passage of time has no objective
counterpart, would have had revolutionary implications had it truly been taken to heart.
But relativists themselves do not seem to have been entirely clear on the implications of
the concept of space-time, and the meaning of these statements had perhaps more
radical ramifications than anyone cared to make clear to anyone. We will briefly
examine these...You must at least offer a "theory of the illusion."
Agreed. Insofar as this article is criticising lazy metaphysics from physicists, I appreciate it. Insofar as it's shitting on relativity, I don't. But, the 'shitting on relativity' through thought experiments does show the need for lots of ontological work. Hence this thread.
Comments (98)
I never thought about it this way, and you're right, I really do like this. My first thought was to Deleuze's reading of Spinoza, in which he aims to "make substance turn upon the modes", rather than the other way around in which it's usually taken. And this too, is a kind of 'making space-time turn upon differentials of (localized) movement', rather than the other way around. I think then that my general sympathy with the Bergsonian interpretation comes out of the general self-interpretation of scientists - including and perhaps especially by Einstein - who drop the 'for a given equation of relativistic motion' qualifier and take SR as an approach to time tout court. This latter was, in any case, how I've always been thought to understand the ontology of time implied by SR.
I will try to have a more interesting and in depth response later if I can, but I'm still on holiday/traveling right now and I'm off to Vietnam in two days which is going to be even worse for me posting-wise, so I'll hedge and say here that I really appreciate the response (it's also 3am where I am right now so... :/ )
I don't have anything helpful to offer, but I'm downloading the paper and I'll read it.
It's a pretty interesting discussion piece. I don't particularly like the last two bits - essentially a rejection of the reality of time as described in special relativity, then qualia alongside some bollocks physics philosofiction. If you've not seen a paper distinguishing physical and experiential time before, I think you'd find that part interesting since you're a trained engineer. One thing the paper does interestingly with regard to the distinction between experiential and physical time is that it allows both to be mathematised - that is, considered in terms that are inspired or compatible with mathematical abstractions. That angle's rarely taken.
Don't take it personally. Relativity shits on itself and clearly is on the way out as quantum information theories replace it and along with it, its weird ontology. No harm though. It just means the end of time travel. Relativity wasn't all that much to begin with other than it help create a pop hero for science.
fdrake specifically asked that people not participate in this discussion if they don't accept the basic premises he spelled out. Apparently you still feel the need to interrupt the discussion with your sniping.
The thing is this, the OP is based upon a paper that questions Relativity's ontology which in turn is based you Bergson's Duration and Simultaneity which also questioned Relativity's ontology. So , the OP is all about questioning Relativity's ontology. I am merely agreeing.
By "somewhat present in general relativity", do you mean that the universal time is completely arbitrary?
Isn't the "universal present" explicitly contradictory to special relativity? So how would general relativity produce a universal present without contradicting the principles of special relativity?
Expansion of the universe shows up when the metric tensor has components which are an increasing function of proper time or proper distance depending on the formalisation. Duration and length may still expand and contract with respect to high speed motions, and the effects of curvature changes/expansion can still be relativised to the motion of a particle.
The trick to quantifying expansion is by looking at differential neighbourhoods of a point and relating differential changes to the metric tensor - when it is an increasing function of time, interpoint distances within differential neighbourhoods increase in time.
Rather than interpreting it as the physicists have no idea what they're doing and that 'the expansion of the universe' is indexed to a universal time then using that idea to derive contradictions in relativity: I'd prefer to keep the thread on the track of analysing the real ontological consequences of assuming its truth.
I know you're skeptical of relativity because you dislike how the relativisation of simultaneity interacts with your Aristotelian metaphysics (specifically the law of non-contradiction and its metaphysical background)- but why not take this thread as an opportunity to see what the assumption of it entails for thinking about space and time?
I'm really not interested in discussing whether it's true or not.
Actually I don't see any ontological necessity from relativity theory. A 3D model of the universe works, despite the 4D Minkowski spacetime model that SR suggests. I did an advocatus diaboli piece about the universe being 3D, and the train-thought-experiment being considered in that light. It works in either model, and thus I find no ontological implications. One thing that I did find is that no inertial frame can be the correct one because no inertial frame foliates spacetime. So a curved foliation (not an accelerated frame) such as the comoving system may be a description of the ontology. I don't buy that, but I cannot disprove the view. The comoving frame functions locally as an inertial frame.
But isn't "proper time" simply an arbitrary designation, dependent on some pragmatic principles? Wouldn't it be contradictory to the special theory of relativity to assume that "proper time" was something other than imaginary?
Quoting fdrake
Isn't this the most fundamental, and important ontological consequence of relativity, the nature of "the present"? We know the present as the division between past and future. And the way that we related to this division influences all practical procedures, it is how we relate to the world in our daily lives. If special relativity tells us that the division between past and future is just an illusion, then doesn't this make how we relate to the world illusory? What is the source of this illusion? Why would the living mind act to deceive us in this way, to create the illusion that the division between past and future is something real?
Quoting fdrake
It's hypocritical of you to say that you want to discuss the ontological consequences of the truth of relativity theory, then when I bring some up you act like "I don't want to discuss 'those' consequences"
I think it's strange to say that there's no motion in special relativity, considering the theory's topic is about what changes in motions that have speed close to the speed of light. In many respects it's what falls out of 'motion's speed cannot exceed c' and relative motions as equivalent to coordinate transforms. Further, if lengths contract and time dilates with respect to the movement of particles - which is an assumption of the OP, these are real effects that should inform the view of space and time.
I really doubt this, since this trivialises space-time curvature. The Einstein and Riemann tensors are 4-tensors, and the metric derivatives and Christoffel Symbols they consist of interact to give 4 tensors., They need to maintain the number of indices they have so that they can be contracted through identification or multiplication by another tensor to derive the Einstein field equations. 4D space-time can't be removed from SR or GR without drastically changing their character.
But, if you have a reference or previous post on this, I'd be happy to read it.
See rule 2.
Complete mischaracterisation, 'what does relativity do to the ontology of space and time if it's true?' is the point of the thread. I'm not going to engage with you in this thread any more unless you adopt the scenario. Find someone else to argue with. If you want to think of this thread as a facile children's playground with no import because SR is fundamentally flawed, be my guest, just go somewhere else, or engage with someone else, to do it.
https://science.nasa.gov/astrophysics/focus-areas/what-is-dark-energy
AFAIK dark matter is considered to be currently unobserved particles. Neutrinos used to be part of this before their measurement. AFAIK, there are loads of undiscovered and possibly unreal particles conjectured from different analysis in contemporary particle physics. It should be stressed that the amount of dark matter is a consequence of the models, not a (possibly temporary) epistemic limitation. In contrast to its composition, which AFAIK is still within the sphere of conjecture.
Similarly with dark energy, it's a part of contemporary physics, and the consequences of amounts of it are modelled. But with dark energy the amount is problematic, apparently some things predict there to be a lot more dark energy than there is.
In general, I don't know enough to comment here, other than providing a repudiation of claims that 'it's all nonsense look at dark energy and matter!', and that it's pointless to consider the effects of SR and GR on the ontology of space and time because dark matter and energy are too weird.
If you have anything about dark-matter or dark-energy that should matter in the substantive/procedural interpretation of space and time, give it a go. I'd ask, though, that you don't reduce space and time to cognitive structures, as if that would provide an account of how they work.
I made some notes discussing this in terms of relativity.
GR and SR do have a single time direction in them, only it's a 'proper time' which is composed of differentials of time and differentials of space/the speed of light. That absolutely has a direction in both of them. If it was reversed, energies associated with masses and momenta can become negative. Proper time also tends to usual time when things are moving slowly relative to the speed of light in SR, and also when there's not much curvature in space in GR.
Material processes on earth - chemical, biological, behavioural - generally don't care so much that time is relativised -of the mapping from time to proper time-, since the frames they occur within don't have relative velocities approaching the speed of light. In these cases the Lorentz transform is effectively the identity transform - it does nothing; and the field equations of general relativity reduce to Newton's force laws (with tiny corrections that only show up if you're measuring things with a crazy amount of precision).
This is why differential equations describing transport of various chemicals around cells, or age related notions like 'age-cohorts' aren't perturbed by SR or GR - anything relativity has to say about them is so similar to what a 'universal time' would produce it becomes a difference that makes no difference.
The theories themselves reduce to usual Newtonian mechanics in low-speed low-curvature/mass scenarios. Luckily, this is the world we find ourselves in - most of the time - on Earth. And it is within this order of things that most processes unfold.
Usual conceptions of simultaneity still apply, usual conceptions of space still apply, for the majority of processes on Earth (on large enough length scales). The conception of simultaneity and invariant distances are not illusions in most scenarios, but they do produce transcendental illusions when applied outside of their scope. Special and general relativity are good descriptions of their target phenomena, empirically, and their influence cannot be removed by mistaking the subjective necessity (a-priority) of some antithetical concepts as the empirical failure of these theories.
Much better to see how things are and think about that, rather than begin from (what is purportedly) pure reason and constrain existence to its edicts.
Don't throw the baby out with the bathwater.
People have found things out about dark energy and dark matter. Neither the existence of dark matter nor dark energy are errors in physical theories, they are predictions. Where flaws or disagreements lay are in their properties - like the amount of dark energy and the particle-constitution of dark matter. When a better way of thinking about them or their constituents is discovered, it will become part of the scientific 'canon' you dislike so much. Their existences aren't illusions of the theory, Rich, they're very likely to be real - and that can be seen from the current state of the theories.
Completely inappropriate to characterise them as illusions. Also see rule 2.
Until they are actually observed or measured, they are just plugins to rescue a theory, just as Vulcan was created to save Newton's theory. What happened was that the invisible planet of Vulcan was replaced by a 95% invisible universe. For the most part, in the history of science, plugins have usually indicated a completely new theory is necessary. Illusions even more so. In the case of General Relativity, very little is lost, which is why completely new approaches are being investigated, one's that do not rely on GR's ontology. What will be preserved in any approach is "gravity" whatever its ontology may be. I suspect it will involve quantum entanglement as opposed to geometrical spacetime.
I don't think you payed much attention to the link you gave me Rich. The presence of dark energy has implications for the cosmological constant.
That there are unknowns on the frontiers of scientific research, especially when those flaws are known and researched by those researchers, is not just normal science functioning, it's close to being analytically true. These unknowns are linked to known things, and that set of relationships lets researchers tease out things from the unknown. Physics and cosmology are not yet degenerate research programs, and the puzzling nature of dark energy and dark matter are being researched in a manner consistent with normal science. Specifically here, afaik, attempting to study these phenomena in terms of different field theories or as consequences of the cosmological constant/metric term in the field equations.
No reason to think that they're degenerating, really. Since successive theories about them are still theoretically progressive (in the expansive form in this case), and there are competing research programs vying for 'the best account' of dark energy and matter. Normal science going on here. Dark energy and dark matter, far from being surface effects of scientific ignorance, are part of the core of scientific research in these areas.
You're not doing a very good job of pooping on science this time. So:
how do you think of space and time? How does relativity enter into it?
Yes, in this case, we have replaced a theory (Newton's) which required an unknown planet, with a theory (GR) that requires a 95% universe. I have no problem with unknowns, as long as one represents it properly. Not only are the puzzling nature of a 95% unknown universe being investigating but so also is the theory that requires it (not a bad idea in my view). GR is actually not that sacrosanct especially since it isn't part of quantum theory. The nature of gravity of course is relevant to any science or ontology. Again, I believe the current target direction of quantum physicists, that gravitates around quantum entanglement will be very fruitful and ultimately space-time will be a relic of physics as was the fate of particles.
I don't poop science, I poop invisibility and illusions, the type magicians are involved with.
Are you asking me what I think of space-time as an ontology? I think it is invisible like the rest of the universe it created.
https://youtu.be/mcMnn5TpqT0
https://youtu.be/RjQg8on4yS0
They are each over 1.5 hours in length so quite difficult to summarize, especially since they are very dense in information.
Look fdrake, either you're having difficulty understanding, or you're simply in denial of what relativity does to the ontology of time. Fundamental to the ontology of time is the distinction between past and future. This is how we derive the fundamental ontological categories of actual and potential, what has actually occurred, in the past, and what is possible, in the future. The boundary, which gives this distinction its ontological status, is called "the present", "now". From the assumption that the boundary is real, having ontological status, we conclude that the determinations of before and after also have ontological status.
Special relativity assumes that the determination of various events as past and future, or before and after, is dependent on the frame of reference, perspective dependent, "subjective". This is what relativity does to the ontology of time, it makes the distinction between the fundamental ontological categories, past and future, before and after, perspective dependent, i.e. subjective.
Do you understand what "ontology" is? It's the study of being, that which "is". Do you understand the temporal reference of "is", meaning "at the present"? If this is not the scenario you wish to adopt with your question of how relativity affects the ontology of time, then what is the scenario you wish to adopt?
https://plus.maths.org/content/what-block-time
"From this block time perspective, time, as we experience in the block universe, is an illusion. "It's not a real, fundamental property of nature," says Cortês. The ticking of time, our experience of time passing, is only because we are stuck inside the block universe, moving forward along the dimension of time. "The fact that we experience moving forward in the block but not outside it comes from the fact that the block picture treats time just as another spatial dimension, and we can step outside of it. Time is not pervasive."
https://phys.org/news/2011-04-scientists-spacetime-dimension.html
The problem of the fixed block universe ontology of GR does not explain the nature of a quantum unfolding universe. Some if the issues are discussed here:
https://www.quantamagazine.org/a-debate-over-the-physics-of-time-20160719/
The ontological status of space-time as conceived of in GR is quite open to question.
I know I briefly addressed this exact passage in my post prior, but on further reflection, there's more to be said with respect to the question of time, which was what this discussion was motivated by. While I still do like this, I think this actually speaks quite nicely to Bergson's point here re: what I referred to as a desubstantialization of time: to the degree that every space-time block is relative to the trajectory of it's localising elements, what is missing or simply untheorized is precisely the passage from one trajectory to another. In other words what is missing, or rather, what is simply assumed is time itself. Time is 'given': given this space-time trajectory, that is the corresponding space-time block. But the passage of time itself is precisely what takes place 'before' (logically speaking) STR 'kicks in', as it were.
It's important to emphasise that this is not a 'fault' of STR. It speaks simply to its scope, and what kind of implications can be drawn from it. When I said that STR does not provide a substantial theory of time, this is what I was getting at. Time itself takes place 'behind it's back', as it were, and STR explores - in a totally legitimate way - what can be predicted given that fact of time's passage. But this passage itself does not fall within the scope of STR. One cannot draw a temporal ontology from it without losing the very thing it ought to account for: time.
--
The article linked by Rich above is actually quite fascinating to read in this regard (https://phys.org/news/2011-04-scientists-spacetime-dimension.html): It begins quite well by noting that "it’s more correct to imagine spacetime as four dimensions of space", and that "Minkowski space is not 3D + T, it is 4D". But from there, instead of concluding that, as a result, STR is simply silent on the question of time (i.e. it says nothing about it either way - which is the whole point of their own reconceptualisation!!), it infers instead that "the universe is “timeless” (!!!). It's basically a classic case of looking for the lost key under the streetlamp and, not finding it there, concluding that there was never any key to begin with. But what it 'wrong' here is not the theory - which in fact, the scientists have exactly right (insofar as they correctly recognise, perhaps more acutely than any before, that it's four dimensions of space at play) - but the implications drawn from it. Excellent science, abysmal philosophy.
I find a lot to agree with, but I wanna place some extra emphasis on the strengths of the theory. I believe it is informative to a naturalistic metaphysics - at least insofar as it rules out various ontological postulates.
For probably the first time since the old PF, I'll be using my own idiosyncratic concepts a lot. So bear with me.
The only thing I find disagreeable in this is that passage from one trajectory to another is internalised through the equivalence principle. Say we consider two frames of reference whose equations of motion are given by sets F1 and F2, there is a relativised form wherein velocity is mapped to relative velocity, accelerations are mapped to relative accelerations and so on - these allow the translation of specific space time trajectories to one another.
I don't think this is a merely epistemic property of SR, I think it's essentially a statement of relational closure of motion in the regional ontology of SR. Will digress on relational closure to make some sense of it, as it's a term I use when thinking about things like this. Discussing what a regional ontology is will follow.
If someone believes in a transcendent God, they stand in a relation to that God. Specifically X believes that {some set of properties obtain about that God}. If it is really that transcendent God which is related to, how is possible for something 'exterior to being' in substantive senses or 'logically prior to it' in others to relate to any particular? The impossibility of this I term relational closure, relata are always existent in some commensurable way, and moreover there must be an overlap of the modes of being/becoming of the relata in the relation.
This is to say - different trajectories of motion in SR, whatever their sense of time - have common modes of expression, and specifically the relations in this case are the mapping of velocities to relative velocities and coordinate systems to others. There's no external 'space of trajectories' to go to for any regional ontology of SR. I don't mean 'SR gives a good account of aging' or 'SR gives an account which involves human reaction time' or anything to do with evolution, which have their own regionalised notions of time, just that trying to find a sort of movement which isn't described well by SR in its own terms is pretty hard, if not impossible. You can find examples by going close to very dense objects, however, and in these cases GR takes over.
For regional ontology, I refer to the specific mode of being of a designated class of phenomena. The only classes which can have regional ontologies devoted to them are ones with relational closure. I think this is similar to 'creating concepts on a plane of immanence' in Deleuze (or as it's thought of by Daniel Coffeen). Further, developing a regional ontology of a class of phenomena corresponds to the study of how it relates its subunits, and how those relations relate.
It's in this sense that coordinate transformations in SR are not just principles of relations of the objects in SR, they're also the means by which the relations are related. The generation of all of these relations for the regional ontology of SR comes from two principles, the cosmic speed limit of light and the equivalence between relative motion and (Lorentz) coordinate transformations (the equivalence principle). Everything follows from those building blocks.
That said, the passage of time can be said to be presumed in SR and GR insofar as it is primitive in the relations of SR and GR - it's a dimension of a vector space, which when combined with others (space) it produces/models the relativisation of time and space through the category of motion. Not simply in the sense that 'motion is space change over time' or that 'motion is change', but it effects the hows of both - motion as such, just as time as such is not part of the regional ontology.
In some senses, yes, in some senses no. Heidegger treats regional and fundamental ontology in a similar manner, attempting to ground regionalised things like moods and language in more primordial things like self-direction and the interpretive-as-structure. But I think this is an idealist way of looking at it - as if the ontology of Dasein was derived from but not conditioned by its ontic realisations. Similarly, SR does place a few constraints on what an ontology of space, time and motion should look like; how it deals with motion as such, time as such and space as such. By as such here I still mean in a somewhat constrained sense relating to physical properties and material flows.
(1) Time itself should be considered as something which can interact with its own unfolding, considering that motion may change its rate of unfolding.
(2) Space itself should be considered as something inseparable from time and vice versa, otherwise space-time curvature doesn't make sense.
(3) Motion itself should be considered as more than an analytic composite of time and space, since it effects the unfolding of its constitutive objects and itself. It is both a relational category of time and space as well as a phenomenon effecting both.
(1),(2),(3) together mark space,time and motion as of equivalent logical priority. Ontologies should treat them as distinct but inseparable.
There are also more specific conclusions that can be drawn:
(A) Time as such cannot be subordinated to a notion of event succession, since temporal orders of events are relativised to motion. The event-clock of the universe can be fickle.
(B) Space as such cannot be subordinated to extension, as time is implicated within it (and vice versa) and these things all change depending on what is analysed. There is a little wrinkle here in terms of treating time as an extensional dimension as well as an index of events, but axiomatically positing the two as the same is what happens when you make it a dimension of the space-time vector space.
Another thing relativity teaches us is that a different regional ontology is needed for the every-day. That is, non-relativistic thinking. We can't ignore the various limiting theorems that reduce GR to SR and SR to Newton. In this realm temporal order is preserved. Our technology can push us past scenarios of the every-day, however, but the effects of it are usually confined (like in the LHC) or very small (like clock differences on transpacific flights). In other words, we can't say that the ontology of GR and SR is a complete account of their contained concepts, even though there is a large region of overlap between their respective 'as such' categories and the theories. They do quite a lot to explain various phenomena in the universe, and so should be treated with respect within their zones of relevance.
Another big thing to note is that experiential time, and the relation of experiential time to physical time, are largely untouched by both.
It is certainly possible to interpret relativity in the context of a 3D world evolving through time. The only problem is that it isn't very elegant. For instance, the precursor to SR, the Lorentz Ether Theory, preserved our traditional notions of absolute time and space by introducing an undetectable ether (which you can probably guess is why it didn't catch on). Apart from that though, it was empirically equivalent to the theory, just with a preferred frame. In GR, the case is somewhat different (since there is no such thing as an inertial frame), but we can still introduce a preferred foliation if we want to. Of course, I'm not saying here that we should (since again this would be ad hoc), but only that we could.
I interpreted noAxioms as suggesting that it's possible to interpret things in a way that made 3 dimensions of space & time combined. Don't see much of a problem with there being different rates of development of phenomena depending on reference frame - that's just using the chain rule in calculus. IE, differentiating x by time in another frame would (dx/dT)(dT/dt).
I wasn't referring to anything like that. I suppose what I'm trying to say is that relativity doesn't necessitate a 4D block universe. It is certainly possible for us to view time in the traditional sense, as a 3D world that changes via. the passage of time though there are costs to that sort of view.
http://discovermagazine.com/2015/june/18-tomorrow-never-was
"What’s most disarming about the block universe, remarks Ellis, is that unlike a movie that plays through a series of successive instants, there is no special point in time that all inhabitants would agree on as “now” — no unique marker that separates the fixed past from the open future."
"There’s more. Just as the students would disagree on whether the clock tower was to Ellis’ right or left, depending on where they stood, two people in Einstein’s block universe could even argue over the order in which events occurred. To one person, the Trinity clock might strike 2 p.m. before Ellis finished his last sip, and to another, the bell chimed only after he was done."
"In the block universe, then, what someone perceives as the future is what someone else saw as the past, depending on the person’s position and motion. Events that have yet to happen for one person, it appears, have already happened for another. The future, though it remains unknown to you, seems to be written already. ... Einstein himself described it thus: “People like us, who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.”"
"Ellis’ new model .. argues that Einstein took that concept too far. There’s no need to assume that the fourth dimension must already exist out into infinity. Thus Ellis’ model has one crucial difference from Einstein’s: The future boundary does not encompass all that will ever happen.
"Thus Ellis’ model has one crucial difference from Einstein’s: The future boundary does not encompass all that will ever happen. Instead, the leading edge of space-time marks the “present” crawling outward, moment by moment, transforming tomorrow’s maybes into yesterday’s fixed happenings. “Tomorrow there will be one more day in the universe than there was today,” says Ellis. “The past is real and can have had an effect on us today, but the future cannot influence us because it does not yet exist.”"
" In Einstein’s view, these events — and all future events — coexist. But in Ellis’ picture, both events must lie in the portion of the evolving block that houses the past; they are fixed into reality before information about them reaches anyone. Similarly, in Ellis’ view, two observers can disagree on the duration of an event, but only if that event has already crystallized into the past."
"If Ellis is correct, how does he explain the mechanism that causes the front edge of the universe to push forward? “The surface is where the uncertainty of the future changes to the certainty of the past,” says Ellis. He found hope in another branch of physics, well known to physicists, where a transformation from uncertain possibilities observably becomes a fixed reality."
"Quantum experiments give Ellis the heart to believe that time is real and Einstein’s simple block universe is wrong. “Some physicists say that the future is already written into today, but I think that they are not taking quantum uncertainty seriously,” says Ellis. “Quantum uncertainty, to me, says the future is not determined until it’s happened.” He contends that at the front edge of his evolving block universe, the uncertain future crystallizes into the past through a sequence of microscopic quantum events. "
"And he scoffs that the burden of proof should lie not with him, but with those who claim that time is a mirage of our own making. After all, Ellis says, not only does his model gel with quantum experiments that appear to show that time is real, it also encapsulates our common sensations, “which is tested every day, by everyone, whenever anything happens.” Life itself is an experiment that backs his view.
"With this in mind, he quotes from the ancient Persian poet Omar Khayyam’s musings on the visceral difference between what has gone and what is yet to come: “The moving finger writes; and having writ, moves on: Nor all thy piety nor wit shall lure it back to cancel half a line, nor all thy tears wash out a word of it.” Then, with a guttural laugh, Ellis throws down a challenge to his critics: “If you don’t believe that, then you go back and change the past!”"
Just briefly on this, my interest was less in the science itself than in the rhetorical moves made within it: the illigitimate jump from spatializing the 'fourth dimension' to declaring a timeless universe. It's illustrative of the 'scientific' instinct to do away with time, even when - perhaps especially when - there lacks any warrant to do so. Will come back to the big post later hopefully.
Quoting fdrakeI meant nothing moves through the block of Minkowski Space time. Time is built in. This is about the block view, not SR or GR. Velocity is the slope of the worldline of some object. Relativity works in block or in 3D view, so the ontological difference is interpretation with no empirical difference. Relativity was born of the observation that the worldline of a photon has the same slope regardless of assignment of coordinate system. That fact is not a necessary property of Minkowski spacetime, so block universe is not necessarily relativistic.
Quoting fdrakeMy post was using SR case, which admittedly has bunk to do reality except in a local sense, away from significant spacetime curvature. So perhaps the field equations do indeed require 4D spacetime.
The posts I refer to is not in this forum. Took a long time to figure out why I was in read-only mode here. Essentially I ran the train thought experiment in 3D absolute space and ran into no contradictions. At least one observer is simply wrong about his assessment of the simultaneity of certain events.
If the twin paradox was mentioned, that is not a minor point. However. If SR was treated as simply a measurement problem, with no ontology, then indeed it is minor.
Yeah, I don't think a block universe is necessitated by the conceptual structure of relativity either. I spelled out what I thought were the ontological consequences of it in my reply to SLX. If you want to think of blocks because of space and time being conjoined, it relativises the blocks to individual motions - something I find pretty cool.
So you're saying that a block universe is neither implied by or implies either relativity? I think I agree with this, but I don't understand how you're using four-velocity in the presentation. Can you give me some more words please?
I'd also really like to see an abbreviated form of the post you made on another forum.
One of the minute-physics videos on special relativity highlights this. Special relativity isn't treated as a topic worthy of study on its own - despite showing up in particle physics. From memories speaking with physicist friends at university, its teaching was highly idiosyncratic and it's not presented in a general form.
I don't think this implies that it's not worthy of study or philosophical interpretation, especially since it's a less complicated form of general relativity - I think you get some interesting constraints on naturalistic metaphysics by trying to make it consistent with special relativity alone. But of course, it'd also be interesting to make it consistent with GR - more work too.
Quoting fdrakePictures are hard to post. Consider a simple spacetime of 2D, one of space, the other of time. Lots easier to visualize. Twins experiment requires only 1D of space for instance. So it can be done on 2D paper, preferably circular paper so there is no preferred orientation.
Draw a dot A somewhere, and B somewhere else. This represents 2 events, say the start and stop of a journey. Straight line between the two is its worldline, unaccelerated. A curved line denotes acceleration. So now superimpose a vertical axis S (space) and perpendicular horizontal axis T(time), with origin at A. If you orient the paper so the line is at an angle, the vertical space displacement of B is nonzero and the slope is the (positive or negative) velocity. If you assume a different frame and orient the paper so the T axis followsthe worldline, then the space displacement is zero, T is at a maximum value at event B. There is no motion in this frame since spatial displacement remains zero for the length of the worldline. Angle the paper a lot and the space displacement gets large and the T displacement starts to shorten, but regardless, the unitless separation between A and B (called the interval) remains fixed.
If there is a third event C which is directly above B at a certain orientation of the paper, then B and C are simultaneous, but only in that frame. Orient the paper different and the events become ordered differently.
All this is pretty much a description of flat Minkowski spacetime. At no point does something move across the paper, and orienting the paper different does not make any real change to what is drawn on it.
Found a bit of it: Context is the train experiment, where two lightning strikes occur, one at each end of the train, leaving a mark on the platform (and train ends) as it strikes. An observer on the platform and on the train each make their assessment of the simultaneity of the two lightning events.
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Under the 4D model, the platform guy notices the two strikes at the same time, and after measuring the distance from where he was standing to each of the platform strike marks, determines that the two strikes were simultaneous. The train guy detects the strike at the front of the train first, and afterwards the rear strike. He also measures his distance to the two marks on the train, and is equidistant. He thus concludes that the front strike happens before the rear strike. Two frames, two different but valid ordering of events.
3D model, with 3D space and separate absolute time:
Two events are not ambiguously ordered. If one frame orders them differently, that frame is not the preferred one and it orders events incorrectly. Two events simultaneous in that frame are not in fact simultaneous, and thus there are no future events that exists. The frames that put you simultaneous with those future events are simply wrong about their designation of simultaneity.
So in my examples, I always pick the unintuitive stationary guy. So it turns out that the train guy is the one actually stationary. The platform observer is on the moving ground.
Lightning flashes go off, hitting the front of the train first, and the back later.
The train observer is midway between the two events, and records the front strike first. Being equal distant from the two events, the observer knows the front strike happens first.
The ground observer is moving towards the rear of the stationary train, and by the time the light from the two signals meet, he is at the point where they meet, so he measures the two signals as arriving simultaneously, but one has traveled further than the other, so this is expected. His clock also runs slow, but since he didn't use it, nobody cares.
The guy not actually stationary is incorrect in his assessment of two events being simultaneous. So the guy on the platform is basing his simultaneity assessment on the false fact that the two marks on the ground are where the lightning struck. Since the ground is moving, this is clearly not true. The marks are not the point in space where the strikes took place. The endpoints of the train are the actual spot where the strikes took place.
This is a description of the 3D scenario, and I hope is free of inconsistencies.
BTW, I also saved a post describing the twin experiment with only SR rules, no acceleration, and using a tag team. It is more for illustration purposes, and argues no philosophical points.
Aha, I see what you mean. You're providing a demonstrative example of motion in 1 spatial dimension and 1 temporal dimension, not saying space and time can be thought of as physically 1 space 1 time in general.
The rest was just an example of the conservation of proper time.
I don't think this is true. If it were legitimate to axiomatically posit a preferred frame of reference with which to define all motion relative to, it'd be a consequence. I think the absence of a preferred reference frame is an implication of the equivalence principle - what would be the point in stressing the transformability of motion to equivalent forms if the only purpose was to index all motion again to an arbitrary origin point? Why should any one ordering of events be more true than another?
In other words, nothing changes about relativistic computations if there is a preferred reference frame for any given motion, so there being a preferred reference frame is something out-with the influence of the theory. An arbitrary decision about space-time should not structure how we think about it.
Your post takes the view that a predicate equivalent to 'is the true reference frame' is something that can be appended to a reference frame, this is something SR and GR prohibit from having any ontological import.
If I've understood you and it, anyway.
The rest was just an example of the conservation of proper time.
Undetectable is what the equivalence principle states, no?. Just because something is undetectable doesn't mean it isn't there. Hey, I'm not arguing for it, just against this being a proof against it. I personally favor a block view, and no ontology to it at all.
Correct. Something undetectable makes no difference to what is an empirical theory.
No GR prohibitions anyway. SR perhaps not, but it describes a flat massless spacetime that doesn't correspond to reality. I.E. no inertial reference frame foliates the universe, so none can be the correct one. Inertial frames are local, and the universe is not. There are objects that can actually be seen that do not exist in our inertial frame since they are, in our frame, simultaneous with a time before the big bang. Talking about stuff near the edge of the visible universe that "has since" (<-- questionable use of verb tense) passed beyond the Hubble Sphere which confines events even remotely valid in our reference frame. Hence the curved foliation with is not a reference frame at all, but covers all the universe.
I don't think an undetectable in principle difference should be elevated to a difference in practice.
I'm assuming 'foliates' here means, essentially, 'providing a coordinate system for'. And the way in X foliates Y is always done differentiably (my differential geometry-fu isn't particularly strong). So I'm thinking of a foliation as the thing which describes the rate of change of an application of a coordinate system to a locality with respect to infinitesimal shifts in its origin.
So at time t they were in the Hubble volume, and at some time t' they expanded out of it? That's the picture?
What implications do you draw from this? I've said previously that there are still things which can be said about spacetime in general with respect to increasing time - like the expansion of space when the metric tensor is an increasing function of time. I interpret foliations as ways of setting up for questions like this - they will provide a system of coordinates in which the evolution with respect to some variable, probably time in this case, can be indexed.
I don't think this makes length contraction or time dilation go away, but it does implicate some notion similar to universal time in the pre-theoretic sense. Regardless, how would you think of this time without destroying the relativisation of time/space through motion? I doubt the right answer is through an assertion against the relativisation of simultaneity (which screws with time = the succession of events), or against the way space expands/contracts relative to motion (which screws with its identification with pure extension).
It is an ordering of events, and not otherwise specifying full coordinates. This event is simultaneous with that one, and prior to that third one over there. A foliation of the universe must order all events, not just local ones like an inertial reference frame does.
Foliation specifies no origin. Just relations, and only temporal relations at that.
Pretty much yes. Time t' would be the event of that thing increasing its proper distance from us at the speed of light. Like from beyond the Hubble Sphere can still reach us by crossing back and eventually getting here. So maybe the image of it we see is one already outside that Sphere. There is an event horizon beyond which objects are undetectable from here even in infinite time.
About t', I speak of proper distance. In reality, time is frozen for it in our frame, and t' is unexpressible in our reference system, so t' represents the local time of both here and there when the contracting Hubble Sphere no longer includes that distant place. Something like that.
Well, IF presentism is true, AND the foliation suggested by GR happens to match the geometry of this 'present' boundary, then there is an actual velocity and location of all things. So from what I read, this 4D metric tensor means in part that the distance between two events is path dependent, and none of the paths is straight or obviously the actual separation. In 3D, a lot of that falls away, and two events need to be simultaneous to have a defined spatial separation. Not sure how much I'm addressing your question, or if I'm being accurate here.
Of course this 3D view still works under relativity. The twin comes back younger because time progresses slower if you move faster. Clocks do not measure time in that view since there is no way to know if it is stationary. So they just measure local process rates. Relativity of simultaneity is an illusion then. As I said, the platform guy is using incorrect data to determine the two events were simultaneous. They're simultaneous in his frame, which is all he cares about. He cares not that his frame is not actually stationary, since that distinction makes zero difference.
I was meaning something like the following: the equivalence principle in SR is essentially that motion is always relative motion - which introduces coordinate transforms - constrained by a cosmic speed limit -which introduces the scaling factors. In GR the equivalence principle is essentially between gravitation and an accelerated (that is curvilinear) coordinate system, and that intrinsic curvature is introduced by mass.
One of the motivating examples for the equivalence principle is the elevator thought experiment. Someone in an elevator could not tell the difference between the elevator moving down with constant acceleration due to a cord and the elevator moving down with constant acceleration due to a gravitational field. If you ignore tidal forces, there's nothing the person in the elevator could do to see if their acceleration is cord based or gravitation based.
In SR, this kind of thing manifests in equivalence between a rocket moving away from a planet with constant speed and the planet moving away from the rocket with constant speed.
I was trying to say that the undetectability of the difference between the relata in any equivalence principle should not be interpreted as an epistemic property, the equivalence in descriptions should be interpreted to be as real as its consequences - such as the relativity of simultaneity and length contraction. These things really happen and are not mere artefacts of coordinate system choice.
A foliation of space-time is a lot different from a foliation of time, you were referring solely to the latter? I don't understand how this is possible, given that in some reference frames event A can happen before B and in some event B can happen before event A - and there can be no strict total order (like <) with this property. How would you construct a foliation to produce a time which obeyed this?
One possibility would be to say that if there exist two events A and B, that they occur at the same time if and only if there exists a coordinate system in which they do occur at the same time. Or that there exists a coordinate system in which A is before B and B is before A. Of course coordinate systems exist in which B can be said to have occurred any time before A or B by adopting the frame of a particle with a particular motion (you can solve the Lorentz equations for v). But I think that this conception of time inappropriately quantifies over reference frames, and destroys the relativity of simultaneity. That is to say, simultaneity in SR is simultaneity in a reference frame, and the solvability of the Lorentz transform for arbitrary t shows that the ordered pairs of events in any such order are incompatible with a total order; unless time is trivialised in the sense that all events occur at the same time (which isn't presentism or a block universe).
So, the question is whether an order produced by such a foliation would resemble anything like a universal time. I'm not convinced that there is such an ordering, could you provide some references for where you're getting this from? I think you're losing too much detail when thinking of foliations as an order.
Definitely a useful thread in demonstrating that Relativity is an ontological mess, with some nominal usefulness as simple transformation equations that no one really understands. Bergson analysis was spot on and Ellis, reluctantly, is going down that path. No block time, only frozen (memory) time.
I find myself resisting this. Is my length really contracted if in my frame, it's the length of everything else that's contracted? Seems like an artifact of of choice. On the other hand, the twin really does come back younger, despite the stay-home twin aging slower during both legs of the journey, from the frame of the rocket-twin. No mere arithmetic games can do that.
Don't know what the latter is. Events are points in spacetime, not in time. Not trivial to order them, but it would be trivial to order moments in time.
Different frames foliate space differently. That's what frames do. They specify an ordering, but not otherwise a coordinate system or an origin. An actual present would imply an objective foliation instead of a relative one, but SR is all about the physics in relative terms and isn't affected by a possible objective foliation.
Actually, under relativity, there exists a frame such that any two (reasonably local) events are simultaneous with only spatial separation, are at the same location with only temporal separation, or right on the edge between the two (on the edge of each other's light cone) in which case separation is 0/0 or undefined. From event A, all events outside its light cone are the first sort, all inside are the second sort. There can be no two points that don't meet one of those 3 cases. This is pure relativity, and has nothing to do with 3D space or absolute time.
So as for your comment above, no, A and B are not simultaneous just because some frame exists where they are. They're only simultaneous in that frame, and not in some other frame where they're ordered A first or B first. One can rotate the paper at will to put C above or below B in the time dimension (my events B and C were potentiall simultaneous in my paper example. A and B were inside each other's light cones and B is unambiguously after A).
All true. Presentism just says that there is an objective correct answer as to which of A or B happens first. Relativity supplies frame dependent answers, not objective ones.
Comoving time is such an ordering. Essentially, for every event in spacetime, the actual time there is the age of the universe in the frame that maximizes that age, or in which the red shift of distant objects (most notably the CMB) is isotropic. Same thing. That age is an objective one, and provides an objective ordering of all events.
So that's the 'frame' referenced when they say our galaxy is moving at about 0.2%c. Our solar system is on the side that cancels out some of that, so we're actually cruising at about 0.12%c. I put 'frame' in quotes because it is not an inertial reference frame, and is different for every point in space due to expansion.
I think we agree on this. So long as you're not going to say that from the equivalence of motions we should posit one reference frame as privileged. I think you agree that such a decision has no consequences, and it doesn't mean anything to index motion to one privileged reference frame. The procedure for doing that is also antithetical to the logic of SR and GR.
It's trivial to order them within a given reference frame, not trivial to order them when multiple are being considered. Think it's impossible to provide a total order of events consistent with all motions, I saw you agreed with my argument that this is the case, so I don't think we need to discuss a total order without respect to a reference frame more.
Do you conclude that relativity thus refutes presentism?
Great, this is another convergence in how we see it. I think, anyway.
Comoving coordinates are those in which the expansion of the universe is uniform in every direction. So a measure of proper time between particles tagged to comoving frames would be a time measure with respect to the expansion of the universe. This makes good sense as a vantage point with which to define cosmological time. So when people speak about the age of the universe, we're speaking about it with respect to the history of intrinsic changes to its space.
However, there's nothing saying that this perspective must be adopted for all phenomena, and it does not remove the shenanigans relativistic motion induces on temporal orderings of events. The age of the universe is certainly a relevant parameter with respect to cosmic expansion, but it renders other motions untouched. That is to say, the sense of time derived from considering comoving frames must be conceptually consistent with the ability to induce changes in event orders by motion. There are real trajectories with which the expansion of the universe looks different.
Relativity says the math works with or without the existence of magical invisible pink unicorns, but it doesn't refute said unicorns. Presentism is such an addition: Something irrelevant, undetectable, and unrefuted.
Yes, but I think that from any such trajectory, the universe appears younger than it would if it were a comoving object, and an observer on that trajectory would be aware of the deviation from the local mean.
And you don't think that simultaneity is a frame dependent phenomenon refutes the idea of there being an objectively correct answer to whether A is before B? Why or why not?
Oh I see the point of this thread now. You want to discuss the fact that relativity refutes presentism. Why didn't you just say that in the op?
"I don't want to discuss the question of whether relativity refutes presentism, I want to discuss the fact that relativity refutes presentism."
No, I just don't trust you or Rich to have anything I would find worthwhile to say on the topic.
Why not put that in the op then? Instead of a convoluted list of rules, simply state "Metaphysician Undercover, Rich, and any others who do not agree with the ontological implications of relativity, need not reply."
Well, we did hear from Ellis (no slouch) and other physicists on the subject. But your quest is a noble one. To do what Einstein couldn't do, which is to make Relativity compatible with quantum theory. I believe your approach is probably better, just ignore quantum theory and build your block universe anyway. That is what you are desperately trying to preserve, isn't it? A block universe in a universe defined by quantum theory indefiniteness. Tough job, but heroic nonetheless.
Well, if you're happy to adopt the rules and stay on topic, I would've at least read your responses.
So do you wish everyone to pretend that Relativity's block universe ontology is fine and quantum theory is all wrong? Just say so. Say you would like us all to ignore the elephant in the room.
I never broke rule 2. I never referred to any of the things listed in rule 2. I referred to the arbitrariness of "proper time", which ought not even be considered as a "deficiency of measurement", arbitrariness is just a standard feature of measurement. Your accusation was unfounded and just an excuse to disregard the points I was making.
You are assuming that relativity is true, and asking how this affects the ontology of time. The obvious answer is that "proper time" is completely arbitrary, meaning that there is no true, or real thing anywhere, which corresponds to this notion. It's like assuming a "metre", with no physical standard anywhere, to refer to. Do you accept the truth of this, concerning "proper time", or does it somehow break rule 2, and fall into the category of things you don't wish to discuss?
Your question can be interpreted different was, so I pick this one: Time as used in physics equations is what simultaneity is about, and relativity describes that. The second definition of time is from presentism, which is the rate of advancement of this 'present', which has no units, not even seconds per second since the two are different things. So I will say that presentism posits a different definition of simultaneous altogether, and there is no refutation of any part of the presentism because presentism is irrelevant.
That's the key word: irrelevant. It is an invisible pink unicorn, and not refuted for the same reason.
Relativity is a scientific theory born of empirical observations. Presentism is a metaphysical interpretation of time, not a scientific theory at all. It has zero falsification tests, as do all interpretations. If such a test (a difference between 4D block and 3D universe) could be proposed and performed, then it could be elevated beyond interpretation and one or the other could be falsified. Meanwhile, relativity would stand because it works the exact same way in both interpretations.
I don't see how these two things can be compatible:
(1) There is a unique order of events induced by the idea of the present in presentism.
(2) Events A and B can be ordered differently depending on the motion of a particle.
I don't understand how you can say 'presentism is independent because it's metaphysics', when one of its implications is negated by how time works in SR.
IMO, presentism explicitly rejects (2) cause it has to reject the relativity of simultaneity as you have noted. That doesn't mean that it rejects the science of relativity though. More specifically, you can accept the mathematical models and the empirical predictions of the theory without accepting the relativity of simultaneity itself (essentially privileging one order of events over the others). Similarly we can accept the science of QM without accepting that indeterminism is true (as in the copenhagen interpretation) or that multiple parallel universes exist (like in the MWI). That is the reason why we call them "interpretations" instead of "theories", "metaphysics" instead of "physics". In that sense presentism is "independent" from both SR and GR. Do you agree with this?
I certainly think it's possible to think that there is a real unique ordering of events by rejecting relativity. But I don't think it's possible to think that there is a real unique ordering of events while accepting relativity.
Adopting a specific reference frame, or class of reference frame, can be useful in inducing an order of events relative to a process - like picking coordinate systems in which the expansion of the universe is spherically symmetric for probing the age of the universe - but this doesn't negate anything from SR.
I think the more interesting endeavour, rather then debating whether presentism is true or not, or accepting or rejecting SR based on previously held principles, is to try to make sense of its implications in a naturalistic metaphysics, and what constraints they place on metaphysics of space and time.
I'd draw the following conclusions from SR and GR:
(1) Space, time and motion are distinct but inseparable, no two should be taken as a derivative category or combination of the other.
(2) Time cannot be thought of as a unique succession of events, as this is contradicted by the real motion of objects.
(3) Despite of (2), time can be immanently defined within a process to study its history. Perhaps different coordinate frames can be thought of as immanent definitions of space and time with respect to motion or mass.
(4) Space cannot be considered as an unconditioned field of pure extension, since motion doesn't just happen through it over time, motion and mass change space itself.
(5) The behaviour of space and time is induced by motion and mass, the former being extrinsic properties of space/time and the latter giving intrinsic properties of space/time.
(6) Different metaphysics may be appropriate depending on whether SR or GR are in play or not, SR isn't very relevant for slow moving objects or intrinsically curved space, GR isn't very relevant when there is no intrinsic curvature to space.
Methodologically, there are some interesting implications of (6): different domains of things (in the broadest sense) may require different ontologies. This is why I posted previously in terms of regional ontologies of SR and GR.
I see it as intellectually lazy to posit metaphysics as independent from science, much more interesting to attempt a naturalistic metaphysics which is informed by current scientific theories. Rather than, say, dogmatic adherence to Aristotelian physics or New Age Quantum Woo.
Maybe you can define what you mean by "relativity" for me cause I think we are using the term differently.
To me, when I speak of "relativity" and "quantum mechanics" I am referring to them as scientific theories through and through. That is, the postulates, the mathematical formulas, and the predictions that we derive from them. Everything else isn't relevant. This is why I say that presentism is compatible with SR and GR, because as far as a physicist is concerned on the matter, it isn't an idea that has been falsified. It has the same status with respect to relativity as does determinism to QM.
Quoting fdrake
I agree with this. I am certainly not suggesting that we shouldn't base our metaphysics in part on our scientific theories. By "independent", I just meant that it cannot be falsified via. the scientific method. If a metaphysical theory such a presentism or eternalism could be falsified in such a manner then they would no longer be metaphysical theories.
The first speaks of objective ordering, and the latter means that the observer is free to order events differently, and physics will still work without detectable differences, rendering any potential objective ordering undetectable. The latter is about empirical observation, not about an interpretation of what actually is. And #2 should be "depending on the reference frame", not depending on particle motion. 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.
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.
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.
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.
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.
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.
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.
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.
It says there is a unique objective ordering, not a unique ordering. None of the SR orderings are objective.
Quoting fdrakeSR doesn't talk about objective orderings, so I don't see how the above can be inferred.
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.
Ok. What differentiates an objective ordering from one in obtaining in a reference frame in special relativity?
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.
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.
SR make no ontological assertions. It just says that physics will be observed to work identically in any frame.
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.
Quoting 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.
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:
[math]\{ \text{events which can be causes after } t \} = x_t = \{\text{events occurring before }t\}[/math]
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.
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.
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.
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.
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".
Then that would be a different scientific theory entirely. I was not talking about that.
Quoting 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.
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.
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:
[math]d\tau^2 = dt^2 - \frac{dx^2}{c^2}[/math]
If [math]d\tau^2>0[/math] between two events occurring at [math]t_1[/math] and [math]t_2[/math], 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 [math]t_1[/math] and [math]t_2[/math] have time-like separation, then:
[math]d \tau ^2 = (t_1-t_2)^2 - \frac{(x_1 - x_2)^2}{c^2}>0[/math]
which gives
[math]c^2 (t_1 - t_2)^2 > (x_1 - x_2)^2[/math]
if we wanted to find a frame of reference in which [math]t_2[/math] occurred before [math]t_1[/math], reversing the inequality here, it would need squared average velocity:
[math]c^2 < \frac{(x_1 - x_2)^2}{(t_1 - t_2)^2}[/math]
which can't happen, since it would be higher than [math]c^2[/math]. 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 [math]d\tau^2 [/math] 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.
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".
Quoting fdrakeI 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.
It is meaningless (but not invalid) to reverse the order of simultaneous events. Either way they both happen at once.
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.
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.
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.
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.
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 [math]t_1[/math] and event 2 occurs at [math]t_2[/math]. Also assume that [math]t_1[/math] and [math]t_2[/math] have a space-like distance between them. That is:
[math]d\tau^2 = dt^2 - \frac{dx^2}{c^2} < 0[/math] for 1D motion.
It's a mathematician's proof, but [math]dt[/math] can be freely set to 0 and you still get a valid reference frame, that is [math](t_1 \geq t_2)[/math]. 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 [math]d\tau^2[/math] as a quantity which can represent the possibility of causal connection between events.
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.
Quoting Pierre-NormandHere 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.
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.
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.
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.
Totally agreed.
In the transition between phenomenological space/time and physical space/time, I think it's quite common - and this is in broad strokes - to make one a derivative of the other. Kant's view on space is a phenomenological one:
[quote=Kant, CoPR, Transcendental Aesthetic]Space is not an empirical concept which has been derived from outer experiences. For in order that certain sensations be referred to something outside me (that is, to something in another region of space from that in which I find myself), and similarly in order that I may be able to represent them as outside and alongside one another, and accordingly as not only different but as in different places, the representation of space must already underlie them. Therefore, the representation of space cannot be obtained through experience from the relations of outer appearance; this outer experience is itself possible at all only through that representation.[/quote]
and time is, again very roughly speaking, an a-priori structure which gives us our index of consecutiveness of experiences.
In the same regard, Heidegger's view of space - however different in character - makes physical space (and time) derivatives of various existentialia (roughly, 'fundamental properties of experience')
[quote=SEP, Martin Heidegger, Spatiality]For example, an entity is ‘near by’ if it is readily available for some such activity, and ‘far away’ if it is not, whatever physical distances may be involved. Given the Dasein-world relationship highlighted above, the implication (drawn explicitly by Heidegger, see Being and Time 22: 136) is that the spatiality distinctive of equipmental entities, and thus of the world, is not equivalent to physical, Cartesian space. Equipmental space is a matter of pragmatically determined regions of functional places, defined by Dasein-centred totalities of involvements (e.g., an office with places for the computers, the photocopier, and so on—places that are defined by the way in which they make these equipmental entities available in the right sort of way for skilled activity). For Heidegger, physical, Cartesian space is possible as something meaningful for Dasein only because Dasein has de-severance as one of its existential characteristics.[/quote]
De-severance functions as a spatialising structure in which relevant objects for my activity are 'nearby for me' and irrelevant objects are 'distant from me'. Heidegger argues at length that the Cartesian conception of space - still present in special and general relativity, they are modern forms of Cartesian coordinate systems; real valued vector spaces - as a field of orthogonal extensions, and my place in it as a point, is derivative from this more primordial spatiality of my experience.
Time, also, is treated as derivative of the orientation of experience. Orientation, again roughly, has the component of futurity - my plans, what I will do next; the component of the present - my engagement with what I'm doing; and the component of the past - what needed to happen to be doing what I'm doing now. It should be noted that these elements work by structuring how I'm doing what I'm doing, and 'the experiential moment' is dispersed and elongated with respect to the futural,present and past aspects of Heidegger's phenomenological time. If you want to read more on this, the terms are 'fallenness', 'thrownness' and 'projection'.
Obversely, it is possible to imagine human experiential time and space as derivatives of physical time and space. The Circadian rhythm being coupled to the sun and the differences between neurotransmitter activity in the brain, the sense of fatigue from mental and physical exertions giving some sort of inner clock coupled with the one we obtain from day and night (or more generally light level). We could say that experiential time is an illusion projected from the the non-relativistic speed of our day to day activities.
I'd like to say at this point that I don't think either of these approaches gives much respect to the particularities of the derivative space/time concept. Accounts of phenomenological space/time are good at describing phenomenological time, science of physical space/time is good at describing physical space/time.
I think the following is a worthwhile question:
In what senses is our phenomenological space/time related to physical space/time? Deriving one from the other has a few problems:
(experiential allows derivation of physical) -> vulnerability to arche-fossils
(physical allows derivation of experiential) -> hard to give an account of differences between the two. (eg, flow-states and time perception)
The discussion so far as highlighted three connected ideas which act as a conceptual bridge between physical space/time and experiential space/time, namely:
(1) Time-like separation between events in Earthly reference frames is prerequisite for maintaining the order of cause and effect. This is a bit of an imprecise formulation but I think it suggests the right idea. Stuff has to be moving slowly, stuff has to be close on a cosmic scale, in order for us to get the real properties we have out of physical time accounts which use relativity.
(2) Light-cones as partitions between causally connected components of space-time.
(3) Limiting theorems of SR and GR reduce their dynamics to typical Earthly ones for most processes, so SR and GR can be incorporated in an ontology of space time.
Ever since I read a reasonable amount of Heidegger, and then Meillassoux' criticism of (experiential->physical) time derivations, I've thought it would be an interesting question to ask:
How do humans internalise physical space and time? How do experiential space/time allow us to act in a universe with a space/time alien to our own? An operational question, rather than casting one space/time as logically prior to another.
The audacity of Bergson is to have argued for the existence of durations that are as much a part of 'physical processes' as to our psychology - although he does not quite put it that way. One consequence of this is that there are for Bergson times in the multiple, not just one big block of impersonal time that everything belongs 'in', but temporalities that belong in some manner to each and every process of individuation.
This points to the issue with the nature of "an event". The events which we describe, and have words for describing, are proper to our experience of duration, which is really a very narrow range of possible experiences of duration. So if we start to hypothesize about different types of "durations", then we must allow as coincidental to these hypotheses, the possibility that "events" within these different durations are completely beyond what we have the capacity to describe. Transformation mathematics only provide a skeletal comparison, and can't tell us what "an event" would be like in a significantly different experience of duration.
Quoting fdrake
There is no such thing as the perspective of a photon. The perspective of a photon would be in its "own" reference frame, i.e. a reference frame where the photon is at rest. But there is no such reference frame.
A couple of references on the topic:
John Norton's "opinionated assessment of what we can learn about the ontology of space and time from the special and general theories of relativity":
Also, since causality has been brought up repeatedly, it is perhaps worth mentioning that there are nomologically possible violations of causality both in special and in general relativity. John Earman has written about it a number of works, such as Determinism: What We Have Learned and What We Still Don’t Know.
From the paper you linked. This kind of reasoning is what I've been trying to use all thread. How do the relativities constrain ontologies of space/time/motion?
Space-like separation is still a problem for causality. This is why I've (and seemingly the first paper you linked) tried to frame light-cones as a partition between causally connected and disconnected components. Interestingly the paper goes on to say that while this causal account appears necessary, it isn't sufficient once you switch to general relativity - in the sense that this causal connection/partition can be generated by more than one spacetime geometry.
I've not read much of the second paper yet, but there's nondeterminism even in Newtonian mechanics. Nomologically possible indeterminism anyway.
If there's a bad smell hanging around thread like this, most likely it's because the threads are rotten.