I had mentioned the rock above. Yes, it very much is a measurement. Thing X (source of photon) has now caused an effect on said rock, and X now exists to the rock. That's how QM measurements work. It causes the state of X and the state of the rock to become entangled. The special equipment in labs is only special because it records the measurement precisely for the purpose of the knowledge of the lab guys, but measurement itself is trivial. — noAxioms

It seems like you do not know what measurement is. Measurement, by definition requires a comparison. The measurement devices in QM are calibrated to perform comparisons.

You can assert otherwise, but then we're just talking about different things. You asked me what it means for an extended object (not all in one point in space) to not be in a defined state at the present, and this is what I mean by that. — noAxioms

Yes, we're talking about different things. You've created a fictitious definition of "measurement", and now you've drifted off into your imaginary realm where rocks and toes are performing measurements of light energy. So I see your explanation of what I asked is completely irrelevant and imaginary. It's nonsense.

It seems like you do not know what measurement is. — Metaphysician Undercover

Then choose another word to refer to what I'm describing, else we cannot communicate.

Measurement, by definition requires a comparison. The measurement devices in QM are calibrated to perform comparisons.

So when I open the box to check if the cat is dead or alive, what carefully calibrated device to I need to do this? It can be done in the total darkness if that helps.

The rock is doing a comparison of photon detected vs photon not detected. The state of the rock is different depending on this comparison.

Under presentism, there has to be a present hypersurface, and there has to be only one of them. Unless you pull the trick of denying objective reality etc. — Inis

Agree, but a hypersurface is 3D surface in a 4D space, and under presentism, there is no 4D space, only the 3D 'all of reality'. It isn't a hypersurface anymore if it is all of reality, no? That was my point, and perhaps it is just semantic.

For the "eternalists" and "block universe" advocates on the thread.
I want to know the status of "dinosaurs"? Are they truly extinct and vanished from the universe (except for their bones and descendants)?
Or are they still moving and inhabiting the earth in their region of the 4D space time block and the only reason we can't get back there is because our timeline won't curve enough to take us back? — prothero
Dinosaur world-lines exist in the distant past. — Inis

And that just seems to be a deliberate dodge of the question. The eternalist stance (as I understand it is the past, the present and the future all have equal ontologic status. They all exist and are real in the same manner.
The problem is virtually no one actually believes that. It arises from treating time as just another physical dimension and then drawing block diagrams to illustrate ones passage through the time block. Which is a useful tool (just like train routes on a map) but no more represents the actual passage than the line a train will take drawn on a map is of the actual train ride.. One can not empirically directly demonstrate the continuing reality of the past. It is all a fallacy of misplaced concreteness mistaking a mathematical formula (always an abstraction and idealization and which fails at the extremes) for reality itself. One cannot derive the concrete from the abstract in its full measure.

And that just seems to be a deliberate dodge of the question. — prothero

Your question is answered.

The eternalist stance (as I understand it is the past, the present and the future all have equal ontologic status. They all exist and are real in the same manner. — prothero

But not at the same time, or the same place..

The problem is virtually no one actually believes that. — prothero

If you've studied relativity (and quantum mechanics) eternalism is inevitable. Many physicists don't like that for religious reasons, which is why they try to invent new physics.

One can not empirically directly demonstrate the continuing reality of the past — prothero

How do you empirically directly demonstrate the momentary reality of the present?

Then choose another word to refer to what I'm describing, else we cannot communicate. — noAxioms

How about we say that things interact with each other, but interacting things do not necessarily measure each other. Otherwise we'd have no difference between interacting with something and measuring something. Measuring is a special activity of comparison which human beings with minds do. Things which interact with each other are not necessarily gather information into one point. Do you know what it means to gather information? Or are you just making up a nonsense definition of that, to go along with your nonsense definition of measurement?

The rock is doing a comparison of photon detected vs photon not detected. The state of the rock is different depending on this comparison. — noAxioms

So the rock compares it's own state prior to its interaction with the photon to its own state posterior to its interaction with the photon? That requires a memory. The day you find a rock capable of doing that comparison, let me know.

You say that the concept of motion is available to eternalists, but it seems logically incoherent to me. You claim that motion or change can(?) happen in the past or in the future, but it fails to explain when anything actually happens in the block universe. — Luke

I don't understand your question. Again, motion is change (specifically, of position, or more generally, of any property) over time. How is this a problem for eternalism? There are timelines, and there are properties that change along those timelines. What, specifically, is incoherent in this picture?

Future events already exist, so have they already happened? — Luke

You are just needlessly confusing yourself with this existence business. Like I said, I don't see much use for it, but if you insist on talking about it, just think logically. Every event in a block universe has a spacial and a temporal coordinate: (x, t). So if you ask when an event exists, the only sensible answer is the obvious one: it exists at t. Just as if you ask where it exists, the answer would be x.

How about we say that things interact with each other, but interacting things do not necessarily measure each other. — Metaphysician Undercover

Interaction implies two way relationship, so perhaps a 1-way interaction.

The moon is a poor example since we're in the gravitational field of the moon at all times and it is impossible for it not to be there, even if hidden behind a curtain. A specific state can be collapsed to us only after at least a second, but the moon in general cannot cease existence just by no longer looking at it, so to speak.

Measuring is a special activity of comparison which human beings with minds do.

You're describing a different dictionary definition of the word. A QM measurement is nothing of the sort, unless you ascribe to the Wigner interpretation I guess. I'd rather not limit myself to such a solipsistic interpretation of QM. Even Wigner himself bailed on support of his own interpretation for that reason.

Things which interact with each other are not necessarily gather information into one point. Do you know what it means to gather information? Or are you just making up a nonsense definition of that, to go along with your nonsense definition of measurement?

I don't think I used the term 'gather information' so far.

So the rock compares it's own state prior to its interaction with the photon to its own state posterior to its interaction with the photon? That requires a memory. The day you find a rock capable of doing that comparison, let me know.

You make comparison sound like a decision. I'm just saying that the rock is in a different state with the photon than it would be without (or with a different) photon. It doesn't make a comparison between those two states. Nothing can since any system has access to only one of the two states.
Rocks have great memory. Ask the geologists. But that is on a classic scale. From a QM standpoint, all matter has perfect memory, hence physics' conservation of information principle. There, now I've used the term 'information', but the physics definition, not the one you're using.

Anyway, I think we cannot communicate on this subject. You insist on the everyday language meaning of my words and not the physics ones.

It doesn't make sense for the presentist to think of the past as being immutable, for the presentist does not interpret his memories as referring to anything transcendent of his volatile world of experience, and he surely appreciates that his memories change over time.

And if the presentist also denies the second law of thermodynamics as constituting a direction or orientation of the present, then time-travel into the past or future could be seen as being nonsensical in virtue of experience not being linearly ordered.

Interaction implies two way relationship, so perhaps a 1-way interaction. — noAxioms

I can't see how a 1-way interaction could be possible. How could one thing have an effect on another, without itself being affected? But a two way relationship does not imply measurement.

You're describing a different dictionary definition of the word. A QM measurement is nothing of the sort, unless you ascribe to the Wigner interpretation I guess. I'd rather not limit myself to such a solipsistic interpretation of QM. Even Wigner himself bailed on support of his own interpretation for that reason. — noAxioms

A QM measurement is clearly a comparison. I don't know how you can think that it's not. There's an experiment and the results are compared to standards, mathematics is applied, to produce a conclusion which constitutes the measurement. The equipment is like any other measurement tool, it doesn't just sit there and give a measurement. Whatever it gives must be interpreted according to a standard (compared), in order that there has been a measurement. Consider a thermometer. It sits there and produces a reading, a number. But that number is meaningless, it's not a measurement until it's put into the context of a scale, K, C, or F. Then, in comparison to this scale, the number recorded has meaning as a measurement.

An interaction not only needs to be recorded (remembered), but it also needs to be compared to a scale in order that it be measured.

You make comparison sound like a decision. — noAxioms

It is a decision, that's what measurement is, it's a matter of deciding which things to compare to which scales, to get a valid measurement. You wouldn't compare a thermometer reading to a colour chart, to see if 30 degrees is green or red, rather, you'd compare it to a temperature chart to see if it's warm or cold..

Rocks have great memory. Ask the geologists. But that is on a classic scale. From a QM standpoint, all matter has perfect memory, hence physics' conservation of information principle. There, now I've used the term 'information', but the physics definition, not the one you're using. — noAxioms

I actually know quite a few geologists and none of them talk about rocks having memory.

Anyway, I think we cannot communicate on this subject. You insist on the everyday language meaning of my words and not the physics ones. — noAxioms

I think that the real problem here is that you make up nonsense meanings for words and then you pretend that these are the meanings which the words have in physics. I happen to know some physicists too.

I don't understand your question. — SophistiCat

Which question?

Again, motion is change (specifically, of position, or more generally, of any property) over time. How is this a problem for eternalism? — SophistiCat

Motion is a problem for eternalism because temporal passage is an illusion according to eternalism. Without passage through time, there can be no motion. How do we get from one time to the next?

There are timelines, and there are properties that change along those timelines. What, specifically, is incoherent in this picture? — SophistiCat

It seems odd to call it "change" when nothing actually changes. Everything just exists. There is nothing to transport us from one time to another. Temporal passage is an illusion. There is no motion.

You are just needlessly confusing yourself with this existence business. — SophistiCat

The disagreement between us seems to be that you (and some others) are speaking from a physics point of view, whereas I am speaking from a philosophy of time point of view. In philosophy of time, eternalism is an ontological theory (about existence) which says that all times equally exist and objective temporal passage is an illusion.

I have been trying to convince you that motion is not possible for eternalism purely as a logical consequence of the principles of eternalism, but since that doesn't seem to be working, take a look at the online article I posted, or the articles that recently posted. I thought we would be discussing things in terms of philosophy of time since this is a philosophy forum.

Like I said, I don't see much use for it, but if you insist on talking about it, just think logically. Every event in a block universe has a spacial and a temporal coordinate: (x, t). So if you ask when an event exists, the only sensible answer is the obvious one: it exists at t. Just as if you ask where it exists, the answer would be x. — SophistiCat

I never asked you when or where an event exists; I asked you to explain how anything can happen in a block universe, in which temporal passage is an illusion and everything already exists at all times. Perhaps you could finally address my questions regarding this illusion.

Motion is a problem for eternalism because temporal passage is an illusion — Luke

Simply false. Eternalists have clocks.

It seems odd to call it "change" when nothing actually changes. — Luke

Eternalists have clocks and change happens.

The disagreement between us seems to be that you (and some others) are speaking from a physics point of view, whereas I am speaking from a philosophy of time point of view. In philosophy of time, eternalism is an ontological theory (about existence) which says that all times equally exist and objective temporal passage is an illusion. — Luke

Eternalism doesn't claim that, though. The fact that all times are equally real does not preclude passage from one time to another.

Eternalists have clocks. — Inis

So what? Eternalists claim that temporal passage is an illusion.

Eternalism doesn't claim that, though — Inis

Prove it. I'll go first:

Eternalism is a philosophical approach to the ontological nature of time, which takes the view that all existence in time is equally real, as opposed to presentism or the growing block universe theory of time, in which at least the future is not the same as any other time. Some forms of eternalism give time a similar ontology to that of space, as a dimension, with different times being as real as different places, and future events are "already there" in the same sense other places are already there, and that there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time. — Wikipedia

So what? Eternalists claim that temporal passage is an illusion. — Luke

No they don't.

Prove it. I'll go first: — Luke

You are conflating "passage of time" (which is measured by clocks) with the wikipedia expression "objective flow of time" (which doesn't exist).

There is no flow of time. This has been dealt with in this or recent similar threads. It is an incoherent misconception that does not bear scrutiny. It doesn't even work under presentism. What is this flow supposed to be relative to?

No one, other than you, thinks that the static block universe precludes clocks, motion, change. Given that time is one of the dimensions of the block, to claim that time doesn't exist in the block, seems somewhat absurd. If someone were to claim that one of the spatial dimensions did not exist, that it was an illusion, you would think they were joking. You're not joking are you?

What is this flow supposed to be relative to? — Inis

I don't buy your distinction. What is the passage of time supposed to be relative to? And where is your proof?

If someone were to claim that one of the spatial dimensions did not exist, that it was an illusion, you would think they were joking. — Inis

I never said there was no time, but eternalism says there is no passage.

I don't buy your distinction. What is the passage of time supposed to be relative to? And where is your proof? — Luke

There you go again. Time is a dimension of the block universe. Clocks measure the passage of time, in their reference frame.

You claimed that there is an objective flow of time. What is this flow relative to?

I never said there was no time, but eternalism says there is no passage. — Luke

Tediously false.

Clocks measure the passage of time, in their reference frame. — Inis

Why couldn't the same be said about the flow of time? What makes that an "incoherent misconception"?

You claimed that there is an objective flow of time. — Inis

I never made this positive claim. The Wikipedia article states that there is no objective flow of time according to eternalism. I take "objective" here to refer to mind independence, not frame independence; that is, as opposed to "subjective".

More proof of my characterisation of eternalism can be found in the article that Walter Pound attached to his post earlier:

We should begin at the beginning: what are the theories of time under dispute here?
In one corner we have the B-theory. The B-theory says: there are times; the
times are structured by the relation x is r seconds earlier than y; this relation gives
time the same order and metric structure as the real numbers. And that is all.
In the other corner we have the moving spotlight theory. The moving spotlight
theory says that the B-theory leaves something out. In addition to the characteristics
the B-theory says time has, there is also this: exactly one time has the intrinsic
property presentness. (Maybe things located at that time and events that occur at
that time also have presentness.) Presentness is the “spotlight” that shines on just
one time. Moreover, which time has presentness changes. Some time has it, but
later times will have it, and earlier times have had it. The spotlight moves along
the series of times at a steady pace. It is this continual change in which time has
presentness that in the moving spotlight theory constitutes the passage of time, or
“objective becoming.” When B-theorists deny that the passage of time is a real
phenomenon they mean to deny that anything like this goes on; there is no such
property as presentness that is instantiated first by earlier and then by later times. — Experience and the Passage of Time - Bradford Skow

The B-theory is often synonymous with eternalism, which is how I have been using it throughout this discussion. According to Skow's article, "B-theorists [or eternalists] deny that the passage of time is a real phenomenon".

Why couldn't the same be said about the flow of time? What makes that an "incoherent misconception"? — Luke

What does time flow relative to?

How fast does it flow relative to this thing?

If it changed speed, or even stopped flowing altogether, would you notice?

Why don't we experience the flow?

How long does the present last for?

All I meant was that the flow of time and the passage of time can be used synonymously. You seem to have some special use for these terms. I use them both to refer to temporal passage. No response to the rest of my post?

ETA: You appear to have overlooked the final sentence of the Wikipedia quote I posted:

...there is no objective flow of time. It is sometimes referred to as the "block time" or "block universe" theory due to its description of space-time as an unchanging four-dimensional "block", as opposed to the view of the world as a three-dimensional space modulated by the passage of time.

You are conflating "passage of time" (which is measured by clocks) with the wikipedia expression "objective flow of time" (which doesn't exist). — Inis

I have to agree with Luke on this one. 'Passage of time' implies flow to the average person, and I don't think the typical eternalist would ever use that term. I wouldn't. Clocks measure duration (length in the temporal dimension), and you seem to equate 'passage' with that, but I don't, and neither does most of the literature, as Luke has been pointing out.

Time travel into the past is coherent, because the past is real. Having actually occurred, — Metaphysician Undercover

Past events occurred. They're no longer occurring. Time is simply change or motion. It's not something you can "travel in." It rather is the traveling so to speak.

Past events occurred. They're no longer occurring. Time is simply change or motion. It's not something you can "travel in." It rather is the traveling so to speak. — Terrapin Station

OK, so if time is simply change, why can't we change what has already occurred then? There must be more to time than simple change, or else we could change what has already occurred.

You mean change something that changed so that it doesn't change that way? How would the idea of that even make sense? It would be an identity violation for one. Remember that time only is those changes. It's not something aside from them.

Once something changes all you can do is change it some other way. You can't "travel in change," the idea of that is just nonsensical .

You mean change something that changed so that it doesn't change that way? How would the idea of that even make sense? It would be an identity violation for one. Remember that time only is those changes. It's not something aside from them. — Terrapin Station

That change is an identity violation is tautological.

You said time is change. There must be something which changes or else there could be no change. The only thing that could change is something which already is, and this is events which have occurred in the past. If it's an identity violation to change something which has already changed, then time is an identity violation. Where's the problem?

You can't "travel in change," the idea of that is just nonsensical . — Terrapin Station

How is the idea of traveling in change nonsensical? Change is all around us, We exist in change. I travel in change everyday. Sometimes I even pay for my travel with change. With free will, why can't we change the change? Or are you determinist?

That change is an identity violation is tautological. — Metaphysician Undercover

I didn't say that change is an identity violation. I said that the idea that we could "take back" something that changed is. Look at what I wrote again: "You mean change something that changed so that it doesn't change that way?" That's what would be an identity violation. Change isn't.

There must be something which changes or else there could be no change. — Metaphysician Undercover

(1) Relations and (2) things could appear or disappear.

How is the idea of traveling in change nonsensical? — Metaphysician Undercover

By not making the slightest bit of sense. You'd have to explain what it would be to "travel in change." Changing isn't the same thing as "traveling in change." Change isn't a place that you can move around in. Change is a process. "Traveling in change" would mean that change is some sort of "thing" that we can move around in . . . which is a difficult idea to even clearly express in words, because it's just completely nonsensical.

Think of it this way, Metaphysician Undercover:

A, B and C change to D, E and F.

You want to propose somehow "traveling back to that change," to experience it again, or to change it some other way, or whatever.

How exactly would it make sense to "travel back to that (particular) change"?

Let's say that all that you really mean is changing D, E, and F back to A, B and C, and then A, B and C change to G, H and I instead. Well, that's just two additional changes. It doesn't somehow erase the initial change. That's was the case regardless. It happened, It can't unhappen.. We just had further changes.

So you'd have to explain how it would make sense to "travel back in change."

I didn't say that change is an identity violation. I said that the idea that we could "take back" something that changed is. — Terrapin Station

How is this different from any type of change? All change is a matter of taking back something that already is. that's just what change is, and it is by definition an identity violation.

You seem to be suggesting that some things have special status. Some things we can change, but others we cannot. What validates that special status of being unchangeable?

Look at what I wrote again: "You mean change something that changed so that it doesn't change that way?" That's what would be an identity violation. Change isn't. — Terrapin Station

I don't see how this is any different from any standard matter of "possibility". The way that something has already changed is only one of the many possible ways in which it could have changed. Why not choose a different way, and make the thing change in that way instead? You simply negate one possibility in preference of another. It doesn't violate identity any more than any case of choosing one possibility over another. The act of changing what has already changed violates its identity, but that's what change does, ipso facto.

By not making the slightest bit of sense. You'd have to explain what it would be to "travel in change." Changing isn't the same thing as "traveling in change." Change isn't a place that you can move around in. Change is a process. "Traveling in change" would mean that change is some sort of "thing" that we can move around in . . . which is a difficult idea to even clearly express in words, because it's just completely nonsensical. — Terrapin Station

Obviously you've got everything backward here, and it's you whose not making sense. We travel in space, and space is not a thing. So your claim that there must be some sort of "thing" for us to travel in, is the opposite of what is the case. "Things" just hinder travel, as being in the way. So if change is a process, and this is a lack of "things", I think it would be the most conducive for efficient travel.

You want to propose somehow "traveling back to that change," to experience it again, or to change it some other way, or whatever. — Terrapin Station

Your premise is that time is simply change. If this is the case, then there is no difference between changes which have not yet occurred, and changes which have already occurred. We can consider each, future change and past change, as a possibility of change, and act accordingly, whether we like or dislike those possible changes.

How exactly would it make sense to "travel back to that (particular) change"? — Terrapin Station

In the very same way that it makes sense to travel toward a possible change in the future, it also makes sense to travel toward a possible change in the past, if time is simply change, which is your premise.

Let's say that all that you really mean is changing D, E, and F back to A, B and C, and then A, B and C change to G, H and I instead. Well, that's just two additional changes. It doesn't somehow erase the initial change. That's still there. We just had further changes.

So you'd have to explain how it would make sense to "travel back in change." — Terrapin Station

I don't know what you mean here. If G, H, and I are chosen instead of D, E, and F, then D, E, and F, are possibilities which are not actualized. It's not a matter of erasing these possibilities, it's a matter of choosing other possibilities instead.

How is this different from any type of change? All change is a matter of taking back something that already is. that's just what change is, and it is by definition an identity violation. — Metaphysician Undercover

Let's say that A is five feet to the right (from perspective x) of B.

They move relative to each other, so that A is now six feet to the right of B.

Now, no matter what we do, A was five feet to the right of B . We can't change that fact. We also can't change the fact that A is now six feet to the right of B. And once more changes happen, we can't change the fact that A was six feet to the right of B.

What you tried to propose was via later changes, that we can somehow "travel" to A being five feet to the right of B and change things so that A, say, stays five feet to the right of B, and never moves six feet to the right of B. That's an identity violation in the sense that you're trying to "erase" the fact that A was six feet to the right of B.

And you'd need to explain how you could travel in change . . . which maybe you tried to do later in the post, but I didn't and won't read past what I quoted.

One thing at a time if you don't want stuff you type to be ignored.

Now, no matter what we do, A was five feet to the right of B — Terrapin Station

Your premise is that time is change. So "was" in the sense of "past time" is meaningless by that premise. You have nothing to differentiate past change from future change. All we have is either A is five feet to the right of B, or A is not five feet to the right of B. And either of these can be changed through time, which is change.

If you want to introduce a premise which states that something which has occurred in the past cannot be changed, then you need to allow that time is more than just change. You need a premise which gives past changes special status over future changes, as being unchangeable.

Your premise is that time is change. So "was" in the sense of "past time" is meaningless by that premise. You have nothing to differentiate past change from future change. All we have is either A is five feet to the right of B, or A is not five feet to the right of B. And either of these can be changed through time, which is change.

If you want to introduce a premise which states that something which has occurred in the past cannot be changed, then you need to allow that time is more than just change. You need a premise which gives past changes special status over future changes, as being unchangeable. — Metaphysician Undercover

I don't think you need a notion of "past change" in order to hold that when you change 1)A to B, 2)B to A and then 3) A to B again 1) is not identical to 3), unless the state you change is the state of the entire universe. Because under that condition, 1) happens in a different universe from 3), and so the full descriptions of the states would not be identical. If you did change the entire state of the universe, then you would time travel, but since this presumably includes your internal state, you wouldn't notice.