when you analyze this proposition there is nothing to make the boundaries between one frame and the next. — Metaphysician Undercover

The concept of boundary only makes sense in a continuum. It makes no sense for elements of a discrete set. If time is discrete there is no continuum, so the concept of boundary is meaningless.

If you find this notion difficult, consider another type of discrete thing like minds. What could be meant by the boundary between my mind and your mind?

Good point. Change is also analytic to space; for much the same reasons.

Perhaps change is the marker for dimension. Or is it position that changes?

The concept of boundary only makes sense in a continuum. It makes no sense for elements of a discrete set. If time is discrete there is no continuum, so the concept of boundary is meaningless. — andrewk

Not only does it make sense, but it is absolutely necessary. What makes the members of a discrete set discrete is the fact that they are isolated from one another. The thing which isolates one from the other is what I called a boundary. If Y and Z are discrete units of time there must be something real in between them, which isolates one from the other, a boundary. If time is discrete, then what would isolate one discrete unit of time from another? We would have to posit a non-time, between each moment of time. But that doesn't make sense because the only thing which could fulfill this condition of "non-time" would be a stoppage of physical activity. But a stoppage requires necessarily, a period of time with no activity. So we end up with the same description, a period of time with no physical activity.

What could be meant by the boundary between my mind and your mind? — andrewk

That's a good example. The boundary between my mind and your mind, is the external world. Boundaries are very real in the spatial world. Though we don't seem to understand them well they are what we sense, so we must hand them some reality if we want to give any credence to empirical knowledge. In the case of time though, we arbitrarily posit points as boundaries. The designated "point in time" separates one unit of time from the next. But there is nothing sensed or otherwise indicating any separation, or differentiation, between one moment and the next. If you believe that time might be discrete, what do you think could possibly separate one moment of time from the next? What gives you any inkling of justification for this proposal?

Thanks, but can you have change apart from space?

As in change of time without change of place?

As in change of thought, viz., moving from one thought to another.

Taking the term "change" from one language game to another. Nothing wrong with that, provided we take care.

If mind is what brain does, changing you mind is a change in space and time.

If Mind is distinct from brain, then not so.

Because if we experience discrete units of time, then we'd have to know in what respect it has continuity to a whole (an event, for example). But this then presupposes there's an in-between the discrete units of time, in which they blend into each other as a continuous flow. Or another thing to ask: in virute of what is this "now moment" related to another time moment? A relation that ulimately presupposes the category of the transitionary.

Jorn, what is your opinion of Shoemaker's claim that time without change is possible? — andrewk

Not sure what to make of it. As thought experiments go it's interesting enough.

If we were to entertain reified abstracts (à la Platonism), then inert, timeless entities exist, along with our temporal, changing world. (Not really my cup of tea, admittedly.)

Could something changeless coexist with something that changes? A free photon?

Well, if all change ceased entirely, and somehow resumed, then what would the difference be, from not having ceased? Doesn't seem like a difference to me.

Either way, with micro-chaos, the universe can't be quiet.

That's related to duration. Simultaneity is also of relevance.

Ya, I can agree with you on that, it seems reasonable enough. I wonder though if simultaneity is a necessary feature of time? My guess is that it's not a logically necessary feature of time, as is change. However, I'm not sure.

Experiencing change is experiencing time - that's what it means to experience time. That's why I said earlier that change is analytic to time - you can't separate the two. — Sam26

I thought we both agreed that you can experience change without experiencing time. Change is change. Time is a measurement of change. You can experience change, but how much time has passed? As I said, you can get lost in your thoughts. Your thoughts change from one moment to another but you don't know how much time has passed until you look at the clock to measure how much time you have been lost in your thoughts.

Time is a measurement of change. — Harry Hindu

This is not a good description of time. Even the thing which is used as a measure, must itself be capable of being measured, or else the measurement made by that thing is arbitrary and meaningless. As Aristotle indicated, in one way, time is what measures, and in another way time is what is measured. Therefore your conclusion that just because one is not using time to measure something then one is not experiencing time, is not a valid conclusion because you neglect the fact that one could be experiencing time without measuring it. The fact that something like time can be measured does not necessitate the conclusion that it must be measured in order to be experienced. Measurement is just a special type of experience.

Sorry Harry, maybe I didn't make myself clear. My point would be that you can experience change without any kind of measurement of change. For example, I could be sitting on my back porch watching the sunset, completely unaware of how much time has passed (in terms of measurement), yet I do know that change has happened and that time has passed. There is no standard as to how much time has passed, it's completely arbitrary. It's true that you don't know exactly how much time has passed while sitting on the porch, but that's a moot point.

I think where I disagree is with your definition of time. Time can exist without any measurement, that is, we can imagine a universe in which there is no intelligent life; and as such, we know that there would be no measuring of time, and yet time would still exist, and as the primary property of time, change would also exist. Moreover, for us to be able to measure change, change would have to exist prior to the measuring. Change doesn't co-exist with the measurement, that is, you wouldn't say that you have no change until you measure it - of course not, we observe the change, and then we produce an arbitrary form of measurement to account for change within our everyday lives.

Simultaneity is dependent on one's frame of reference.

Two events separated by space, but occurring a the same time. Is that different to two events separated by time, but occurring in the same place?

Playing the game using the grammar of physics seems to me the best approach. In which case simultaneity is incidental.

I don't get the fuss over McTaggert's A and B series. They simply are not incommensurable. Any A-series event can be made a B-series event simply by indexing it.

Two events separated by space, but occurring a the same time. Is that different to two events separated by time, but occurring in the same place? — Banno

Yes, I think it's quite obvious that there is a big difference between these two. Prior/posterior is very different from here/there, because the concept of causation is dependent on the former.

But it isn't; they are truth functional equivalent; this is just your failure to understand relativistics

The usual spacetime stuff in brief:

• where: left ↔ right, up ↔ down, forward ↔ backward (indexical "here")
• when: past → present → future (indexical "now" = present)

• same when, different wheres: simultaneity
• same where, different whens: place

• same when, same where: identity (indexical "here-now")
• different when, different where: motion or non-identity

It's common, everyday stuff:

• it takes time to get to work in the morning (duration)
• work is elsewhere (distance)
• we get to work about the same time in the morning (simultaneity) as agreed prior (past)
• we have meetings at work (place)

Figuring out simultaneity, for example, is a matter of applying the Lorentz transformation (or more complex varieties, depending on acceleration/gravity and such). Figuring out duration, so that we can largely agree at least, is a matter of stable quantification across applications, to which physicists have come up with caesium fountain atomic clocks (so far).

Duration and simultaneity together seems to suggest dimensionality of some sort, which goes well with relativity and other contemporary science. Does that suggest a (growing) block universe?

I don't get the fuss over McTaggert's A and B series. They simply are not incommensurable. Any A-series event can be made a B-series event simply by indexing it. — Banno

(Y)

But it isn't; they are truth functional equivalent; this is just your failure to understand relativistics — Banno

"Truth functional equivalent". What does that mean? I happen to know that equivalent and the same are not the same thing. 2+2 is equivalent to 4, but not the same as four. So if you claim that a spatial separation is equivalent to a temporal separation, "equivalent" does not mean that there is no difference between them.

SO where will you go with this - do you agree with McTaggert's argument that time is not real? If so - well, I will answer that later.

There are at least two ways in which we use the word simultaneous. I'll see two events happen and say that it occurred simultaneously, however, we know it's not true given very precise measurements. So in terms of the language-game in which we use the word simultaneous, that is, in everyday usage, it's quite correct for us to say that some event occurred simultaneously. The precision of science is just not that important when saying "John and Mary arrived simultaneously." We have two different language-games, and we should point out that the use of the word has very different functions in each. If you were to argue with someone, and point out that John and Mary didn't arrive simultaneously, they would probably wonder what you were smoking - especially if they came in the door at the same time. And even if you were doing very precise measurements, an event X can seem to occur simultaneously from one point of view, and not from another.

I found an interesting video here http://highexistence.com/this-will-mindfuck-you-simultaneity-is-relative/

Error can be measured. John and Mary arrived simultaneously to an accuracy of five minutes, but to an accuracy of a few seconds, John arrived first.

Yes, I know, but that's not the point. The point is that when we say that people arrived simultaneously, we generally are not saying that it's an exact measurement. Like when we say "Stand here," it's generally used in a rough sense. We don't take precise measurements.

SO where will you go with this - do you agree with McTaggert's argument that time is not real? If so - well, I will answer that later. — Banno

I don't know McTaggart's argument, but I believe that time is real. I base this on the knowledge that there is a real difference between future and past.

, in the link, observer A found the lightning strikes occurred simultaneously, and observer B found they didn't.
However, after applying the Lorentz transformation, they both agree on that (their different observations).
Check Relativity of simultaneity » Einstein's train thought experiment (Wikipedia article).
By physics, simultaneity is meaningful for reference frames, not universal as such, and the Lorentz transformation tells us how it differs among reference frames.
Exactitude is a different problem.

Might be worth noting that retro-causation remains impossible according to relativity:

if the two events could be causally connected (i.e. the time between event A and event B is greater than the distance between them divided by the speed of light), the order is preserved (i.e., "event A precedes event B") in all frames of reference — https://en.wikipedia.org/wiki/Relativity_of_simultaneity#Explanation

What does the "is" mean then, if not that it exists in the present tense? Either something is, was, or will exist so in what other way is the block universe said to "exist"? — Alec

I'm thinking it just means that our language can be confusing. We're not accustomed to tense-less chat. So, the block universe = what was, what is, and what may yet come to be.

We have (possibly confusing) double-temporal proposition propositions like “it is true now, that it rained the other day”.

I don't get the fuss over McTaggert's A and B series. They simply are not incommensurable. Any A-series event can be made a B-series event simply by indexing it. — Banno

You will also have to ignore the tensed nature of the A-series, so no you cant just index an A-series.

I'm thinking it just means that our language can be confusing. We're not accustomed to tense-less chat. So, the block universe = what was, what is, and what may yet come to be. — jorndoe

How about the Block = what was, what is, and what will be?

There is no "may" in the Block.

I'm thinking it just means that our language can be confusing. We're not accustomed to tense-less chat. — jorndoe

I am not sure what you mean by "tenseless chat". Under the block universe, every time "is" real. What does the "is" mean here? Does it mean that it was or will be, that they ceased to exist or will come to exist? Certainly not, since that means they don't exist. Or perhaps it means just what we normally mean by the term, that they all currently exist in the present tense.

So, the block universe = what was, what is, and what may yet come to be. — jorndoe

I think a better way to say it is that the block universe = Every event in the universe's history. This would include things like the Big Bang, the earth at 2017, and the Martian Outposts in 2100. We speak purely in terms of the particular contents instead of using confusing descriptions like "the things that were" or "what will be", which have a particular meaning to them. To me, under the block universe, every one of these events just "is" in the present tense. The events that we normally take to have existed or will exist actually currently exist somewhere in our universe, though of course not in the same 3D timeslice as our own.

I think the lesson from relativity is that time as a dimension functions a lot like space. That is not to say that time is exactly like space, but that time as a dimension designates locations just like space does. Napoleon didn't cease to exist, he just exists "over there" somewhere in the block universe the same way I say that the planet Pluto exists "over there" somewhere in space.