Frame of Reference as Subject in Subjective Idealism

[owl]

You are still conflating light delay (the time it takes for us to see things) with relativity of simultaneity. The eight-minute delay in the travel of light from the Sun to the Earth has absolutely nothing to do with relativity of simultaneity as presented in special relativity.

 

In my example, what is happening in the railcar depends exactly upon whether you're moving relative to it.

 

Your dictum has been to measure events in the frame in which they are at rest -- e.g. events are simultaneous when you're standing on the railcar, in its reference frame, so they must remain simultaneous. What if the two walls of the car are moving in different directions? How do you decide which reference frame is correct?

I would move to stay equidistant between them and stay on the train to minimize the variables for my measurement. But I have a feeling that this is beside your point. And you have not addressed my pursuit of understanding constant lightspeed as logically requiring the relativity of simultaneity.

Me, again:

Please detail the logic from, “The speed of light is constant" (agreed) to "the relativity of simultaneity." (I disagree.")

I said;

We know that things happening at the same time in different locations are not simultaneous for observers in different FORs. This is why you say that simultaneity is relative. But they are still simultaneous regardless of from where and when they are observed. ... (etc.)

You replied:

You are still conflating light delay (the time it takes for us to see things) with relativity of simultaneity. The eight-minute delay in the travel of light from the Sun to the Earth has absolutely nothing to do with relativity of simultaneity as presented in special relativity.

Please show me the difference, i.e., how exactly I am conflating, as above.

Again:

Will you please address my take on simultaneity above in equally clear English. Then maybe we can move on to your conclusion as pertains to length contraction.

 

Rather, you change the situation, before the above is resolved, as with:

What if the two walls of the car are moving in different directions? How do you decide which reference frame is correct?

 

Schrodinger's hat:

The angular size of the moon is part of reality. It's not subjective,

But it does depend on the FOR from which it is measured.

You continue to ignore my illustration that the world (cosmos, moon, the space/distance between Earth and Sun, etc.) exists independent of observation and measurement from different FORs.

 

Your complex FOR exercises totally avoid my above argument for realism. "The world" does not depend on how we look at it for its intrinsic reality.

 

Edit, replying to your:

There is a concept known as proper distance which is invariant. Ie. Earth's proper radius if you assume it's not spinning (or is spinning so slowly that it doesn't matter -- which is true) and ignore GR is: 6370 km

For a realist, looking at the concrete example of Earth as seen from the space station, for instance, its spinning is irrelevant, no matter how slow or fast. We can see the whole Earth in profile, and it appears as a disk with a mean radius of 6371 km.

From an extreme FOR, as discussed to death here, it may appear as 1/8th of that, but the real Earth stays very close to a 6371 km diameter, and the 'squished Earth' observation/measurement, if there were one, which there is not...would be a gross error.

Edited September 16, 2011 by owl

[Schrödinger's hat]

But it does depend on the FOR from which it is measured.

You continue to ignore my illustration that the world (cosmos, moon, the space/distance between Earth and Sun, etc.) exists independent of observation and measurement from different FORs.

 

So you're angular sizes are not part of reality?

According to my model, the angular size of the moon from London exists whether or not there is a person there to measure it. It's just that one of the parameters required to fully define an angular size is position.

 

In the same way we have been trying to explain that (according to SR) one of the parameters required to define a distance is velocity.

Proper distances are defined with the implicit statement 'the velocity of this thing is 0'.

 

If you are trying to say that distance being in the same category as angular size means that we are somehow saying reality is subjective then we may finally have grounds on which to start an actual philosophical discussion.

For a realist, looking at the concrete example of Earth as seen from the space station, for instance, its spinning is irrelevant, no matter how slow or fast. We can see the whole Earth in profile, and it appears as a disk with a mean radius of 6371 km.

 

Let's just ignore the issue of rotation for a good long while, it makes things too complicated, and I do not understand all the consequences of using a rotating frame.

At any rate anything we encounter/think of will not be spinning fast enough to matter.

 

You continue to ignore my illustration that the world (cosmos, moon, the space/distance between Earth and Sun, etc.) exists independent of observation and measurement from different FORs.

 

I continue to fail to understand the point you were trying to make and how it pertains to special relativity.

We appear to be making progress on the other matter, so maybe we can come back to it in a few posts.

 

From an extreme FOR, as discussed to death here, it may appear as 1/8th of that, but the real Earth stays very close to a 6371 km diameter, and the 'squished Earth' observation/measurement, if there were one, which there is not...would be a gross error.

I was discussing proper length.

If someone were to make some measurements of the length of earth, then make the corrections to calculate the proper length, he would always get 12740km* no matter which frame he was in.

 

 

*(rounded, diameter is twice radius, the 6370 figure was radius rounded to 3 non-zero digits because earth is very-slightly-oblate in all frames, and the uncertainty from this is in the 10s digit)

Edited September 16, 2011 by Schrödinger's hat

[Cap'n Refsmmat]

I would move to stay equidistant between them and stay on the train to minimize the variables for my measurement. But I have a feeling that this is beside your point. And you have not addressed my pursuit of understanding constant lightspeed as logically requiring the relativity of simultaneity.

If the speed of light were not constant in all reference frames, we would find that the light strikes the walls simultaneously in all reference frames:

 

 

Here you see the light moving at different speeds, since it's launched on a moving train; the light in the direction of travel goes faster, and the light intersects the walls simultaneously. This is what we'd see with bullets or model airplanes.

 

Light, however, behaves differently, as you could see in the diagram where the light reaches the wall at different times. This is solely because of its constant speed in all reference frames.

 

The constant speed of light necessarily means that certain events can change order -- i.e., one that appears first in one reference frame can appear second in another. After all, I could draw the train moving in the other direction (or observe the train from a car driving past it very fast) and see the light reach the left wall first, rather than the right.

 

The interesting thing about this is that causality is always conserved; reordering events cannot create paradoxes.

 

Please show me the difference, i.e., how exactly I am conflating, as above.

There is a difference between "I saw the explosion as happening eight minutes later, since the explosion was very far away and the light didn't reach me" and "the events are no longer simultaneous, even when I compensate for the light delay."

[Schrödinger's hat]

There is a difference between "I saw the explosion as happening eight minutes later, since the explosion was very far away and the light didn't reach me" and "the events are no longer simultaneous, even when I compensate for the light delay."

Maybe you could make it clearer by adding some return-journey light lines to your diagram, point out when/where the me sees them and when/where a (or two) observer(s) on the tracks do(es)?

[owl]

So you're angular sizes are not part of reality?

According to my model, the angular size of the moon from London exists whether or not there is a person there to measure it. It's just that one of the parameters required to fully define an angular size is position.

My argument (realism) is that reality does not depend on how we see or measure it. I had hoped you could imagine an earth, sun moon, etc., and their relative positions existing and having intrinsic properties as if there were nobody looking at them or the distances between them from different FORs. That would make my point.

 

If I take a pancake and turn it on edge, it will look like a fat line, not a disk. But it remains the same pancake, regardless of the angle from which I observe it.

Same applies to relativity's FORs. Reality stays the the same (in this context... though everything is moving) regardless of how you look at it. That IS my philosophical point, and it negates "length contraction."

 

In the same way we have been trying to explain that (according to SR) one of the parameters required to define a distance is velocity.

Proper distances are defined with the implicit statement 'the velocity of this thing is 0'.

 

How fast something is going does not make the distance traveled shorter, just the time it takes to get there. (In all these statements, "according to realism" is implied.)

 

If you are trying to say that distance being in the same category as angular size means that we are somehow saying reality is subjective then we may finally have grounds on which to start an actual philosophical discussion.

 

I'm saying that the distance to the sun doesn't change with how you look at it, and that a pancake doesn't change shape when you look at it on edge, even though it appears to do so.

 

I was discussing proper length.

If someone were to make some measurements of the length of earth, then make the corrections to calculate the proper length, he would always get 12740km* no matter which frame he was in.

Earth doesn't change shape with how you look at it. We all know that it bulges just a bit at the equator. Polar diameter is about 7900 miles, and equatorial diameter is about 7927 miles (just for a change of units.)

 

If the speed of light were not constant in all reference frames, we would find that the light strikes the walls simultaneously in all reference frames:

 

 

Here you see the light moving at different speeds, since it's launched on a moving train; the light in the direction of travel goes faster, and the light intersects the walls simultaneously. This is what we'd see with bullets or model airplanes.

 

Light, however, behaves differently, as you could see in the diagram where the light reaches the wall at different times. This is solely because of its constant speed in all reference frames.

I have agreed (several times) that the speed of light is constant, not effected by the speed of its source or of its observer(s.) I have even used the bullet from a moving gun illustration of the difference.

 

The constant speed of light necessarily means that certain events can change order -- i.e., one that appears first in one reference frame can appear second in another. After all, I could draw the train moving in the other direction (or observe the train from a car driving past it very fast) and see the light reach the left wall first, rather than the right.

 

The interesting thing about this is that causality is always conserved; reordering events cannot create paradoxes.

 

Still no argument against. Still doesn't address my assertion from realism that what is happening in the real world does not depend on the FOR from which that happening is observed. See my "jousting lasers experiment" on a one Au "track." I accurately stated what both jousters saw when and where on the track, which stayed the same length. Point: An over-all view of the whole situation does not depend on the individual FORs of the players.

 

There is a difference between "I saw the explosion as happening eight minutes later, since the explosion was very far away and the light didn't reach me" and "the events are no longer simultaneous, even when I compensate for the light delay.

 

Events happening right now are simultaneous no matter where they are happening or how long it takes any observer anywhere to see them. Simultaneity in the real cosmos does not depend on the FOR from which events are observed.

Edited September 17, 2011 by owl

[md65536]

Events happening right now are simultaneous no matter where they are happening or how long it takes any observer anywhere to see them. Simultaneity in the real cosmos does not depend on the FOR from which events are observed.

That's an interesting conjecture! If you can demonstrate that it's true, then relativity will be in trouble and you'll have a base to begin proving the rest of your statements. All it needs is a bit of evidence or logic to show that it's true.

 

Meanwhile you have several people trying to prove to you that it's logically not true, given an acceptance of a constant speed of light in all inertial reference frames. I suppose that if you can show that universal simultaneity is true, it should suggest a way to punch a hole in their arguments.

 

It took 18 pages, but I have a good feeling that we're getting close to the start of a productive conversation! Keep it up! Almost there!

 

 

[Cap'n Refsmmat]

Er.

 

"Events happening right now are simultaneous no matter what."

 

"Okay, here's an example where changing reference frames causes events to no longer be simultaneous."

 

"Makes perfect sense. Nevertheless, events happening right now are simultaneous no matter what."

 

Perhaps you should elaborate further on the evidence for your claim.

 

I'm not particularly impressed by your own contrived example, since it's easy to create an example that follows your rules, not relativity's.

[owl]

I'm gone again for the weekend. Maybe "Is-ness" is just too simple to understand once one is convinced that everything everywhere and every-when depends of frame of reference and denies simultaneity because of the time lag for info about what is happening now elsewhere. "Is," the present, happening now has no logical location boundaries. Light, of course conveys images and information over distances at 'C' velocity, so we can not know what is happening now elsewhere until we see it or get the info. But I am repeating.

See y'all Monday.

[Cap'n Refsmmat]

I'm gone again for the weekend. Maybe "Is-ness" is just too simple to understand once one is convinced that everything everywhere and every-when depends of frame of reference and denies simultaneity because of the time lag for info about what is happening now elsewhere.

Where did you get the idea that the time lag for information about events is what causes relativity of simultaneity, or even has anything to do with it at all?

[Iggy]

and where did you hear that simultaneity is relative to location,

 

Events happening right now are simultaneous no matter where they are happening

or that nothing is invariant,

 

everything everywhere and every-when depends of frame of reference

Relativity is nothing like the blithering nonsensical strawman for which you mistake it.

[tar]

Cap'n,

 

I slept on it twice...and it's as clear as mud...still.

 

If the speed of light were not constant in all reference frames, we would find that the light strikes the walls simultaneously in all reference frames:

 

 

I am thinking that "simultaneity" is the culprit here. One's definition of it, defines the conclusions that follow.

 

Often in this thread, Owl and I have been thought to "not understand" SR, when we speak of an "objective" now, that defines similtaneity. This "real" now that he and I and I entertain is very "unreal" in that it can only be imagined, and proven to be the case later. Much unlike instruments and recording devices, that rely completely on what is happening here AND now.

 

In many experiments and diagrams, several or a large number of observers are set on a stage, as if we can see the whole performance at one time, from one place, and time, one perspective, from which we can make our observations, design our formulae, apply our assumptions, and derive our conclusions. That this, which is thought to be similtaneous is not, because a high speed traveler would not see it that way...etc.

 

While both Owl and I agree that this is the case, we hold on to the thought that there is a universe that exists NOW, everywhere, that has done everything that has led up to, and caused NOW, but has not yet done the things it is going to do next.

 

"Here and Now" on the other hand, is a purely subjective experience. An observer, such as a TAR2 sees the entire universe, but not in its "NOW" condition. Only GOD, or an observer given godlike powers of knowledge of all "heres" at one time, can know what the universe is doing NOW. But that is not how the universe can be viewed, BECAUSE of photon lag.

 

When we talk of similtaneity, we should be clear on which of the two nows we are speaking of. The one we see, or the one we imagine to exist, because we know from experience that we will see it, once the photons or slower effects reach us.

 

In various examples, and various posts the term "similtaneous" is used, and it seems quite likely that we are not all in agreement with what "now" we are considering, or what "now" we think the other is misunderstanding the nature of.

 

Regards, TAR2

 

Schrödinger's hat

 

Well I guess if SR is the best we have, its probably a pretty good deal. I am just trying to grasp what it "means".

 

After all, any observer would have to report back its findings to a central observer, for the central observer to determine indeed what had exactly happened where and when. But this report would come no faster than light. The report can not be made at the speed of thought. It would arrive in "real" time.

 

And I still have my question, and the question of this thread, in terms of what a particular person considers the "objective" universe, that "IS" this way or that. The jumps between the map and the territory are made very readily, and I am not yet clear on the conventions, and where there is agreement, and where there is misunderstanding or room for discovery.

 

I base my reluctance to consider myself simply ignorant, on the fact that certain cosmologists or physicists might make a determination that the universe IS a certain way. This seems to me to be obviously incorrect from the point of view of an observer which can not know anything about the whole universe except the past parts of it, arriving here, now, and the record of the past parts of it that have continued to arrive here before. (sorry, that's pretty confusing. Don't really expect anybody to follow that.)

 

But we have a couple of ways to "take" Alpha Centuri. Is it the "real" Alpha Centuri that we see? It's probably the one and only Alpha Centuri, but its only the "image" that we see, and it's a 4.5 year old image, and Alpha Centuri has done 4.5 years worth of "being" Alpha Centuri in the mean time.

 

Which Alpha Centuri is real, now? The one that is with us now, by virtue of our experience of it, or the one we know exists now, but that we cannot see but in our imaginations?

 

Regards, TAR2

Edited September 18, 2011 by tar

[Iggy]

Since the Captain just said this and it can't seem to be reiterated enough... Signal delay, or "photon lag" is not the cause of the relative nature of simultaneity. The existence of a constant speed causes it. It doesn't matter that light happens to travel that constant speed or that we happen to use light to see. It is the invariant nature of the speed itself that leads logically to relativity.

 

If we did not have eyes and all of our measurements about the world came from bouncing solid metal pellets off of things and catching them when they return, we would still be able to derive the fact that simultaneous events in one frame are not simultaneous in another because the velocity of the pellets would add according to the Lorentz transformations. We would be able to find out that there is a constant speed and we would know its true value ([latex]c[/latex]). We would not think that the speed of the pellet is constant just because we use them to see and they take time to get around.

 

"Simultaneous" means "at the same time". That is all it ever means.

[tar]

for instance, the cosmic background radiation, often considered an image of the universe when it just became transparent to photons, actually is possibly also a 13.whatever billion year old image of a large number of Alpha Centuri like stars in Galaxies and strings of Galaxies much like what's "around here" now. But that is only the "real" universe considered from a godlike point of view.

The actual universe is the way it looks now to us, for any observer. Close stuff recent and fully evolved, far away stuff younger and further in the past, as you go.

 

There is no platform, or viewer that can experience it, or know it, any differently than the way we do.

 

So which is the real, objective universe? Or is it the both?

 

Iggy,

 

"Simultaneous" means "at the same time". That is all it ever means.

 

But it also means "arriving at the observer's location at the same time". This is not the now that every location is experiencing presently.

 

Regards, TAR2

 

(have to go to sleep)

[Iggy]

So which is the real, objective universe? Or is it the both?

You are catching yourself in a false dichotomy. Try the analogy that Schrodinger's Hat makes. What is the distance to the earth? I understand that "from the moon's perspective" the distance to the earth is 390 thousand kilometers and I understand that "from the sun's perspective" the distance to the earth is 150 million kilometers, but what is the real universal distance to the earth?

 

You understand and agree that as far as "the distance to the earth" is concerned there doesn't need to be a 'single', 'real', 'universal' value for the universe to be real and objective, yes? The same thing goes for velocity and kinetic energy. The earth doesn't have a single, real, velocity from some godlike perspective. It has one velocity compared to the sun and another compared to the milky way and another compared to the Andromeda galaxy. It doesn't need a universal velocity presided over by god for the universe to be objective. You agree, yes?

 

So why does your mind beg you to say that events need a single universal order? The evidence is overwhelming against the idea and I've heard no reason to even suspect that simultaneity, time, and distance are different from velocity, momentum, and other frame dependent quantities.

 

But it also means "arriving at the observer's location at the same time". This is not the now that every location is experiencing presently.

No -- that is not the definition. If two trains, or two birds, or two rays of light arrive at a location at the same time then they arrive simultaneously. This does not mean that the trains, or birds, or rays of light must have left their points of origin simultaneously.

 

If a supernova happens in the Andromeda galaxy and we observe it here on earth 2.5 million years later no one would say that the star goes supernova at the same time that us earthlings observe it -- that the supernova and the observation are simultaneous. Wherever you got that idea it should be put completely out of your mind. Relativity certainly has nothing like that in mind.

Edited September 18, 2011 by Iggy

[Schrödinger's hat]

My argument (realism) is that reality does not depend on how we see or measure it. I had hoped you could imagine an earth, sun moon, etc., and their relative positions existing and having intrinsic properties as if there were nobody looking at them or the distances between them from different FORs. That would make my point.

I can imagine this perfectly well.

The earth, sun, moon etc as they exist over time are all four dimensional objects that exist and have intrinsic properties, no matter which frame they are viewed from.

Taking a few slight liberties with the definition of the word cylinder (Minkowski geometry is not like euclidean and what things are like depends on your choice of embedding), you can imagine something like earth as being a bit like a cylinder.

Each point on earth represents a straight line through space-time, much like the lines in Capn's diagrams. Together the world-lines of any two-dimensional slice of earth would be a cylinder. If you take the world-lines of the entire earth you get the four-dimensional equivalent of a cylinder (a sphere in three directions, extruded along a fourth).

Depending on which velocity or angle you look at this object from, you will see something a bit different.

Our interactions and minds deal in three dimensional slices so at any given time

 

It is by taking the results of this four dimensional model (one of which is length contraction), without taking the model itself that one reaches a contradiction.

The entire study of relativity, especially General Relativity, is based on describing objects and geometries in a way that does not depend on any frame of reference or coordinate system.

It is perfectly possible to use the mathematics and results of relativity without putting time in the same ontological category as space, but then you will have to do one of two things:

1) Create a hugely convoluted model based on an indetectable rest frame (ie. Lorentz Ether). In these models moving things actually do morph and change shape, rather than it being a relic of looking at them from a strange angle.

2) Deny realism

 

If I take a pancake and turn it on edge, it will look like a fat line, not a disk. But it remains the same pancake, regardless of the angle from which I observe it.

Same applies to relativity's FORs. Reality stays the the same (in this context... though everything is moving) regardless of how you look at it. That IS my philosophical point, and it negates "length contraction."

As I said, earth almost exactly like the pancake

Accelerating is almost exactly like turning it on edge.

 

 

Your argument appears to be:

There is a universal and well defined now. (assume presentism)

Assume Realism

Therefore relativity is wrong

 

What you seem to be interpreting our argument as:

There is a universal and well defined now (noone who accepts relativity believes this)

Assume relativity

Therefore there is no realism

 

While ours is:

Assume realism

Assume 100 years of experiments showing constancy of the speed of light and disproving every elegant Ether model are correct

Therefore Relativity is correct and presentism is not.

 

Presentism, realism, constant speed of light, no preferred(unversal still) frame pick three. (we picked the latter three).

Any more are logically incompatable.

 

 

Also you still haven't given me a definition of distance or time that are any better than the ones I had, I'm most interested to hear one that's not tautological.

 

In various examples, and various posts the term "similtaneous" is used, and it seems quite likely that we are not all in agreement with what "now" we are considering, or what "now" we think the other is misunderstanding the nature of.

When the word simultaneous is used it means:

According the the observer of frame that is currently being considered, these events occur at the same time coordinate.

Think of it as the same sort of thing as 'directly in front of'

If I say one cup of coffee is directly in front of another on the table, I mean that according to some reference, they'd be at the same y coordinate.

So unless they are also 'here', you can't see stuff that is 'now' until a while later.

Now will also be a different set of events from different frames.

Well I guess if SR is the best we have, its probably a pretty good deal. I am just trying to grasp what it "means".

 

After all, any observer would have to report back its findings to a central observer, for the central observer to determine indeed what had exactly happened where and when. But this report would come no faster than light. The report can not be made at the speed of thought. It would arrive in "real" time.

 

And I still have my question, and the question of this thread, in terms of what a particular person considers the "objective" universe, that "IS" this way or that. The jumps between the map and the territory are made very readily, and I am not yet clear on the conventions, and where there is agreement, and where there is misunderstanding or room for discovery.

 

I base my reluctance to consider myself simply ignorant, on the fact that certain cosmologists or physicists might make a determination that the universe IS a certain way. This seems to me to be obviously incorrect from the point of view of an observer which can not know anything about the whole universe except the past parts of it, arriving here, now, and the record of the past parts of it that have continued to arrive here before. (sorry, that's pretty confusing. Don't really expect anybody to follow that.)

Often cosmologists use 'just happened' or 'now' in place of 'long enough ago for a signal to reach us now' (eg. the supernova just reached maximum intensity), just to confuse the issue, but it's usually clear from the context.

Sometimes

For predictable objects they often observe past events and then extrapolate to now as well.

But we have a couple of ways to "take" Alpha Centuri. Is it the "real" Alpha Centuri that we see? It's probably the one and only Alpha Centuri, but its only the "image" that we see, and it's a 4.5 year old image, and Alpha Centuri has done 4.5 years worth of "being" Alpha Centuri in the mean time.

 

Which Alpha Centuri is real, now? The one that is with us now, by virtue of our experience of it, or the one we know exists now, but that we cannot see but in our imaginations?

 

Not quite sure how to answer this, to me they're both just as real, along with the Alpha Centauri existing at any other time in the past or future.

To go any further than this I'd have to start discussing Bell's theorem, and the problem of measurement. This requires a decent understanding of quantum physics, and I'm not sure I have learnt enough yet to have a fully coherent philosophy on the matter, let alone communicate that to others.

[tar]

Iggy,

 

No -- that is not the definition. If two trains, or two birds, or two rays of light arrive at a location at the same time then they arrive simultaneously. This does not mean that the trains, or birds, or rays of light must have left their points of origin simultaneously.

 

If a supernova happens in the Andromeda galaxy and we observe it here on earth 2.5 million years later no one would say that the star goes supernova at the same time that us earthlings observe it -- that the supernova and the observation are simultaneous. Wherever you got that idea it should be put completely out of your mind. Relativity certainly has nothing like that in mind.

 

But what of two supernovae that we see at the same time? We call them simultaneous AND as Schrödinger's hat allows, also know that they did not both happen now. This indicates to me, that we are fully capable to both experienc the world AND know what it means in terms of when and where stuff happens. When we collect all the info and fit it together we can build one model of it that has two aspects. One being position/distance/angle from a reference point, and one being causal/timelike from a single timelike reference point. We can automatically do "transforms" by reevaluating our model from another connected here and now and matching up (rotating) our here and now with the other here and now and see that they absolutely do "fit" together. The fact that they do match up, even if distant in time and/or space, indicates that there is a consistency present, and a reality that "exists" that we only can experience and model, not be "greater than", but by analogy.

 

Regards, TAR2

[Iggy]

But what of two supernovae that we see at the same time? We call them simultaneous AND as Schrödinger's hat allows, also know that they did not both happen now.

I don't know exactly to what you're referring. Simultaneous means "at the same time". Time is relative so whether two events are simultaneous can depend on frame, but that is far beyond the scope of your confusion. If two supernova don't happen at the same time then they are not simultaneous.

 

You need to think of the supernova as an event. It happens at a specific place and time. The observation that we make of the supernova is a separate event. It happens at a different specific place and time. The two events happen at different times. They are not simultaneous.

[Schrödinger's hat]

But what of two supernovae that we see at the same time? We call them simultaneous AND as Schrödinger's hat allows, also know that they did not both happen now.

We only call two supernovae simultaneous in the strict sense (as it is used in discussing, say, relativity) if:

After we subtract out the light delay, they still happened at the same time.

So if we saw two supernovae in different directions in a single event (e.g. a single super-wide-angle camera took a single photo with both supernovae happening in it) we would only measure them as having happened simultaneously if they were equally far away..

 

Due to aberration effects the distance the light you view appeared to come from, changes between different frames. This will match up with the different distances and times

 

This indicates to me, that we are fully capable to both experienc the world AND know what it means in terms of when and where stuff happens. When we collect all the info and fit it together we can build one model of it that has two aspects. One being position/distance/angle from a reference point, and one being causal/timelike from a single timelike reference point. We can automatically do "transforms" by reevaluating our model from another connected here and now and matching up (rotating) our here and now with the other here and now and see that they absolutely do "fit" together. The fact that they do match up, even if distant in time and/or space, indicates that there is a consistency present, and a reality that "exists" that we only can experience and model, not be "greater than", but by analogy.

 

Yes, this is pretty much spot on. This is what SR (and science in general) attempts to be.

A few other things to say about this.

One of the aspects of this model is it does not elevate one now above any other. The concept of simultaneous is just a convenient label we can put on a certain set of events to make it easy to reason about them.

They are no more or less real than those at any other time.

 

There are four categories of events which do have physical meaning (for a given observer)

The past: Things that can effect me. No matter what frame I'm in, these events are always at a negative t coordinate (if I call here and now t=0).

This event: Right here, right now

The future: Things that I can effect. No matter what frame I'm in, these events are always at a positive t coordinate.

 

Other: These are events that I can neither effect, nor be effected by. They are too far away fro a signal to reach.

At small distances this category is indistinguishable from events at t=0, because light travels so fast. This is why the concept of the present makes so much sense to our minds.

[owl]

TAR2:

But it also means "arriving at the observer's location at the same time". This is

not the now that every location is experiencing presently.

 

Yes.

 

Schrodinger's hat:

One of the aspects of this model is it does not elevate one now above any other.

 

As long as you think that there a many “nows” you deny the meaning of simultaneity, which is “happening at the same time” with no location restrictions or concern about image travel time.

 

Relativity’s assertion that “time is relative”, makes more of it than elapsed time for light’s travel.

There are two concepts of simultaneity being expressed here recently. One is seeing images of two events at the same time, which means that the two events must be equidistant from the observer.

The other is “happening at the same time” (period)... regardless of when events are seen. This is universal presentism.

 

Schrodinger's hat:

I can imagine this perfectly well.

The earth, sun, moon etc as they exist over time are all four dimensional objects that exist and have intrinsic properties, no matter which frame they are viewed from.

 

You assert that these are all 4-D objects as if Minkowski spacetime, based on non-Euclidean geometry and cosmology were a given, established fact. It is not. I have argued vigorously against those *assumptions* in my “ontology of spacetime” thread and elsewhere. I will not repeat all the arguments against.

All “objects” beyond the geometric point, line, and plane (with zero, one and two dimensions respectively) are 3-D objects, and the space they exist in is also 3-D. Time elapses as things move, not a dimension, per se, but a very “real factor” since the universe is not a static snapshot.

I am glad that you realize that these objects “ exist and have intrinsic properties, no matter which frame they are viewed from.” Too bad you require 4-D space and objects to get there, and even then, what happens to "length contraction" when "objects that exist and have intrinsic properties, no matter which frame they are viewed from"? Back again to the "true shape of Earth" debate. Does that not depend, as the Cap 'n insists, on frame of reference, or do you disagree with him.

 

Your argument appears to be:

There is a universal and well defined now. (assume presentism)

Assume Realism

Therefore relativity is wrong

What is happening now Is happening presently, regardless of when we see it happening or where it Is happening.

Therefore positing different “nows” or a lack of simultaneity based on different frames of reference or the constant speed of light is wrong.

 

While ours is:

Assume realism

Assume 100 years of experiments showing constancy of the speed of light and disproving every elegant Ether model are correct

Therefore Relativity is correct and presentism is not.

 

The version of presentism I just re-presented above has nothing to do with any ether model. The conclusion does not follow unless the premises are agreed. (Yes for realism; no for any ether model)

 

Also you still haven't given me a definition of distance or time that are any better than the ones I had, I'm most interested to hear one that's not tautological

.

 

Seems like you are asking me to define distance without referring to the concept of the linear space between points or objects, how far it is from here to there... etc. I really don’t know how to put it differently than I already have. I tried to explain via realism, that without any intelligent observers with measuring sticks, the *whatever-you-want-to-call-it* between objects would remain as is, not dependent on or changing due to different frames of reference. Sorry, the best I can do. (Assumption: A real world/cosmos exists as is whether observed and/or measured from different frames of reference or not.)

Time (for the hundredth or so ‘time”): Event duration of physical processes. A chosen starting and ending is required for measurement thereof, but the earth keeps on turning and orbiting... event duration... whether or not we measure it and assign time units or "the beginning and ending" of a day or a year.

 

When the word simultaneous is used it means:

According the the observer of frame that is currently being considered, these events occur at the same time coordinate.

 

Now will also be a different set of events from different frames.”

 

I disagree, as above. ‘Happening at the same time’ is not dependent on “According the observer of frame that is currently being considered.”

Neither the time required for info to travel* any distance nor the constant speed of light negates the universality of the present, now everywhere... *it just “takes time.”

[Schrödinger's hat]

As long as you think that there a many "nows" you deny the meaning of simultaneity, which is "happening at the same time" with no location restrictions or concern about image travel time.

 

There is nothing about image travel time in the bulk of the responses here.

The one time I did mention it, I was responding to tar pointing out that sometimes the word simultaneous is used in different contexts to mean different things.

The meaning of simultaneous I have been using is that events occur at the same time coordinate as the one right here and now in my frame.

You are correct in your conclusion that this denies presintism's concept of now and simultaneous, as this type of now depends on my frame of reference (your now, and my now may not be the same).

 

Relativity's assertion that "time is relative", makes more of it than elapsed time for light's travel.

There are two concepts of simultaneity being expressed here recently. One is seeing images of two events at the same time, which means that the two events must be equidistant from the observer.

The other is "happening at the same time" (period)... regardless of when events are seen. This is universal presentism.

 

Well now there are three.

Ignore the first one. Noone was talking about images until tar brought it up. The third concept of simultaneous which you can't seem to distinguish from light delay is usually explained thusly:

 

Imagine you were to move some clocks out in all directions -- infinitely slowly so time dilation wouldn't effect them (if it were a real effect).

Events are simultaneous in the frame those close are stationary in, if the clocks each event is nearest have the same reading on them.

In a universe without a constant speed (one where galilean transforms work) all of the clocks from all of the different frames will agree as to what is simultaneous.

If you accept a constant speed of light, things are different. As Capn has been trying to explain, and I shall endeavour not to derail that conversation.

 

You assert that these are all 4-D objects as if Minkowski spacetime, based on non-Euclidean geometry and cosmology were a given, established fact. It is not. I have argued vigorously against those *assumptions* in my "ontology of spacetime" thread and elsewhere. I will not repeat all the arguments against.

All "objects" beyond the geometric point, line, and plane (with zero, one and two dimensions respectively) are 3-D objects, and the space they exist in is also 3-D. Time elapses as things move, not a dimension, per se, but a very "real factor" since the universe is not a static snapshot.

I am glad that you realize that these objects " exist and have intrinsic properties, no matter which frame they are viewed from." Too bad you require 4-D space and objects to get there, and even then, what happens to "length contraction" when "objects that exist and have intrinsic properties, no matter which frame they are viewed from"? Back again to the "true shape of Earth" debate. Does that not depend, as the Cap 'n insists, on frame of reference, or do you disagree with him.

 

The 3d slice we view of these 4d objects depends on the frame of reference chosen. Distance is not one of these intrinsic properties, just as the pancake changes from a circle to a line, the 4d things change from spheres to oblate sphereoids (if you slice them along a line of constant t).

 

What is happening now Is happening presently, regardless of when we see it happening or where it Is happening.

Therefore positing different "nows" or a lack of simultaneity based on different frames of reference or the constant speed of light is wrong.

 

You are assuming presintism again. This is incompatable with a constant speed of light.

 

The version of presentism I just re-presented above has nothing to do with any ether model. The conclusion does not follow unless the premises are agreed. (Yes for realism; no for any ether model)

 

The experimental evidence points to one of the following:

1) The speed of light is constant in all reference frames, or

2) The laws of physics conspire in a highly convoluted, specific, and arbitrary way to make it seem like they do.

 

Unless you want to deny experiment, these are your only two options. The first denies presentism, leaving you with 2), which leads to Lorentz Ether theory.

 

Everyone I know who has studied the matter goes with 1).

 

Seems like you are asking me to define distance without referring to the concept of the linear space between points or objects, how far it is from here to there... etc. I really don't know how to put it differently than I already have. I tried to explain via realism, that without any intelligent observers with measuring sticks, the *whatever-you-want-to-call-it* between objects would remain as is, not dependent on or changing due to different frames of reference. Sorry, the best I can do. (Assumption: A real world/cosmos exists as is whether observed and/or measured from different frames of reference or not.)

Time (for the hundredth or so 'time"): Event duration of physical processes. A chosen starting and ending is required for measurement thereof, but the earth keeps on turning and orbiting... event duration... whether or not we measure it and assign time units or "the beginning and ending" of a day or a year.

 

Well I have no idea what you mean by space other than amount of distance, or what you mean by duration other than a period of time. This definition appears indistinguishable (other than being more vague) from my version with 'the thing we measure with meter sticks' and 'the thing we measure with clocks'.

At any rate, the point I was trying to make is there is no definition (I know of) that isn't circular to some/all readers.

 

I disagree, as above. 'Happening at the same time' is not dependent on "According the observer of frame that is currently being considered."

 

Well you believe two contradictory things then. (the speed of light is constant, and presentism)

 

Neither the time required for info to travel* any distance nor the constant speed of light negates the universality of the present, now everywhere... *it just "takes time."

Ignore signal delay. We're not talking about signal delay (other than my response to tar, conceding that some people include signal delay, and that 'simultaneous' in the context of relativity ignores signal delay)

Edited September 19, 2011 by Schrödinger's hat

[owl]

Just a quick pass through here.

Schrodinger's hat:

...just as the pancake changes from a circle to a line, the 4d things change from spheres to oblate sphereoids (if you slice them along a line of constant t).

 

Just to clarify:

The pancake does not change from a disk (as I called it) to a 'fat line', (specified to acknowledge that the pancake has 'thickness'.) It stays the same shape, no matter how you "slice it" or look at it. These are real objects, according to realism. You can not "slice them!" You can "slice" your model of them on your imaginary coordinate system and make them into any shape you want.

 

And "a line of constant t" reifies time. It makes sense on your "coordinate system" but you are "slicing" nothing but that graphic concept. You can not believe that Earth changes shape with how you "slice it" in different frames of reference.

Correction, you can believe anything you want, but that doesn't make it science.

[Schrödinger's hat]

Just to clarify:

The pancake does not change from a disk (as I called it) to a 'fat line', (specified to acknowledge that the pancake has 'thickness'.) It stays the same shape, no matter how you "slice it" or look at it. These are real objects, according to realism. You can not "slice them!" You can "slice" your model of them on your imaginary coordinate system and make them into any shape you want.

Just as the pancake does not actually change its reality, neither does earth. Simply the three dimensional piece that we consider to be 'now'.

All of our interactions are based on a 3d slice of the 4d object, so this is what we perceive at any given time.

 

And "a line of constant t" reifies time. It makes sense on your "coordinate system" but you are "slicing" nothing but that graphic concept. You can not believe that Earth changes shape with how you "slice it" in different frames of reference.

Correction, you can believe anything you want, but that doesn't make it science.

I don't see any problem with putting time on the same philosophical ground as space.

It seems to be supported by Occam's razor. Replacing two concepts (time and space) with one (albeit a less intuitive one).

 

At any rate, all there are, are events.

Our perceptions of reality are three dimensional, so three dimensional slices of events are what are the most sensible.

It's also three dimensional slices of events (our light cone) that we effect, and that effect us.

It's natural to think of the stuff in between as three dimensional.

SR (specifically Minkowski geometry) says it's actually a very thin four dimensional wedge.

[owl]

This will be a complex post with a "time lag" trying to sort out and make sense of conversations on the last page with Cap 'n R and also an up to date reply to Schrodinger's hat. Starting with the latter.

You said:

Just as the pancake does not actually change its reality, neither does earth.

 

This is what I’ve been saying throughout this whole thread. Where does that leave the “length contracted” earth of 1000 mile diameter, as seen from a near lightspeed fly-by FOR, as posited by Cap ‘n R?

You say:

All of our interactions are based on a 3d slice of the 4d object....

...ignoring my critique of “4-D objects” as 3-D objects plus the time factor.

You continue;

...so three dimensional slices of events are what are the most sensible....

It's also three dimensional slices of events (our light cone) that we effect, and that effect us....

 

...Still ignoring my challenge that earth, sun and moon are real objects, and you can not slice them. The coordinate system which you can slice any way you like is not the actual solar system with all of its real, 3-D objects, in motion as they are ‘through time.”

 

Repeating another summary of the point of this thread:

Assumption: A real world/cosmos exists as is whether observed and/or measured from different frames of reference or not.

 

Now to my question to Cap’ n R in post 348:

Please detail the logic from, “The speed of light is constant" (agreed) to "the relativity of simultaneity." (I disagree.")

(Later, I again asked):

Will you please address my take on simultaneity above in equally clear English. Then maybe we can move on to your conclusion as pertains to length contraction.

I said:

We know that things happening at the same time in different locations are not simultaneous for observers in different FORs. This is why you say that simultaneity is relative. But they are still simultaneous regardless of from where and when they are observed. What is happening on Earth and on the Sun is all happening right now, not dependent on when we see (it.)

 

You answered:

You are still conflating light delay (the time it takes for us to see things) with relativity of simultaneity. The eight-minute delay in the travel of light from the Sun to the Earth has absolutely nothing to do with relativity of simultaneity as presented in special relativity.

 

In my example, what is happening in the railcar depends exactly upon whether you're moving relative to it.

 

Your dictum has been to measure events in the frame in which they are at rest -- e.g. events are simultaneous when you're standing on the railcar, in its reference frame, so they must remain simultaneous. What if the two walls of the car are moving in different directions? How do you decide which reference frame is correct?

 

So you changed to moving walls. My argument has always been that the overall view of the scene in question is the “reality” of the situation, not the individual frames of reference.

Will you please address this point? (Your next reply did not.):

 

Here you see the light moving at different speeds, since it's launched on a moving train; the light in the direction of travel goes faster, and the light intersects the walls simultaneously. This is what we'd see with bullets or model airplanes.

 

Light, however, behaves differently, as you could see in the diagram where the light reaches the wall at different times. This is solely because of its constant speed in all reference frames.

 

I replied:

I have agreed (several times) that the speed of light is constant, not effected by the speed of its source or of its observer(s.) I have even used the bullet from a moving gun illustration of the difference.

You continue:

The constant speed of light necessarily means that certain events can change order -- i.e., one that appears first in one reference frame can appear second in another. After all, I could draw the train moving in the other direction (or observe the train from a car driving past it very fast) and see the light reach the left wall first, rather than the right.

 

The interesting thing about this is that causality is always conserved; reordering events cannot create paradoxes.

You are speaking of the appearence of "certain events (changing) order" depending on different FORs.

I replied:

Still no argument against. Still doesn't address my assertion from realism that what is happening in the real world does not depend on the FOR from which that happening is observed. See my "jousting lasers experiment" on a one Au "track." I accurately stated what both jousters saw when and where on the track, which stayed the same length. Point: An over-all view of the whole situation does not depend on the individual FORs of the players.

To my:

Please show me the difference, i.e., how exactly I am conflating, as above.

You answered:

 

There is a difference between "I saw the explosion as happening eight minutes later, since the explosion was very far away and the light didn't reach me" and "the events are no longer simultaneous, even when I compensate for the light delay.

 

What? If they happened at the same time, they were simultaneous. When you see them is about light delay.

 

Now to your last posts on the last page:

 

Post 357:

Er.

"Events happening right now are simultaneous no matter what."

 

"Okay, here's an example where changing reference frames causes events to no longer be simultaneous."

 

"Makes perfect sense. Nevertheless, events happening right now are simultaneous no matter what."

 

Perhaps you should elaborate further on the evidence for your claim.

 

I'm not particularly impressed by your own contrived example, since it's easy to create an example that follows your rules, not relativity's.

 

Very confusing. “Yes” to first statement. “Happening at the same time” is what simultaneous means, and what is happening right now is all happening at the same time.

 

Second statement makes no sense.(Where did I say it did?) If they are happening at the same time, changing reference frames will not make them happen at different times, even though they will be seen at different times.

Elaboration: Distance between events does not change the "when they happen," only when they are seen in different FORs, repetitive as that is.

 

Post 359:

Where did you get the idea that the time lag for information about events is what causes relativity of simultaneity, or even has anything to do with it at all?

 

From all of the above.

 

Now, finally to the last exchange with Schrodinger's hat.

Me:

How fast something is going does not make the distance traveled shorter, just the time it takes to get there. (In all these statements, "according to realism" is implied.)

 

You:

If you are trying to say that distance being in the same category as angular size means that we are somehow saying reality is subjective then we may finally have grounds on which to start an actual philosophical discussion.

 

No. To the contrary:

I'm saying (realism asserts) that the distance to the sun doesn't change with how you look at it, and that a pancake doesn't change shape when you look at it on edge, even though it appears to do so.

[Iggy]

Where did you get the idea that the time lag for information about events is what causes relativity of simultaneity, or even has anything to do with it at all?

Signal delay, or "photon lag" is not the cause of the relative nature of simultaneity.

Ignore signal delay. We're not talking about signal delay

If they are happening at the same time, changing reference frames will not make them happen at different times, even though they will be seen at different times.

It must be an intentional strawman.

[owl]

I have some spare 'time.' Backing up to my last question to swansont: post 312:

You:

But you did. You claim (as I bolded above) that either the universe's properties are intrinsic, or they aren't. That excludes a third option, that only some properties are intrinsic. So given the choice of either realism or idealism, how would you classify the answer that some properties are intrinsic and some are not? Is that realism, or is it idealism?

Me:

You missed the point that realism supports the general (non specific) proposition that "the world" in general is real, as it is, regardless of how we observe or (measure it.) (Edited for spelling and clarity.)

If you say that some of "the world's" properties are intrinsic, again, "good for you." You are a realist regarding those properties.

If you say some properties of "the world" are not intrinsic, then you are an idealist regarding those properties, because they will depend, for their pseudo-reality on the FOR from which they are measured.

Clear enough?

 

I wonder if the above explained my position more clearly and you quit the challenge or what. (...Or if the "what" is that you do not agree to a respectful conversation, since that would be a 'first.')

 

Ps: The timestamp and quote alert for post 312 didn't work for three pages back (or my error), but if swansont is still interested, he will check in... if not... no more harassment from him, which is fine.

Edited September 21, 2011 by owl