Frame of Reference as Subject in Subjective Idealism

[swansont]

So, along comes the part of relativity theory (SR) that says “the world” is as it is observed/measured from whatever frame of reference (FOR), and there is no “preferred FOR.”

So, it either changes with every FOR from which it is observed (no intrinsic properties), or it doesn't change with every possible FOR, but we can not know which FOR yields an accurate description or measurement (all FORs being equally valid.)

 

No, this is false. SR does not say that all observations depend on your FOR. You should not criticize a theory you do not understand.

 

The all-or-nothing philosophy you present creates the false dichotomy. The negation of "all attributes are intrinsic" is NOT "no attributes are intrinsic," it is "some attributes are not intrinsic" — only a single attribute need not be intrinsic to falsify the statement. Someone who taught logic should know that.

[owl]

Swansont:

 

No, this is false. SR does not say that all observations depend on your FOR. You should not criticize a theory you do not understand.

 

Which observations do not depend on frame of reference?

 

You assert that you know better than I what I understand. Are you psychic? Or does your expertise in physics make you an expert in the philosophy of science pertaining to idealism vs realism. I have not seen posted evidence of that.

 

Your persistent disclaimers of my arguments, like "strawman, strawman!" and "false dichotomy" (several times) does you no credit as a philosopher or logician.

Neither did your mistaking my simple conditional, "if, then" logic, with two elements, for a syllogism with a stupidly inserted third (Wikipedia version*) and then criticizing me for introducing an extra element, which I had not.

*

(A syllogism (Greek: συλλογισμός – syllogismos – "conclusion," "inference") or logical appeal is a kind of logical argument in which one proposition (the conclusion) is inferred from two others (the premises) of a certain form, i.e. categorical proposition.

 

Maybe you are over your head in trying to argue logic and philosophy. Just a possibility to consider.

Edited September 9, 2011 by owl

[Schrödinger's hat]

Which observations do not depend on frame of reference?

For one, spacetime intervals.

If I stick a clock on each pole of the earth, and synchronise them (to the same time-zone), then record the time and place they are in when they each show 3:47:00am December 12th 2011, then the quantity c^2t^2-x^2-y^2-z^2 will never change no matter which FOR I am in.

 

Things that do depend on frames of reference:

Time and space intervals.

The two events (different clocks reading the same time) will happen at different times in different frames.

They will happen at different places in different frames.

Only the combination (time and space) is invariant.

 

Think back to that example I gave you of two of a circle.

If you do not consider the z axis when considering it from different angles (frames of reference) then it will get shorter.

 

Your refusal to consider the combination of spacial and temporal interval as being the invariant is exactly absurd to anyone who understands relativity as refusing to acknowledge the z axis for measuring the shape of a circle of paper.

 

Your persistent disclaimers of my arguments, like "strawman, strawman!" and "false dichotomy" (several times) does you no credit as a philosopher or logician.

 

But over and over again your present the two options:

1) Spatial intervals do not change between reference frames.

2) Reality is subjective.

 

Everyone here has responded at some point or another with:

3) Reality is four dimensional.

 

To which your response is:

No it isn't, pick 1 or 2

 

 

Owl, you cannot attack length contraction in isolation, it is a direct logical consequence of the lorentz transform.

No scientist got up one day and said 'oh, I know. I'll just say that lengths of objects get smaller if they're moving.'

They reluctantly accepted it as a logical consequence of adding two assumptions to existing theory, (or arguably only the second):

 

1) The laws of physics are the same in all inertial reference frames, and

2) The speed of light is a law of physics.

 

Whenever someone tries to walk you through the chain of logic that leads from these assumptions to length contraction you tell them they're performing mind games or just refuse to respond.

[Cap'n Refsmmat]

For one, spacetime intervals.

If I stick a clock on each pole of the earth, and synchronise them (to the same time-zone), then record the time and place they are in when they each show 3:47:00am December 12th 2011, then the quantity c^2t^2-x^2-y^2-z^2 will never change no matter which FOR I am in.

Also the rest mass, the speed of light, and all of the Lorentz scalars (there are a few).

[Schrödinger's hat]

Also the rest mass, the speed of light, and all of the Lorentz scalars (there are a few).

And all your four-vectors (and tensors, I suppose, but let's not go there -- also their components may change, but they are still the same vector), four-acceleration, energy-momentum...and so on.

Events. If I explode in one frame, I will explode in every frame, it's just a matter of when and where.

Order of events along a time-like path, (or a space-like path not sure if it's mixed....probably still ordered?)

We can keep going if you like?

[swansont]

You assert that you know better than I what I understand. Are you psychic? Or does your expertise in physics make you an expert in the philosophy of science pertaining to idealism vs realism. I have not seen posted evidence of that.

 

No, I suppose it's possible you actually do understand relativity and your gross errors are made on purpose for some reason, i.e. you could be trolling. I'm assuming your errors are genuine.

 

Your persistent disclaimers of my arguments, like "strawman, strawman!" and "false dichotomy" (several times) does you no credit as a philosopher or logician.

 

In your opinion.

 

Neither did your mistaking my simple conditional, "if, then" logic, with two elements, for a syllogism with a stupidly inserted third (Wikipedia version*) and then criticizing me for introducing an extra element, which I had not.

 

Are you saying you cannot take an if-then statement and recast it as a syllogism? I would think that to be trivial for someone versed in logic. The conclusion to this is left as an exercise.

 

Maybe you are over your head in trying to argue logic and philosophy. Just a possibility to consider.

 

Considered all the time. But rejected in this case. Your arguments are those of a crackpot and your amateurish mistakes belie your claims of expertise.

 

How about actually addressing the point here: Is NOT(all attributes are intrinsic) = no attributes are intrinsic (i.e. not "all a are b" = "no a are b") a logically true/valid statement or not?

[owl]

For one, spacetime intervals.

 

...Assuming "spacetime" as an established fact.

... Ignoring my whole argument (and all cited references) to the contrary.

I cite Brown and Pooley's "Minkowski's Spacetime: a glorious non-entity" and Dieks' two volumes of papers from the conferences of the International Society for the Advanced Study of Spacetime. this forum, and you, case in point, ignore it all and, like most texts and websites on relativity, speak of spacetime as a given.

 

Now back to mainstream spacetime for a moment, a la Wikipedia:

In physics, spacetime... is any mathematical model that combines space and time into a single continuum. Spacetime is usually interpreted with space as being three-dimensional and time playing the role of a fourth dimension that is of a different sort from the spatial dimensions. According to certain Euclidean space perceptions, the universe has three dimensions of space and one dimension of time.

The ontology of time (see my thread on that... in "Speculations") does not grant "it", time, the status of an entity that "combines with space." It remains, as per my argument, the 'event duration of physical events.' And space remains empty volume until evidence that it too as a malleable medium is established.

I agree that the "universe has three dimensions of space and one dimension of time," though I would not call the time required for all movement a "dimension."

Now to the "rotation" of the "spacetime manifold", quoting

Bartelby.com on Minkowski’s Four Dimensional Space:

 

We can regard Minkowski’s “world” in a formal manner as a four-dimensional Euclidean space (with imaginary time co-ordinate); the Lorentz transformation corresponds to a “rotation” of the co-ordinate system in the four-dimensional “world.”

(my bold)

So, from my argument, we have a "mathematical model", a coordinate system based on a non-entity, spacetime with an imaginary time coordinate (which, in the real world simply accounts for object's movements through 3-D space, simple volume)... "rotating."

Then, as "explained" by Cap 'n R, we can look at our theoretical manifold from any angle of rotation and "see spacetime" as quite different from different frames of reference. And we can slice it up and find its contents in any number of creative arrangements.

 

These are abstract concepts, and easily imaged on computer screens. But how does all of that relate to "the real cosmos" of space with stuff in it moving around as "time elapses?"

 

Then back again to continue the Wiki quote on spacetime:

 

By combining space and time into a single manifold, physicists have significantly simplified a large number of physical theories, as well as described in a more uniform way the workings of the universe at both the supergalactic and subatomic levels.

 

How convenient for physics, but what are the referents in the real world? Again, if space and time don't exist without objects moving around (paraphrased Einstein), what is spacetime anyway? Event duration doesn't exist without events. I disagree with the disappearance of space. "No objects" leaves empty space.

 

Anyway, then you are off and running on synchronized clocks without having addressed any of the above.

 

Then to "Things that do depend on frames of reference:"

Time and space intervals.

Argument against:

If there were no intelligent life observing cosmos from different frames of reference, objects would still be moving, and that requires "time" even if there were no clocks measuring any/all such event duration. The (moving) positions of all objects in space would remain "as is" regardless of any theoretical frame of reference from which they are observed.

 

The two events (different clocks reading the same time) will happen at different times in different frames.

They will happen at different places in different frames.

 

Only the combination (time and space) is invariant.

 

The above argument still applies. Observation from different frames does not change the position or elapsed time for movement of objects in the real-space cosmos, regardless of how we manipulate coordinate systems.

Now back to basic geometry:

 

Think back to that example I gave you of two of a circle.

If you do not consider the z axis when considering it from different angles (frames of reference) then it will get shorter.

 

I'd need link or directions to that example, and the typo above loses the sense of it.("Two dimensions of a circle, I presume.) What z axis?

Conventionally, a plane (circle in this case) has two dimensions, x & y. Rotate it through 3-D space (the z axis) and you eventually describe a sphere of the same radius as the 2-D circle.

 

Your refusal to consider the combination of spacial and temporal interval as being the invariant is exactly absurd to anyone who understands relativity as refusing to acknowledge the z axis for measuring the shape of a circle of paper.

 

I have considered the space-time interval in detail above and "spacetime" as a 4-D "invariant" coordinate system also in detail above, as per criticisms of "it."

 

As per the "z axis" of a 2-D (x-y dimensional plane), please study, if you have not already, the frequently cited (by me) paper by Kelley Ross, The Ontology and Cosmology of Non-Euclidean Geometry. You take for granted that non-Euclidean is now the one and only established and factual version of space and time and spacetime and geometry in general. I have disagreed in all my threads here.

But over and over again your present the two options:

1) Spatial intervals do not change between reference frames.

2) Reality is subjective.

 

I present the argument for realism/naturalism that the reality of the world/cosmos does not depend on how it is observed, from whatever frame of reference. Specifically, earth is not closer than 93 million miles from the sun just because a certain extreme frame of reference might see it that way... (yes, over and over.)

 

Relativity has its special language, "spatial intervals" in which time and space are theoretically combined, but that does not mean that the AU changes with every extreme in frame of reference from which it is observed. In the real world the elliptical orbit makes the trivial changes in that distance happen, and the AU averages that variation.

 

Everyone here has responded at some point or another with:

3) Reality is four dimensional.

 

To which your response is:

No it isn't, pick 1 or 2

 

That "consensus" (not a criterion for "factual") is not shared by the many critics I've cited, including those in this post.

 

And I have no beef with 3-D space as simple volume and time as above. That version of cosmos does not include either the morphing of earth, the AU, and the meter rod to suit the 4-D theory, nor does it support the claim that there is no way to know the actual, intrinsic (realist terms) dimensions of the three cases above.

 

This is not a "false dichotomy."

Earth has an 8000 or so mile diameter or it doesn't... in spite of the claim that from a certain extreme frame of reference it might be measured as only 1000 miles... or "it *is* a 1000 mile diameter... for that frame of reference."

 

Owl, you cannot attack length contraction in isolation, it is a direct logical consequence of the lorentz transform.

 

I just did, though I included my other two favorite examples above as well.

 

Even Lorentz can not transform the earth into a severely oblate spheroid. The entire scientific community knows better than that.

No scientist got up one day and said 'oh, I know. I'll just say that lengths of objects get smaller if they're moving.'

They reluctantly accepted it as a logical consequence of adding two assumptions to existing theory, (or arguably only the second):

 

1) The laws of physics are the same in all inertial reference frames, and

2) The speed of light is a law of physics.

 

Cap 'n R said here awhile back that length contraction is not about objects changing lengths (or shapes, with contracted diameters), but rather that there is no way of telling which frame of reference is correct. (Paraphrased. Please correct me if this misrepresents you, Cap 'n.) He illustrated this with many creative thought experiments, even though there is no actual experimental verification of large scale length contraction...

unless you grant that "for a muon" ( as an equally valid frame of reference) the atmosphere is way less than 200 miles through, based on their longer than expected lifespan... "time dilated" resulting in a way shorter, "length contracted" distance traveled.

 

Finally, motivated by my recent arguments with Cap 'n R on SR and the (so far agreed) constant speed of light, I have been studying light experiments more vigorously lately.

 

I've begun to wonder how certain it is that light has zero "resting mass." For one thing, there are no "resting" photons, and their moving momentum acts like mass. Lasers recoil when fired. Solar wind "pushes things" through space. In the "box of mirrors" experiment, it gains resting inertia with laser beams bouncing around inside, as if it gained mass.

 

Then there is the "questioning authority" from other sources. One example (not having checked his credentials):

http://o.castera.free.fr/pdf/onemorederivation.pdf

Jean-Marc Levy-Leblond:

 

.

The evidence of the nonzero mass of the photon would not, as such, shake in any way validity of the special relativity. It would, however, nullify all its derivations which are based on the invariance of the photon velocity.

 

My bold. Just an avenue that I am exploring, though I have agreed (maybe prematurely) to constant 'C' after reviewing the Michelson/ Morley experiment and summaries of more contemporary verifications.

 

Well, I'll quit before this becomes a book- length post.

Gone for the weekend again.

Edited September 10, 2011 by owl

[Cap'n Refsmmat]

...Assuming "spacetime" as an established fact.

No. A spacetime interval can be calculated without the notion of spacetime existing:

 

[math]s^2 = (\Delta x)^2 - (c \Delta t)^2[/math]

 

This can be done only with knowledge of the speed of light, the distance separation between two events, and the time between those two events. One must not make any assumptions about the nature of spacetime; one could say that spacetime consists of tie-dyed rabbit pelt and spacetime intervals would work equally well.

 

All one needs is the notion of a distance between events and a time between events. The ontology of spacetime is irrelevant to the invariance of the interval.

 

Relativity predicts that any two observers will agree on the spacetime interval between events, no matter what reference frame they observe the events from. The spatial and temporal separations might differ between frames, but the interval does not, regardless of what "spacetime" is or isn't.

[Schrödinger's hat]

...Assuming "spacetime" as an established fact.

I need only assume that there are 3 space-like degrees of freedom, and one time-like degree of freedom. No ontology is implied, merely that it can be described as a vector space.

The ontology of time (see my thread on that... in "Speculations") does not grant "it", time, the status of an entity that "combines with space." It remains, as per my argument, the 'event duration of physical events.' And space remains empty volume until evidence that it too as a malleable medium is established.

I see no way in which 'empty volume' is any more of a descriptor of what space is than just calling it space.

Same goes for time. What do you mean duration? Then what do you mean by ____

Eventually we just get back to 'some measure of change' or 'something measured with clocks.

 

If you wouldn't mind, I'd prefer to take pragmatic definitions

space: 'the thing we measure with meter sticks' and

time: 'the thing we measure with clocks'

Whatever they happen to be.

Spacetime can be 'the thing, or things that we measure with clocks and meter sticks'. Whether space and time are somewhat interchangable (thus 'thing'), or completely separate entities ('things')

 

If you read my response to tar, or any other derivation of the simultenaety of relativity you'll notice that once the assumption of constant speed of light is accepted, moving clocks no longer measure the same thing as stationary clocks.

 

I agree that the "universe has three dimensions of space and one dimension of time," though I would not call the time required for all movement a "dimension."

Will you at least concede that it's a dimension in the mathematical sense, in that it's a degree of freedom which is independant (again, mathematical definition -- as in orthogonal) from the three spatial degrees of freedom, and that it is required to describe events?

This is what I (and most physicists -- when they are not discussing the ontology of space and time at least) mean when I say dimension.

Now to the "rotation" of the "spacetime manifold", quoting

Bartelby.com on Minkowski’s Four Dimensional Space:

(my bold)

So, from my argument, we have a "mathematical model", a coordinate system based on a non-entity, spacetime with an imaginary time coordinate (which, in the real world simply accounts for object's movements through 3-D space, simple volume)... "rotating."

Then, as "explained" by Cap 'n R, we can look at our theoretical manifold from any angle of rotation and "see spacetime" as quite different from different frames of reference. And we can slice it up and find its contents in any number of creative arrangements.

 

These are abstract concepts, and easily imaged on computer screens. But how does all of that relate to "the real cosmos" of space with stuff in it moving around as "time elapses?"

It relates in that any scenario we can set up in a laboritory -- or see in the world around us -- agrees with the results from this abstraction.

Because the speeds and energies involved are so large, the real situations where the results of relativity differ significantly from classical physics all involve things that are very small, or very large and far away.

We then induce that the same laws would apply to medium things, or close, large, things if they were moving fast.

Just as one would induce that the sun still rose and set if one was underground for a number of days.

How convenient for physics, but what are the referents in the real world? Again, if space and time don't exist without objects moving around (paraphrased Einstein), what is spacetime anyway? Event duration doesn't exist without events. I disagree with the disappearance of space. "No objects" leaves empty space.

 

Anyway, then you are off and running on synchronized clocks without having addressed any of the above.

Surely we have to establish what whether space and time are the same thing before we can even begin to come up with an ontology for them?

No-one here that I've noticed has said anything about an ontology for spacetime. They merely use 'spacetime' as shorthand for 'a possibly unknown entity or non-entity wherein events occur such that they can be described by a four dimensional vector space' (it is also implied that one appends a 'that transforms under the lorentz group' to that if one is talking to a physicist, but we'll leave that bit off now for your sake). We get a bit tired of describing everything from scratch every time, which is why we come up with these 'sequences of vocalisations which may also be represented as a series of glyphs' or 'words'. I hope you'll let me use them without having to come up with an ontology for them first.

 

Then to "Things that do depend on frames of reference:"

 

Argument against:

If there were no intelligent life observing cosmos from different frames of reference, objects would still be moving, and that requires "time" even if there were no clocks measuring any/all such event duration. The (moving) positions of all objects in space would remain "as is" regardless of any theoretical frame of reference from which they are observed.

 

 

 

The above argument still applies. Observation from different frames does not change the position or elapsed time for movement of objects in the real-space cosmos, regardless of how we manipulate coordinate systems.

No-one said anything at all about events being different in different reference frames. In fact the very point of the entire matter is that they aren't -- and this is the entire point (along with constancy of speed of light) of relativity and science in general.

Let's say I have a vector pointing from the event in which bob trips over and skins his knee at the south pole, to alice sitting on santa's lap at the north. They happen at the same time.

It might go[math] [x,y,z,t] = [0m,13000000m,0m,0s][/math]

(note, all these numbers are rounded to 2 sig figs or so)

No matter which coordinate system you use it is still the same vector.

I could describe it as [math][0km,13000km,0km,0s][/math] if I wanted, or in miles or whatever.

I could also describe it from a coordinate system which is rotated, it might go

[math][13000000m,0m,0m,0s][/math] or [math][9000000m,0m,9000000m,0s][/math] depending on how I rotate my frame of reference.

None of these is any more correct than the others. There is no absolute angle which all measurements are correct in.

 

Now if I boost my frame of reference to 0.866 times the speed of light (a very similar operation), I might get (according to special relativity):

[math][26000000m,0m,0m,-0.075s][/math]

So the events happen further apart and at different times.

If I take some different events, so they are at the same time I am no longer measuring the same thing.

Say I take a slightly earlier event, where bob is in the process of tripping over, I get:

[math][26000000m - 0.866c*0.075,0m,0m,0s] = [6500000m,0m,0m,0s][/math]

This is the origin of length contraction.

Cap 'n R said here awhile back that length contraction is not about objects changing lengths (or shapes, with contracted diameters), but rather that there is no way of telling which frame of reference is correct. (Paraphrased. Please correct me if this misrepresents you, Cap 'n.) He illustrated this with many creative thought experiments, even though there is no actual experimental verification of large scale length contraction...

unless you grant that "for a muon" ( as an equally valid frame of reference) the atmosphere is way less than 200 miles through, based on their longer than expected lifespan... "time dilated" resulting in a way shorter, "length contracted" distance traveled.

 

Finally, motivated by my recent arguments with Cap 'n R on SR and the (so far agreed) constant speed of light, I have been studying light experiments more vigorously lately.

@capnrefsmmat Awww, he's (mis)quoting you to disprove me. Given our recent interactions I find that not the least bit hilarious.

Without going back and re-reading his posts, I will posit that Capn was trying to get across the concept that there is no correct reference frame. They are all equal. We can define things like proper lengths of collections of events that we call a solid object, but if you had something like....three objects passing each other such that they were in a straight line at some point, and were to ask the question 'what is the length of the line' there is no single reference frame which you can single out as the one in which that is a proper length.

 

You say you agree to constant c, but you steadfastly refuse any of the trains of logic which lead from there to the lorentz transform.

 

Again, I'd like you to state the assumptions you're operating on, because as far as I can see some of them are contradictory. Perhaps I can help you along -- which of these are you assuming?

The Galilean transform will give correct results when changing from one frame of reference to another,

There is a well defined stopped reference frame from which all measurements can be taken

Measurements taken from this stopped reference frame will differ somehow from those taken in another in a way that measurements from two different moving reference frames do not.

The speed of light is a law of physics

The laws of physics are the same in all non-accelerating reference frames

[tar]

Schrodinger's hat,

 

(sorry, not sure how to get the umlaut)

 

 

I guess my thought experiment was designed to establish one FOR that both the buoys and the double ended flashlight were operating within. All clocks, buoys and recording devices were to be brought back to the lab and studied to see what actually did happen, and "when" and "where" events actually occured, in the lab's reference frame, in retrospect.

 

It seems to me, that in this scenario, the flashlight never leaves the lab's reference frame, and the conclusion would be that since length can not be (in the flashlight's FOR) both expanded in the rearward direction, and contracted in forward direction, or contracted in the rearward direction and expanded in the forward, that indeed the laws of physics themselves need to be assessed from just one frame.

 

'Cause clocks cannot slow unless they slow in reference to "normal", and if the flashlight's clock slows in reference to the "lab" which included the whole local group of galaxies, AND the clocks of the whole local group of galaxies slow in reference to the "normal" of the flashlight, then the whole shooting match should grind to a halt. Which it does not.

 

So the flashlight does not redefine the universe and cause it all to move at .5C around it. It moves through the universe at .5C. The foward photons cannot reach the 187th and the first buoy at the same timestamp in the "galaxy lab" perspective, AND be figured by the flashlight to have to arrive at anything other than the "proper" time.

 

So the flashlight does not see the universe as homogenous. It sees the one direction, in which it is traveling, as extremely blueshifted, and where it has been, as extremely redshifted. The flashlight "knows" it is traveling at .5C through the "galaxy lab".

 

Regards, TAR2

 

P.S. And the flashlight "sees" the "fixed galaxies" that are perpendicular to its direction of motion, in normal light.

Edited September 12, 2011 by tar

[owl]

No. A spacetime interval can be calculated without the notion of spacetime existing:

 

[math]s^2 = (\Delta x)^2 - (c \Delta t)^2[/math]

 

This can be done only with knowledge of the speed of light, the distance separation between two events, and the time between those two events. One must not make any assumptions about the nature of spacetime; one could say that spacetime consists of tie-dyed rabbit pelt and spacetime intervals would work equally well.

 

As a realist, I always try to understand what these terms mean as descriptions of the observable world. A “spacetime interval” as pertaining to a tie-died rabbit pelt would be a real challenge to one trying to make sense of the phrase!

An interval is elapsed time as objects move through space, as I understand the relationship between space and time and the word “interval.”

 

And how about spacetime as that medium curved by gravity in general relativity theory? What curves besides object’s trajectories?

All one needs is the notion of a distance between events and a time between events. The ontology of spacetime is irrelevant to the invariance of the interval.

 

Relativity predicts that any two observers will agree on the spacetime interval between events, no matter what reference frame they observe the events from. The spatial and temporal separations might differ between frames, but the interval does not, regardless of what "spacetime" is or isn't.

 

Just to sort out the meaning of words more clearly, would you object to a translation of the common use of "event" in physics to mean "object", and the application of the word "event" to that which happens as things move? Then we could speak of the distance between objects at a given time as they both move, either closer or further apart. Like "right now", earth IS exactly (whatever) distance from the sun, though that distance varyies with earth's position in elliptical orbit. I am describing objects and their movements as time elapses in the real world in concrete terms without automatic assumption of the special theoretical lingo relativity theorists use, as you do above, as in "the invariance of the interval."

 

Then what would your second paragraph mean in my translated terms? Does it mean that any two observers will agree on the above "right now" earth-sun distance, "no matter what...?"

And when you say, "The spatial and temporal separations might differ between frames,but the interval does not...", doesn't that mean that different FORs will "see" that "right now" distance differently, while the "rabbit pelt interval" remains invariant, the objective, true measurement? All one needs is a magic word to get at the "real distance?"

Please assume for a moment, for the sake of my argument that there is no "temporal separation" in the present take on that distance, from whatever frame, because "time" is not different in different locations, not an entity, even though clocks will show different times 'as seen from another frame.' (Now being simultaneous for all frames everywhere in this argument, even in the face of relativity's "lack of simultaneity" dictum to the contrary.)

 

Now to back up to swansont's tedious criticisms (without specifics, as usual):

To my:

You assert that you know better than I what I understand. Are you psychic? Or does your expertise in physics make you an expert in the philosophy of science pertaining to idealism vs realism. I have not seen posted evidence of that....

 

You reply:

 

No, I suppose it's possible you actually do understand relativity and your gross errors are made on purpose for some reason, i.e. you could be trolling. I'm assuming your errors are genuine.

 

Again, labeling as “errors” doesn’t make (whatever?) wrong, and you avoid yet again my distinction between idealism and realism. Seems you consider argument by labeling the apponent wrong, and name calling (crackpot and amateurish, as below) as valid forms.

 

You challenge:

Are you saying you cannot take an if-then statement and recast it as a syllogism? I would think that to be trivial for someone versed in logic. The conclusion to this is left as an exercise.

 

No. I have said repeatedly that I was using simple conditional, “if, then” logic without a misplaced third element, which makes a two element syllogism absurdly wrong (as illustrated by Wikipedia on syllogisms.) You re-cast my conditional as a syllogism and claimed that I had introduced a third element, which I had not.

 

You:

Your arguments are those of a crackpot and your amateurish mistakes belie your claims of expertise.

 

More name calling, which simply and obviously demonstrates how vacuous your argument remains.

 

How about actually addressing the point here: Is NOT(all attributes are intrinsic) = no attributes are intrinsic (i.e. not "all a are b" = "no a are b") a logically true/valid statement or not?

 

Very pedantic and lame if intended as a rebuttal of my last “either, or.”...

Something like, ... Either Earth has a 1000 mile or so diameter or it doesn’t.

Background, in "if, then" format: If there is no preferred frame of reference, then the above description is equally as valid as the extremely well verified 8000 mile diameter.

If Earth's diameter is, in fact around 8000 miles, then there is a preferred frame of reference, namely at rest with the object measured.

Or, more generally, either the world/cosmos is real and has properties intrinsic and independent of measurement, or it doesn’t, and the world’s reality depends on how (from what frame of reference) it is measure.

I don't expect a rebuttal, since you have not been able to follow this simple logic before.

 

Edit: I am speaking in the general terms of idealism vs realism here, about "the world." I know you have said that some properties are intrinsic (not idealism... good for you!),and some are not. You use length (and by implication, Earth's diameter) as an example of a property which is not intrinsic. This does in fact claim that earth's diameter depends on the frame of reference from which it is observed. So either Earth doesn't have an intrinsic shape independent of measurement, or nobody knows what its correct shape/ diameter is. Both propositions are equally absurd according to realism/naturalism. And either assertion would make you an idealist.

 

Of course, “all attributes are intrinsic” does NOT equal “no attributes are intrinsic.”

“ not "all a are b" = "no a are b"... is obviously false.

But I did not assert either (obviously stupid) argument, as yet again illustrated above.

Edited September 12, 2011 by owl

[swansont]

If you are going to complain about purported name calling, then you should not be a practitioner yourself.

 

Very pedantic and lame if intended as a rebuttal of my last “either, or.”...

Something like, ... Either Earth has a 1000 mile or so diameter or it doesn’t.

Background, in "if, then" format: If there is no preferred frame of reference, then the above description is equally as valid as the extremely well verified 8000 mile diameter.

If Earth's diameter is, in fact around 8000 miles, then there is a preferred frame of reference, namely at rest with the object measured.

Or, more generally, either the world/cosmos is real and has properties intrinsic and independent of measurement, or it doesn’t, and the world’s reality depends on how (from what frame of reference) it is measure.

I don't expect a rebuttal, since you have not been able to follow this simple logic before.

 

Of course, “all attributes are intrinsic” does NOT equal “no attributes are intrinsic.”

“ not "all a are b" = "no a are b"... is obviously false.

But I did not assert either (obviously stupid) argument, as yet again illustrated above.

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?

[Cap'n Refsmmat]

As a realist, I always try to understand what these terms mean as descriptions of the observable world. A “spacetime interval” as pertaining to a tie-died rabbit pelt would be a real challenge to one trying to make sense of the phrase!

It would certainly be more fun, however.

 

An interval is elapsed time as objects move through space, as I understand the relationship between space and time and the word “interval.”

 

And how about spacetime as that medium curved by gravity in general relativity theory? What curves besides object’s trajectories?

That works here. We don't need to invoke general relativity in this case, since adding gravity and spacetime curvature just makes things more complicated.

 

Just to sort out the meaning of words more clearly, would you object to a translation of the common use of "event" in physics to mean "object", and the application of the word "event" to that which happens as things move? Then we could speak of the distance between objects at a given time as they both move, either closer or further apart. Like "right now", earth IS exactly (whatever) distance from the sun, though that distance varyies with earth's position in elliptical orbit. I am describing objects and their movements as time elapses in the real world in concrete terms without automatic assumption of the special theoretical lingo relativity theorists use, as you do above, as in "the invariance of the interval."

 

Then what would your second paragraph mean in my translated terms? Does it mean that any two observers will agree on the above "right now" earth-sun distance, "no matter what...?"

And when you say, "The spatial and temporal separations might differ between frames,but the interval does not...", doesn't that mean that different FORs will "see" that "right now" distance differently, while the "rabbit pelt interval" remains invariant, the objective, true measurement? All one needs is a magic word to get at the "real distance?"

Please assume for a moment, for the sake of my argument that there is no "temporal separation" in the present take on that distance, from whatever frame, because "time" is not different in different locations, not an entity, even though clocks will show different times 'as seen from another frame.' (Now being simultaneous for all frames everywhere in this argument, even in the face of relativity's "lack of simultaneity" dictum to the contrary.)

An "event" is an object being in a specific place at a specific time. One could describe the Earth and the Sun as two separate events: "the Earth was in this place at exactly this time," and "the Sun was in this other place at exactly this time." (Clearly their positions change through time, so one must specify the time.)

 

So if I measure the spatial distance between two events, I can call that [math]\Delta x[/math]. If I measure the time that elapsed between two events, I can call it [math]\Delta t[/math]. So suppose I measure the distance between the Earth and Sun right now. In the spacetime interval:

 

[math]s^2 = (\Delta x)^2 - (c \Delta t)^2[/math]

 

...[math]\Delta t = 0[/math], since I'm measuring the two positions at exactly the same time. So the interval between those two events is [math]s^2 = (\Delta x)^2[/math], or just the distance between them right now.

 

Now, suppose I measure Earth's position now and the Sun's position ten minutes from now. Now [math]\Delta t = 10\text{ s}[/math], and so the spacetime interval ends up different than before. That makes sense, because I'm measuring the Earth's position and the Sun's position at different times. Clearly the distance won't be the same.

 

Now, everyone will agree on the spacetime interval between two events, no matter where they are, what they're doing, or how fast they're going. Even if the distance is contracted, the spacetime interval will come out the same.

[Iggy]

As a realist, I always try to understand what these terms mean as descriptions of the observable world. A “spacetime interval” as pertaining to a tie-died rabbit pelt would be a real challenge to one trying to make sense of the phrase!

In fact, you are at least consistent in your approach. You have made it a frequent argument:

 

• 
   
  
• Physical things contract. If relativity has "length contraction" then it requires that length be a physical thing.
  
• Physical things dilate. If relativity has "time dilation" then it requires that time be a physical thing.
  
• Malleable mediums curve. If relativity has "space-time curvature" then it requires that space-time be a malleable medium.
  

You even made the interval argument before...

 

...The rod's spacetime interval stays constant between reference frames, though.

Since I, and many others (ISASS, in spacetime thread) do not accept "spacetime" as a given, as in relativity, using the word as an established fact is not appropriate for a discussion which disputes "spacetime intervals." It assumes a premise in dispute.

 

Guess which logical fallacy it is?

 

I can relate though. When I was young I heard the term "devil's food cake" and it proved in my mind that the devil was a real physical being. How, after all, could he have a cake otherwise?

[Schrödinger's hat]

So the flashlight does not see the universe as homogenous. It sees the one direction, in which it is traveling, as extremely blueshifted, and where it has been, as extremely redshifted. The flashlight "knows" it is traveling at .5C through the "galaxy lab".

 

Regards, TAR2

 

P.S. And the flashlight "sees" the "fixed galaxies" that are perpendicular to its direction of motion, in normal light.

You appear to be talking about a preferred reference frame -- a concept not present in special relativity. I need a bit more information before I can respond sensibly.

 

So you are disputing the postulate of relativity? (Namely that the laws of physics are the same in all inertial reference frames -- inertial reference frames being those like the one where the flashlight thinks it's still.)

Or that the speed of light is a law of physics? (ie. the speed of light will be measured as the same from an apparatus which is in a different inertial reference frame).

 

If either of these are the case, how do you define the frame in which C=3*10^8m/s? The one where the CMBR is isotropic? Pick a random galaxy and take the frame where its redshift is zero? Non-moving compared to the centre of the milky way? The frame of Sol? These are all different (and vary by up to 500km/s or so iirc), and Earth's surface's velocity relative to these objects changes on a yearly and daily basis.

If there is a preferred frame then doing experiments with moving instruments (like doing one in the morning and one in the afternoon) and assuming that they are stationary should yield different results.

 

If you could try to predict what would happen according to your model what would happen according to instruments on the flashlight were one to assume it was stationary that would be useful.

My response was based on the assumption that the flashlight can be considered stationary, and according to its instruments light moved at the same speed as it does according to instruments in other frames.

 

'Cause clocks cannot slow unless they slow in reference to "normal", and if the flashlight's clock slows in reference to the "lab" which included the whole local group of galaxies, AND the clocks of the whole local group of galaxies slow in reference to the "normal" of the flashlight, then the whole shooting match should grind to a halt. Which it does not.

This is one of the many counter-intuitive elements of SR. The galaxy clocks are slow in the flashlight frame, and the flashlight clock is slow in the galaxy frame. Neither time dilation nor length contraction make sense in isolation, it is only when you consider time dilation, length contraction and the simultenaety of relativity together that the paradoxes disappear -- as they are all consequences of the Lorentz transform.

[owl]

It would certainly be more fun, however.

 

That works here. We don't need to invoke general relativity in this case, since adding gravity and spacetime curvature just makes things more complicated.

 

Ref: "That" being my,

An interval is elapsed time as objects move through space, as I understand the relationship between space and time and the word “interval.”

And my:

And how about spacetime as that medium curved by gravity in general relativity theory? What curves besides object’s trajectories?

... was just a reminder that GR takes "spacetime" and "makes something of it" besides a place holder (a 'whatever') for SR math. Ontologists are picky about assertions that spacetime is curved by gravity even though it arguably remains a "non-entity."

 

An "event" is an object being in a specific place at a specific time. One could describe the Earth and the Sun as two separate events: "the Earth was in this place at exactly this time," and "the Sun was in this other place at exactly this time." (Clearly their positions change through time, so one must specify the time.)

So far so good.

 

So if I measure the spatial distance between two events, I can call that [math]\Delta x[/math]. If I measure the time that elapsed between two events, I can call it [math]\Delta t[/math]. So suppose I measure the distance between the Earth and Sun right now. In the spacetime interval:

 

[math]s^2 = (\Delta x)^2 - (c \Delta t)^2[/math]

 

...[math]\Delta t = 0[/math], since I'm measuring the two positions at exactly the same time. So the interval between those two events is [math]s^2 = (\Delta x)^2[/math], or just the distance between them right now.

Right...

So suppose I measure the distance between the Earth and Sun right now. In the spacetime interval:

(insert math symbols for purpose of calculation... fine...)

 

Then you say:

So the interval between those two events is [math]s^2 = (\Delta x)^2[/math], or just the distance between them right now.

Fine. The distance between them now is the distance between them now. The repetition gains nothing and the math looks irrelevant to the meaning.

 

Now, suppose I measure Earth's position now and the Sun's position ten minutes from now. Now [math]\Delta t = 10\text{ s}[/math], and so the spacetime interval ends up different than before. That makes sense, because I'm measuring the Earth's position and the Sun's position at different times. Clearly the distance won't be the same.

 

Clearly. The distance changes over time in an elliptical orbit, whether or not you call it a spacetime interval or a rabbit pelt interval.

 

Now, everyone will agree on the spacetime interval between two events, no matter where they are, what they're doing, or how fast they're going. Even if the distance is contracted, the spacetime interval will come out the same.

 

Darn! It was all going so well, and we all agreed until you said, "Even if the distance is contracted..."

Does that mean, “even if earth and sun move closer together as earth moves in its elliptical orbit” ... or does it refer to the more esoteric meaning of "length contraction, as per SR theory " that the distance gets shorter" for some other reason, like observational (FOR) differences? In other words (realism), does the actual distance change with different observational frames or not? Realism says, "not."

[Cap'n Refsmmat]

Darn! It was all going so well, and we all agreed until you said, "Even if the distance is contracted..."

Does that mean, “even if earth and sun move closer together as earth moves in its elliptical orbit” ... or does it refer to the more esoteric meaning of "length contraction, as per SR theory " that the distance gets shorter" for some other reason, like observational (FOR) differences? In other words (realism), does the actual distance change with different observational frames or not? Realism says, "not."

The "actual distance" is s, and no, it does not change with different observational frames. [math]\Delta x[/math] and [math]\Delta t[/math] might, though.

[owl]

Iggy,

You constantly misunderstand and/or misrepresent me, and I am quite tired of it. Now again I must clarify in case someone actually believes you as follows:

In fact, you are at least consistent in your approach. You have made it a frequent argument:

 

* Physical things contract. If relativity has "length contraction" then it requires that length be a physical thing.

* Physical things dilate. If relativity has "time dilation" then it requires that time be a physical thing.

* Malleable mediums curve. If relativity has "space-time curvature" then it requires that space-time be a malleable medium.

No. Realism asserts that physical things do not contract except for obvious natural reasons. Same for the distances between objects, as immediately above.

"Time dilation" refers to clocks slowing down in different circumstances. The "physical process" of "ticking" slows down, and probably all physical processes in the same circumstances as the clocks. Time is not "something" that slows down.

If gravity "curves spacetime" then the obvious ontological question is, "What is IT that gravity curves." Obviously the trajectories of objects are curved by gravity. What does "spacetime curvature" add to that fact? (Nothing.)

 

The "actual distance" is s, and no, it does not change with different observational frames. [math]\Delta x[/math] and [math]\Delta t[/math] might, though.

You also said:

So if I measure the spatial distance between two events, I can call that Delta x. If I measure the time that elapsed between two events, I can call it Delta t.

 

We all know that the distance between earth and sun changes over time because of the elliptical orbit.* The question here is whether it also changes with observational frame, called "length contraction."

 

Then again you invoke the magic of the spacetime (or rabbit pelt) interval, s and say that "it", "actual distance" doesn't change with different observational frames but "delta x" and delta t "might" change.

But delta x is the spatial distance between two events (bodies, in the common vernacular), and it might change with a different FOR?

 

How exactly does this theory make sense in regard to the earth getting closer to the sun in the "length contraction" way. (Ref: * above.)

[md65536]

No. Realism asserts that physical things do not contract except for obvious natural reasons.

Can this be extended to other properties in general, or does it apply only to length?

Would you say that 'Realism asserts that reality consists of only what is obvious'? Or are there "natural reasons" that are not obvious (just none for length)?

 

 

If gravity "curves spacetime" then the obvious ontological question is, "What is IT that gravity curves." Obviously the trajectories of objects are curved by gravity. What does "spacetime curvature" add to that fact? (Nothing.)

But if gravity "curves the trajectories of objects" then the obvious ontological question is, "What is IT that gravity curves."

 

I must be mistaken somewhere, because I thought your argument for why 'GR takes "spacetime" and "makes something of it"' is that GR says that spacetime is curved.

My understanding of that is that if something can be curved, it must be an entity.

You are saying that the trajectories of objects are curved.

Does this mean that the trajectories of objects are entities?

 

 

 

Where have I gone wrong?

[Cap'n Refsmmat]

We all know that the distance between earth and sun changes over time because of the elliptical orbit.* The question here is whether it also changes with observational frame, called "length contraction."

 

Then again you invoke the magic of the spacetime (or rabbit pelt) interval, s and say that "it", "actual distance" doesn't change with different observational frames but "delta x" and delta t "might" change.

But delta x is the spatial distance between two events (bodies, in the common vernacular), and it might change with a different FOR?

 

How exactly does this theory make sense in regard to the earth getting closer to the sun in the "length contraction" way. (Ref: * above.)

[math]\Delta x[/math] is the spatial distance between two events which occur at the same time. (You wouldn't measure the distance between the Earth now and the Sun ten years from now.) Since simultaneity is relative (a logical consequence of the constant speed of light -- I can give a concrete example if you'd like), necessarily spatial distance is as well. But s is not relative.

[owl]

[math]\Delta x[/math] is the spatial distance between two events which occur at the same time. (You wouldn't measure the distance between the Earth now and the Sun ten years from now.) Since simultaneity is relative (a logical consequence of the constant speed of light -- I can give a concrete example if you'd like), necessarily spatial distance is as well. But s is not relative.

Yes, please give a concrete example.

Is “event”, as you use it synonymous with “object” as I use it? (Refer to my recent efforts at ”translation” from relativity lingo into realism plain talk.)

You assert as a fact that "Since simultaneity is relative (a logical consequence of the constant speed of light..."

 

Simultaneity means to me and in most dictionaries, some version of “happening at the same time.” Now IS now, whether one IS here or there, regardless of how long it takes light (and information) to travel from here to there. Make sense so far? If that seems wrong, how do you think it is wrong?

Then, what does “simultaneity is relative” mean in the above context?

As I have said before, the constant speed of light can not make the earth change diameters or the meter rod contract to 12 cm or the “actual distance” between Earth and Sun contract to 1/8th of its astronomically verified distance. So where does that leave the length contraction argument as pertains to the observed solar system?

 

Please answer the above as directly as possible in English without the debated math concepts by which Earth either morphs drastically (to accommodate different FOR measurements) or by which no accurate knowledge about its measurements is possible. (As per "no preferred FOR, and each is different.")

Thanks.

I'll try to get back to arguments proposed by others soon.

 

You say, "Delta x[/math] is the spatial distance between two events which occur at the same time."

 

Maybe my (supposed) confusion arises from the special usage of "events" here. That is why I tried to clarify the difference between objects, like sun and earth, their relative position (distance between) at any given time and how you use "event." The act of measuring could be called an "event" too, but that would really muddy the waters.

Earth and Sun both exist right now at the same time, and right now there is a given "actual distance" between them which does not depend on... lets just call it FOR.

If we measure that distance a few months from now (forget 10 yrs... It might be in the same orbital position...), it will be different, because its orbit is not a perfect circle.

 

Cap ‘n R:

No. A spacetime interval can be calculated without the notion of spacetime existing:

 

s^2 = (Delta x)^2 - (c Delta t)^2

 

This can be done only with knowledge of the speed of light, the distance separation between two events, and the time between those two events.

All one needs is the notion of a distance between events and a time between events.

 

What does “the time between events mean?”

The time between the event of breakfast and dinner may be so many hours. When you call the earth an “event” and the sun “an event”, what would the “time between them” mean... just signal delay for light’s travel? The distance between them only changes trivially over time because of the out of round orbit.

 

Backing up to replies in post 309 by Schrodinger’s hat:

(Sorry for the delay. It has been a busy thread.)

 

I need only assume that there are 3 space-like degrees of freedom, and one time-like degree of freedom. No ontology is implied, merely that it can be described as a vector space.

 

I know it is common relativity lingo, but really!... Space-like and time-like? What is the reason for the hedge? Space has three dimensions, not "space-like" dimensions. And time is... “like”... what elapses as things move. Yes, things moving through space can be described as having a vector or trajectory through space.

 

S's hat:

I see no way in which 'empty volume' is any more of a descriptor of what space is than just calling it space.

 

Many cosmologists think that space is *something* that expands, as distinguished from the obvious fact that things in (empty) space/volume move away from each other.

 

Same goes for time. What do you mean duration? Then what do you mean by ____

Eventually we just get back to 'some measure of change' or 'something measured with clocks.

 

I mean to assert that “time dilation” and the “time” part of “spacetime” are only artifacts of measurement. Duration is elapsed time from “tick” to “tick” or from sunrise to the next sunrise at a given surface location on Earth... or from one “now” to another during any physical process.

 

If you wouldn't mind, I'd prefer to take pragmatic definitions

space: 'the thing we measure with meter sticks' and

time: 'the thing we measure with clocks'

Whatever they happen to be.

 

Spacetime can be 'the thing, or things that we measure with clocks and meter sticks'. Whether space and time are somewhat interchangable (thus 'thing'), or completely separate entities ('things')

 

As a realist and an ontologist (asking “What is it?” in all cases), I do mind.

Both cases above are meaningless tautologies, asserting that space (distance) is “what meter sticks measure” , and time is “what clocks measure.” It tells us nothing about either except that they are conventions of measurement.

In the real world, 8+ light minutes is the distance between Sun and Earth, using lightspeed as a constant for actual distance traveled through space in a conventional time unit.

Me:

I agree that the "universe has three dimensions of space and one dimension of time," though I would not call the time required for all movement a "dimension."

 

Schrodinger's hat:

Will you at least concede that it's a dimension in the mathematical sense, in that it's a degree of freedom which is independant (again, mathematical definition -- as in orthogonal) from the three spatial degrees of freedom, and that it is required to describe events?

This is what I (and most physicists -- when they are not discussing the ontology of space and time at least) mean when I say dimension.

 

Yes. I just have a beef with designating “dimensions” beyond 3-D space (and time as event duration), because M-Theory has abused the concept of dimensions to the point that there are seven of them posited beyond the above four with no empirical bases whatsoever. Yet it pretends to be science.

 

Well, I didn’t get all the way through your post 309, but that’s all for now.

Edited September 13, 2011 by owl

[Cap'n Refsmmat]

Is “event”, as you use it synonymous with “object” as I use it? (Refer to my recent efforts at ”translation” from relativity lingo into realism plain talk.)

As I said: An "event" is an object being in a specific place at a specific time. Events have not just a location but a time.

 

An event might be an explosion, for example, which occurs at a specific place and only at one very specific time. An object exists over a length of time, and hence consists of many separate events.

 

What does “the time between events mean?”

The time between the event of breakfast and dinner may be so many hours. When you call the earth an “event” and the sun “an event”, what would the “time between them” mean... just signal delay for light’s travel?

If I measure the Sun's position right now, that is a single event. Its position four hours from now is a separate event. Those two events are four hours apart in time.

 

Just like if I blow something up now, then blow it up again tomorrow, there's a time between those two events, even though it's the same thing I'm blowing up.

 

Yes, please give a concrete example.

 

Righto. Imagine this situation: I am standing in the middle of a large room, ten meters wide, exactly between two walls. I have two laser pointers which I point at the opposite walls and fire simultaneously. The light from each laser pointer travels five meters to the wall and hits it.

 

This is the diagram showing the situation:

 

 

Position is in meters. I'm measuring time in funky units, such that light travels one meter in one unit of time; the diagram is clearer that way. Clearly it takes five units of time for the light to reach the walls. I've marked the five-unit time with a dashed line so you can see the light reaches the walls simultaneously.

 

Before I move on: is this situation clear and coherent? Does the diagram make sense? I don't want to jump in deep without being sure you understand.

 

(edited for clarification and adjusted diagram)

[Schrödinger's hat]

I know it is common relativity lingo, but really!... Space-like and time-like? What is the reason for the hedge? Space has three dimensions, not "space-like" dimensions. And time is... "like"... what elapses as things move. Yes, things moving through space can be described as having a vector or trajectory through space.

I say space-like, as in like the thing we measure with metre sticks, because we have to treat them differently from the time-like dimension under transformations.

This is true of both the Galilean transformation (which does not involve length contraction etc) and the Lorentz transformation.

 

I assert only that (whatever they are ontologically) they behave in a way that matches the behavior of certain mathematical objects. The careful wording is because these mathematical objects behave slightly differently (although you can compare, and in some cases -- according to relativity --they will contribute to one another).

One example is the interval we keep talking about [math] (\Delta s)^2 = (\Delta ct)^2 - (\Delta x)^2 - (\Delta y)^2 - (\Delta z)^2[/math]. You have to treat one dimension differently from the others.

Many cosmologists think that space is *something* that expands, as distinguished from the obvious fact that things in (empty) space/volume move away from each other.

 

Within the strict bounds of GR (rather than some interpretation of the theory) this is because the contribution due to one part of the theory (the part that changes our coordinate system) is different to the other part (the part from their momentum-energy).

This statement is like pointing to someone who does electrodynamics on a macro scale, and saying, "Ha! See! Scientists don't believe in atoms!" because the words they use in papers and textbooks talk about matter as if it were continuous.

Some people elevate space-time to thingyness and say that it's an entity which is expanding. It's a useful conceptual tool and as long as your definition of what type of thing it is does not contradict the data (and the mathematical model you are using based on that data) you are free to interpret how you wish.

 

 

As a realist and an ontologist (asking "What is it?" in all cases), I do mind.

Both cases above are meaningless tautologies, asserting that space (distance) is "what meter sticks measure" , and time is "what clocks measure." It tells us nothing about either except that they are conventions of measurement.

In the real world, 8+ light minutes is the distance between Sun and Earth, using lightspeed as a constant for actual distance traveled through space in a conventional time unit.

I'm sorry, this isn't a discussion on ontology, that was the other thread. Trying to ask what something is before you've established how it works, or whether it is the same type of thing as another is premature.

The topic here is whether or not SR implies reality is subjective. I don't see the what of time and space being relevant compared to the how.

I gave these definitions to distinguish time from -- say -- a unicorn. These definitions are sufficient to talk about it, and to get some time from reality into our mental/mathematical model.

Other than that I have no idea what they are, nor does your definiton of empty volume and duration between events seem in any way meaningful to me. This is probably because I have a different definition of the words than you. This is why I supplied a pragmatic definition in the first place.

Perhaps you can agree with a slightly weaker definition?

 

Time is at least the thing that is measured with clocks.

Space is at least the thing that is measured with meter sticks.

 

Whether or not they apply to the tie-dyed rabbit pelt or empty volume and duration.

Upon reflection on my response to tar, I would also like to make these a bit more specific.

 

Time is at least the thing that is measured with stationary clocks -- whether or not moving clocks measure the same thing.

Space is at least the thing that is measured with stationary meter sticks -- whether or not moving meter sticks measure the same thing.

 

With the same caveat that no Ontology is implied.

 

Yes. I just have a beef with designating "dimensions" beyond 3-D space (and time as event duration), because M-Theory has abused the concept of dimensions to the point that there are seven of them posited beyond the above four with no empirical bases whatsoever. Yet it pretends to be science.

 

Well, I didn't get all the way through your post 309, but that's all for now.

 

Whether or not it is classifyable as science (I know of no testable predictions -- but that may have changed), M-theory is completely irrelevant to the discussion at this point. You're trying to skip a century of work of some of the world's brightest minds, when you refuse to even accept the predicates of SR for the sake of argument for long enough to comprehend the theory.

 

I mean to assert that "time dilation" and the "time" part of "spacetime" are only artifacts of measurement. Duration is elapsed time from "tick" to "tick" or from sunrise to the next sunrise at a given surface location on Earth... or from one "now" to another during any physical process.

Well this is actually useful for moving the discussion forward.

How do you define the reference frame from which all measurements should be taken?

Edited September 14, 2011 by Schrödinger's hat

[owl]

As I said: An "event" is an object being in a specific place at a specific time. Events have not just a location but a time.

 

An event might be an explosion, for example, which occurs at a specific place and only at one very specific time. An object exists over a length of time, and hence consists of many separate events.

 

 

If I measure the Sun's position right now, that is a single event. Its position four hours from now is a separate event. Those two events are four hours apart in time.

 

Just like if I blow something up now, then blow it up again tomorrow, there's a time between those two events, even though it's the same thing I'm blowing up.

Thanks for the clarification. An event is an object or happening with a "timestamp." How is that different (if it is) than my example of sun-earth distance-between-objects right now (with timestamp on measurement) and a few months from now (new timestamp) showing a bit different distance-between-objects?

(Still working toward establishing that that distance does not (actually) vary to extremes with different FORs, but just with position in orbit.

 

Before I move on: is this situation clear and coherent? Does the diagram make sense? I don't want to jump in deep without being sure you understand.

Yes. Frankly, it is ultra-simple, and I wish you would forget the baby-steps and just make your case. Seems we have been here before with your several diagrams of the moving flashlight and observer... claiming length contraction... and my counter argument (not addressed) in a quasi-real*-world setting one AU long (*the well established average sun-earth distance.)

 

But, please do proceed anyway.

 

Schrodinger’s hat:

 

Other than that I have no idea what they are, nor does your definiton of empty volume and duration between events seem in any way meaningful to me. This is probably because I have a different definition of the words than you. This is why I supplied a pragmatic definition in the first place.

(my emphasis)

 

My point in defining time as event duration for physical events (with examples) and space (in its linear dimension) as the distance between real objects in space... is to demonstrate that time is not something that slows down (as per “time dilation”), even though physical processes (like clocks ticking) slow down in certain circumstances,... and that the real distance between objects (like sun and earth) does not vary to extremes with the FOR from which they are measured, as length contraction would have it.

This is relevant to the thread topic in that my above argument grants reality to physical objects, the distances between them, and the elapsed time for those processes to happen, independent of whether or not any of the above are measured or from what FOR.

 

Still addressing Schrodinger's hat's post from last page, you said:

None of these is any more correct than the others. There is no absolute angle which all measurements are correct in.

 

In a limited sense, this supports the length contraction argument that there is no reality to distances between objects independent of measurement.

You totally ignore my thought experiment in support of realism, as follows:

If there were no intelligent life observing cosmos from different frames of reference, objects would still be moving, and that requires "time" even if there were no clocks measuring any/all such event duration. The (moving) positions of all objects in space would remain "as is" regardless of any theoretical frame of reference from which they are observed.

 

The earth-sun distance has a "life (reality) of its own" and the distance varies with earths (elliptical) orbital position, not with how it is measured from different FORs.

This point directly addresses the thread topic.

Edited September 14, 2011 by owl

[Cap'n Refsmmat]

Thanks for the clarification. An event is an object or happening with a "timestamp." How is that different (if it is) than my example of sun-earth distance-between-objects right now (with timestamp on measurement) and a few months from now (new timestamp) showing a bit different distance-between-objects?

(Still working toward establishing that that distance does not (actually) vary to extremes with different FORs, but just with position in orbit.

Roughly the same idea. We must simply take into account the time of observations. I think we agree.

 

Yes. Frankly, it is ultra-simple, and I wish you would forget the baby-steps and just make your case. Seems we have been here before with your several diagrams of the moving flashlight and observer... claiming length contraction... and my counter argument (not addressed) in a quasi-real*-world setting one AU long (*the well established average sun-earth distance.)

 

But, please do proceed anyway.

Righto. Let us suppose that my room is actually on a railroad car moving down the tracks, and you're watching. You watch to see the path of the light and the path of me, over time:

 

 

I'm on a railroad car moving to the left, as you can see. The walls move as well, because they're attached to the railroad car. The light emitted by my laser travels at the speed of light and hits the walls. One light pulse hits just after four units of time, the other just after six.

 

Had you seen the speed of light change between reference frames -- just like my speed is 0 in my frame and nonzero in yours -- it would all match up, and the light pulses would hit at the same times. Unfortunately, the speed of light is constant for everyone.