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Author Topic: That length contraction does not apply to large objects (or distances)  (Read 16121 times)

Offline butchmurray

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Here Einstein states that the content of the relatively moving frame is not judged as contracted by an observer within that frame.
The earth, The Michelson Morley experiment etc. is contracted as judged by the observer in a frame chosen as the “at rest” reference and the extent of that contraction is a function of the velocity of the earth compared to or relative to that particular observer.

Albert Einstein (1879–1955).  Relativity: The Special and General Theory.  1920.
XVI.  Experience and the Special Theory of Relativity - Paragraph 7
http://www.bartleby.com/173/
“Here the contraction of moving bodies follows from the two fundamental principles of the theory without the introduction of particular hypotheses; and as the prime factor involved in this contraction we find, not the motion in itself, to which we cannot attach any meaning, but the motion with respect to the body of reference chosen in the particular case in point. Thus for a co-ordinate system moving with the earth the mirror system of Michelson and Morley is not shortened, but it is shortened for a co-ordinate system which is at rest relatively to the sun.”

Einstein’s gives a complete explanation of this concept.


By the way, I found a typographical error in section XII paragraph 1 near the end. “For the velocity v=0 we should have …” should be “For the velocity v=c we should have …”

Butch
 

Offline old guy

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butchmurray,
Here is an example of the difference between claims of large scale length contraction and realism, which, unlike Einstein, recognizes a "real world" existing and having intrinsic properties independent of observation, let alone differences in observation claiming corresponding differences in objects and distances observed.

As I said yesterday to David:
"A near 'c' fly-by of Earth-and-Sun (edit: observing a shorter AU) would not change the AU from its average 93 million miles..." Do you agree?

A near 'c' fly-by of Earth would not change its diameter from nearly 8000 miles to, say around 1000 miles in the direction of flight. Do you agree.
(Obviously it does not have both diameters, so one must be correct and the other incorrect, right?)

A rigid metallic "probe" approaching Earth at 86.6% of 'c' and observed from Earth to be 10 meters long will not fit in a shuttle cargo bay 10 meters long sent to retrieve it, even for an instant. Do you agree (that its true and immutable length... short of being crushed... is 20 meters?)

Do you agree that real forces are required to make real objects change shape/ length and real distances between objects shrink, i.e., to make objects move closer together? (Length contraction posits no such force involved in objects changing shapes or lengths or to move stars closer together in space.)

Thanks.
« Last Edit: 24/09/2012 19:15:37 by old guy »
 

Offline David Cooper

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Lets take this to the most basic level which no one can deny (well... almost no one.)
I said:
"The paradoxical property of constant ‘c’ does not re-create all physical objects and the distances between them into malleable effects of variable observation/ measurement.'
You said;
"There's nothing paradoxical about it."

Do you agree that physical objects like Earth and spacecraft exist and have properties like shape and size independent of observation?

I personally agree with that.

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Same question in  reverse: Do you think that Earth changes shape as a result of how it is observed?

No.

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If not, do you think that the craft can BE both 20 meters and 10 meters long or that the Earth can have both a nearly 8000 mile diameter and a 1000 mile diameter... in the direction of an observing high speed frame, of course?
If so, do you experience cognitive dissonance as you claim both to be true?
Do you deny that there is a real world independent of observation?

In a Lorentzian universe it may be 20m long at rest and 10m long while moving at 0.866c through the fabric of space. In SR it can arguably be 20m long in absolute terms (many people in the SR camp don't agree with that, but it's fully compatible with SR none the less) and effectively other lengths (including 10m) in other frames.

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Quote
"Realists look at the MM experiment and conclude that length contraction is real. At that point, they either shift into the SR or Lorentzian camp. Your answer to MM appears to be to ignore it and pretend it isn't there, but it most certainly is there and it shows you to be wrong. That's why your babble belongs in the backwaters of science forums.

A realist will answer my first two questions above in agreement with the first and denying the second. A realist will not agree that differences in observation require differences in that which is observed. They must ask by what means is a planet is squished flat and a spacecraft built 20 meters long is contracted to 10 meters, for whatever brief time in a theorist's mind. For a realist things do not change with how they are observed. Do you get at least that much of the argument from realism? If not, this is a totally futile exercise in communication.

I consider the Lorentzian universe to be the real realism - it has taken the MM experiment into account and corrected an old assumption which was demonstrated to be wrong. That assumption was that if you accelerate something to high speed it will remain the same length, but in reality it doesn't happen because the increased distance that forces have to travel to complete round trips within an object that is moving automatically results in all the points of balance in forces between atoms being moved closer together in the direction of travel, and that's the physical mechanism for the length contraction - you would actually need to introduce new stretching forces to maintain the original length of an object as you accelerate it and ramp them up the faster it travels.
 

Offline old guy

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Me:
   " Do you agree that physical objects like Earth and spacecraft exist and have properties like shape and size independent of observation?'
David:
"I personally agree with that."

Great! How could one not agree, except Einstein, of course, for whom observation is reality.
Me:
"Same question in  reverse: Do you think that Earth changes shape as a result of how it is observed?"
You:
"No."
Excellent. Now we are communicating.
You:
Quote
In a Lorentzian universe it may be 20m long at rest and 10m long while moving at 0.866c through the fabric of space. In SR it can arguably be 20m long in absolute terms (many people in the SR camp don't agree with that, but it's fully compatible with SR none the less) and effectively other lengths (including 10m) in other frames.

I suggest we speak our own minds and leave Lorentz out of it until we sort it out.
If the probe doesn't actually change in length as a result of observation, then what Lorentz believed is moot. And "the fabric of space" is not an established entity. It may well be just 3-D volume with "stuff" in it moving around, which, of course "takes time." And "...effectively other lengths in other frames..." again asserts observation as the definition of what is real, ignoring that the probe was built and remains 20 meters long regardless of how it is observed.
You:
"I consider the Lorentzian universe to be the real realism ..."

In case you haven't noticed, this conflicts with your first two replies quoted above.
 

Offline David Cooper

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You:
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In a Lorentzian universe it may be 20m long at rest and 10m long while moving at 0.866c through the fabric of space. In SR it can arguably be 20m long in absolute terms (many people in the SR camp don't agree with that, but it's fully compatible with SR none the less) and effectively other lengths (including 10m) in other frames.

I suggest we speak our own minds and leave Lorentz out of it until we sort it out.
If the probe doesn't actually change in length as a result of observation, then what Lorentz believed is moot. And "the fabric of space" is not an established entity. It may well be just 3-D volume with "stuff" in it moving around, which, of course "takes time." And "...effectively other lengths in other frames..." again asserts observation as the definition of what is real, ignoring that the probe was built and remains 20 meters long regardless of how it is observed.

What's your 3D volume without a fabric to enforce distance and to restrict the speed of light to c? SR has a fabric of space called Spacetime, and the old theory before Lorentz and Einstein came up with theirs had a fabric of space too. Remove it at your peril. We're currently working with three theories, or four or more if you want to make even more up with no fabric of space, but most of them are broken and therefore wrong.

Quote
You:
"I consider the Lorentzian universe to be the real realism ..."

In case you haven't noticed, this conflicts with your first two replies quoted above.

Where does it conflict with them? Let's have a look:-

Quote
Me:
   " Do you agree that physical objects like Earth and spacecraft exist and have properties like shape and size independent of observation?'
David:
"I personally agree with that."

I didn't say that their shape and size can't be changed by movement. If you change the speed of either object, it will have a new shape and size which is independent of observation.

Quote
Me:
"Same question in  reverse: Do you think that Earth changes shape as a result of how it is observed?"
You:
"No."

I can't see any sign of even an imagined contradiction there.
 

Offline old guy

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 Me:
       " Do you agree that physical objects like Earth and spacecraft exist and have properties like shape and size independent of observation?'
  David:
Quote
I personally agree with that....

I didn't say that their shape and size can't be changed by movement. If you change the speed of either object, it will have a new shape and size which is independent of observation.

But you agree that no force is applied. So how do you change the speed of either object without applying the force of acceleration? Maybe you hadn't thought that through. I suggest that you do.
 Then, can that force squeeze the Earth down to 1/8th or so of its spherical diameter. That is a lot of squeezed atoms with no force applied,... by what, ...accelerating Earth to near 'c' relative to the solar system. It makes no sense.
 Me:
    "Same question in  reverse: Do you think that Earth changes shape as a result of how it is observed?"
    You:
    "No....
I can't see any sign of even an imagined contradiction there.”

Like... Earth changes shape with no force applied. That is a clear sign of contradiction. So is the imaginary acceleration of Earth to near 'c' and then claiming that no force is applied.

I am losing patience again with this conversation.
 

Offline butchmurray

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"A near 'c' fly-by of Earth-and-Sun (edit: observing a shorter AU) would not change the AU from its average 93 million miles..." Do you agree?

A near 'c' fly-by of Earth would not change its diameter from nearly 8000 miles to, say around 1000 miles in the direction of flight. Do you agree.
(Obviously it does not have both diameters, so one must be correct and the other incorrect, right?)
The distance between the observer and the moving frame or body is of absolutely no consequence. For an observer on earth the diameter of earth does not ever change because the velocity of one relative to the other is zero. For the observer at the near c velocity, that observer is at relative rest and the earth is in relative motion at near c. Therefore, the diameter of the earth in the direction of motion and its distance to the sun (if the earth and the sun are not in motion relative to each other) is contracted judged by that observer who is at relative rest.

Quote
A rigid metallic "probe" approaching Earth at 86.6% of 'c' and observed from Earth to be 10 meters long will not fit in a shuttle cargo bay 10 meters long sent to retrieve it, even for an instant. Do you agree (that its true and immutable length... short of being crushed... is 20 meters?)
At the moment the probe enters the cargo bay the relative velocities of the two better be near zero, in which case neither is contracted relative to the other. So, if it fits when both are at relative rest, it fits.

Quote
Do you agree that real forces are required to make real objects change shape/ length and real distances between objects shrink, i.e., to make objects move closer together? (Length contraction posits no such force involved in objects changing shapes or lengths or to move stars closer together in space.)
Einstein said that the body itself does not contract (Lorentz thought it did) rather; the body is contracted as judged from relative rest.
 

Offline old guy

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butchmurray:
Quote
The distance between the observer and the moving frame or body is of absolutely no consequence. For an observer on earth the diameter of earth does not ever change because the velocity of one relative to the other is zero. For the observer at the near c velocity, that observer is at relative rest and the earth is in relative motion at near c. Therefore, the diameter of the earth in the direction of motion and its distance to the sun (if the earth and the sun are not in motion relative to each other) is contracted judged by that observer who is at relative rest.
My whole criticism of length contraction is that the objects and distances themselves do not change lengths and shapes as they might appear to do as seen from various frames. That is why I keep asking, for instance, how Earth, a solid object, is *supposed* to flatten out (as seen from a near 'c' fly-by) with no application of force to squeeze it out of spherical. I am fine with a theoretical *image of Earth* as a very oblate spheroid in the above case.
Me:
Quote
    A rigid metallic "probe" approaching Earth at 86.6% of 'c' and observed from Earth to be 10 meters long will not fit in a shuttle cargo bay 10 meters long sent to retrieve it, even for an instant. Do you agree (that its true and immutable length... short of being crushed... is 20 meters?)
You:
Quote
At the moment the probe enters the cargo bay the relative velocities of the two better be near zero, in which case neither is contracted relative to the other. So, if it fits when both are at relative rest, it fits.

The "contracted length" of the probe as seen from Earth, approaching at high speed as above, appears to be 10 meters. The cargo bay, as built actually is 10 meters. As the shuttle pulls alongside the probe, the latter is seen as it actually is, 20 meters. Its velocity relative to Earth had made it appear contracted to half its actual length.

This was the best example I could think of to show the difference "in the real world" between "length contracted" in appearance and actual length.
Length contraction advocates deny this difference.
You:
Quote
Einstein said that the body itself does not contract (Lorentz thought it did) rather; the body is contracted as judged from relative rest.

Einstein said:
Quote
It appears to me that “real” is an empty meaningless category (drawer) whose immense importance lies only in that I place certain things inside it and not
certain others.
So, what is "the body itself" in this context since he denies the meaning of "real" and says that "reality" depends on observation.

I of course agree that "the body itself does not contract," but the folks who run this show demanded that such a non-mainstream view belongs here in the obscure "backwaters" of the forum, not in the serious physics section.
 

Offline old guy

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David Cooper:
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What's your 3D volume without a fabric to enforce distance and to restrict the speed of light to c? SR has a fabric of space called Spacetime, and the old theory before Lorentz and Einstein came up with theirs had a fabric of space too. Remove it at your peril....
What "peril?"
"Stuff" exists and moves through space and there is space between such things.
What in that requires "enforcement?" Light naturally travels at constant 'c' through space without something "restricting" it to this finite velocity.

Minkowski invented "the fabric of spacetime," and then Einstein endorsed it and built the GR theory of gravity around mass curving "spacetime."(It remains merely an abstract concept describing a coordinate system incorporating 3-D space and time to account for movement.
The problem is that physics abhors ontology, so nobody ever address the questions, "What is space?" (besides the obvious 3-D volume), "What is time" (besides the concept of 'that which elapses' as things move in space), and "What is spacetime?" (the coalescence of the two "non-entities" as examined in a paper by Brown and Pooley, "Minkowski's spactime; a glorious non-entity.")
 

lean bean

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My whole criticism of length contraction is that the objects and distances themselves do not change lengths and shapes as they might appear to do as seen from various frames. That is why I keep asking, for instance, how Earth, a solid object, is *supposed* to flatten out (as seen from a near 'c' fly-by) with no application of force to squeeze it out of spherical. I am fine with a theoretical *image of Earth* as a very oblate spheroid in the above case.

show demanded that such a non-mainstream view belongs here in the obscure "backwaters" of the forum, not in the serious physics section.

Old wrinkly guy
You were told 23 days ago by lightarrow that lengths in your rest frame (your choosen rest frame being earth) don't change. It's only from other frames of reference travelling at high speeds relative to earth that lengths on earth change.

If you are still with respect to Earth, every Earth's dimension has a value, in your frame of reference; if you are moving with resperct to Earth, those dimensions are different, as measured in that new frame of reference (because of #).
In relativity you *cannot* say: "the lenght is 2 metres", you have to say: "the lenght is 2 metres as measured in this specific frame of reference".

Old guy, is this you asking on another forum and receiving the same answer back in February? mik
http://www.physforum.com/index.php?showtopic=38507








« Last Edit: 25/09/2012 20:04:58 by lean bean »
 

Offline David Cooper

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But you agree that no force is applied. So how do you change the speed of either object without applying the force of acceleration? Maybe you hadn't thought that through. I suggest that you do.

You are the one who keeps failing to think things through. You accelerate an object to change its speed, but that acceleration is not responsible for contracting its length, as you should realise if you rotate a moving object - the contraction happens in the direction of travel of the object, so a rotating ship which is length-on to the direction of travel, then side-on to it, then length-on again, etc. will have its length contracted first, then it will have its width contracted instead while its length is restored, then its length will contract again as its width is decontracted, etc.

The contraction is caused by the atoms sitting more closely together in the direction of travel due to the altered communication distances between them. This has been explained to you several times now, but you simply ignore it every time and repeat your old rubbish.

Quote
Me:
    "Same question in  reverse: Do you think that Earth changes shape as a result of how it is observed?"
    You:
    "No....
I can't see any sign of even an imagined contradiction there.”

Like... Earth changes shape with no force applied. That is a clear sign of contradiction. So is the imaginary acceleration of Earth to near 'c' and then claiming that no force is applied.

There is absolutely no need for any extra force to be applied - it's all down to a change in the distances between atoms where the existing forces balance, and that's caused by the extra distance the force carriers have to go to complete round trips. It seems you're incapable of getting that point though.

Quote
I am losing patience again with this conversation.

That'll be why you're so bad at learning anything - you get it all handed to you on a plate with multiple explanations from many people who do understand it, and you just insult them and tell them they're wrong on the basis of faulty assumptions.

"Stuff" exists and moves through space and there is space between such things.
What in that requires "enforcement?" Light naturally travels at constant 'c' through space without something "restricting" it to this finite velocity.

What do you imagine that space is? Literally nothing? If there's literally nothing there, there can be no distance between things through this nothing - you would be able to step straight off the moon onto Mercury because there would be next to nothing between them. In reality, there are distances between things which must be enforced by a space fabric of some kind. And what in your nothing do you imagine can restrict the speed of light to c?

Quote
Minkowski invented "the fabric of spacetime," and then Einstein endorsed it and built the GR theory of gravity around mass curving "spacetime."(It remains merely an abstract concept describing a coordinate system incorporating 3-D space and time to account for movement.

The fabric of space is a better description of what used to be called aether, but aether sounds far too liquidic and would require a fabric of space to contain it, so it's best to ditch all suggestions of a liquid and call it something which describes more accurately what it needs to be.

Quote
The problem is that physics abhors ontology, so nobody ever address the questions, "What is space?" (besides the obvious 3-D volume), "What is time" (besides the concept of 'that which elapses' as things move in space), and "What is spacetime?" (the coalescence of the two "non-entities" as examined in a paper by Brown and Pooley, "Minkowski's spactime; a glorious non-entity.")

There are so many possible answers that this is usually pushed into philosophy, and rightly so as it's almost all speculation with nothing to back it up. However, space is some kind of fabric, Newtonian time is tied to the speed of light through this fabric (though it may actually have an external origin where superluminal speeds may be normal), and Spacetime is an interpretation of the universe in which time is thought of as a dimension. To call it a non-entity is ridiculous - it may be that all matter and energy is simply a rippling of the space fabric, so it's the fabric of space which may be of much more real substance that either of those things.
 

Offline David Cooper

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Old guy, is this you asking on another forum and receiving the same answer back in February? mik
http://www.physforum.com/index.php?showtopic=38507

That does sound like him, and he does have a good point about the atmosphere being length-contracted so that the muon can reach the ground. What he needs to do is look at the different theories that are available and work out which one explains it best. His own theory is broken because it doesn't take length contraction into account, thereby allowing itself to be disproved by the MM experiment. There's no point in him telling other people to remove splinters from their eyes until he's dealt with the ruddy great plank sticking out of his own.
 

Offline old guy

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Just another quickie. Sorry, no time 'til later.
David:
"What do you imagine that space is? Literally nothing?"

I imagine space as volume with three axes/dimensions. Distance is the linear component of this volume. There are (grammar edit) about 93 million miles of distance (space) between Earth and Sun. It varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.
More later as time permits. And, yes, my user name was "mik" in the link cited. I quit that forum because it was such a dog fight with science as secondary and personal insults as the battle that most participants there seemed to relish.
 

Offline David Cooper

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I imagine space as volume with three axes/dimensions. Distance is the linear component of this volume. There are (grammar edit) about 93 million miles of distance (space) between Earth and Sun.

So how do things know where they are relative to other things to work out whether to bump into them or not? Do they all keep a record of their coordinates and keep asking all the other objects to tell them theirs so that they can work out what or whether to do anything with them? That works in a computer simulation, but it's a much more complicated way of doing things than having an actual fabric of space imposing location directly on the things travelling through it.

Quote
It varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.

That means it's a broken model then as it can't handle the result of MM.
 

Offline old guy

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I imagine space as volume with three axes/dimensions. Distance is the linear component of this volume. There are (grammar edit) about 93 million miles of distance (space) between Earth and Sun.

Quote
So how do things know where they are relative to other things to work out whether to bump into them or not? Do they all keep a record of their coordinates and keep asking all the other objects to tell them theirs so that they can work out what or whether to do anything with them? That works in a computer simulation, but it's a much more complicated way of doing things than having an actual fabric of space imposing location directly on the things travelling through it.

Huh? Do you need basic astronomy lessons and don't know that gravity works to hold the planets in their elliptical orbits around the Sun? Earth orbits the Sun just fine without a man-made coordinate system to follow for instructions!

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It varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.

Quote
That means it's a broken model then as it can't handle the result of MM.
Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?

Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?
 

Offline David Cooper

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Huh? Do you need basic astronomy lessons and don't know that gravity works to hold the planets in their elliptical orbits around the Sun? Earth orbits the Sun just fine without a man-made coordinate system to follow for instructions!

So you don't have everything storing its position as coordinates, and you don't have a fabric of space either, but you do have a volume of space which serves exactly the same role as a fabric of space by enforcing distances. My point was that your volume of space is not mere nothing - it must be a fabric of space if it is to perform the role that you have it performing.

Quote
Quote
Quote
It varies a bit with Earth's position in its elliptical orbit but not with differences in how that distance is observed by varying frames of reference.

That means it's a broken model then as it can't handle the result of MM.

Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?

My comment referred to the second part of your original quote and not to the first part.

Quote
Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?

Our measurements don't change the physical arrangement of anything - merely their apparent arrangement. The idea that observing things from different frames physically changes the thing being observed is exclusive to an extremist group within SR and you are wasting your time attacking it - it is not mainstream anything. In a Lorentzian universe though, the Earth could really be much closer to the sun during parts of its orbit than we think it is (dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space), but the heat reaching the Earth from the sun would be no different from normal due to the concentration of heat and light forwards in the direction of travel and the extra distance through space it would have to cover to reach the Earth if the Earth is moving ahead of it.
 

Offline old guy

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David:
Quote
So you don't have everything storing its position as coordinates, and you don't have a fabric of space either, but you do have a volume of space which serves exactly the same role as a fabric of space by enforcing distances. My point was that your volume of space is not mere nothing - it must be a fabric of space if it is to perform the role that you have it performing.

"Enforcing" is a very strange concept in this context, with absolutely no relevance to the fact that planets orbit the Sun according to the law of gravity, which requires no (metaphorical) "fabric" as an analytical coordinate system. You are clearly not familiar with the many scholarly papers over the years presented at the conferences held by the International Society for the Advanced Study of Spacetime.
You beat on that drum assuming that space, time, and "the fabric of spacetime" exist as entities. Three dimensional volume (space) contains entities, including objects and forces. Space itself is the volume in which entities exist, not itself an entity. Planets are such objects and the gravity which holds them in orbit around the Sun is a force.
Review:
Me:
Quote
Really?! Do you really not understand that as Earth orbits the Sun it is closer at some points and further away at other points in the elliptical path?

Do you think that our measurements change any of that? By what force might the Earth *actually* be moved to, say, 15 million miles from the Sun, if it were so measured from the familiar relativistic fly-by frame? How would Earth then avoid being incinerated?
You:
Quote
Our measurements don't change the physical arrangement of anything - merely their apparent arrangement. The idea that observing things from different frames physically changes the thing being observed is exclusive to an extremist group within SR and you are wasting your time attacking it - it is not mainstream anything.
(my bold again)

If you review this thread you will find that what passes for mainstream SR in this forum holds exactly the position you call extremist. Don't worry about how I spend my time, wasted or not. I have objected to this mainstream position on length contraction for many years, and my participation here is still focused on correcting the misconception that reality (as in the physical examples I use) changes as measurements of things/distances change as observed from different frames of reference.
Please read my comments to you in the other thread and make your arguments in your own thread.
Thanks.

 

Offline old guy

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A detail I didn't mention in yesterday's reply:
Everything you said after "In a Lorentzian universe..." was gibberish.

Quote
In a Lorentzian universe though, the Earth could really be much closer to the sun during parts of its orbit than we think it is (dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space), but the heat reaching the Earth from the sun would be no different from normal due to the concentration of heat and light forwards in the direction of travel and the extra distance through space it would have to cover to reach the Earth if the Earth is moving ahead of it.

"We think it is", as precisely measured from Earth at all points in its orbit, on average about 93 miles from Earth. If Earth were closer, it would be hotter. At 15 million miles away (the theoretically length contracted extreme) it would in fact be incinerated.
None of that has anything to do with "...(dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space)"...
Velocity makes no sense without specifying "relative to what?", and Earth-Sun are in the same frame relative to how our galaxy is moving through space relative to other galaxies and cosmic expansion in general.

So the challenge here in my example is, in the frame of Earth and Sun, how far is Earth from Sun, and does that distance change as a result of theoretical relativistic, fly-by measurements, not in the at rest frame with Earth-Sun. The answer is no. Length contraction as applied to the AU is... well... bogus!


 

Offline David Cooper

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"Enforcing" is a very strange concept in this context, with absolutely no relevance to the fact that planets orbit the Sun according to the law of gravity, which requires no (metaphorical) "fabric" as an analytical coordinate system.

Are you capable of understanding anything? You're mixing two things together that don't belong together and attributing it to me when I made it perfectly clear that they are alternative systems. The coordinate storing system is used in computer games to record where things are so that the program can work out when things need to collide, while the fabric of space is used in the universe, avoiding the need for storing any numbers.

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You are clearly not familiar with the many scholarly papers over the years presented at the conferences held by the International Society for the Advanced Study of Spacetime.

Spacetime is a fabric of space - GR depends on it being distorted.

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You beat on that drum assuming that space, time, and "the fabric of spacetime" exist as entities. Three dimensional volume (space) contains entities, including objects and forces. Space itself is the volume in which entities exist, not itself an entity. Planets are such objects and the gravity which holds them in orbit around the Sun is a force.

It doesn't work without a fabric. Your volume is a fabric, regardless of your inability to recognise a fabric of more than two dimensions. If your volume was literally nothing, it would not be able to dictate separations between things - two things with literally nothing between them must be touching.

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If you review this thread you will find that what passes for mainstream SR in this forum holds exactly the position you call extremist. Don't worry about how I spend my time, wasted or not. I have objected to this mainstream position on length contraction for many years, and my participation here is still focused on correcting the misconception that reality (as in the physical examples I use) changes as measurements of things/distances change as observed from different frames of reference.

What you need to do then is up your game so that you can speak out of knowledge instead of ignorance, and then you'll be able to get your point across and push more of these people into the mainstream SR position held by actual physicists.

A detail I didn't mention in yesterday's reply:
Everything you said after "In a Lorentzian universe..." was gibberish.

Your failure to understand something does not make it gibberish.

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In a Lorentzian universe though, the Earth could really be much closer to the sun during parts of its orbit than we think it is (dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space), but the heat reaching the Earth from the sun would be no different from normal due to the concentration of heat and light forwards in the direction of travel and the extra distance through space it would have to cover to reach the Earth if the Earth is moving ahead of it.

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"We think it is", as precisely measured from Earth at all points in its orbit, on average about 93 miles from Earth. If Earth were closer, it would be hotter. At 15 million miles away (the theoretically length contracted extreme) it would in fact be incinerated.

If the sun is moving at 99% the speed of light, which it could theoretically be, then the Earth's orbit would be extremely narrow in the direction of travel, but it would not appear to be so when viewed from the Earth - our measurements of the distance to the sun would remain between 91 and 95 million miles and we would be completely unable to tell that that was not the case. If you don't even understand that, then you probably haven't taken in anything at all.

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None of that has anything to do with "...(dependent on the sun and our galaxy moving at ridiculously but not impossibly high speed through space)"...
Velocity makes no sense without specifying "relative to what?", and Earth-Sun are in the same frame relative to how our galaxy is moving through space relative to other galaxies and cosmic expansion in general.

Through the fabric of space which exists in a Lorentzian universe. If you want to work with a theory that has no fabric of space, you'll lose all separation and end up with a singularity and nothing more than that.

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So the challenge here in my example is, in the frame of Earth and Sun, how far is Earth from Sun, and does that distance change as a result of theoretical relativistic, fly-by measurements, not in the at rest frame with Earth-Sun. The answer is no. Length contraction as applied to the AU is... well... bogus!

In no theory does the real distance change just by moving past the solar system at high speed, but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less if they're aren't lined up at 90 degrees to the direction of travel of the fast-moving observer. The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun.
 

Offline old guy

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Limited time again... just a quick reply to:
"two things with literally nothing between them must be touching..."

You have NO COMPREHENSION of what I already said about that... a "conversation" going nowhere.
I said, answering your direct question, that I "imagine" space to be the 3-D volume in which objects move around, guided by the force of gravity. I also said that distance is the linear component of that 3-D volume. (Do you even know what that means?) So, as solar systems form around stars, planets are formed as nearly spherical (not flattened) and the distances between them are due to where/how the raw materials of each body were distributed as the planets were formed and distributed in space.
The coordinate systems in GR came along a lot later and work very well as tools for predicting the movements of these planets around the Sun, in our case.

You completely distort what I say, either intentionally or because of total failure to understand what I said in the first place*. Since attribute no malice to you (only extreme arrogance and obsession with your own agenda), I will go with the latter.*
« Last Edit: 28/09/2012 21:31:53 by old guy »
 

Offline old guy

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Finishing my reply to D.C. yesterday... and hopefully finishing my conversation with him, though that hope will, no doubt, be in vain!
He said:
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In no theory does the real distance change just by moving past the solar system at high speed, but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less if they're aren't lined up at 90 degrees to the direction of travel of the fast-moving observer. The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun.

Re: "In no theory does the real distance change just by moving past the solar system at high speed..."

That is factually incorrect. Mainstream length contraction theory is based on relativity's dictum that all frames of reference are equally valid, so that when a frame measures an object or distance to be contracted, it IS contracted, not just APPEARS TO BE contracted. The phrase which is always attached as a qualifier is some form of "for observer A"... the object/distance is contracted, while "for observer B" it is quite different in length/shape/distance. The "all frames equally valid" dictum says that a 15 million mile AU (measured from the relativistic speed frame) is equally valid with the standard 93 million mile or so average AU. I have argued that point many times with relativity theorists over the years. Your "in no theory..." statement is false.

Your statement:..."but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less..."
Then you say, "The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun."


Another contradiction: Does faster movement create a shorter pathway (distance) or is does it just "appear to be less...?"  How can a "shortened distance" be "absolutely real" and yet the distance between Earth and Sun has not changed? You are very confused.
Introducing the phrase "for that fast-moving observer" does not change the Reality of the distance between Earth and Sun. Is that so difficult to understand?
This difference, again, is the main issue of my length contraction threads, a difference clearly still lost on you. "For" the fast moving frame the distance traveled/measured may *appear* shorter. That appearance does not make Earth and Sun closer than 93 million miles apart. You still don't get it, and I give up on explaining the difference to you.
 You didn't even get the difference between the *real/actual length* of the "alien probe" (20 meters) and its *apparent (contracted) length*(10 meters.) That difference was why the probe would not fit into the 10 meter cargo bay sent out to capture it. You danced all around that one and still didn't get it. That was a "reality check" on how "real" length contraction is. (Not real; only apparent.)
« Last Edit: 29/09/2012 18:41:56 by old guy »
 

Offline David Cooper

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I said, answering your direct question, that I "imagine" space to be the 3-D volume in which objects move around, guided by the force of gravity. I also said that distance is the linear component of that 3-D volume. (Do you even know what that means?) So, as solar systems form around stars, planets are formed as nearly spherical (not flattened) and the distances between them are due to where/how the raw materials of each body were distributed as the planets were formed and distributed in space.

And that isn't a fabric of space? What's the difference between the two ideas then? Your 3D volume isn't just nothing - it enforces three space dimensions on its contents rather than four or five of them. You have distances enforced by your 3D volume too, so how is there no fabric of space in this? When light travels through your 3D volume, how is it restricted to the speed of light? What is it interacting with that enables it to maintain exactly the right speed while it travels through your 3D volume for billions of years?

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You completely distort what I say, either intentionally or because of total failure to understand what I said in the first place*. Since attribute no malice to you (only extreme arrogance and obsession with your own agenda), I will go with the latter.*

I'm simply trying to help you clarify your thoughts so that you can see where you're making mistakes, and I'm trying to explain two alternative theories to you which don't suffer from as many faults as yours so that you might understand why the old ideas of "realism" were dumped a century ago in favour of new theories which could handle the results of experiments which disproved the old "realism".

Finishing my reply to D.C. yesterday... and hopefully finishing my conversation with him, though that hope will, no doubt, be in vain!

You don't want help then? You don't want to know where you're wrong? You don't want to advance and become right? You'd rather be an old dog who can't learn new tricks?

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Re: "In no theory does the real distance change just by moving past the solar system at high speed..."

That is factually incorrect. Mainstream length contraction theory is based on relativity's dictum that all frames of reference are equally valid, so that when a frame measures an object or distance to be contracted, it IS contracted, not just APPEARS TO BE contracted.

The real distance does not change. If you are moving fast past something, that thing does not change shape on the basis of your moving past it - it is simply contracted (that's a state and not a transformation) in the frame in which you're moving past it. If you change frame and the object appears to have a new shape, you haven't transformed it - you've switched into a frame in which it has a different shape.

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The phrase which is always attached as a qualifier is some form of "for observer A"... the object/distance is contracted, while "for observer B" it is quite different in length/shape/distance. The "all frames equally valid" dictum says that a 15 million mile AU (measured from the relativistic speed frame) is equally valid with the standard 93 million mile or so average AU. I have argued that point many times with relativity theorists over the years. Your "in no theory..." statement is false.

No, it's correct - in no theory do you change an object by changing the frame you're observing it from. In one frame it has one shape, and in another frame it has another shape, but it has those shapes all the time - your jumping from one frame to another doesn't physically change the object at all, but merely allows you to see it as the shape it already has in a different frame.

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Your statement:..."but in SR there will be shorter pathways opened up by that fast movement which make the distance between the Earth and Sun appear to be less..."
Then you say, "The shortened distance for that fast-moving observer is absolutely real, but he has not actually moved the Earth nearer to the sun."

Another contradiction: Does faster movement create a shorter pathway (distance) or is does it just "appear to be less...?"  How can a "shortened distance" be "absolutely real" and yet the distance between Earth and Sun has not changed? You are very confused.

I'm not the one who's confused here, but I can see why you are in this case. Faster movement doesn't create a shorter pathway - the pathway is already there, but it's only accessible by moving fast - that's what I meant by "opened up", but I can see now that it was ambiguous.

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Introducing the phrase "for that fast-moving observer" does not change the Reality of the distance between Earth and Sun. Is that so difficult to understand?
This difference, again, is the main issue of my length contraction threads, a difference clearly still lost on you. "For" the fast moving frame the distance traveled/measured may *appear* shorter. That appearance does not make Earth and Sun closer than 93 million miles apart. You still don't get it, and I give up on explaining the difference to you.

If you ever paid attention to anything you'd have got it by now, but you reject half the picture every time on the basis that I'm pushing my own agenda. I'm not. If you want to understand SR properly, you have to understand the Lorentzian universe properly too so that you can tell which is which - a lot of the stuff that's said about SR is actually a description of the Lorentzian universe and is not SR, so you have to be able to separate the two in the right places. That is why I discuss two theories every time. In a Lorentzian universe, the 93 million miles that you measure may be false due to undetectable length contraction. In SR, every possible frame of reference serves as a Lorentzian universe when measuring things, and all of these frames are said to be equally valid. In the Lorentzian universe there is one correct answer (which can't be pinned down) and all other descriptions are wrong. In SR, all the descriptions are right. Because they are all right in SR, the Earth and Sun really are closer together in some frames, and this does work mathematically if you switch to using non-Euclidean geometry - there really are shorter pathways available in other frames. You are free to reject that if you like and to chuck the whole of SR with it, but if you're wanting answers within SR, there's no point in throwing tantrums when you get the answers that SR provides.

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You didn't even get the difference between the *real/actual length* of the "alien probe" (20 meters) and its *apparent (contracted) length*(10 meters.) That difference was why the probe would not fit into the 10 meter cargo bay sent out to capture it. You danced all around that one and still didn't get it. That was a "reality check" on how "real" length contraction is. (Not real; only apparent.)

Everyone here got it from the start, but the problem was that no one could believe that you really were asking such a stupid question. If you're asking if length contraction is real and set the rules up in such a way that you can only compare the contracted thing with an uncontracted thing by removing the length contraction from the contracted one, of course you aren't going to find any length contraction on it. The question you should have been asking, and which everyone thought you were asking, was much more interesting: is the object really contracted and can it fit in a smaller space than normal while contracted. The answer was yes in a Lorentzian universe, and impossible to decide in SR because of simultaneity issues, but in terms of measurements there is actual contraction.

[I await the flinging of yet more pants on the now-heaving pile.]
 

Offline JP

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Stop personal attacks please.  I'll lock this thread if they continue.
 

Offline simplified

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Someone on the bus should send his photons  at 150 degrees relatively of own motion direction.

Yes - that's what I meant by 60 degrees behind, but you've expressed it better.
And if I am motionless observer then the light(of instant flash) travels by way of one arch of wave(if to not calculate energy waves) relatively of me.Therefore I can see the light under the same mirror angle.
« Last Edit: 30/09/2012 10:52:43 by simplified »
 

Offline David Cooper

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I apologise if anything I've said has been taken as a personal attack. When I describe a question as stupid, it doesn't mean the person who asked it is stupid. We are all capable of asking stupid questions, and I recently asked one here about things being in more than one place at a time (where my way of testing the properties of such a thing would actually have destroyed its ability to be in more than one place at a time). I don't take any of Old Guy's comments as a personal attacks on me either - he is merely expressing frustration with this situation as things don't appear to be getting anywhere, but it is that that makes this particularly interesting as we continue to try to identify a key point where something might be forced to give.
 

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