[GoC (OP)]

   Which do you understand and why?

[jeffreyH]

This is not a trivial question. The answer has significant implications. Time dilation is a definite physical effect and has been confirmed experimentally. It may not be possible to confirm Lorentz contraction in the same way. It is then only via close examination of the mathematics of relativity that an insight can be gained.

[GoC (OP)]

This is not a trivial question. The answer has significant implications. Time dilation is a definite physical effect and has been confirmed experimentally. It may not be possible to confirm Lorentz contraction in the same way. It is then only via close examination of the mathematics of relativity that an insight can be gained.

Exactly! While there is no mechanical reason for contraction there is mathematics that show image contraction.

[guest4091]

An observer is moving with the center of a circle in the x direction.
The first figure shows light arriving earlier from the perpendicular directions than from the x direction of motion, relative to the plane of simultaneity (red).
The second figure is the same except the circle is length contracted in the x direction. The light arrives simultaneously in the plane of simultaneity. Thus the reflection will be a mirror image of the radial emission. The observer sees a simultaneous reflection, even though the reflection occurs over an interval of space and time.

[PhysBang]

This is not a trivial question. The answer has significant implications. Time dilation is a definite physical effect and has been confirmed experimentally. It may not be possible to confirm Lorentz contraction in the same way. It is then only via close examination of the mathematics of relativity that an insight can be gained.

Exactly! While there is no mechanical reason for contraction there is mathematics that show image contraction.

Except that there is mechanical reason for contraction and there is evidence for contraction, i.e., if there was no contraction, one could not have time dilation, since one could not have a consistent theory.

[jeffreyH]

This is not a trivial question. The answer has significant implications. Time dilation is a definite physical effect and has been confirmed experimentally. It may not be possible to confirm Lorentz contraction in the same way. It is then only via close examination of the mathematics of relativity that an insight can be gained.

Exactly! While there is no mechanical reason for contraction there is mathematics that show image contraction.

Except that there is mechanical reason for contraction and there is evidence for contraction, i.e., if there was no contraction, one could not have time dilation, since one could not have a consistent theory.

I have to ask. Contraction of what? It's not that I am necessarily disagreeing with you. It is important to determine exactly what is contracting.

[PhysBang]

J S Bell produced a very nice derivation of length contraction given movement relying on Maxwell's electromagnetism.

Harvey Brown wrote a nice paper about the derivation and its pros and cons. http://cds.cern.ch/record/396878/files/9908048.pdf

[GoC (OP)]

Except that there is mechanical reason for contraction and there is evidence for contraction,

There is no mechanical reason for contraction in SR. Visual image contraction is actually necessary with the finite speed of light and relativistic speeds. The competition of physical vector motion and the speed of light for image length changes in favor of the physical object moving through reflection as less able to reflect. For proof just change the speed of light in the Lorentz contraction and you will recognize its not a physical contraction. Its just a relativistic relationship to the speed of light.

if there was no contraction, one could not have time dilation,

   The clock does not contract. With vector speed there is a geometry distance in space That affects the distance light moves relative to c. This distance slows the tick rate of a clock not contraction.

since one could not have a consistent theory.

Consistency comes from c as a constant. Motion removes a percentage of available c as equivalence to GR dilation in clocks. Both increase the distance light has to travel between ticks.

Rulers and clocks mutually change physically in dilation of GR. That is why Relativity works. if a clock contracted it would tick faster. We have to follow logic in our relativity equations.

[guest39538]

   Which do you understand and why?

A good question which has a variation of answers to an extensive subject. One could understand the Lorentz contraction to have several meanings in it's intent which could lead to ambiguity of thought.
If we were to perceive an object such as a train contracting in physical length when in motion that would be of fallacious thinking. However if we was to look at the distance differences of light relative to the  angle(s) of vision of the moving object then the ''length'' of light is stretched or contracted between observer and the observed.
All objects seen are relative to deception, 3d objects becoming visual 2 dimensional to the observer , the greater the distance the object is viewed away.
Vision is pretty ''flat'' unless the object is in close proximity.
However in saying the above, there still exists volume contraction and volumes tend to  have a length.

[GoC (OP)]

However in saying the above, there still exists volume contraction and volumes tend to  have a length.

How do we measure volume as relativistic? With the use of light. Now if we understand relativity correctly in SR light is independent of the source. So the reflection and the object are in two different special positions when the image is received by an observer.

Two parallel trains at relative rest view each other as perpendicular. Each conductor views the other 90 degrees from the forward vector. There is a unbendable bar between the trains. From the at rest position each train is physically parallel and now traveling half the speed of light. As they approached the half speed of light each conductor viewed the other train as falling behind. The unbendable bar appears to bend towards the trailing train. Why? Because light is independent of the source. The vector of the image between them is no longer 90 degrees from the forward position. It is now 120 degrees from the forward position or 30 degrees behind parallel. The image beyond the train is traveling between the trains. So each conductor views what is behind the opposite train while they are physically parallel.

The Doppler effect does the same thing to light images for the perpendicular observer at relative rest. The observer at rest views the object at half the speed of light at a 120 degree angle rather than a 90 degree angle by the time the image reaches him. So the angle of light as the perpendicular position becomes a 30,60,90 geometry triangle. Cos 30 is 0.866025 contracted view. The Lorentz contraction at half the speed of light is 0.866025 which many consider physical contraction just because the image is contracted. Smoke and mirrors can fool most of us. The visual image is just smoke and mirrors.

[nilak]

If SR is only a visual effect then GR is the same. All you have to do is examine how things work under acceleration then apply the equivalence principle.

[GoC (OP)]

If SR is only a visual effect then GR is the same.

Unlikely, Relativity would not work as it does if rods and clocks did not change with dimensional dilation in GR.

All you have to do is examine how things work under acceleration then apply the equivalence principle.

Equivalence in GR to SR is at a specific point of dilation. You can have 9.8 m/s/s as you approach the speed of light your tick rate continues to slow. But dilation in GR at 9.8 m/s/s has a fixed clock tick rate by dilation of space time specific energy density. Dilation changes the length of rods and clocks as special changes in GR. Geometry shows the image changes in SR with competition between vector mass and light speed. Change the light speed in the Lorentz contraction and the ratio of contraction changes in SR. It is speed of light dependent for contraction Mathematically.

[nilak]

If SR is only a visual effect then GR is the same.

Unlikely, Relativity would not work as it does if rods and clocks did not change with dimensional dilation in GR.

All you have to do is examine how things work under acceleration then apply the equivalence principle.

Equivalence in GR to SR is at a specific point of dilation. You can have 9.8 m/s/s as you approach the speed of light your tick rate continues to slow. But dilation in GR at 9.8 m/s/s has a fixed clock tick rate by dilation of space time specific energy density. Dilation changes the length of rods and clocks as special changes in GR. Geometry shows the image changes in SR with competition between vector mass and light speed. Change the light speed in the Lorentz contraction and the ratio of contraction changes in SR. It is speed of light dependent for contraction Mathematically.

You just said it :"relativity wouldn't work...". That means it is not a visual effectz, it is real.


Time changes between points of different gravitational potential in a gravitational fileld. To have an increase of difference between clocks you need to increase distance between the two objects by free fall at acceleration g.
Under acceleration the same thing happens. Time dilation occurs as seen from a stationary object. The distance between them is increasing by the same acceleration g. If both clocks are in the same ship, the clocks at the bottom will not reduce its frequency over time but it will tick at a fixed frequency lowey that that at the top.

Change the speed of light is GR and rates of contration will change as well.

This looks very weird.

To have the same effect in gravity as in acceletation you need to do the same things.
In a gravity field if there is a fixed distance between two objects the clocks rates difference will remain constant because the object further away is accelerating at the same rate g. (Considering constant gravitational field. You don't need a gravitational field gradient at all). That is the key.

All of these mean if aether existed, an object with mass would pull in aether at an accelerated rate not at a constant rate. Perhaps it does.

[GoC (OP)]

You just said it :"relativity wouldn't work...". That means it is not a visual effectz, it is real.

Not necessarily. You regard relativity as physically real. In GR this is true with dilation. We seem to agree on this point GR changes in rods and clocks is physical. But we probably disagree about the meaning of dilation. An Ether would have to have particles further apart for a clock to slow down. Most scientists would believe more particles will slow light speed. This is because of SR contraction of the visual object.

With geometry we can see a change in the length of rods and clocks. What is interesting, for clocks the distance of added space to fundamental c slows the tick rate of a clock physically. The geometry of vector speed changes the length of your measuring stick as a reflection which becomes longer with added speed. The equivalence is the measuring stick changes your length of the meter exactly the amount to compensate for the clocks tick rate. Because of this the speed of light in a vacuum is always measured to be the same in every frame. The point becomes the measurement of the speed of light which is confounded to be the same relative to tick rate.

In GR dilation the physical size increases and the tick rate decreases. The distance of your meter stick increases and your clock allows more time for light to travel the extra distance. They are confounded also. That is the equivalence between SR and GR. I can show you the math in SR. We can view dilation in galaxies as lensing.

Einstein had trouble because of his belief in rigid mass relative to spacetime. That is the part he could not explain clearly. His gravity curve is 2 dimension description of a 3 dimensional affect.

also c is of space not mass. Electrons do not move themselves. Light is the electron friction to c during a jump to a higher orbit.

Navigating relativity mechanically is the only way to understand it properly.

[nilak]

I think there is a better way to explain this, and you are right, in a way. SR, is pure geometry and only involves time, length and speed and acceleration. GR says gravity is equivalent to acceleration but it is still geometry. All if these explain in fact the reality but at a basic level eve though they are geometric. Then Einstein introduced his equation with tensors still part of GR. These explain things at a level very close to fundamental.

So, yes you can say SR is a visual/geometric explanation of reality and so is GR up to the Einstein field equations.

[jeffreyH]

I think there is a better way to explain this, and you are right, in a way. SR, is pure geometry and only involves time, length and speed and acceleration. GR says gravity is equivalent to acceleration but it is still geometry. All if these explain in fact the reality but at a basic level eve though they are geometric. Then Einstein introduced his equation with tensors still part of GR. These explain things at a level very close to fundamental.

So, yes you can say SR is a visual/geometric explanation of reality and so is GR up to the Einstein field equations.

Special relativity definitely does not include acceleration. That is the whole point of general relativity.

[guest39538]

However in saying the above, there still exists volume contraction and volumes tend to  have a length.

How do we measure volume as relativistic? With the use of light. Now if we understand relativity correctly in SR light is independent of the source. So the reflection and the object are in two different special positions when the image is received by an observer.

Two parallel trains at relative rest view each other as perpendicular. Each conductor views the other 90 degrees from the forward vector. There is a unbendable bar between the trains. From the at rest position each train is physically parallel and now traveling half the speed of light. As they approached the half speed of light each conductor viewed the other train as falling behind. The unbendable bar appears to bend towards the trailing train. Why? Because light is independent of the source. The vector of the image between them is no longer 90 degrees from the forward position. It is now 120 degrees from the forward position or 30 degrees behind parallel. The image beyond the train is traveling between the trains. So each conductor views what is behind the opposite train while they are physically parallel.

The Doppler effect does the same thing to light images for the perpendicular observer at relative rest. The observer at rest views the object at half the speed of light at a 120 degree angle rather than a 90 degree angle by the time the image reaches him. So the angle of light as the perpendicular position becomes a 30,60,90 geometry triangle. Cos 30 is 0.866025 contracted view. The Lorentz contraction at half the speed of light is 0.866025 which many consider physical contraction just because the image is contracted. Smoke and mirrors can fool most of us. The visual image is just smoke and mirrors.

how can light possibly be independent of the source as evidently I turn off the source , I turn off the light , I consider that the light is dependent of the source made by the source?

[nilak]

I think there is a better way to explain this, and you are right, in a way. SR, is pure geometry and only involves time, length and speed and acceleration. GR says gravity is equivalent to acceleration but it is still geometry. All if these explain in fact the reality but at a basic level eve though they are geometric. Then Einstein introduced his equation with tensors still part of GR. These explain things at a level very close to fundamental.

So, yes you can say SR is a visual/geometric explanation of reality and so is GR up to the Einstein field equations.

Special relativity definitely does not include acceleration. That is the whole point of general relativity.

I don't agree. SR can handle accelerations perfectly fine. Equivalence principle is the point, and then filed equations.

[PhysBang]

Except that there is mechanical reason for contraction and there is evidence for contraction,

There is no mechanical reason for contraction in SR.

I know that this fantasy is important to you. However, it is still a fantasy.

For proof just change the speed of light in the Lorentz contraction and you will recognize its not a physical contraction. Its just a relativistic relationship to the speed of light.

That doesn't sound like a proof to me. Change the speed of sound and you will find that sonic booms are not a physical sound, they are just a sonic relationship to the speed of sound.

if there was no contraction, one could not have time dilation,

   The clock does not contract. With vector speed there is a geometry distance in space That affects the distance light moves relative to c. This distance slows the tick rate of a clock not contraction.

A nice collection of words that has no relationship to physical systems.

[PhysBang]

Special relativity definitely does not include acceleration. That is the whole point of general relativity.

Please, please, please look at any textbook on special relativity.