133 replies to this topic

[swansont]

What I said does predict what relativity says. If am making any mistake then you should be able to correct it. There are only three arguments.

• When the traveler reaches Alpha c, his clock shows lesser elapsed time.
• If #1 is true then, this is possible only if the traveller travels lesser distance.
• If #2 is true then the length contraction of the universe, predicted by SR, must be true (real) effect.

Yes, yes and yes.

I think length contraction can never be proved directly. This is because time elapsed can be recorded on the clock and the clock can be compared. There is no such accumulative effect for length. Therefore what you say is true, it is wrong to ask for a proof of length contraction in a lab. You correctly said, moving clock always moves in space of other frame and though this space is contracted for the moving clock, it is not for the frame to which it belongs.

Yes, that's correct: time dilation can be accumulated and that's why it's easier — it's frequency that is affected, and you integrate to get the time, so you can more easily measure the effect by doing a longer experiment. That doesn't mean that length contraction isn't observed, just that it's harder to measure, because the effect is small.

Question is if the space does not contract how can time dilate.

No, that's not the question, because length does contract.

[imatfaal]

Vilas - I will dig out a link, but I believe that the data retrieved from relativistic collisions of large ions can only be fully explained if the ions are modelled as contracted to disc-like entities unpon collission rather than the spherical shape at rest

[Vilas Tamhane]

Vilas - I will dig out a link, but I believe that the data retrieved from relativistic collisions of large ions can only be fully explained if the ions are modelled as contracted to disc-like entities unpon collission rather than the spherical shape at rest

That won’t serve any purpose, because I am questioning SR postulate at the fundamental and theoretical level. Moreover the observation sighted by you appears to be applicable to objects, whereas length contraction is actually space contraction. (Not only the length between earth and Alpha c contracts but whole universe in this direction contracts. Is it ever possible?

If you have read my earlier post, you will find that length contraction is simply impossible.

[imatfaal]

Vilas - you misunderstand science entirely if you think that your postulate trumps experimental evidence

[swansont]

That won’t serve any purpose, because I am questioning SR postulate at the fundamental and theoretical level. Moreover the observation sighted by you appears to be applicable to objects, whereas length contraction is actually space contraction. (Not only the length between earth and Alpha c contracts but whole universe in this direction contracts. Is it ever possible?

If you have read my earlier post, you will find that length contraction is simply impossible.

Here's how the science works. The postulate, taken from Electrodynamics (already known to work) and applied to kinematics, is that c is a constant in all frames. The result is Lorentz transformations. Experiment shows that Lorentz transformations reflect the reality of the universe. If you negate the constance of c you break relativity and Electrodynamics. It means that neither GPS nor your car radio actually work.

To claim, scientifically, that length contraction is impossible means you have done a length contraction experiment and gotten a statistically conclusive null result. To which journal have you submitted the paper?

[Vilas Tamhane]

Here's how the science works. The postulate, taken from Electrodynamics (already known to work) and applied to kinematics, is that c is a constant in all frames. The result is Lorentz transformations. Experiment shows that Lorentz transformations reflect the reality of the universe. If you negate the constance of c you break relativity and Electrodynamics. It means that neither GPS nor your car radio actually work.

To claim, scientifically, that length contraction is impossible means you have done a length contraction experiment and gotten a statistically conclusive null result. To which journal have you submitted the paper?

Your post does not answer my question. Since I am not a scientist, I am least interested in knowing how science works. At the same time, I don’t see anything wrong in your description of how science works. I don’t think there can be any other way.



But science does not mean censorship, refusal to reason and enquiry and anger against inconvenient questions; as these belong to the realm of religion.



If I am not an expert to publish papers, if my knowledge is meager, does not deprive me from asking questions on free net forums. On the other hand I would like to ask you, how many papers against SR were published in top journals within last 100 years? Why most of the books on relativity shun discussions on questions similar to those I raised? What science is afraid of? Are students encouraged to criticize or they are rebuked for being blasphemous?

Not being in this field, I don’t know what is happening on the ground. But from the outside fringe, I can sense intolerance to skepticism, which experts forget, is an anathema to science?

[swansont]

Your post does not answer my question. Since I am not a scientist, I am least interested in knowing how science works. At the same time, I don’t see anything wrong in your description of how science works. I don’t think there can be any other way.



But science does not mean censorship, refusal to reason and enquiry and anger against inconvenient questions; as these belong to the realm of religion.

You have not been censored. The attitude of "I don't understand this but I think it's wrong" does not lead to inconvenient questions, they lead to faulty assertions. You can ask questions about relativity or you can question relativity, but you can't do both — if you don't understand it, you can't say it's wrong.

If I am not an expert to publish papers, if my knowledge is meager, does not deprive me from asking questions on free net forums. On the other hand I would like to ask you, how many papers against SR were published in top journals within last 100 years? Why most of the books on relativity shun discussions on questions similar to those I raised? What science is afraid of? Are students encouraged to criticize or they are rebuked for being blasphemous?

Not being in this field, I don’t know what is happening on the ground. But from the outside fringe, I can sense intolerance to skepticism, which experts forget, is an anathema to science?

Denial is not skepticism.

Exactly. If traveler’s clock shows lesser elapsed time, after reaching Alpha c, then this can be explained only if the distance, d, between earth and Alpha c contracted. This contraction has to be real because this is the distance traveler actually travelled during his journey. Now there is one important thing to be considered. Viewed from the rest frame, the distance d remained unchanged so how can it ‘really’ change for the traveler? After all this is the space that belongs to rest frame. Distance d is not merely the measurement of the traveler; it is the space of the rest frame that the traveler actually moves through.

Calling it "real" implies that there is one frame where the "correct" measurement can be made, and that is contrary to the concept. There is no preferred frame, and therefore you can't say one measurement is truth. The length is different for the traveler because c is constant. It's a straightforward consequence.

[tar]

The length is different for the traveler because c is constant. It's a straightforward consequence.

Swansont,

If all the clocks onboard are ticking consistantly slower than here, and she will always measure C to be C, and she measures it along the direction of travel of the ship, and she measures it perpendicular to the direction of travel, will she find that she is an oblate disc (so to speak?)

Regards, TAR2

[Vilas Tamhane]

You have not been censored. The attitude of "I don't understand this but I think it's wrong" does not lead to inconvenient questions, they lead to faulty assertions. You can ask questions about relativity or you can question relativity, but you can't do both — if you don't understand it, you can't say it's wrong.
Denial is not skepticism.
Calling it "real" implies that there is one frame where the "correct" measurement can be made, and that is contrary to the concept. There is no preferred frame, and therefore you can't say one measurement is truth. The length is different for the traveler because c is constant. It's a straightforward consequence.

It is safer for non expert to ask a question rather than make a statement. Yes I agree, till I get the answer I can’t say it is wrong. But If I don’t get an answer then naturally I will think that there is something wrong.

I am not getting answer to the question, ‘Does universe contract?’

In real world, in experimental world, we seek real effects. It is now an accepted convention that the measurements do not appear to be different. They are really different.

There is no ambiguity when there are three frames. Length of rod Lo in frame 1 is L1 in frame 2 and L3 in frame 3. Since no frame is a preferred frame, it is not possible to decide which measurement is real. Problem in the present case, as you already know, is that traveler has travelled in the space of rest frame. Was it contracted? To keep time dilation real, we must assume that space contraction was real. Question is how it is possible. How can there be real space contraction of the universe.

[swansont]

It is safer for non expert to ask a question rather than make a statement. Yes I agree, till I get the answer I can’t say it is wrong. But If I don’t get an answer then naturally I will think that there is something wrong.

I am not getting answer to the question, ‘Does universe contract?’

In real world, in experimental world, we seek real effects. It is now an accepted convention that the measurements do not appear to be different. They are really different.

There is no ambiguity when there are three frames. Length of rod Lo in frame 1 is L1 in frame 2 and L3 in frame 3. Since no frame is a preferred frame, it is not possible to decide which measurement is real. Problem in the present case, as you already know, is that traveler has travelled in the space of rest frame. Was it contracted? To keep time dilation real, we must assume that space contraction was real. Question is how it is possible. How can there be real space contraction of the universe.

Yes, to that observer it's really a different length. In that sense, it contracted. Anyone who did not change frames of reference would not observe contraction. In that sense, it has not contracted.

It boils down to what you mean by "real". If you mean "observable by all" then nothing is "real" because relativity shows us that each frame has its own reality. That is the paradigm that has to be used, because you do not have a preferred frame of reference. There is no objective way to say one frame is the real one.

[tar]

There is no objective way to say one frame is the real one.


Swansont,

Well perhaps there is. That is to say that we piece together what we have learned to build our model of the world.

When I see a truck 1/4 mile ahead on the highway, it looks very small. I can cover it with my thumb at arms length. I do not take this to mean that I should be able to hold the truck in my hand. Nor do I consider that covering it with my thumb, made it disappear.

Because of my knowledge of the world, having moved around in it, I have learned what is, and is not the case related to the apparent size of the truck and its "actual" size. Thus I am able to predict, that if I am going a few miles an hour faster than the truck, it will grow in size till it is big enough to actually contain a driver, which I know it must have behind the wheel. And sure enough, that happens.

When we measure the distance to a star we take into account its apparent movement against the "fixed" stars behind it, as we repeat the observation of the star 1/2 a year later from the other side of the Sun, and compare the views. We can take our knowledge of the whole situation, what we have found must be the size of the Earth, and its distance from the Sun, and the diameter of its orbit...hundreds, if not thousands or millions of observations and calculations, and observations, that "force" things to "have to be" the case for everything to fit together.

Thus, although there is no "preferred" frame of reference, if we take all the things we know "must" be the case and put them together, checking our findings and beliefs, from various hypothetical and/or real other frames of reference (thought, or actual "experiments") we can "build" a prediction, of "what is real" and actually the case.

Contradictions that arise, are not the fault of objective reality (which MUST be the case), but a sign that our model needs some adjustment, or that we are not looking at it the right way.

Thus, for various reasons, I would say "our" frame of reference, is not only a good one to use, but the only one we have, to use. And transformations and differential geometry and the mass=energy equivilancy, are excellent ways to "move around" in an existant universe, that fits together flawlessly.

Still, an "objective reality" that fits together flawlessly has to be the case. We experience it every day. Objectively speaking, the universe we experience IS the real one. (its the only one we have)

Regards, TAR2

[swansont]

Objectively speaking, the universe we experience IS the real one. (its the only one we have)

And what of someone living in a different frame of reference?

[J.C.MacSwell]

Frames generally speaking* do not have their own independent reality. We may shift around mathematically in the definitions of each, in both time and space...but we still exist...we are still "here" in the past, present or future of whichever frame you choose. (assuming the frame is physically legitimate)

They are all real in that sense.

*you can define a frame to exclude us, but in that sense the frame is just limited not our reality

Edited by J.C.MacSwell, 16 July 2011 - 03:27 PM.

[Janus]

How can there be real space contraction of the universe.[/font][/size]

The problem with that question is that it is a lot like the question, " If the world is round, how come the people on the underside don't fall off?" in that it is based on a presumption. The presumption of the quoted question deals with the nature of "down". The presumption of your question deals with the nature of time and space (and how its measured).


Now I'll explain what I mean.

Imagine that you have a point "a" located at a position with respect to the origin of a reference frame like this:



We have two axes, x and y. If you draw a line perpendicular to the x axis, it intersects with the x axis at xa which gives the distance of a from the origin in terms of x. a similar line drawn perpendicular to the y axis gives the distance of a from the origin in terms of y.

Okay. Now we superimpose a new reference frame on top the first with the same origin but tilted at 45 degrees. The axes are labeled x' and y' we draw lines perpendicular to the axes and intersecting with point "a" like we did before.



If we now rotate this whole image by 45 degree, we can more easily see how this new frame measures the position of with respect to the origin.



Note that if you were to draw a line between "a" and the origin, it would be the same length as it was in the first diagram, what has changed is the distance in terms from the axes.

To relate this to relativity we change the y and y' axes to t and t', the 45 degree tilt corresponds to the second frame of reference moving with a velocity with respect to the first, and the x axis is the distance as measured along the line of motion.

"a" and the origin represent events that occur at certain times. ta and t'a is the time difference between the event at the origin and the event marked a.

shown here are the measurement of "a" with respect to the axes according to both frames:






The time difference and the distance along the line of movement between the origin event and event a is different for the two frames. This corresponds to time dilation, length contraction, and the relativity of simultaneity). Again, the line joining the origin and "a" remains constant. This is known as the space-time interval. What changes between frames is the time and space components of the space-time interval.

These diagrams are for getting the general concept across and aren't proper space-time diagrams, so their utility is somewhat limited.

The point to all this is that any measurement you make is frame dependent and that measurement represents "reality" for that frame and that's all the reality that there is.

So from a reference frame moving with "with respect to the local region of the universe" ( I'll will not say moving with respect to the whole universe, because that actually has no meaning), the local universe does "really' contract. And from a reference frame moving at a different velocity, it will "really" contract differently and there is no contradiction in this.

It just comes down to thinking about time and space differently, just like accepting a round Earth required people to think differently about what "down" meant.

[Vilas Tamhane]

The problem with that question is that it is a lot like the question, " If the world is round, how come the people on the underside don't fall off?" in that it is based on a presumption. The presumption of the quoted question deals with the nature of "down". The presumption of your question deals with the nature of time and space (and how its measured).


Now I'll explain what I mean.

Imagine that you have a point "a" located at a position with respect to the origin of a reference frame like this:



We have two axes, x and y. If you draw a line perpendicular to the x axis, it intersects with the x axis at xa which gives the distance of a from the origin in terms of x. a similar line drawn perpendicular to the y axis gives the distance of a from the origin in terms of y.

Okay. Now we superimpose a new reference frame on top the first with the same origin but tilted at 45 degrees. The axes are labeled x' and y' we draw lines perpendicular to the axes and intersecting with point "a" like we did before.



If we now rotate this whole image by 45 degree, we can more easily see how this new frame measures the position of with respect to the origin.



Note that if you were to draw a line between "a" and the origin, it would be the same length as it was in the first diagram, what has changed is the distance in terms from the axes.

To relate this to relativity we change the y and y' axes to t and t', the 45 degree tilt corresponds to the second frame of reference moving with a velocity with respect to the first, and the x axis is the distance as measured along the line of motion.

"a" and the origin represent events that occur at certain times. ta and t'a is the time difference between the event at the origin and the event marked a.

shown here are the measurement of "a" with respect to the axes according to both frames:






The time difference and the distance along the line of movement between the origin event and event a is different for the two frames. This corresponds to time dilation, length contraction, and the relativity of simultaneity). Again, the line joining the origin and "a" remains constant. This is known as the space-time interval. What changes between frames is the time and space components of the space-time interval.

These diagrams are for getting the general concept across and aren't proper space-time diagrams, so their utility is somewhat limited.

The point to all this is that any measurement you make is frame dependent and that measurement represents "reality" for that frame and that's all the reality that there is.

So from a reference frame moving with "with respect to the local region of the universe" ( I'll will not say moving with respect to the whole universe, because that actually has no meaning), the local universe does "really' contract. And from a reference frame moving at a different velocity, it will "really" contract differently and there is no contradiction in this.

It just comes down to thinking about time and space differently, just like accepting a round Earth required people to think differently about what "down" meant.

Your explanation is as good as any can be. But I differ with your definition of reality. Any physical entity in the vector form is the reality which can never change by our selection of system of coordinates. Only components can change. This is not the case with space time diagram because of the addition of time as a coordinate. However existence of a vector is a physical reality and any coordinate system that changes this basic reality is necessarily wrong.

There cannot be any theory and associated mathematics based on coordinate system alone that has an ability to change basic quantities of nature. Any such theory, according to me, is grossly wrong.

In case we decide that reality depends on frame then we face many problems.

1. Length contraction is space contraction and we do not have any proof that space is some tangible entity which has capability of any dimensional change. Therefore the statement that space can contract is not good physics. If space can contract then it should be able to expand. What exactly this means?

2. For the traveller, the space contracts but at the same time the same space does not change for the observer in the rest frame. How can same space ‘really’ contract and remain unchanged at the same time?

3. For a rapidly moving train observer, wheels of moving cycle are elliptical (or rather every particle on the wheel moves in elliptical path. And this is not an apparent measurement but ‘real’ change. This is not possible.

4. There is nothing in physics that explains how any moving object can have influence on non moving objects. Is it ever possible that the wheels of a bicycle will become really oblong if I pass along it with greater speed in a car? The measurement is clearly apparent and not real. In the previous example, it is impossible that the distance between earth and Alpha c will ‘really’ contract. Any such measurement has to be apparent and if this is so then, in spite of the measurements of the traveller, he will have to travel the real distance that is measured in the rest frame.

[swansont]

Your explanation is as good as any can be. But I differ with your definition of reality. Any physical entity in the vector form is the reality which can never change by our selection of system of coordinates. Only components can change. This is not the case with space time diagram because of the addition of time as a coordinate. However existence of a vector is a physical reality and any coordinate system that changes this basic reality is necessarily wrong.

There cannot be any theory and associated mathematics based on coordinate system alone that has an ability to change basic quantities of nature. Any such theory, according to me, is grossly wrong.

In case we decide that reality depends on frame then we face many problems.

1. Length contraction is space contraction and we do not have any proof that space is some tangible entity which has capability of any dimensional change. Therefore the statement that space can contract is not good physics. If space can contract then it should be able to expand. What exactly this means?

Who is claiming that space is a tangible entity?

2. For the traveller, the space contracts but at the same time the same space does not change for the observer in the rest frame. How can same space ‘really’ contract and remain unchanged at the same time?

3. For a rapidly moving train observer, wheels of moving cycle are elliptical (or rather every particle on the wheel moves in elliptical path. And this is not an apparent measurement but ‘real’ change. This is not possible.

4. There is nothing in physics that explains how any moving object can have influence on non moving objects. Is it ever possible that the wheels of a bicycle will become really oblong if I pass along it with greater speed in a car? The measurement is clearly apparent and not real. In the previous example, it is impossible that the distance between earth and Alpha c will ‘really’ contract. Any such measurement has to be apparent and if this is so then, in spite of the measurements of the traveller, he will have to travel the real distance that is measured in the rest frame.

Repeating your statements does not make them any truer. If there is an objective true length, there must be a frame in which that length is measured. How do you tell if you are in that frame? You appear to be insisting that Galilean transforms are how nature behaves. Is there any physical evidence you can produce to confirm this? That it offends your sensibilities does not count.

[tar]

And what of someone living in a different frame of reference?

Swansont,

They see "our" universe, from their perspective. But once we meet them, they can make the transformation to our frame and we to theirs, and there will still be one objective universe that both we and the newly met "other framer" can and do consider "our" universe.

Regards, TAR2

The point to all this is that any measurement you make is frame dependent and that measurement represents "reality" for that frame and that's all the reality that there is.

Janus,

But included in that frame's reality is the ability to make the transformations to our reality, and any particle, field, object or motion, that exists in both frames can be "seen" in the other's frame, if the transformations are made.

If the imaginary frame does not account for everything that is "real" in the starting frame, if transformation into the imaginary frame and back, yields an impossible thing, then, as Vilas is arguing, the transformation was not done in a realistic way.

And the universe need not conform to our analogies. Our analogies are of it. And I for one, will challenge the completeness of our analogies, before I challenge the truth of the universe.

Regards, TAR2

[swansont]

Swansont,

They see "our" universe, from their perspective. But once we meet them, they can make the transformation to our frame and we to theirs, and there will still be one objective universe that both we and the newly met "other framer" can and do consider "our" universe.

Regards, TAR2

Why don't we have to consider it from theirs? Is there a physics-based reason that ours is preferred?

[tar]

Swansont,

We have to consider it from one place and time, inorder to have a frame to transform into another.

This starting frame is required, and the basis upon which we define any other.

Once we have defined the other, we can mentally exist there, put ourselves in its shoes, and even then consider IT the "starting" frame, and our frame "an other frame".

But I prefer our frame, because it is the one we have been experiencing the world and the universe from through our long history of experiments and theoretical exploration. It is the frame we have learned about, and the frame we understand the best.

Regards, TAR2

[J.C.MacSwell]

Swansont,

We have to consider it from one place and time, inorder to have a frame to transform into another.

This starting frame is required, and the basis upon which we define any other.

Once we have defined the other, we can mentally exist there, put ourselves in its shoes, and even then consider IT the "starting" frame, and our frame "an other frame".

But I prefer our frame, because it is the one we have been experiencing the world and the universe from through our long history of experiments and theoretical exploration. It is the frame we have learned about, and the frame we understand the best.

Regards, TAR2

Which frame would that be? I personally use a number of them everyday and would find it very inconvenient not to switch.