Relativity Question

[between3and26characterslon]

between3and26characterslon,

 

Thanks for the link. I have read such explanations before. The sensible parts, are part of my thinking, and part of my model of the world, already.

 

That still leaves the "for no apparent reason" parts. In these parts, as in the "twins" descriptions, the "logic" stops, and the random application of terms starts. For instance, logically speaking, on the way out, both twins will see the other's clock slow, because each successive tick of the other's clock is further away and will take a longer time to reach the other's position. On the way back, the distance between the twins is closing, and both twins should see the other's clock ticking faster than their own. In both cases, each twin's clock is ticking normally, and as far as I can figure, how this ticking "appears" to the other, is not the crucial consideration, in terms of how many ticks, in their own reference frame, each twin counts. The traveling twin is traveling at .88c and it's going to take her 5.11 years worth of ticks to reach Alpha Centuri. Even if her twin gets hit by a bus, as soon as she leaves. And it will take her 5.11 years worth of her own ticks to return.

 

Lets call it "the stay at home twin dies" condition. She is still 10.22 years worth of ticks older, when she returns.

 

Relativity, has nothing to do with it. If a moving clock ticks slower, then something is slowing it down.

 

I am still not clear on why scientists don't want to look for the reason why particles whizzing through a powerful magnetic field, take longer to decay. So it happens at a rate that fits a formulae. I fail to see the logic for assuming time dilation, and don't know the real reasons. But I believe there SHOULD be an explanation. Time dilation has no meaning to me. I don't understand when and why one should consider time has slowed. In most of the cases used to describe how the world appears to different observers, it make perfect sense to me, why it appears so. I have no reason to believe there is any situation where magic needs to be involved.

 

Regards, TAR2

 

 

 

Einstein said that in Euclidian geometry a straight line is uniquely defined as being the shortest distance between two points situated upon it. By using this rule one can test whether the statement "a line is straight" is true or false. What one can not do is test the if rule is true or false. You can not ask if more than one straight line can pass between two points. You can not determine whether that is true or false, if it were a rule it would lead to different conclusions.

 

So science is based on the notion of rules, if the rules lead to consequences that agree with observation they are good rules and if they don't they are bad rules.

 

The Principle of Relativity first described by Galileo is that all frames that are at rest with each other or in uniform rectilinear translation to each other must all have laws of physics wich are no less simple than each other. In other words there is no difference between moving in a straight line at a constant speed and being stationary, if you drop a ball it falls to the ground in a predictable way in either frame. This is a rule supported by evidence, you've probably been on a plane and you know that when you drop something on a plane it falls to the floor. The plane's speed relative to the ground does not affect the laws of physics in the plane.

 

Then you have another rule of physics which is that the speed of light is constant. In every experiment conducted the speed of light in vacuo is measured to be constant. If someone on the ground shot a bullet at 1000mph and you flew past at 800mph you would measure the bullet to be travelling at 200mph. The difference is with light you will both measure it to be the same speed.

 

Einstein realised this paradox between the principle of relativity and the constant speed of light to all observers could be resolved if one were to consider that time and space were not constant. So if you are on a moving vehicle and you drop a ball you see it fall straight down but someone standing on the ground watching you go past will see your ball describe an arc as it falls to the ground. This means that although you do not have to take into account any motion when considering the physics of the frame you are in you do have to when considering the physics of a frame that is moving relative to you. You have to consider that time is dilated and length is contracted in the frame that is moving relative to you. That is its time and length change relative to yours, if you were to catch up with that frame and be at rest with it you would consider your time and length to be normal.

 

Getting back to the twins you can approximate that the distance between our sun and proxima senturi is constant. This then gives you two fixed points of an enormous frame of reference which you can consider to be at rest. Both twins start of at rest relative to this frame and only one twin gains motion relative to this frame therefore only one twin is affected by time dilation and when he/she returns is younger that their sibling.

 

Hope that makes some sense.

[tar]

Between3and26characterlon,

 

Yes it makes SOME sense.

 

I understand that I should let the universe follow the rule of E=MCsquared, since the universe is found by repeatable, peer reviewed experimentation, to always follow it.

 

Just don't know how to make sense of it.

 

By the way, Rexitivity, I'll be going along with Swansont, since I have already decided that there cannot be ANYTHING supernatural about nature. It is, what it is, and there is no magic. The trick is learning about it, and discovering its mysteries.

 

And in that light, I will wear the colors of all the humans before me and around me, that have noticed things about the world, documented them, compared notes, thrown out what does not work (the false notions) and agreed upon what does work (the truth).

 

I have noticed in my own life, that if I remember a certain thing is true, and I see it is no longer the case, I immediately discard the false thing, and accept the true thing. I believe all people do that. (Although in the area of beliefs, things are not so readily apparent.)

 

So in that light, I am saying that I believe in E=MCsquared, I just don't see how it works out to be true. I have heard about it, read about it, and thought about it, and always get to some contradiction, that just doesn't make sense to me.

 

Swansont,

 

Perhaps you can help me out with something. In the formulae I see, the relationships work out mathematically, but I rarely see the units expressed. That is Energy expressed in how many of what units, equals Mass expressed in how many of what units, times the Speed of Light in how many of what units squared? I just need one example expressed in this way, and I might see what the equation is saying about reality. I just need to see where the constants fall, and where the units of distance, time, and energy fall.

 

Regards, TAR2

[swansont]

 

Swansont,

 

Perhaps you can help me out with something. In the formulae I see, the relationships work out mathematically, but I rarely see the units expressed. That is Energy expressed in how many of what units, equals Mass expressed in how many of what units, times the Speed of Light in how many of what units squared? I just need one example expressed in this way, and I might see what the equation is saying about reality. I just need to see where the constants fall, and where the units of distance, time, and energy fall.

 

Regards, TAR2

If mass is in kilograms and c is in meters/second, the energy will be in Joules. On the atomic scale, mass is often expressed in terms of energy and c^2, e.g. a proton has a mass of about 938 MeV/c^2. (the c^2 is often implied, so one might express masses in terms of just MeV or GeV)

[tar]

Swansont,

 

Thank you very much for that. I think its the "implied" part, that I never see in the equations, and that is where the meat is. Since C is the one carrying the position and time information. Its here where things get a bit foggy to me, because I don't know what assumptions are being made, and in what frame of reference the seconds and miles are being measured and defined.

 

Time has different aspects to it, as in a piece of music. There is the rate of the beat, the spacing and how long the notes are held, and then the vibrational frequency of each single note. Since one can slow down a song, by singing the notes at their proper pitch, with a slower beat, and or hold each note longer, without changing the frequency of the note...how do you carry all the aspects properly through an equation, or transform, if you don't keep the units of position and time in there, to make sure the operation is realistically performed?

 

How do you know if you are mixing metaphors, so to speak?

 

I remember in middle school math class, a proof of something that looked logical at each step, which proved an impossible thing.

 

Closer inspection found a place where a subtle change in assumptions, produced a hidden division by zero.

 

Leaving out the units, and using an implied C, is on the one hand dangerous, in that a false assumption will not be readily noticed, and on the other hand, uninstructive, in terms of seeing the relationship between the things being considered.

 

For instance, I was thinking yesterday, that if a photon sees zero distance, and zero time in changing its position from one place in the universe to another, it has no "speed" (and perhaps there is no "other place"). So how do we use this zero speed, as the implied constant in all our equations?

 

Regards, TAR2

Edited July 9, 2011 by tar

[swansont]

Leaving out the units, and using an implied C, is on the one hand dangerous, in that a false assumption will not be readily noticed, and on the other hand, uninstructive, in terms of seeing the relationship between the things being considered.

No more dangerous than not wearing "floaties" while swimming. I'm not going to use the formalism on the chance that a novice jumps into the conversation; I expect that someone wanting to discuss such subjects has a little bit of a background. That doesn't always hold up in practice, but I think it's incumbent upon a novice to learn to swim before they jump into the deep end of the pool.

 

For instance, I was thinking yesterday, that if a photon sees zero distance, and zero time in changing its position from one place in the universe to another, it has no "speed" (and perhaps there is no "other place"). So how do we use this zero speed, as the implied constant in all our equations?

The frame of a photon is not a valid inertial frame. It's dangerous to extrapolate physics that holds in inertial frames to the frame of a photon.

[tar]

Swansont,

 

I feel safe in the deep end, without my floaties. After all, if I start to go under I can grab on to the swan swimming around out here.

 

Regards, TAR2

[swansont]

In addition we know that there in so experiment that has proved length contraction.

No, this statement is untrue. Length contraction of a macroscopic object has not been measured, but that's not the same thing as demonstrating length contraction.

[swansont]

Even if length contraction is assumed to take place, world of SR becomes quite weird. In fact to prove SR we should have an experiment in which MUTUAL time dilation is observed and this is impossible because in any such experiment we will have to bring moving clock at rest to compare results.

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No, you cannot artificially constrain experiments in this way. Mutual time dilation is ONE prediction of relativity. It is not the ONLY prediction of relativity.

 

Disturbing idea is that SR results are considered real. If the spaceship A moves with a velocity v1 and another spaceship B with v2, then their views about the universe are different and even if we take these as measurements, these are not of much use unless they really take place. Obviously, in reality, space cannot shrink differently when observers move with different speeds and in fact it cannot get shrunk at all, not only for it being empty space but also because a moving object cannot influence it. And if in reality space does not shrink, time cannot dilate.

 

The problem with "in reality" is it implies a preferred frame of reference. You need to devise a physics experiment that will tell you which frame is the preferred one.

 

In spite of the correctness of Galilean relativity and the equivalence of inertial frames and in spite of the fact about relative nature of velocity, in real world we always seek to know past acceleration. And to my mind there is deterministic value to the velocity of the object and there is a definite arrow in the direction from smaller to the bigger objects. For example we do not say that (though we see platform moving backward), the train is stationary and the earth is moving. Because smaller object cannot contain bigger object and so it is always the smaller object that is accelerated to move in the frame of bigger object.

 

This brings up the issue of the relativity of simultaneity. And the fallacy of argument by personal incredulity.

[J.C.MacSwell]

 

In spite of the correctness of Galilean relativity and the equivalence of inertial frames and in spite of the fact about relative nature of velocity, in real world we always seek to know past acceleration. And to my mind there is deterministic value to the velocity of the object and there is a definite arrow in the direction from smaller to the bigger objects. For example we do not say that (though we see platform moving backward), the train is stationary and the earth is moving. Because smaller object cannot contain bigger object and so it is always the smaller object that is accelerated to move in the frame of bigger object.

 

 

 

Tell that to the ship... as it takes off and leaves you bobbing in the ocean.

[IM Egdall]

No, this statement is untrue. Length contraction of a macroscopic object has not been measured, but that's not the same thing as demonstrating length contraction.

 

I found one example demonstrating length contraction for microscopic objects in the Science Forums archives:

 

"The people who design experiments for the accelerators have to take length contraction into acount. A spherical bunch of particles coming at you looks like a flattened ellipsoid due to relativistic shortening, and the detection probabilities and expected directions of ejecta are affected. So you could say that all these experiments are also testing length contraction, in that they are designed around it, and they work." REF: SelfAdjoint Mar 9, 2004 07:08 PM http://www.physicsforums.com/archive/index.php/t-15958.html

 

 

[Vilas Tamhane]

Tell that to the ship... as it takes off and leaves you bobbing in the ocean.

 

Even in this case, I must get ejected from the ship. Not vice-versa. Note that ship will always accelerates w.r.t. sea shore.

 

No, you cannot artificially constrain experiments in this way. Mutual time dilation is ONE prediction of relativity. It is not the ONLY prediction of relativity.

 

The problem with "in reality" is it implies a preferred frame of reference. You need to devise a physics experiment that will tell you which frame is the preferred one.

 

This brings up the issue of the relativity of simultaneity. And the fallacy of argument by personal incredulity.

 

 

Mutual time dilation and length contractions are the basic results of SR. This theory looses all its significance if these results cannot be proved, either in thought experiments or in real experiments.

 

I think when we apply relativity to actual experiments, we always observe the results ‘in reality’ in the rest frame of the lab.

 

Going back to the example of a traveler, we find that his clock will show less elapsed time than the clock in the rest frame. This is a real effect. This real effect is not possible unless for him there was ‘real’ length contraction. When we say that for the moving frame, the distance between earth and Alpha c was really contracted, it also means that distance in this direction of the whole universe was contracted. This is not possible because there can be many other objects moving with different velocities and universe cannot contract in various directions and proportions just to satisfy length contraction prediction.

 

So if length contraction is apparent then time dilation has to be apparent.

 

 

[tar]

Swansont,

 

No, you cannot artificially constrain experiments in this way. Mutual time dilation is ONE prediction of relativity. It is not the ONLY prediction of relativity.

 

Well I suggest then that we also consider where we are going to get the energy to accelerate the ship to .88 C. It might require substantial local mass to be turned into energy. And the ship itself, moving at that rate would become extremely massive, and would affect the spacetime around it, forming its own gravity well that the Sun and Alpha Centuri would begin to orbit, or fall into, and all the photons, coming toward and away from the craft would be bent by its gravity. Are these predictions of relativity built into the experiment?

 

Regards, TAR2

 

Which laws of physics are we taking with us on this thought experiment, and which are we leaving behind?

 

Seems like local spacetime would be quite permanently remodeled by this experiment. And perhaps reality would even prevent us from performing it.

[csmyth3025]

Even in this case, I must get ejected from the ship. Not vice-versa. Note that ship will always accelerates w.r.t. sea shore.

 

 

 

 

Mutual time dilation and length contractions are the basic results of SR. This theory looses all its significance if these results cannot be proved, either in thought experiments or in real experiments.

 

I think when we apply relativity to actual experiments, we always observe the results 'in reality' in the rest frame of the lab.

 

Going back to the example of a traveler, we find that his clock will show less elapsed time than the clock in the rest frame. This is a real effect. This real effect is not possible unless for him there was 'real' length contraction. When we say that for the moving frame, the distance between earth and Alpha c was really contracted, it also means that distance in this direction of the whole universe was contracted. This is not possible because there can be many other objects moving with different velocities and universe cannot contract in various directions and proportions just to satisfy length contraction prediction.

 

So if length contraction is apparent then time dilation has to be apparent.

 

 

(Bold added by me)

 

You seem to think that somewhere in the universe there is an object that has zero velocity relative to the universe. As far as I know, the whole point of special relativity is that every object in the universe is moving relative to some other object. The equations of special relativity simply provide the means for transforming measurements taken in one inertial frame of reference into the equivalent measurements taken in another inertial frame of reference that's moving relative to the first.

 

Special relativity doesn't claim that the measurements taken on object A are right or wrong or that the reflect anything other that what the observer on A measures. It only says that if measurements are taken on object A they can be mathematically adjusted according to a very specific set of equations to produce the measurements that an observer on object B that is moving relative to A will obtain.

 

What part of this doesn't seem real to you?

 

Chris

[swansont]

I found one example demonstrating length contraction for microscopic objects in the Science Forums archives:

 

"The people who design experiments for the accelerators have to take length contraction into acount. A spherical bunch of particles coming at you looks like a flattened ellipsoid due to relativistic shortening, and the detection probabilities and expected directions of ejecta are affected. So you could say that all these experiments are also testing length contraction, in that they are designed around it, and they work." REF: SelfAdjoint Mar 9, 2004 07:08 PM http://www.physicsforums.com/archive/index.php/t-15958.html

 

There's also the muon experiments, which show length contraction in the muon frame. In fact, any experiment that shows relativistic effects will have time dilation in one frame and length contraction in the other. The problem with the objection that length contraction has not been observed is that it really means "length contraction has not been observed in the lab frame" (which is wrong but as a much narrower claim it is at least not as wrong)

 

Mutual time dilation and length contractions are the basic results of SR. This theory looses all its significance if these results cannot be proved, either in thought experiments or in real experiments.

 

I think when we apply relativity to actual experiments, we always observe the results ‘in reality’ in the rest frame of the lab.

 

Going back to the example of a traveler, we find that his clock will show less elapsed time than the clock in the rest frame. This is a real effect. This real effect is not possible unless for him there was ‘real’ length contraction. When we say that for the moving frame, the distance between earth and Alpha c was really contracted, it also means that distance in this direction of the whole universe was contracted. This is not possible because there can be many other objects moving with different velocities and universe cannot contract in various directions and proportions just to satisfy length contraction prediction.

 

So if length contraction is apparent then time dilation has to be apparent.

Thought experiments prove nothing, they are (at best) predictions for real experiments to confirm or falsify. Real experiments are constrained by what you can build. I will reiterate: you cannot artificially constrain experiments to one or two tests when there are a multitude that would demonstrate confirmation. Time dilation is a prediction. Mutual time dilation is a much more specific prediction. There are many more ways to demonstrate time dilation than by showing mutual time dilation.

 

 

"This is not possible because there can be many other objects moving with different velocities and universe cannot contract in various directions and proportions just to satisfy length contraction prediction." shows a basic misunderstanding of relativity — it does not reflect what relativity predicts. As such, it's a straw man argument. Try again.

[Vilas Tamhane]

(Bold added by me)

 

You seem to think that somewhere in the universe there is an object that has zero velocity relative to the universe. As far as I know, the whole point of special relativity is that every object in the universe is moving relative to some other object. The equations of special relativity simply provide the means for transforming measurements taken in one inertial frame of reference into the equivalent measurements taken in another inertial frame of reference that's moving relative to the first.

 

Special relativity doesn't claim that the measurements taken on object A are right or wrong or that the reflect anything other that what the observer on A measures. It only says that if measurements are taken on object A they can be mathematically adjusted according to a very specific set of equations to produce the measurements that an observer on object B that is moving relative to A will obtain.

 

What part of this doesn't seem real to you?

 

Chris

 

I don’t think what you say is what is believed. Length contraction and time dilation are the real effects predicted by SR. If this was not the case then SR would have been just an ornamental theroy.

 

There's also the muon experiments, which show length contraction in the muon frame. In fact, any experiment that shows relativistic effects will have time dilation in one frame and length contraction in the other. The problem with the objection that length contraction has not been observed is that it really means "length contraction has not been observed in the lab frame" (which is wrong but as a much narrower claim it is at least not as wrong)

 

 

Thought experiments prove nothing, they are (at best) predictions for real experiments to confirm or falsify. Real experiments are constrained by what you can build. I will reiterate: you cannot artificially constrain experiments to one or two tests when there are a multitude that would demonstrate confirmation. Time dilation is a prediction. Mutual time dilation is a much more specific prediction. There are many more ways to demonstrate time dilation than by showing mutual time dilation.

 

 

"This is not possible because there can be many other objects moving with different velocities and universe cannot contract in various directions and proportions just to satisfy length contraction prediction." shows a basic misunderstanding of relativity — it does not reflect what relativity predicts. As such, it's a straw man argument. Try again.

 

Thought experiments prove logic in the theory. Even Einstein used these.

 

A theory has to be logically consistent, even before it is tested. However there cannot be any objection to its use if the experiments confirm the predictions. At the same time, if the theory is logically inconsistent then one should be sure that there is some other mechanism that is behind the experimental results.

 

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.

 

There's also the muon experiments, which show length contraction in the muon frame. In fact, any experiment that shows relativistic effects will have time dilation in one frame and length contraction in the other. The problem with the objection that length contraction has not been observed is that it really means "length contraction has not been observed in the lab frame" (which is wrong but as a much narrower claim it is at least not as wrong)

 

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.

 

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

 

 

[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.