LSU professor resolves Einstein's twin paradox




First suggested by Albert Einstein more than 100 years ago, the paradox deals with the effects of time in the context of travel at near the speed of light. Einstein originally used the example of two clocks - one motionless, one in transit. He stated that, due to the laws of physics, clocks being transported near the speed of light would move more slowly than clocks that remained stationary. In more recent times, the paradox has been described using the analogy of twins. If one twin is placed on a space shuttle and travels near the speed of light while the remaining twin remains earthbound, the unmoved twin would have aged dramatically compared to his interstellar sibling, according to the paradox.


"If the twin aboard the spaceship went to the nearest star, which is 4.45 light years away at 86 percent of the speed of light, when he returned, he would have aged 5 years. But the earthbound twin would have aged more than 10 years!" said Kak.

The fact that time slows down on moving objects has been documented and verified over the years through repeated experimentation. But, in the previous scenario, the paradox is that the earthbound twin is the one who would be considered to be in motion - in relation to the sibling - and therefore should be the one aging more slowly. Einstein and other scientists have attempted to resolve this problem before, but none of the formulas they presented proved satisfactory.


Kak's findings were published online in the International Journal of Theoretical Science, and will appear in the upcoming print version of the publication. "I solved the paradox by incorporating a new principle within the relativity framework that defines motion not in relation to individual objects, such as the two twins with respect to each other, but in relation to distant stars," said Kak. Using probabilistic relationships, Kak's solution assumes that the universe has the same general properties no matter where one might be within it.

The implications of this resolution will be widespread, generally enhancing the scientific community's comprehension of relativity. It may eventually even have some impact on quantum communications and computers, potentially making it possible to design more efficient and reliable communication systems for space applications.

For more information, please contact Subhash Kak at 225-578-5552 or kak@ece.lsu.edu .

Louisiana State University

http://www.brightsurf.com/news/headlines/28890/LSU_professor_resolves_Einsteins_twin_paradox.html

I'm sure Mr. Kak did something interesting, but there never has been a paradox to solve. maybe he will make peopl more comfortable about the so-called paradox, but he hasn't solved anything that hasn't been solved before.

Cincirob: I'm sure Mr. Kak did something interesting, but there never has been a paradox to solve. maybe he will make people more comfortable about the so-called paradox, but he hasn't solved anything that hasn't been solved before.



AAF: ' Mr. Kak' was trying to solve the Dingle Paradox by assuming and resurrecting the very antithesis of Einstein's Special Relativity; i.e. the privileged frame of reference. Is that interesting, or what?



Ted: Here is the answer: http://www.mathpages.com/home/kmath317/kmath317.htm Doubtful that you even understand the question



Bob S: Yah, right! We are supposed to believe a Relativist who can't even spell Relativists right (relativityists, his word) is going to be objective with his comments about Dingle...I don't! The only mistake Dingle made was tactical, he assumed (falsely, still!) that the "relativityists" sic would respond to his concerns with reasoned discourse and not ad hominem attacks as was the case. Dingle may have gone to his grave with spit on his collar but his integrity was intact and, he was RIGHT! And by the way Tedbecile, if you don't think AAF understood the question why not restate it for him, the original question, DumbASS!



AAF: Right on target, Bob! This Idiot Ted would never understand the Dingle's Paradox, because Imbecile Ted does not want to see the truth. It's that simple.



Cincirob: Hey Ted, aren't you glad you don't have to use Dingle as a reference for your arguments....he's the bottom of the scientific barrel.



AAF: Look, Cinci; your 'he's the bottom of the scientific barrel' (whatsoever that means) would not help you or make you able to solve Dingle's most devastating paradox. Very briefly, Dingle's Paradox has killed Einstein's Special Relativity; and you have to live or to try to live with this fact.

AAF: Look, Cinci; your 'he's the bottom of the scientific barrel' (whatsoever that means) would not help you or make you able to solve Dingle's most devastating paradox. Very briefly, Dingle's Paradox has killed Einstein's Special Relativity; and you have to live or to try to live with this fact.


cinci: You can't talk the theory away AAF. But if you'd like to try, then you describe "Dingle's devastating paradox" here.

No excuses and no cutesy comebacks, just explain it in your own words.

If you can't explain the "devastating paradox" in your own words here then we'll know it's all just hot air.
*****************************

SR deals with symmetric case of twins, so that each observe time dilation of the other. i.e. SR assumes symmetry.

When relativity theory is stepped up to GR the assumption of symmetry is abandoned and its allowed to be asymmetric i.e. first twin sees the other age faster, and the second twin sees the other ageing slower.

Kak seems to be dealing with that.

Kak-- "I solved the paradox by incorporating a new principle within the relativity framework that defines motion not in relation to individual objects, such as the two twins with respect to each other, but in relation to distant stars,"

i.e. he's talking about Mach's principle, and a preferred frame of reference.

That means SR assumption of symmetric observation and no preferred frame of reference is false. (its an assumption that is stated in SR but not often stated explicitly enough in SR texts. )i.e. SR is dead.

But Einstein's relativity is still alive - because GR assumptions replace his SR assumptions.

none: SR deals with symmetric case of twins, so that each observe time dilation of the other. i.e. SR assumes symmetry.

When relativity theory is stepped up to GR the assumption of symmetry is abandoned and its allowed to be asymmetric i.e. first twin sees the other age faster, and the second twin sees the other ageing slower.

Kak seems to be dealing with that.

Kak-- "I solved the paradox by incorporating a new principle within the relativity framework that defines motion not in relation to individual objects, such as the two twins with respect to each other, but in relation to distant stars,"

i.e. he's talking about Mach's principle, and a preferred frame of reference.

That means SR assumption of symmetric observation and no preferred frame of reference is false. (its an assumption that is stated in SR but not often stated explicitly enough in SR texts. )i.e. SR is dead.

But Einstein's relativity is still alive - because GR assumptions replace his SR assumptions.


cinci: GR and SR are not incompatible nor do they conflict. And while SR is symmetric, what happens in the twin paradox is not. Proper application of the Lorentz transformations to each twin in turn yields consistent results.
***********************

cinci: And while SR is symmetric, what happens in the twin paradox is not. Proper application of the Lorentz transformations

proper application of Lorentz transformations and its symmetric. And since GR says its not symmetric, SR is wrong.

None,

You mix truth and mistakes here:

When relativity theory is stepped up to GR the assumption of symmetry is abandoned and its allowed to be asymmetric i.e. first twin sees the other age faster, and the second twin sees the other ageing slower. ... That means SR assumption of symmetric observation and no preferred frame of reference is false.

First of all, in the twin setup, there is no symmetry between the twins.
One twin will reverse his travel to meet his brother.
Therefore this twin will experience accelerations and decelerations, while the other will not.
Also this twin will not always be in an inertial frame, while the other is supposed to stay inertial.
No symmetry for the twins and therefore, no paradox.

But the nice aspect of the "paradox", is precisely its relation to general relativity.
Indeed acceleration creates this assymetry between the twins.
Indeed, gravitational fields should have the same effect.
And therefore indeed there is no symmetry in GR as long as there is either some acceleration, or some gravitational field.

First of all, in the twin setup, there is no symmetry between the twins.
One twin will reverse his travel to meet his brother.
.
You are an idiot mixing up SR and GR.
.
Reversing travel is acceleration and SR is not considering acceleration.
.
The symmetry is when there is constant velocity.

SR is valid locally anywhere in GR.
So what is your point?

none:

First of all, in the twin setup, there is no symmetry between the twins.
One twin will reverse his travel to meet his brother.
.
You are an idiot mixing up SR and GR.
.
Reversing travel is acceleration and SR is not considering acceleration.
.


Ted: none, the idiot is you. SR deal with acceleration just fine, Here is the SR explanation to what happens to the travelling (accelerated) twin. http://en.wikipedia.org/wiki/Twin_paradox#Difference_in_elapsed_time_as_a_result_of_differences_in_twins.27_spacetime_pathsSo, STFU.

Oh yes, that's another good one, none:

... SR is not considering acceleration ... (none)

Have you ever read about the equation of motion in SR?
Would you mean that in SR, ther is only uniform motion?
Think twice!

Ted: none, the idiot is you. SR deal with acceleration just fine,

No TEd YOU GOT IT WRONG AGAIN YOU ****ING WANKER GO AND WANK OFF SOMEWHERE ELSE YOU **** FACE

... SR is not considering acceleration ... (none)

Have you ever read about the equation of motion in SR?

. Onbiously you haven't because it does not deal with acceleration. Ted's a wanker, but you are an idoit. Do us all a favour shoot your one brain cell out

none,

Can you be more precise that a few insults?
What do you mean by "it (special relativity) does not deal with acceleration"?
Have you ever heard about particle accelerators and how special relativity is needed to control the beam trajectories correctly.
I worked for several years in a closely related domain.
What are your own credentials?

None, just FYI.
This is the definition of the acceleration in special relativity:



where



is the velocity.
The derivatives are with respect to the proper time.

What do you mean by "it (special relativity) does not deal with acceleration"?
That's really a ambiguous statement.

none: Have you ever read about the equation of motion in SR?

Obviously you haven't because it does not deal with acceleration.

cinci: Well nobody hands you this one on a platter, but special relativity can deal with acceleration. Here's the equation:

t' = Int[t(1 - (v(t)/c)^2)^.5] from t=0 to t=t

where "Int" stands for the integral symbol and

v(t) is the time history of velocity in the period t=0 to t=t and is, in general, a function of acceleration.

For instance, for constant acceleration where v=0 at t=0, v(t) = at

where "a" is the value of constant acceleration.

This integral will give you and equation for constant acceleration, but since that is only one of an infinite number of acceleration histories you could dream up, there's no single equation.
*********************************

The Principle of Special Relativity is -
"The laws of physics are the same in any inertial frame, regardless of position or velocity".


Nothing about acceleration!!

lala: What do you mean by "it (special relativity) does not deal with acceleration"?
That's really a ambiguous statement.

. As pointed out no acceleration mentioned in SR principle, lala to you

cinci: Well nobody hands you this one on a platter, but special relativity can deal with acceleration.
.
Nuts to you too, the Principle of SR says nothing about acceleration. So you are modifying SR.

cinci: And while SR is symmetric, what happens in the twin paradox is not. Proper application of the Lorentz transformations

none: proper application of Lorentz transformations and its symmetric. And since GR says its not symmetric, SR is wrong.


cinci: Easy enough to prove. If you think SR produces a paradox when the Lorentz transformations are properly applied, then why don't you apply them to the problem and prove it?
***************************

cinci: Well nobody hands you this one on a platter, but special relativity can deal with acceleration.


none: Nuts to you too, the Principle of SR says nothing about acceleration. So you are modifying SR.


cinci: If you don't understand what I posted, ask questions. If you don't want to believe me, then google acceleration and relativity.
******************************

none,

How can you derive this stupidity:

it (special relativity) does not deal with acceleration

from the principle of relativity:

The Principle of Special Relativity is - "The laws of physics are the same in any inertial frame, regardless of position or velocity". Nothing about acceleration!! (this last sentense by none, of course)

Do you really mean that the "laws of physics" do not deal with acceleration ???

The Principle of Special Relativity is -

"The laws of physics are the same in any inertial frame, regardless of position or velocity".

Nothing about acceleration!!

lalbatros>>Do you really mean that the "laws of physics" do not deal with acceleration ???
,
Special relativity does not properly deal with acceleration; you are just some kind of nut that does not understand English.

none,

You seem incompetent at anything else than name calling.
Otherwise you would be able to explain your statement better:

"The laws of physics are the same in any inertial frame, regardless of position or velocity".

How can you conclude from this statement that "SR does not deal with acceleration"?
The statement refers clearly to the "laws of physics".
Do you really think that the laws of physics do not deal with acceleration?

I don't say that SR applies perfectly well without limitations.
All theories have limitations.
Read a little bit more about the motivations of GR and you will understand why GR is a generalisation of SR, in case that was not obvious for you.

Also from a practical point of view, your statement "SR does not deal with acceleration" is a total absurdity.
As I told you (and you gave no answer), particles acelerators deal with acceleration and need the use of special theory of relativity for proper design and operation. So your statement can only be flawed as it appears from -I would say- engineering practice!

"The laws of physics are the same in any inertial frame, regardless of position or velocity".

Anonymous idiot>How can you conclude from this statement that "SR does not deal with acceleration"?
.
How can you not?
.
There is no mention of word acceleration.

Indeed, the word "acceleration" does not appear explicitely.
Do you know one of the earliest and best known laws of physics?
It is the Newton's law: F=ma where a stand for acceleration.

Newton's law has been improved in the Special theory of Relativity.
Didn't you know?
The improved law differs only slightly from Newton.
Roughly speaking absolute time has been replaced by proper time when taking derivatives.
And you would pretend that "SR does not deal with acceleration"?

Do you need further help to understand why it is really silly to say that "SR does not deal with acceleration"?

Anonymous >>Indeed, the word "acceleration" does not appear explicitely.
.
Yes

Anonymous idiot>Do you know one of the earliest and best known laws of physics? It is the Newton's law: F=ma where a stand for acceleration.
.
So what, Einstein changes all that. Special relativity does not say how to handle force. And then Einstein speculates that force is spacetime curvature creating a different theory - general relativity. So your idiocy is not being able to understand relativity.

none,

It seems that you cannot learn anything by yourself.
Just read about the history of SR and its motivation.
It was all about reconciling the Maxwell's theory of electromagnetism and the Newton's law.

The experimental facts were such that the Newton's law had to be modified.
The modification was small in typewriting but huge in concepts.
It was just replacing "absolute time" by "proper time" in time derivatives (roughly speaking, specially for you).

If you had learned just a tiny bit of special relativity you would know that for velocities much smaller than the speed of light, the Einstein's law of motion is exactly the same as the Newton's law of motion. However, it is also well known, even by the laymen, that at high speeds, objects get "more inertia" in such a way that they can never accelerate up to the speed of light.

And you would still pretend that "SR does not deal with acceleration" !!!
And you went even deeper in absurdity with this one:

Special relativity does not say how to handle force.

Not only is that in contradiction with the main goals and results of SR, but it is -as I explained several time- in contradiction with the daily practice in particle accelerators engineering and many other fields of physics where charged particles are accelerated by electromagnetic fields, like plasma physics. Just have a look -for example- at the theory of Bremsstrahlung that deals with collisions of charged particles. (collisions involves acceleration or deceleration by impact)

The modifications to the laws of motion by Einstein's theory of SR are simply crucial for a huge part of modern physics, specially in laboratory experiments. That part of relativity that deals with motion is called relativistic mechanics. Maybe you can have a read about it: http://www.britannica.com/EBchecked/topic/496896/relativistic-mechanics , just in case you would doubt that it exists.

You could also have a look at the first paper of A. Einstein on what is today called Special Relativity: ON THE ELECTRODYNAMICS OF MOVING BODIES . You will see that the last §10 precisely deals with motion, forces and acdeleration, using notations and terminology of that time. No surprise: electrodynamics is about electromagnetic fields as well as about the motion of charges particles. That is why it contains the word "dynamics".

You could also read this other famous paper: DOES THE INERTIA OF A BODY DEPEND UPON ITS ENERGY-CONTENT?.
You should know that from Newton's law, and by definition inertia is related to force and acceleration (since F=ma). Therefore, if Einstein's special theory of relativity has a relation to inetia, then it should have a relation to "acceleration".

It is very tyring to try to explain you something.

Re: anonymous, LSU professor resolves Einstein's twin Paradox February 10 2009, 8:09 AM

Anonymous,
"If you had learned just a tiny bit of special relativity you would know that for velocities much smaller than the speed of light, the Einstein's law of motion is exactly the same as the Newton's law of motion. However, it is also well known, even by the laymen, that at high speeds, objects get "more inertia" in such a way that they can never accelerate up to the speed of light."

At what given velocity do Newton's laws cease (stop-quit-end) and Relativistic effects take over. For example, a particle starts at 0>...c under Newton's laws and ends at (c) under Relativistic effects, there has to be a cross-over point of velocity where Newton's laws end; what is that given velocity?

And second, the parameters of Special Relativity are "in vacuum", there is no gravity in SR----remember----the invariable speed of light "in vacuum"; therefor, no gravity = no inertia!

Anonymous idiot, you really are a big idiot, if you attended any physics/ astronomy courses, you must have slept through them.



from: Astronomy 162
Stars, Galaxies, and
Cosmology
In our first semester of astronomy we were concerned primarily with our own Solar System. In this semester we broaden our perspective and consider the entire Universe.

quote: Einstein's Special Theory of Relativity is valid for systems that are not accelerating. Since from Newton's second law an acceleration implies a force, special relativity is valid only when no forces act.

bob s
Re: LSU professor resolves Einstein's twin paradox February 10 2009, 8:50 AM

Re: anonymous,


Anonymous is just trying to misrepresent relativity.

Special relativity is supposed to deal with constant velocity motion. When there is acceleration and force, you are supposed to deal with General relativity.

Anonymous is just distorting things. Special relativity can't properly handle acceleration.

There are equations in Special relativity for acceleration and force, but the theory can't properly handle it; its only an approximation.

He's just someone who can't properly understand relativity and talks nonsense.

Good none!

It helps a lot to give the full reference to a quote.
That's good practice!
I can now see the context of the sentense.
However, it is very clear that generally speaking this sentense is simply wrong:

Einstein's Special Theory of Relativity is valid for systems that are not accelerating ...

Remember also that there is a part of SR which is called "relativistic mechanics".
Furthermore I gave you many examples where SR is actually dealing with acceleration and forces.
And not only SR is dealing with acceleration and forces but it does it very successfully.

So what is the problem then?
It is mainly that the reference you gave (http://csep10.phys.utk.edu/astr162/lect/cosmology/gravity.html) is an oversimplified introduction to physics.
The problem is more subtle than "having a problem with acceleration".
Read a better reference like this one: The Classical Theory of Fields.

Anonymous

However, it is very clear that generally speaking this sentense is simply wrong:

Einstein's Special Theory of Relativity is valid for systems that are not accelerating ...

... You are just deluded.

Anonymous
So what is the problem then?

...No problem with me, its your end.

Anonymous
It is mainly that the reference you gave (http://csep10.phys.utk.edu/astr162/lect/cosmology/gravity.html) is an oversimplified introduction to physics.
..Rubbish. Its your statements that are oversimplified.

Anonymous
The problem is more subtle than "having a problem with acceleration".
Read a better reference like this one: The Classical Theory of Fields.
... If that text says differently then its probably wrong. Better reference indeed; you do talk so much nonsense; if its wrong then its a worse reference; it might even be some nonsense you wrote (?)

Anonymous idiot

I checked out the link you gave; its to some book that is the fourth revised edition. It can't even get its facts right and has revised itself four times already; what nonsense; presumely needs more revising.

It is up to up, none.
If you believe by L D Landau & E.M. Lif****z is scrap, then good luck.
Just a last help for you: a book that has been revised is a book that has been read many times.
You should look also at the date of the first edition, as well as the number of languages it was translated to.

Anonymous

If you believe by L D Landau & E.M. Lif****z is scrap, then good luck.
Just a last help for you: a book that has been revised is a book that has been read many times.
.....
So what are you trying to tell me; that Special relativity is being continually revised (?) Well that would be nonsense. It would mean that person A working from the old version and person B working from the revised version would each be calling one another idiots. What idiot thought of doing that?

none: Anonymous is just trying to misrepresent relativity.

Special relativity is supposed to deal with constant velocity motion. When there is acceleration and force, you are supposed to deal with General relativity.

Anonymous is just distorting things. Special relativity can't properly handle acceleration.

There are equations in Special relativity for acceleration and force, but the theory can't properly handle it; its only an approximation.

He's just someone who can't properly understand relativity and talks nonsense.


cinci: You seem determined to avoid learning anything new. The theory of relativity was developed for inertial frames, that is, no acceleration or gravity. I showed earlier that it can be used to predict time dilation during acceleration by the use of calculus. Hereis why that works.

Let's say you have an accelerating clock and you plot the velocity of the clock over time. Let's say that over a one second period, the velocity changed linearly from 1 ft.sec to 10 ft/sec. Now look at it over a period of .5 seconds and it changed only 5 ft/sec. Over a .01 second period it changes only .1 ft/sec. And finally, over an infintessimaly small fraction of a second, the velocity changes and infintessimally small amount. So, during that samll fraction of time, the velocity doesn't change much so relativity is a pretty good estimate of what happens in that time period.

Then, if you add up al the little effects for all the little pieces of time, then you get the total effect. You can do this numerically; that is, really plot a time history of velocity, break up the history into little chunks, evaluate each, and then add them up. This would be an approximate answer as you suggest.

But calculus (invented by Newton for exactly this type of problem) allows you to let the little chunks become arbitrarily small. In fact that in the limit they approach zero and this will give you and exact answer. So you are correct that SR is a constant velocity but Newton provided us witha method for treating this kind of probem and getting an exact anwser.

none,

You are really excellent at playing the fool:

So what are you trying to tell me; that Special relativity is being continually revised (?) Well that would be nonsense. It would mean that person A working from the old version and person B working from the revised version would each be calling one another idiots. What idiot thought of doing that?

Maybe you can continue your show further after reading that:

The Classical Theory of Fields Revision Project (CTFRP)

Have fun!

Anonymous
Maybe you can continue your show further after reading that:
The Classical Theory of Fields Revision Project (CTFRP)
....
That article says".it has been realised over the years that The Classical Theory of Fields contains a number of serious theoretical errors.
The errors are in general not peculiar to this book alone, but
are fundamental misconceptions that appear routinely in all
textbooks on General Relativity, without exception."

Is it just peculiar to that book (with its revisions) or do others accept relativity is full of errors?

none: Is it just peculiar to that book (with its revisions) or do others accept relativity is full of errors?


cinci: Maybe there aren't any errors and it's just that people read as poorly as you apparently do. The articel doesn't say there are any errors in the theory of relativity.
***************************

none: Is it just peculiar to that book (with its revisions) or do others accept relativity is full of errors?
cinci: The articel doesn't say there are any errors in the theory of relativity.
...
You must have a reading difficulty, it says: The errors are in general not peculiar to this book alone, but are fundamental misconceptions that appear routinely in all extbooks on General Relativity, without exception."

none,

The Landau's book "Classical theory of fields" is one of top books of physics with a few others from Feynman, Wheeler, Jackson, Fermin, Dirac, ...
It has been revised just as many times it has been reprinted (and in several languages).
It is normal practice to remove at least small mistakes for each edition.
Improvement is both a sign of respect and a sign of quality.

The approach taken by Landau is more than a standard textbook approach.
The intention of Landau was not to paraphrase Einstein or others, or to simplify.
The approach has been to show the deep principles behind the classical field theory.

He systematically explores how a principle of least action can be designed to describe the motion of particles or the evolution of the electromagnetic fields, or the evolution of the metric.
What I have learned from this book is that there is very little freedom to build an invariant theory in each case.
Classical electrodynamics is the best example for our discussion, in the first half of his book. This approach is extended in other volumes about quantum field theory.

But what is so special with Special Relativity?
My answer is: mathematics is not enough for special relativity, you first need to understand.
I strongly recommend another book that stresses the fundamentals.
It is: Very Special Relativity: An Illustrated Guide by Sander Bais.
You will find only few equations but you will get it right.

The chapter 6 might help you understand that SR is also good at mechanics (and therefore acceleration).
Here is an extract from the beginning of chapter 6:

In Newtonian mechanics the state of motion of a particle is characterised by its mass m and its velocity v or momentum p=mv. Newton came to the insight that a force cause a proportional acceleration a, where the proportionality constant is by definition the inertial mass m. His famous force law F=ma basically states that force equals the change in momentum (per unit time). ...

From there on, the author exposes the differences between relativist mechanics and Newtonian mechanics.
The most famous difference is of course the constant E=mc˛ that appears in the energy conservation law.
Talking "energy conservation" is talking mechanics, and talking mechanics is talking force and acceleration. Just to illustrate once more ...

In chapter 8, this book brings you "Beyond special relativity" and you will find there a nice comment about the horizon of an uniformly accelerated observer.
May be you might be more interrested by this small book than by this childish discussion.

Anonymous




ok Anonymous you fooled me, you wasted my time researching what you were stating; great laugh.

I couldn't check Landau's book "Classical theory of fields".

But I found a course based on that book being an advanced level additional reading at:http://theory.gsi.de/~friman/gtr.html

Introduction to the General Theory of Relativity
WS 2007-2008 by Bengt Friman

The Literature it cites:

More advanced:

S. Weinberg, Gravitation and Cosmology, Wiley, 1973

L.D. Landau, E.M. Lif****z, The Classical Theory of Fields, Pergamon, 1983

On lecture 3 it deals with SR applied to Twin paradox, and says you need GR because acceleration involved.

You probably want the whole thing, so Quote:

Twin paradox
Consider a clock moving along an arbitrary world line, with accelerations. The
time measured from space-time point a to b by the clock (the proper time) is
[equation won't come out!](47)
Now consider two clocks, one remaining at rest (A) and one moving away from
the start position at time ta and later returning to this position at time tb (B).
Clearly the time elapsed on clock A (= tbta)is the more than on clock B, since
~ vA = 0 and ~ vB 6= 0. Thus, when the clocks meet, they are not synchronized;
the clock B has aged less. Now one may ask, why can one not turn the
argument around and view the events from the rest frame of B. After all in
special relativity all Lorentz frames are equivalent. Then one should find that
A has aged less than B. This is the so called twin paradox. The solution is
that the rest frames of A and B are not equivalent, because in order to move
away and return to the same point B must be accelerated. This distinguishes
the two paths. Thus, the twin paradox is no paradox, and the twin that has
been traveling through space at a high speed and returns to earth has really
aged less than the one that stayed at home. Note that the equation for the
proper time (47) remains valid also when the motion of B is accelerated. For
a complete description the problem in the frame of B requires the machinery
of GTR, since accelerated frames are involved.


i.e. acceleration is involved and you need General relativity (GTR).

So a course using your book and its not claiming what you are claiming of that book. You have just misunderstood things somehow. It's as I have been saying - to properly handle acceleration you need GR.

Thanks for wasting my time. You had me going for a minute.

But if you genuinely believe that from that book; well students are being taught the opposite from using that book.

none, you dumbsh^t, SR has a chapter that deals with acceleration. But you are so full of crap that you don't know, sh^thead.

None,

I appreciate that you are now developing your subject and digging a bit further.
However it is not wise to discuss in a black and white way about a book that you have not read yourself. (I also skipped myself some paragraphs)

What strikes me is that the most debated aspects are often the less discussed in most books.
Why is that so? Would it be because these topics would be a weea point to be hidden?
No, the reason is that the more you know the less you get emotional.

The twin "paradox" has been discussed since nearly a century.
When you have read at least two books on relativity and solved -say- ten exercices, you cannot heat up anymore on that topic. Instead, you prefer to consider each statement and analyze its value. It is also good for testing our understanding of SR.

It is for sure totally right to solve the twin paradox by the fact that there is an assymetry between these twin. Only one of them is non-inertial at least during a short time.
However, the acceleration plays only a small role in the paradox. (I believe)
Maybe even no role at all depending on where you "feel" there is a paradox.
(personally I have no feeling of a paradox)

To convince you of that, just forget about the twins, but consider a triplet of twins.
They can organize an experiment if they want.
Let us call them A, B and C and see what they did.
Assume twin A will "stay at rest" on the earth.
Assume twin C will travel to a distant place with a clock up to alfa centaurus.
Once he reaches alfa he starts a high-speed (V) travel back to earth.
At the same time (for A), the twin B starts a travel to alfa centaurus at the same high speed (V).
At the time twin B and C meet on their way, they quickly synchronize their clocks to mark the same time. Of course, when C arrives back on earth A will observe the time dilation effect just as in the standard twin paradox.

None, do you feel the triple version of the twins paradox is still a paradox? Why?
And do you still think acceleration plays a role in the twin paradox? Why?
You better don't answer the question.
The goal is not to heat up again, it is to cool down.

Another topic is again about acceleration.

Your remark: ... "i.e. acceleration is involved and you need General relativity (GTR)." is wrong.
Just consider that:

1) relativistic mechanics is a branch of special relativity
2) relativistic mechanics is based on the principles of special relativity
3) relativistic mechanics is a generalisation of Newtonian mechanics ...
4) ... and it agress perfectly with Newtonian mechanics for small velocities (v/c<1) <br> 5) Newtonian mechanics just "deals successfully" with acceleration
6) Newtonian mechanics can even be used in an accelerated frame

If you doubt that Newtonian mechanics can be used in accelerated frame, just go back to any introduction course on mechanics. It is an elementary and classical topic to study how Newton's law F=ma is transformed when going to an non inertial (accelerated) frame. The most famous example it the rotating frame: transforming F=ma to the rotaring frame leads to F'=ma'+Fi where Fi are called inertial forces. The inertial forces in a rotating frame involve the centrifugal force and the Coriolis force. In the same way, in a deccelarating frame of reference (a car) the law of Newton leads to an inertial force equivalent to a gravity force. In these examples you see the three types of inertial forces that appear in Newtonian mechanics in an accelerated frame.

But there is of course a difference between NM or SR and GR.
When you go to an non inertial frame in SR or NM, the laws of physics generally don't keep their simpler inertial form: for example the Newton's law gets the "inertial forces" in addition.
In contrast, in GR, the laws keep their same form in any frame of reference, or more precisely any coordinate system even the most surprising. Eisntein was able to write the laws of mechanics, electrodynamics and space-time dynamics in a totally invariant way. Invariant means that the form of the law is the same independently of the system of coordinates that is chosen.

In summary Newtonian mechanics can deal with acceleration and with accelerated frames of reference, and Special Relativity doesn't do less.

My best advise is that you learn physics in books and not on the web.
You are probably too young and too much bright possibilities to burn your time in useless discussion. Just go forward.

Concerning your web reference (http://csep10.phys.utk.edu/astr162/lect/cosmology/gravity.html):

It says "Einstein's Special Theory of Relativity is valid for systems that are not accelerating"

This does not mean that SR does not apply to accelerated systems.
So this web site is not wrong, but the statement above is just useless and misleading.
A revision would be useful.

Anonymous
>>I appreciate that you are now developing your subject and digging a bit further. However it is not wise to discuss in a black and white way about a book that you have not read yourself.
....
I did point out a course using the book though and it was saying different to you.

Anonymous>>(I also skipped myself some paragraphs)
... Yeah so you might have misread the book.

Anonymous>>What strikes me is that the most debated aspects are often the less discussed in most books.
Why is that so? Would it be because these topics would be a weea point to be hidden?
No, the reason is that the more you know the less you get emotional.
... Don't know what that is supposed to mean; sounds like you are throwing up a diversion. I caught you in a mistake and now you want a smokescreen.


Anonymous>>The twin "paradox" has been discussed since nearly a century.
When you have read at least two books on relativity and solved -say- ten exercices, you cannot heat up anymore on that topic. Instead, you prefer to consider each statement and analyze its value. It is also good for testing our understanding of SR.
It is for sure totally right to solve the twin paradox by the fact that there is an assymetry between these twin. Only one of them is non-inertial at least during a short time.
... Yeah and the point of that is its then GR not SR!!!


Anonymous>>However, the acceleration plays only a small role in the paradox. (I believe)
.... So you don't really know. If you don'y know about that, what makes you think you knew about acceleration in relativity!!


Anonymous>>Maybe even no role at all depending on where you "feel" there is a paradox. (personally I have no feeling of a paradox)
... feelings????? what "feelings" instead of knowing?


Anonymous>>To convince you of that, just forget about the twins, but consider a triplet of twins.
... I think that's a diversion. The point is that twin paradox is solved by GR not SR because acceleration is involved; triplet case -- its still GR case.

Anonymous>>None, do you feel the triple version of the twins paradox is still a paradox? Why?
... Not really a paradox. It is solved by GR. Its still GR-- people are changing velocity becoming non-inertial hence switching from SR scenario to GR scenario.

Anonymous>>And do you still think acceleration plays a role in the twin paradox? Why?
... yes because non-inertial.

Anonymous>>Your remark: ... "i.e. acceleration is involved and you need General relativity (GTR)." is wrong.
... No its not, I was stating the inference of the cited GR course had to say on it. Even when its in black and white that there is a relativity text saying different to you; you don't want to believe it. Well you are just in denial about the evidence aren't you? your beliefs are more religious than scientific. Scientific -- is you are supposed to react to the evidence, but you are more religious and ignore the evidence when it does not fit what you want to believe. I am right aren't I?

Anonymous>>Just consider that:
1) relativistic mechanics is a branch of special relativity
2) relativistic mechanics is based on the principles of special relativity
....ok

Anonymous>>3) relativistic mechanics is a generalisation of Newtonian mechanics ...
... amendment


Anonymous>>4) ... and it agress perfectly with Newtonian mechanics for small velocities (v/c<1) <br> 5) Newtonian mechanics just "deals successfully" with acceleration
6) Newtonian mechanics can even be used in an accelerated frame
If you doubt that Newtonian mechanics can be used in accelerated frame, just go back to any introduction course on mechanics. It is an elementary and classical topic to study how Newton's law F=ma is transformed when going to an non inertial (accelerated) frame. The most famous example it the rotating frame: transforming F=ma to the rotaring frame leads to F'=ma'+Fi where Fi are called inertial forces. The inertial forces in a rotating frame involve the centrifugal force and the Coriolis force. In the same way, in a deccelarating frame of reference (a car) the law of Newton leads to an inertial force equivalent to a gravity force. In these examples you see the three types of inertial forces that appear in Newtonian mechanics in an accelerated frame.
... I don't doubt any of that. The point is that to properly handle acceleration it requires GR. SR amends Newton for velocity case. To amend Newton for acceleration case, Einstein needed GR!!

Anonymous>>But there is of course a difference between NM or SR and GR.
When you go to an non inertial frame in SR or NM, the laws of physics generally don't keep their simpler inertial form: for example the Newton's law gets the "inertial forces" in addition.
In contrast, in GR, the laws keep their same form in any frame of reference, or more precisely any coordinate system even the most surprising. Eisntein was able to write the laws of mechanics, electrodynamics and space-time dynamics in a totally invariant way. Invariant means that the form of the law is the same independently of the system of coordinates that is chosen.
In summary Newtonian mechanics can deal with acceleration and with accelerated frames of reference, and Special Relativity doesn't do less.
My best advise is that you learn physics in books and not on the web.
You are probably too young and too much bright possibilities to burn your time in useless discussion. Just go forward.
.... The point is I was taught that to deal with acceleration you need GR not SR, but you disagreed with that. I pointed out you were wrong, and you just went into a state of denial!!!!!!


Anonymous>>Concerning your web reference (http://csep10.phys.utk.edu/astr162/lect/cosmology/gravity.html):
It says "Einstein's Special Theory of Relativity is valid for systems that are not accelerating"
... yes and not valid for acceleration. If it was valid for acceleration it would have said so!! So the way you twist things around the wrong way and misinterpret this statement is wrong. So you basically don't understand relativity. And when there is evidence in black and white that you are wrong, rather than accept you are wrong, you go into a state of denial, and want the evidence amended. As I reiterate you are not following a scientific point-of-view, instead you have turned this into a religion for you.

none posted this:

"L.D. Landau, E.M. Lif****z, The Classical Theory of Fields, Pergamon, 1983

On lecture 3 it deals with SR applied to Twin paradox, and says you need GR because acceleration involved.

You probably want the whole thing, so Quote:

Twin paradox
Consider a clock moving along an arbitrary world line, with accelerations. The
time measured from space-time point a to b by the clock (the proper time) is
[equation won't come out!](47)
Now consider two clocks, one remaining at rest (A) and one moving away from
the start position at time ta and later returning to this position at time tb (B).
Clearly the time elapsed on clock A (= tbta)is the more than on clock B, since
~ vA = 0 and ~ vB 6= 0. Thus, when the clocks meet, they are not synchronized;
the clock B has aged less. Now one may ask, why can one not turn the
argument around and view the events from the rest frame of B. After all in
special relativity all Lorentz frames are equivalent. Then one should find that
A has aged less than B. This is the so called twin paradox. The solution is
that the rest frames of A and B are not equivalent, because in order to move
away and return to the same point B must be accelerated. This distinguishes
the two paths. Thus, the twin paradox is no paradox, and the twin that has
been traveling through space at a high speed and returns to earth has really
aged less than the one that stayed at home. Note that the equation for the
proper time (47) remains valid also when the motion of B is accelerated. For
a complete description the problem in the frame of B requires the machinery
of GTR, since accelerated frames are involved. "


cinci: You read more into this than it deserves. The key sentence is:

"Thus, the twin paradox is no paradox, and the twin that has been traveling through space at a high speed and returns to earth has really aged less than the one that stayed at home."

In any case, the paradox can be framed using two travellers with no acceleration involved.

Let A be an observer on Earth.

Let B pass the earth in a spaceship at v=.8c and as he does he sets his clock at the same timem as A's.

Let B travel for some periad of time and then passs C in another spaceship travelling toward earth at .8c relative to the earth and a they pass, C sets his clock to read the same as B's.

When C reaches earth and compares the time elapsed, it will show that less time passed for B and C than for A. No acceleration is involved.

If you still aren't convinced, the apply the Lorentz trnasformations treating A as stationary and the assuming B as stationary and you will find no paradox.
****************************

Well none,

If you agree that all books are not necessarily totally consisten with each other,
then why do you chose a few sentense from a nearly unknown web site to forge your opinion?

In addition, simple logic can lead you to the right conclusion.
Why don't you have more confidence in yourself and less confidence in the web.

Maybe the web site you mentioned is from your university.
Then, why don't you ask your professor for some discussion?
Why don't you ask him more details to be sure there is no misunderstanding?

Some exercices:

1) Particle acceleratord design is based on relativistic mechanics.
Do you still think it is just plausible that SR does not deal with acceleration.

2) Newton law F=ma becomes F=ma+Fi (Fi=inertial forces) when transformed to a rotating frame.
A rotating frame is a special case of accelerating frame.
Would you say that Newtonian mechanics cannot deal with acceleration?

3) In relativistic mechanics the Newton's law F=ma is only sligthly different.
It matches perfectly Newtonian mechanics for small velocities.
Would you say that relativistic mechanics cannot deal with acceleration?

Have also a look at these web pages:

http://en.wikipedia.org/wiki/Special_relativity#Force
http://en.wikipedia.org/wiki/Special_relativity#Force_in_4D

Maybe they are right, if you are lucky enough ...

none posted this:
"L.D. Landau, E.M. Lif****z, The Classical Theory of Fields, Pergamon, 1983
On lecture 3 it deals with SR applied to Twin paradox, and says you need GR because acceleration involved.
You probably want the whole thing, so Quote:
Twin paradox
Consider a clock moving along an arbitrary world line, with accelerations. The
time measured from space-time point a to b by the clock (the proper time) is
[equation won't come out!](47)
Now consider two clocks, one remaining at rest (A) and one moving away from
the start position at time ta and later returning to this position at time tb (B).
Clearly the time elapsed on clock A (= tbta)is the more than on clock B, since
~ vA = 0 and ~ vB 6= 0. Thus, when the clocks meet, they are not synchronized;
the clock B has aged less. Now one may ask, why can one not turn the
argument around and view the events from the rest frame of B. After all in
special relativity all Lorentz frames are equivalent. Then one should find that
A has aged less than B. This is the so called twin paradox. The solution is
that the rest frames of A and B are not equivalent, because in order to move
away and return to the same point B must be accelerated. This distinguishes
the two paths. Thus, the twin paradox is no paradox, and the twin that has
been traveling through space at a high speed and returns to earth has really
aged less than the one that stayed at home. Note that the equation for the
proper time (47) remains valid also when the motion of B is accelerated. For
a complete description the problem in the frame of B requires the machinery
of GTR, since accelerated frames are involved. "


cinci: You read more into this than it deserves. The key sentence is:
"Thus, the twin paradox is no paradox, and the twin that has been traveling through space at a high speed and returns to earth has really aged less than the one that stayed at home."
... So what I know. The issue was that the twins is solved by GR.


cinci:In any case, the paradox can be framed using two travellers with no acceleration involved.
Let A be an observer on Earth.
Let B pass the earth in a spaceship at v=.8c and as he does he sets his clock at the same timem as A's.
Let B travel for some periad of time and then passs C in another spaceship travelling toward earth at .8c relative to the earth and a they pass, C sets his clock to read the same as B's.
When C reaches earth and compares the time elapsed, it will show that less time passed for B and C than for A.
... acceleration involved when C gets back to Earth.

article says "For
a complete description the problem in the frame of B requires the machinery
of GTR, since accelerated frames are involved. ""
You seem to miss that.

Anonymous>>If you agree that all books are not necessarily totally consisten with each other,
then why do you chose a few sentense from a nearly unknown web site to forge your opinion?
... I do not. I am open minded. I looked at your claims and pointed out that your claims are not being taught to relativity students even when they use the book that you misunderstand to draw your false beliefs. It is you being close minded. I have repeatedly pointed out from several independent sources that you are wrong, and rather than accept that you want to dimiss the evidence. Now you cite wikipedia. Ecen wikipedia disagrees with you-- QUOTE:

"After completing his theory of special relativity, Albert Einstein realized that forces felt by objects undergoing constant proper acceleration are indistinguishable from those in a gravitational field. This was the basis for his development of general relativity, a relativistic theory of gravity. This is also the basis for the popular twin paradox, which asks why one twin ages less when moving away from his sibling at near light-speed and then returning, since the non-aging twin can say that it is the other twin that was moving. General relativity solved the "why does only one object feel accelerated?" problem which had plagued philosophers and scientists since Newton's time (and caused Newton to endorse absolute space). In special relativity, only inertial frames of reference (non-accelerated frames) can be used and are equivalent; general relativity considers all frames, even accelerated ones, to be equivalent. (The path from these considerations to the full theory of general relativity is traced in the introduction to general relativity.)"

i.e. SR for non-accelerated case and GR for acceleration.

Anonymous: Maybe the web site you mentioned is from your university.
Then, why don't you ask your professor for some discussion?
Why don't you ask him more details to be sure there is no misunderstanding?
... The misunderstanding is your end; why should I discuss with others your misunderstandings; that is personal to you. You have the choice of ignoring the evidence and believing what you like; and that is what you are doing. As I have pointed out that is a religious belief on your part rather than a scientific perspective.

Anonymous>1) Particle acceleratord design is based on relativistic mechanics. Do you still think it is just plausible that SR does not deal with acceleration.
... relativity deals with acceleration; so what.

2) Newton law F=ma becomes F=ma+Fi (Fi=inertial forces) when transformed to a rotating frame. A rotating frame is a special case of accelerating frame.
Would you say that Newtonian mechanics cannot deal with acceleration?
... Newton is an approximation to relativity.

3) In relativistic mechanics the Newton's law F=ma is only sligthly different. It matches perfectly Newtonian mechanics for small velocities.
Would you say that relativistic mechanics cannot deal with acceleration?
... relativity deals with acceleration. Its just YOU misunderstang HOW relativity deals with acceleration.
I refer you to the three sources that point out you are wrong. And I pose the question again-- admit it YOU have a religious perspective of being close minded on this subject rather than a scientific perspective.
It makes things easier to understand and appreciate if you and others like you admit you have relativity as a religion; wouldn't you agree?

Ok none,

I did not agree with your previous claim

... SR is not considering acceleration ...

but now I see that you changed your mind:

relativity deals with acceleration

and that's ok now.

There was no need to discuss the motivations of GR.
I know that very well.

It is true that solving the "twin paradox" has another flavor in GR.
Considering that standard twin story, where one of the twin must experience an acceleration at some time, then the effect observed should be equivalent to a gravitational field, by the equivalence principle.

And indeed, GR brings acceleration and gravity on the same foot which SR or NM don't do, of course.
But that doesn't mean that SR doesn't deal with accleration or even with gravity.
And actually, GR is not needed to solve the twin paradox.

I would even go further!
========================
The twins paradox has been conceived during duscussion of the implications of SR.
This means that the "paradoxical" aspect is actually derived from SR.
I explained you that the acceleration of one of the twins proves an assymetry.
This removes what is usually perceived as the paradox, since the twins are the same.
However, the effect is not due to the acceleration, it is a purely kinematic effect.

This is seen immediately from the time dilation law.
The clocks are simply running differently for the two twins.
And this just applies for the atoms making up each of the twins, since atoms are very much like clocks.
This is what explains physically the paradox.
(talking twins instead of clock is just more spectacular)

But then, would the acceleration not bring an additional effect, not included in the (kinematic) time dilation effect.
I think this is the case.
And probably, the final time difference that will be observed will be different if the traveling twin reverse his motion slowly or abruptly.
I take that as obvious, since the acceleration is equivalent to a gravitational field and therefore it should dilate time.
If the back-acceleration is very strong, the traveling twin could experience a near black hole effect, where time would slow down very much. Isn't it?

Therefore, I think the total time difference will be a sum of two effects: the pure SR effect and an additional GR effect: dt(SR)+dt(GR).
The usual twin paradox discussion is only about the first term dt(SR).

Maybe you try that as GR exercice?
Who knows, it could reveal more surprise in theoretical physics?
Check the web also, this might not be a news, I don't know.

Anonymous>>but now I see that you changed your mind:
relativity deals with acceleration
and that's ok now.
... I'm not changing mind, relativity is SR and GR.


Anonymous>It is true that solving the "twin paradox" has another flavor in GR. Considering that standard twin story, where one of the twin must experience an acceleration at some time, then the effect observed should be equivalent to a gravitational field, by the equivalence principle.
And indeed, GR brings acceleration and gravity on the same foot which SR or NM don't do, of course.
...ok

Anonymous>>But that doesn't mean that SR doesn't deal with accleration or even with gravity.
...never the issue. SR does not deal with them as properly as GR.


Anonymous>>And actually, GR is not needed to solve the twin paradox.
I would even go further!
The twins paradox has been conceived during duscussion of the implications of SR.
This means that the "paradoxical" aspect is actually derived from SR.
I explained you that the acceleration of one of the twins proves an assymetry.
This removes what is usually perceived as the paradox, since the twins are the same.
However, the effect is not due to the acceleration, it is a purely kinematic effect.
This is seen immediately from the time dilation law.
The clocks are simply running differently for the two twins.
And this just applies for the atoms making up each of the twins, since atoms are very much like clocks.
This is what explains physically the paradox.
(talking twins instead of clock is just more spectacular)
But then, would the acceleration not bring an additional effect, not included in the (kinematic) time dilation effect.
I think this is the case.
And probably, the final time difference that will be observed will be different if the traveling twin reverse his motion slowly or abruptly.
I take that as obvious, since the acceleration is equivalent to a gravitational field and therefore it should dilate time.
If the back-acceleration is very strong, the traveling twin could experience a near black hole effect, where time would slow down very much. Isn't it?
Therefore, I think the total time difference will be a sum of two effects: the pure SR effect and an additional GR effect: dt(SR)+dt(GR).
The usual twin paradox discussion is only about the first term dt(SR).
Maybe you try that as GR exercice?
Who knows, it could reveal more surprise in theoretical physics?
Check the web also, this might not be a news, I don't know.
... I pointed out your mistake as regards SR and GR. The start of this thread is LSU professor resolves Einstein's twin paradox, and you diverted it on to your misunderstandings with SR and GR. From what you are saying above, you have lots of ther misunderstandings with relativity.

Just playing with the words now:

" SR does not deal with them as properly as GR. "

Of course the the ranking in coherence is NM < SR < GR ! <br> Can be read in the newspaper.

Anonymous>Just playing with the words now:
" SR does not deal with them as properly as GR. "
Of course the the ranking in coherence is NM < SR < GR ! <br> ,, If you want to look at it that way; you used the words inappropriately.

None,

That's just normal that I use words incorrectly since English is not my mother tongue.
And it is also normal that you just play with the words, since this is easier for you than going deeper in the physics. That's what I concluded by observing you.

Anyway, I think I tried my best both with english and with some tracks I gave you.
You also were not that bad, since I had some good idea anyway discussing with you.
I like the idea of "kinematic twin effect" and "dynamic twin effect", as those part being due to SR and GR(acceleration) respectively.

I am closer to retirement than to graduation.
Therefore, you might be in a better position to try to estimate "kinematic" and "dynamic" twin effect.
(well I have to work also and in my hobby time I am more interrested in quantum mechanics and in applied mathamatics)

I enflaed others on "acceleration".
Few responses, but enough for me.

http://www.physicsforums.com/showthread.php?t=291282

Enjoy your retirement, Anonymous.

I suppose is difficult to deal with talking about relativity where the setup is-

NM <-SR <-GR <br>
where NM is an approx of SR, and SR is an approx of GR.

And probably is the sort of some of the confusion.

To none,

I could have saved the professor some time. There really isn't any paradox. If you think there is, then post what you think it is.
**********************