[PhysBang]

I proved my point. I think you can understand but you just don't want to admit it... If not, think again and look for "Einstein and the twin paradox". There are many good articles...

Yes, and like the one linked to above and like the YouTube video, the good articles establish that there is no paradox and that SR handles the scenario quite well. I'm not sure what you imagine your point is, but given that you have abandoned the English language, I'm betting that it doesn't really matter.

[CPT ArkAngel]

You just proved another of my points again! And English is not my first language by the way. You are accusing me of not reading your links but you didn't read carefully my arguments. You just rely on alleged experts. Read about Einstein point of view of the twin paradox after 1914. Before that he never truly expressed himself on the subject other than saying he didn't see any problem with it. But he changed his mind. There is a very important distinction between proper time and relative time. Relative time is a communication time while proper time is the actual time in a specific frame.

"Prime is moving along (and always has been) at the speed v" is a statement of unknown, unreality and incompleteness.

The fact that you can compare proper time and calculate it involve a necessary acceleration. The subjects must be in the same frame at some point and at least one must have an acceleration... The fact that they are twins implies acceleration... 
 

[yor_on]

CPT, you could make it simpler if you like. Your 'proper time' is what you always carry around. Where ever you go, or fast, or mass. One way to describe a 'frame of reference' is using ones wrist watch. That holds generally speaking. And arguing with PhysBang about his studies is a dangerous thing my man, not impossible but indeed difficult :)

[PhysBang]

You just proved another of my points again!

Since your points center on the idea that the twin "paradox" is a real paradox and that there is no way in SR to habdle the paradox, your points have been thoroughly refuted.

 

And English is not my first language by the way.

My apologies.

You are accusing me of not reading your links but you didn't read carefully my arguments. You just rely on alleged experts.

Well, no, since in the past I've actually worked through the twin scenario.

Read about Einstein point of view of the twin paradox after 1914. Before that he never truly expressed himself on the subject other than saying he didn't see any problem with it. But he changed his mind.

Einstein later developed a theory that treated the geometry of spacetime with more precision, of course he would update his approach. Still, please show the citation for your claim.

 

There is a very important distinction between proper time and relative time. Relative time is a communication time while proper time is the actual time in a specific frame.

The lesson of relativity is that one can always determine proper time from a determination of relative time and other factors and one can always tell from relative speed what proper time will be.

"Prime is moving along (and always has been) at the speed v" is a statement of unknown, unreality and incompleteness.

Says you. The scenario is an idealized one and, since we are using SR, giving relative speed gives proper time.

The fact that you can compare proper time and calculate it involve a necessary acceleration.

That's a wonderful theory you have, but it isn't SR.

The subjects must be in the same frame at some point and at least one must have an acceleration... The fact that they are twins implies acceleration... 

OK, so you are just ignoring the scenario where there were no twins, just clocks, and the numbers work out anyway.

[guest4091]

A non accelerating frame is chosen as the observer. But why? This is the key to understand the problem. The problem is swept under the carpet from the beginning. This is a reduction to Lorentz equations.

SR was developed within the range of constant linear (inertial/free from accelerations/unchanging) motion, because it's free from the complexities of gravity.
I looked under the carpet and there's nothing there! It's unfortunate you spent 30 yrs with the misguided role of acceleration. Acceleration is a means to an end. Once you reach target speed, clocks continue to lose time. If you use a ladder to climb a tree and break a leg falling to the ground, the ladder didn't cause the injury.

Experimental evidence.
The clock hypothesis states that the tick rate of a clock when measured in an inertial frame depends only upon its velocity (speed) relative to that frame, and is independent of its acceleration or higher derivatives.
   Bailey et al., “Measurements of relativistic time dilation for positive and negative muons    in a circular orbit,” Nature 268 (July 28, 1977) pg 301. Bailey et al., Nuclear Physics B    150 pg 1–79 (1979).
They stored muons in a storage ring and measured their lifetime. When combined with measurements of the muon lifetime at rest this becomes a highly relativistic twin scenario (v ~0.9994 c), for which the stored muons are the traveling twin and return to a given point in the lab every few microseconds. While being stored in the ring they were subject to a proper acceleration of approximately 10^18 g (1 g = 9.8 m/s2). The observed agreement between the lifetime of the stored muons with that of muons with the same energy moving inertially confirms the clock hypothesis for accelerations of that magnitude.

1. Why do moving clocks run slow?
Fig.1 is a light clock moving to the right along the popular x axis at some fraction of light speed. It consists of an emitter/detector on the bottom with a mirror m at the top 1 unit distance. A second is defined as k cycles of a photon moving to m and returning. The light paths (blue) are shown for three speeds .3, .6, and .8. Since light speed is constant and independent of the source (it does not acquire the speed of the source), the photon direction can only rotate to maintain its position relative to the mirror. Geometrically the light vector is resolved into an x component which compensates for the clock motion and a p (perpendicular) component which becomes the working part of the clock, i.e. light speed is <c inside the moving clock.  Compared to R the clock at rest, the cycle time is .95 sec at .3c, .8 second at .6c, and .6 sec at .8c. This motion induced phenomenon is not restricted to clocks, but any process involving energy transfer via em forms. Observer biology is chemistry, therefore they are not aware of the slow running clock. There is no mystery with relative speed. You have to aim ahead of a moving target in order to hit it. In terms of energy, at increasing speeds, light spends more energy chasing the moving clock and less in the clock function.

Fig.2 is a 'hermann' aka 'Minkowski spacetime diagram', but I don't care for verboseness. The vertical axis is 'time' in terms of light speed, light (seconds, years, ...). Einstein originally formulated his theory using spatial dimensions and time. Minkowski generalized these variables into a 4D theory. Despite the abstraction, his ct notation is beneficial since the graph now plots object motion vt to light motion ct, a speed profile. It's also necessary scaling for a usable graph since the distance unit ls is 30 million times the time unit sec. If vt/ct = 1, then light speed profile is a 45 deg line. The selected speeds A and B are straight lines, and thus constant. Our interest now is the lost time (red) for each clock when compared to the R clock.

Fig.3 shows a 3rd clock B2 moving at 0, getting a clock reading while passing B1 and passing A at 1.33 R-time. Rotating the graph 180 deg, the lost time for the rejoining portion is noted.  Lost time for A is .27 sec vs .40 sec for B. B is younger than A.
If the B1 speed profile increases more time is lost. If the B1 speed profile is less than A, less time is lost compared to A but the B2 profile will lose more. Rotate the graph 180 deg. and interchange B1 and B2 to verify that the order of short path-long path makes no difference.
The least amount of lost time occurs for the A profile, and any profile that differs loses more time. The blue rectangle represents light speed constraints, i.e. a stopped clock.
 
time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4981 times)

time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4981 times)

time dilation 170406-3.gif (5.09 kB . 372x432 - viewed 4981 times)

[CPT ArkAngel]

If you understand my arguments, you should understand there is not a single of your arguments disproving mines, even though the mechanics you explained is right. Within SR it is true, but when you scrutinize the implications, you find it is impossible.

Case 1.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.

Case 2.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true. There is something missing because it contradicts case 1. You need external frames to explain otherwise but there is none in case 1, so you limit your cases to non accelerating frames.

After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes. So SR is not a perfect solution but just an approximation of reality. As certainly GR is...

[CPT ArkAngel]

The key to that is in case 1, the twin going away must push the other twin to move! So no one will age slower than the other... If you don't consider any net energy transferred or lost by pushing, which is in fact the key...

[PhysBang]

If you understand my arguments, you should understand there is not a single of your arguments disproving mines, even though the mechanics you explained is right. Within SR it is true, but when you scrutinize the implications, you find it is impossible.

As far as I can tell, you do not have an argument.

You wrote, "All explanations within the frame of SR alone are wrong because there is no key to differentiate the twins." That's simply false, as many citations above have established.

You wrote, "The change is associated to the twin in the rocket by a purely arbitrary a priori choice." That is also false, because even the twin in the rocket knows that she changed direction.

You wrote, "There are no explanations concerning acceleration and inertia in SR." This is also false, because every textbook that deals with SR covers acceleration.

You wrote, "In Special Relativity, the acceleration is entirely reciprocal for both twins." That is false because, again, if we are to include acceleration, the acceleration for one twin is different because she changes direction according to her own initial trajectory.

You wrote, "SR is not just an add on to Newtonian mechanics, it is the start of a new theory." And while it is true that SR is in some sense a new theory, it begins with the assumption of Newtonian mechanics.

You wrote, "With SR alone, you cannot really explain why the accelerating frame will have a slower time." And there are various demonstrations that this claim is false.

Case 1.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.

Sure, and this will be the case using SR alone. Which was the point of developing the "paradox" in the first place.

Case 2.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true.

What is "in reality"? Are you just another run-of-the-mill crank SR denier? If we accept SR, then, "in reality" requires us to describe motion relative to some system of coordinates. So A is time dilated relative to B in a reference frame co-moving with B and B is time dilated relative to A in a reference frame co-moving with A. There is no perspective outside of a reference frame.

There is something missing because it contradicts case 1. You need external frames to explain otherwise but there is none in case 1, so you limit your cases to non accelerating frames.

Only your idea of relativity, not SR, has any contradiction here. This is why we should continue to use SR and reject your idea of relativity.

After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes. So SR is not a perfect solution but just an approximation of reality. As certainly GR is...

GR is entirely irrelevant to the question of what SR actually says.

[PhysBang]

The key to that is in case 1, the twin going away must push the other twin to move! So no one will age slower than the other... If you don't consider any net energy transferred or lost by pushing, which is in fact the key...

That's a nice fantasy physics, but it's not SR. Or GR.

[CPT ArkAngel]

There is no point to argue with a wall, especially a circular one. At least, I know what I don't understand, but you don't!

There is no such a thing as a uniform motion in the real universe and no two elements can be in the same frame.

You are quick to judge without any proof. You constantly use unfounded attack trying to discredit others. Though, I usually agree with you, you have a narrow mind. And this is not unfounded.

You are making extensions by fantasy, not me, by interpreting and wrongly adding things to what I've said.

I don't play to "King of the Hill"...

[PmbPhy]

is the twin paradox real ? is there any experiment of two twins one traveling at high speed and one on earth at rest aging differently ?

Yes. Its real. While some people may imply that it hasn't actually been observed in real life we know from the theory of relativity and the confirmation of that theory, especially concerning time dilation, that it is indeed real.

Never take seriously statements by those who imply a particular thing has never been observed to mean its not "real". That's like assuming that because nobody has ever observed a hippopotamus walk around Boston's city hall to meant that one can't theoretically do so.

In the present case its an observed fact that time dilation is real, i.e. a fact of life. That fact quite literally means that the win paradox is real. Those who claim otherwise don't know what they're talking about in that their philosophical grounding is totally false and without any merit. Since its pretty much a fact of life that others will post some nonsense claiming otherwise I refuse to respond to such ignorant responses.

BTW - that's not meant as an insult but as a scientific fact of life.

[PhysBang]

is the twin paradox real ? is there any experiment of two twins one traveling at high speed and one on earth at rest aging differently ?

Yes. Its real. While some people may imply that it hasn't actually been observed in real life we know from the theory of relativity and the confirmation of that theory, especially concerning time dilation, that it is indeed real.

Never take seriously statements by those who imply a particular thing has never been observed to mean its not "real". That's like assuming that because nobody has ever observed a hippopotamus walk around Boston's city hall to meant that one can't theoretically do so.

In the present case its an observed fact that time dilation is real, i.e. a fact of life. That fact quite literally means that the win paradox is real. Those who claim otherwise don't know what they're talking about in that their philosophical grounding is totally false and without any merit. Since its pretty much a fact of life that others will post some nonsense claiming otherwise I refuse to respond to such ignorant responses.

BTW - that's not meant as an insult but as a scientific fact of life.

Yes, time dilation is real, but that doesn't mean that there is some sort of paradox in existence! The term "paradox" is used to indicate that this twin scenario means that there is some sort of problem with SR. There is not.

[PhysBang]

There is no such a thing as a uniform motion in the real universe and no two elements can be in the same frame.

A frame of reference is, by definition, an idealization. And by that idealization, all objects are in every well-formed frame of reference.

You are quick to judge without any proof. You constantly use unfounded attack trying to discredit others. Though, I usually agree with you, you have a narrow mind. And this is not unfounded.

I try to narrow my mind to what is justified by the evidence and, in the case of where a text is involved, the actual text. I'm sorry that you don't think that quoting what you actually wrote is good evidence about your actual positions and I'm sorry that you don't think that Einstein's paper on SR is good evidence about the content of SR.

[guest4091]

CPT#49
From the 1905 paper, par 4:
“From this there ensues the following peculiar consequence. If at the points A and B of K there are stationary clocks which, viewed in the stationary system, are synchronous; and if the clock at A is moved with the velocity v along the line AB to B, then on its arrival at B the two clocks no longer synchronize, but the clock moved from A to B lags behind the other which has remained at B by  (up to magnitudes of fourth and higher order), t being the time occupied in the journey from A to B.
It is at once apparent that this result still holds good if the clock moves from A to B in any polygonal line, and also when the points A and B coincide.
If we assume that the result proved for a polygonal line is also valid for a continuously curved line, we arrive at this result: If one of two synchronous clocks at A is moved in a closed curve with constant velocity until it returns to A, the journey lasting t seconds, then by the clock which has remained at rest the travelled clock on its arrival at A will be  second slow.”
The author A.E. has previously described clock synchronization, and now demonstrates that it only applies to that frame at its current speed. If one of the clocks moves relative to that frame, its rate changes and synchronization is lost.
Note he doesn’t concern himself with the means of acceleration to v, since it is not a relevant factor, and acceleration can be approximated with a polygonal line.
It seems your chain of causality is faulty,

[yor_on]

Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true. There is something missing "

I know, that one hurt me too until I realized that all 'time dilation's' are the same. The 'twin experiment' is just a time dilation taking into the extreme. It's a proof of a concept CPT, and as such you will need a mathematical proof to refute it.

[CPT ArkAngel]

Time dilation is real, I've never expressed the contrary. But the SR explanation of the twin paradox is ultimately wrong or at least flawed due to incompleteness, even though in reality the twin accelerating will be truly younger if you make abstraction of gravity.

Read Einstein on the twin paradox... Later conclusions are very different after he looked at it in a deeper way. Before that, he thought about it as a measuring experiment, not as a real explanation of proper time dilation.

[PhysBang]

Time dilation is real, I've never expressed the contrary. But the SR explanation of the twin paradox is ultimately wrong or at least flawed due to incompleteness, even though in reality the twin accelerating will be truly younger if you make abstraction of gravity.

Sure. You believe this despite all the demonstrations that the situation is explained exactly in SR. You have this belief about gravity even though you haven't actually worked through the effect that gravity supposedly has on this scenario.

Read Einstein on the twin paradox... Later conclusions are very different after he looked at it in a deeper way. Before that, he thought about it as a measuring experiment, not as a real explanation of proper time dilation.

You keep saying this, but you have no citation. Even if your citation is not purely a fabrication, Einstein often got some of the implications of relativity incorrect. So we need to see his actual statement and his reasoning to compare it to the actual mathematical reasoning of SR presented in the multiple citations above.

[CPT ArkAngel]

I've never said that SR was wrong. I said the explanation of the twin paradox within SR, making abstraction of acceleration is ultimately incomplete and it doesn't truly explain proper time dilation. Everything I wrote is consistent with this statement.

You can search by yourself, there are many references. What I am saying is not new. It is understood by the best theorists.

[guest4091]

CPT;
I have read later publications by Einstein, Max Borne, and others, and NEVER saw the math formulas include acceleration  as a factor. Maybe you had a vision.

[PmbPhy]

If you understand my arguments, you should understand there is not a single of your arguments disproving mines, even though the mechanics you explained is right. Within SR it is true, but when you scrutinize the implications, you find it is impossible.

Your analysis is incorrect, i.e.

Case 1.
There are only the two twins in the universe and one is going away and come back, the only difference is acceleration and deceleration. The twin subjected to accelerations is now younger.

This part is correct.

Case 2.
Astronaut A encounters astronaut B and they have a relative speed V. Each of them has the same relative time rate for the other, it is reciprocal within SR. But in reality, it cannot be true.

This part is incorrect. In fact it tells me that your understanding of the twin paradox is quite flawed. When the twins have the same acceleration relative to an inertial frame is not a twin paradox. Its only a twin paradox, as the term is defined in the literature, when one twin is at rest and the other accelerates away from a point in space and later returns to the same event, i.e. when one of the worldlines is a straight line in spacetime and he other worldline is curved and both start and end at the same place in space. Therefore what you describe here is not a twin paradox.

After GR, we understand that SR is never true because as soon as one moves, the gravitational potential changes.

This is incorrect as well. In fact this part of your response is a common mistake, i.e. that SR doesn't apply to accelerating objects in an inertial frame.

GR doesnot apply to accelerating body's in an inertial frames but only when one is analyzing events from a frame at rest in an accelerating frame. SR only applies to inertial frames.

So SR is not a perfect solution but just an approximation of reality. As certainly GR is...

Incorrect as well for reasons stated above and does provide a perfect solution.