About interpretations and logic...

[enridp]

Hello everyone !

I want to ask you something and I hope you think your answer and not just reply with an orthodox foundation. I'm not another Einstein's enemy, I believe in SR but sometimes I just can't imagine some situations...

Look at this:

I will use the famous twin paradox because it is known for all... but I won't answer who is younger at the end, we know "Earth-Twin" is older, now... WHEN "Traveler-Twin" get this difference? was it during his acceleration? was it during his inertial movement (outbound or inbound travel?).

Even more... let me modify our paradox:

Now the "Traveler-Twin" never returns to the Earth. Does he remain younger?

And if we don't know WHO accelerates? who is younger?

I hope you can understand my doubt. To me, THERE is the real paradox... and I don' think relativity of simultaneousness solves it...

Someone told me once:

If nobody is accelerating and nobody turns back, then, they cross at maximum ONE time, and then is not relevant who is younger...

I can understand that answer in a practical way, but I think it's not acceptable from a theoretic point of view.

I think SR, with the current interpretation, can't solve this.

But look at this:

I we assume there's a preferential frame of reference, if we assume the nature of universe is NOT the same for all inertial observers, BUT:

every physical theory should look the same mathematically to every inertial observer, and the laws of the universe are the same regardless of inertial frame of reference, so, we left the equations of our SR unbroken, and we save our "logic", because now, like before, we can't answer WHO is younger... but we KNOW that one of them is younger... I think there's an important difference, because again, we can't save our practical problem, but yes the theoretic one.

Now, why the science community choose the first interpretation of SR, which is so cruel with our logic if the second interpretation take us the SAME equations and preserves our logic?

Is there some problem with this second interpretation?

Please, again, I'm not trying to break up the SR or something similar, I'm just trying to solve this logic paradox...

 

Thanks for read!

(and thanks a lot if you reply...)

 

enrique.

[theCPE]

I am not sure I understand what twin scenario you are trying to suggest causes SR logical problems?

 

If the twin doesn't come back then you can't compare the ages, which has nothing to do with whether or not SR still holds up, you just can't complete the experiment so to speak. The acceleration of the traveling twin isn't what causes them to age slower, it is the velocity.

 

But like I said, I can't really tell what you are saying, rephrase?

[Klaynos]

The twin paradox cannot be considered with SR as there are non-inertia frames involved... I also believe that it is possible to always tell which of two objects is the accelerating one...

[timo]

WHEN does the "Traveler-Twin" get this age-difference?

Interestingly, that question doesn´t really make sense. You can compare it with a classical example: I travel to some other city by car. I can either take the highway or some shortcuts using smaller roads. When I arrive via the highway, the distance I travelled is bigger than it had been had I used the smaller roads. At which point on the highway did I travel additional kilometers? Of course, there is no such point. The highway simply is the longer route.

The different aging of the twins is pretty much the same thing. They took different paths from A to B, so the time they experienced on the way can differ.

 

Someone told me once: If nobody is accelerating and nobody turns back, then, they cross at maximum ONE time, and then is not relevant who is younger... I can understand that answer in a practical way, but I think it's not acceptable from a theoretic point of view.

From a more theoretical point of view: At which two point on their respective paths through spacetime would you compare who is older? A quite natural aproach is taking two point that have the same time coordinate in some coordinate system. The question that you encounter then is: Would those two points have the same time coordinate in some other coordinate system? The answer to that question is: They do exactly if they also have the same space coordinates, too. In other words: If you compare the ages at the point where the twins meet, then you are comparing the same points on their path through spacetime for all coordiante system. If you´re comparing the ages when they don´t meet, then you´re comparing two pretty much arbitrary points (the points compared depend on the coordinate system chosen) on their path and can get pretty much any result you want.

To compare it with my previous example: Assume you wanted to find out where I have to drive the extra-kilometers when using the highway. So you decide to compare the kilometers already traveled not at the destination town but somewhere along the route. Which points on the routes do you compare with each other? You could chose some comparison like "I compare points at which you taveled an equal distance to the north". But that is not a better choice than comparing points with an equal distance travelled to the west or comparing points at which you have an equal altitude over the ocean surface.

 

 

But look at this:

If we assume there's a preferential frame of reference, if we assume the nature of universe is NOT the same for all inertial observers, BUT:

every physical theory should look the same mathematically to every inertial observer, and the laws of the universe are the same regardless of inertial frame of reference [...]

Is there some problem with this second interpretation?

My personal problem with this "second interpretation" is that I´m not understanding what you´re saying. You´re saying that you want to leave all the maths unchanged but want to alter the interpretation of the results? Are you saying that a stone doesn´t always fall down because if I turn myself head-down I see it falling up and therefore the coordinate system where my feet are on the ground is a prefered one (it is my prefered one, for sure )?

[enridp]

Hello again !

First, thanks for your replies.

Now, I think I'm not explaining well, maybe it's due my poor english, sorry for that, I'll try to do it better now:

Atheist understood my question very well, so I will try to follow his answers and to explain me better.

The classical travel It's an interesting comparison, maybe it really has no sense to wonder WHEN does the time difference appears. I need to think that a bit more... But look at this situation:

Two ships (A and B) in middle of the universe, they meet in a moment, call it t=0. Both are perfect inertial frames. Now A will say: "B's time is going slow", and B will say: "A's time is going slow".

So who is right?

Many people accept the answer:

*both AND nobody

And it really breaks my logic. But if we now say something like:

OK, every physical theory should LOOK the same mathematically to every inertial observer, and the laws of the universe LOOK the same regardless of inertial frame of reference, BUT EXISTS a preferential frame, somewhere, although we can not detect it. Now we still without knowing who is right, A or B, but we know they can't be right at the same time.

SR is not changed, only its interpretation, at least I think so... and we save our logic...

Now, have passed more than 100 years and the original interpretation remains in the science community, then, my question is:

* What is the problem with the "new" (at really is not new, and of course, not mine...) interpretation of the SR? What is wrong with it? if it preserves all the mathematical structure and it's more logic, why we are not using it?

 

greets!

enrique.

[theCPE]

Ok, I think I might see what you are asking now.

 

When A and B pass each other they both observe the other as being the one with slower time whether they both are moving the same velocity or one is stationary and the other is moving a high velocity (large fraction of light).

 

And you want to know which one is right?

 

Well the answer is of course the name of the theory. It is relative. They both feel they are right and they both are; relative to their reference point the other is the one experiencing the time dilation.

 

As far as a universal reference frame you keep referring too; it doens't exist. There is no universal reference frame.

 

Maybe that is helpful?

[enridp]

Hi theCPE !

Yes, something like that is what I'm asking.

Now, your answer is therefore the classical:

* both and nobody (it's relative...)

But I don't know... to me is really easier to think that someone, and only ONE, is in the right way... the right answer is in hands of that hypothetical universal reference frame. It only modifies our interpretation of the results... again, we don't change our equations, but now we say:

We don't know if A or B has the right answer, but we know THERE IS a right answer... I think this point of view is easier to visualize and eliminate many paradoxes.

Let me go back to the twin paradox:

A -> Earth-Twin

B -> Traveler-Twin

When B is going, we KNOW(*) his time is going slow, we don't say "it's relative", there's a reality there...

My example is the same thing, but now we don't know who accelerated... and for that we just say now the reality is relative? That's my logic problem...

And I don't understand why nobody accepts the alternative interpretation. At really, I'm trying to find a problem with this alternative interpretation, that is the really subject of this post, because I can't sleep fine with two possible interpretations

 

(*) Here I must to clarify something I think...

In the "aternative" interpretation (there's a universal reference frame, somewhere), although B is who accelerated we can't know if B's time is going slower than A's time. We can be sure that B is younger if he returns, but we can't know (without knowing where is the universal frame...) who is younger in a going travel only...

[theCPE]

Yeh, it would be nice to be able to say one is right but again, that assumes a universal reference and there isn't one.

 

Of course for the twin paradox you can KNOW the right answer if you perform the experiment the conventional way. They both need initial reference frames that are the same...earth, then one travels one doesn't, upon arriving home the answer of whom was right, A or B (since both saw the other as having dilated time) becomes obvious...the one that didn't leave earth.

[Klaynos]

Yeh, it would be nice to be able to say one is right but again, that assumes a universal reference and there isn't one.

 

It's often been said that science doens't care whether it's nice or not just that it's as true as we know... (Which I know is your point)...

[enridp]

Yeh, it would be nice to be able to say one is right but again, that assumes a universal reference and there isn't one.

 

OK, here is my problem... I mean, How do you prove there isn't a universal reference? I'm not trying to change nothing, just trying to understand... because I know it's really difficult to prove the non-existent of something, but I think should be some crucial difference if we accept a universal reference, because if the two interpretations are equally valid, then why we choose the first and no the second?

This is what I'm asking at really and what I'm trying to solve...

In principle I think there's a principal difference:

If we accept a universal frame, then the physics allow us to have velocities higher than "c", then will be possible to find where is the universal frame.

But I can find just that difference. I think I'm losing something.

What is the problem with a universl frame?

[timo]

What is the problem with a universal frame?

The main problem is that you attribute physical reality to a coordinate system which, from a standpoint of relativity, is simply a tool for humans to put reality into a form that you can do calculations in. The two paths in my example about travelling to another town above "have a reality" (exist, are unchanged regardless of, ...) independent of the way I use to describe them. Whether I use GPS coordinates to describe the path or describe it via informations like "... after 3 km turn right on route B26, follow that route for 10 km, then ...".

 

I´ve seen that on physicsforums.com someone gave you a similar classical example about two lines on a piece of paper. I´ve not completely read it but you could try to follow the steps he presented. The key point is, that the two lines on the piece of paper exist regardless of whether you draw a coordiante system on the piece of paper to describe the line-points via their coordiantes or not.

[swansont]

If there is a universal reference frame, we should be able to measure our speed when we are moving with respect to it.

 

We choose reference frames because of convenience in solving problems, but as far as we've measured, we still get the right answers when we use different ones.

[Jacques]

I mean, How do you prove there isn't a universal reference?

It is a postulate of relativity, it is the concept on witch relativity is build. You can imagine a theory with a universal reference, but it won't be relativity.

[Amr Morsi]

Hi Sir,

 

With respect to the twin paradox, it can totally be accounted for by the Special Relativity, even though acceleration is involved (can be included in SR, as opposite to many people may think). Science now has settled down to that the traveller (accelerating and decelerating) is the younger. But, I can say with confidence, other serious deeper researches say that they will be equal in age, after accounting correctly for acceleration in SR.

 

A simple check, look to the other twin from the versus-frame-of-reference. What is the situation? It is totally the opposite.

 

Buddy,

Time Transfer is only accounted for in GR, WHERE MASSES ARE AFFECTING THE SPACE-TIME CURVATURE.

 

May be I pointed it out. But, I studied it and Experimentally.

[swansont]

Hi Sir,

 

With respect to the twin paradox, it can totally be accounted for by the Special Relativity, even though acceleration is involved (can be included in SR, as opposite to many people may think). Science now has settled down to that the traveller (accelerating and decelerating) is the younger. But, I can say with confidence, other serious deeper researches say that they will be equal in age, after accounting correctly for acceleration in SR.

 

No, it has been experimentally confirmed that the accelerating clocks do actually run at the different rate. The twins would not be the same age.