[General] STR twin Paradox

[Viv Robinson]

Hi Chip,

Referring to your “imagine” section, highlighted in bold below. How do you synchronize clocks when you don’t know their velocity or how far apart they are? They can only communicate with each other by photons. You have two unknowns, speed and distance, and only one variable, redshift. They can be synchronized if they have a common reference point. That returns them to the common origin I mentioned below. 

So I restate my position. What is the physics by which the two clocks can be synchronized when their distance and velocities are unknown? That is obvious when they are synchronized at a common origin point or with respect to a common third party of known speed and distance from each. Then there is no paradox as I mentioned below. SRT and Doppler calculations will give the delay to the one that has moved the fastest with respect to the reference point when they next come close to each other. 

You are correct in that all motion is relative in SRT. But there is no absolute reference point in space. CMB does not give such a reference. That reference point will always be relative to the common point about which the two clocks were synchronized. Without such a common point the two clocks can’t be synchronized. Without synchronization the results of the observation are questionable. 

Cheers,

Vivian Robinson

On 23 August 2017 at 5:41:16 AM, Chip Akins (chipakins at gmail.com) wrote:

Hi Vivian

 I would like to return to a discussion briefly which was ensuing a couple of months ago.

Thank you for the careful explanation offered in the email below.

However the point I was attempting to make a couple of months ago, deals only with the concept that all motion is relative in SRT.

So let us set up an experiment which excludes all effects of GRT, acceleration, gravity etc. and only evaluates this notion of SRT that all motion is relative.

We have two identical clocks, moving relative to each other.

For the sake of this experiment, let us imagine that we have a means of synchronizing their clocks regardless of their separation. Or at least to start recording data at the same time, like when each reaches a predetermined distance from the other. (All Doppler effects accounted for.)

An observer with clock A thinks clock B is moving.

An observer with clock B thinks clock A is moving.

After the “relative” motion has occurred for some time, the two clocks pass by in very close proximity to each other and exchange their data.

 The observer with clock A assumes the reading from Clock B will indicate that time has passed more slowly for B than for A.  The observer with clock B assumes the reading from Clock A will indicate that time has passed more slowly for A than for B. Both cannot be correct.

Clearly because of this, there IS A PARADOX, and that paradox is undeniably embedded in the notion that all motion is relative. Bringing in arguments from other theories, and proclaiming that there is no paradox does not dismiss this logical problem inherent in SRT’s notion that all motion is relative.

If one clock is more stationary with regards to the CMB it is likely that is the one which will be more correct in their prediction of the clocks readings.

They cannot both be correct.

If they cannot both be correct, then all motion is NOT relative, but time is slowed for objects moving relative to space itself.

Chip

 

From: Viv Robinson [mailto:viv at universephysics.com]  
Sent: Wednesday, June 14, 2017 10:44 PM
To: Chip Akins <chipakins at gmail.com>; Nature of Light and Particles - General Discussion <general at lists.natureoflightandparticles.org>
Cc: 'Darren Eggenschwiler' <darren at makemeafilm.com>; 'Innes Morrison' <innes.morrison at cocoon.life>; 'Mark, Martin van der' <martin.van.der.mark at philips.com>
Subject: Re: [General] STR twin Paradox

 

Hi All,

The best way to sort out a problem is to understand the physics behind a situation and then use mathematics to calculate the magnitude of the physical effect attributed to it. Lets look at the so called "twin paradox".

Two observers O1 and O2 are next to and at rest with each other. Both have accurate atomic or whatever clocks. O2 is accelerated to speed v, travels for time t at v, is decelerated to rest wrt to O1, accelerated to v towards O1, again travels for a time and finally is decelerated to rest next to O1. They compare clocks. O2’s clock has slowed down wrt O1. Yet O2 has observed O1 traveling at v. So why doesn’t O1’s clock slow down wrt to O2?

The answer is the acceleration. To accelerate O2, a force is applied to it. The combination of force and distance adds energy to O2 that is not added to O1. That energy is added to O2 in terms of kinetic energy or momentum change. No matter how small is the energy that is added, it is split between mass and velocity and causes a time dilation. They are the special relativity theory (SRT) corrections. That is something that O2 experiences and O1 does not experience.

The fundamental difference that O2’s acceleration makes is that its mass increases as well as its velocity. Its time wrt O1  decreases. So while O2 may see O1 accelerating away, O1 is not the one experiencing the acceleration. Therefore O1 is not the observer whose mass is increasing and whose time is dilating. That is the physical reason why there is no "twin paradox". 

Time dilation due to acceleration and deceleration (calculable from gravity equivalence) appears to be cumulative. Acceleration effects may make a difference if O2 is rapidly accelerated to v and then immediately rapidly decelerated to rest wrt O1, followed by a rapid acceleration to v and an immediate deceleration to rest next to O1. O2 will show SRT time dilation effect equal to the integrated effect of its relativistic velocity wrt O1. Those interested could calculate the acceleration effect from gravity equivalence and see how they compare.

Apart from that the time delay O2 experiences is because of the velocity multiplied by time effect. When the time traveled is much longer than the acceleration time, the time delay experienced by O2 will, for all practical purposes, be due to the SRT correction. 

The above has described the physics of the so called “twin paradox”. There is no paradox. O2’s time slows relative to O1 because O2 is the one that has been accelerated. Einstein was correct on both situations, the relativistic time correction and that they are only experienced by the accelerated observer. 

Of course you are free to disagree with the above. However if you feel compelled to point out that it is wrong, it is best done by forwarding the physics that makes it wrong and then present the mathematics required to show the magnitude of the physical effect. Then show how it agrees with experimental observation. In doing that remember that experimentalist using accurate atomic clocks have many times verified the SRT time corrections. 

There are two ways by which the SRT corrections can be applied. One is that there is an absolute zero reference somewhere in space and all corrections are applied from it. The other is that the SRT corrections are a property of any particle moving wrt another. I have previously published some calculations that suggest that the rotating or toroidal photon model for the structure of matter is responsible for the SRT corrections of matter. With all sub atomic particles, proton, neutron electron and neutrino having a rotating or toroidal photon structure, the SRT corrections are automatically inbuilt into every particle. As such I am happy that Einstein’s SRT corrections will always apply. 

Remember that all linear motions are relative to the observer. However accelerations and circular motions are absolute. O1 and O2 may start out at 0.5 c wrt O3. O2 may be decelerated to rest wrt O3, remain at rest wrt O3 and then accelerated back to 0.5c to return to rest next to O1. O1 will still see O2’s clock as having lost time. O3 will see an entirely different situation. But remember O3 can only see what is happening to O1 and O2 by using photons. O3’s time dilation observations of O1 and O2 must include the SRT corrections as well as Doppler effect and distance changes. Complex but calculable to those interested.

Chip, regarding your analogy of A and B. At one stage in their life they were at the same place at the same time, even if it was only at birth. To find out which will be the younger you need to establish their background. If A remained at rest and B was accelerated away from A, B will be the younger when they both meet up again. If they both travelled away with equal accelerations, velocities and time they will both appear the same age. Both would be younger than a person born at the same place at the same time and remained at that place when they all met up again. 

I am quite happy to accept that all linear motion is relative. It agrees with SRT and experiment. I am also satisfied that the rotating or toroidal photon model for an electron (and other particles) gives a physical description that matches both SRT and observation. 

Cheers,

Vivian Robinson

On 15 June 2017 at 12:43:26 AM, Chip Akins (chipakins at gmail.com) wrote:

Hi John 


Yes.  When I used the large circle example, I was afraid that someone would divert the conversation from Special Relativity.  I suppose I deserve that. 


Back to Special Relativity.

 One Twin (Twin B) is moving at a constant highly relativistic velocity toward Twin A. Twin B thinks Twin A is moving, Twin A thinks Twin B is moving. When twin B arrives at Twin A’s location, Twin A expects Twin B to be younger, Twin B expects Twin A to be younger.  Mutually exclusive conditions (if all motion is relative). So all motion is not relative. Simple, even for post grads, like you and me.

I welcome constructive, logical, suggestions, but please refrain from condescension, it does not help the cause.

Chip


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.natureoflightandparticles.org/pipermail/general-natureoflightandparticles.org/attachments/20170823/c7126081/attachment.htm>