# Most general case of the Twin Paradox

556 views

### Edgar L. Owen

Sep 23, 2019, 6:39:53 PM9/23/19
to
Disregarding gravitation:

Twins A and B separate from any possible point in the universe, each take any separate path, then meet again at any possible location.

In general when they meet their clocks will read different elapsed proper times.

Is it true that in all possible cases each twin's elapsed proper time will be equal to the sum of its Lorentz time dilation due to its velocity RELATIVE to the eventual meeting point? Where the Lorentz time dilation is of their own proper time RELATIVE to a clock at the eventual meeting point (i.e. the coordinate time of their clock as measured relative to a clock at the eventual meeting point)?

If not what is the simple rule that determines the difference in proper times in the most general case above?

Thanks,
Edgar

### JanPB

Sep 23, 2019, 8:07:01 PM9/23/19
to
On Monday, September 23, 2019 at 3:39:53 PM UTC-7, Edgar L. Owen wrote:
> Disregarding gravitation:
>
> Twins A and B separate from any possible point in the universe, each take any separate path, then meet again at any possible location.
>
> In general when they meet their clocks will read different elapsed proper times.
>
> Is it true that in all possible cases each twin's elapsed proper time will be equal to the sum of its Lorentz time dilation due to its velocity RELATIVE to the eventual meeting point? Where the Lorentz time dilation is of their own proper time RELATIVE to a clock at the eventual meeting point (i.e. the coordinate time of their clock as measured relative to a clock at the eventual meeting point)?

Yes. (Assuming I understand your question correctly.)

--
Jan

### rotchm

Sep 23, 2019, 8:56:25 PM9/23/19
to
On Monday, September 23, 2019 at 6:39:53 PM UTC-4, Edgar L. Owen wrote:
> Disregarding gravitation:

Ok

> Twins A and B separate from any possible point in the universe,

Simpler said: B leaves A.
Or, A & B initially coincide.

> each take any separate path, then meet again at any possible location.

Or, they coincide again.

> In general when they meet their clocks will read different
> elapsed proper times.

Yes. Or simpler: Their values generally differ.

> Is it true that in all possible cases each twin's elapsed proper
> time will be equal to the sum of its Lorentz time dilation due to its
> velocity RELATIVE to the eventual meeting point?

No, because a velocity wrt a "point" makes no sense. A velocity is wrt a reference frame, a coordinate system, and preferably, an inertial one (since poisint & time 7 thus velocity has a well given definition).

You meant that their elapsed proper time will be equal to the
sum of its Lorentz time dilation due to its
velocity RELATIVE to any chosen inertial frame.

>Where the Lorentz time dilation is of their own proper time RELATIVE
> to a clock at the eventual meeting point

Their end values will be their end values, just as the clock at their meeting point. All three clocks will have *values* as they all coincide.

> (i.e. the coordinate time of their clock

That doesn't quite make any sense. "the value of their clock" is what you meant?

usually we talk of 'coordinate time' wrt an inertial frame, not a of a clock.

> as measured relative to a clock at the eventual meeting point)?
>
> If not what is the simple rule that determines the difference in
> proper times in the most general case above?

Given any inertial frame F, one can describe the trajectory x(t) of any "traveling clock". You can find the value of this/these clocks(or any where else in the F frame) by using the "summation of the TD"; by
evaluating ∫√( 1 + b²)dt where b = d(x(t))/dt where x(t) is the trajectory
of the clock as described by F.

### Edgar L. Owen

Sep 23, 2019, 11:02:43 PM9/23/19
to
OK, now here's what I don't understand. To me it seems that the different elapsed proper times when the twins compare clocks upon meeting is clearly something actual since both twins agree on it. Both proper time rates are now the same. The elapsed disparity is not due to coordinate times. That seems in clear contradiction to Tom and rotchm claiming 'clocks always run at the same rate'. For the two clocks to show different elapsed times they can only have been running at different proper time rates during their separation. That's problem 1.

But problem 2. is how could motion wrt a meeting point which may not yet even have been determined possibly determine the actual proper time rates of the twin's clocks during their separation before their meeting? That just doesn't make sense to me.

It seems clear the clocks must be running at different actual rates during their separation whose cumulative result is the disparity upon meeting. Therefore it must be due to actual motion wrt something common to both twins.

Intuitively the only explanation that makes sense to me to explain the clearly actual proper time disparity would be that it's due to motion wrt some absolute frame (aggregate mass of universe) rather than motion wrt some arbitrary meeting point somehow controlling how their proper times varied during their separation.

Thoughts?
Edgar

### rotchm

Sep 23, 2019, 11:23:58 PM9/23/19
to
On Monday, September 23, 2019 at 11:02:43 PM UTC-4, Edgar L. Owen wrote:

> ...the twins compare clocks upon meeting is clearly something
> actual since both twins agree on it.

Yes.

> That seems in clear contradiction to Tom and rotchm claiming
> 'clocks always run at the same rate'.

This is where I see that you are a dishonest hypocrite.
I asked you a simple question relating to this concept and you have refused to answer. Why?

Here it is again: You buy two el-cheapo watches at the dollar store.
You set them at the same time, one on each arm. Some time later,
the Left one indicates 2:23pm and the other 2:31.
Which one ticked faster? Slower?

### Engr. Ravi

Sep 24, 2019, 4:05:35 AM9/24/19
to
On Tuesday, September 24, 2019 at 8:53:58 AM UTC+5:30, rotchm wrote:
> Here it is again: You buy two el-cheapo watches at the dollar store.
> You set them at the same time, one on each arm. Some time later,
> the Left one indicates 2:23pm and the other 2:31.
> Which one ticked faster? Slower?

Simple. Check them both w.r.t GPS atomic clocks.

### Engr. Ravi

Sep 24, 2019, 4:08:46 AM9/24/19
to
On Tuesday, September 24, 2019 at 8:32:43 AM UTC+5:30, Edgar L. Owen wrote:
> OK, now here's what I don't understand. To me it seems that the different elapsed proper times when the twins compare clocks upon meeting is clearly something actual since both twins agree on it. Both proper time rates are now the same. The elapsed disparity is not due to coordinate times. That seems in clear contradiction to Tom and rotchm claiming 'clocks always run at the same rate'. For the two clocks to show different elapsed times they can only have been running at different proper time rates during their separation. That's problem 1.
>
> It seems clear the clocks must be running at different actual rates during their separation whose cumulative result is the disparity upon meeting. Therefore it must be due to actual motion wrt something common to both twins.
>

For the two clocks to show different elapsed times they can only have been running at different proper time rates during their separation. It seems clear the clocks must be running at different actual rates during their separation whose cumulative result is the disparity upon meeting.

+1 Amen!

### maluw...@gmail.com

Sep 24, 2019, 4:17:37 AM9/24/19
to
On Tuesday, 24 September 2019 05:23:58 UTC+2, rotchm wrote:

> Here it is again: You buy two el-cheapo watches at the dollar store.
> You set them at the same time, one on each arm. Some time later,
> the Left one indicates 2:23pm and the other 2:31.
> Which one ticked faster? Slower?

For a sane guy it's obvious, the one of 2:31 has
ticked faster (assuming none of them was reset).
But you're a fanatic idiot following some mystical
bullshit; heavens only know what answer you'll
announce as the correct one.

### maluw...@gmail.com

Sep 24, 2019, 4:19:48 AM9/24/19
to
On Tuesday, 24 September 2019 10:08:46 UTC+2, Engr. Ravi wrote:
> On Tuesday, September 24, 2019 at 8:32:43 AM UTC+5:30, Edgar L. Owen wrote:
> > OK, now here's what I don't understand. To me it seems that the different elapsed proper times when the twins compare clocks upon meeting is clearly something actual since both twins agree on it. Both proper time rates are now the same. The elapsed disparity is not due to coordinate times. That seems in clear contradiction to Tom and rotchm claiming 'clocks always run at the same rate'. For the two clocks to show different elapsed times they can only have been running at different proper time rates during their separation. That's problem 1.
> >
> > It seems clear the clocks must be running at different actual rates during their separation whose cumulative result is the disparity upon meeting. Therefore it must be due to actual motion wrt something common to both twins.
> >
>
> For the two clocks to show different elapsed times they can only have been running at different proper time rates during their separation.

Man, get conscious. Take a look around you.
I'm sure you'll find some clocks with
different elepsed times without any
separation.

### Engr. Ravi

Sep 24, 2019, 5:08:35 AM9/24/19
to
On Tuesday, September 24, 2019 at 1:49:48 PM UTC+5:30, maluw...@gmail.com wrote:
> Man, get conscious. Take a look around you.
> I'm sure you'll find some clocks with
> different elepsed times without any
> separation.

@maluw

A skeptic should be open to the possibility that the theory he is skeptical about, could after all be correct.

IF the experiment described in this post:

gives a NON-NULL result, in particular IF it turns out that:

[(B_end - A_0) - (M_end - M_0)] is NOT normally distributed with zero mean,

(B_end - A_0) ≈ γ(M_end - M_0),

even after a thorough verification, clocks are not defective, battery packs are reliable, no confounding effects, etc., THEN, it is very likely that STR is actually correct.

However, as Tom himself has admitted, the experiment described has never been conducted, since it has been estimated that for attainable velocities, the "systemic errors would great outweigh the predicted effect".

Tom instead lists FIVE other experiments which we are supposed to take as equivalent to the described experiment:

Of these,
- Hafele & Keating is useless as it has too much variance and unfavorable results were omitted.
- gravity probe A is yet another frequency-shift experiment or a test of "time-dilation".
- the two experiments with muon's are unsatisfactory, since we do not know for sure if the muon disintegration mechanism is equivalent to a countdown timer.

So we are down to just ONE. If this is also carefully checked, it is highly likely there will be flaws.

=====================
C. Alley, “Proper Time Experiments in Gravitational Fields with Atomic Clocks, Aircraft, and Laser Light Pulses,” in Quantum Optics, Experimental Gravity, and Measurement Theory, eds. Pierre Meystre and Marlan O. Scully, Proceedings Conf. Bad Windsheim 1981, 1983 Plenum Press New York, ISBN 0-306-41354-X, pg 363–427.

They flew atomic clocks in airplanes that remained localized over Chesapeake Bay, and also which flew to Greenland and back.
=====================

### Odd Bodkin

Sep 24, 2019, 6:50:10 AM9/24/19
to
Edgar L. Owen <elot...@gmail.com> wrote:
> OK, now here's what I don't understand. To me it seems that the different
> elapsed proper times when the twins compare clocks upon meeting is
> clearly something actual since both twins agree on it. Both proper time
> rates are now the same. The elapsed disparity is not due to coordinate
> times. That seems in clear contradiction to Tom and rotchm claiming
> 'clocks always run at the same rate'. For the two clocks to show
> different elapsed times they can only have been running at different
> proper time rates during their separation.

No, that’s where you are forcing a false dichotomy. There’s a third option.

> That's problem 1.
>
> But problem 2. is how could motion wrt a meeting point which may not yet
> even have been determined possibly determine the actual proper time rates
> of the twin's clocks during their separation before their meeting? That
> just doesn't make sense to me.

Because it’s not the meeting POINT that matters but the frame of reference
in which the meeting point is at rest that matters.

>
> It seems clear the clocks must be running at different actual rates
> during their separation whose cumulative result is the disparity upon
> meeting. Therefore it must be due to actual motion wrt something common to both twins.
>
> Intuitively the only explanation that makes sense to me to explain the
> clearly actual proper time disparity would be that it's due to motion wrt
> some absolute frame (aggregate mass of universe) rather than motion wrt
> some arbitrary meeting point somehow controlling how their proper times
> varied during their separation.
>
> Thoughts?
> Edgar
>

--
Odd Bodkin -- maker of fine toys, tools, tables

### Odd Bodkin

Sep 24, 2019, 6:50:11 AM9/24/19
to
At rest in which frame?

### Odd Bodkin

Sep 24, 2019, 6:50:11 AM9/24/19
to
Engr. Ravi <ravic...@gmail.com> wrote:
> On Tuesday, September 24, 2019 at 8:32:43 AM UTC+5:30, Edgar L. Owen wrote:
>> OK, now here's what I don't understand. To me it seems that the
>> different elapsed proper times when the twins compare clocks upon
>> meeting is clearly something actual since both twins agree on it. Both
>> proper time rates are now the same. The elapsed disparity is not due to
>> coordinate times. That seems in clear contradiction to Tom and rotchm
>> claiming 'clocks always run at the same rate'. For the two clocks to
>> show different elapsed times they can only have been running at
>> different proper time rates during their separation. That's problem 1.
>>
>> It seems clear the clocks must be running at different actual rates
>> during their separation whose cumulative result is the disparity upon
>> meeting. Therefore it must be due to actual motion wrt something common to both twins.
>>
>
> For the two clocks to show different elapsed times they can only have
> been running at different proper time rates during their separation.

False dichotomy. There’s a third option.

> It seems clear the clocks must be running at different actual rates
> during their separation whose cumulative result is the disparity upon meeting.
>
> +1 Amen!
>

### Engr. Ravi

Sep 24, 2019, 6:56:26 AM9/24/19
to
On Tuesday, September 24, 2019 at 4:20:11 PM UTC+5:30, Odd Bodkin wrote:
> > For the two clocks to show different elapsed times they can only have
> > been running at different proper time rates during their separation.
> > It seems clear the clocks must be running at different actual rates
> > during their separation whose cumulative result is the disparity upon meeting.

> False dichotomy. There’s a third option.

3rd option, which is ???

### maluw...@gmail.com

Sep 24, 2019, 7:10:48 AM9/24/19
to
Being in denial.

### Python

Sep 24, 2019, 7:43:16 AM9/24/19
to
Something you are very familiar with, aren't you Mr FRAUD Wozniak?

### maluw...@gmail.com

Sep 24, 2019, 8:02:13 AM9/24/19
to
Yes, poor halfbrain, I am very familiar with

### Python

Sep 24, 2019, 9:06:40 AM9/24/19
to
Like biologists in denial of creationism, M.D. in denial of homeopathy,
climatologists in denial of oil company propaganda. Sure, Mr FRAUD
Wozniak.

### maluw...@gmail.com

Sep 24, 2019, 9:11:45 AM9/24/19
to
No. Like insane fanatic cultists denying
common sense.

### Python

Sep 24, 2019, 9:36:25 AM9/24/19
to
What does common sense say about the likelihood of two people (or more)
sharing the same birthday date in a class of twenty people?

### rotchm

Sep 24, 2019, 9:55:29 AM9/24/19
to
On Tuesday, September 24, 2019 at 9:36:25 AM UTC-4, Python wrote:

> What does common sense say about the likelihood of two people (or more)
> sharing the same birthday date in a class of twenty people?

My gut feeling tells me a little less that 50%.
So my gut feeling is somewhere between 40% & 49%.

### Odd Bodkin

Sep 24, 2019, 10:44:02 AM9/24/19
to
There are many ways to explain it, for which ample reading in textbooks
helps. Geroch’s book on General Relativity from A to B is good as a start.

One way to explain it is that time is not a feature of the physical object,
ie the clock. Rather, the behavior of clocks (and in fact all objects) is
governed by the structure of spacetime. It is a habit of amateurs and
engineers steeped in classical physics to consider space and time to be
passive backgrounds in which physical things happen but which are not
active players in those processes. Where this prejudice comes from, I’m not
sure. Maybe it’s due to a related bias that only material things have
physical properties, which is also not true.

There are a number of arguments one can make to shake those prejudices
loose. One simple one is to note simply that time dilation affects all
processes exactly equally, no matter what the underlying physics of those
various processes are. It therefore can have nothing to do with the details
of how those devices or processes work.

Another one that seems difficult to absorb is that pairs of clocks
synchronized in one frame are not synchronized in any other relatively
moving frame, by any common synchronization test applied in both frames.
The immediate question an amateur is tempted to ask is, what happened to
those two clocks to throw them out of synch in the second synch test? The
answer is “nothing” because if you retest them in the original frame,
they’re still synched. This actually has more to do with time dilation and
length contraction than it first appears.

The usual reaction by the amateurs and engineers steeped in classical
physics to the concept of spacetime having a structure is to ask, what is
the mechanism by which that structure affects processes? This again
heartens back to the (unjustified) bias that this is a cogs-and-wheels
universe with material things effecting changes in other material things.
That is in fact off the mark. Physics aims to understand rules, not
cogs-and-wheels processes. As an example, it’s widely accepted that
momentum is conserved in closed systems (or in systems sufficiently close
to closed that the experimental difference is negligible). However, you’re
never going to find a process or mechanism for WHY momentum is conserved.
Momentum isn’t a “stuff”, for example, and so this can’t be shuffled off to
some “stuff is conserved” notion. Note that physicists are aware that
(thanks to Emmy Noether) momentum conservation has to do with a particular
symmetry of physical laws. But symmetry isn’t a mechanism, and physical
laws are not material things.

So abandoning some of the prejudices that corner you into making false
dichotomies is key here. Those prejudices do not work in physics and in
fact do not apply to physics, and attempts to reinstall them will only lead
to the barriers you are encountering.

--
Odd Bodkin — Maker of fine toys, tools, tables

### kenseto

Sep 24, 2019, 11:56:37 AM9/24/19
to
On Monday, September 23, 2019 at 11:02:43 PM UTC-4, Edgar L. Owen wrote:
> OK, now here's what I don't understand. To me it seems that the different elapsed proper times when the twins compare clocks upon meeting is clearly something actual since both twins agree on it. Both proper time rates are now the same. The elapsed disparity is not due to coordinate times. That seems in clear contradiction to Tom and rotchm claiming 'clocks always run at the same rate'. For the two clocks to show different elapsed times they can only have been running at different proper time rates during their >separation. That’s problem 1.

The problem is that Einstein rejected the notion of absolute time. In doing so he embraced the notion that a clock second is a universal interval of time (absolute time).....it is not. Tom and Rotchm accept Einstein’s false notion of time that a clock second is a universal interval of time and that’s why they said that ‘clocks always run at the same rate’. This creates your confusion.

In real life:
1. Absolute time exists. The rate of passage of absolute time is the same in all frames. This means that your twin will passed the same amount of absolute time between meetings.
2. But there is no clock time unit (including a clock second) that represents the same amount of absolute time in different frames. A clock second will represent a different amount of absolute time in different frames or in different gravitational potential.
3. This means that each twin will experience the same amount of absolute time between meetings. However, in terms of clock time: the clock that has a higher state of absolute motion or in lower gravitational potential will accumulate clock seconds at a slower rate.

4. I invite you to read the above concept time in the following link:
http://www.modelmechanics.org/2015irt.pdf
http://www.modelmechanics.org/2016ibook.pdf

### Pálek Slovù

Sep 24, 2019, 12:22:23 PM9/24/19
to
JanPB wrote:

>> Is it true that in all possible cases each twin's elapsed proper time
>> will be equal to the sum of its Lorentz time dilation due to its
>> velocity RELATIVE to the eventual meeting point? Where the Lorentz time
>> dilation is of their own proper time RELATIVE to a clock at the
>> eventual meeting point (i.e. the coordinate time of their clock as
>> measured relative to a clock at the eventual meeting point)?
>
> Yes. (Assuming I understand your question correctly.)

We never know. You could also be just guessing, with a fifty-fifty chance.

### Odd Bodkin

Sep 24, 2019, 12:32:01 PM9/24/19
to
It never ceases to amaze me that people like Ed Lake, Ken Seto, Ned Latham,
the subject matter of this group — aside from some news items on the
internet, Usenet posts, and maybe a high school book — and still think that
their opinions, thoughts, and ideas should be treated on the same level
playing field as those by others who have more seriously studied the
subject. It’s arrogance of the highest order.

I will say it again. If any if the following is true:

— You don’t know the meaning of terms used in physics, and are content to
either substitute colloquial meanings as found in the dictionary or just
GUESS what you think they mean,

— You don’t have the prerequisite math skills to follow physics
presentations or to generate numerical consequences of other people’s idea

— You are unaware of the corpus of experimental data that has been gathered
to test various physics ideas, and you have no idea how to find them to

— You have not bothered to read textbook presentations of the material,
because you find it frustrating or it takes too long or it costs money or
you can’t make head nor tail of it,

If any of the above are true, then you simply don’t know enough about the
subject to discuss it intelligently. And any attempt on your part to
discuss it ANYWAY (because you crave the attention) is a waste of your
time, and the only outcome is that you will cement a reputation for idiocy.

### Engr. Ravi

Sep 24, 2019, 1:14:28 PM9/24/19
to
On Tuesday, September 24, 2019 at 8:14:02 PM UTC+5:30, Odd Bodkin wrote:
>

Appreciate your effort to provide a deeper understanding.

> One way to explain it is that time is not a feature of the physical object,
> ie the clock. Rather, the behavior of clocks (and in fact all objects) is
> governed by the structure of spacetime. It is a habit of amateurs and
> engineers steeped in classical physics to consider space and time to be
> passive backgrounds in which physical things happen but which are not
> active players in those processes. Where this prejudice comes from, I’m not
> sure. Maybe it’s due to a related bias that only material things have
> physical properties, which is also not true.

spacetime is a concept that is being scheduled for retirement, for totally different reasons, by many physicists at the vanguard of physics.

> There are a number of arguments one can make to shake those prejudices
> loose. One simple one is to note simply that time dilation affects all
> processes exactly equally, no matter what the underlying physics of those
> various processes are. It therefore can have nothing to do with the details
> of how those devices or processes work.

This is required by the principle of relativity. If time dilation is real, then it must affect all mechanisms in the same proportion regardless of their individual intricate processes. However, the far more simpler argument, again from the principle of relativity, is there is no real time dilation [this is consistent with experiment], so no mechanism is affected in any way by mere uniform motion, when viewed from the frame it is in rest. Of course when the mechanism has to be viewed from a frame in which it is moving, this requires using signals, which can and will be affected by the motion.

Our understanding of physics becomes deeper if we can figure out the mechanism behind real time dilation [if it exists]. When it was first proposed, both Lorentz and Fitzgerald attempted to give a mechanism of action using the aether theory.

> Another one that seems difficult to absorb is that pairs of clocks
> synchronized in one frame are not synchronized in any other relatively
> moving frame, by any common synchronization test applied in both frames.
> The immediate question an amateur is tempted to ask is, what happened to
> those two clocks to throw them out of synch in the second synch test? The
> answer is “nothing” because if you retest them in the original frame,
> they’re still synched. This actually has more to do with time dilation and
> length contraction than it first appears.

Ok, this is the relativity of simultaneity, a corner stone for STR, and Einstein's aha moment.

> The usual reaction by the amateurs and engineers steeped in classical
> physics to the concept of spacetime having a structure is to ask, what is
> the mechanism by which that structure affects processes? This again
> heartens back to the (unjustified) bias that this is a cogs-and-wheels
> universe with material things effecting changes in other material things.
> That is in fact off the mark. Physics aims to understand rules, not
> cogs-and-wheels processes. As an example, it’s widely accepted that
> momentum is conserved in closed systems (or in systems sufficiently close
> to closed that the experimental difference is negligible). However, you’re
> never going to find a process or mechanism for WHY momentum is conserved.
> Momentum isn’t a “stuff”, for example, and so this can’t be shuffled off to
> some “stuff is conserved” notion. Note that physicists are aware that
> (thanks to Emmy Noether) momentum conservation has to do with a particular
> symmetry of physical laws. But symmetry isn’t a mechanism, and physical
> laws are not material things.

Physics aims at both, what the rules are, and also why they are the way they are. Sometimes we can only achieve the former, and that leaves us dissatisfied.

The conservation of momentum is traced back to Newton's third law that all forces between particles are equal and opposite, i.e., they are symmetrical. For each individual force, people have tried to understand why this is so. For example, Le Sage's theory of gravitation explains this for gravity and any emission/ballistic theory of electromagnetism explains this for electrical and magnetic forces via mechanisms.

The wholesale acceptance of Einstein's STR was indeed the death of deeper understanding in physics. Just read Maxwell's papers and the attention he gave to mechanisms. THAT was real physics. Now, even someone like Feynman says visualizing something like the EM field is simply impossible.

> So abandoning some of the prejudices that corner you into making false
> dichotomies is key here. Those prejudices do not work in physics and in
> fact do not apply to physics, and attempts to reinstall them will only lead
> to the barriers you are encountering.

Tom's proposed experiment for verifying real time dilation is possibly the simplest possible. In that experiment if a NON-NULL result is obtained it is unavoidable to interpret the result as showing that the moving clocks actually ran differently. There is not much scope for a dicotomy here. A NULL result would however be the death of spacetime.

### Edgar L. Owen

Sep 24, 2019, 2:56:23 PM9/24/19
to

> Here it is again: You buy two el-cheapo watches at the dollar store.
> You set them at the same time, one on each arm. Some time later,
> the Left one indicates 2:23pm and the other 2:31.
> Which one ticked faster? Slower?

Rotchm,

This question is irrelevant. It has nothing to do with proper time always running at the same rate. It's just inaccurate mechanisms. I see no point to it.

Edgar

### Edgar L. Owen

Sep 24, 2019, 3:00:21 PM9/24/19
to
I agree its the frame of reference of the meeting point but don't see how that changes the conclusion.

Edgar

### Paul B. Andersen

Sep 24, 2019, 3:44:55 PM9/24/19
to
Den 24.09.2019 00.39, skrev Edgar L. Owen:
> Disregarding gravitation:
>
> Twins A and B separate from any possible point in the universe, each take any separate path, then meet again at any possible location.
>
> In general when they meet their clocks will read different elapsed proper times.
>
> Is it true that in all possible cases each twin's elapsed proper time will be equal to the sum of its Lorentz time dilation due to its velocity RELATIVE to the eventual meeting point? Where the Lorentz time dilation is of their own proper time RELATIVE to a clock at the eventual meeting point (i.e. the coordinate time of their clock as measured relative to a clock at the eventual meeting point)?
>
> If not what is the simple rule that determines the difference in proper times in the most general case above?
>
> Thanks,
> Edgar
>

See:

https://paulba.no/pdf/TwinsByMetric.pdf

--
Paul

https://paulba.no/

### kenseto

Sep 24, 2019, 4:18:00 PM9/24/19
to
Physicists have studied all that had been written for the last 110 years and they failed to come up with a unified theory. This mean that current physics is wrong or incomplete. It’s time for new physics like Model Mechanics that includes a valid unified theory and a new theory of gravity.

### rotchm

Sep 24, 2019, 4:34:17 PM9/24/19
to
On Tuesday, September 24, 2019 at 2:56:23 PM UTC-4, Edgar L. Owen wrote:
> > Here it is again: You buy two el-cheapo watches at the dollar store.
> > You set them at the same time, one on each arm. Some time later,
> > the Left one indicates 2:23pm and the other 2:31 pm.
> > Which one ticked faster? Slower?
>
> Rotchm,
>
> This question is irrelevant.

No it is not irrelevant. Its that you just dont see it. Try to think about it. Try to answer it.

> It has nothing to do with proper time always running at the same rate.

Yes it does.

> It's just inaccurate mechanisms.

Really? Think a little harder.

> I see no point to it.

As you dont see the 'simplicity' of SR, the simplicity of what confuses you, hence all your naive questions.

### maluw...@gmail.com

Sep 24, 2019, 5:05:56 PM9/24/19
to
It says that if you want to know you shold calculate it.

### Tom Roberts

Sep 24, 2019, 6:03:51 PM9/24/19
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On 9/23/19 5:39 PM, Edgar L. Owen wrote:
> Disregarding gravitation:
>
> Twins A and B separate from any possible point in the universe, each
> take any separate path, then meet again at any possible location.
>
> In general when they meet their clocks will read different elapsed
> proper times.
>
> Is it true that in all possible cases each twin's elapsed proper time
> will be equal to the sum of its Lorentz time dilation due to its
> velocity RELATIVE to the eventual meeting point? Where the Lorentz
> time dilation is of their own proper time RELATIVE to a clock at the
> eventual meeting point (i.e. the coordinate time of their clock as
> measured relative to a clock at the eventual meeting point)?

This is true IF AND ONLY IF there exists an inertial frame in which the
clock at the eventual meeting point is always at rest, and that frame is
used to calculate all of the "time dilations".

Speed "relative to a point" is meaningless. Speed can only be measured
relative to some coordinate system, and is only simple if that
coordinate system is an inertial frame. So it makes no sense for a point
to be at rest in an inertial frame. But it does make sense for a clock.
So the "time dilations" are relative to that inertial frame of the
clock, not the eventual meeting point.

Tom Roberts

### Odd Bodkin

Sep 24, 2019, 6:08:46 PM9/24/19
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Engr. Ravi <ravic...@gmail.com> wrote:
> On Tuesday, September 24, 2019 at 8:14:02 PM UTC+5:30, Odd Bodkin wrote:
>>
>
> Appreciate your effort to provide a deeper understanding.
>
>> One way to explain it is that time is not a feature of the physical object,
>> ie the clock. Rather, the behavior of clocks (and in fact all objects) is
>> governed by the structure of spacetime. It is a habit of amateurs and
>> engineers steeped in classical physics to consider space and time to be
>> passive backgrounds in which physical things happen but which are not
>> active players in those processes. Where this prejudice comes from, I’m not
>> sure. Maybe it’s due to a related bias that only material things have
>> physical properties, which is also not true.
>
> spacetime is a concept that is being scheduled for retirement, for
> totally different reasons, by many physicists at the vanguard of physics.

Only in the same sense that Newtonian gravity has been “retired” by general
relativity or that Maxwell’s equations have been “retired” by quantum
physicists. They are not saying that spacetime was a mistake or a blind
alley. They are saying that an even deeper and almost certainly stranger
model will come to the fore, with spacetime being the effective limit when
some parameter in the new system is small.

>
>> There are a number of arguments one can make to shake those prejudices
>> loose. One simple one is to note simply that time dilation affects all
>> processes exactly equally, no matter what the underlying physics of those
>> various processes are. It therefore can have nothing to do with the details
>> of how those devices or processes work.
>
> This is required by the principle of relativity. If time dilation is
> real, then it must affect all mechanisms in the same proportion
> regardless of their individual intricate processes.

I’m not sure what you mean “required by relativity”. Relativity is not a
physics concept like Lorentz symmetry or spacetime with measurable
properties. In other words, I don’t think there’s more value in saying
“required by relativity” as opposed to “due to the structure of spacetime”.
At least with the latter, you can quantify and point to mathematically
expressed foundations for why.

> However, the far more simpler argument, again from the principle of
> relativity, is there is no real time dilation [this is consistent with
> experiment], so no mechanism is affected in any way by mere uniform
> motion, when viewed from the frame it is in rest. Of course when the
> mechanism has to be viewed from a frame in which it is moving, this
> requires using signals, which can and will be affected by the motion.

And again, I would dispute that “real” time dilation means changes or
affects physical mechanisms.

Let me put it to you this way. If I view a tree while standing on the
ground, the tree’s kinetic energy is zero. If I view the same tree from out
in space and watch the tree get dragged along with the earth’s surface
moving at 600 mph as the earth rotates, that tree now has a lot of kinetic
energy. Now ask yourself whether this difference is “real”. If the
conclusion is that it’s not real, is it the claim that only one of those
values is real? Or that kinetic energy itself is not real?

>
> Our understanding of physics becomes deeper if we can figure out the
> mechanism behind real time dilation [if it exists]. When it was first
> proposed, both Lorentz and Fitzgerald attempted to give a mechanism of
> action using the aether theory.

That’s correct. Note that they took the stance that electromagnetic
interactions accounted for ALL physical mechanisms, that there was one and
only one interaction responsible for all processes. We of course now know
that was a bad gamble. And since there is not one single interaction that
is responsible for all physical processes, then the “reality” of time
dilation must be attributable to something other than a common physical
interaction.

>
>> Another one that seems difficult to absorb is that pairs of clocks
>> synchronized in one frame are not synchronized in any other relatively
>> moving frame, by any common synchronization test applied in both frames.
>> The immediate question an amateur is tempted to ask is, what happened to
>> those two clocks to throw them out of synch in the second synch test? The
>> answer is “nothing” because if you retest them in the original frame,
>> they’re still synched. This actually has more to do with time dilation and
>> length contraction than it first appears.
>
> Ok, this is the relativity of simultaneity, a corner stone for STR, and
> Einstein's aha moment.

And the thing to understand is how relativity of simultaneity is at the
root of other stuff like length contraction. To see this, length has an
OPERATIONAL meaning. Can you figure out what that is? Let me ask how you
would measure the length of a car moving relative to you?

>
>> The usual reaction by the amateurs and engineers steeped in classical
>> physics to the concept of spacetime having a structure is to ask, what is
>> the mechanism by which that structure affects processes? This again
>> heartens back to the (unjustified) bias that this is a cogs-and-wheels
>> universe with material things effecting changes in other material things.
>> That is in fact off the mark. Physics aims to understand rules, not
>> cogs-and-wheels processes. As an example, it’s widely accepted that
>> momentum is conserved in closed systems (or in systems sufficiently close
>> to closed that the experimental difference is negligible). However, you’re
>> never going to find a process or mechanism for WHY momentum is conserved.
>> Momentum isn’t a “stuff”, for example, and so this can’t be shuffled off to
>> some “stuff is conserved” notion. Note that physicists are aware that
>> (thanks to Emmy Noether) momentum conservation has to do with a particular
>> symmetry of physical laws. But symmetry isn’t a mechanism, and physical
>> laws are not material things.
>
> Physics aims at both, what the rules are, and also why they are the way
> they are. Sometimes we can only achieve the former, and that leaves us dissatisfied.

The answer to the why is usually another rule, not a mechanism. It usually
has a broader scope and so is more fundamental than the prior rule. A good
example of this is that conservation of momentum is a rule that explains
both Newton’s first and third law. It is not a mechanism; it’s just a
deeper rule.

>
> The conservation of momentum is traced back to Newton's third law that
> all forces between particles are equal and opposite, i.e., they are
> symmetrical. For each individual force, people have tried to understand
> why this is so. For example, Le Sage's theory of gravitation explains
> this for gravity and any emission/ballistic theory of electromagnetism
> explains this for electrical and magnetic forces via mechanisms.

And it turns out that conservation of momentum comes from a symmetry:
spatial translational invariance of the laws of physics (Noether). This of
course does not answer why nature has this particular symmetry.

>
> The wholesale acceptance of Einstein's STR was indeed the death of deeper
> understanding in physics. Just read Maxwell's papers and the attention he
> gave to mechanisms. THAT was real physics. Now, even someone like Feynman
> says visualizing something like the EM field is simply impossible.
>

Again, physics has come a LONG way since 1875, the days when it was all
about material mechanisms. Particularly, in the last 70 years, there have
been several key, profound changes. A couple are:

1. That all material things and interactions have quantum fields as their
underlying reality.

2. That the nature of the interactions (quantum fields exchanging quantum
fields) is completely governed by local symmetries found in nature.

What I’ve described is what has been thought of as real physics for a half
dozen decades, even though it is much different than what you describe as
real physics.

>> So abandoning some of the prejudices that corner you into making false
>> dichotomies is key here. Those prejudices do not work in physics and in
>> fact do not apply to physics, and attempts to reinstall them will only lead
>> to the barriers you are encountering.
>
> Tom's proposed experiment for verifying real time dilation is possibly
> the simplest possible. In that experiment if a NON-NULL result is
> obtained it is unavoidable to interpret the result as showing that the
> moving clocks actually ran differently. There is not much scope for a
> dicotomy here. A NULL result would however be the death of spacetime.
>
>

### Odd Bodkin

Sep 24, 2019, 6:08:47 PM9/24/19
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Science never is finished. You view that as some kind of failure. That’s
perhaps because you don’t know what science is.

> This mean that current physics is wrong or incomplete.

No, not wrong.

Why do you think that unless science has come up with an answer for
everything then it is wrong?

> It’s time for new physics like Model Mechanics that includes a valid
> unified theory and a new theory of gravity.

Well I agree that it’s time for some new physics. Science never ends.

Unfortunately, you are incapable of generating the new physics because: you
don’t have the requisite skills to do physics, you don’t know the meaning
of the terms used in physics, and you’ve read nothing about physics.

You say that those things are not needed to do new physics, and that’s the
thought of a nut job.