Re: Twin paradox negation lll

On Oct 25, 12:36 pm, "harry" <harald.vanlintelButNotT...@xxxxxxx>
wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in message

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On Oct 24, 7:43 pm, "harry" <harald.NOTTHISvanlin...@xxxxxxx> wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in message

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On Oct 23, 6:05 pm, "harry" <harald.NOTTHISvanlin...@xxxxxxx> wrote:

The gist of 1916 GRT and his 1918 defence was that all motion is
"relative",
so that a gravitational field is fully equivalent to an acceleration;
consequently, Einstein stressed in 1916 that the gravitational field
that
the traveller experiences is not "fictitious" but as "real" as any
other
gravity. That is negated by the FAQ which calls those fields "pseudo"
fields. On top of that, the FAQ negates the fact the Twin paradox is
not
a
paradox of SRT, eventhough Einstein stressed this fact.

Apart from occasional references to the 1918 article my particular
interest lies in the first three paragraphs of Einstein's chapter 4
STR - specifically wherein he refers to a clock moving in a polygonal
line as does the out-and-return journey astronaut.

OK. That is not the Twin paradox but a similar scenario (of course,
that's
why these are often mixed up: it's the same problem in the context of
another theory which bears almost the same name).

I'm of the opinion that a polygonal trip can be directly applied to
'the twin paradox'. In lieu of starting some distance from B as per
Einstein's depiction clock A is located alongside, and is synchronous
with, B. A moves to X (a similar distance to Einstein's relocation of
A to B) and comes to a stop. It will then lag behind B by the same
amount as Einstein's clock A lagged behind clock B.

Clock A returns to clock B's location where it is found that it lags
behind B by twice that amount. It's an *identical* scenario.

Fine (that wasn't the point).

Thus the topic is of your discussion is, it seems, Einstein's 1905 SRT
time
dilation prediction and Langevin's similar example of two brothers, one
of
whom will age less; and not the paradox of one clock advancing over
another,
eventhough each is regarded as "always in rest".

Does your comment 'each is regarded as "always in rest"' apply to
Einstein's 1905 SRT time
dilation prediction

Only in the context of 1916 GRT.

specifically his chapter 4 depictions because as
far as I'm concerned in that chapter Einstein points out that it is
clock A that moves and B remains at rest.

Indeed. That's SRT.



In paragraph 3 Einstein refers to clock being made to move in a closed
curve around B "then by the clock *which has remained at rest* the
traveled clock will be slow."

The rate at which clock A 'goes more slowly' than B whilst A is
accelerating or decelerating could, I imagine, be determined
mathematically showing that Einstein's clock A will lag even further
behind a clock (initially located the same distance away from B) that
accelerates to B's location and is bought to a stop however this will
*not* invalidate the fact that A 'goes more slowly' (i.e. ticks over
at a slower rate) than B during that trip.

I'm not sure what you are saying there; with time dilation in SRT, two
things must be understood (not including effects from gravity):
1. Which clock is "really" going slower at a certain point in time cannot
be
determined, as the apparent difference depends on the reference one
chooses
(the PoR: absolute uniform motion cannot be determined).
2. What can be determined without ambiguity is that the clock that
*changes*
speed and returns goes slower on the average.

Apart from having momentarily come to a stop at the end of the outward
bound trip the clock that changes speed *continuously* goes slower
according to Einstein's chapter 4.

Indeed, that's also point no.2.

As pointed out above in relation to
the polygonal trip, clock A goes slower than B both on the outward
bound and the return journey.

Yes, that's all point no.2. How about your understanding of point no.1?

On the basis that an observer accompanying clock A is apparently
entitled to believe ("What can be determined without ambiguity....)
that his clock *is* going slower than it was before he changed speed
on the basis that he *has* changed speed then so too is the astronaut
entitled to be of the same opinion.

On the average yes - as I stated.

[...]

Indeed, the predictions of SRT are not in doubt. It is generally thought
that the "twin paradox" is simply due to a misunderstanding of SRT.

On the basis that the predictions of SRT specifically chapter 4 are
not in doubt then the claim that the astronaut, moving with uniform
velocity can be of the opinion that he *is* moving; that his clock
*is* ticking over at a slower rate than it was before he changed
speed.

According to SRT (and classical mechanics) we are free to choose any
inertial reference system we wish. For example, you can choose the solar
system as reference, so that you are now moving at high speed through space.

He accelerates away from what he considers is a 'stationary' reference
frame - the planet - and, having attained an instantaneous velocity of
near-light speed, takes his foot off the gas pedal but according to
some people he insists that he is at rest and that it is the entire,
infinite, universe which starts moving relatively to him at near-light
speed *instantaneously*.

Here you switch from the SRT clock calculation to 1916 GRT and the Twin
paradox.

Knowing that this a sheer impossibility that does *not* conform with
the laws of physics he *could* sensibly realize that although there is
no internal dynamic experiment that he can conduct to determine if he
is moving with uniform velocity or is at rest he is entitled to
realize that he *is* moving away from the planet (Einstein's clocks B
- chapter 4) at near-light speed.

Sure.

I believe that *every* experiment that is claimed to ratify the
concept of time dilation has involved acceleration!

In order to obtain a speed difference one must of course at one point in
history have had an acceleration. However, the first direct test of time
dilation made use of the Doppler effect at constant speed:

http://en.wikipedia.org/wiki/Ives%E2%80%93Stilwell_experiment



Regards,
Harald

It is my understanding that the Doppler effect has *no* relationship
to relativistic time dilation.

Indeed: the measured "relativistic" Doppler effect is in fact the combined
effect of Doppler and time dilation - and that's how it was measured.

There were, I believe, two experts in the subject who staunchly denied
that the Ives-Stilwell experiment ratified SRT. Their names? Ives and
Stilwell.

That relates to a debate over words and philosophy and it has nothing to do
with predictions or measurements: they tried to demonstrate that time
dilation is "real", "contrary" to Einstein who held that time dilation is
"physical". As philosophy and debates over words is without end, I won't go
into that.

Instead I'll cite Ives: "The first suggestion as to a means by which this
postive effect may be observed experimentally came from Einstein and from
Ritz over thirty years ago, namely that the newly discovered Doppler effect
in canal rays involved velocities of the moving particles high enough to
show the expected effect."

It's a difficult experiment, but the essence is that of hydrogen atoms that
pass by at constant speed, the emission spectrum is measured and from that
the time dilation is calculated. This has nothing to do with the twin
paradox (point 2 above), but everything with time dilation (point 1 above).
Please bring up one topic at a time.

Best regards,
Harald

.

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