Re: Twin paradox revisited ll

On Jul 18, 8:13 am, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in messagenews:1184628075.621812.219120@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 16, 6:55 pm, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:
<cosmo...@xxxxxxxxxxxxxxx> wrote in messagenews:1184547408.260420.302940@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

What information can either person see, other than Doppler shift, that
causes them to believe that the other twin's clock is is ticking more
slowly? The idea that it is the inertial twin's clock that is ticking
more slowly contradicts Einstein's 1981 article.

Do you accept the contents of that article - that it is the clock (the
traveler's clock) that has experienced the force of acceleration as it
moves to the other clock's (the inertial twin's clock) location which
is the one that has incurred time dilation?

Over the total return journey the traveller ages less but during the
cruise phase each twin measures the other's clock to be running
more slowly.

In other words you do *not* accept the contents of Einstein's 1918
article that it is *only* the clock that has experienced acceleration
which is the one that physically ticks over at the slower rate.

If somebody accepts that suggestion then they must conclude that what
the traveler 'measures' or 'observes' or 'determines' is nothing more
than a visual illusion on the basis that Einstein insisted that the
'other' clock (i.e. the earth clock) does *not* incur time dilation.

Why won't you answer the question instead of simply rehashing old
clichés? In your opinion, in his 1918 article *did* Einstein suggest
that the clock that does *not* experience the force of acceleration
*also* incurs time dilation?

Einstein's article was an attempt to *solve* the twin paradox i.e. the
concept that 'each twin measures the other's clock to be running more
slowly'.

There are two things which affect the frequency of the received
light signal: the standard Doppler shift and relativistic time
dilation (the combined effect is generally known as the relativistic
Doppler effect). An observer sees both effects but can allow for
the normal Doppler effect (which was understood well before
relativity and is therefore not important in this context). When
the normal Doppler effect is allowed for, time dilation is observed.

According to Einstein's article, the clock that has *not* experienced
the force of acceleration is *not* ticking over at a slower rate than
the one that *has* so if the traveler 'measures' that the other *is*
incurring time dilation he must be receiving false data.

As Einstein showed in his train gedanken using two flashes of
lightning however, as I pointed out in one of my postings in the 90s,
the train passenger and the stationary observer (as well as numerous
other observers in separate reference frames) can agree on
simultaneity determined by the passenger's location at the instant
that the flashes take place.

I am happy to discuss the train experiment if you wish.

We are having enough trouble discussing the subject on hand without
introducing extemporaneous material.

As per above, on what other information does the traveler conclude
that the inertial twin is aging at the slower rate? I repeat, in his
1918 article Einstein insisted that it is the traveler that is aging
at the slower rate so any argument that insists otherwise is
suggesting that Einstein was wrong in that article.

Over the return journey traveller ages less. As stated above
during the cruise phase each twin can use the light frequency
to calculate that the other's clock is running slower, after
they have allowed for the Doppler effect.

See information stated above.

Einstein pointed out in his 1918 article that it is the clock (or
twin) that physically experiences the force of acceleration which is
the one that incurs time dilation however our intrepid traveler,
having experienced that force of acceleration, pointedly ignores
Einstein's suggestion and insists that it is the earth, and the rest
of the universe, that is now moving relatively to him.

Yes, during the cruise phase but not during the turn around.
Acceleration is not relative.

Not according to some of the people responding to this discussion.
They insist that as the traveler blasts off from the launch pad or
accelerates following turn around he is of the opinion that it is the
universe that is accelerating and he is 'at rest' and it is this
solipsist nonsense, along with your suggestion that the traveler,
during the cruise phase when he can see the universe rushing past him,
insists that he is stationary and it is the universe that is moving
relatively to him, that I am attempting to resolve.

On the basis that, according to the traveler, it is the universe that
is moving past him compared to when he bought his ship to a stop prior
to turn around he must also realise that this relative velocity was
*not* instantaneous - that the universe *must* have incurred
acceleration in order to bring about this difference in its velocity
relative to him.

The traveler can only assume that a force that is greater than the
infinite mass of the universe has caused it to start accelerating.

No response?

Acceleration is not relative, the traveller accelerates, the other twin
does not.

Agreed, but for the traveler during the cruise phase to be of the
opinion that he is at rest and that it is the universe that is now
moving relatively to him he must, I repeat, be of the opinion that it
underwent acceleration in order to take it from when it was 'at rest'
relatively to him prior to his accelerating the ship to its now near
light speed rate of travel.

As you point out - the traveler accelerates, the other twin does not
and on the basis that the traveler is aware of Einstein's 1918
argument he must, assuming that he agrees with Einstein, be of the
opinion that his is the clock that has *experienced* a force of
acceleration thus that, as Einstein insisted, *his* is the moving
clock and as such, regardless of what he 'sees' or 'measures' or
'determines' that it must be *his* clock that is physically ticking
over at a slower rate than the earth clock.

No, during the cruise phase, in both directions, the traveller will
determine the Earth to be orbiting the sun at a rate of less than
once per year.

If he is travelling away from the earth at a velocity whereby each of
his seconds is equal to 30,000 seconds earth time he must surely, in
accordance with your arguments, be able to *determine* this 'fact'?

On the basis that what he *determines* is, from his point of view,
reality then surely he must 'see' or 'determine' or 'measure' his
twin's clock to be ticking over at the rate of 30,000 seconds for each
of his own seconds?

In one of his days - 30,000 days have elapsed on earth thus the
planet's rate of spin, from his point of view - in accordance with his
determination - has increased from 1,600K-h to (an SR verbotten) 48
*million* K-h.

Similarly he must 'determine' that for each of his own years the earth
clocks have registered a total of 30,000 years?

In a single year of his time he must 'determine' that 30,000 years
have elapsed on earth and for this to take place the earth must be
orbiting the sun at around 900,000K-s.

You suggest that, during the outward bound trip, 'the traveler will
determine the Earth to be orbiting the sun at a rate of less than once
per year'. Presumably you mean one of his years.

How can he 'see' or 'determine' that 30,000 earth years elapse for
each of his own years if he *also* determines that the earth is
orbiting the sun at a velocity whereby an earth year is *longer* than
one of his own years?

What experimental evidence, other than that dealing with the Doppler
effect, shows that the inertial twin will determine that the traveler
is alternately aging at a slower then faster rate than he is?

I know you are aware of the Hafele and Keating experiment. Clocks
are now more accurate and I understand that observation of time
dilation is now commonplace.

The HKX showed, from the point of view of an observer located in the
laboratory in Washington, that during the first leg of the experiment
- when the clocks were being made to travel in the same direction as
the earth's axial spin - that they, compared to his clocks, incurred
time dilation and during the second leg that those clocks incurred
time 'contraction' - ticking over at a faster rate than his clocks.

In other words, the 'inertial' twin found that Hafele and Keating
alternately aged at slower then faster rates than himself due to the
fact that the traveling clocks were alternately moving at faster then
slower speeds than the laboratory clocks - and himself.

Unless you are referring to rates of travel wrt a Newtonian universal
rest, which I very doubt that you are, this is *not* analogous to an
out and return journey where the traveler is moving at identical
velocities in both directions relatively to a stationary observer.

The only way that the inertial twin can determine faster or slower
rates of aging *for the traveler* is if the latter moves at different
velocities during each of the trips however he *cannot* determine, as
did the Washington observer, that the traveler is aging at a *faster*
rate than himself. But I think you are aware of that fact.

You can see all the experimental evidence for SR on the FAQ.

It is, I understand, a primary tenet of physics that although a theory
may appear to have been ratified by numerous experiments it only takes
one experiment to invalidate *any* theory.


Bill

.

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