Re: Twin paradox revisited ll

"bill" <cosmosco@xxxxxxxxxxxxxxx> wrote in message
news:1185067492.713084.100350@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 18, 8:13 am, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:
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.

They may be other words .. bnut they are not what he just said

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.

No .. its not a visual illusion

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 is no paradox

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.

Both clocks tick at the correct rate .. but in A's frame of reference, B's
clock is slower and in B's frame of reference, A's clock is slower.

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.

Its a simpler case .. you have to understand that before you can move onto
the more complex twins paradox

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.

Everyone here has said the acceleratiomn is not relative

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'

No

and it is this solipsist nonsense

Like yours?

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 is an equally correct view.

that I am attempting to resolve.

There is nothing to resolve. If A is moving away from B,. then B is moving
away from A

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.

What he 'realises' is unrealted to the physics. The twin 'paradox' has
nothing to do with what the twins realise .. or even if they are conscious
... or even if they are human .. or even if they are alive.

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.

His opinions is irrelevant to the physcis.

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.

The physics of the situation doesn't change based on whether the traveller
is aware of Einstein's paper.

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'?

Whether or not he can determine it is irrelevant. Its whether or not it is
true

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?

No .. when not accelerated, he would see his twin's clock ticking at 1
second for 30,000 of his.

In one of his days - 30,000 days have elapsed on earth thus the
planet's rate of spin,

No .. the other way around (we are talking about the cruising part of the
triup here)

from his point of view - in accordance with his
determination - has increased from 1,600K-h to (an SR verbotten) 48
*million* K-h.

No .. it has slowed dramatically (we are talking about the cruising part of
the triup here)


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

No .. the other way around (we are talking about the cruising part of the
triup here)

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.

No .. the other way around (we are talking about the cruising part of the
triup here)

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.

No .. the other way around (we are talking about the cruising part of the
triup here) .. he would observe the earth slowing down and taking longer to
orbit.

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?

The problem here is that during the cruise both twin's clocks are slow
relative to the other. It is symmetric. During the acceleration phase,
things are no longer symmetric

[snip]
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.

Yeup .. but it is important to understand just how many experiments that
COULD have shown SR was wrong, indeed gave results that supported it. NONE
have given results that contradict what SR predicts.


.

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