Re: Twin paradox revisited ll


"bill" <cosmosco@xxxxxxxxxxxxxxx> wrote in message news:1185235954.440484.53780@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 22, 10:26 pm, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in messagenews:1184981064.527191.20310@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jul 20, 7:11 pm, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:

No I would not. I cannot accept that the traveler *really* believes
that the earth is orbiting the sun at around 1m-s nor do I believe
that this is what would 'really' be happening.

This is the crux of the problem. The problem we have is that the
English language has evolved to describe things we see in
normal life. It turns out that, when high speeds are involved,
things are very different and we do not have words to adequately
describe what happens. Thus, is the current context, words
like 'really' and 'physically' do not have any useful meaning.

In everyday life, if I say something 'really' or 'physically'
happens, there is no need to explain what I mean; everybody
knows.

So, what can we do to come to any form of agreement?

Firstly, we can state the facts that are undisputed and
explicable without ambiguity in the English language. For
example, we agree that on his return, the traveller has
aged less then the inertial twin. We can also agree that
in the inertial frame of any twin nothing unusual happens.

Secondly, we can state what we expect the results of any
measurement will be. For example, during the cruise phase,
if either twin measures the clock of the other they will
measure it to be running slower than their own. This
statement applies to any and every sensible method of
measurement. In other words, there are no sensible
measurements whatsoever that do not show the results
described above. Is this real? How real do you want?
It is as real as the fact your head hurts when you hit it.

I agree that the travelling twin will see that the earth clock
*appears* to be running slower than his own clock but if he insists
that it *is* physically ticking...

You continue to try to understand what happens in terms of
the normal meaning of English words. This cannot be done.
There is no parallel to this situation in everyday life and no
English words to fully describe what happens. If you cannot
understand this point you will never make any progress.

over at a slower rate than his own
clock he is denying Einstein's 1918 article by insisting that he,
having experienced the force of acceleration, is *not* the moving
twin.

I understand that the 'twin paradox' resulted from questions raised by
people such as Dingle asking 'which is the *moving* clock? and that
Einstein attempted to overcome this paradox by pointing out that it is
the clock that experiences a force of acceleration which is, in
response to *that* question, *the* moving clock and that it is this
*moving* clock that incurs time dilation.

Most people seem to be ignoring this factor, making no response to
same.

It is the fact that one twin accelerates and one does not that
makes the situation non-symmetrical.

Do you accept that in *Einstein's* opinion it is the accelerated clock
that incurs time dilation *not* that the other clock incurs time
*contraction*? I'm not referring to what some physicists now believe
but what *Einstein* believed!

I cannot possible answer the question as to what Einstein believed
any particular moment and neither can anyone else. It is quite
unimportant anyway. Einstein was a great physicist who proposed
and developed his theories of relativity; he was not a prophet
and to try to construe the meaning of is every word is pointless.

Einstein showed that a clock that is made to travel in a circular path
around another clock ticks over at a slower rate than the stationary
clock. He did not, and would not, have written that the stationary
clock is then physically ticking over at a faster rate than it was
*before the other clock went into orbit* around it.

For a person accompanying that orbiting clock to insist that the
stationary clock is *physically* ticking over at a faster rate than it
was *before he went into orbit around it* is a ludicrous solipsist,
philosophical concept that has no place in *reality*.

In SR, a clock made to travel on a circular path is not in an inertial
frame. Making measurements from a non-inertial frame is
complex and bizarre. Even in Newtonian mechanics, measurements
from non-inertial frames are significantly more complicated.

He *can* say that the stationary clock *IS* ticking over at a faster
rate than his clock but to insist that this has *physically* occurred
- that the rate of operation of the stationary clock has *physically*
increased rather than the fact that the rate of operation of *his*
clock - as the result of its rate of travel with respect to the
stationary clock - has decreased, is solipsist nonsense!

You really must try to understand the point I am making about
use of the English language. You _must_ define exactly what you
mean by each of your emphasised words.


Anybody who suggests that during the first leg of the Hafele-Keating
experiment the laboratory clocks physically started ticking over at a
faster rate than the clocks in the aircraft and that during the second
leg the laboratory clocks physically started ticking over a slower
rate than the flying clocks is sprouting solipsist nonsense and if
that's what 'physics' shows the somebody should have a good look at
the subject of reality.

That is not what I asked. Which of the orbiting clocks told
the right time?

I very much doubt that Hafele or Keating, during the first leg of the
experiment , insisted that they were not moving, that it was the
planet's axial spin that had slowed down.

Of course not.


Thirdly, we can try to come up with forms of words which
describe the situation You might say that the mutual slowing
of clocks is a consequence of measurement in the world
in which we live.

On the other hand, *I* would say that the mutual slowing of clocks is
a solipsist nonsense which introduced a paradox that Einstein,
apparently unsuccessfully, attempted to solve.

This is not what all the world's physicist's would say.


This would be acceptable to most
physicists. A more personal view is that physics is all
about measurement, so the slowing is real, but here I am using
'real' in a specific way to mean 'as measured'. I would not
use the word in this context without explaining what I meant
by it.

If we 'measured' or 'determined' the shape of a steel rod placed in a
tank of water we would *assume* that it has bent at the surface of the
water however we *then * apply our knowledge (as Confucius suggested
we should) and come to the conclusion that *in reality* the rod has
*not* been deformed but that this is only a visual illusion in the
same way that the *apparent* slowing down of a *stationary* clock is
the result of a visual illusion created by *our* motion relative to
*it*.

Correct. When we make a measurement of a relatively moving
clock we do exactly the same. We make allowance for all known
effects. _After we have done that_ we find the moving clock to be
ticking more slowly than our own.

We can also use analogies to explain what we mean or
talk only in mathematical language. As Daryl has suggested
the more ways you have of looking at the subject the better
your understanding will be.

In 1989 I read an article in a local newspaper supposedly quoting
David Mermin from Cornwell University as stating that the moon
physically ceases to exist if nobody looks at it. The author continued
that it is the actual act of looking at the moon that creates its
reality and that this is the belief held by some of the world's best
physicists.

Such points may be relevant to a discussion about quantum
mechanics but they are not relevant to SR.

I asked a physicist if they truly believed that this would take place
and his response was 'No - but that's the closest analogy to what the
mathematics shows.' When I asked him the value of a mathematical
proposition that has *no* application to *reality* he suddenly
remembered an urgent job back at the office and promised to get back
to me.

Maybe another day.

Having noted, in his contribution to 'James Clerk Maxwell: A
Commemorative Volume', that sense perception creates reality, Einstein
also insisted that he liked to believe that the moon is still there
even when he's not looking at it.

Fine.

Having initially set out to establish the validity of mathematics,
Bertrand Russell was reluctantly forced to conclude "Mathematics may
very well be a subject in which we never know what we are talking
about nor that what we are saying is true."

No doubt.

In his address to the Prussian Academy of Sciences in 1921 Albert
Einstein stated "As far as the propositions of mathematics refer to
reality, they are not certain; and as far as they are certain, they do
not refer to reality."

Yes, he did.

A former Head of the School of Mathematics at the University of New
South Wales, Australia, Professor Simon Prokhovnik in his article 'The
twin Paradoxes of Special Relativity: Their Resolutions and
Implications' (having provided an equation in support of his theory)
wrote "There are plenty of self-consistent mathematical systems which
have scant relevance to physical phenomena or observations."

I agree, but SR is not one of them.

Having read Maxwell's mathematical interpretation of his work Faraday
wrote to him asking if he could provide an everyday version of that
work so that he (Faraday) could understand it. Apparently there was no
response

However, Maxwell's interpretation of Faraday's turned out to be one
of the most successful theories of physics ever.

It must be very difficult to provide logical analogies for
mathematical systems that have no application to reality.

So he *really* believes that the earth is *physically* orbiting the sun
at 1m-s?

Yes. It least I would in his position.

You need to define 'physically'.

That the traveler destroys all life on the planet.

By that definition, there is no change on Earth 'physically'.

In his opinion, all life is extinguished yet you classify this as
being 'no change'?

Incorrect. as explained below, he does not believe that.

If I was in his position I would head for the
nearest star.

Having 'believed' that all life on the planet has been obliterated it
would not only be 'from the earthbound twin's point of view, nothing
unusual has happened' but also from the *traveler's* point of view.

No he does not believe that. Although he measures time to have
slowed down on Earth, all the laws of physics are also transformed
in such a way that life goes on as usual. It is never the case in
SR that one observer measures a different final outcome
from another. Are you familiar with the 'pole and barn' paradox.

Yes.

The bit you have not grasped is that the passage of time is not
universal. This is very counterintuitive but it is the inescapable
conclusion of experiment.

Or rather, in the *interpretations* of those experiments.

I agree that all experimental results require interpretation but
the interpretations used in SR are no different from those used
in Newtonian physics. If you use light to measure some distant
event you must make allowance for its transit time, for example.
This is perfectly normal, indeed not to do so would be an
obvious error.

In their book 'The Matter Myth' Professors Paul Davies and John
Gribbin depict the explosion of a star that is two light years away
from the earth at the instant that the light from another exploded
star located another two light years further out reaches that star's
location and point out that, from our point of view, those stars
exploded simultaneously *and* at the very instant that we saw those
explosions based on the concept of 'zero four-dimensional spacetime
continuum' whereby we do *not* 'make allowance for [lights] transit
time'.

In his book 'Fiction Stranger Than Truth' Nikolai Rudakov quoted
Mendelssohn as stating

"It is not much sense for an astronomer, who sees a flare appear on
the sun, to say that the flare occurred eight minutes earlier because
the light takes eight minutes to travel this distance.
Since no faster means exist to inform the observer sooner of this
event, the latter only acquires physical reality for him at the moment
when he sees it."

This refusal to accept reality, i.e. not allowing for the transit time
of light, *is* 'an obvious error' or, in my opinion, mushroom
treatment.

Yes, of course it is. If you believe that relativity does that
you are suffering under a serious delusion.


In 'The Matter Myth'Davies and Gribbin suggest that as the result of
its inherent uncertainty people may have turned away from the subjects
of physics and mathematics and turned toward religion however in that
same book they actually contribute *toward* that uncertainty writing
that a galaxy that is moving away from us at superluminal velocity
does not contradict special theory on the basis that it is *moving
away from* not *moving past* us.

As from the very instant that an object has moved past us it is then
moving away from us and it is this type of misinformation that I am
trying to overcome.

As far as I
am aware there has been no experiment which proved that from the
traveler's point of view it is his twin that ages at the faster rate
than himself.

Over the whole journey the HK experiment does just that. When the
two clocks meet, one shows more elapsed time than the other. We
obviously cannot ask the clocks what they believe but we have to
take it that each clock measures time. In other words, if you fancifully
asked each clock what had happened during its journey it would
say 'I measured time to pass as normal, I therefore presume that the
other clock has run fast/slow while we have been separated'. Or
to put it another way, you tell me which clock in the HKX told the
right time.

They *all* told the right time *in their reference frame* but, as
above, it would be ludicrous for Hafele or Keating OR their clocks to
insist that the laboratory clocks physically ticked over at different
rates depending on the aircraft's relative motion compared to their
rates of operation *before* the experiment commenced.

I did not suggest otherwise.


--
Martin Hogbin






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