Re: Twin paradox revisited ll

On Jul 27, 6:48 am, "Martin Hogbin" <goatREMOVETHIS...@xxxxxxxxxx>
wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in messagenews:1185416809.446909.24230@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Martin Hogbin wrote:
"bill" <cosmo...@xxxxxxxxxxxxxxx> wrote in messagenews:1185339722.394291.34610@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

If something that happens cannot be described in everyday language
then in my opinion that 'thing' or 'event' does not take place. If it
can only be 'described' in mathematical 'language' or propositions I
agree with Einstein that it has no place in the real world.

Experiment indicates otherwise.

Please provide an example of an event or a 'thing' that can be
experimentally tested but which cannot, of itself, be explained in
everyday language.

The results of all the experiments that confirm relativity

In other words - in your opinion - the results of the Michelson-Morley
experiment *cannot* be explained in everyday language.

In your opinion - the results of the Hafele-Keating experiment cannot
be explained in everyday language? I refer you to Clifford M Will's
book 'Was Einstein Right?' in which he (p.54, Oxford University Press,
1986) clearly explains, *in everyday language*, the results of those
experiments.

In your opinion - the results of particle acceleration experiments
*cannot* be explained in everyday language?

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.

The Hafele-Keating experiment as well as information garnered from
global positioning satellites and from particle acceleration
experiments have *all* involved non-inertial frames yet they are *all*
cited as providing confirmation of SR.

None of what you say negates what I have said above.

I did not suggest that my comments *negate* SR just that they are
examples of *your* comment that "a clock made to travel on a circular
path is not in an inertial frame."

SR is a special case of GR. SR is generally taken to include everything
in GR except gravitation.

In 'Relativity (the Special and General Theory)' Einstein wrote (p.76,
Crown, 1961) that
special theory *only* applies to *zero* gravity locations.

As I said,SR does not include gravitation and strictly speaking should
not be used when gravity is involved. My point was that gravity
can play a relatively minor or even insignificant role. Ultimately
every experiment should be analysed using GR but is many cases
SR is sufficient in practice. I would agree with you that the GPS
should not be quoted as evidence of SR since gravitation plays
a small but significant role.

The experiments you quote confirm relativity.

On the basis (of what I understand is a primary tenet of physics) that
no experiment can *prove* a theory only *dis*prove a theory those
experiments do *not* as some people insist *prove* SR but merely
appear to confirm its concepts.

That is what I said.

A version of the traveler's journey whereby he does not take a
straight out and return journey but travels in a circular path
provides the same argument as the former example but - as you point
out - this is *not* an 'inertial frame' journey.

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.

I note that you decline to do this.

Because I am of the opinion that it is a waste of effort to explain
what I mean by 'can' and 'is' and 'physically' and 'his'. If you can't
understand what I am saying then I would be wasting my time trying to
explain it. There is *no* _must_ about it.

But this is what physics is about. How can I tell if something 'physically'
happens? If there is no objective way to tell, it is not physics just your
personal feelings.

And the concept that the earth bound twin physically ages at the
faster rate and only during acceleration following turn around is
*not* physics but is just the personal feelings of the traveller.

Thank you, that's precisely my point. A traveler who insists that the
earth's axial spin decreases or increases on the basis that what he
sees is, from his point of view reality, would also insist that Hafele
or Keating *would* have concluded that it was the planet's axial spin
that had slowed down.

I am not sure what you mean here. Are H and K on a plane with
one of the clocks or on the Earth's surface.

The latter. Having returned to the laboratory at the end of the second
journey they determine the time differences between the clocks. They
could either conclude that their clocks ticked over at the faster rate
*or* that the laboratory clocks ticked over at a slower rate which
would mean that the earth's axial spin had also decreased.

No, you are continuing to think of time as being absolute. In a
relatively moving frame the Earths rotation does indeed slow down.

Pardon the pun but you keep going round in circles.

The earth's rotation does *not* slow down - this is merely the
personal feelings of the traveller.

We could move the HKX to the abovementioned off-earth circular
trajectory journey where the astronaut commences his trip from a
geostationary location. This is precisely the same as Einstein's
reference to a clock that is made to travel in a circular path around
another clock but the traveler's course (clock's path) is eccentric to
the earth (Einstein's central clock).

For that astronaut to insist that during his trip the earth's axial
spin alternately increased and decreased is just as nonsensical as
Hafele or Keating insisting that the earth's axial spin physically
decreased during the first part of the experiment and that it
increased during the second part of their experiment.

As I have said before, to attempt to describe what is observed
from a non-inertial frame is difficult - but possible.

I am of the opinion that at least *some* of the world's physicists
might agree with Hafele and Keating that the laboratory clocks did
*not* tick over at a faster rate than their own clock during the first
leg of the experiment because for this to take place they would also
have to believe that the earth's axial spin had increased and that the
earth's axial spin decreased during the second leg of that experiment.
Seemingly you do not believe that either Hafele or Keating would have
insisted that this actually took place.

From any relatively moving reference frame, the Earth's rotation
does indeed slow down.

So *now* you are suggesting that Hafele and Keating *should* have been
of the opinion that the earth's rotation *was* affected by *their*
location in a "relatively moving reference frame." That's *not* what
you said before.

I was not sure where they were supposed to be. In a relatively moving
frame the Earth's rotation does slow down. We, of course, notice nothing
because we are on the Earth.

The concept that 'the earth's rotation does slow down' is merely the
personal feelings of the traveler.

I assume that you mean that *all* of the world's physicists would say
that a clock that is moving past another clock would physically tick
over at slower rate than the latter and that the latter would
physically tick over at a slower rate than the former

As ever, you have not defined what you mean by 'physically'.

As distinct from 'seemingly' as a result of a visual illusion as per
the steel rod in a tank of water example.

In that case, yes. See my other post.

which is *not*
what Einstein wrote in his 1918 article where he insisted that it is
*only* the clock that experiences the force of acceleration as it
moves to the other clock's location *which is the one that has
incurred time dilation*. Of course, all the world's physicists might
not agree with Einstein.

Overall, it is the non-inertial twin whose clock runs slower. That
is the point that Einstein was making in his 1918 article.

That is *precisely* the point I am trying to make!

According to *Einstein* it is the non-inertial clock that ticks over
at the slower rate than the inertial clock and anyone who insists
that the inertial clock ticks over at the slower rate on the basis
that this is what the non-inertial twin observes is contradicting
Einstein. According to that article, Einstein was of the opinion that
it is *only* the non-inertial clock that, in *reality* physically,
really, actually, incurs time dilation.

No, you are misunderstanding him.

Did he, or did he not insist in that article that it is the clock
that experiences the force of acceleration which is the one that
incurs time dilation?

You wrote, above, "Overall, it is the non-inertial twin whose clock
runs slower. That is the point that Einstein was making in his 1918
article."yet when *I* write that my understanding of that article is
that 'it is the non-inertial twin whose clock runs slower' you insist
that I am misunderstanding him!

Inertial frames are special and making measurements in makes
life easy. which is why it is fairly easy to calculate the elapsed time
of the traveller from the Earth's reverence frame.

Calculating the elapsed time for the earthbound twin from the
frame of the traveller is much harder, but possible.

To make life a little easier let us assume the journey takes place
in three stages. We assume a flying start and finish in which the
traveller passes by Earth at speed and when very close to his
twin they compare clocks (and photographs of one another).

In his 1918 article Einstein insisted that the *only* way that the
rates of operation of the clocks can *physically* be compared is when
they are *stationary* alongside each other i.e. located in the *same*
inertial reference frame.

No he did not. Obviously clocks can be compared when
they are in motion, provided that they are in the same place.

I am of the opinion that your denial that this is what Einstein wrote
in that article is erroneous.

Of course you cannot compare the rates of two clocks by
this method because, if they are in relative motion, they will
only be at the same place for an instant

You are going round in circles again. You wrote "Obviously clocks
*can* be compared when they are in motion" and now you state "you
*cannot* compare the rates of two clocks by this method...."

You wrote "...if they are in relative motion, they will only be at the
same place for an instant.."

I suggest that *the rates of operation* of the clocks *cannot* be
determined *in an instant* nor can their rates of operation be
compared by looking at photographs of same.

During the cruise phases each twin measures the other's
clock to be running more slowly than his own. Neither
has any special claim to considered 'correct'.

And it seems to me that this paradox is *precisely* what Einstein
sought to overcome.

Absolutely not. Which one would you say is correct?

I'm not talking about which one *I* would say is correct but what
*Einstein* 'said' in that article.

During the turnaround the earthbound twin measures the
traveller's clock to be running more slowly, dependent only
on the traveller's relative velocity.

Having come to a stop the traveler's clock is in the same reference
frame as the earth clock hence it is ticking over at the same rate as
his twin's clock. He flips his ship end over end and during this turn
around period - on the assumption that he and his clock are at the
centre of his ship - he has *no* relative velocity other than the fact
that, during the few minutes that it takes to flip the ship over, he
is *not* moving toward, or away from, his twin. If he, having come to
a stop, simply reverses his motors he has absolutely *no* velocity
relatively to his twin so how can the latter measure his twin's clock
to be 'running more slowly'?

That is what I said. The clock is measured to be running slowly
when it is moving to and from the Earth. When it is stationary
with respect to the Earth it is measured to run at the same speed
as you quite rightly say.

No that is *not* what you said. You wrote that "*During the
turnaround* the earthbound twin measures the traveller's clock to be
running more slowly." You did *not*, in that sentence, say that "The
clock is measured to be running slowly *when it is moving to and from
the Earth.*"

During the turnaround the travelling twin measures some
very strange things such as the earthbound twin's clock
running backwards! Note however that he is making his
measurements in a non-inertial frame.

He measures (sees, determines, observes) that his twin's clock is
running backwards in contradiction of the respective laws of physics
as they apply to the physical operation of clocks and measures (sees,
determines, observes) his twin's beard *reducing* in length or his
twin coming back out of his grave and he *believes* that this is
*physically* (really, actually) taking place? *Very* strange things
*indeed*.

Yes, that is why we do not make measurements from non-inertial
frames.

The idea that the traveler 'can' see his twin arising from the grave
or the earth spinning backwards on its axis or its orbit of the sun
reversed are prime examples of the type of solipsist nonsense - on
behalf of the *traveler* of course - that I believe should *not* be
applied to physics.

You can believe what you like but physicists believe the
results of experiment.

I note your reference to 'physicists' rather than you previous
reference to *all* physicists.

If I were talking to a physicist who truly believed, as apparently do
you, that the earth bound twin's casket disinters itself and that the
twin comes back to life I would tend to walk away from that
discussion.

When the two twins meet, they both agree that the traveller
has aged less. The earthbound twin puts this down to the
fact that the other twin's clock has run slower that his own
during the journey.

The traveller's explanation is that the earthbound twin's clock
went wild during the turnaround.

The earth bound twin's clock went wild or the traveler's mind went
wild?

Neither twin noticed anything odd going on with their own
clock although the travelling twin was able to detect that
he was not in inertial motion during the turnaround.

Having been of the opinion that during the first stage of the event it
was the earth clocks that were ticking over at the slower rate - the
traveler, in order to comply with Einstein's insistence that the
*only* way that the rates of operation of the respective clocks can be
*physically* (actually, really) compared, bring his ship to a stop,
turns it around and *accelerates* to the earth's location and, having
learned Einstein's 1918 concept, that it is *him* and *his* clock,
having experienced that force of acceleration, which incurs time
dilation thus that whilst he is of the opinion that the rate of
operation of his clock has remained constant he *must* conclude that
in *reality*, i.e. as insisted upon by Einstein, his clock was ticking
over at the slower rate.

Why does the traveller not conclude that the Earth based
clocks have run fast?

He does *not* believe that the earth based clocks have run fast on the
assumption that he is aware of and accepts Einstein's 1918 article
concept that his is the non-inertial reference fame.

Although the Hafele-Keating experiment did not involve SR's required
inertial reference frames I presume that *some* of the world's
physicists would agree that the flying clocks ticked over at a slower
rate than the laboratory clocks during the first leg of the experiment
thus that they agree with Hafele and Keating's (assumed) decision that
the earth's axial spin did not slow down.

Are you talking about earthbound physicists or the ones who travelled
with the clocks?

Are you *now* contradicting your previous comment that Hafele and
Keating would *not* have been of the opinion that the earth's axial
spin decreased or increased as the result of their rate of travel with
respect to the laboratory clocks.

I am talking about *both* sets of physicists.

They would conclude different things.

Obviously Einstein's accomplishment meant *nothing* to people who
effectively suggest that the earth bound twin can arise from his grave.

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.

The 'observation creates reality' concept that the moon ceases to
exist if nobody looks at it or - conversely - that it is the act of
observation that creates reality, *is* relevant to the idea that if
the traveler observes the other clock to be ticking over at a slower
rate than his own clock this is, in his opinion, 'reality' in the same
way that Hafele or Keating (hypothetically) observing the laboratory
clocks apparently ticking over at faster rate than their own clocks
could have assumed that the laboratory clocks *were* ticking over at
the faster rate than their own clocks thus, consequently, that the
earth was spinning at a faster rate than it was before they took off.

Whether a moving observer chooses to observe a clock in a
different inertial frame or not it is still ticking more slowly than
his own.

And the traveler who, having accelerated following turn around,
insists that his clock is *not* the clock referred to in Einstein's
1918 article as being the one that *is*ticking over at the slower rate
is deluding himself regardless of whether or not he can *see* his
twin's clock.

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." He, of course, referred to *all* other
propositions of mathematics *except* SR did he?

Not especially.

That's a deliberately limp response.

Yes, because that is a completely irrelevant quote, even if it
was by Einstein.

The concept of relativistic 'Doppler' effect is based on the special
theory mathematical proposition that a moving clock ticks over at a
slower rate than a stationary clock.

We are discussing Einstein's concept of time dilation therefore I am
of the opinion that any comments made by Einstein in relation to the
*validity* of that concept *are* relevant.

You seem to be mentioning a number of diverse philosophical texts
on physics which have little to do with the subject in hand.

The subject on hand *is* the philosophical, solipsist attitude
adopted by a traveler who, presumably being aware of Einstein's 1918
attempted negation of the clock paradox, insists that his opinion
takes precedence over Einstein's.

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.

What gave you that impression?

Because you keep mentioning it. If you agree that relativity makes
complete allowance for the transit time of light then we can drop
that subject.

In his book 'Fiction Stranger Than Truth' Nikolai Rudakov wrote that
special theory's concept of length contraction (without which SR's
concept of the constancy of light speed cannot be maintained) is
determined on the basis that the observer does not allow for the
transit time of light.
Nikolai depicts two identical ships out in space that are at rest
alongside each other. One of them (A) accelerates away from the other
one (B), travels in a large circle and returns past B at near light
speed.

An observer, located at *a specific point* on the hull of ship B sees
the front end of ship A directly in line with the front end of his
ship at the very same instant that he sees the rear end of ship A in
line with him thus he concludes that A has contracted to a length that
is equal to the distance from him to the front of his ship on the
basis that he makes *no* allowance for the
transit time of the message that the front ends of the ships are
*seemingly* at the same location.

He does *not*, on the basis of philosophical solipsism, allow for the
fact that in the time it has taken for that message to reach him, ship
A has moved.

I have not read the book you mention but if it indeed claims that
SR does not allow for the transit time of light it is wrong.

You are now arguing about simple matters of fact. SR is a well
known and understood theory and any text book on the subject
will tell you what it is based on. I can assure you that SR is not
based on making measurements which ignore the transit time of
light.

You have obviously studied a number of diverse writings on
relativity and come to some very weird conclusions. There
are several people on this group who could correct your
misunderstandings if you wish. Alternatively you could continue
to rant.

--
Martin Hogbin

Your having typically resorted to personal insult terminates our
discussion.

.

Relevant Pages

  • Re: The speed of gravity revisited
    ... clock experiences when the temperature increases: the clock slows, but nothing happens to real time as used to measure change in the universe at large. ... miracle means "an act of God". ... That is the meaning I intended in my use of the word in this physics context. ... the apple falls from the tree because there is a net graviton wind blowing down toward Earth because Earth blocks part of the graviton wind coming up from below. ...
    (sci.physics.relativity)
  • Re: Relativistic Physics - Science or Religion?
    ... >Modern physics, at least that part which is based upon Dr. Einstein's work, is ... >compared the time recorded by that clock with the time recorded by an identical ... He did not accept the possibility that the velocity of the trip ... but neither theory is a theory of gravity. ...
    (sci.physics)
  • Re: collection of ideas on relativity
    ... Take note that when we measure *anything* our measurements may ... It should be physics' goal in general to have all ... have a light-source and a light-detector, and perhaps a clock and a ... an amount of time while a light-clock *derives* an amount of time. ...
    (sci.physics.relativity)
  • Relativistic Physics - Science or Religion?
    ... Relativistic Physics - Science or Religion? ... physicist transported an atomic clock around the world on jet airliner and ... He did not accept the possibility that the velocity ... with a medium, called the Aether. ...
    (sci.physics.relativity)
  • Relativistic Physics - Science or Religion?
    ... Relativistic Physics - Science or Religion? ... compared the time recorded by that clock with the time recorded by an identical ... He did not accept the possibility that the velocity of the trip ... with a medium, called the Aether. ...
    (sci.physics.particle)
Loading