From: Daryl McCullough on
harald says...

>Einstein explained how a paradox arose with the inception of GRT:

It's at http://tiny.cc/kz0uq

I read the dialog, and I do not agree with your description of it, as a paradox
of GR. The fact is, as I said, the "GR description" is actually not GR at all,
it's SR being expressed in noninertial coordinates. The use of the term
"gravitational field" is picturesque and suggestive, but nothing that Einstein
says about interpreting the twin paradox from the point of view of the traveling
twin is in any way dependent on Einstein's theory of gravity. As I have pointed
out, the relationship goes the other way around: Einstein's theory of gravity
piggy-backs on SR as expressed in non-inertial coordinates.

If you start with ordinary coordinates (x,t), and do a transformation to
noninertial accelerated coordinates, then in these new coordinates there are
weird effects:

1. An unsupported object will spontaneously accelerate "downward". A force must
be exterted to keep a massive object "at rest".

2. For two clocks at rest at different "heights", the one that is higher will
run faster (that is, dT/dt is greater, where T is the time on the clock, and t
is coordinate time).

These are *not* inferences from GR. They are inferences from *Special
Relativity* that are derivable using calculus. You can picturesquely describe an
accelerated coordinate system in terms of "gravitational fields" as an
explanation for point 1, but that has no physical content. You are just giving a
name to the effect in point 1.

To reiterate, I think that you have completely misinterpreted the twin paradox
if you believe that is a consistency issue for General Relativity. It is not.
The only "General Relativity" that Einstein uses in that dialog is SR +
noninertial coordinates, which cannot *POSSIBLY* be inconsistent unless SR is.

--
Daryl McCullough
Ithaca, NY

From: Daryl McCullough on
Edward Green says...

>There's a canard floating about here somewhere, which I see has very
>early origins. It runs as follows: "In SR, all inertial coordinate
>systems are shown to be equivalent, in GR _all_ coordinate systems are
>equivalent". It may not be false, but the two equivalences are not
>equivalent. One contains a strong physical insight, the other, more a
>tour of mathematical force, that all coordinate systems may be forced
>to be equivalent. I lack the skill to state this precisely, but there
>is something there.

Can you say a little more about this difference? I might agree, or I might not.

I've thought about it a little, and I realize that it's a little subtle to say
what it means to say that all inertial frames are equivalent. We can say roughly
that if there are two frames F and F', and you perform the same experiment in
both frames, you'll get the same results. But what, exactly, does "the same
experiment" mean? What does "the same result" mean? Just one subtlety is system
of units: how do you know that the experimenters in F and F' are using the same
standards for length and time? You want to be able to say something like this:
Such and such a chemical reaction took T seconds in frame F, while it took T'
seconds in frame F'. To know whether this confirms or violates the relativity
principle, you have to know whether T and T' are being measured in the same
units. But how do you know that? Ultimately, you have to rely on some
reproducible experiment, such as chemical or mechanical reaction, in order to
establish that F and F' are using the same units of time. But then it becomes
tautological that those reactions work the same in both frames.

Another way to talk about invariance is in terms of coordinate transformations.
For a particular mathematical formulation of some law of physics, we can ask
whether its form is invariant under particular kinds of coordinate
transformations. Newton's laws are invariant under Galilean transformations, but
not under Lorentz transformations, and not under nonlinear transformations. SR
is invariant under Lorentz transformations, but not under Galilean or nonlinear
transformations. GR is invariant under all possible transformations.

But this characterization in terms of coordinate transformations has no real
physical content. You can *ALWAYS* write any law of physics in a way that is
invariant under arbitrary coordinate transformations. So what's the *physical*
sense in which SR satisfies a relativity principle, and GR satisfies a principle
of equivalence of all coordinate systems?

Here's the completely non-obvious answer: It's in terms of nondynamic scalar,
vector and tensor fields! Let me explain this with the three theories under
discussion: Newtonian physics, Special Relativity, and General Relativity.

In Newtonian physics, there are no intrinsic spatial vectors. There can be
spatial vectors (such as the velocity vector of a particle), but they are always
*contingent*; they depend on initial conditions, and can be modified by applying
forces. How does the nonexistence of nondynamic spatial vectors satisfy the
principle of relativity? Well, if there were a preferred rest frame, then there
would be a preferred velocity vector---the velocity of the rest frame. It would
be an intrinsic spatial vector.

Newtonian physics *does* have an intrinsic scalar field, namely universal time.
It's nondynamic in the sense that there are no forces that can ever change the
value of universal time.

In Special Relativity, there is no intrinsic vector fields or scalar fields. But
there *is* an intrinsic tensor field, namely the metric tensor. It's nondynamic,
in the sense that there are no forces in SR that are capable of changing the
metric tensor.

In General Relativity, there are no intrinsic, nondynamic scalars, vectors, or
tensors. There are important tensors (the metric tensor, the curvature tensor)
but they are dynamic, they evolve, and do not have god-given values.

--
Daryl McCullough
Ithaca, NY

From: eric gisse on
G. L. Bradford wrote:

>
> "eric gisse" <jowr.pi.nospam(a)gmail.com> wrote in message
> news:i0r22e$bio$2(a)news.eternal-september.org...
>> G. L. Bradford wrote:
>> [skipped to the end]
>>
>>> Of course few of them are first tier thinkers and seers, nor even
>>> second
>>> tier, nor even third tier, nor even fourth tier....
>>>
>>> GLB
>>>
>>> ==========================
>>
>> So what's your training in the sciences and why does it put you so many
>> cuts
>> above those who have put a decade of study into the subject?
>>
>> You've been posting here for years but you don't seem to show much
>> knowledge
>> about science...
>
> ===================
>
> Physicist Marc Davis at a seminar on string theory a couple of decades
> ago
> was heard to excitedly exclaim, "We know next to nothing about the
> universe!"

He's wrong.

>
> Gisse, I'm only interested in the many faces, the many views, of the
> Universe, among many, many, other things I'm interested in and follow. I'm

So when was the last time you went to a research library to see what has
been recently discovered? Or read a preprint on arXiv? Bet you don't even
know.

> interested but I'm no physicist, I've stated that again and again, and
> again, over the last two decades of my participation in these two open
> forums, but even I know, from experience with your type if nothing else,
> that you know far less than you puff yourself up to claim, or imply, you
> know.

Gosh, I don't know about that. I have literature references and an actual
college education...

I guess this long winded response is your way of saying "No Eric, I have no
formal training in science."

> You make it only too obvious that you are just as superficial, just
> as lacking in breadth and depth, as I pointed out, a light weight rote
> priest and fool with not the slightest capacity for vision and imagination
> and perception to you.

You sound rather certain of that. I support my claims with literature
references and actual reasoning that stands up to scrutiny. How's bout you?

> Davis isn't even close to the only one who has said
> or written the same thing. And the numbers of physicists and others, even
> as the total numbers of professional physicists are fast imploding here in
> Western Civilization, who say it and write it ("We know next to nothing
> about the universe") seem only to be growing these days.

What a nice emotional appeal. Are your claims supported by reality?

Are the numbers of awarded PhD's and college degrees in physics and physics-
related fields decreasing? No. Not since the last time I looked. Perhaps you
have different numbers?

As for the 'we know nothing' crowd, much lies in your wording. It might
_seem_ that way to you but I bet there is one hell of a feedback loop going
on in your head.

>
> You didn't go after what I said about the dimensionally three cornered
> picture, the deeper layered picture, versus the two pointed line only
> picture in my post. You didn't say that what I detailed about what is
> observed and what is unobserved is wrong, pointing out what you see to be
> wrong with what I describe about relative and real. You didn't because you
> couldn't get past the fact of the "observable universe" versus the
> "unobserved, and unobservable, universe." You didn't because you couldn't
> get past the two universe picture and realizations I present in my own
> way, or better yet the dual universe picture and realizations. The certain
> deductions to be made -- that I make -- regarding it. Being what you are,
> following in the footsteps of all the other 1-dimensional types just like
> you throughout history, it left you only one thing you could do if you
> were going to respond at all, didn't it?

I have no real interest in dissecting the excess verbiage that constitutes
your opinion about something only you care about.

>
> GLB
>
> ===================

From: colp on
On Jul 5, 11:52 am, Cosmik de Bris
<cosmik.deb...(a)elec.canterbury.ac.nz> wrote:
> On 4/07/10 11:07 , colp wrote:
>
>
>
> > On Jul 4, 2:10 am, PD<thedraperfam...(a)gmail.com>  wrote:
> >> On Jul 3, 1:04 am, colp<c...(a)solder.ath.cx>  wrote:
>
> >>> On Jul 3, 2:57 am, PD<thedraperfam...(a)gmail.com>  wrote:
>
> >>>> On Jul 1, 6:25 pm, colp<c...(a)solder.ath.cx>  wrote:
>
> >>>>> On Jul 2, 2:26 am, PD<thedraperfam...(a)gmail.com>  wrote:
>
> >>>>>> On Jul 1, 12:53 am, colp<c...(a)solder.ath.cx>  wrote:
>
> >>>>>>> On Jul 1, 11:37 am, Koobee Wublee<koobee.wub...(a)gmail.com>  wrote:
>
> >>>>>>>> On Jun 30, 4:20 pm, artful wrote:
>
> >>>>>>>>> On Jul 1, 8:47 am, colp wrote:
> >>>>>>>>>> The statement that "moving clocks run slow" isn't an
> >>>>>>>>>> oversimplification, it is directly inferred from Einstein's
> >>>>>>>>>> "Electrodynamics of Moving Bodies".
>
> >>>>>>>>> It IS an over simplification.  There is more to SR than just clocks
> >>>>>>>>> running slow.
>
> >>>>>>>> Nonsense and mysticism.<shrug>
>
> >>>>>>> A postulate is just an assumption with better table manners.
>
> >>>>>> Yes, indeed. By DEFINITION, a postulate is something that is ASSUMED.
>
> >>>>>> In science, the test of a postulate is based on experimental check of
> >>>>>> the *consequences* of postulates. A direct test of the postulate is
> >>>>>> not required.
>
> >>>>> One such test is the test for paradoxes arising from one or more
> >>>>> postulates. For example, the following two postulates lead to a
> >>>>> paradox, meaning that not all the postulates are correct:
>
> >>>>> 1. Statement 2 is true.
> >>>>> 2. Statement 1 is false.
>
> >>>>> The paradox that arises from the postulates of Einstein's
> >>>>> "Electrodynamics of Moving Bodies" can be described as follows:
>
> >>>>> "Examples of this sort, together with the unsuccessful attempts to
> >>>>> discover
> >>>>> any motion of the earth relatively to the light medium, suggest that
> >>>>> the
> >>>>> phenomena of electrodynamics as well as of mechanics possess no
> >>>>> properties
> >>>>> corresponding to the idea of absolute rest. They suggest rather that,
> >>>>> as has
> >>>>> already been shown to the first order of small quantities, the same
> >>>>> laws of
> >>>>> electrodynamics and optics will be valid for all frames of reference
> >>>>> for which the
> >>>>> equations of mechanics hold good.1 We will raise this conjecture (the
> >>>>> purport
> >>>>> of which will hereafter be called the Principle of Relativity ) to
> >>>>> the status
> >>>>> of a postulate, and also introduce another postulate, which is only
> >>>>> apparently
> >>>>> irreconcilable with the former, namely, that light is always
> >>>>> propagated in empty
> >>>>> space with a definite velocity c which is independent of the state of
> >>>>> motion of the
> >>>>> emitting body."
>
> >>>>> Einstien, Electrodynamics of Moving Bodies (Introduction)
>
> >>>>> This text describes Einstein's postulate that there is no preferred
> >>>>> inertial frame of reference.
>
> >>>>> "If at the points A and B of K there are stationary clocks which,
> >>>>> viewed in the stationary system, are synchronous; and if the clock at
> >>>>> A is moved with the velocity v along the line AB to B, then on its
> >>>>> arrival at B the two clocks no longer synchronize, but the clock moved
> >>>>> from A to B lags behind the other which has remained at B ..."
>
> >>>>> Einstien, Electrodynamics of Moving Bodies (Section 4)
>
> >>>>> The text describes the time dilation of a clock that moves from point
> >>>>> A to point B. If there is no preferred frame of reference then it is
> >>>>> just as true to say that
> >>>>> the clock is viewed as part of a stationary system and the points A
> >>>>> and B are in a moving system which moves at velocity -v. The
> >>>>> conclusion that time for both systems can be dilated with respect to
> >>>>> the other system is paradoxical.
>
> >>>> No, it's not paradoxical at all.
>
> >>> It is paradoxical because time for both systems cannot be dilated with
> >>> respect to each other.
>
> >> This is your assumption about what can and cannot be.
>
> > No, it is a logical inference derived from Einstein's description of
> > time dilation and his postulate that there is not preferred frame of
> > reference.
>
> Now you are contradicting yourself.

Wrong. In this case the inference of a paradox means that Einstein's
assumption is wrong.

> You started this whole thread

I didn't start this thread, Daryl did.

> with a
> reference to a paper claiming that it was possible to find an absolute
> frame.

You mean the paper I quoted from the "Symmetric Twin Paradox" thread?

> This paper you touted as showing SR to be wrong.

What do you mean by 'touted'?

> and you are not
> using Einstein's description of time dilation you are using a mish-mash
> of stuff of your own making.

Wrong. I quoted Einstein's description of time dilation from
"Electrodynamics of Moving Bodies". The text is even present in the
post that you replied to. If you think that my description is
materially different, then quote what I said that shows that.
From: colp on
On Jul 5, 7:31 am, PD <thedraperfam...(a)gmail.com> wrote:
> On Jul 3, 6:06 pm, colp <c...(a)solder.ath.cx> wrote:
>
>
>
> > On Jul 4, 2:14 am, PD <thedraperfam...(a)gmail.com> wrote:
>
> > > On Jul 3, 1:06 am, colp <c...(a)solder.ath.cx> wrote:
>
> > > > On Jul 3, 3:03 am, PD <thedraperfam...(a)gmail.com> wrote:
>
> > > > > On Jul 1, 7:56 pm, colp <c...(a)solder.ath.cx> wrote:
>
> > > > > > On Jul 2, 2:21 am, PD <thedraperfam...(a)gmail.com> wrote:
>
> > > > > > > On Jun 30, 5:47 pm, colp <c...(a)solder.ath.cx> wrote:
>
> > > > > > > > <quote>
>
> > > > > > > > > > At best, all you've done is show the
> > > > > > > > > > fallacies or assumptions inherent in COLP's Oversimplified Relativity.
> > > > > > > > > What specific fallacies or assumptions? Quotes, please.
>
> > > > > > > > Sure. You've used the statement from COLP's Oversimplified Relativity
> > > > > > > > that moving clocks run slow (which you've said is true even for blue-
> > > > > > > > shifted clocks), and you've used the statement that COLP's
> > > > > > > > Oversimplified Relativity makes no provision whatsoever for a
> > > > > > > > compression of time for a clock turning around. This immediately leads
> > > > > > > > to several paradoxes, and this is ample reason to chuck Colp's
> > > > > > > > Oversimplified Relativity.
> > > > > > > > </quote>
>
> > > > > > > > The statement that "moving clocks run slow" isn't an
> > > > > > > > oversimplification, it is directly inferred from Einstein's
> > > > > > > > "Electrodynamics of Moving Bodies".
>
> > > > > > > It IS an oversimplification. If you've inferred this from his 1905
> > > > > > > paper, then you've oversimplified.
>
> > > > > > No, inferring something from a paper does not constitute an
> > > > > > oversimplification.
>
> > > > > It does if it's an oversimplification of what's presented in the
> > > > > paper!
>
> > > > It isn't. Claiming that it is without showing why is of no value.
>
> > > You aren't owed an education on a newsgroup, despite your taunts to
> > > the contrary.
>
> > I'm not asking for an education, I'm pointing out that all you have to
> > defend you beliefs are hollow claims.
>
> No, they are fully supportable claims.

Wrong. The burden of proof is yours. You can't support them because no
such support exists.