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From: Androcles on 4 May 2010 13:11

"harald" <hvan(a)swissonline.ch> wrote in message
news:e74170c7-7abf-4d1f-b2d9-c7c15ff109b1(a)e2g2000yqn.googlegroups.com...
On May 4, 5:57 pm, Tom Roberts <tjrob...(a)sbcglobal.net> wrote:
> harald wrote:
> > On May 2, 7:00 am, Tom Roberts <tjroberts...(a)sbcglobal.net> wrote:
> >> In SR you can select ANY inertial frame. There is no need to select one
> >> frame
> >> and use it throughout the year.
>
> > when you change inertial frame, you also declare
> > your earlier measurement as having been done in a "moving" frame.
>
> So what??? Who cares??? From the standpoint of SR this is irrelevant.

It would be irrelevant for SR if SR wasn't meant to also apply to
moving objects; and it would be irrelevant for this thread if the
topic concerned objects that are all the time in the same state of
motion.

> The point at issue is: do the fringes move as the interferometer is
> rotated?

No, that is definitely NOT the topic of this thread...

> NOTHING else matters.

That says it all: you are incapable of considering the topic that the
OP discusses. Worse, you insist on making inconsistent statements.

[..]

> > It's reassuring that you understand that the variation of velocity of
> > the Earth is relevant for stellar aberration. But that makes it even
> > more amazing that you cannot (or refuse to) understand that the
> > variation in velocity is equally relevant for Lorentz
> > contraction in SRT (which the OP called "SRT math").
>
> You, too, are confused about what "Lorentz contraction" means in SR -- the
> arms
> themselves are COMPLETELY UNAFFECTED by "Lorentz contraction".
>
[...]

> > the OP (DDRR) obviously meant that it is "physically
> > impossible" to get a null result with a *moving* interferometer
> > without a modified length of at least one of the arms, assuming that
> > the speed of light is completely unaffected by the speed of the Earth.
>
> Again, this is just plain not true -- that statement is implicitly adding
> unstated conditions that erroneously limit what can be considered, and
> they
> exclude SR inappropriately. SR is a counterexample: in SR the length of
> the arms
> does not change (even for a *moving* interferometer), the speed of light
> is
> unaffected by the speed of the earth, and yet SR predicts a null result.
> Note carefully the meanings of the words used: "length of the
> arms" relates to THE ARMS THEMSELVES, and does NOT refer to the
> distance some observer moving relative to the arms might happen
> to measure between their endpoints.

The meanings of your words are inconsistent: either one discusses an
observation from a system in which the interferometer is moving, or
one discusses it from a system in which it is in rest. You flip-flop
from one system to another in a single description.

SR predicts a null result for a moving interferometer (which is by
*definition* of the word "moving" *not* measured relative to a co-
moving or "proper" coordinate system), and you know very well that the
length in the direction of motion is shortened in the same system
which was used to define it as "moving".

> At base, this discussion hinges on the meanings of the words used; you,
> Paul,
> and DDRR all use unacknowledged PUNS on the meaning of "length" -- the
> word has
> different meanings at different places in your statements.

No, it is you - as shown here above. Length (in contrast to "proper
length") means in this context always the length as *measured* in the
same reference system as to which the word "moving" refers. It is
better to be specific, but an intelligent reader should be able to
understand a consistent use of references! If you answer to a newcomer
such as DDRR it requires a minimal effort to follow what he is
thinking, without imposing *your* way of formulating things on him and
then giving replies that are completely besides the point.

> DON'T DO THAT! If you
> guys were careful about the meanings of the words you use, you
> would not be confused, and would not need this discussion.

I'm not confused, while you risk to confuse people with your stubborn
flip-flopping between references without any concern for the topic
that they discuss.

> At base this is due to the
> implicit and unquestioned assumptions that you carry, many of which are
> wrong.
> You MUST learn to discard this baggage, or you will never be able
> to understand modern physics.
> Just like Paul you need to learn how to read, write, and
> think more accurately.

Here you gave me good laugh Tom. :-) Did you publish any paper on SRT
and length contraction in a quality peer reviewed journal?

[..] (Well, you also need to pick one theoretical context
> and stick to it.)

Tom, the theoretical context of this thread is to consider a *moving*
Michelson interferometer, and the therewith consistent length of the
*moving* arms (which implies that the lengths are *not* described in
rest!).

If your brain had not lost its flexibility, you could have had a
constructive discussion with the OP by now.

Ciao,
Harald

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