Re: Einstein's Train Gedanken Re-visited

On Jun 14, 9:35 am, Uncle Ben <b...@xxxxxxxxxxx> wrote:
On Jun 14, 8:30 am, Uncle Ben <b...@xxxxxxxxxxx> wrote:



On Jun 14, 6:46 am, "Androcles" <Headmas...@xxxxxxxxxxxxxxxx> wrote:> "G" <gehan.ameresek...@xxxxxxxxx> wrote in message

news:7ab963ee-23dc-4e57-8b6e-fbadf806b457@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Jun 13, 6:16 pm, "Androcles" <Headmas...@xxxxxxxxxxxxxxxx> wrote:

http://tinyurl.com/c53cqo

Thanks for the hyperlink, but I have read the scruffy rat theory and
it is not clear to me where A and B are

Let me put it this way;

...

No, let's not. Instead, let's help Androcles sort out his scruffy
story.

The references to A and B are found in Einstein's famous 1905 paper
that shook the world. In particular they refer to a thought xperiment
described the first section, called the "Kinematical Part", after the
introduction, in subsection 2.

There Einstein first raises the question, if clocks are synchronized
in one inertial frame of reference, are they thereby also synchronized
with respect to another frame of reference in motion with respect to
the first.  His result, no, they are not.

To synchronize clocks well apart from each other, Newton assumed that
there is no problem: time is universal and absolute.  But to be
consistent with Maxwell's theory, AE has to question that assumption.
If the speed of light is to be a universal constant, as he proposes,
he uses that postulate to define synchronization with light rays as
Androcles describes.

So AE uses a rod to define distance, uses c as his standard, and
imagines clocks synchronized along the x axis of a frame of reference
that he calls the "statioary system," although one must not get too
attached to the term "stationary," which has no privileged status in
relativity.

A abd B are the coordinates of the ends of the rod, as Androcles could
have said at the outset, since he finally admits that he knew very
well.

To answer the present question, "Are the clocks just set up
synchronized also with respect to another frame of reference moving at
speed v w.r.t. the first system?", he sets out in imagination with the
rod now moving at v along with two moving observers at points A and B.

His moving observers test the clocks of the stationary system for
synchronization.  They send light from A to B and then back to A.  We
know from our omniscient position as readers that it is not going

to work:  Because of the motion of the rod while the light is
travelling, the time to go from A to B according to the stationary
system is now longer than it was when the rod was at rest in that
system, and the return time is now shorter.  (The round trip is also
shorter, as any first-year physics student should be able to show.)
Thus the clocks are not synchronized w.r.t. the moving observers.

(Note: I avoided the term "closing speed" so as not to cause Androcles
heart failure.)

How can they fix this problem?  They have to build their own clock
system. Their clocks must be re-synchronized.  In particular a moving
clock at B must be set to the time that Androcles ridicules: (t1+t2)/
2, in an obvious notation. Time is relative!

How can this be justified?  The biggest point that Androcles misses is
that the "moving" observers are entitled by his new Principle of
Relativity to consider themselves stationary and the other system as
moving backwards.  Therefore their synchronization should be just as
valid in their system as the original process in the "stationary
system."

In other words, Androcles missed the whole point of the exercise.

If he didn't have such a foul mouth and horrible personality, I would
say that Androcles is still a good person in spite of his error.  But
that would obviously be incorrect.

Uncle Ben

==============

I left in my text several typos -- which should be corrected for the
benefit of idiots -- and one more serious error: the good first-year
physics student will find that the round-trip time computed from the
stationary clocks is longer, not shorter, than the proper time. One
can see this immediately as v approaches c because of the (c-v) in the
denominator of the expression for the forward leg of the round trip.

Yep... He could work that out waiting for the horse
and carriage that goes by the school.


The calculation also shows (in 1905) the phenomenon of time dilation
for the first time in the AE paper. The moving clocks are slow w.r.t.
the stationary frame.

Maybe I need to hire a first-year physics student as an editor. -- No,
I'm not getting paid that much for the writing.

It might be sufficient to peek at what contemporary
physics students are reading.

<<It would be helpful if we could easily distinguish
those elements of Maxwell's equations which depend
on physics from those which only depend on coordinates.
In fact, we can achieve this by using what mathematicians
call vector field theory. This theory enables us to
write Maxwell's equations in a manner which is completely
independent of our choice of coordinate axes. As an added
bonus, Maxwell's equations look a lot simpler when
of eight first-order partial differential equations,
we only require four such equations within the context
of vector field theory. >>
"Preface"
http://farside.ph.utexas.edu/teaching/em/lectures/node4.html

By that technique equations for light can't
interfere with the fundamental notion that:

"ALL[1] inertial frames are totally equivalent
for the performance of ALL[1] physical experiments."
http://farside.ph.utexas.edu/teaching/em/lectures/node108.html


Sue...


Uncle Ben

[1] Shouting by Sue...

.

Relevant Pages

  • Re: Einsteins Train Gedanken Re-visited
    ... let's help Androcles sort out his scruffy ... There Einstein first raises the question, if clocks are synchronized ... he uses that postulate to define synchronization with light rays as ... rod now moving at v along with two moving observers at points A and B. ...
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  • Re: What are the SR predictions for these experiments??
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  • Re: What are the SR predictions for these experiments??
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  • Re: Einsteins Train Gedanken Re-visited
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    (sci.physics.relativity)
  • Re: Einsteins 1905 paper flawed from the start.
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