🚀 go-pugleaf

On Nov 8, 11:28 am, Pentcho Valev <pva...@yahoo.com> wrote:
> On Nov 8, 9:14 am, Don Stockbauer <donstockba...@hotmail.com> wrote in
> sci.physics.relativity:
>
>
>
>
>
> > On Nov 8, 12:49 am, Pentcho Valev <pva...@yahoo.com> wrote:
>
> > > On 7 Nov, 21:01, Tom Roberts <tjroberts...@sbcglobal.net> wrote:
> > > > In SR, neither "length contraction"
> > > > nor "time dilation" are physical -- they are purely geometrical. A
> > > > moving ruler does not physically get any shorter, it is merely MEASURED
> > > > shorter by an observer relative to whom it is moving along its length.
> > > > Ditto for clock tick-rates.
>
> > > >         Simple example: take two meter sticks, A and B, and place
> > > >         them in a V on the ground. Project the end of each
> > > >         perpendicularly onto the other. The length of A projected
> > > >         onto B is less than 1 meter; the length of B projected
> > > >         onto A is likewise less than 1 meter. Yet NEITHER stick
> > > >         is physically shorter. This is easily recognizable as a
> > > >         geometric projection that does not affect the meter sticks
> > > >         at all. In SR, "length contraction" and "time dilation"
> > > >         are PRECISELY the same -- geometric projections that do
> > > >         not affect objects at all.
>
> > > Roberts Roberts you are paid for teaching that length contraction and
> > > time dilation are "purely geometrical", not "physical", and so teach
> > > your French brothers - Thibault Damour and Gilles Cohen-Tannoudji for
> > > instance. However most brothers in Einstein criminal cult teach the
> > > opposite Roberts Roberts - they are paid for explaining how a long
> > > train can be trapped inside a short tunnel, how a 80m long pole can be
> > > trapped inside a 40m long barn, and, what is most important Roberts
> > > Roberts, those brothers of yours tell the "story of what causes the
> > > particles to get closer together, and so what causes the rod to
> > > shrink":
>
> > >http://groups.google.ca/group/sci.physics.relativity/browse_frm/threa...
>
> > > Who gives the money for all those good salaries Roberts Roberts?
> > > Taxpayers in Einstein zombie world?
>
> > > Pentcho Valev
>
> > Only Napoleon held aloof. He had declared himself against the windmill
> > from the start.  One day, however, he arrived unexpectedly to examine
> > the plans. He walked heavily round the shed, looked closely at every
> > detail of the plans and snuffed at them once or twice, then stood for
> > a little while contemplating them out of the corner of his eye; then
> > suddenly he lifted his leg, urinated over the plans, and walked out
> > without uttering a word.
>
> A nice story but now you shall return to the problem your masters have
> not solved yet:
>
> http://ndpr.nd.edu/review.cfm?id=6603
> "There are many things I might be asking when I ask someone to explain
> length contraction. I might be asking, "Why do different inertial
> observers (who are not at relative rest) disagree about the length of
> a given (inertially moving) rod?" Or I might be asking, "Why is a
> moving rod shorter than its stationary counterpart (of the same proper
> length)?" Or I might be asking, "If you take a rod that is initially
> at rest (in your frame of reference), and accelerate it, why is it
> shorter after you accelerate it than it was before you accelerated
> it?"......I'm not sure what Brown thinks about geometrical answers to
> the first why-question, but he certainly thinks that GEOMETRICAL
> ANSWERS TO THE SECOND TWO WHY-QUESTIONS ARE BAD EXPLANATIONS. He
> thinks that good answers to these questions say something about the
> way in which the forces holding the parts of the rod together depend
> on velocity of the rod. Only that is a story of what causes the
> particles to get closer together, and so what causes the rod to
> shrink."
>
> Pentcho Valev- Hide quoted text -
>
> - Show quoted text -

  Strictly speaking, there is no such a thing as
length contraction * as an attribute of the IRF change*,
in my opinion.
  According to the Lorentz transformations, in the same
IRF, we must have simultaneously contraction AND dilatation,
depending on the sign of coordinates.
   Then, certainly, we should not talk any more of contraction,
but only of CHANGE, due to a chosen method of length
measurement.
     For the sake of clarity : moving objects can be
measured sending signals from one end of the object or
from the other end.
In one case results an apparent increase in length,
while in the other case an apparent contraction will
be registered.
    From here, the Lorentz transforms attempt to
give an answer as to what the "real" or "proper"
values would be in the moving frame.
And, they do use geometrical assumptions to do this.
  In this sense, the "contraction" is geometrical.
       Physical ?
No way! After acceleration at a moderate rate, all
bodies shall regain their "start dimensions" in a
very short time.
  Best regards, LL