Re: SR's velocity addition -- ANY Experimental Evidence?

From: Jim Greenfield (greenfield_7_at_hotmail.com)
Date: 07/08/04 

Date: 7 Jul 2004 17:31:00 -0700

Timo Nieminen <timo@physics.uq.edu.au> wrote in message news:<Pine.LNX.4.50.0407071146170.7196-100000@localhost>...
> On Wed, 6 Jul 2004, Jim Greenfield wrote:
>
> > Timo Nieminen <timo@physics.uq.edu.au> wrote:
> > > On Tue, 5 Jul 2004, Jim Greenfield wrote:

> > > > Postulate of SR is that coordinates on a moving body get closer due to
> > > > increased velocity. OK?
> > >
> > > No.
> > >
> > > More like "the coordinates (x,t) of an event in an inertial coordinate
> > > system X are related to the coordinates (x',t') of the same event in
> > > inertial coordinate system X' by the Lorentz transforms."

By what stretch, are the ends of a stick/ train, an "event"?
> > >
> > > As a result the length of a moving object is measured to be different from
> > > the length of the same object when stationary.

Not by me! I add in the source velocity of the light which conveys the
information regarding the whereabouts of the stick's end, and thereby
ALWAYS get the same, correct answer.
> > >
> > > Do note that this actually predates special relativity. In the preceding
> > > theory, it was assumed that the moving object *actually shrinks*.
> > > Einstein's special relativity theory replaces this *actual shrinkage* with
> > > a reduction in the length as measured in the coordinate system in which
> > > the object is moving. Note that this reduction in measured length is
> > > second order in v/c.

Sam W and many co supprters of GR / SR mainatain that, unequivocably,
the shrinkage is "real". They produce the math to 'prove' it, and
claim multitudes of machines which have been designed to allow for
"shrinkage" at high speed
> > >
> > > This length contraction is not what an *observer* sees - the observer sees
> > > light that left the object at different times, depending on the distance
> > > to the different parts of the object. The coordinate system measures the
> > > locations of all parts of the object *simultaneously*. The observer
> > > actually looking at the object will generally see an increase or decrease
> > > in length of order v/c, depending on the direction of motion, which is
> > > most certainly an illusion.

Yes! The observer is mistaken. It follows to me, that a "mistake"
"proved correct" by maths, shows a VERY major flaw in that math.
> > >
> > > Feel free to consider the change in length as measured by a coordinate
> > > system an illusion as well. Certainly much more illusory than the actual
> > > physical shrinkage proposed by earlier theories.

Whether an image, and the information we perceive from that image (say
viewing a fast train), is altered by time of flight of photons, or the
direction from which they come, is intriguing (like art?), is nothing
but ab abstraction. What the REAL situation is / was / will be, should
always be worked through, keeping finite light speed at the forefront.
> > >
> > > Of course, the *proper length* of the object doesn't change at all. If
> > > you're happy to call "length" something other than that which you measure
> > > with a ruler, then you can call the proper length the "length".

So long as my ruler is inviolate (not "tuned" to SR), by all means.
> >
> > Thank you kindly. Your foregoing is pretty much what I have been
> > trying to get through to Sam W, Dirk v, Franz H, Al S and various
> > other DHR's for several months--- that the observed (or even measured
> > in selected frame) shrinkage of a body is an ILLUSION brought about by
> > finite light speed.
>
> Do note that the conventional definition of "length" is the distance
> between the two ends of the object when the positions of the two ends are
> measured simultaneously. This length does indeed change, and the
> abovementioned posters are indeed correct to say so.

Nyet
>
> As I wrote above, the most successful theory preceding Einstein's special
> relativity to explain observed electromagnetic phenomena assumed that this
> was a *real physical shrinkage*. In SR, it's a result of the way that
> measurements are made in a coordinate system.
>
> As I wrote, you can call this length contraction an illusion - if you are
> willing to define "length" as something other than that which is measured
> by rulers. But even if you do adopt a non-conventional definition of
> length, you still should not complain about others using the usual
> definition. And you should make it clear that you are using a *different*
> definition. It's the difference in definitions that can cause one person's
> "illusion" to be another's "real effect".
>
> Generally, explanations of special relativity are simplified. As you had
> shown very little inclination to learn about SR, as judging by your posts,
> you were mostly offered very simplified explanations ignoring some of the
> somewhat pedantic points above.
>
> As well as learning some of the physics that you have been loudly
> complaining about, it might be educational to learn some history as well.
> Had Einstein not published his theory in 1905, we'd still have the
> equivalent of special relativity with us, courtesy of Lorentz and
> Poincare.

They caused the initial (math), by using an impossibility in their
equations; the premise that distance, and therefore velocity, can be
less than zero
>
> As a logically self-consistent theory, SR needs to be assailed from the
> outside, by experiment or observation. You loudly support an emission
> theory of light. The experiments have been done. Null results, all.

Rubbish. Everytime you see a frequency change due to the motion of the
source (in vacuum) you are REALLY seeing c'=c+v
>
> > > > But when I look at fast moving heavenly
> > > > bodies, they do NOT suddenly change their distances apart when their
> > > > approaches change (pass each other).
> > >
> > > Well, why would they?
> >
> > This was reference to Sam W claim that the distance reduction (of a
> > travelling object) from its destination is REAL.
>
> The reduction of distance as measured in a coordinate system comoving with
> the body is real, yes.
>
> > So if two bodies are approaching at speed, EACH sees the other to be
> > closer.
>
> Sure, if you mean that each measures the other to be closer in their
> respective comoving coordinate systems as compared with, for example,
> their centre of mass coordinate system. Not quite the same as "see". You
> might want to sit down and calculate what they actually *see*, and
> separate optical effects from coordinate system effects.
>
> Why do you think that even the optical illusion results in a *sudden*
> change?
>
> > SW claims this a "real" effect.
>
> Where "real" is what you measure in your coordinate system, sure.

Did NASA rely on Cssini's "pilot" to calculate its position? (nwk)
>
> > As they pass, the situation
> > reverses, and suddenly both (according to that arguement) would be
> > further apart.
>
> Why? OK, I mentioned above optical illusions of order v/c as distinct from
> length contraction of order (v/c)^2, which are not what is measured by the
> coordinate system above.
>
> Why would the speed, as measured in their respective comoving coordinate
> systems change? That it does not trivially follows from the theory. The
> optical illusions are another matter (and do you have them the right way
> around?).
>
> > This quick change would be apparent, and of course the
> > sudden accellerations without energy changes are
> > impossible.
>
> Why would there be any acceleration, sudden or no? Accelerations are
> defined in terms of positions as measured in the coordinate systems, and
> there isn't any theoretically predicted acceleration, sudden or not.
>
> > .......although Sam W &Co. claims NO energy requirements
> > for shortening effects in SR.
>
> Of course there are no energy requirements, since they're just
> consequences of the way that measurements are made in coordinate systems.
>
> > > > If an observer on such a
> > > > (asteroid) "saw" that to be so, then he is MISTAKEN- the shortening
> > > > is an illusion
> >
> > I never expected to be on the same page as you, and yet my position
> > has NOT changed :-)
>
> Change it. You can't properly criticise a theory from a position of
> profound ignorance. Learn, then criticise.

Why learn something which based on obsession? One obsession being,
that because an observer cannot be at both ends of a rocket at once,
then it MUST shrink.
Personally, I don't give a monkeys how frustrated DHR's get, by not
being able to have information about a point's position 'instantly'.
The finite velocity of light will will one day be factored in to
observations, clearly showing that velocity does NOT cause shrinkage

Jim G

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