Re: The fallacy of affirming the consequent

[Pentcho Valev <pvalev@BAS.BG>]

Ken Caviness wrote:

> Pentcho Valev wrote:
>
> > However Einstein needs something different:
> >
> > B -> A, A, therefore B                                      /4/
> >
> > He proceeds in accordance with /4/ - builds Lorentz equations on B and
> > so creates the sequence (A therefore B therefore Lorentz equations) -
> > the illusion is that
> > Lorentz equations ultimately stem from A. In fact, A CAN be a corollary
> > of B or Lorentz equations, in accordance with /3/, but Lorentz equations
> > can BY NO MEANS be
> > deduced from A.
>
> I vividly remember an assignment in my freshman year Engineering Physics class
> where we were asked to _derive_ the Lorentz transformation equations from
> Einstein's postulates that the laws of physics and the speed of light are the
> same for all inertial observers.  I have since used this in my classes or as a
> homework assignment.  The only additional assumption needed is that the
> transformations be linear in all the variables (x,y,z,t,x',y',z',t').  That
> was handled by the statement that we would _first_ seek a set of
> transformation equations which was linear, but if necessary we could back off
> from that requirement.
>
> Briefly, if you let
>
> x = A x' + B y' + C z' + D t', y = E x' + ..., etc., the unknown constants can
> be identified by symmetry arguments and the requirement that the speed of
> light be measured by both primed and unprimed observers as c.  The Lorentz
> transformation falls out in your lap, i.e., the Lorentz equations can indeed
> "be deduced from A" + the additional requirement that the dependence be
> linear.

Let me make a suggestion. In the absence of additional ad hoc premises, the
postulate of the constancy of the speed of light (PCSL) is a corollary of Lorentz
equations, but the opposite is not true - Lorentz equations are NOT a corollary of
PCSL (combined with the principle of special relativity). This has an immediate
implication: Experimental verifications of Lorentz equations tell us nothing about
the validity of PCSL. In contrast, experimental verifications of PCSL are crucial
for Lorentz equations: experimental rejection of PCSL implies rejection of Lorentz
equations as well.
   By the way, speaking of the speed of the SAME  light in two inertial systems
implies that the speed is MEASURABLE in both systems. On the other hand, the
source            of light does not belong to at least one of the systems and I
wonder how the speed can     be measured in this case. Let the system be the
train, with two synchronized             clocks at the front and back ends. The
lightning flash first reaches the back end, stops the clock there but part of the
light passes through a hole, goes to the front clock and          stops it. What
speed would the person on the train measure - c or (c - v)? Is there an
essentially different way of measuring the speed of light in a system not
containing the source of light? Have such measurements ever been performed?

Pentcho Valev