Re: Fact
From: Tom Roberts (tjroberts_at_lucent.com)
Date: 03/02/05
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Date: Wed, 02 Mar 2005 09:54:11 -0600
Paulps wrote:
> Some simple facts.
If you seriously want to do physics and avoid nonsense, you must be much more
careful about not labeling your personal beliefs as "fact".
> a) The speed of light (SOL) is constant in the medium of vacuum and as such
> is used as constant.
OK. Remember that what is actually measured is the speed of light in vacuum
relative to the measuring apparatus. We find that no matter how the apparatus is
oriented, or how it moves relative to objects like the earth and sun, the
measured value is constant (after accounting for any non-inertial motions of the
apparatus).
BTW nobody else calls vacuum a "medium". Be aware that your nonstandard usage
will probably confuse others (and perhaps/probably yourself). Calling vacuum a
"medium" does not make it one.
> b) The SOL is independent of the velocity of the source with respect to the
> vacuum/medium.
For an optical medium this is clear and observable[#]. For vacuum you need to
explain how "speed relative to vacuum" makes sense and can be measured (at least
in principle). This directly implies you must specify how to measure the speed
of an apparatus "relative to vacuum". That will be quite difficult, as all
measurements of speed are relative to the measuring apparatus, and vacuum has no
apparatus....
[#] But, of course, nobody measures speeds relative to the medium.
What is measured is either speed in the medium relative to the
apparatus, or speed relative to the apparatus and speed of the
medium relative to the apparatus. In this last case some theory
is needed to convert the two measurements into a speed relative
to the medium.
With that last point of the footnote in mind, what you need to define and
describe is a measurement of the speed of vacuum relative to an apparatus. Good
luck....
> c) The observer can from observation of the deviation frequency of light
> with a known frequency, determine their velocity with respect to the vacuum
> that the light is constant in by a spectrophotometer and computation.
This has the same difficulty mentioned above. In fact, as I mentioned above,
speed of light measurements in vacuum obtain the same value independent of
motion of the apparatus. Measurements of frequency shifts depend on a number of
things, including gravitational potentials and relative velocity of detector
relative to source.
But none of that can be described as "relative to vacuum" -- in every case there
is a physical apparatus relative to which measurements are made.
> d) Many of the examples posted to this group and in books fail to take
> account of the above facts.
That's OK, because they are not really facts.
> e) There are some resident trolls on this group that either though intent or
> misunderstanding try to obscure these facts
"Never attribute to malice what can be explained by incompetence." [attribution
lost, possibly R.A.Heinlein] In this case, your inability to identify actual facts.
Tom Roberts tjrobverts@lucent.com
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