🚀 go-pugleaf

On Jun 18, 9:13 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote in
sci.physics.relativity:
> Henry Wilson, DSc wrote:
> > How can all the starlight in the universe
> > that is moving in our direction magically find a common speed if there is no
> > 'medium' in space that determines that speed?
>
> The same way that a straight line "magically finds" the shortest
> distance between two spatial points (over distances less than ~1000 km).
> That is, GEOMETRY.
>
> I don't know why the space-time geometry of the world we inhabit has
> this property, but experiments show that this model is one of the best
> and most widely-applicable descriptions of our world that have ever been
> discovered.
>
> This is not really a surprising result, to people who have actually
> studied the matter. Here's a simple explanation:
>
> Assume the world we inhabit is causal. That is, for a given point in
> space P and given time T, all phenomena located at P at time T can
> depend only on phenomena near P a short time before T. This implies that
> it is not possible for some object or influence to "zoom in from
> infinity" with infinite speed and affect any phenomena located at P at
> time T [#]. So there must be a finite upper bound on the speed of all
> objects and influences -- that's the only way to ensure they are near P
> a short time before T. Mathematically this implies that the only valid
> transformation group among inertial frames is the Poincaré group [@],
> which has the property that all objects and signals are restricted to
> speeds less than a universal maximum speed; experiments show that this
> universal speed limit is equal to the vacuum speed of light. The theory
> that describes this is known as Special Relativity, and experimentally
> it has been observed to be valid for all phenomena that have been tested
> under conditions where gravity can be ignored.

Experimental results should be interpreted, Honest Roberts. The
Doppler effect (shift in frequency) is unquestionable but it takes a
sane (non-Einsteinian) mind to say whether it is due to shift in
wavength (then no problem for Einstein's 1905 light postulate) or
shift in the speed of light (then Einstein's 1905 light postulate is
false). Consider a light source and an observer initially at rest
relative to each other. Then the observer suddenly starts moving, with
constant speed, towards the light source. The frequency unquestionably
shifts, but can you imagine the wavelength shifting as well? A sane
(non-Einsteinian) mind cannot imagine any shift in wavelength (the
wavelength can only be determined by the source and has nothing to do
with the movements of the observer) and concludes that the speed of
light has shifted, in accordance with the formula:

frequency = (speed of light)/(wavelength)

Pentcho Valev
pvalev@yahoo.com