Re: Is the speed of light really constant ?

From: Pax (pax1_at_whitesweb.com)
Date: 09/28/04 

Date: Tue, 28 Sep 2004 16:01:11 GMT

"Mich" <mich@efni.com> wrote in message
news:10kticflub4qr1f@corp.supernews.com...
>
> Bill Hobba <bhobba@rubbish.net.au> wrote in message
> news:nLm3d.36395$D7.23823@news-server.bigpond.net.au...
> >
> > "Mich" <mich@efni.com> wrote in message
> > news:10kqvt6hjnr0j70@corp.supernews.com...
> > >
> > > joseph levy <josephlevy1@compuserve.com> wrote in message
> > > news:cii0t6$o1p$1@ngspool-d02.news.aol.com...
> > > > We now know that the speed of light is not really
> > > > constant.
> > >
> > > As a layman, my understanding is very shallow.My difficulty with
the
> > > invariable speed of light lies in the fact that an observer seeing a
> > distant
> > > light source(star), can immediately change the light's frequency of
the
> > > source by changing his/her frame of reference relative to it(star). I
> fail
> > > to see how this can change the light's frequency without claiming a
> change
> > > in the light's speed.
> >
> > That is because you do not understand the physics involved. However
that
> is
> > easily corrected - many good books explaining it abound eg Taylor and
> > Wheeler - Space-time Physics.
> >
> > Bill
>
> Maybe. I have three books at hand;two text books, fundamentals of physics,
> and physics for scientist and engineers.They were on sale in a used book
> store.
> The other book is simply called Relativity, written by Einstein, which
> doesn't write about the dopple shift at all.
> In the first text book, physics for engineers, althought it writes in
> great details about the doppler effect for sound waves, the only thing it
> mentions concerning the doppler effect for light is "If a light source
moves
> with a speed v relative to an observer, there is a shift in the observed
> frequency analogous to the doppler effect for sound waves." It then goes
on
> to explain the equation for the shift. But what about when the observer
> changes his/her frame of reference? It doesn't mention this.
> In the book Fundamentals of Physics, only a small mention is made of a
> light doppler shift where the cause is by the observer moving relative to
> the source. "We would expect two observers, one moving towards a light
> source and the other moving away from it, to make two different
> determinations of the relative speed of light. This would be true for
sound
> waves, and produces the well known doppler effect.According to Einstein,
> though,each would determine the same result, c = 3 * 10 ^8 m/s."
> I can't help but notice, the book writes of as though the observer
moving
> relative to the light does "not" observe a doppler shift as seen in the
> statement "this would be true for sound waves, and produces the well known
> doppler effect."
>
> Andre

You've seen wind tunnel tests on television before, haven't you? They use
fine smoke to show air movement around an object in a wind tunnel. Have you
ever noticed how the smoke hits the front of the object, builds up slightly,
then rushes past and over the object to its rear? The same thing happens
with sound waves in air and light waves in space. The waves are compressed
(rise in pitch or spectrum) so that their wavelengths shorten if an object
is moving toward us, and stretch out (drop in pitch or spectrum) so that
their wavelengths lengthen if an object is moving away from us. This is the
Doppler Effect.

Edwin Hubble noted a "dopplering" of the light from distant galaxies in
1929, their light was all shifted toward the red (longer wavelength), and
the further away from us the galaxy was the faster it appeared to be
receding from us. The rate of acceleration, depending on distance from us,
was so stable a "constant" was discovered, Hubble's Constant (H).

Using his constant, Hubble arrived at an age for the Universe that was much
younger than that commonly held for the age of the Earth (he also calculated
that our galaxy, the Milky Way, was larger than all other galaxies). Other
astronomers, positive he was mistaken, adjusted the value of Hubble's
Constant in order to arrive at an age for the Universe more in line with
popular belief, 10 to 20 billion years.

One must wonder, if Hubble was considered on the one hand to be so right
then why was he also considered to be so wrong? He found a value of 150km
per second per 1,000,000 light years for H, however that has now been
revised down to 15-30km per 1,000,000 light years for H. That's a huge
revision, denoting a 70-85% error!

Hubble's Law (the cosmological velocity-distance law), which uses as its
basis Hubble's Constant, states that
velocity = H times distance,
the greater the distance of the galaxy, the faster it recedes. The fact of
this acceleration according to distance was never officially questioned, yet
it seems no one thought to apply it directly to Universal expansion... a
least until very recently. This is exceedingly strange, since astronomers
have been using Hubble's Constant for nearly three-quarters of a century.

Be well - Pax

.~*~._.~*~._.~*~._.~*~._.~*~._.~*~._.~*~._.~*~._.~*~.

What are ten years in the history of humanity? Must
not all those forces that determine the life of a man
be regarded as constant compared with such a trifling
interval? - Albert Einstein - Out of My Later Years

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