Re: Syncronized atomic clocks
From: Sam Wormley (swormley1_at_mchsi.com)
Date: 06/10/04
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Date: Thu, 10 Jun 2004 15:01:42 GMT
The Ghost In The Machine wrote:
>
> In sci.physics, Sam Wormley
> >
> > Whoa Ghost--The speed of light is constant!
> > http://scienceworld.wolfram.com/physics/SpeedofLight.html
>
> That's the theory, yes...I agree with it in general but
> would be curious as to how one can verify that c in deep
> space is the same as c on the Earth. (Presumably one can
> locate a binary star on the edge of a dust cloud, perhaps.)
>
Counter Point (and fact of our universe): there is a limit
to velocity called the speed of light. This has been known
for more than 90 years.
Ref: http://ldolphin.org/chistory.html
A Brief History of c
When the Danish astronomer Olaf Roemer (Philosophical
Transactions; June 25, 1677) announced to the Paris
Academie des Sciences in September 1676 that the
anomalous behavior of the eclipse times of Jupiter's inner
moon, Io, could be accounted for by a finite speed of light,
he ran counter to the current wisdom espoused by
Descartes and Cassini. It took another quarter century for
scientific opinion to accept the notion that the speed of
light was not infinite. Until then, the majority point of
view was that the velocity of light was infinite.
The Greek philosophers generally followed Aristotle's
belief that the speed of light was infinite. However, there
were exceptions such as Empedocles of Acragas (c.450
B.C.) who spoke of light, "travelling or being at any given
moment between the earth and its envelope, its movement
being unobservable to us," (The Works of Aristotle
translated into English, W.D. Ross, Ed.; Vol. III; Oxford
Press, 1931: De Anima, p. 418b and De Sensu, pp.
446a-447b). Around 1000 A.D., the Moslem scientists
Avicenna and Alhazen both believed in a finite speed for
light (George Sarton, Introduction to the History of
Science Vol. I; Baltimore, 1927; pp. 709-12). Roger Bacon
(1250 A.D.) and Francis Bacon (1600 A.D.) both accepted
that the speed of light was finite though very rapid. The
latter wrote, "Even in sight, whereof the action is most
rapid, it appears that there are required certain moments
of time for its accomplishment...things which by reason of
the velocity of their motion cannot be seen-as when a ball
is discharged from a musket" (Philosophical Works of
Francis Bacon; J.M. Robertson, Ed.; London, 1905; p. 363).
However, in 1600 A.D., Kepler maintained the majority
view that light speed was instantaneous, since space could
offer no resistance to its motion (Johann Kepler; Ad
Vitellionem paralipomena astronomise pars optica
traditur Frankfurt, 1804).
It was Galileo in his Discorsi..., published in Leyden in
1638, who proposed that the question might be settled in
true scientific fashion by an experiment over a number of
miles using lanterns, telescopes, and shutters. The
Accademia del Cimento of Florence reported in 1667 that
such an experiment over a distance of one mile was tried,
"without any observable delay" (Essays of Natural
Experiments made in the Academie del Cimento;
translated by Richard Waler, London; 1684; p. 157).
However, after reporting the experimental results,
Salviati, by analogy with the rapid spread of light from
lightning, maintained that light velocity was fast but finite.
Descartes (who died in 1650) strongly held to a belief in
the instantaneous propagation of light and, accordingly,
influenced Roemer's generation of scientists, who
accepted his arguments. He pointed out that we never see
the sun and moon eclipsed simultaneously. However, if
light took, say, one hour to travel from earth to moon, the
point of co-linearity of the sun, earth, and moon system
causing the eclipse would be lost and visibly so (Christiaan
Huygens, Traite de la Lumiere...; Leyden; 1690, pp. 4-6,
presented in Paris to the Academie Royale des Sciences in
1678). In 1678 Christiaan Huygens demolished Descartes'
argument by pointing out, using Roemer's measurements,
that light took (of the order of) seconds to get from moon
to earth, maintaining both the co-linearity and a finite
speed.
However, only Bradley's independent confirmation
published January 1, 1729 ended the opposition to a finite
value for the speed of light. Roemer's work, which had
split the scientific community, was at last vindicated. After
53 years of struggle, science accepted the observational
fact that light traveled at a finite speed. Until recently, that
finite speed has been generally been considered a fixed
and immutable constant of the universe in which we live.
Scientifically speaking, the velocity of light is the highest
known velocity in the physical universe. The present
value has been fixed (by definition) since 1967 and is
299,792.458 kilometers per second. Almost everyone
rounds this off to 3 X 10 (exp8) meters/second, or 186,000
miles/second. Electronics technicians often prefer to
remember the approximate speed of light as one foot per
nanosecond in air or vacuum-the distance light travels in
one-billionth of a second. In dielectric media the velocity
of light (electromagnetic waves) is slower than in the
vacuum of space.
by Barry Setterfield
1987
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