Re: Maxwell's derivation of the Speed of Light "c"
- From: "Sue..." <suzysewnshow@xxxxxxxxxxxx>
- Date: Sun, 04 Nov 2007 01:03:05 -0700
On Nov 3, 10:34 pm, Don Stockbauer <donstockba...@xxxxxxxxxxx> wrote:
On Nov 3, 7:19 pm, "hhc...@xxxxxxxxx" <hhc...@xxxxxxxxx> wrote:
On Nov 3, 7:09 pm, Sam Wormley <sworml...@xxxxxxxxx> wrote:
hhc...@xxxxxxxxx wrote:
I posted this a bit earlier on an old thread discussing the speed of
light, but since so many laymen appear confused about the factors that
determine and fix the velocity of light in free space, I believe that
a pointer to a very excellent article on the subject is appropriate.
http://en.wikipedia.org/wiki/A_Dynamical_Theory_of_the_Electromagneti...
Sorry about the math, but at this level of physics, it's difficult to
communicate the basic concept except through the use of vector math
notation.
If you skip to the last quarter of the article, you will find the
accepted solution that specifies the speed of light, "c", in free
space. Note that "c" is entirely determined by two parameters of
space, permittivity and permeability. Permittivity deals with the
electric field properties of space, and Permeability with the
magnetic. Combined, they define the velocity at which an
electromagnetic wave will propagate through space.
I hope in posting this that it helps at least one person.
Harry C.
According to Tom Potter:
"James Maxwell (1831-1879) formulated the concepts of permittivity
and permeability to serve as constants in his equations which
described most electro-magnetic behavior. Amazingly, using data
from experiments on capacitors and coils, he was able to predict
the existence of radio waves including their velocity. Maxwell's
books on electro-magnetics and "Matter and Motion" are powerful
reading and provide a much clearer view of reality than most
modern books".
Sam Wormley says: One can calculate the speed of light from
the permittivity and permeability of free space, for example,
but it is conventional and more useful to consider the speed
of light as a fundamental constant.- Hide quoted text -
- Show quoted text -
Sam, the convenience of knowing "c" to be roughly 3 X 10^8 Meter/
Second was not the point of my post, nor do I dispute that value. The
only reason that I posted this thread was because of the many
crackpots posting various speculative theories on the propagation
velocity of light on this newsgroup. I realize that you know better,
but evidently many of the newsgroup readers don't know the fundamental
facts of how this propogation value was established, how
electromagnetic waves propagate through a vacuum...and I know that you
do. Hence, what I post is not directed at you. It's simple
pontification of basic physics theory. Stay with me here. I'm simply
trying to get a few of the readers of this newsgroup to think, rather
than posting silly and fantasic theories.
The velocity of light depends on the permittivity and permeability,
hence it at least appears to me that "c" is a dependent, not an
independent variable. Change the value of permittively or
permeabililty, and "c" will change as we can experimentally observe.
Accordingly, the speed of light is not a fundamental constant unless
Maxwell was wrong -- something that I strongly doubt.
In fact this is precisely why the speed electromagnetic wave
propagation changes in some media, where the parameters of
permittivity and permeability differ from those in fee space. This is
precisely why there is a velocity factor associated with
electromagnetic wave propagation in a coaxial cable.or in water. The
values of permittivity and permeability in these mediums are different
from those encountered in free space (vacuum).
I hope that I am not being excessibe pedantic is differentiating the
speel of light in a media from that in free space, but I suspect you
know why I am doing this. "c" is the speed of light in free space
(e.g. a vacuum), but in a physical medium like water, glass,or coaxial
cable, the propagation velocity of an electromagnetic wave slows. If
it didn't, optical lenses would not work! :-) Again, this serves to
demonstrate the fact that the propagation velocity of any
electromagnetic wave is entirely depended on the permittivity and
permeability of the transmission media. In the vacuum of free space,
this translates to whay most physicists remember as 3 X 10^8 Meters/
Second. Were the physical parameter that determine the velocity
diffent, then "c" would have a different value.
Maxwell, the strange genius that he was, connected all of this
together. Damn, I wish I were 10% as intelligent as this guy was!
If you are fortunate enough to find a scan of Maxwells original
publication, please forward me a copy.
Harry C.
Harry C.
What is light moving relative to?
Ligh moves at c relative to the same thing water wave move relative to
.... the nearst interacting molecule of the media.
http://en.wikipedia.org/wiki/Free_space
http://www-ssg.sr.unh.edu/ism/what.html
http://web.mit.edu/8.02t/www/802TEAL3D/visualizations/light/index.htm
http://nobelprize.org/physics/articles/ekspong/index.html
Sue...
.
- References:
- Maxwell's derivation of the Speed of Light "c"
- From: hhc314@xxxxxxxxx
- Re: Maxwell's derivation of the Speed of Light "c"
- From: Sam Wormley
- Re: Maxwell's derivation of the Speed of Light "c"
- From: hhc314@xxxxxxxxx
- Re: Maxwell's derivation of the Speed of Light "c"
- From: Don Stockbauer
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