"J?rgen Clade" wrote in message om...
EL,

...chicken poop.
...****...chicken
poop

Is this your usual way of discussing? You should not only learn some
physics, but also some manners.

[possibly posted twice - sorry, news server problem]

Impossible.
http://users.pandora.be/vdmoortel/di...rsenLogic.html
Look at the "interesting follow-ups" at the bottom ;-)
Enjoy...

Dirk Vdm

(J?rgen Clade) wrote in message . com...
EL,

...chicken poop.
...****...chicken
poop

Is this your usual way of discussing? You should not only learn some
physics, but also some manners.

regards,
Jürgen

[EL]
Are you accusing me of not recognising chicken **** when I see it?
Then who do you suggest can teach me physics if you all seem to be
chicken that has no freaking idea about any physics else than
excreting ****.?

If you had had the knowledge required to teach a professor then
certainly I do have the manner with which I should address such a
master.

I am really sorry to have offended you, and I never meant to offend
you in retaliation to being offended by your post.
Most probably you did not intentionally mean to offend me except that
there is nothing you can do about yourself being offensive.

Try posting science and I shall show you elite manners.

Post the same chicken **** you posted and I shall identify it on the
spot.

EL

wrote in message news: ...
I'll add here as a comment that the issue of group velocity is
generally misunderstood, perhaps due to the fact that lower level
textbooks don't explain it well. Group velocity *is not* signal
velocity. Under some circumstances, when the dependence of phase
velocity on frequency over the bandwidth of the signal is weak, group
velocity is a good approximation to signal velocity over distances
short enough so that the pulse shape does not change appreciably in
propagation. That's all. The conditions listed above are reasonably
well satisfied in most practical situations, but they totally fail
under anomalous dispersion situation.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

You're aware of the discussions on sci.physics.relativity that to
determine if a signal travelled superluminally what would be required
is a round-trip measurement. This is because of the uncertainty of
synchronizing clocks in two different locations. The standard SR
method of using light-signals requires the assumption of the constancy
of the one-way speed of light. [1]
I was interested to see that in some descriptions of the experiment
of Wang et.al. using lasers in cesium gas, that the light pulse was
said to exit the chamber before it entered:

"Can c, the speed limit of the universe, the speed of light in vacuum,
be exceeded? In July, 2000, the science-oriented news media were full
of reports that pulses of laser light had broken the speed-of-light
barrier. Physicists L. J. Wang, A. Kuzmich, and A. Dogarliu of the
NEC Research Institute in Princeton, NJ, had a paper about to be
published in the prestigious journal Nature describing an experiment
in which not only had laser pulses traveled faster than light, but had
actually emerged from the apparatus before they had entered it." [2]

It occurs to me that this is what would appear to happen if the
entrance and exit were synchronized using light signals but the actual
signal to be measured was traveling superluminally or if light signals
provided an inaccurate means of synchronizing clocks. What would be
needed to see if the signal pulse was being propagated superluminally
would be to have the pulse reflected back to the source and seeing if
the total travel time was less than the time for light to make the
round trip.

Another experiment might have made such round trip measurements.
These were experiments by Ranfagni et.al. of microwaves propagating in
a wave guide:

"In the new experiments, led by Anedio Ranfagni of the Italian
National Research Council in Firenze, the setup looks innocent enough:
The team sent microwaves (3.5 cm wavelength) through a narrow,
ring-shaped opening onto a large and nearby focusing mirror, which
collimated the waves into a beam propagating back from the mirror,
beyond and behind the source. They "modulated" the microwaves with
rectangular pulses (sharp "amplify" and "attenuate" commands, in rapid
succession) and detected the pulses at positions between 30 and 140 cm
from the source, along the beam axis. The slope of their plot of
arrival times vs. distance led to an apparent propagation speed of 5
to 7% above c, although beyond about 1 m, the speed approached c, all
of which agreed with previous predictions." [3]

The experimenters claim some speeds exceeding c in the reflected
waves but it is difficult to tell here if any of these speeds are for
a round trip signal back to the source.


Bob Clark



1.)Conventionality of Simultaneity
http://plato.stanford.edu/entries/sp...e-convensimul/

2.)Faster-than-Light Laser Pulses?
by John G. Cramer
http://www.npl.washington.edu/AV/altvw105.html

3.)Faster than a Speeding Light
http://focus.aps.org/story/v5/st23

In article , (Robert Clark) writes:
wrote in message news: ...
I'll add here as a comment that the issue of group velocity is
generally misunderstood, perhaps due to the fact that lower level
textbooks don't explain it well. Group velocity *is not* signal
velocity. Under some circumstances, when the dependence of phase
velocity on frequency over the bandwidth of the signal is weak, group
velocity is a good approximation to signal velocity over distances
short enough so that the pulse shape does not change appreciably in
propagation. That's all. The conditions listed above are reasonably
well satisfied in most practical situations, but they totally fail
under anomalous dispersion situation.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

You're aware of the discussions on sci.physics.relativity

I'm certainly not aware of any discussions on sci.physics.relativity,
nor do I have any interest in these.

that to
determine if a signal travelled superluminally what would be required
is a round-trip measurement. This is because of the uncertainty of
synchronizing clocks in two different locations. The standard SR
method of using light-signals requires the assumption of the constancy
of the one-way speed of light. [1]
I was interested to see that in some descriptions of the experiment
of Wang et.al. using lasers in cesium gas, that the light pulse was
said to exit the chamber before it entered:

"Can c, the speed limit of the universe, the speed of light in vacuum,
be exceeded? In July, 2000, the science-oriented news media were full
of reports that pulses of laser light had broken the speed-of-light
barrier. Physicists L. J. Wang, A. Kuzmich, and A. Dogarliu of the
NEC Research Institute in Princeton, NJ, had a paper about to be
published in the prestigious journal Nature describing an experiment
in which not only had laser pulses traveled faster than light, but had
actually emerged from the apparatus before they had entered it." [2]

It occurs to me that this is what would appear to happen if the
entrance and exit were synchronized using light signals but the actual
signal to be measured was traveling superluminally or if light signals
provided an inaccurate means of synchronizing clocks. What would be
needed to see if the signal pulse was being propagated superluminally
would be to have the pulse reflected back to the source and seeing if
the total travel time was less than the time for light to make the
round trip.

Another experiment might have made such round trip measurements.
These were experiments by Ranfagni et.al. of microwaves propagating in
a wave guide:

"In the new experiments, led by Anedio Ranfagni of the Italian
National Research Council in Firenze, the setup looks innocent enough:
The team sent microwaves (3.5 cm wavelength) through a narrow,
ring-shaped opening onto a large and nearby focusing mirror, which
collimated the waves into a beam propagating back from the mirror,
beyond and behind the source. They "modulated" the microwaves with
rectangular pulses (sharp "amplify" and "attenuate" commands, in rapid
succession) and detected the pulses at positions between 30 and 140 cm
from the source, along the beam axis. The slope of their plot of
arrival times vs. distance led to an apparent propagation speed of 5
to 7% above c, although beyond about 1 m, the speed approached c, all
of which agreed with previous predictions." [3]

The experimenters claim some speeds exceeding c in the reflected
waves but it is difficult to tell here if any of these speeds are for
a round trip signal back to the source.

Actually all the above experiments yield results fully consistent with
the existing theoretical predictions, based on classical
electrodynamics (even QM is not really required) and fully consisten
with relativity. You should read the scientific publications, not
writeups in popular media. There are all sorts of funny htings you
can do with pulses which change shape across small distnaces.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

Robert Clark:
wrote in message news: ...
I'll add here as a comment that the issue of group velocity is
generally misunderstood, perhaps due to the fact that lower level
textbooks don't explain it well. Group velocity *is not* signal
velocity. Under some circumstances, when the dependence of phase
velocity on frequency over the bandwidth of the signal is weak, group
velocity is a good approximation to signal velocity over distances
short enough so that the pulse shape does not change appreciably in
propagation. That's all. The conditions listed above are reasonably
well satisfied in most practical situations, but they totally fail
under anomalous dispersion situation.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

You're aware of the discussions on sci.physics.relativity that to
determine if a signal travelled superluminally what would be required
is a round-trip measurement.

That is not the case.

This is because of the uncertainty of synchronizing clocks in
two different locations.

It's completely unnecessary to synchronize anything.

(Bilge) wrote in message ...
Robert Clark:
wrote in message news: ...
I'll add here as a comment that the issue of group velocity is
generally misunderstood, perhaps due to the fact that lower level
textbooks don't explain it well. Group velocity *is not* signal
velocity. Under some circumstances, when the dependence of phase
velocity on frequency over the bandwidth of the signal is weak, group
velocity is a good approximation to signal velocity over distances
short enough so that the pulse shape does not change appreciably in
propagation. That's all. The conditions listed above are reasonably
well satisfied in most practical situations, but they totally fail
under anomalous dispersion situation.

Mati Meron | "When you argue with a fool,
| chances are he is doing just the same"

You're aware of the discussions on sci.physics.relativity that to
determine if a signal travelled superluminally what would be required
is a round-trip measurement.

That is not the case.

This is because of the uncertainty of synchronizing clocks in
two different locations.

It's completely unnecessary to synchronize anything.

It is well known among researchers in the foundations of relativity
the need to synchronize clocks at two locations for comparing times at
those locations.
See this post by Stephen Speicher:

From: Stephen Speicher )
Subject: Speed of light
Newsgroups: sci.physics.research, sci.physics.relativity
Date: 2003-06-24 20:06:03 PST
http://groups.google.com/groups?selm...st.localdomain


Bob Clark

(Bilge) wrote in message ...

It's completely unnecessary to synchronize anything.

[EL]
Hi Bilge.

Why is it so difficult for people to imagine group velocities as wave
envelopes!

All decent empirical wave-group-velocity measurements show that they
are much lower than phase velocity in the same dispersive medium.

I wish to make an analogy to establish a law.

When many people walk in a corridor while their legs are not equal in
length and their steps are not synchronized the group velocity of the
crowd is obviously slower than the fastest person in that crowd.

When six sportsmen are rowing a boat the speed of that boat is the
same as the collective speed of that synchronized group.

The envelope of the rowing mechanics may not exceed the speed of the
boat and the boat tip-front must lead at all times and never be
exceeded.

EL

J\"urgen Clade wrote:
EL,

...chicken poop.
...****...chicken
poop

Is this your usual way of discussing? You should not only learn some
physics, but also some manners.

Don't let irritate, if this man leaves some farts. He is only a chemist,
but he sees more than lots of paid physicists. See also
http://home.t-online.de/home/Ulrich....z/article2.txt
(Reading that, you may better understand the subject of this thread.)

Regards
Ulrich Bruchholz

On 25 Oct 2003 03:57:23 -0700, (EL) wrote:

(Bilge) wrote in message ...

It's completely unnecessary to synchronize anything.

[EL]
Hi Bilge.

Why is it so difficult for people to imagine group velocities as wave
envelopes!

All decent empirical wave-group-velocity measurements show that they
are much lower than phase velocity in the same dispersive medium.

Except in negatively-dispersive media, where both theory and
experiment show the opposite.

- Randy

[EL]
Thank you dear Ulrich, I know myself that I am an old ranting fart,
but I still appreciate your testimony.


ueb wrote in message ...
J\"urgen Clade wrote:
EL,

...chicken poop.
...****...chicken
poop

Is this your usual way of discussing? You should not only learn some
physics, but also some manners.

Don't let irritate, if this man leaves some farts. He is only a chemist,
but he sees more than lots of paid physicists. See also
http://home.t-online.de/home/Ulrich....z/article2.txt
(Reading that, you may better understand the subject of this thread.)

Regards
Ulrich Bruchholz