Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

All those precious analyses should give an answer to the following
question:

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

Pentcho Valev

"Pentcho Valev" wrote in message
oups.com...
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

All those precious analyses should give an answer to the following
question:

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

What, is this nonsense still going on?! Sure in German as well as in common
English (and in many scientific publications) there is no difference between
"speed" and "velocity". And everyone in the sci.relativity group supposedly
knows that the "local" value of light speed depends on one's choice of
reference frame, and many do know it. It really belongs to the abc of GRT:
Einstein based his famous light bending calculation on the light speed
gradient in a gravitational field.
And I'm sure that I explained it to you, but you may have overlooked it.
Thus one last time: If you choose as your reference units those of outer
space, then the speed of light is *reduced* to *less* than 300000 km/s in a
gravitational field - otherwise, light would deflect the wrong way! Think
about it...
Is it clear now?

Harald

Pentcho Valev wrote:
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

All those precious analyses should give an answer to the following
question:

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

Pentcho Valev

Yes, but "globally", not locally. A (closer to the planet) sees the
*speed* of light at B (farther away from the planet) to be *higher*.
(And B sees the speed of light at A to be *lower*.)

But the the *local* values of c at A and at B are the same (3.10^8m/s).
I.e. A measures this value for the speed of a light ray inside his
spaceship, and B measures the same value for a ray of light inside
*his* spaceship.

Mahmoud In My Dinner Jacket wrote:
Pentcho Valev wrote:
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

All those precious analyses should give an answer to the following
question:

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

Pentcho Valev

Yes, but "globally", not locally. A (closer to the planet) sees the
*speed* of light at B (farther away from the planet) to be *higher*.
(And B sees the speed of light at A to be *lower*.)

Isn't it difficult to learn such idiocies by rote? How does A measure
the speed of light at B?

Pentcho Valev

Pentcho Valev wrote:
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Clearly, Einstein maintained that the SR principle that light has a
constant speed (or velocity) as valid under *some* condition. But under
what condition? The condition addressed specifically in GR: Gravity is
the pivot. If in the experiment gravity is weak compared to all other
"forces," it can be ignored, and in such a case SR is applicable as a
close approximation. SR is just an idealization which is very accurate
model in high-energy experiments, for example. Obviously, the transit
of light passed a star is dealing with an appreciable amount of gravity
over a "long" interval of time: thus gravity can't be ignored and GR is
the theory to use. In such a case, GR predicts that the path of light
is a curve in space.

The smaller the distance light (or particles other than light) travels
in the experiment, the smaller the effect of the bending of its path
("falling") due to gravity it will experience, especially relative to
other forces in the experiment. That's what is meant by the Light
Principle being valid locally, as opposed to having unrestricted
validity globally. The analogy to the curvature of the surface of a
sphere is compeling: the smaller the region one looks at on the
surface, the less evident is the curvature for practical
considerations. If the earth's surface were perfectly smooth, it would
locally "look flat." What that means is that if you could stand on a
spot on that surface and shrink yourself to ever smaller size, in time
the surface you stand on would be indistinguishable from a flat plane.
That's what is meant by 'locally' in the differential geometric sense.

Consider this: Someone trying to hit a coffee can at three feet with a
baseball in an overhand speed throw can ignore gravity in his or her
aim; someone throwing a baseball 30 feet away at the same coffee can
cannot. Thus, the pitcher who only throws three feet away is justified
in promoting the Principle of Ignorable Gravity. However, this is a
principle without unlimited validity! It has a limited domain of
applicability.

Undoubtedly, one of the greatest misconceptions lay people have about
real physics is how often real physics relies on the use of
approximations and idealized models.

Pentcho Valev wrote:
CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

Sure, depending on the physical conditions of the measurement. It can
also be less than "300000 km/s" (by which I assume you really mean the
standard value for c). And this can happen even for an accelerated
observer in a region without any significant gravitation (e.g. in
Minkowski spacetime).

GR predicts that measurements of the speed of light in a
locally-inertial frame using standard clocks and rulers will always
obtain the value c (to within the accuracy that the local frame is
inertial). But if you use non-standard rulers or clocks, or measure over
a non-local distance, or in a non-inertial frame, then you can obtain a
different value; perhaps wildly different. For instance, in an
accelerated rocketship in Minkowski spacetime one could measure an
infinite value for the speed of light; or a zero value, or even crazier
values....


BTW the only identifiable "Zombie" here is Pentcho Valev himself -- he
simply refuses to learn modern physics, and keeps posting silly
statements (like this one). Why he thinks he is "two zombies" is not
clear....


Tom Roberts

"Pentcho Valev" wrote in message oups.com...
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

Porco Valev does not know the differences between
- speed and velocity
- local and global
- inertial and non-inertial
- implication and equivalence
- science and religion
- himself and a zombie

The list seems to grow - which is nice.

Dirk Vdm

Pentcho Valev wrote:
Mahmoud In My Dinner Jacket wrote:
Pentcho Valev wrote:
Albert Einstein, "Relativity", Chapter 7: "There is hardly a simpler
law in physics than that according to which light is propagated in
empty space. Every child at school knows, or believes he knows, that
this propagation takes place in straight lines with a VELOCITY c=300000
km/s."

Chapter 22: "...the law of the constancy of the velocity of light in
vacuo, which constitutes one of the two fundamental assumptions in the
special theory of relativity and to which we have already frequently
referred, cannot claim any unlimited validity. A curvature of rays of
light can only take place when the VELOCITY of propagation of light
VARIES WITH POSITION."

Tom Roberts: "AFAIK Einstein basically thought in German, which does
not have different words for "speed" and "velocity" ("die
Geschwindigkeit" is used for both). Certainly his "velocity of
propagation" could be phrased as "speed of propagation" without
changing the underlying physics."

Sam Wormley and Dirk Van de moortel: "Valev confuses *velocity* of
light with *speed* of light!", "The fact that Valev doesn't understand
the difference between speed and velocity." etc. (repeated many times).

All those precious analyses should give an answer to the following
question:

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?

Pentcho Valev

Yes, but "globally", not locally. A (closer to the planet) sees the
*speed* of light at B (farther away from the planet) to be *higher*.
(And B sees the speed of light at A to be *lower*.)

Isn't it difficult to learn such idiocies by rote?

You're telling me! I had to train hard for six years to qualify as a
DI (Doctor of Idiocy). But any fool can be sensible.

How does A measure the [local value of the] speed of light at B?

He doesn't. B does.

Pentcho Valev

Pentcho Valev wrote:
[..]

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?


Well Tom said Yes, depending on experimental parameters, but I'm going
to give a qualified no:

Not if by SOL you mean the instaneous speed.

Sure you can get from point A to point B as fast as you want using e.g.
expanding or curved manifolds but at every point along the way the
instaneous speed of light is c.

Cheers - shev

"shevek" wrote in message
ups.com...

Pentcho Valev wrote:
[..]

CAN THE SPEED OF LIGHT EXCEED 300000 km/s IN A GRAVITATIONAL FIELD?


Well Tom said Yes, depending on experimental parameters, but I'm going
to give a qualified no:

You are not qualified.

Not if by SOL you mean the instaneous speed.

SOL = sqrt(dx^2 +dy^2+dz^2)/dt.
That's instantaneous VELOCITY. Speed is the magnitude of velocity,
there is no such word as "instaneous", you are definitely not qualified.


Sure you can get from point A to point B as fast as you want using e.g.
expanding or curved manifolds but at every point along the way the
instaneous speed of light is c.

Cheers - shev

Sure, have another drink. Cheers.
Androcles