On May 4, 4:11 pm, Mike wrote:
On May 4, 2:05 am, Koobee Wublee wrote:

On May 3, 8:37 am, Tom Roberts wrote:

Tom Van Flandern wrote:
The premises that arise from logic alone rather than from experiments
or observations or philosophy or mathematics include these:
** Causality: Every effect has an antecedent, proximate cause.
** Creation: No creation ex nihilo; and no demise ad nihil

This approach to science was abandoned during the Renaissance, when it
was learned CONCLUSIVELY that this approach does not describe the world
we actually inhabit. In particular, your statements here are VASTLY too
imprecise to be useful. And they are not valid in modern physics:

Observing an effect without knowing a cause is not understanding the
issues involved. shrug

I agree if, and only if, there is a cause. If a cause is not there or
necessary then it is an empty statement.

Causes, are also first or final. Scholastic philosophy was based on
final causes and religion of first causes. Which causes are you for
KW?



** No theory of physics expressed in terms of differential equations
has your NAIVE "causality". Such equations describe correlations,
but correlation is not causation.

Speed of gravity is not an issue of causality. It is strictly an
issue of how fast a change in gravitational effect can propagate.
According to SR, the intuitive conjecture is that the speed of gravity
is the same as the speed of light. The speed of light is explained
definitively and thoroughly by the Maxwell’s equations. However, any
of the mathematics involved in GR does even describe what the speed of
gravity is. The field equations do not tell you how gravitational
waves propagate. Believing it otherwise is a myth. Mysticism is not
wisdom.

There is no such thinmg a "speed of gravity" like there is no such
thing as "speed of a smile".


"speed of a smile" exists. If you can't react
with a smile almost instantaneously to a
clever joke, then you are a retard :-)

On May 4, 11:10*am, Tom Roberts wrote:
Juan R. González-Álvarez wrote:
Tom Roberts wrote on Sat, 03 May 2008 15:37:22 +0000:
In particular, your statements here are VASTLY too
imprecise to be useful. And they are not valid in modern physics:
* ** No theory of physics expressed in terms of differential equations
* * *has your NAIVE "causality". Such equations describe correlations,
* * *but correlation is not causation.

Almost all relativists invoke the term *causality* (meaning causation) to
select retarded potentials as physical (they also use this term)
solutions to differential equations.

I'm merely pointing out that his NAIVE causality is not included in ANY
theory of physics expressed as differential equations. The choice of
retarded vs advanced potentials is boundary conditions, not "causality",
and one must of course select the one that matches what is observed in
the world we inhabit -- that naive causality is an APPROXIMATION, but is
woefully inadequate to specify a theory of physics.

* ** quantum field theory most definitely has what you call "creation
* * *ex nihlo" and "demise ad nihil".

Surely it does not, Tom.

Particle pairs pop in and out of existence spontaneously. The quantum
vacuum clearly does what he calls "creation ex nihlo" and "demise ad
nihil".

Perhaps if you would learn what science actually is you would not keep
repeating the same mistakes.

A small problem is you have not the exclusive of the definition of
science, even if you believe you have one.

Making up "principles" like Van Flandern does has not been part of ANY
definition of science, since the middle ages.

They say before you make suggestion to your neihgbor to watch his
house you must watch yours.

Yes, TVF alludes to some pretty wired principles. But before bushing
TVF, think about the wired principles you worship every day you get up
from bed:

http://casa.colorado.edu/~ajsh/sr/postulate.html

1. "Space and time form a 4-dimensional continuum".

Give us a break man.

2. "There exist global spacetime frames with respect to which
unaccelerated objects move in straight lines at constant velocity".

Idiots. Such frames cannot be proven to exist. It's worse than TVF's
causality, which ar least is some type of naive principle.

This second principle of SR is completely metaphysical, a gross joke
for children under the age of 2.

3. "The speed of light c is a universal constant, the same in any
inertial frame".

brrrroooooooo, time to get out of this bar parking lot before the
bouncers get out

4. "The laws of physics are the same in any inertial frame, regardless
of position or velocity".

Laws of physics? This sounds worse than creation ex nihilo, which
although a naive principle, at least would be common sense to some
poeple. What tha hell is a law of physcis and why that hell must be
the same in any inertial frame and where tha heel, those inertial
reference frames are any way, and if you cannot find any, what value
does this principle have anyway, other than generating a whole foken
class of paradoxes cookoo people have been trying to solve since
insanity hit science in 1906.

Hey, is the bug dead, smashed by the rivet, or not?

ok, tomorrow when I go to work, I will say how beautiful and elegant
are SR and GR otherwise I risk getting fired or losing my grants, or
even been called anti-democratic.


Mike










Tom Roberts

On May 4, 11:31*am, Albertito wrote:
On May 4, 4:11 pm, Mike wrote:





On May 4, 2:05 am, Koobee Wublee wrote:

On May 3, 8:37 am, Tom Roberts wrote:

Tom Van Flandern wrote:
* *The premises that arise from logic alone rather than from experiments
or observations or philosophy or mathematics include these:
** Causality: Every effect has an antecedent, proximate cause.
** Creation: No creation ex nihilo; and no demise ad nihil

This approach to science was abandoned during the Renaissance, when it
was learned CONCLUSIVELY that this approach does not describe the world
we actually inhabit. In particular, your statements here are VASTLY too
imprecise to be useful. And they are not valid in modern physics:

Observing an effect without knowing a cause is not understanding the
issues involved. *shrug

I agree if, and only if, there is a cause. If a cause is not there or
necessary then it is an empty statement.

Causes, are also first or final. Scholastic philosophy was based on
final causes and religion of first causes. Which causes are you for
KW?

* ** No theory of physics expressed in terms of differential equations
* * *has your NAIVE "causality". Such equations describe correlations,
* * *but correlation is not causation.

Speed of gravity is not an issue of causality. *It is strictly an
issue of how fast a change in gravitational effect can propagate.
According to SR, the intuitive conjecture is that the speed of gravity
is the same as the speed of light. *The speed of light is explained
definitively and thoroughly by the Maxwell’s equations. *However, any
of the mathematics involved in GR does even describe what the speed of
gravity is. *The field equations do not tell you how gravitational
waves propagate. *Believing it otherwise is a myth. *Mysticism is not
wisdom.

There is no such thinmg a "speed of gravity" like there is no such
thing as "speed of a smile".

"speed of a smile" exists. If you can't react
with a smile almost instantaneously to a
clever joke, then you are a retard :-)- Hide quoted text -

- Show quoted text -

You got the point. A retard is one that reacts instantenuously.

Mike

Tom Roberts wrote on Sun, 04 May 2008 10:10:36 -0500:

Juan R. González-�lvarez wrote:

Almost all relativists invoke the term *causality* (meaning causation)
to select retarded potentials as physical (they also use this term)
solutions to differential equations.

The choice of
retarded vs advanced potentials is boundary conditions, not "causality",

Either you are not reading or just lying.

It is well-known that textbooks and papers *often* invoke *causality* to
select the retarded potentials:

http://adsabs.harvard.edu/abs/1992AmJPh..60..465A

(\blockquote
The use of retarded potentials in solving the wave equation is usually
justified on physical grounds or else by an appeal to *causality*.
)

Emphasis mine.

Moreover, in some sense, it is wrong to speak about "boundary conditions"
for that case.

** quantum field theory most definitely has what you call "creation
ex nihlo" and "demise ad nihil".

Surely it does not, Tom.

Particle pairs pop in and out of existence spontaneously. The quantum
vacuum clearly does what he calls "creation ex nihlo" and "demise ad
nihil".

But you are making a beginner mistake because a quantum vacuum is not
empty and Tom van Flandern's "creation ex nihlo" refers to creation out
from nothing, or like Tom van Flandern would probably say: "empty space".

The quantum vacuum of quantum field theory is other thing carrying energy
momenta, correlations, fluctuations, and populated with virtual particles:

http://en.wikipedia.org/wiki/Vacuum_state

(\blockquote
According to present-day understanding of what is called the vacuum
state or the quantum vacuum, it is "by no means a simple empty
space"[1], and again: "it is a mistake to think of any physical vacuum
as some absolutely empty void."[2]
)

A small problem is you have not the exclusive of the definition of
science, even if you believe you have one.

Making up "principles" like Van Flandern does has not been part of ANY
definition of science, since the middle ages.

That is your belief Tom, just that. Like or not like it, science is that
is published in textbooks, journals and discussed at conferences.


--
http://canonicalscience.org/en/misce...guidelines.txt

Juan R. González-�lvarez wrote:
Tom Roberts wrote on Sun, 04 May 2008 10:10:36 -0500:
The choice of
retarded vs advanced potentials is boundary conditions, not "causality",

Note the quotation marks -- I was using the word "causality" in VAN
FLANDERN'S SENSE.


Either you are not reading or just lying.

Neither. You did not read what I wrote carefully enough.

It is well-known that textbooks and papers *often* invoke *causality* to
select the retarded potentials:
http://adsabs.harvard.edu/abs/1992AmJPh..60..465A
(\blockquote
The use of retarded potentials in solving the wave equation is usually
justified on physical grounds or else by an appeal to *causality*.
) Emphasis mine.

Sure. But there is a GREAT BIG PUN involved, and the word "causality"
here does NOT mean the same thing as when I used it IN VAN FLANDERN'S SENSE.


Moreover, in some sense, it is wrong to speak about "boundary conditions"
for that case.

Not really. It is boundary conditions applied to the Green's function.
This _IS_ how we use the language.


** quantum field theory most definitely has what you call "creation
ex nihlo" and "demise ad nihil".
Surely it does not, Tom.
Particle pairs pop in and out of existence spontaneously. The quantum
vacuum clearly does what he calls "creation ex nihlo" and "demise ad
nihil".

But you are making a beginner mistake because a quantum vacuum is not
empty and Tom van Flandern's "creation ex nihlo" refers to creation out
from nothing, or like Tom van Flandern would probably say: "empty space".

I was discussing VAN FLANDERN'S statements, not QFT. I merely pointed
out that QFT violates his statements. Yes, there are subtleties, but
they, like the above, involve PUNS on the words used. Your statements
here do not use the words in the same way Van Flandern uses them.

In particular, those virtual pairs DO NOT EXIST in the vacuum BEFORE
they "popped out of the vacuum", and no other contents of the vacuum
"caused" them to "pop out". This _IS_ what VAN FLANDERN means by
"creation ex nihlo" -- even though the vacuum is not "empty", his phrase
applies.


A small problem is you have not the exclusive of the definition of
science, even if you believe you have one.
Making up "principles" like Van Flandern does has not been part of ANY
definition of science, since the middle ages.

That is your belief Tom, just that. Like or not like it, science is that
is published in textbooks, journals and discussed at conferences.

Nowhere is science related to making claims about the world and then
expecting Nature to obey those claims. That is what Van Flandern is
trying to do, and that simply is not science. shrug


Tom Roberts

Tom Roberts wrote on Mon, 05 May 2008 09:35:50 -0500:

Juan R. González-�lvarez wrote:
Tom Roberts wrote on Sun, 04 May 2008 10:10:36 -0500:
The choice of
retarded vs advanced potentials is boundary conditions, not
"causality",

Note the quotation marks -- I was using the word "causality" in VAN
FLANDERN'S SENSE.

Tom van Flandern did a remark about causality, Every effect has an
*antecedent* cause.

That is the meaning taken in textbooks when selecting the retarded
potentials. It is believed that effects precede the cause for advanced
potential.

Moreover, in some sense, it is wrong to speak about "boundary
conditions" for that case.

Not really. It is boundary conditions applied to the Green's function.
This _IS_ how we use the language.

Speaking about boundary conditions in the four dimensional space is
really wrong thing to do. Dynamical questions, causality, and other
issues are better solved in the 3+1 formalism.

I was discussing VAN FLANDERN'S statements, not QFT. I merely pointed
out that QFT violates his statements.

You did a beginner mistake when said that quantum field theory has
"creation ex nihilo" and "demise ad nihil".

In particular, those virtual pairs DO NOT EXIST in the vacuum BEFORE
they "popped out of the vacuum", and no other contents of the vacuum

From the section on virtual particles in the link i provided before

http://en.wikipedia.org/wiki/Vacuum_state

(\blockquote
These virtual particles are included in the definition of the vacuum.
)

Maybe you would also take a look to

http://www.ts.infn.it/physics/experi...s/quantum.html

for a 'picture'. Tom van Flandern 'empty space' is also pictured.

Nowhere is science related to making claims about the world and then
expecting Nature to obey those claims.

Science is a dialog with Nature.


--
http://canonicalscience.org/en/misce...guidelines.txt

On May 5, 11:29*am, "Juan R." González-Álvarez

Science is a dialog with Nature.

Tom Roberts and his friends do not like dialog. They are dognatic. If
they lived during the years of scholastic philosophy, they would say
the same things and defend it. It's just a particular type of people.
The very same people that imbede progress instead of using their
knowledge to assist it.

Now, you are also wrong about some things. The notion of causality is
extremely dubious. In physics, it is not necessary at all. It can be a
nice metaphysical discussion but it is not physics.

TVF belives in a material fulx of gravitons that hot matter with FTL
speeds and create pushing gravity. If you are a seriosu physicist you
must immediately dismiss such naive concept, first developed by a in
early 18th century.

You see, if you try to defend yourself while defending some of TVF
concepts, you lose your credibility immediately.

TVF is not a crank, IMO. But hsi insist to present an all encompasing
theory of everything makes appear to some as one. He is otherwise a
very good physicist with solid credentials. But he does not realize
that there is a dividing line between the observable and the
inherently unobservable. So he thinks that gravitons can be observed
in the future like people observed air molecules now.

He does not want to accept that the properties of graviton in his flux
are already such that it cannot be observed. It is bogus particle.

Mike

Mike wrote:
Tom Roberts and his friends do not like dialog. They are dognatic.

You got it BACKWARDS. Tom Van Flandern is being dogmatic, in making
claims about the world and expecting Nature to conform to his claims.

Understanding current physical theories, and recognizing that no
experiments refute them, and also recognizing that crackpot theories do
not agree with the experiments, is NOT "dogmatic". That is part and
parcel of science.


TVF is not a crank, IMO. But hsi insist to present an all encompasing
theory of everything makes appear to some as one. He is otherwise a
very good physicist with solid credentials.

You have not followed his utter confusion about GR. Re-read his exchange
with Steve Carlip and see how poorly he understands GR. "Credentials" do
not matter, understanding is what counts. For someone who claims to be
an "expert" on gravitation, and to have studied it for decades, he has a
very poor understanding of modern gravitational theory.


"Juan R." González-Álvarez wrote:
Tom van Flandern did a remark about causality, Every effect has an
*antecedent* cause.

His claim is MUCH stronger than that, and is violated in every modern
fundamental theory of physics. Modern theoretical physics has a stronger
version of causality than merely "antecedent": no action or field
outside the past lightcone of point P can affect any field or happening
at point P. But this is QUITE DIFFERENT from Van Flandern's dictum.


Science is a dialog with Nature.

Hmmm. Watching a movie is a better metaphor than "dialog". While there
may appear to be an exchange, in actuality our theories merely color our
own interpretations of Nature, but do not affect her at all.


Tom Roberts

On 5 maio, 11:35, Tom Roberts wrote:
Nowhere is science related to making claims about the world and then
expecting Nature to obey those claims. That is whatVanFlandernis
trying to do, and that simply is not science. shrug

TomRoberts

I disagree. Deductive reasoning is applied very often in Science,
simply
because a set of observations, in most of the cases, does not have
a unique solution, i.e., there is not a unique model that explains it.
Therefore,
to expect that inductive reasoning alone will always lead to a correct
interpretation
is a mistake. That's why a set of starting premises ("claims about the
world")
and constraints are often attached in most of data analysis.

I've had an intermittent connection to USENET recently, and missed
this when it first appeared. Still, though, there's not too much to
say, since Tom Van Flandern is merely exhibiting his basic ignorance
of GR.

Tom Van Flandern wrote:

[...]
and Steve Carlip writes:

[Carlip]: Let R contain a single mass M moving at a constant velocity. ...
Then both GR and Newtonian gravity agree that a test mass at p will
experience an acceleration toward the "instantaneous" position of M. In
particular, the direction of that acceleration will track the motion of M.

Correct. The same would be true if M moved with arbitrary acceleration.

Not in GR. Do the math.

There was no need for the "constant velocity" assumption except to keep the
example simple. As for p, I'm assuming you mean it to be at rest in the
selected coordinate system, because moving with M would defeat the purpose
of the example.

[Carlip]: Now, at time t=0, make the following change in R: stop the
motion of M. You apparently agree that this change will have no affect at
p until the time for a light signal to reach p from R.

Nonsense. What I agreed to was that the gravitational potential field at
p would not change until one light-time later than t = 0. However, it is
clear from logic, observation, and computer experiments that the force
operating at point p changes almost instantly,

The "force" is the gradient of the potential. If the potential doesn't change,
its derivatives don't, either. Your statement here exhibits a profound lack of
understanding of basic mathematics.

[...]
[Carlip]: Write down the exact solution of the Einstein field equations
for a mass M that initially moves at a constant velocity and then abruptly
stops. ... Now just compute the acceleration at p.

[Carlip]: This is not a question of an "interpretation" -- it is a direct,
unambiguous mathematical prediction.

You can only say that because you have apparently not understood the
real issue. (More below.)

Nonsense. This is not a question of interpretation. It is a *calculation*.
General relativity tells you exactly how to do the computation, first to
determine the metric from the source mass and then to determine the
geodesics in that metric. Nothing is ambiguous.

[TomVF]: The one and only mathematical question of importance here to the
speed of gravity issue is this: For a target body with a transverse
motion relative to the source mass, should we use the retarded gradient
or the instantaneous gradient to get the force?

[Carlip]: There is no such thing as a "retarded gradient." The gradient of
a function is the vector of its spatial derivatives. Time doesn't come
into it.

Here you make an elementary mistake. It takes two points (or one point
and a direction) to determine a vector. So there is most definitely a "time"
issue because there is no remote simultaneity in relativity. That means if
the two points are synchronized in M's frame, they are not synchronized in p's
frame; and vice versa. So the "gradient" cannot be the same for both frames
if they have a relative transverse motion.

"Gradient" is a mathematical operation. Given a function, the gradient is
the vector whose components are its derivatives. The gradient of a function at
position x and time t is determined by the value of the function at x (and in its
infinitesimal neighborhood) at time t, period. This is elementary undergraduate
calculus.

[...]
[Carlip]: It is also an elementary mathematical fact, of course, that if a
function at x at time t is determined by the behavior of some source at an
earlier time t', then the gradient of the function of x at time t is also
determined by the behavior of some source at time t'.

In accord with the relativity principle, you are not entitled to adopt
the source mass frame as special and ignore the view from the target body
frame, or vice versa.

The statement I made is frame-independent. This is again elementary mathematics.

Tom, if you want to claim to agree with GR, you need to learn some math. You
are making things up here out of whole cloth.

Steve Carlip