Re: Tom Van Flandern and Newtonian Gravity

From: Tom Van Flandern (tomvf_at_starpower.net)
Date: 09/20/04 

Date: Mon, 20 Sep 2004 10:51:29 -0400

            This replies to Gerald Lasser and Vern.

"Gerald Lasser" <antispam@nospam.com> writes:

STATIC VS. NON-STATIC FIELDS

>> [tvf]: there should be no observable consequences to choosing the
>> source's frame or the sensor's frame to do physics. In particular,
>> there is nothing time-dependent about the static field.

> [Lasser]: The charge is NOT static with respect to the rest frame
> coordinates of the sensor, because the charge is moving relative to
> the sensor. Therefore, the equations of electrostatics are not
> applicable in terms of these coordinates. The equations of
> electrostatics apply only to coordinates with respect to which all
> charges involved are at rest.

            Here we have a case where the sensor has no effect on the
source charge or its field. So it is a one-charge case with an inactive
sensor. You are saying that the observable results will be different
depending on whether the charge is at rest and the sensor moving, or the
sensor is at rest and the charge moving. This is a violation of the
relativity principle. It amounts to a claim that there is absolute
motion.

MEANING OF "NEARFIELD"

>> [tvf]: it doesn't matter whether the region involved is more or less
>> than "one wavelength" from the source because electric forces are not
>> a wave phenomenon, so there is no such thing as the "wavelength of an
>> electric force". What do you think the definition of wavelength is
>> for a single, fixed charge?

> [Lasser]: Consider (again) two stationary charges, initially at rest
> and separated by a distance D. Momentarily move one of the charges
> slightly, and then put it back at rest in its original position.

            Do you know the difference between a wave and an
oscillation? An oscillation can occur in a void, whereas a wave requires
a medium to transmit it. An oscillation can have arbitrary speed,
whereas a wave can have only the speed determined by its medium type and
density. An oscillation can displace anything it contacts to a great
distance, while a wave has constituents that oscillate in place and only
the momentum moves on, but not the entities comprising the medium.

            Your example is of an oscillation, which has no
characteristic wavelength of its own, although it can trigger a wave if
it is surrounded by a medium. In my example, there was no oscillation,
only uniform, linear, relative motion of a charge and a sensor. Electric
forces are not a wave phenomenon, and therefore have no natural
nearfield/farfield distinction.

> [Lasser]: The resulting variations in the electric and magnetic fields
> as a function of time can be computed unambiguously using Maxwell's
> equations. According to those equations (with which you claim to
> agree), the fields at the other particle are totally unaffected until
> a time D/c after the first particle was moved.

            Why do we regress on this point with every message?
Disturbances of the potential field are lightwaves and propagate at c.
Electric forces and changes in electric forces propagate faster than c.
Maxwell's equations correctly reflect that dichotomy; i.e., they have
more than one physical interpretation. Many equations do, which is why
equations can't dictate physics, but only the other way around.

            You are insisting that your preferred interpretation is the
only possible one. Whether your preferred interpretation is better or
worse than mine, you are clearly wrong in your denial that there are two
possible interpretations. Think about it. I can see your interpretation,
but disagree with it. It is not to your credit that you cannot even see
my interpretation because you are in no position to judge it if you
cannot see it.

PROPAGATION SPEED OF ELECTRIC FORCES

> [Lasser]: This is exactly what occurs when electrons are moved in an
> antenna. The time-dependent variations in the Coulomb field near an
> antenna have been extensively studied. In the near field we are not
> dealing with waves, we are dealing with highly complex patterns of
> fields varying in time and place. Maxwell's equations are extremely
> successful in representing the observed patterns. All electric and
> magnetic effects propagate at the speed c.

            Your explanation is mistaken. Radio waves propagate at speed
c. Theory says that all lightwaves have an electric vector and a
magnetic vector. But those are just names for the two components of a
transverse wave. In point of fact, lightwaves of any wavelength carry no
charge and no magnetic field. The forces they apply are purely radiation
pressure, not electric or magnetic forces. And no experiment has ever
measured an electric force propagating as slowly as speed c. But it is
easy to prove me wrong by citing one.

> [Lasser]: This is exactly analogous to how changes in the static
> pressure exerted on the top of a cylinder of gas by a piston propagate
> at the speed of sound from the piston to the head of the cylinder.

            If we strike a material body, it sets off a pressure wave
traveling through the body (the medium) at the speed of sound in that
body. If the body rests in a surrounding medium such as air or water, a
simple displacement of the body can set off waves in the surrounding
medium. In either case, the speed of those waves has no relationship
whatever to the speed of the force that displaced the body.

            The example I usually cite is an asteroid impact. The mass,
speed, and force of the asteroid are one thing. The amplitude, speed,
and force exerted by the sonic boom it sets off in the atmosphere are
another thing entirely. Do you not see this?

WHAT DETERMINES A GRADIENT?

>>> [Lasser]: The definition of the gradient of a scalar field does not
>>> involve "the motion of a second point".

>> [tvf]: It certainly does if the point at which we wish to know the
>> gradient is a moving point.

> [Lasser]: If you're using the word "point" to mean a spatial location
> corresponding to a specific set of coordinates, then obviously every
> point is at rest with respect to the coordinate system in terms of
> which it is defined, so on this basis your statement is incoherent. On
> the other hand, if you're using the word "point" to mean a physical
> particle, then your statement is simply false (which I guess is
> slightly better than incoherent - but not much.)

            I hate to shock you like this, but there are actually some
wild-eyed mathematicians on this planet (incoherent though they may be)
who like to discuss the properties of a point moving with respect to a
coordinate frame. What will they think of next!

            Seriously, while you have maintained a high level of
discourse for the most part, that last point was a loser. Would you like
to reconsider?

> [Lasser]: The simple and elementary fact is that, given a scalar
> function f(x,y,z) in terms of a given system of coordinates x,y,z, the
> gradient of f is a vector field with components df/dx, df/dy, df/dz at
> each point.

            Suppose neither of us had ever heard of taking the gradient
at a moving point in a fixed field, or at a fixed point for a moving
field. Recall that the intensity of a wave is proportional to amplitude
squared, where amplitude is a measure of maximum displacement. Now
compute the gradient (a vector) of the amplitude of sunlight (a scalar)
as observed from Earth, which is the direction in which intensity is a
maximum.

            If the answer you get is that it points toward the origin of
a coordinate system fixed in the Sun, you got the wrong answer.

> [Lasser]: Instead of just exchanging verbiage, let's get specific.
> Given a static scalar field f(x,y,z) = 6x^2 - 7xy + 3xyz + 2yz - 5z^3,
> what do you believe is the gradient of f at the point (2,7,-4)?

            Why so complicated to make a simple point? Alright, df/dx =
12x - 7y + 3yz, where "d" is a partial derivative operator. This
evaluates to 24-49-84 = -109. Next, df/dy = -7x +3xz + 2z --> -14-24-8
= -18. Lastly, df/dz = 3xy +2y -15z^2 --> 42+14-240 = -184. So the
gradient is -109i -18j -184k, where (i,j,k) are unit vectors along the
(x,y,z) axes, respectively.

> [Lasser]: Now suppose a particle is moving through the point (2,7,-4)
> with the speed v in the positive x direction. What now is the gradient
> of f at the point (2,7,-4)?

            It is the same.

> [Lasser]: These are vitally important questions, because you claim to
> agree with Maxwell's equations, but those equations involve the
> gradient operator, and you obviously don't understand what this
> operator signifies. Until you learn what the word "gradient" means,
> you really aren't in a position to say whether you agree with
> Maxwell's equations or not.

            Uh, gee, did I get it right, teach? It was just a lucky
guess. :-)

            Now let's get serious and realistic and redo your example so
that it relates to this discussion instead of only to elementary pure
math. I agree that it is vitally important to understand what the
gradient "del" operator means in general, not just what it means in
simple number applications with no "source" and no propagation. If you
worked my example with sunlight above, you already know why your example
breaks down when applied to regenerating physical fields with a source.
If not, let's work it through now. Then you can go back and apply what
you learn here to getting the sunlight answer right.

            In our discussion, we have considered cases where the field
has a source and propagates radially outward at speed c (or in general
at speed V). It is still a static field with a fixed value at every
fixed point in the source's coordinate frame. But it must continually
regenerate to maintain that static situation because, if the source
vanished, so would the field at every point one propagation delay
interval later. In my papers, I use the waterfall analogy. Your example
is like a frozen waterfall with no moving parts. My example is like a
flowing waterfall, where it is always the same at any one point even as
each droplet of water is being continually replaced by another from
behind.

            So to make your example work, we would have to begin by
describing the velocity vector of the moving point, then by noting the
units of the scalar field (perhaps units of velocity squared, such as
potential has), then setting the units of the gradient (perhaps
acceleration units), because they are necessarily different. We would
then note that the gradient is variable over time as measured from the
moving point, and that the direction of the source is displaced in the
direction of the point's motion by the aberration angle [arctan(v/V)].
(Strictly, in this ratio we should use only the transverse component of
the relative velocity v.) The resultant gradient measured at the moving
point at some specific place and time will then be the directed toward
the retarded direction of the source, not its present direction at the
chosen time. The two directions differ by the specified aberration
angle.

            To get quantitative, we would have to specify all these
units and specific values for v and V in addition to the locations of
two points, the source and the target, at some specified time. But in
its simplest form, the gradient measured at the moving point will be the
vector sum of the original gradient and the point's transverse relative
velocity vector, each expressed in suitable units.

            These are important considerations, just as you say. Are we
now past the point where you think I don't understand the basics? I
understand them very well, which is why I have had some success in
publishing critiques of the long-accepted physical interpretations of
these concepts. Until you see that there are at least valid questions
about that standard interpretation, you will continue to patronize and
fail to teach or learn anything worthwhile in this discussion. -|Tom|-

and "Vern" <vern@bealenet.com> writes:

> [Vern]: the quote was a commentary on the derivation of Kepler's Third
> Law from Newton's inverse-square force, which derivation evidently
> mistakenly assumes the mass of the target body is irrelevant.

            Why do you say "mistakenly" in the above sentence? The
Galileo "Tower of Pisa" experiment and the Astronaut Scott "hammer and
feather" demonstration on the Moon both showed even the "man on the
street" that gravitational acceleration does not depend on the mass of
the target body. Today, Eotvos-type experiments have confirmed this to
more than a dozen decimal places.

> [Vern]: Nevertheless, the issue is that the inverse-square force may
> also be derived from Huygens' equations and Kepler's Third Law, so
> Newton's Theory of Gravitation is at best only one possibility for how
> nature works.

            Newton's aptly named "universal law of gravitation" is a
possibility that has been repeatedly verified to better than a part in a
million in lab experiments and astrophysical systems throughout the
Galaxy and even in nearby galaxies. By contrast, every other force law
ever tried has failed, with the single exception of "post-Newtonian"
theories such as GR which derive a force law that differs
insignificantly from Newton's for most local applications.

> [Vern]: There could also be a fundamental tangential force or a
> universal rotation involved in nature. What experimental evidence
> supports either? That rotating systems seem to evolve alike is
> evidence of universal rotation being a factor. Universal rotation is
> explained by a sink vortex model.

            To my knowledge, a tangential force is not a possibility
because it would instantly destroy angular momentum conservation -- the
very quantity you most want to preserve. But if someone has actually
thought of a clever type of tangential force that gives closed orbits, I
would love to learn of it. That would be big news. Has this happened or
not? Please be specific.

            As for a "universal rotation", I have no idea what that
expression is supposed to mean. I'm unaware of any real concept that
would qualify for that description. And I also don't know what you mean
by "rotating systems evolve alike". Give an example. The solar system's
planets certainly have now "evolved alike" and do not share any common
rotation, so where is this supposed to be true?

> [Vern]: Molecules of an ideal gas do not vibrate or oscillate in a
> kinematic sense; Newtonian contact forces are all that are involved.
> That is a common misconception.

            The only "misconception" I see is in your interpretation of
these words, because what I said also assumes that contact forces are
all that is involved. When molecules have a short mean free path before
a collision, we often describe their average motion as vibratory or
oscillatory in nature.

> [Vern]: If a gas is in an isotropic state then the average
> collision-free distance of the molecules is the same.

            I'm sure you mean a homogeneous state. "Isotropic" just
means no change with direction, but density could still vary with
distance. "Homogeneous" means uniform throughout.

> [Vern]: Any disturbance in the gas causes a change in the
> collision-free distance of the molecules. Waves are a series of
> compression pulses dissipated by a change in the collision-free
> distance and are therefore dependent on the average velocity of the
> molecules.

            The whole point of the discussion was that this "dependence"
is not an equality. The wave speed does depend on the average molecule
speed in the way that I described. But those two speeds cannot be equal
for the reason I stated: Molecule speeds take place in three dimensions,
and only the component of that speed in the wave direction goes into
wave speed.

            You seem to have little understanding and many
misconceptions about how standard physics works. Don't you think it
would be valuable to learn standard physics before attempting to
criticize it? At a minimum, you will need to know the standard models to
succeed in communicating with others. This process you use of inventing
unfamiliar concepts on the fly and using technical terms in unfamiliar
ways is almost impossible to follow. -|Tom|-

Tom Van Flandern - Washington, DC - see our web site on replacement
astronomy research at http://metaresearch.org

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