Re: Welcome to Dipole Gravity blog


"Uncle Al" <UncleAl0@xxxxxxxxxxxxx> wrote in message
news:46238BB7.93770038@xxxxxxxxxxxxxxxx
Supertech wrote:

http://dipoleantigravity.blogspot.com/

Idiot.

The source of monopole radiation is a changing monopole moment for a
charge q or for a mass m. Since charge and mass are conserved, there
can be neither monopole electromagnetic radiation nor monopole
gravitational radiation.

The source of dipole radiation is a changing dipole moment.
(Punctiliously, you need a second time derivative of the dipole
moment.) For a pair of charges

d = qr + q'r'

and there's nothing special about the derivatives. For a pair of
masses, the gravitational dipole moment is

d = mr + m'r'

and its time derivative is

mv + m'v' = p + p'

By conservation of momentum the second time derivative of the
gravitational dipole moment is zero, and you can go to a center of
momentum frame and set the first derivative to zero as well. There is
no gravitational "electric dipole" radiation.

Consider the analog of "magnetic dipole" radiation. The gravitational
equivalent of the magnetic dipole moment for a pair of charges is

M = mv x r + m'v' x r'
("x" is the cross product, "mv" is the "mass current")

But M is the total angular momentum, which is also conserved. There
is no gravitational "magnetic dipole" radiation.

The next moment up is quadrupole, with no relevant conservation laws,
so gravitational quadrupole radiation is permitted. You can use this
argument to advocate that gravity must be a tensorial (spin-2)
interaction. Electromagnetism is mediated by spin-1 photons.

Maxwell-like ("vector") gravitational equations fail for a number of
reasons. Among the main ones:

1) In electromagnetism, like charges repel, while opposite charges
attract. In particular, if you have three charges, they cannot all
attract each other. (If charge 1 is positive and attracts charge 2,
then charge 2 must be negative. Then what is charge 3?) The
situation for gravity is clearly different.

You can try to alter Maxwell's equations so that like charges
attract. To do so, though, you have to change signs in such a way
that the energy of electromagnetic radiation comes out negative. This
is a disaster (and would be for gravity): it would allow a pair of
charges or masses to generate energy without limit by radiating away
negative energy.

2) Even if you ignore the sign problem, radiation in a vector
theory is emitted at a much faster rate than in a tensor theory like
general relativity. For a pair of masses in GR, radiation depends on
the rate of change of the quadrupole moment. For a pair of charges in
Maxwell's theory, or a pair of masses in a vector theory of gravity,
the radiation rate depends on the rate of change of the (much larger)
dipole moment. This leads to predictions of gravitational radiation
that disagree severely with observed decays of binary pulsar orbits.

3) A general vector theory of gravitation involves three adjustable
parameters. These can be chosen, by hand, to predict the right
precession of Mercury's perihelion (though GR has the advantage that
no ad hoc choices are needed to get the right answer). But the
resulting vector theory predicts no bending of light in a
gravitational field, again disagreeing strongly with observation. See
Robertson and Noonan, _Relativity and Cosmology_, section 6.6.

4) In a vector theory of gravitation, the energy of the field
itself does not gravitate. (The electromagnetic analog is that the
electric field has no charge, and doesn't generate its own electric
field.) But we know from observation---by comparing the Earth's and
the Moon's motion toward the Sun---that gravitational binding energy
*does* contribute to the gravitational field.

Vector theories of gravity are thus strongly ruled out by observation.

Idiot.


The proposed dipole gravitational moment is not radiative. It's a static
gravitational field according to the theory in the blog. I don't think you
read the article before advertising your lengthy reiteration of the already
well known materials in the 20 year old lecture notes of somebody's on
gravity.

The dipole gravitational moment is temporal in the sense that it exists only
when there is an angular momentum for an asymmetric object like hemisphere.

It has nothing to do with any of the materials in your 20(or perhaps 30)
years old lecture note.


.

Relevant Pages

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