Natural Science Forum / Physics / Relativity / February 2007

Nothing about the theory.

Because it is mere speculation and drools about aether.

On Feb 23, 12:30 pm, d_ha...@yahoo.de wrote:

Like this?

http://www.chem.purdue.edu/gchelp/liquids/inddip.html
http://www.mypage.bluewin.ch/Bizarre/GRAV.htm

http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html

Is it abandoned?

<< This interpretation governs the expectation
that accelerated bodies have concordant
accelerating action in the same
sense on other bodies (acceleration induction).
This interpretation is even more
plausible according to general relativity
which eliminates the distinction between
inertial and gravitational effects.
It amounts to stipulating that, apart
from the arbitrariness governed by the
free choice of coordinates, the
gm v -field shall be completely determined
by the matter. Mach's stipulation is favoured
in general relativity by the circumstance
that acceleration induction in accordance
with the gravitational field equations really
exists, although of such slight intensity
that direct detection by mechanical experiments
is out of the question. >>
http://nobelprize.org/nobel_prizes/physics/laureates/1921/einstein-lecture.html

Sue...

Experiment showed gravity is modelled closely using the metric tensor - EM
by a 4 vector - the 4 potential - leading to entirety different predictions
eg if gravity was EM based we would not have a positive result in the
Pound-Rebka experiment.

Thanks
Bill

I don't know the details of Lorentz's proposal.  But the question of
explaining gravity in terms of imbalanced interactions of charges of
this sort came up in sci.physics recently.  It doesn't work, for a
number of reasons (I'm basically quoting my own post here):

First: this model has the same problems with the principle of
equivalence.  In particular:

 1.  We observe that an electron moving at a finite velocity  
     has a larger inertial mass than an electron at rest.  The  
     inertia, as measured by response to an external force,  
     is increased by E/c^2.  (There are some tricky issues of  
     reference frames if you consider a single electron, but  
     there's no ambiguity if you consider abound system and
     look at the velocities of the electrons relative to the
     center of mass.)
 2.  We observe that despite their greater inertial masses,  
     objects in which electrons are moving rapidly fall at  
     exactly the same acceleration as objects in which electrons  
     are moving more slowly.  By Newton's second law, this means  
     that the *gravitational* mass must also increase by E/c^2.
 3.  The same argument holds for other forms of energy, including
     electrostatic energy, magnetostatic energy, energy of weak  
     neutral currents, and gravitational binding energy.

This means that, *observationally*, energy gravitates.  Since electric
charges (again, observably) don't change with energy, this excludes
any model in which gravity is a result of electric charge.  Note that
the relevant experiments typically have accuracies of a few parts in
10^11 or better, so you can't just dismiss this as an oddity -- any
serious model of gravity that's based on electric charge has to
explain why energy, which is uncharged, contributes *exactly* E/c^2
to gravitational interactions.

Note in particular that (again observationally) gravitational energy
itself gravitates.  This means that any theory of gravity must be
nonlinear; you can't just fiddle with a linear theory like
electrodynamics.

Second: this model fails the binary pulsar test.  We observe that
binary neutron star orbits slowly decay, with an energy loss that
precisely matches the amount predicted by general relativity from
emission of gravitational radiation.  This amount depends on the
mass quadrupole moment of the binary system.  Electromagnetic
radiation, on the other hand, depends on electric *dipole* moments.  
This means that if the two neutron stars had unbalanced electromagnetic
interactions, the amount of radiation would be much higher -- dipole
radiation is much stronger than quadrupole radiation.  (Note, again,
that this is a precise quantitative issue.)

Third: despite some hand-waving, this model does not explain the
deflection of light by a gravitational field.  The nature of light
follows directly from Maxwell's equations -- it is a propagating
electromagnetic field, and is, in particular, uncharged.  It should
therefore not be affected by an interaction that is based on unbalanced
interactions of charges.  

Fourth: there are a large number of precision measurements of gravity
that go beyond a Newtonian inverse square interaction.  These include
precession of perihelia in the Solar System (Mercury, Mars, Icarus)
and in neutron star binaries; gravitational red shift and time dilation;
Shapiro time delay; de Sitter precession of the Earth-Moon system; a
number of strong field tests of gravity in binary pulsar systems (the
"r" and "s" parameters); and probably frame-dragging (we'll hear the
results from Gravity Probe B in April).  Physics is a quantitative
science; a proposed alternative to general relativity has to explain
these observations quantitatively at least as well as general relativity
does.

Steve Carlip