Gravitoelectromagnetism (GEM) is a rather long and unwieldy name for the effects on spacetime caused by moving masses.
EM vs GEM
The name is based on an analogy with electromagnetism (EM) – where the subject of EM deals (in part) with the effects due to a moving electrical charge, GEM effects are the analogous behaviours caused by a moving gravitational charge (a moving mass).
The analogy is not exact (electrical charges can be positive or negative, gravitational charges can only be positive), but since both types of field are bound by the same general constraints of classical field theory, and both have a finite propagation speed (defined as "c" for EM, and generally assumed to nominally be "c" for GEM), the two classes of problem can't help but share some basic behaviours.
GEM effects cause a deflection of light, and also a deflection of the paths of objects passing through a region, and these effects are at least superficially reminiscent of the dragging effects expected in most obsolete dragged-aether theories (as most aether theories generate smooth variations across space that can be modelled as fields, have a finite propagation time, and again are subject to some of the same basic constraints as alluded to above)
As in C19th theories, a rotating mass will tend to drag light and matter around with it and also draw bodies towards it ("GEM-r"), and an accelerating mass will cause a dragging in the direction of forced acceleration ("GEM-a"). The first two of these effects can be calculated from Mach's principle, the second is also a consequence of the gravitational attraction of energy, and the third is also Machian.
A further effect is more controversial: a simply-moving gravitational mass logically ought to exert a pull on nearby objects and light, as a consequence of relative velocity between masses.
An apparently overwhelming set of mutually-supporting arguments seem to insist that velocity-dependent GEM effects (GEM-v) must exist, and are required to exist by any credible general theory, by continuum theory, and by simple arguments based on projective geometry and domain translation. We can also extrapolate general GEM-v form the special-case velocity-dependent dragging effect around a moving body, posit GEM-v as being the lower-order effect underlying GR's GEM-a effect, and derive it from the stochastic approach to quantum mechanics, from particulate-matter draggign effects, or back-derive it from cosmological horizon behaviour.
On the other hand, if GEM-v effects exist, they lead to a chain or arguments that result in the invalidation of special relativity, which depends on our ability to model the physics of masses with simpel motion as probems involving perfectly flat spacetime. If GEM-v effects exist, then SR is not fundamental phyics, and our current general theory of reativity is wrong for including SR as a perfect physical limiting case.
Then again, GR1960 contains a mass on logical inconsistencies, no longer conforms with the GPoR disagrees with quantum theory and associated general geoemtrical and thermodynioc laws, and fails ot predict medium-scale gravity properly unless we invent dark matter, so perhaps the current general theory needs to be scrapped and rewritten anyway.
Full GEM as the basis of a new General Theory
If we attempt to construct a general theory that conforms to the GPoR even where this disagrees with SR, we obtain the full set of GEM effects, a relativistic acoustic metric rather than the flat Minkowski metric, and apparent agreement with QM.
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Pages in category "Gravitoelectromagnetism (GEM)"
The following 6 pages are in this category, out of 6 total.