Sato Posted June 27, 2013 Share Posted June 27, 2013 If gravity is a force that interacts with matter via space, and gravitational waves are the measurable transfers of this force, then are all gravitational interactions due to gravitational waves, but most masses give off minute and constant gravitational waves which can't be detected very easily? Is that what the inverse-square law of gravitational is then, describing the dissipation of any gravitational wave over a distance? Link to comment Share on other sites More sharing options...
ajb Posted June 27, 2013 Share Posted June 27, 2013 ...then are all gravitational interactions due to gravitational waves, but most masses give off minute and constant gravitational waves which can't be detected very easily? Gravitational waves can be thought of as the small ripples in space-time coursed by changes in a massive object. They are described in terms of lineariation of the gravitational field and are like the "electromagnetic waves" of gravity. They are to do with small changes rather than the gravitational field absolutly. Link to comment Share on other sites More sharing options...
Enthalpy Posted June 27, 2013 Share Posted June 27, 2013 More questions... I imagine that mass does not change quickly, nor does a single mass accelerate or oscilate - only two or more bodies can interact and they keep their center of mass inmobile in this process. This is why gravitational waves are not dipolar (which would have corresponded to: the single mass oscilates between right and left) but quadripolar, resulting from the generating masses alignment changing between aligned and transverse as seen from the observer. The wave's frequency is also twice the masses' orbital frequency. Is that any reasonable? Keeping the analogy with EM waves for want of understanding gravitation, I figure that masses close to an other or moving slowly create a near-field quadripole that decreases as 1/R3, which is not called a wave (is it?) and does not propagate. In addition, because gravitation propagates at a finite speed, when the masses move quickly enough as compared with gravitation's propagation time, the "phase difference" prevents the 1/R2 terms to fully cancel out, and a significant power is radiated as 1/R2 which is then called a wave. Does this make sense? I've seen a formula for the radiation by a pair of stars with a speed well below c. But is the power radiated by an ultrarelativistic object known? Several detectors in service have seen no wave up to now. Is that normal? Have attenuation processes been proposed for gravitational waves? Have methods been proposed for humans to create our own detectable gravitational waves? I mean, not the rotating bars which produce a near-field only - no, a real far-field wave, even if far means just 10m away. Thank you! Link to comment Share on other sites More sharing options...
ajb Posted June 28, 2013 Share Posted June 28, 2013 (edited) This is why gravitational waves are not dipolar ...The root of the reason why we do not have dipoles in gravity is that fact that mass is always positive. This is in contrast to electromagnetisum where we have positive and negative electric charges. Another way to think of this is that conservation of mass prevents monopole radiation and conservation of momentum prevents dipole radiation. Have methods been proposed for humans to create our own detectable gravitational waves? I mean, not the rotating bars which produce a near-field only - no, a real far-field wave, even if far means just 10m away.Creating gravitational waves in principle should be easy. The trouble is that there ampliture will be tiny and so undetectable. The sort of waves people are looking for come from quite violent processes like black hole collisions. Edited June 28, 2013 by ajb Link to comment Share on other sites More sharing options...
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