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In view of the observational equivalence of gravity and acceleration, does acceleration produce ripples in spacetime, similar to gravity waves?
EnumaElish said:In view of the observational equivalence of gravity and acceleration, does acceleration produce ripples in spacetime, similar to gravity waves?
What I did not get here is that it is a mass that is accelerated. So wouldn't this cause tiny changes in spacetime and thus make a gravitational wave possible, even if it might not be measurable?PeterDonis said:In short, in both cases, the acceleration does not involve any change in the curvature of spacetime at all. And gravitational waves are changes in the curvature of spacetime that propagate at the speed of light. So if there is no change in the curvature of spacetime, there are no gravitational waves.
Are you asking about treating the rocket case using GR rather than SR? Then, yes, in general, an accelerating rocket would generate (undetectable) gravitational radiation. [There are special cases where it wouldn't, e.g. the Kinnersly photon rocket solution. However, if you perturb the thrust pattern at all on that solution, you will get GW.] Some of the GW would be attributable to the mass of of they rocket payload.fresh_42 said:What I did not get here is that it is a mass that is accelerated. So wouldn't this cause tiny changes in spacetime and thus make a gravitational wave possible, even if it might not be measurable?
fresh_42 said:it is a mass that is accelerated. So wouldn't this cause tiny changes in spacetime and thus make a gravitational wave possible, even if it might not be measurable?
EnumaElish said:If two black holes are rotating around each other at variable velocities (perhaps because of elliptical orbits), they would alternately be accelerating and decelarating.
EnumaElish said:Wherever that is the case, could a fraction of what is measured by Ligo be explained by the acceleration?
Thank you. I was just asking because I thought that although unbelievably small it might be a non-zero solution. (I admit it's not really of physical interest.)PeterDonis said:If we are talking about a mass that produces non-negligible spacetime curvature being accelerated, we are talking about a different situation than the OP was referring to. If we are talking about "gravity and acceleration being equivalent", we are talking about the Equivalence Principle, which only applies in a small local patch of spacetime in which curvature can be ignored. Also, strictly speaking, the EP only applies to "test objects", which are idealized objects that produce zero spacetime curvature themselves. That was the scenario I was assuming in my response to the OP.
fresh_42 said:I was just asking because I thought that although unbelievably small it might be a non-zero solution.
The absence of gravitational radiation in Kinnersley's ``photon rocket'' solution of Einstein's equations is clarified by studying the mathematically well-defined problem of point-like photon rockets in Minkowski space (i.e. massive particles emitting null fluid anisotropically and accelerating because of the recoil). We explicitly compute the (uniquely defined) [it]linearized[/it] retarded gravitational waves emitted by such objects, which are the coherent superposition of the gravitational waves generated by the motion of the massive point-like rocket and of those generated by the energy-momentum distribution of the photon fluid. In the special case (corresponding to Kinnersley's solution) where the anisotropy of the photon emission is purely dipolar we find that the gravitational wave amplitude generated by the energy-momentum of the photons exactly cancels the usual 1/r gravitational wave amplitude generated by the accelerated motion of the rocket. More general photon anisotropies would, however, generate genuine gravitational radiation at infinity. Our explicit calculations show the compatibility between the non-radiative character of Kinnersley's solution and the currently used gravitational wave generation formalisms based on post-Minkowskian perturbation theory.
Non-gravitational acceleration refers to any acceleration that is not caused by the force of gravity. This can include forces such as electromagnetism, friction, or applied forces.
Yes, non-gravitational acceleration can produce waves. In fact, most waves that we encounter in everyday life are produced by non-gravitational acceleration, such as sound waves, light waves, and water waves.
Waves produced by non-gravitational acceleration are typically mechanical waves, meaning they require a medium to travel through. They also have a characteristic frequency and wavelength. On the other hand, gravitational waves are ripples in the fabric of space-time and can travel through a vacuum.
Some examples of non-gravitational acceleration producing waves include sound waves produced by speakers, light waves produced by electronic devices, and water waves produced by wind or a moving object in the water.
In some cases, non-gravitational acceleration can produce harmful waves. For example, exposure to high-frequency electromagnetic waves, such as x-rays or gamma rays, can be harmful to living organisms. Additionally, strong mechanical waves, such as seismic waves from earthquakes, can also be dangerous.