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The speed of light is now defined as 299792458. m/s
But what is the speed of gravity ?
But what is the speed of gravity ?
There is only one fundamental constant in Maxwell's Equations, namely c. The so-called 'permeability of free space' μ0 is inserted solely for the benefit of Electrical Engineers. It's unfortunate that introductory E & M courses make it seem otherwise. In fact μ0 has the exact defined value of 4π x 10-7. Maxwell's Equations written in Gaussian units, for example, contain neither ε0 or μ0, only c.Baluncore said:I know that c, the velocity of EM waves in space, is determined by the product ε0 μ0 = 1 / c2
Baluncore said:But without seeing some basis for that assertion, it strikes me as wishful thinking, and so requires me to have faith. That gravitational waves propagate at c seems at first sight to be eminently acceptable, and sure is neat. But “It can be shown” does not really convince me as I am stubborn and of little faith.
http://mathoverflow.net/questions/112029/the-speed-of-gravitational-waves-in-general-relativityHomogenousCow said:Do we even have a concrete definition of what "the speed of gravity" means outside of linear gravity?
I mean in EM we could solve the vacuum wave equations, where c just emerged out of, but in full blown non-linear GR we of course don't have those neat equations.
On the other hand, the speed at which gravitational waves propagate must be frame invariant, which means it must locally be C.
Yes, this is a good explanation, and serves to remind us that General Relativity is not the only nonlinear theory in the world. The theory of nonlinear PDE's and their associated wave motions is well developed.WannabeNewton said:http://mathoverflow.net/questions/112029/the-speed-of-gravitational-waves-in-general-relativityHomogenousCow said:Do we even have a concrete definition of what "the speed of gravity" means outside of linear gravity?
I mean in EM we could solve the vacuum wave equations, where c just emerged out of, but in full blown non-linear GR we of course don't have those neat equations.
On the other hand, the speed at which gravitational waves propagate must be frame invariant, which means it must locally be C.
DO you happen to know of a good textbook delving into detail on these and related topics (non-linear wave PDEs)? Thanks Bill.Bill_K said:The velocity of wave propagation is studied as high frequency, small amplitude perturbations on a background, or equivalently as the propagation of discontinuities on that background. Wave fronts are the characteristic surfaces, and information propagates along the generators of those surfaces, i.e. the bicharacteristics.
The speed of gravity is 299792458 meters per second (m/s). This is the same value as the speed of light in a vacuum.
The speed of gravity is typically calculated using the inverse square law, which states that the force of gravity between two objects is inversely proportional to the square of the distance between them. By measuring the distance between two objects and the force of gravity between them, scientists can calculate the speed of gravity.
No, the speed of gravity is not faster than the speed of light. Both have been measured to be the same value, 299792458 m/s. This is a fundamental constant in the universe.
According to Einstein's theory of general relativity, the speed of gravity is a constant value. However, some theories suggest that the speed of gravity may vary in extreme conditions, such as near black holes.
The speed of gravity affects us by determining the strength of the force of gravity between objects. It also plays a role in the motion of celestial bodies in our solar system and beyond.