Reply to post: Re: Red-shifted gravity

Grav-wave eggheads come closer to nailing down Hubble's Constant – the universe's speedy rate of expansion

Palpy

Re: Red-shifted gravity

Mmmm. That's a question for physic maths.

I'm uncertain whether the properties of electromagnetic waves and the properties of gravity waves are identical in that regard.

Thinking intuitively, with no real physics to back me up: gravitational waves induce a stretch-squeeze as they pass through spacetime, and through matter. Similar (but not identical in detail) to the tidal stretch-squeeze of the Moon.

For waves of frequency X, pretend that the stretch-squeeze happens 10 times per minute; after the frequency is expanded by a factor of 2, the stretch-squeeze would happen 5 times per minute. So if you had something which extracted energy from the waves -- a piezoelectric crystal the size of Scotland, for example -- then the waves would transfer less energy per minute from the redshifted gravitational wave. Or so it would seem.

But imagining an event like the merging of two black holes, then the entire wavetrain generated by the event would have the same total energy after redshifting as before -- the wavetrain would just be twice as long, and would take twice the time to deliver the energy to your giant piezoelectric device.

I hope someone with knowledge of the theory and maths involved pipes up. I just hung my hat on a bunch of intuitive BS...

Incidentally, it's worth noting (again) that physics is mathematical. When one says that "the speed of light is measured experimentally using experiments that themselves are based on how fast forces propagate ... You cannot rely on the speed of light being a constant just because you measure it as such." that's kind of true... but in fact the speed of light can also be derived from Maxwell's wave equation. And like all well-established mathematical descriptions of the Universe, Maxwell's descriptions of electromagnetism, in math, has stood innumerable experimental tests coming at it from many, many angles. And of course his laws are retested every day inside your computer. The Electric Universe guys can toss out the bathwater, conceptually, but they don't realize the number of babies they toss out with it.

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