Kopeikin and "the speed of gravity"

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On 10-Jan, AgoraBasta suggested an empirical way to measure the speed of gravity with large quartz crystals. Another approach might be to use gravimeters (mentioned by Larry Burford), as long as they have very fast responses or at least reliable latencies (e.g., within a few nanoseconds). If we have a mass, detected both up close as well as a few meters away by two identical gravimeters, couldn't we bump (accelerate) the mass and measure the delay between the gravimeter readings? Couldn't this enable us to determine quite easily whether gravitational force travels at close to c or not?

John


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Yes, if gravimeters had nanoseccond response times. To the best of my knowledge the fastest currently available have response times on the order of a second or so.

Bummer.

Regards,
LB

From Larry Burford: "To the best of my knowledge the fastest currently available [gravimeters] have response times on the order of a second or so."

I have found a lab that sells 1MHz gravimeters. This implies a 300 meter separation to confirm a c speed. I'm afraid an explosion would not work as a detectable disturbance because the center of gravity might not change for several microseconds. Maybe the swaying of a large building? Or, maybe "background" patterns could be picked up at both sites and be correlated. There has to be an elegant empirical solution to this.

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From Larry Burford: "To the best of my knowledge the fastest currently available [gravimeters] have response times on the order of a second or so."

[JBailey]
I have found a lab that sells 1MHz gravimeters. This implies a 300 meter separation to confirm a c speed. I'm afraid an explosion would not work as a detectable disturbance because the center of gravity might not change for several microseconds. Maybe the swaying of a large building? Or, maybe "background" patterns could be picked up at both sites and be correlated.

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That's my intuition on this as well. But, we shall see...

Now, about that gravimeter you found... do you have any other specifications on it? Specifically, what is it's sensitivity at the maximum sample rate?

The gravimeters I've found so far have sensitivities of around 1 to 10 uGal, and these are (I believe) the ones that can detect a person moving around near-by.

I'll be (very pleasantly) surprised if this one can achieve the sensitivity needed to detect the movement of a 75 kg mass at 1 microsecond intervals. And a range of 300 meters would really be nice, but this also seems unlikely.

I hope you can surprise me. If this device can do all these things <b>at the same time</b>, we just might be able to "measure" (set a reproducible hard lower bound on) the speed of gravitational acceleration. It would be borderline, though. 300 meters at c is about a microsecond ...

BTW, if anyone else has specific data on specific instruments, I think we should consider collecting it here. Or rather, references to the information with a summary here. Most will not be capable of doing what we want to do, but that is still usefull knowledge.

Regards,
LB

LB,

Mac here. I can't say yet what it is that we are doing but as soon as our testing is completed, I believe the setup we are using may be adapted to your problem. I'm an old Instrument tech and I believe I can design a system to achieve what you want.

Our tests ar currently showing what we wanted to show but we need more data to establish a good foundation. We are sensing 3 billionths of a pound but we get abnormal runs for reasins not yet clearly understood.

On the average the data says what we think it should say.

"I have found a lab that sells 1MHz gravimeters"

Is that a transfer function frequency response? Suppose yes, then trying to measure the speed of gravity with a gravimeter is like trying measuring the acceleration of a speeding car by speeding a track next to it. The only thing you will measure with a gravimeter is how fast the gravimeter responds to gravitational disturbances. When the frequency of the disturbance exceeds the frequency response of the gravimeter it will act as a filter. At any rate, what is measured is not the "speed of gravity" but speed of gravitational potential disturbances. You can assume that is equal to c and it will save you from a lot of trouble and pain in keeping the gravimeter inside at a constant temperature (within .0001 C or something like that).

I don't know if anyone knows what is really meant by "speed of gravity". I guess to understand that one must know what gravity is in the first place. lol

Mechanic writes, "The only thing you will measure with a gravimeter is how fast the gravimeter responds to gravitational disturbances."

If Larry, Mac and I are reasoning correctly, we think two identical gravimeters, separated by a distance that is greater than their response times divided by c, could both be subjected to a single gravitational disturbance. Does this not show a speed of the force? For example, GR'ists would predict the more distant measurement will occur d/c seconds later. Or does this setup only show the speed of the potential disturbance/wave/etc.?

The design of the gravimeter, as I understand it, is to measure a falling weight at 1MHz intervals. The company is www.Microgsolutions.com .

Does anyone understand whether Walker and Dual have published the results of their vibrating rod experiments? Perhaps we are simply retracing old ground on this (see www.ldolphin.org/vanFlandern/9706082.pdf ).