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Re: [Phys-L] gravitational waves (Ludwik Kowalski)



Thank you Don. I had in mind a much simple setup, like my two-disks model.

* Suppose the masses of disks, separated by the distance x=10,000 meters, are identical, for example M=10,000 kg. each.

* Suppose the M is pushed toward m suddenly, at the moment t=t1.

* Suppose a tiny sensitive detector, mounted on m, detects the gravitational disturbance at the moment t=t2

* S suppose the time interval dt=t2- t1 is measured, with two fast synchronized clocks.

* In that case the x/dt ratio would be called "speed of the gravitational disturbance", SD.

* Suppose the SD is measured many times, perhaps ten or thousand. What should I expect?

* The mean SD would most likely be very close to c. The error bar would most likely be determined by precision of fast clocks.

Ludwik
=============================================

On Apr 13, 2016, at 2:05 PM, Donald Polvani wrote:

The two LIGO detectors (Hanford, WA and Livingston, LA) are 3002 km apart.
For a gravitational wave, traveling at the speed of light, this gives a
range of possible delay times between the two detectors of 0 to 10 ms
depending on the angle of arrival of the wave. The observed delay time for
the September detection was 6.9 ms. The angular position of the source is
reported as within an area of 600 deg^2 consistent with the 6.9 ms
measurement. The experimenters say that to further pin down the angle of
arrival (and, thus, the speed of the wave) a third remote detector is
required (possibly in India?).

https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.116.061102

Don

-----Original Message-----
From: Phys-l [mailto:phys-l-bounces@www.phys-l.org] On Behalf Of Ludwik
Kowalski
Sent: Wednesday, April 13, 2016 12:44 PM
To: Phys-L@Phys-L.org
Subject: Re: [Phys-L] gravitational waves (Ludwik Kowalski)

1) Cavendish, who died 200 years ago, would certainly measure the speed of
a gravitational disturbance (with his simple laboratory model), if he had
an
ultra-fast clock, similar to clocks available to modern scientists.

2) Did LIGO scientists try to do something like this?

3)They probably did this; the mean was probably very close to c. And the
bar
of random error was probably much smaller than 10%. Yes I am guessing
again.

Ludwik
=======================================


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