Re: gravitational-wave sources (was: Re: Is temporal sign ambiguity inherent in Einstein's general relativistic field equation?)


Joe Fischer wrote:
> On Tue, Jonathan Thornburg wrote:
>
> >In sci.physics.research Joe Fischer wrote:
>
> Sorry, I didn't realize the message I replied to
> was cross posted to s.p.research.
>
> >> I would like to state how I think LIGO should have been tested from the
> >> beginning.
> >>
> >> A perfectly level rail line should have been built running toward and
> >> away from the end of the arm, and a rail car propelled by rockets used
> >> to accelerate a large mass ~10E+6 kg, back and forth as rapidly as
> >> possible.
> >
> >Unfortunately, this would
> >(a) produce large ground vibrations which might well interfere with
> > LIGO's operation,
>
> I was assuming that a smooth rail line would not
> cause too much vibration with only rocket power.
> The cost would be so small compared to the total
> cost of the program that it should provide some useful
> data. It is not too late to do if nothing like has been
> tried.
>
> >(b) produce large *Newtonian* gravitational effects which would
> > interfere with LIGO's operation, and
>
> Aren't all observed effects up to now those
> resembling Newtonian effects?
>
> >(c) produce a gravitational-wave signal which is *vastly* too small
> > for LIGO to detect. A rough approximation to the emitted
> > gravitation-wave power is
> > P_GW = P_internal^2 / P_0
> > where P_0 = 4e52 Watts = (2e5 solar masses*c^2)/second
> > and P_internal = the non-spherically-symmetric power flow in the
> > emitting system
> > If you work it out, you'll see that this is WAY below LIGO's
> > sensitivity.
>
> Sorry, I don't understand what could have any
> kind of interaction involving 2e5 solar masses / second.
> I purchased Joe Weber's prize winning paper
> when I heard about the Gravity Research Foundation
> publications, and I did not see much that I understood,
> so please forgive me.
>
> >> I have no idea why black holes or neutron stars are talked about,
> >> ordinary binary stars would seem to merge at least as easy as any other
> >> because of their size and atmospheric drag, plus ordinary stars should
> >> flex and transfer material easier than dense stars.
> >
> >Black holes or neutron stars are 'talked about' because they are
> >much stronger gravitational-wave sources than ordinary binary stars.
> >This is because they are (or can be) moving much faster, in much
> >closer-together orbits. I think the gravitational-wave signal
> >grows as the 5th power of the orbital frequency, so a neutron star
> >or black hole binary shortly before merger, with an orbital frequency
> >of 100 Hz or more, produces a LOT more gravitational-wave signal
> >than a classical binary star (with an orbital frequency of 0.0001 Hz
> >or lower).
> >ciao,
>
> That does sound something like the Joe Weber paper
> describes, but it is not clear to me what the signal is supposed
> to consist of.
> If gravity is purely geometrical with no "flux" of
> interacting energy involved, I don't understand what the
> "signal" of gravitational radiation would be.
>
> This suggests to me that LIGO, etc., experiments
> are more to test _if_ gravitational radiation exists, yet they
> are built as if they will be observational instruments to
> observe _known_ phenomena.
>
> The reason for my pessimism is that I don't think
> there are any "effects" of gravity other than those that
> have been observed as "changes in motion".
> Taking the experiments to orbit before having
> some success with ground based instruments seems
> a little too optimistic.

Optimism is a fundamental component in grav-wave
production and this paper even says so.
http://arxiv.org/abs/astro-ph/0406037
LOL ... It does give some basis for a higher frequency of
rotation having a direct, indirect or imaginary influence
on the coefficient of optimism. :o)

Sue...

>
> Apparently LIGO data is being analysed, and I
> can't imagine why there should be data which is not
> of the gravitational wave signal type.
> I see no reason for me to have any further
> comments which can only show how little I understand. :-)
>
> But thanks for the reply.
>
> Joe Fischer

.

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