LIGO-Australia Proposed

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astro-marwil
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Message 115675 - Posted: 19 Jan 2012, 17:36:22 UTC
Last modified: 19 Jan 2012, 17:38:15 UTC

Hallo !

*** if two LIGOs haven't observed anything yet, ***


There aren´t only 2 detectors but thereof 4 (Geo660 and Virgo too) and the japanese one coming soon in operation as the 5th. All they are in a belt on the north half of the globe.
My point of view is: As long as there is no proven evidence of GW by more than one of these detectors, it is irresponsible to install a 6th detector, as they realy can´t be paid just from our pocket money. To make plans, also detailed plans, for the days just after the advent of that proven evidence is fine, so one can start off immediately.

We are searching now for 6 years for this waves without success, with detectors that have the neccessary proven sensitivity to find something valuable. The only result now, that has been concluded is, that neutronstars are obviosly more precisely ballshaped than allowed by theoretical calculations. At minimum 2 detectors become upgraded to 10 fold sensitivity just now. By schedule they will start the testphase in the next year and come to regular operation one year later (2014). To check, whether there are GW or no and to take basic measurements, the existig 5 detectors are more than sufficient.

Of course, if there would be found no GWs or theire strenght is engraving lower than expected, that would be very spectacular and a strong indicator for some sort of new physics.

Kind regards
Martin
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Message 115677 - Posted: 19 Jan 2012, 21:50:02 UTC - in response to Message 115675.

Hallo !
*** if two LIGOs haven't observed anything yet, ***


There aren´t only 2 detectors but thereof 4 (Geo660 and Virgo too) and the japanese one coming soon in operation as the 5th. All they are in a belt on the north half of the globe.
My point of view is: As long as there is no proven evidence of GW by more than one of these detectors, it is irresponsible to install a 6th detector[...]


Again, as I understand it (correct me if I'm wrong), the original plan for LIGO Astralia was this:

"the LIGO Laboratory decided to explore the
option of shifting one of the Advanced LIGO detectors
from the US to a southern hemisphere location"

quoted from here.

http://www.aigo.org.au/aigo_web_docs/LIGO-AustraliaProposal.pdf


HBE
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Profile Mike Hewson
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Message 115678 - Posted: 20 Jan 2012, 1:38:39 UTC - in response to Message 115675.
Last modified: 20 Jan 2012, 1:51:26 UTC

...with detectors that have the neccessary proven sensitivity to find something valuable

Hi Martin!:-)

That is not quite the case. While it is true that upper bounds have been placed on certain models - the neutron star asymmetries that you refer to - alas that's not a detection per se. Which is the rub ...... and bear in mind that the detectors aren't equivalent for a host of arcane reasons.

The trouble is that gravitational waves are a leading edge hypothesis involving 'first use technology', so 'proven' is somewhat of a tail-chasing argument. I really should dig out those late 90's studies for reference here. The precise reason for making predictions back then was to defray the very issue you have raised now. Specifically it was anticipated that a 'scorecard' would be desired. So while we are all gunned up to get a GW detection - because that would be new, cool, interesting etc - Nature may not actually provide us with one. But if they don't exist, then we have discovered a novelty indeed.

What I should add is that the experience with early resonant bar detectors - Joseph Weber at al - induced considerable caution within the field as to what ought be claimed, expected or touted as a detection. Again the extremely low order of the effect is the prime issue.

Cheers, Mike.

( edit ) To be exact : NOT detecting certain gravitational wave patterns from neutron stars with 'mountains' is also consistent with

- gravitational waves NOT existing, PLUS

- neutron star asymmetries of a degree constrained by other factors

( edit ) Certainly the Einstein Telescope has prior gravitational wave detection as an absolute prerequisite for it's construction. All of these projects are worth a bucket of someone's money, so it is all the more important to be clear about expectations.
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Message 115679 - Posted: 20 Jan 2012, 2:47:04 UTC
Last modified: 20 Jan 2012, 2:52:35 UTC

If you will permit a digression on the significance/detection issue ...

... a core problem with Joseph Weber's work was that the significance level for a detection claim was made after the fact. One can take any measurement setup for pretty well any physical quantity you like and there will be variance from one reading to the next. At the deepest level you could blame quantum mechanics for this - but generally you don't need to invoke that - and discover that random data sets ( those without a true underlying reliable trend ) are as common as mud. Thus adjusting some detection line/level up and down to classify those measurements 'under' as negative and those 'over' as positive will give a genuinely consistent labelling from even a purely random process. The trouble is that when you extend that to another random data set you'll have to reset the threshold to recover the same degree of significance ( or probability if you like ). Choosing another set, another adjustment etc ... as exhaustion permits. In Weber's case no other data set affirmed his findings. Note this is not necessarily a deliberate scientific fraud. Not at all. It can merely be poor forethought, insufficient regulation of control cases, wishful thinking ( we want to find a GW, so we will ), and good old luck/happenstance ( to name but a few pitfalls ).

[ So we wish to do better than being recurrent fools in the inevitable presence of random variation. ]

This you could label as the 'Methinks It Is Like A Weasel Problem' ( MTIILAWP ) see Shakespeare's Hamlet :

Ham. Do you see yonder cloud that ’s almost in shape of a camel?
Pol. By the mass, and ’t is like a camel, indeed.
Ham. Methinks it is like a weasel.
Pol. It is backed like a weasel.
Ham. Or like a whale?
Pol. Very like a whale.

... meaning that random patterns, like clouds, can suit any tendency you like. On the proviso that one is willing to accept post-facto alteration of expectations. In Hamlet's case it is better to decide by pre-drawn weasel templates, say, what a weasel shape is. And then go searching amongst the clouds.

The challenge is greater for GW's though because we've never seen the weasel ( or a camel, or a whale for that matter ) as it applies to this type of measurement. Hence 'orthogonality' or 'intersection' is the key. So if one can reproduce ( to some agreeable tolerance at least ) an effect, elsewhere in time/space then we will have greater confidence in the 'reality' of some phenomena ( eg. bumps on neutron stars ). Imagine our delight if a GW frequency from a sky direction matched ( or had a simple integral relation to ) a well studied radio pulsar ! :-)

So for instance, within the medical research field the MTIILAWP peaked when deliberate choices of inclusion and exclusion of whole data sets occurred. Drug companies especially were fond of simply 'losing' results which were not favourable to their nascent product's future commercial success. Clouds with the wrong shape. Thus we only heard of the few studies which glowed and not the ( usually rather larger ) remainder which spluttered and faded. Hence like exit interviews on minefield crossing participants, they will all be winners and grinners :-)

We found out later of course, when the general public was exposed to the thing, what their true potential was. Now I could give you ( but I won't because I haven't a desire for bankruptcy and litigation ) a seriously worrying list of major well selling drugs that put simply are failed products for the purpose intended. Fortunately I can fail to prescribe/recommend them, and also freely inform the patient of the naked truth within the confines of a confidential medical consultation. But alas they persist on the chemist/supermarket shelf on account of momentum, advertising, urban-myth or any other sociological factor of your choice.

Plus my usual admonition : beware fields of inquiry which aren't even aware of these issues, or pay lip service to managing them. Such fields are also as common as mud.

Cheers, Mike.
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This material is based upon work supported by the National Science Foundation (NSF) under Grants PHY-1104902, PHY-1104617 and PHY-1105572 and by the Max Planck Gesellschaft (MPG). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the investigators and do not necessarily reflect the views of the NSF or the MPG.

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