Gravitational Wave Detector on the Cheap
15 Oct 2012 12:35:08 UTC
Topic 196571
(moderation:
ArXiv blog entry..
There are some who can live without wild things and some who cannot. - Aldo Leopold
Gravitational Wave Detector on the Cheap
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I'd have to say this is a rather silly article in Fleet-Street/New-Scientist style. I wouldn't have expected MIT to go in for that type of rubbish ...
It declares the author's own superficial ( & deep ) ignorance of the topic rather than any terrible issue within the GW field of study. It's not a case of 'any old detector will do' but what one can do with a range of effective detectors. So if the frequency range available by pulsar timing studies was all that was needed, then so be it, but that's a bit like saying that while we can see photons ( thus confirming electromagnetic theory predictions ) we'll just study the red ones.
As for his/her deductions ( dutiful silence, unspoken fears etc ) based on what people aren't saying is just Area 51 nonsense. Also if he'd/she'd done any homework at all he'd/she'd have discovered rafts of documents over many decades predicting the challenges of progressive instrumental refinement to achieve detection. By his/her logic the Keck Telescope, say, is merely an expensive paperweight : as compared to Galileo's first telescope, which is where we should have stopped evidently.
He/she just doesn't understand that the IFO's are dedicated transducers ( GW to photon counts ), not incidental effects on another mode of observation whereby 'any remaining difference should be due to gravitational waves'.
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
I agree. Its a blog entry. A
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I agree. Its a blog entry. A personal opinion. It is not a vetted article from MIT. The author presents his views in a relaxed manner and that all they are, the author's views.
There are some who can live without wild things and some who cannot. - Aldo Leopold
I thought of cracking in with
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I thought of cracking in with a reply but couldn't be bothered signing up etc. But I note that Martin Hendry has appropriately replied by quoting Ray Wiess. As they're both LIGO members I'll let it be.
Cheers, Mike
( edit ) I forgot to mention that the original comment on detection difficulties came from Einstein himself - around 1918 I think. He despaired of ever confirming the GR prediction of waves due to the many orders of magnitude b/w typical electromagnetic and gravitational field strengths. The 'stiffness' of spacetime so to speak.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Take this arXiv 'Blog Entry'
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Take this arXiv 'Blog Entry' for what its worth.
First Observation of Gravitational Waves Imminent
There are some who can live without wild things and some who cannot. - Aldo Leopold
I had wondered who is writing
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I had wondered who is writing this blog and found this ( my highlight ) :
So it's 'shooting the breeze' type of stuff from this author. I ought stop expecting much rigour then, mind you the readers comments are often quite amusing.
[ The author is obviously rooting for the pulsar timing method, though has toned down on the 'expensive paperweight' line of deprecation for LIGO ( does he/she know of Livingston LIGO, which is currently further progressed in upgrade than Hanford ? ). Still doesn't understand - or disclose understanding of - the crucial matter of frequency related sensitivity and how different 'machines' can give complementary as well as competing results. Or that there might be more to a scientific endeavour than a Nobel touchdown for that matter ... ]
Cheers, Mike.
( edit ) With some things I read online I wonder if I'm occasionally being lured into Turing testing or unknowingly enjoined in some sociology prank. Or perhaps trolling has soared to even higher levels of refinement ( courtesy of FaceBook? ). Who can say? :-) :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
RE: I had wondered who is
)
I just think he is a theorist who doesn't get out of the office much.:-)
Edit: I think the author of this blog was changed recently.
There are some who can live without wild things and some who cannot. - Aldo Leopold
I think the wackiest part of
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I think the wackiest part of the article is the unattributed and un-explained graphic at the top. You could deduce that it is a plot of sensitivity ( units of gravitational wave 'strain' : the parameter used in the linearised far field approximation to GR ) vs frequency. Roughly centered on one cycle per year, hence the negative logarithm on the horizontal axis ie. there is ~ 3 * 10^7 seconds per year thus the inverse is b/w 10^[-8] and 10^[-7], so b/w -8 and -7 on a log scale. The vertical scale is quite a few orders of magnitude away from LIGO plots but they have units of strain per SQRT[Hz] and typically around 10^[-22].
Hard to compare the apple to the orange with that plot, so I viewed the source article. It turns out the colored bands variously refer to a 95% confidence interval ( data + their modelling ), and SNR = 2 and SNR = 8 over a five year integration. All of which is way lower than the long time pre-agreed LIGO standards for detection. But hey, despite only two good plates from the Principe expedition Eddington claimed a GR light deflection effect in the 1919 eclipse ! :-)
I still don't get why he says this :
[ Hint : if you're wrong, you get laughed at. It's measurement that defines scientific validity. ]
Cheers, Mike.
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal
Here is a link to the paper(
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Here is a link to the paper( its just a couple of pages) that the graph tries to summarize.
http://arxiv.org/pdf/1211.4590v1.pdf
From what I can grasp, it represents a 'convoluted' probability of the signal to noise ratio of a gravitational waves based on galaxies colliding. Which they surmised happens more often since the formation of the universe and they draw a conclusion that this increases the S/N ratio.
Like I said before ArXiv is the wild west of physics.
There are some who can live without wild things and some who cannot. - Aldo Leopold
RE: Here is a link to the
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Next to the Big Bang I guess galaxies colliding - or the merging of the humungous black holes thought to lurk within - will crack off a decent signal! They seem to be comparing their model to 'a pure dark matter simulation' in galactic halos so the prediction is with respect to that base. Which I might add is not identification of single GW source(s) but 'expected signal strength from the full population of binaries'. So they are looking for passing GW's in the generality rather than specific detections, so that focus is rather different from LIGO aims. Again, complementary rather than competitive : outside of Nobels that is. Anyway's best of luck to them!!
I'll chill out then ... even with a cheeky title like 'The imminent detection .. ':-)
Cheers, Mike.
( edit ) And I guess like any wave modality you are going to get the usual 'diffraction limited' angular error ( the first zero of the Bessel function from the image centre, see Airy disc ) - thus proportional to wavelength ( thus inverse to frequency ) and also inversely proportional to the aperture or characteristic dimension of the device. So by analogy to this the wavelength of a year's worth of one wave cycle ie. a light year, is going to dwarf even an Earth's diameter of baseline ( 'aperture' ). So no sky position discrimination what-so-ever.
( edit ) Browsing around that blog - I have a quieter week evidently - there's a really weird contributor ( Lucy Hay ? ) who is clearly well into Area 51 mode ie. 'I assert thus and hence you must disprove' with the inevitable corollary 'you didn't respond thus I must be right'. Quite humorous to read ... :-)
I have made this letter longer than usual because I lack the time to make it shorter ...
... and my other CPU is a Ryzen 5950X :-) Blaise Pascal