Bruce AllenForum moderator
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After several years of analysis and post-processing work, the results of the Einstein@Home search for gravitational waves in the full LIGO S5 data set are now publicly available. The paper can be found here http://arxiv.org/abs/1207.7176.
The results are negative: no statistically-significant gravitational wave signals have been detected. However the search excluded signals with a greater level of sensitivity than previously achieved. For example, in the 0.5 Hz-wide band at 152.5 Hz, signals with intrinsic strain h0 greater than 7.6e-25 are excluded with 90% confidence.
Einstein@Home will continue to search for gravitational-wave signals. In the long term, we are optimistic. The LIGO and VIRGO and GEO detectors are all undergoing hardware upgrades to improve their sensitivity, and Einstein@Home will continue to develop and employ better and more sensitive data analysis methods.
Bruce Allen
Director, Einstein@Home
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Thank you for the information.
Just wanted to ask - if gravitational waves exist - what is the speed of such waves ? Certainly more that speed of light because gravitation is only one stuff which can spread from inside black hole to outside world.
The gravitational wave - a perturbation of the gravitational field "ripple" fabric of space-time propagating with the speed of light. Gravitational waves are predicted by general relativity (GR), and many other theories of gravity
Bruce, thank you for "project science update"! Any new paper or other information about it interesting for us.
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Thank you for the scientific update! I have good hope that the project will find a gravitational wave. The sensitivity updates to the detectors sounds very promising as well.
Thank you and the team for all you do. We look forward to helping through future workunits ;)
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Just wanted to ask - if gravitational waves exist - what is the speed of such waves ?
At the speed of light is the expectation and that would be consistent with other knowledge. But being a scientific enterprise this a matter for verification. One especial hope is to be able, one day, to correlate the timing of some event ( supernova say ) with several modes to then compare. This occurred incidentally with SN1987A using visual photons and neutrinos, but uncertainties remained with timings at source ie. when did they leave the scene? What a hoot it would be to have a set of such observations and confident timings across detection techniques.
Certainly more that speed of light because gravitation is only one stuff which can spread from inside black hole to outside world.
I think the consistent interpretation is that once a black hole is formed then we can perceive only from the event horizon and outwards. By definition really. For us on the outside, that surface is our only knowledge of the entirety of the hole - mass, charge and angular momentum.
[ For me the key anti-intuitive issue in relativity is time. When viewed from a distance objects descending to an event horizon never quite get there ( in finite time ). All photons coming up from the horizon get their frequency shifted to zero, which is also their zero of energy. So we can never know ... ]
Cheers, Mike.
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
It seems to me that Gravitational Waves would be created primarily from black holes which have the strongest gravitational force that we know of. Unfortunately we can only see or record data to the event horizon. What lies beyond that is only for the imagination to guess. I would consider that an extremely strong gravitational wave would be produced on the other side of the hole wherever and whenever that may be. Perhaps some day we may discover this but certainly not today. Just keep searching for we really know very little about the universe but new discoveries are being made every day.
So am I wasting my time with this?
So am I wasting my time with this?
Just think of people like myself crunching SETI@home in search of extra terrestrial intelligence!
Tullio
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So am I wasting my time with this?
Just think of people like myself crunching SETI@home in search of extra terrestrial intelligence!
Tullio
Strange answer but I probably got your point.
Imo, you're not wasting time, neither with E@H nor with Seti or any other project. Maybe the main goal won't be achieved but at the same time you can improve scientific methods, learn more about large-scale data processing, signal processing and so on. To me, things like that are never a waste of time, so the answer to your question depends on your POV.
Michel
So am I wasting my time with this?
Hmmm? :-)
This project is part of a scientific enterprise which has substantial/ambitious long term goals. A good deal of what we do - individual workunits - is not going to 'discover' particular celestial objects, as we are looking for uncommon beasts. Put another way, if it was 'easy' then the scientists wouldn't be needing our help and Einstein At Home wouldn't exist. But we have certainly to date helped to formulate methods of attack for later searches when the instruments have been improved to higher sensitivity ( Advanced LIGO ). We function as a huge programmable calculator ( anyone remember those, eg. HP-29C's ? ).
Having said that : the absence of gravitational wave detections down to certain levels - and we all participate in that finding - has already helped constrain the models that describe the things we are looking for. That's actually more important than it sounds because it impacts on ideas like the 'equation of state' of a neutron star ( how its parts interact to determine deformation when spinning ), the distribution of neutron stars out there ( because one of our search parameters is distance away from us ) and such like. Theorists are clever poppets who always yearn to deduce things, even when the Baskervilles hound doesn't bark.
So that's a 'productive science' answer. Other than that take your pick : it's fun and interesting, it's an excuse ( if needed ) to buy better hardware, it keeps one out of the pub ( if that was a problem ), one gets to meet & talk with people from everywhere ( I've yet to find a downside to that ), it stimulates the imagination, it provokes one to learn and research this topic and the associated ones .... <write your personal stimulus here> ..... :-):-)
Cheers, Mike.
( edit ) Whoops, forgot .... you get to rub shoulders with the smart and helpful people at AEI and elsewhere that run the show :-) :-)
[ Phew! Nearly lost my job there .... ]
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
I have a degree in Theoretical Physics,1967 vintage, and sometimes I am at loss understanding today's physics. But I crunch also Test4Theory@home, LHC@home,QMC@home,climateprediction.net besides Einstein@home, always trying to learn something. But SETI@home has the merit of having started all this all,unlike Folding@home which has remained an "ortus conclusus", a walled garden.
Tullio
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Here's my picking of curious stats from the paper :
- 117 authors by the end of the B's. I then gave up .... :-)
- contribution from 95+ institutions world wide.
- 25,000 CPU (Central Processing Unit) years to produce the S5R5 analysis.
- 121 harmonic lines of the mains power frequency of 60Hz ( Table VI, and they're all over the place in Fig. 9 ).
- around 10^11 'candidates' were returned from users machines with S5R5, at about 10^4 for each work unit. These were then subject to automated filtering back at AEI using Atlas to yield under a dozen 'survivors' for 'manual' attention ( putting aside the 'detection' of deliberate signal injections ).
- if my understanding of equation (4) is correct then the difference in the moments of inertia ( Ixx - Iyy, a measure of 'wobble' ) for a neutron star must be quite enormous to get any signal at all, given the placement of G, c^4 and d in the right hand side ..... you wouldn't want a smack in the face from that! :-)
- the sky is divided into ~8500 smaller areas/points for Hough purposes, from 10^3 to 10^5 otherwise ( depending on frequency ).
- processing 'errors' at less than 0.045% of work units.
- false alarm ( random noise mimicking a signal ) probability below 10^[-16]
- S5R5 reduced the upper limit on the spacetime strain level by a factor of 3 compared with S5R1. It's under 10^[-24] around the detector's 'sweet spot' in the 100Hz to 200Hz band.
- all injected signals that should have been found with the sections of data used were found.
This is my Sad Panda bit :
No evidence for continuous gravitational waves has been observed in the search presented here.
This my Oh Well, There Is An Upside bit :
It has long been expected that searching a large parameter space for CW signals will require hierarchical semi-coherent searches. This analysis is a milestone towards that goal, and we expect that future analyses will build on the tools developed here.
Cheers, Mike.
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
Think of it this way. We accept that gravitational waves do not exceed light speed since we accept that mass cannot exceed light speed no matter how strange the mass may be. Wikipedia under Gravitational Waves is a good starting point on the subject.
I think attenuation of gravitational waves should be considered. As still unknown property of space-time... or black matter.
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I think attenuation of gravitational waves should be considered. As still unknown property of space-time... or black matter.
I believe the GR prediction is like reciprocal of distance; so if we knew the strength at source, the strength here, and the distance, then we could test that. There's a heap of fascinating stuff that begs for study once we can crack into this area ... :-)
Cheers, Mike.
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
I mean additional attenuation. "Viscosity" of dark matter or spacetime.
As for zero output - 130 years ago Michelson–Morley experiment aka "most famous "failed" experiment" had the same two-arms interferometer.
And its "zero" was the begining of absolutely new physics :)
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I mean additional attenuation. "Viscosity" of dark matter or spacetime ......
Oh sorry, I see ..... yes, like the Coal Sack. I suppose you'd also get lensing effects too.
Cheers, Mike.
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"I have made this letter longer than usual, because I lack the time to make it short." - Blaise Pascal
Bernd MachenschalkForum moderator
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Another indirect gravitational wave proof.
BM