Surely you are not suggesting that Weber's work was critical to this discovery>? Carving up a bunch of aluminium cylinders that clang together and then calling them Weber Bars just to impress bankers is hardly major progress in this field.
You may owe Kip an apology - he has worked tirelessly over the decades. In fact Kip also looked at the detection of gravitational waves in the 1960s but the technology was not advanced enough at that point in time.
Surely you are not suggesting that Weber's work was critical to this discovery>? Carving up a bunch of aluminium cylinders that clang together and then calling them Weber Bars just to impress bankers is hardly major progress in this field.
Weber's work has pushed forward the experimental work on the detection of gravitational waves. His results have been questioned and disputed, but his pursuit for the technological advances were critical. There were many 'bar detectors' around the world, following Weber's work. Much advanced in measurement characterisation has come out of these experiments. So directly, you could say that his work was not critical, but indirectly his work was critical in the pursuit of the detection of gravitational waves.
Quote:
Originally Posted by Eratosthenes
You may owe Kip an apology - he has worked tirelessly over the decades. In fact Kip also looked at the detection of gravitational waves in the 1960s but the technology was not advanced enough at that point in time.
Rainer Weiss (MIT) was the first who performed a detailed analyses of the inner working of a laser interferometer gravitational wave detector, on which LIGO (and the other interferometers such as Virgo, KAGRA and GEO) are based. Both Kip and Rai (as well as Drever) were instrumental in the development of these instruments over the years.
Weber's work has pushed forward the experimental work on the detection of gravitational waves. His results have been questioned and disputed, but his pursuit for the technological advances were critical. There were many 'bar detectors' around the world, following Weber's work. Much advanced in measurement characterisation has come out of these experiments. So directly, you could say that his work was not critical, but indirectly his work was critical in the pursuit of the detection of gravitational waves.
Rainer Weiss (MIT) was the first who performed a detailed analyses of the inner working of a laser interferometer gravitational wave detector, on which LIGO (and the other interferometers such as Virgo, KAGRA and GEO) are based. Both Kip and Rai (as well as Drever) were instrumental in the development of these instruments over the years.
...as well as the Russian input on designing and stabilising the 40kg mirrors.
Lots of contributions into these massive projects.
I hope you're not suggesting that just because Eratosthenes invented teh scientific method in ~190BC when he measured the circumference of the earth that HE played a critical role in the detection of the Cosmic background radiation or the positron?
Interesting Australian link up - from the MIT LIGO summary.
"Australian groups are also making capital contributions to Advanced LIGO. A consortium of Australian National University and the University of Adelaide are providing Hartmann phase sensors, a pre-lock length stabilization system, and specialized beam-pointing equipment to Advanced LIGO. ANU and Adelaide are full partners in Advanced LIGO."
Surely you are not suggesting that Weber's work was critical to this discovery>? Carving up a bunch of aluminium cylinders that clang together and then calling them Weber Bars just to impress bankers is hardly major progress in this field.
You may owe Kip an apology - he has worked tirelessly over the decades. In fact Kip also looked at the detection of gravitational waves in the 1960s but the technology was not advanced enough at that point in time.
Weber Bars
You are oblivious to the fact that Weber was the driving force in creating the experimental science behind gravitational waves.
Whereas Einstein described propagating gravitational waves in the arcane mathematical language of time dependent coefficients of the perturbed Lorentz metric, which was cryptic to most people including experimental physicists, Weber showed that if gravitational waves were able to deform an elastic body then it should be possible to drive electromechanical transducers which would provide the signal for the wave's presence.
Your comments on Weber are woefully ignorant and demeaning.
Here is what Kip Thorne had to say about Weber in an excerpt from a Washington Post article after the discovery.
Quote:
One of the people who studied under Weber was Kip Thorne, who co-founded LIGO and also devoted much of his career to the search for Einstein’s waves. Thorne came to Washington Thursday to be part of the big announcement — his picture is on our front page today — and he took pains Thursday to credit Weber as an inspiration.
When I asked Thorne after the news conference about Weber’s claims of discovering gravitational waves, Thorne corrected me: He said Weber only claimed to have found evidence for such waves, and didn’t claim an actual discovery.
Perhaps that’s a fine distinction, but let’s move on: Weber also was a pioneer of lasers, and he arguably should have shared in the Nobel Prize for their invention. LIGO is a masterpiece of laser-based science and delicate instrumentation. Keep in mind, the gravitational waves are not detected directly but are inferred through their effects on a split laser beam. The founders of LIGO (including Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT) derived many of their ideas and technologies from Weber’s groundbreaking work.
Thorne told me, “He really is the founding father of this field.”
~3 solar masses were converted into energy and radiated in the form of gravitational waves.
I am wondering.. if grav energy in form of waves are being emitted, they should be also absorbed, right? Moving and shaking, compressing and stretching masses around..
What effect (on us) would have been if this merger were closer, say in Milky way.. or Magellanic clouds?
If there was a (measurable) effect on light path as consequence of this distant merger, surely the effect would have been very visible if we were closer to the merger?
And how close we should be to see/feel anything?
DECam searches for optical counterparts of the first gravitational wave event GW15091
Science Daily on 15th February reports that the Dark Energy Survey used the 3 square-degree, 570-megapixel
Dark Energy Camera (DECam) imager mounted on the
Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory
in Chile to search for any visible light that might be associated with the
black hole merger that LIGO detected.
Working in collaboration with the LIGO team, they began the search within a day
of the gravitational waves being detected.
Quote:
Originally Posted by Science Daily
They faced a significant hurdle since the search area was so large: 700 square degrees of sky, or about 2,800 times the size of the full moon. The team observed large swaths of this region several times over a period of three weeks but did not detect any unusual bursts of visible light. They used this information to place a limit on the brightness that can serve as a benchmark for future attempts.
“This first attempt to detect visible light associated with gravitational waves was very challenging,” states Berger, “but it paves the way to a whole new field of astrophysics.”
The team plans to continue searches for visible light from future gravitational wave sources.
Results in The Astrophysical Journal Letters paper entitled "A DARK ENERGY CAMERA SEARCH FOR AN OPTICAL COUNTERPART TO THE FIRST ADVANCED
LIGO GRAVITATIONAL WAVE EVENT GW150914" by Soares-Santos at. al. here - http://darkenergysurvey.org/ms-11.pdf
and in The Astrophysical Journal Letters paper entitled "A DARK ENERGY CAMERA SEARCH FOR MISSING SUPERGIANTS IN THE LMC AFTER THE
ADVANCED LIGO GRAVITATIONAL WAVE EVENT GW150914" by Annis et. al. here - http://darkenergysurvey.org/lmc-paper-v11.pdf
yes, all sorts of data comparison of before and after the event being measured on Earth! soooo intriguing!
I read about a longterm Pulsar project in which the goal is to detect GW passing by their system by constantly measuring it's pulse and looking for deviations (Pulsar J1909-3744). Their object of interest is 195 light years away somewhere in Taurus.
So, without knowing exactly where the two BH merged, it's still possible that the GW already have passed by the Pulsar, too, and the deviation stayed undetected. Or maybe it will take another 100 light years for the GW to reach J1909. I don't know.
How exciting is the stuff the Pulsar project members can learn about their assumptions and methods, now, that they know they didn't see what they were looking for, even though it was indeed there: marvellous!
(The article I had read bout it was pre-discovery publication so it didn't state anything about them crawling back into the data or anything, yet.)
Or the Ligo teams themselves:
they can try and understand why their two "rulers" measured different amplitudes in the build-up - and only during the merger-moment became quite congruent. >>image
It could be a tool's problem of one or the other Ligo - or both.
Or it might be a predictable GW behaviour, previously unthought of. Especially in the light of congruent "chirp" in the merging moment. Assuming if there was problem with the tool, the merging moment would not show up as congruent as it was, either.
Bojan has an interesting question, I think: how big and how close by would a GW-creating event have to be so humans would feel/see something?
It was the spanish-accent-lady in the press conference (16:45 - 17:45) who explained that the amplitude of the signal tells the approximate distance as mathematically predictable.
That's not answering Bojan's question, of course, but if one of us knew how to draw predictions relating to event distances, the question would be possible to answer here in the forum.
Another point of view as to how the GW event did indeed already have a palpable effect on humans:
by a delay of 5 months after the detected GW on Earth,
our brains use electrochemical energy to discuss the event.
The time difference of 5 months was caused by the particular form of human observation: scientific publishing procedures being the "sense of perception" of the humans in audience.
Of course, that's rather "quantum" in this case synonymous with "esoteric".
But it IS an observable effect the GW had on humans.
Could be used to develop formulae to empathically predict socio-energetic reactions. Or whatever. Maybe stuff for a sci-fi novel.
But certainly, the energy we as IIS members put into discussing the September event,
would have a higher strain amplitude than the GW of 1bn ly away.
oh, this socio-energetic detector... reminds me of the noosphere project. http://noosphere.princeton.edu
So it's not too "quantum" for humans not to have attempted to scientifically measure and experiment with it.
Although the tool used has proven itself to be inadequate, I think.
Like Weber's bar thingy for GW.
Or the Ligo teams themselves:
they can try and understand why their two "rulers" measured different amplitudes in the build-up - and only during the merger-moment became quite congruent. >>image
It could be a tool's problem of one or the other Ligo - or both.
Or it might be a predictable GW behaviour, previously unthought of. Especially in the light of congruent "chirp" in the merging moment. Assuming if there was problem with the tool, the merging moment would not show up as congruent as it was, either.
Hi Silv,
Both interferometers saw the same 'amplitude' signal. The LIGO interferometers ran at about 1/4 of their design sensitivity, as well as at the lower 'frequency range' they ran even 'more' noisier. So hence only when the merger signal (say amplitude) came above the 'nominal' noise floor of the detectors, they could see the signal. There is a bit more data analyses in there, but that is the basic limit.
If the detectors were much more sensitive in the lower frequency band (<< 1 Hz), then the orbital signal well before the merger event could be seen. This unfortunately, even at design sensitivity, is not going to happen with LIGO anytime soon..
As for the Pulsar Timing Array, that is a very interesting results. According to the models, they should have seen something and they didn't. So that says something about the models, which in turn is very interesting.
Science Daily on 15th February reports that the Dark Energy Survey used the 3 square-degree, 570-megapixel
Dark Energy Camera (DECam) imager mounted on the
Blanco 4-meter telescope at the Cerro Tololo Inter-American Observatory
in Chile to search for any visible light that might be associated with the
black hole merger that LIGO detected.
Thanks Gary, hadn't seen those!
Looks like they initially didn't know that it was a binary black hole system, as they anticipated it would be a binary system with a neutron star. I wouldn't think a BBH would have emitted anything, but then that is the unknown we want to see.
~3 solar masses were converted into energy and radiated in the form of gravitational waves.
I am wondering.. if grav energy in form of waves are being emitted, they should be also absorbed, right? Moving and shaking, compressing and stretching masses around..
What effect (on us) would have been if this merger were closer, say in Milky way.. or Magellanic clouds?
If there was a (measurable) effect on light path as consequence of this distant merger, surely the effect would have been very visible if we were closer to the merger?
And how close we should be to see/feel anything?
Gravitational waves unlike electromagnetic waves hardly interact with matter.
Gravitational waves act like a mass spring damper system where the amplitude and energy decay over time.
By the time GW150914 reached us only a minute amount of the original energy and amplitude remained.
Not sure of the effects of a gravitational wave originating from the distance of the LMC but nearby you would be flattened in one direction and streched out in the perpendicular direction.
From it I gather that in the interaction between mass and gravitational wave, no energy is absorbed (unlike in case of EM waves)?
I would expect something like tidal effects due to gravitational field gradients that propagate through space/time.
Was that way of thinking in the core of Weber's idea (GW prompting the metal cilinder to vibrate at mechanical resonant frequency and picking those vibrations with piesoelectric sensors)?
Quote:
Originally Posted by sjastro
Gravitational waves unlike electromagnetic waves hardly interact with matter.
Gravitational waves act like a mass spring damper system where the amplitude and energy decay over time.
By the time GW150914 reached us only a minute amount of the original energy and amplitude remained.
Not sure of the effects of a gravitational wave originating from the distance of the LMC but nearby you would be flattened in one direction and streched out in the perpendicular direction.
From it I gather that in the interaction between mass and gravitational wave, no energy is absorbed (unlike in case of EM waves)?
I would expect something like tidal effects due to gravitational field gradients that propagate through space/time.
Was that way of thinking in the core of Weber's idea (GW prompting the metal cilinder to vibrate at mechanical resonant frequency and picking those vibrations with piesoelectric sensors)?
this is a bit old, but may be useful summary of gravitational wave energy? http://ned.ipac.caltech.edu/level5/E...hn/boughn.html
It seems to be an exceptionally inefficient way to transfer energy and only viable when the source is capable of generating vast amounts of energy in a short time - such as the black hole merger where 3 solar masses were converted to GWs in a fraction of a second.
Ray,
I had in mind exactly what this article describes when posting my question.
Appropriate (very small.. the factor is 1e-43, compared to EM interaction with electrons) part of energy carried by GW must be absorbed by mass .. and possibly dissipated within the receptor as heat. Similar/analogous to EM.
Now, we have here 3 solar masses converted into GW energy.. this is a lot of energy and this must interact noticeably with nearby objects... it would be interesting to put that into our everyday perspective.
"How far away do you have to be from this kind of black hole merger to live to tell the tale? Stuver: For the black hole binary we detected with gravitational waves, they produced a maximum change in the length of our 4 km (~2.5 mi) long arms [of] 1x10-18 meters (that is 1/1000 the diameter of a proton). We also estimate that these black holes were 1.3 billion light-years away.
Now assume that we are 2 m (~6.5 ft) tall and floating outside the black holes at a distance equal to the Earth’s distance to the Sun. I estimate that you would feel alternately squished and stretched by about 165 nm (your height changes by more than this through the course of the day due to your vertebrae compressing while you are upright). This is more than survivable."
The above quotation summarizes the issue of noticeability.. provided the calculation involved was correct.
From it I gather that in the interaction between mass and gravitational wave, no energy is absorbed (unlike in case of EM waves)?
I would expect something like tidal effects due to gravitational field gradients that propagate through space/time.
Was that way of thinking in the core of Weber's idea (GW prompting the metal cilinder to vibrate at mechanical resonant frequency and picking those vibrations with piesoelectric sensors)?
Strictly speaking it is not a tidal effect. The stretching and compression associated with a tidal effect is due to the action of a gravitational force acting in one direction. In a gravitational wave there are two "distinct forces" acting perpendicular to each other.
Weber was able rewrite the motion of test particles effected by gravitational waves using a model where a volume of space time is occupied with a elastic medium.
The medium is subject to deformation by the GW and in theory be detectable with piezoelectric sensors.
