LIGO's "New Ear for the Universe"

http://www.bbc.com/news/science-environment-34298363

The mirrors have been made ultra-sensitive, and the data from them is to be crunched by a bank of supercomputers to look for evidence of a gravitational wave.

Kip Thorne: "We are there; we are in the ball park (sensitivity) now. It would be very surprising if we don't detect any gravity waves".

 

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Great stuff!
How long before the modified LISA is launched?

 

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I suspect, unless LIGO actually succeeds, LISA will likely be shelved and replaced by missions with a greater probability of a mission success.

This article is the first one I've read with details about whether the 2010 upgrades were successful or not. The specifications for the planar smoothness of the mirrors were the subject of considerable discussion elsewhere. It is a tribute to Thorne's ability to stick it out that the upgrades were completed as planned. I think Joe Weber would have approved. Even if it fails, it's eventually a good thing to get such design attempts worked through to the end, if for no other reason, so we need not try this approach ever again.

I don't believe I ever mentioned, failures sometimes contribute more to advances of science than successes, even if this is not generally appreciated as much as a moon landing or the discovery of the Higgs boson.

I'm not the only one who noticed that gravity wave detection had been long promised, but LIGO has been so far short on results. At least, I no longer fault their principle consultant, who does have a track record for accurate predictions, as of 2014.

If this eventually works, do you believe it would be able to detect any remnants of the original inflation? That would be über cool.

 

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Here's something else to think about in connection with the detection of gravity waves. According to:

https://en.wikipedia.org/wiki/Gravitational_wave#Power_radiated_by_orbiting_bodies

The expression for the power of a gravity wave is given by:

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In the case of the Sun-Earth system, this expression evaluates to about 200 Watts. From where would this 200 Watts of energy be sourced? Well, from the center of mass of the Sun-Earth system, of course. In other words, the gravity waves would originate from a point that is very close to the Sun's core. How long do you suppose it would take for the energy of that gravitational wave to propagate from the core of the Sun to its surface? Would the thermodynamic mechanical equivalent of heat act to damp (reduce to zero) any such propagation long before any gravitational waves from the Earth orbiting the Sun, or even Jupiter orbiting the Sun ever reached the photosphere? Very likely. The conversion of tidal forces into heat is well known, and this likely serves to damp the propagation of the piddling 200W worth of gravity wave energy from the Earth orbiting the Sun long before it reaches the surface of the Sun, EVEN IF it were the case that gravity waves could actually propagate in a medium that is devoid of inertia, which would be questionable if it were predicted by anyone but Einstein himself in 1916. Just because gravity itself and time dilation can extend beyond the surface of a gravitating object is no assurance that gravity waves can do likewise, or that if they can, a means can be found to monitor them as they propagate.

In order to absorb such energy, you must have an instrument that is attuned to absorbing some of the energy of the wave, in the same manner that photons are absorbed by the retina of our eyes so that our neurons can perceive where they are coming from. If LIGO has an aperture, which direction is it pointed? The inability of an instrument looking for weak signals and an inability to concentrate that energy, is something like expecting to make a telescope out of an empty tube. But don't laugh! Tycho Brahe did exactly this, and with the greatest scientific efficacy imaginable. Without his careful observations, Kepler's work would have amounted to nothing.

Even in the case of orbiting black holes, the EH of those extend in the direction of the opposing BH, rendering any chance of observing energy of any kind originating from the interiors of the BHs rather remote. If we do not observe gravity waves from these rare cataclysmic events, that in itself would be evidence that the tidal forces at work interior to them likewise serve to render even gigawatts of gravitational wave energy to a much reduced level before getting absorbed as though they were photons in the final shape of the EH. Perhaps such gravity wave events provide their own form of shielding. Just because gravity extends beyond the EH is no absolute assurance that gravity waves can, but if they could, that would be equivalent to information leaving the interior of a BH before it completely evaporates, wouldn't it?

The term "black hole" was not even coined until 3 years after Einstein's death, so he could not possibly have a quote, much less a calculation about this possibility, so don't bother to look for one.

 

The last I heard ESA is going it alone after NASA pulled out.
Shame that economics can be such a drain on scientific projects.

Although gravity waves are so far only indirectly validated, I see no reason why they do not exist, simply on the basis that if spacetime can be warped and curved in the presence of mass, and undergo frame dragging in the presence of a rotating body, then why gravity waves would not be produced by any cataclysmic event.
I have no doubt they are present, the problem is having the technology to detect at that sort of level, remembering the highly precision gyroscopic spheres that needed to be constructed to validate spacetime curving and frame dragging by GP-B

No problem with that.....
https://theconversation.com/failure...-and-different-from-phony-controversies-37217

That doesn't worry me a great deal. The more we learn about nature and the universe around us, the more difficult the next steps seem to be.
Detecting gravity waves was never going to be easy, as their intensity falls off rather quickly as the emanate from the source.
Viable Nuclear fusion reactors was never going to be easy. I don't believe that such research should be dropped as a result.
String theory and its derivitives and a potential QGT is another extremely difficult goal. Still we'll keep on keeping on!

 

Think of what happens when a bound electron transitions to a lower energy state by emitting a photon. The electron is what accelerated. The photon cannot be said to have accelerated because it travels at c immediately after it has been created, and forever after.

If an analogous thing occurs with gravity waves, the mass which accelerates most will be what emits the most gravitational radiation. In the case of the Sun-Earth or even Sun-Jupiter system, obviously it is the smaller body that accelerates the most, but which of the two is more likely to emit a higher energy gravity wave? Recall the principle of equivalence. If you drop a stone, is it the Earth that produces the gravity wave from that, or the Earth? Or to put it another way, which one endures more tidal forces from the interaction?

I'm only suggesting, all of the energy of the gravity waves even of cataclysmic events may actually be absorbed before it ever leaves the surface of a gravitating body, as if it were an electron emitting a photon from inside an electrically conductive and shielded, opaque box. In such an event, this would be a universe in which gravity waves were mostly absorbed or otherwise attenuated before their rather small energies could escape, much less be detected by even the most sensitive detector. The gravity wave universe may prove to be them most difficult one for us to observe.

 

About LISA.
It seems their ready to launch (November) a mission to test some of the technology which will be used on the LISA main project, which is hopefully due to be in 2030, that seems like a lifetime away!

http://www.bbc.co.uk/news/science-environment-34152577

 

Well, at least LISA has something resembling an aperture.

 

Actually, of course not! Evidently you have zero grasp of the nature of wave generation in general. At best, assuming GW's actually exist, there would be a gradual transition from 'near-fields', indistinguishable from Newtonian gravity to within many times the radius of Sun-Earth system, to a supposed radiation zone, arbitrarily established from roughly a quarter light-year radius on out! All that could be said is there would be a notional center of GW symmetry corresponding to the Sun-Earth centre of mass. And this ignores the contributions from orbits of all the other planets.

A non-sequitur like that does not deserve a reply other than to point out it is a non-sequitur following on from a false premise. As I have mentioned before in SF quite a few times, it's quite easy - if you know what to look for - to prove that the standard GR predicted GW's of Kip Thorne's and others dreams are impossible. And, once again, no I won't elaborate or justify that claim here. But will state ahead of time that upcoming BICEP3 will 'bite the dust' just as surely as the abject failure that was BICEP2.

If the hugely confident expectations of 'many detections per year' for the updated LIGO is born out, for sure it will be found the mode signatures will be other than that of the quadrupole mode TT-gauge GW's of GR. Either way, detection or not, it will lead to a crisis of confidence in GR.

 

That's like expecting the extended electric field of an electron to be the place where photons are emitted. Is it? If so, how much should we wager?

 

You wish to wager on correctness of our respective viewpoints/claims? Sure - just state what your maximum level of confidence is in dollar terms. But first, elaborate on the above. I suspect you are trying to frame my 'indistinguishable from Newtonian gravity' as claiming there is instantaneous action-at-a-distance close in. No, and obviously not if you followed the sense of what I meant. Which was that any still hypothetical GW component of Sun-Earth gravitational 'near-fields' would be imperceptibly feeble wrt quasi-static components having basically Newtonian-to-quasi-Newtonian character. And certainly such notional GW components would have no sharply defined source location, such as your postulated "within the Sun's core region". There would at best be a gradual transition as per #9.
With a fairly strong likelihood imo of no GW's, just quasi-static fields falling off at least as 1/r^2 and higher inverse powers of r.

Anyway, elaborate as to what you did mean. Then we'll talk firm bet and how to decide on it. Go danshawen, go!

 

GW's impossible? Why? BICEP 3 will bite the dust, why are you so sure of that?
It seems that you would be ecstatic if it did.

Ahaa! Now I see.

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My question would be if you are so sure of what you say, and so sure that you have it all solved, why are you here?
Why not go out there and assist in getting your message across.
Oh and a request. Could you tell a poor lowly lay person such as myself, why GW's are impossible? Or at least point me to any article giving reasons why they are impossible.

 

I have never claimed nor gotten down to determine if any and all conceivable modes of GW are impossible. Merely that the quadrupole mode TT-gauge variety ('deforming ellipse'), which within GR is the only permissible mode, is 100% for sure ruled out.

Like I wrote before, not saying here at least for now. It may have $$ value down the track and I'm in no mood to blow that by prior disclosure just to satisfy idle curiosity.

See above. If you can't make the connection, too bad.

As I wrote earlier in another thread, it was a huge personal relief when the premature claims of success for BICEP2 were finally laid to rest. I knew from the start they had to be wrong, but in that early climate of euphoria, there was no chance in persuading GW consortium folks their expensive quests were a likely huge white elephant. In the interim between YES! and NO! results, I just lost interest and focused on other things.

That passage is a late edit by you. Anyway, covered above, though unlikely to your satisfaction.

 

Like paddoboy, I also have an expectation that BICEP3 is a worthwhile experiment. They are highly motivated, and as they are looking for INDIRECT evidence of the action of gravity waves before there was very much of anything out there to absorb them.

As I understand it, I have been offered a sporting wager about the DIRECT detection of gravity waves by instruments based on a LIGO dual, no aperture interferometric device or a LISA dual aperture triple interferometric arrangement, is that right?

I want to make it clear that although a null result of these experiments is also useful, just as it was for Michaelson-Morley or Kennedy-Thorndike, I wouldn't pay for a null result, (as in, no ACTUAL gravity waves detected) agreed? Remember that you are paying ME if they AREN'T detected, understand?

Because of what happened in the case of Joe Weber's Weber bar detectors, I would additionally stipulate that I would not pay for results that are not reproducible or corroborated by more than one gravity wave detector of a similar design. I'm afraid that would, unfortunately, place the terms our wager into one that encumbered both our estates. As such, the terms of the wager would need to be in the form of a time capsule or a trust fund managed by our respective estates.

It's just not much fun wagering if you're not around to enjoy the humbling of your mark, is it? Otherwise, we could just set a timer on the completion of gravity wave detection experiments already in place, say, five or ten years? I wouldn't expect you to pay anything if LISA crashed or suffered a systems failure and you didn't buy insurance on it.

You might also consider that GW could also be absorbed by something like dark matter, which would be another unknown factor in terms of shielding them in the vicinity of galaxies with black holes at their centers. Yours is not a bet I would be comfortable making, even if investors in projects like LIGO and LISA already have.

What are your thoughts?

 

My thoughts are that you seem to have badly misread the content and intent of my earlier posts here. If I read your post #10 right, any betting was on the correctness or not of GW's having 'point source' origins. That the co-orbiting 'point source' Sun-Earth masses are the postulated generators of GW's is not at question. If you believe in a quantized version of gravity where spin-2 'gravitons' constitute GW's, non-localizability follows automatically.
If you believe gravity is probably a non-quantum effective field i.e. essentially classical in nature, one still has that any notional GW's generated are described by a gradual morphing transition occurring over distances orders of magnitude greater than the Sun-Earth characteristic spatial extent.

That and the doubtfulness of there actually being GW's - if really there then necessarily radically different to those allowed by GR - are the points I was making. Methinks we best drop any idea of bets involving estates. I simply claim that in the unlikely case the 'many detections per year' via LIGO materializes, shock surprise - the mode signatures will be anything but GR's quadrupole TT-gauge ones. And yes LIGO and similar are set up such as to be able to discriminate between all iirc 6 possible basic mode types.

 

Very sensible.

 

OK......I can't really comment on all your claim, but I find it hard to believe that the majority of reputable scientists would be looking for something/anything that was impossible to exist.
I prefer the Occam's razor approach: If spacetime can be warped, curved and twisted, why should it also not form ripples from catastrophic collisions.

So you are actively working on showing your claim to be valid? Good, seriously....We have so many would be's if they could be's, that come here, denigrate mainstream science, refuse to reveal their credentials, deride all links invalidating their crank nonsense, and strut on this stage [sciforum stage] hoping to impress people.
Meanwhile of course, science proceeds on without them.

I presume logically that BICEP 3 will be more sensitive then its predecessor.
I also have no agenda one way or the other. If it too fails to determine GWs, then we try other methods. That's what science is all about.....It's very rare for there to be a science experiment that does nothing for science.
Even presumed failures, we learn from.

I really don't accept the validity of how you could know that with such certainty.

Late edit? I've forgotten, but I really don't see that as relevant at all. We all make late edits...well at least I do often.
Again as I have already acknowledged, if you are actually out there, at the grindstone, head down, arse up, then great stuff!
Keep us up to date in how things turn out and any results of any proceedings.

 

You are 'famous' for having an unwavering faith in consensus opinion - in both politics and science. Others prefer to step outside such boxes despite the perils.

Ahh yes, one recalls a thread where e.g. Carlo Rovelli 'disproved' standard EFE's by fiat postulation: GW's for sure exist, carry energy-momentum, hence 'self-gravitate'.
Too bad that leads to a severe paradox. In reality you either have your cake or eat it - not both. My claim re non-existence of TT-mode GR GW's is however not necessarily based on or connected to the above (deliberate ambiguity intended).

Not right now - that 'project' is in cold storage for an undetermined duration. I obtained the proof quite some time back - but profitable utilization of such is another matter. Meanwhile I'm actually working out the spectrum of possible variants on something considered impossible. Violation of the venerable reciprocity theorem. That is to say, non-reciprocity from a device comprised of only ideally reciprocal, linear, and passive components. Result being a radically different and superior replacement for RF/MW/optical isolators/circulators. And, he he, need I say it, no details divulged here.

So very relieved to read that last bit. Of course there is another phenomenon here. Any daring to think outside of Mainstream Opinion are denigrated just on that basis. No names.

OK you failed to make the connection. Let me more-or-less spell it out then. If as I claim GR's brand of GW is non-existent, there is no hope of detecting GW induced CMBR B mode polarizations. No matter how sensitive and discriminating the search for such is. One caveat - some theorists have predicted B-modes owing to non-GW effects - particularly primordial magnetic fields but from memory other sources too. So any possible detection of non-dust generated B modes will need to pass through various physics and statistical model hoops. And it's well known cosmologists have come up with variant inflationary models having arbitrarily small B mode signatures. The usual theorist playground thing.

I should care? You are not in my shoes and vice versa.

Right - a subtle back-handed compliment of sorts I guess. Anyway when and as I devote further time to it, there will feedback as to any further developments.

 

Nice wrap-up of your theoretical position Q-reeus.

I'll of course be disappointed if what you say turns out to be correct and no one ever observes a gravity wave.

But are not the Earth's tides a gravity wave detector? Joe Weber evidently believed they were. His pressure sensors on the Weber bars were intended to do nothing more elegant or exotic than measure a change in shape of a massive object, which is all that a tide does. If this is all a gravity wave detector needs to do, perhaps all we would need is deploy an array of water level sensors. The LHC reportedly is a large enough instrument that the effect of the moon's pull changes its shape. If you considered that to be a rather expensive gravity wave detector, then have they not already been found? How much stronger is the moon's gravitational pull on us compared to orbiting black holes tens of thousands of light years away?

An interferometer trying to measure a much tinier effect (the bending of light by gravity) is trying to do the same thing, but deliberately using something with no mass in order to do this. Yet if you consider that gravitational lensing occurs almost every direction we look, this mode of detection has been proven as well.

Neither of these approaches seem to make much sense, or any more than a slight modification of the Cavendish experiment or even an electronic pendulum for measuring slight variations in gravitational pull.

The boson modeled to be the force carrier in gravity in the Standard Model has not even been identified yet. Or has it?

GR is more successful in explaining gravitational interaction than SM because GR did not dispense with time and replace it with a study of probability and statistics. GR doesn't help us build instruments sensitive enough to detect them because entanglement based clocks have not been invented yet, and the resolution needed to resolve time dilations so small is much finer than instruments based on the propagation of bulk energy or matter make possible. Moreover, relativity itself is incomplete until it includes a consideration of quantum entanglement. Gravity works fine over galactic distances, yet we only know this because we see things moving. It may turn out that gravity wave variations are beyond the range of an energy or matter based clock to resolve, at both ends of the needed scale.

 

Thanks. Especially nice compliment considering how little of any detail I have given away.

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Along with many others - including those who approved funds for such 'high frontier' forays.

No - just responses to very much 'near field' fluctuations in g-field gradients. It's the elusive and vastly weaker 'far fields' aka radiation zone that so much hope is placed on detecting something real.

He famously claimed early success with what is now considered a hopelessly insensitive resonant bar design. Still, it was 'theoretically sound' IF one assumes GR's TT-mode GW's can exist.

Not trying to measure light transverse deflection (bending), but an assumed fluctuation in linear displacement between mirrors. It's a bit subtle (some might say wrong-headed). See e.g.:
https://www.aapt.org/doorway/tgrutalks/Saulson/SaulsonTalk-Teaching gravitational waves.pdf

By 'identified' you mean detected? Certainly not detected and many believe that impossible even in principle. We all know string theorists claim the identification of fundamental string excitation with properties of a spin-2 graviton is taken as a big plus for that theory. Good for them, but how old is string theory now?