Wow! They also assumed the Plane a-priori!

While a detector's directional response is maximal for this case, it is still significant for

most other angles of incidence or polarizations (gravitational waves propagate freely through the Earth)

There was a gamma ray burst at the time that came from the same direction. They were not absolutely certain it was related to the graviational wave burst

One would have thought that in the five months between detection and publication, one of the many, many authors listed on the LIGO collaboration might at least have troubled to check the GRB data. Oh yes, and they might also have glanced at their own plots to see if there was anything present that did not tally with their expectations, features that might tie up with the detected gamma ray burst for example. Failing that, there was a chance these kinds of oversights might be picked up during peer review... or am I just being silly now?

Preprint Coincident Down-chirps in GW150914 Betray the Absence of Eve...

Fact is that the infinite time dilation at the event horizon does not in reality exist, as these observations of the chirps suggest.

Its just a quirky paradox of the maths of GTR 

These along with other paradoxes can be lifted by reformulating the maths

Einstein did not predict the existence of black holes, in fact he denied their existence in a paper published in 1936, Simply because that would imply the existence of singularities, with infinite density and zero time passage at the event horizon.

The force of gravity in General relativity  (GTR) is thought to come form the curvature of space-time.

Unfortunately the maths of GTR implies infinite curvature and zero time passage at the black hole event horizon  and the black hole becomes a singularity- and yet the black hole has a radius.

The Misner Wheeler Thorne interpretation partially resolved this in  that the singularity rests inside the event horizon.

But yet another paradox arises if time stops at the event horizon (frozen star) no matter would fall in hence  black hole could not accumulate matter, and all the in-falling matter would be situated at or near the event horizon, hence the firewall.

The solution is to alter the maths of GR.

Additionally GR falls down in a number of areas, so any new maths should also resolve these problems

Yes GR works in the weak fields of the the solar system, and Intermediate

fields of neutron stars. 

1). It produces infinite density singularities in the very strong fields

such as in black holes.

2).It does not necessarily explain dark matter in galaxy cores where we

know super-massive black holes exist and the galactic dark matter

therein,

3). It does not explain dark mater present in galactic halo's,and galactic

clusters such as the bullet cluster,

4).It does not explain the presence of cosmological dark matter as a whole.

5). It has not yet been fully corroborated by the studies of neutron stars

and in black holes.

6). It does not easily explain the presence of dark energy and cannot be

translated in quantum gravity.

7). It predicts that time stops at the event horizon

Here I enclose a number of publications which explain all of these

phenomena, whilst agreeing with the results of GR where it has been

thoroughly tested.

1).First to obviate the infinite density singularities.

1a)

https://www.researchgate.net/publication/32897680_An_advanced_dynamic_adaptation_of_Newtonian_equations_of_gravity?ev=prf_pub

1b)

https://www.researchgate.net/publication/269689554_The_formulation_of_Dynamic_Newtonian_advanced_gravity_DNAg?ev=prf_pub

2).Secondly we explain the presence of dark matter at the centre of the

galaxy.

2a)

https://www.researchgate.net/publication/228858219_Advances_in_Black_Hole_Gravitational_Physics_and_Cold_Dark_Matter_Modelling._The_Gravity_of_Dark_Matter

3) Thirdly it is possible to explain the presence of dark matter in the

galactic halo.

3a)

https://www.researchgate.net/publication/269689929_Advances_in_Black_Hole_Physics_and_Dark_Matter_Modelling_of_the_Galactic_Halo?ev=prf_pub

4). It is able to explain the presence of cosmological dark matter

https://www.researchgate.net/publication/32897680_An_advanced_dynamic_adaptation_of_Newtonian_equations_of_gravity

5). It is corroborated in neutron stars (including Data from radiation

damping ) and is corroborated by black hole studies.

5a)

https://www.researchgate.net/publication/32888463_An_advanced_modification_of_dynamicgravitation

5b).

https://www.researchgate.net/publication/269667939_Corroboration_of_Dynamic_Black_Hole_Gravitational_Physics_from_Observations_of_Cygnus_X-1

6) it explains dark energy and translates into quantum gravity

https://www.researchgate.net/publication/32899306_String_quintessence_and_the_formulation_of_advanced_quantum_gravity

7). It does not offer infinite time dilation at the event horizon

https://www.researchgate.net/publication/287213872_Finite_Gravitational_Time_Dilation_In_Black_Holes_Using_Dynamic_Newtonian_Advanced_Gravity_DNAg

.

Article An advanced modification of dynamic gravitation

Article An advanced dynamic adaptation of Newtonian equations of gravity

Article String quintessence and the formulation of advanced quantum gravity

Article Advances in Black Hole Gravitational Physics and Cold Dark M...

Article Corroboration of Dynamic Black Hole Gravitational Physics fr...

Article The formulation of Dynamic Newtonian advanced gravity, DNAg

Article Advances in Black Hole Physics and Dark Matter Modelling of ...

Article Finite Gravitational Time Dilation In Black Holes Using Dyna...

Like many, I am sceptical about the result myself.  I myself have written the first paper in the subject in 1992 (BAAS) and then in ApJ (1993) on binary black holes which are known today as extrememass black holes. Subsequently, in 1996 I showed that electromagnetic waves (X-rays/gamma-rays) could also be used to constrain masses, provided there is an accretion disk around either of the two black hole. Please see

S.K. CHAKRABARTI: When Gravitational Waves Collide!

International Journal of Modern Physics D}, 1992, 1, 525.

S.K. CHAKRABARTI: Binary Black Holes in Stationary Orbits

and a test of the AGN Paradigm, Astrophysical Journal, 1993,

411, 610.

D. MOLTENI, G. GERARDI and S.K. CHAKRABARTI,

Simulation of Interactions of An Orbiting Compact Star with an Accretion

Disk by Smoothed Particle Hydrodynamics, Astrophysical J., 1994,

436, 249.

S.K. CHAKRABARTI, Gravitational Waves from Binary Systems

in Presence of Accretion Disks, 1996, Phys. Rev. D. v.53, 2901

P. BASU, S. MONDAL, S.K. CHAKRABARTI, 2008, Gravitational wave emission

from a massive companion black hole in presence of an accretion disk around a super-massive

Kerr black hole, MNRAS, 388, 219

P. BASU, S.K. CHAKRABARTI, 2008, Gravitational wave damping from a self

gravitating vibrating ring of matter around a black hole, New Astronomy, 13, 451

(a) If Gamma Ray were even looked for, then there is a fallacy. The same matter which would have emitted gamma rays, would also have altered the angular momentum loss profile of the orbiting black holes (as I shown twenty years back). So  I would more happy if they DO NOT see gamma rays. I am writing an article on this.

(b) The masses 36 and 29 M are unbelievable numbers. No known astrophysical process is going to give stellar mass black holes of those masses. In our own galaxy we do not see black holes more than 5-15 solar mass. So I WOULD BE HAPPY, that if the detection is not a fluke or hoax, or not tuned to attract specific persons/funds (which often is done), the presented masses do not make sense at all.

Sandip,

You're quite right - it's extremely odd that the claimed masses are far too small to be supermassive black holes and yet implausibly large to have been created through stellar collapse. The event was also extremely remote. Would we not have expected more numerous examples of objects of smaller mass coalescing nearer to us during recent months, with comparable if not better signal strength?

Setting aside the possibility that other detections might remain selectively unpublished, I question the inferred masses as they were estimated based on the unwarranted assumption that Kerr black holes are the realistic outcome of gravitational collapse. As many are aware, the ingress of matter across an event horizon is mathematically prohibited in a universe of finite age, and the characteristics of quasars cast observational doubts on the existence of  event horizons. Furthermore, Einstein himself rejected the notion of black holes back in 1939. Alas, I see this as further confirmation that science is not being taken sufficiently seriously on this planet. I elaborate on these points in the attached article.

Preprint Dispelling Black Hole Pathologies Through Theory and Observation

Robin,

All said and done, I am really not questioning presence of black holes as we see their signatures on a daily basis through all the satellite observations. In fact we see matter moving towards the horizon on an hourly basis. I myself have written a hundred ApJ/MNRAS on that. So I am not questioning BHs. They may as well be 'fuzzy-ball' type where we really need not want to know what is INSIDE the horizon. All all practical purposes the it may be a ball-like object that todays pundits are maintaining (see papers by Samir D. Mathur etc.). I also believe that the space time perturbation would propagate at a velocity of light (it is not like an electromagnetic wave embedded on the space time).

Having said these, the Gamma Rays/X-rays i was hoping are coming from the matter that falls on them. Now if both are black holes, each could be starving after eating up matter perhaps coming from the SN collapse or tidal deformation. In that case templates made from point like source would good enough. THAT WOULD NOT be the case if strong X-rays/gamma-rays were seen from the matter. The matter would be changing the template, messing up the mass estimation and possibly also the distance.

I am also surprised to see beautiful symmetric patterns in both the detectors and a random source in a random direction could not have possibly done that due to its (mis)alignment with the arms of the detectors.

In the past, false hopes have been used (e.g. GRB was detected by a satellite funded by Senate inadvertently, as they thought they are funding a satellite to monitor Soviet H-bombs). Even the 'Black hole of Calcutta' incident was rigged to get more funds from the British parliament which was eventually used to finish of the last king of free India in 1756. Since the source such this just cropped up within 3 days of turning on the machine, I would be expecting then to rain down cats and dogs. Have they?

My apprehension about the masses remain.

Sandip, you seem to be very comfortable with the possibility, nay likelihood, that black hole research is a pathological science, which makes me apprehensive.

Robin,

No true. I believe in black hole research, and I make a living on it. As I said, the satellite observations on black hole candidates (X-rays/gamma-rays) are REAL and DO indicate existence of black holes. The radiation emitted is perfectly understandable from conservation laws.

My cynical comments are mostly on this specific example of GW detection. I would like to wait for more detection. One observation is not enough for me.  I also doubt the identification of the component masses involved. I am neither against black hole science, nor that GWs. I think many angles to the recent events must be looked into.

I would ask a simpler query: if the raw signals are so obviously good looking and even a dumb would call it a detection, why would a Nobel winning paper be announced after five months, and that too just before Indian Budget session where 13 billion rupees just committed based on that result?

@ Robin/sandip

Well we live in a very large Universe and rare events do happen

This event resulted in one very large star producing two black holes whilst collapsing. Why two black holes - because it was spinning very rapidly.

Then the two black holes merged in a matter of seconds. producing a very short burst of gravitational waves.

What's more the black hole merger produced an additional "chirp" of matter ejecta, which means the black hole event horizon is not inviolable - as predicted by the papers below

1a)

https://www.researchgate.net/publication/32897680_An_advanced_dynamic_adaptation_of_Newtonian_equations_of_gravity?ev=prf_pub

1b)

https://www.researchgate.net/publication/269689554_The_formulation_of_Dynamic_Newtonian_advanced_gravity_DNAg?ev=prf_pub

2).Secondly we explain the presence of dark matter at the centre of the

galaxy.

2a)

https://www.researchgate.net/publication/228858219_Advances_in_Black_Hole_Gravitational_Physics_and_Cold_Dark_Matter_Modelling._The_Gravity_of_Dark_Matter

3) Thirdly it is possible to explain the presence of dark matter in the

galactic halo.

3a)

https://www.researchgate.net/publication/269689929_Advances_in_Black_Hole_Physics_and_Dark_Matter_Modelling_of_the_Galactic_Halo?ev=prf_pub

4). It is able to explain the presence of cosmological dark matter

https://www.researchgate.net/publication/32897680_An_advanced_dynamic_adaptation_of_Newtonian_equations_of_gravity

5). It is corroborated in neutron stars (including Data from radiation

damping ) and is corroborated by black hole studies.

5a)

https://www.researchgate.net/publication/32888463_An_advanced_modification_of_dynamicgravitation

5b).

https://www.researchgate.net/publication/269667939_Corroboration_of_Dynamic_Black_Hole_Gravitational_Physics_from_Observations_of_Cygnus_X-1

6) it explains dark energy and translates into quantum gravity

https://www.researchgate.net/publication/32899306_String_quintessence_and_the_formulation_of_advanced_quantum_gravity

7). It does not offer infinite time dilation at the event horizon

https://www.researchgate.net/publication/287213872_Finite_Gravitational_Time_Dilation_In_Black_Holes_Using_Dynamic_Newtonian_Advanced_Gravity_DNAg

.

Article An advanced dynamic adaptation of Newtonian equations of gravity

Article The formulation of Dynamic Newtonian advanced gravity, DNAg

Article Advances in Black Hole Gravitational Physics and Cold Dark M...

Article Advances in Black Hole Physics and Dark Matter Modelling of ...

Article An advanced modification of dynamic gravitation

Article Corroboration of Dynamic Black Hole Gravitational Physics fr...

Article String quintessence and the formulation of advanced quantum gravity

Article Finite Gravitational Time Dilation In Black Holes Using Dyna...

Sandip,

Before Wheeler came up with the term black hole in the late 60s people understood the outcome of gravitational collapse to be a frozen star lacking an event horizon. Such objects are often, though not always, observationally indistingishable as far as astronomers are concerned/ By now black holes have been foisted upon mainstream science, exploiting a gullible public and gullible new generations of scientists. That Einstein, Eddington and Dirac regarded the Schwarzschild metric as physically unattainable has been swept under the carpet - but they were quite right to dismiss black holes on account of infinite time dilation. The more you compress an object, the slower time advances for its constituent matter. If you try to create a black hole in this way, time will halt completely to thwart you, saving the universe from a host of absurd outcomes and paradoxes.

I could list a dozen severe problems that the existence of black holes would create for physics and cosmology but your strongest counter-argument would be that we possess metrics describing stationary black holes, objects that would necessarily have to pre-date the big bang. Appeals to a belief in them by celebrity scientists or the sheer number of papers published on the topic in recent decades are really just a symptom, but they attest to the gigantic scale of the disease.

You may be right that the main reason for the 5 month publishing delay could have been political machinations involving India and China but I think this overlooks the more worrying underlying issue. Alternative models were not considered in that paper (despite curious features in the signals) because black hole research has been driven by the politics of the academic establishment, much more so than by genuine science, for the last 50 years. But I think Einstein will once again triumph, even if his warning concerning black holes is currently being marginalised.

Hi Robin,

 I llke your work - but have you considered that Einstein was right mathematically until we begin to closely approach the event horizon - which is not inviolable

Hi Andrew,

Portions of the exterior Schwarzschild solution accurately describe gravity around a spherically symmetric object. Einstein did not regard the rest of the solution as physically relevant. He appreciated that if nothing can penetrate the event horizon in finite time then it must be wrong to assume that objects with an event horizon exist. For this reason, and many others, my view is that there is never an event horizon to approach, closely or otherwise.

Hi Robin,

I like this discussion about physical sense (or nonsense) of BH within GRT. Actually the central subject here is the nature of the gravitational interaction itself. In modern theoretical physics there are only two alternatives for this: Einstein’s geometrical  and Feynman’s field approaches for description of gravitational interaction.  Though classical relativistic effects  have the same values in both approaches, there are dramatically different effects predicted by  GRT and  FGT for relativistic astrophysics (including BH existence), see arXiv: 0809.2323 and arXiv:0809.2328. 

Actually what we observe in astrophysics is the Relativistic Compact Objects and not BHs. Though we expect in this year to see the first VLBI observations at 0.6 mm using EHT which will demonstrate the image of SgrA*  RCO at scale of its gravitational radius. It will be really crucial experiment on the physics of the gravitational interaction.

Hi Yuri, it will certainly be interesting to discover whether the EHT can tell us more about these RCOs. You say that Feynman's field approach is immune to singularities. For this theory, would there be some limit to the density of matter?

Hi Robin,

There is no theoretical limit on the density of matter in the Feynman’s field gravity (FG) approach, but there is definite limit on the size of any physical body which must be larger than  R > R_g  = GM/c^2. This limit has very clear physical meaning, like the classical radius of the electron, i.e. when energy of the gravitational field must be less than the rest mass of the body measured at large distance  E_g < E = M c^2. This is why there are no black holes in the FG, see

http://arxiv.org/abs/0809.2323

http://arxiv.org/abs/0809.2328

By the way in FG there are two types of gravitational waves – tensor waves (spin 2) and scalar waves (spin 0). Intriguingly, only scalar waves can interact with LIGO mirrors, so GW150914 (if real) can be detection (localization of the energy of the gravitational field) of a scalar GW:

http://arxiv.org/abs/gr-qc/9911081

Dear Thierry,

Black Holes are not  physical objects (both static and rotating) because in General Relativity there is no the energy density (energy momentum tensor) of the gravitational field (see Misner, Thorn, Wheeler, Gravitation, 1973, paragraph 20.4, p.467; and Landau & Lifshitz, Field theory, 1971, sec 101, p.304). This is why the concept of BH does not control the energy of gravitational field both inside and outside BH.

This is why it was long time discussion about localization of the GW, because it demands the localization of the energy of the gravitational field.

But MTW(1973) p.467 wrote that energy of the gravitational field "is not localizable. The equivalence principle forbids".

There are some good discussion about Black Holes on RG by some experts.

https://www.researchgate.net/post/What_do_you_think_about_the_existence_of_the_BLACK_HOLES?_tpcectx=profile_questions

Thierry, I don't accept your argument as it completely overlooks gravitational time dilation, which can become infinitely strong.

Yurij, I am open to theories in which event horizons are prohibited and matter can exist at extremely high densities, providing of course they do not conflict with empirical data. However, my suspicion is that no departure from general relativity is required until the Planck scale.

Many serious difficulties exist with the concept of black holes, some theoretical and some observational.

Theoretical:

The event horizon of a stationary black hole is impenetrable if one insists that external proper times must remain finite. Einstein was aware of this and understood that this alone guarantees that the formation and growth of black holes is impossible. Moving to Kruskal coordinates has no effect on the actual physics, a straightforward consequence of general covariance. That is why Dirac was able to side with Einstein after the publication of the Kruskal metric.

Paradoxes would arise. Information and electrical charge would vanish from the universe (perhaps to spontaneously reappear, as if by magic, at the endpoint of Hawking evaporation). The electrical field of a charged particle cannot propagate faster than light in order to escape the event horizon of a black hole. Similarly, gravitational waves are limited to the speed of light, and are unable to transport energy from within a black hole out into space. Travel backwards in time, a generic feature of rotating black hole spacetimes, would destroy causality - the bedrock of genuine physics.

The entropy of a black hole would be enormous. There is no plausible mechanism for this entropy increase as particles/astronauts passively drift through the event horizon, supposedly noticing nothing remarkable as they do so.

It is implausible that matter can exist at infinite density. The Oppenheimer-Snyder paper stated that singularities cannot form in finite time and that, from the perspective of the external universe, the event horizon is never present. That paper, ignored at first and somewhat notorious by now, was an ambitious analysis which followed closely on the heels of the TOV limit on neutron star mass. Had it not been for Oppenheimer's distraction by the Manhattan project, I suspect he might well have tidied up the loose ends left behind by that work, and ironed out its inconsistencies.

Black holes conflict in several ways with a new cosmological model that yields the first resolution of the Fermi paradox which abides by the scientific method. Black holes would consume neutrinos, depriving aquatic life of a vital energy source. They would prevent the future decay of dark energy to neutrinos via the Unruh effect. They would dominate the entropy increasing processes of the universe, ruining what would otherwise be an impressive entropy management strategy capable of sustaining aquatic life very efficiently for 1025 years.

Observational:

The finite lifetimes of quasars, the beamed emission of relativistic jets of charged particles and the extreme energetics are consistent with a rotating, electrically charged central engine generating its own poloidal magnetic field - ruling out popular Kerr black hole models. Low redshift galaxy clusters are presently very rich in gas yet their galactic nuclei are dormant. A toroidal dark hole model fits the observational data and establishes, via topological censorship, that these "black hole candidates" cannot possess event horizons. Quasar extinction corresponds to topological collapse of the central engine, swiftly followed by its charge neutralisation.

The spectrum of the GW140915 event includes features suggesting significant mass ejection occurred as the "black holes" coalesced. This is inconsistent with the black hole interpretation.

There are very good reasons why black holes were not taken seriously for a long time. They were foisted upon science during the 60s due to the widespread bewilderment concerning the realisation that quasars are extremely remote and hence extraordinarily energetic objects, the discovery of the Kerr metric and rampant speculation/confusion in the wake of Einstein's departure. I think that what followed since will in time come to be regarded as an ignominious episode in the history of science. To some it was always apparent that black holes amounted to nothing more than pseudosicence, but by now that pseudoscience has been allowed to harden into pathological science, and that is detracting from important research.

Thierry, so in order to simplify things and eliminate the pesky time dilation corrections in the GPS calculations, we need only ensure that everybody switches off their clocks?  The same will presumably be true of black holes: so long as nobody switches their clocks back on, the fantasy that they exist will be able to continue indefinitely! Oh, but wait, how can we be sure that civilisations elsewhere will not invent clocks and spoil this fun game? How can we make the universe safe for physicists who like to continue betting on issues that have already been satisfactorily settled?

Dear Robin, you wrote:

"I am open to theories in which event horizons are prohibited and matter can exist at extremely high densities, providing of course they do not conflict with empirical data. However, my suspicion is that no departure from general relativity is required until the Planck scale."

The Feynman's Field Gravity Theory is not a new theory of gravitation, it is a part of the modern relativistic quantum field theory of all fundamental physical interactions (ED, QED, QCD). Such non-metric theory of gravitational interaction is called Feynman’s Field Gravity Approach (http://www.amazon.com/Feynman-Lectures-Gravitation-Frontiers-Physics/dp/0813340381). Feynman emphasized that: “The geometric interpretation is not really necessary or essential to physics”.

Though the FGT was not developed enough in modern  literature, e.g. see review in 

http://arxiv.org/abs/0809.2323   and   http://arxiv.org/abs/0809.2328 .

In FGT all really tested relativistic gravity effects has the same values, though very different interpretations. Also there are different testable predictions even in the weak field regime. In FGT there is no problem with the energy of the gravitational field (wich is a big problem in GRT) and no BH because there is limiting size = gravitational radius R=GM/c^2.

Dear Yurij,

So Feynman's Field Theory is distinct from GR, not merely an alternative interpretation, yet consistent with all experimental results? Even gravitational lensing?

Can it also accommodate the accelerating cosmic expansion? If so, what becomes of energy conservation in this case?

I suppose the idea that everything moves in as straight a line as possible is abandoned, but gaining energy conservation seems like handsome motivation.

How close are we to being able to discriminate between the theories experimentally?

Dear Robin,

all answers to your questions exist in the references which I noted in preceding notes. We cannot go further in our discussion without reading this papers.

In a nutshell FGT is consistent with all really tested relativistic gravity experiments, including gravitational lensing and also there are new testable predictions which can distinguish between FGT and GRT.  The FGT is not a metric theory, but is a field theory of the gravitational interaction, similar all other theories of fundamental physical interactions.

Modern cosmological data and comparison of GRT and FGT cosmological models is presented in the book http://link.springer.com/book/10.1007%2F978-94-007-2379-5 .

 In FGT there is no expanding space and cosmological redshift can be due to global mass distribution (see also  http://arxiv.org/abs/0810.0162 ).

Dear Yurij,

I have read your interesting articles. It is intriguing that such a radically different proposal is still viable.  I note that high vacuum accelerations are still attainable for ravitationally collapsed objects, which I like. However, unlike most people, I can see definite advantages to the non-conservation of energy at the cosmological level. That is why I was asking about whether dark energy can be accommodated in FGT. I am particularly interested in the possibility that vacuum/gravitational energy might tunnel out over the course of ~ 1011 years via the Unruh effect in the vicinity of RCOs, ultimately brining an end to the accelerating cosmological expansion. Do you see a way for this to work in FGT?

The vacuum contribution in FGT will be studied in future, it takes time for developing the quantum FGT.  

Understood, but could the accelerating expansion be attributed to a negative pressure fluid in this theory? Would an additional field be needed perhaps? Is there some obvious analogue of a cosmological constant?

In FGT the source of gravity is the EMT(energy momentum tensor) of any kinds of substances including physical vacuum. However the vacuum is a special kind of quantum substance, hence it requires quantum gravity consideration.

The most important feature of the FGT is that the symmetric second rank tensor potential (describing gravitational field) actually contains two types of fields - tensor (spin 2) and scalar (spin 0, which corresponds to the trace of the EMT of the sources). So FGT is the scalar-tensor theory, but the scalar is intrinsic (trace of the symmetric potential, instead of extrinsic scalar in the Brans-Dicke's like theories).

This scalar part is similar to the cosmological constant. However the cosmological model in FGT is essentially different from SCM in GRT(which has many theoretical and observational problems - see http://arxiv.org/abs/1501.01919 ). There is no expanding space in FGT, which is constructed in Minkowski space. The Field Gravity Fractal cosmological model is considered in http://arxiv.org/abs/0810.0162 . 

Dear Yurij, I have reasons to suspect that the accelerating expansion is driven by a vacuum energy that is capable of decaying via Unruh radiation from collapsed objects (black hole candidates) over the course of the next 60 billion years or so. The vacuum energy density is far too small to be plausibly attributed to a cosmological constant. I can see that there might be more hope of quantising FGT than GR. So I wonder whether there is any possibility of a connection between vacuum energy in FGT and its discharge via the Unruh effect in environments where the acceleration due to gravity becomes immense (though short of the Planck acceleration scale). Might there be some clues here as to how to proceed with quantum gravity?