We should say goodbye neither to Black Holes nor to gravitational waves. When a star die and collapses under the pressure of Gravitation Force the whole mass of the star converts into a highly condensed ball of Gravitation Force.

Gravitational waves are the fact as it generally can be in the science. Hence, let's listen to them!

The "echos" are also compatible with what is predicted for 2,2 quasinormal mode oscillations during ringdown. See for example this paper but there are many others:

Article Black Hole Quasinormal Modes in the Era of LIGO

Distinguishing between different models will take a lot of detailed analysis so I think the paper cited in the question is just saying that one particular hypothesis about the nature of the event horizon is not ruled out, there remain several possibilities.

Gravitational waves allow viewing into the interior of "black holes" and reveal a structure. This is not a surprise, it is a great success of science.

This discovery leads to the requirement, that a zoo of exotic matter exists, with ultra hard and ultra heavy elementary particles, which can't be squeezed by immense pressure and which are stable under exotic conditions.

Because ECOs of any size show stability, the existence of an endless series of higher order particles with increasing mass is probable.

Maybe there is only event horizon at Planck scale and at Planck mass never achievable...

...as elementary mass.

May be an event horizon of any size exists, but is never achievable in a dynamic shrinking process because of dilatation effects.

The Earth has no event horizon, does that make it exotic? The originator of our best theory of gravitation realised long ago that event horizons cannot form during gravitational collapse, and pointed out the mathematical reason for that in a paper published in 1939, thus resolving the black hole information paradox before anyone silly enough to entertain it had been born:

Preprint Dispelling Black Hole Pathologies Through Theory and Observation

One does not need fictitious black holes to generate gravitational waves, and black holes are incapable of rapidly ejecting matter:

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

The experiment on direct imaging of nearby Black Hole Candidate SgrA* was done in April 2017, however up to now there is no published results:

http://eventhorizontelescope.org/

The better meaning for ECO was proposed: "eternally collapsing object" - no exotic reference. I don't remember who has created that expression...

The Earth is also an eternally collapsing object. ;)

Article Low significance of evidence for black hole echoes in gravit...

An answer here ..

I think they used templates from simulations with event horizon - i.e. only the regular signal accepted. Imho the open theory should be considered.

It's embarrassing enough that there's any reluctance to thoroughly consider the various possibilities but we've had 50 years of this charade (namely the belief in black holes by a supercilious clique that has fostered yet another academic dogma). Luminaries such as Einstein, Eddington, Dirac and Landau recognised long ago that infinite time dilation prevents the formation of event horizons, a conclusion backed up by the mathematics yet completely ignored by today's bungling "experts". It's high time that Hawking and others came clean, and admitted their colossal mistake.

Hi Robin!

Hawking's NOT one of the "bad guys" here - he's fiercely independent-minded, and in the early 1970s was initially the only person radical enough to stand up and say that according to QM black holes radiated, and that if GR said otherwise, then "so what".

A few years ago Hawking also suggested that we might be able to fix the current black hole information paradox by changing GR's horizons from "event" horizons to weaker "effective" horizons. A lot of people knew this, but it was still a radical thing to suggest, because it implies that there may be something in the current structure of GR that requires changing.

AFAIK, Einstein's objection to horizons was that an event horizon suggested a one-way causal relationship between two regions, which according to Einstein, was philosophically bad – he argued that since this shouldn't happen, but GR1916 seemed to make it inevitable, that his own general theory probably shouldn't be trusted to make correct predictions for such extreme situations.

Dear All,

The assumption that gravity is a pulling force created either by some kind of field or by some kind of geometry, as for example is given in the GTR, and the observation that light seems to bend around mass, has the consequence that extrapolation of the rules will lead to a situation where there is inside a given volume so much mass that we have to call it a black hole.

This of cause does not mean that automatically nature has to follow this theoretical case. We know for sure that we have observations of objects that seem to have extreme large mass and are located in the centres of galaxies. (I try to state it such that we don't need to discuss this formulation..)

The results from our analysis of the observations is always based on the initial assumptions. In my article, as I have uploaded under my project in the first comment, I have given a derivation that it is possible that the expansion of space can't be depending on any energy density inside it. Under that condition we can accept the huge energy density as QM predicts it that is 10120 larger than the total sum from cosmology theories. With a so large zero point energy we can have the situation that gravity is a result of the density variation of this energy. The more empty an area is the more zero point energy can be there. The larger an empty volume is the larger the lowest frequencies can be. With this view gravity would be the push of the 'empty' larger volumes, that have a higher energy density, to the smaller volumes, that have a lower energy density. This can follow the theories like GTR for a large range. But in the end the singularities will be different.

I show with this that we first need to analyse if our assumption, that gravity is a 'pull' is correct and that it is not a 'push'. A push has a maximum.

Regards,

Paul Gradenwitz

Hi Eric,

Einstein published a paper in 1939 explaining why black holes cannot realistically form, on the same day that Oppenheimer & Snyder published theirs. O&S drew an invalid conclusion in their discussion, despite the fact that their calculations correclty indicated that gravitational collapse only asymptotically produces a result resembling a black hole: an event horizon never actually forms. It was the day that World War II broke out. Many people are unaware of this background precisely because many people who are aware of it never mention it in public, even though some of them have had ample opportunity to do so due to their celebrity status.

There is no information paradox, current or otherwise, to be fixed within GR itself. If you remember, what Hawking actually said a few years ago was that perhaps event horizons don't exist but apparent horizons do - a very odd comment because apparent horizons can only arise within event horizons. Was he perhaps dipping one toe in the water to see what response a full confession might draw?

In the 1960s, Penrose and Hawking published their singularity theorems in which they assumed that time dilation effects can be ignored and worldlines can be extended arbitrarily without restriction. You never hear mention of these assumptions when they discuss their work or when they continue working on solutions to problems that those reckless assumptions gave rise to. Take out the work on fictitious black holes and what are you left with? Einstein was a genius who made many solid, scientifically verifiable discoveries - why ignore his conclusions and why will academia not even allow anyone to mention them any more? Is it because science is no longer considered important?

Hi Robin,

Under current GR, apparent horizons arguably should only coincide with event horizons, but ... the 1916 theory's screwed up. It's geometrically incoherent.

The illustrating argument I came up with in 2016 was this:

The "horizon" part of GR1916 doesn't work.

Further,

So Einstein's 1916 theory, and any other attempt to build a curved-spacetime model using SR and Minkowski spacetime as a physical foundation and wholly-included subset of the physics, doesn't work.

The concept is fundamentally flawed. If one wants to build a legitimate geometrical theory of gravity, it has to be built around and compatible with curvature-based principles right from the very beginning. One cannot just splice in existing legacy theories that have incompatible starting assumptions, and trust everything to work out.

Hi Eric,

When Einstein pointed out that black holes are unphysical he wasn't criticising general relativity in any way, merely pointing out that there are solutions of the field equations which have nothing to do with reality. Problems arise when it is assumed that those solutions (obtained by imposing stationarity) can be arrived at by evolutionary physical processes from realistic initial conditions. What prohibits the formation of event horizons is the fact that the universe has a finite age. I side with Einstein (and Landau, Dirac, Eddington and others) on this. We may be living in dark times but that does not make black holes any more likely. The information paradox is a well known problem that arises when invalid assumptions are held to be true. You may have found more. I can point to a few myself, along with two lines of astronomical evidence that the objects commonly referred to as black holes do not possess event horizons:

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

Preprint Dispelling Black Hole Pathologies Through Theory and Observation

"What prohibits the formation of event horizons is the fact that the universe has a finite age" ??

better:

What prohibits the formation of event horizons is the fact that the collapsing object has a finite age.

The proper time along any worldline is guaranteed to be no greater than the age of the universe. A black hole is a hypothetical object which is not only older than the universe, but infinitely older. Ah, but if it was fully formed an infinite time ago, when did its formation actually occur? Even if such technicalities are set aside, how can black holes communicate the fact that they have mass or charge to a universe which they cannot influence without those tachyons that never turn up in particle colliders? The ongoing pretence that black holes exist, despite clear observational and thoeretical evidence to the contrary, is not merely an embarrassment to science but to human civilisation. It is not surprising that this species is prepared to ignore the views of Einstein concerning gravitational collapse when it is perfectly content to ignore so many simple lessons from history.

Dear Robin,

assumptions about relations between the age of "black holes" or whatever we consider to be "black holes" and the age of the universe are highly speculative. Aren't they?

Isn't gravitation a quite intense influence of "black holes" on the universe?

It seems that we don't know what "black holes" really are.

Hi Wolfgang,

I'm prepared to trust the results of properly performed calculations drawn from a theory of gravity which has passed every experimental test. A very straightforward calculation proving that no particle of any description can traverse a Schwarzschild event horizon could be taught to schoolchildren with some scientific aptitude in a half hour lesson. As for any suggestion that objects within the universe might be older than the universe itself, you should understand that this is not my stance at all. I was merely pointing out the absurdity of the belief in black holes given what is known for sure about their mathematical properties. Einstein understood that a black hole is a fictional object but I agree that there are many people today who don't know that, many of them happy to keep on channeling research funding in unproductive directions. If you're asking what is the end result of gravitational collapse my answer is an eternally collapsing object, formerly known as a "frozen star". I prefer the term "dark hole", however, since I think that some important physics still goes on in regions of high gravitational acceleration despite the time dilation, allowing dark energy to gradually discharge in the form of neutrinos:

Preprint A Non-anthropic Solution to the Cosmological Constant Problem

Hi Robin,

Schwarzschilds original work does not comprise something like an event horizon. Schwarzschild considered a point mass and the only singularity in his solution was at radius=zero, the exact position of the point mass.

All calculations, which directly concern the event horizon or the vicinity of the event horizon are speculative. Therefore properly performed calculations drawn from "the theory of gravitation", which consider effects of the event horizon do not exist.

Hi Wolfgang,

I don't consider the event horizon of a black hole to be a singularity and I haven't said that I do. In fact, I would not even describe black holes as a speculative idea. The mathematics clearly shows that their formation is physically impossible. Of course, that does not prohibit the formation of objects without event horizons during gravitational collapse. There's no doubt that very massive, almost invisible objects lurk at the centre of every galaxy.

Hi Robin,

without the event horizon/the singularity, we should ask which property of matter prevents the complete collapse. Is it possible that an infinite series of higher order "increasingly hard" kind of elementary particles exist?

This would mean that with a much larger hadron collider we only would find heavier and smaller particles with a shorter lifetime confined by super quarks.

Hi Wolfgang,

Gravitational time dilation is caused by the presence of matter and energy. As the metrics of the hypothetical black holes show, the time dilation becomes infinite for any particle of any mass travelling towards a black hole before the particle can be absorbed, thus prohibiting its capture (not to mention the formation of the BH itself).

There's a maximum limit to the mass of a neutron star above which degeneracy pressure can no longer withstand gravity. As implosion proceeds, density increases but the degeneracy pressure only becomes weaker compared to gravity. However, the collapse does eventually halt owing to the relativistic effect of gravitational time dilation, doing so in such a way as to permanently prevent the formation of an event horizon. The resulting object was once referred to as a "frozen star" before general relativity was overrun by mathematicians with a poor grasp of physics and no regard for the scientific method.

A careful explanation of this was provided by Lev Landau in the first edition of "The Classical Theory of Fields". Alas, he passed away soon after the first edition, and his correct dismissal of black holes was erased from subsequent editions for the sake of moronic academic dogma and the sale of popular science books by those hoping to cash in on their celebrity.

Although you could regard the gravitationally collapsed matter as becoming extremely stiff, in the local frame nothing has really changed. It is just that the time dilation has slowed down all physical processes as observed by the rest of the universe.

http://nautil.us/blog/are-black-holes-actually-dark-energy-stars

At least a different point of view...