[Kryptid]

The calculations are all done by computer. But how accurate are these computer calculations, when does the computer decide that a signal isolated from the trillions and trillions of different signals, is the one signal denoting gravity? Surely the very noise generated inside the circuits of LIGo should swamp any credible signal? A very dodgy situation.

It isn't dodgy at all. The gravitational waves produced by a black hole merger event is predicted by general relativity to have a very distinct pattern to it. I have a book written long before the first gravitational wave detection that details this pattern. The fact that LIGO has two arms at right angles to each other is critical in detecting it because gravitational waves produce a contraction of space along one axis while producing a stretching along the other axis. As the wave passes, this stretching and contraction reverses and then cycles again and again.

As two black holes approach each other in orbit, the strength of this signal slowly increases until the merger event, after which there is a "ring down" period where the newly-formed, merged black hole releases additional gravitational radiation before it settles. The signal then disappears. This known pattern combined with the fact that LIGO and VIRGO are in widely-separated parts of the world can be used to rule out false positives due to local noise.

[McQueen (OP)]

It isn't dodgy at all. The gravitational waves produced by a black hole merger event is predicted by general relativity to have a very distinct pattern to it. I have a book written long before the first gravitational wave detection that details this pattern. The fact that LIGO has two arms at right angles to each other is critical in detecting it because gravitational waves produce a contraction of space along one axis while producing a stretching along the other axis. As the wave passes, this stretching and contraction reverses and then cycles again and again.

                          While what I have to say may not go down well with certain people, objectivity is one of the most desirable traits in the evaluation of any scientific method. Take quantum computers. For one thing the present generation of quantum computers cannot truly be called quantum computers. Quantum computers are computers based on quantum entanglement of sub-atomic particles. The present generation of quantum computers detect changes in the current of Josephson-Junctions of super conductors and use these signals to serve as quantum qubits, this is more or less a digital process and can by no means be equated with quantum entanglement. Therefore, what may eventually emerge from such a development are better computers but they could not by any criteria be termed to be quantum computers. Google, one of the leading proponents in the field, are offering rewards of upwards of 5 million dollars for anyone who can come up with a practical use for quantum computers. Considering, that Google is one of the most innovative companies in the world, and the fact that research has been going on for at least a decade with unlimited funding, this does not look like a good sign. One useful function that quantum computers should be able to perform, is that of quantum encryption. Surely quantum encryption is such a massive field that there would be no need to advertise for further uses of quantum computers? The fact that no encryption encoding is forthcoming from quantum computers is in itself an indication of the present day wildly speculative nature of science.  Huge sums are spent on proving things that cannot be proven.

                   I would say that in spite of the many reasons that you put forward to justify LIGO that it is a far cry from a certainty. To detect differences of 10,000th the width of a proton in the presence of so much signal noise, is a bit of a stretch.  Mere wishful thinking rather than sound (pardon the pun) science.

[alancalverd]

Except it doesn't explain the interaction of light with materials. Photography, photoelectricity.....all require a particle model,

Not necessarily. A modified wave model can do the same job.

Please explain photographic reciprocity failure and radiographic quantum mottle using a modified wave model.

and at very low intensities you can even count the photons!

You don't really count the photons. Only some activations of sensory equipment, which can also be activated by other stimulants, such as temperature and cosmic rays.

Cosmic rays behave very much like particles in a cloud chamber or a film block, and indeed can be counted individually as particle interactions in electronic detectors. Which is why we call the massless, electrically neutral ones "photons". The effect of temperature on a photocathode will not change when you put a piece of cardboard between your photon source and the detector.

One common use of photon counting is in x-ray crystallography where we count individual diffracted photons at different points in space them use a wave model to determine the structure of the material that scattered them.

[Kryptid]

To detect differences of 10,000th the width of a proton in the presence of so much signal noise, is a bit of a stretch.

If it had been determined that the noise was an insurmountable problem, they wouldn't have spent so much money building the thing. Besides, random noise isn't going to generate the telltale gravitational wave signature of two inspiraling and then merging neutron stars in three different locations on the planet and also at the same time that the merger was detected in the electromagnetic spectrum: https://en.wikipedia.org/wiki/GW170817

[Eternal Student]

Hi.

Some minor questions from @Zer0  seem to have been missed.

Please do Allow a few randomly absurd thoughts...

   I'll assume you want short replies.

Can " Space " bend over itself?

    I'm not sure what you were asking.    Here are 2 possibilities:
1.     Can space act to bend space?   Space isn't as empty as you might think,  there is always vaccum energy in every cubic metre of space.    All energy contributes to gravitation (the curvature of spacetime).   So space will bend spacetime and some of that curvature will be purely in the spatial part of spacetime,   so we could reasonably say "yes, space can bend space".  Indeed "vaccum energy" is an important component in modern cosmological models.
2.      Can space roll up like a carpet or fold over itself somehow?    It's best that you don't think of space as some 2-dimensional rubber sheet that curves in 3-dimensional space,   so that whatever image you have of space bending over itself, it probably isn't like that.   Black Holes are an example of a region where curvature becomes extremely degenerate as you approach the singularity.   You might declare this as a region where space has folded over on itself but you'd need to be working in higher dimensional flat space to "see" that.
     String theory sometimes considers the existence of additional dimensions that are described as being tightly rolled up and generally go un-noticed.  However, this isn't really a consequence of space doing anything to roll these other dimensions up,  they just are tightly curled up for some reason.

Can ' Relativistic mass ' not produce a similar, but not the same, effect such as Gravity?

     Yes and it essentially does produce a gravitational effect broadly equivalent to having more mass.
    1.   We don't really use "relativistic mass", it's an old term and discouraged - but we don't need to, we capture the important information about the movement in other ways.
    2.   In GR various things are sources of gravitation.   Sources of gravitation are all the forms of stress-energy that exist and all this information appears in the stress-energy tensor.   So, mass is certainly a source of gravitation but so is energy, momentum and pressure.    So a moving particle contributes a lot more to gravitation (the curvature of spacetime) then a stationary particle.    A moving particle has mass, kinetic energy and momentum.   It can also elevate the pressure that exists in a region of space  (e.g. a gas has pressure due to the movement of particles in it).    Overall, the curvature of spacetime will be more significant when a moving particle is in that region than when a stationary particle is in that region.   
     If you have Newton's ideas of gravity in the back of your mind then it is broadly equivalent to a moving particle acting as a source of gravity according to its relativistic mass rather than its rest mass.   (Why only "broadly equivalent"?  At relativistic speeds, where relativistic mass would be significantly different to rest mass, we'd be better off abandoning Newtonian mechanics and Newtonian gravity entirely and using General Relativity.   Patching up Newtonian gravity with relativistic mass is only going to be a rough or crude adjustment you could make).

Could the ' Higgs field ' twist, tangle, entangle in on itself?

   I don't know.   The Higgs field isn't an ordinary physical thing and I don't suppose it's very useful to think of it as a thing that can twist and tangle in any ordinary sense.   However, such terminology may exist in some very specialised models and areas of Physics that I haven't seen.

Best Wishes.

[Eternal Student]

Hi.

About LIGO and gravitational waves:
     A lot of physicists thought it would be impossible to detect the effects of gravitational waves.   On the face of it, you're talking about finding differences in distance measurements that are smaller than the width of a proton.   There were a few physicists writing books at the time just before LIGO was commissioned or when construction had only just started.   They wanted to have a chapter on LIGO but many thought "this is never going to work" so they didn't bother.   So you're  ( @McQueen ) in good company if you think there would be problems like noise dominating any actual meaningful signal.

    However, it did seem to work.   @Kryptid has already mentioned quite a lot about this.   Moreover, I don't think we had any idea about how common black hole or neutron stars mergers actually are.   The equipment probably is failing to detect a lot of them but it doesn't seem to matter - there are so many of them every year.

Best Wishes.

[Zer0]

@McQueen

I think i get the gist of what you are tryin to say, i might be misunderstanding, but still...

The official " Speed of Light " in a vacuum keeps changing every Century.

Perhaps, a hundred years from now, it won't be what it is today.
Obviously, the ' Speed ' is not changing in Reality, just our instrumentations are getting more precise n accurate n averaging becomes better.

But if all we have are hypothetical models to describe Reality, hence if our Theories change, then so do our Realities!
(gotcha)

ps - @Eternal
Thanks for the replies, always a Treat!
Still, a little shorter, a little less sweet,
Well help me in avoiding DiabeteeZ!

[alancalverd]

The official " Speed of Light " in a vacuum keeps changing every Century.

Perhaps, a hundred years from now, it won't be what it is today.

Since the end of the last century, the speed of light in a vacuum has been defined as constant, and everything else as potentially variable, so distance  is "c x time"  and so forth.

[McQueen (OP)]

However, it did seem to work.   @Kryptid has already mentioned quite a lot about this.   Moreover, I don't think we had any idea about how common black hole or neutron stars mergers actually are.   The equipment probably is failing to detect a lot of them but it doesn't seem to matter - there are so many of them every year.

                    Thank you Eternal Student for your informative answer. But notwithstanding that, the facts should be stated. The merger of black holes that was first detected by LIGO was 1 billion light years away, since 1 billion light years is approximately 9.46 x 10^15 m , one billion light years would be 9.46 x 10^24 m , since the signal would weaken inversely with the square of the distance, the final signal would be 8.94 x 10^49 times less than whatever the initial signal had been.  Surely, a defense of a result involving such numbers would be purely philosophical regardless of how sophisticated the computers that were used were?

[Kryptid]

Surely, a defense of a result involving such numbers would be purely philosophical regardless of how sophisticated the computers that were used were?

It's a testament to just how much energy was released by the merger (about 3.1 solar masses worth of energy, which is an awful lot when you put it into E=mc²). We already know that radiation can be detected over such immense distances, as we've seen a supernova over 10 billion light-years away.

[alancalverd]

Galileo summed up the argument very neatly: eppur si muove.

[McQueen (OP)]

Galileo summed up the argument very neatly: eppur si muove.

                           But it moves!  and also: "In questions of science the authority of a thousand is not worth the humble reasoning of a single individual." - Nelle questioni scientifiche l'autorit? di mille non vale l'umile ragionamento di un solo individuo

[Kryptid]

"In questions of science the authority of a thousand is not worth the humble reasoning of a single individual."

I hope that wasn't supposed to be an argument in favor of you being right. Your reasoning basically falls into the "argument from incredulity" fallacy. You say how unbelievable you find it that we have detected gravitational waves, thus you conclude that we have not actually detected them. It would do you well to further research how LIGO works and how it manages to get the needed sensitivity to work.

[alancalverd]

Of course it is unbelievable. Like the heliocentric universe, and the idea that I can talk to anyone, anywhere in the world, by pushing a few buttons on a piece of plastic.

But science is about facts, not belief, and engineering is about making the unbelievable happen.

[hamdani yusuf]

Of course it is unbelievable. Like the heliocentric universe, and the idea that I can talk to anyone, anywhere in the world, by pushing a few buttons on a piece of plastic.

Heliocentric universe is unbelievable if we still use Aristotelian model of natural world, with many unknowns regarding the masses of celestial objects like planets and stars, and mechanisms that govern their motions and interaction.

[hamdani yusuf]

The official " Speed of Light " in a vacuum keeps changing every Century.

Perhaps, a hundred years from now, it won't be what it is today.

Since the end of the last century, the speed of light in a vacuum has been defined as constant, and everything else as potentially variable, so distance  is "c x time"  and so forth.

What makes you think it will never be changed again in the future?

[alancalverd]

If somebody comes up with a better model than relativity, we might indeed have to base our physics on a new constant. No big deal, as long at it degenerates to the einsteinian or newtonian solution in appropriate circumstances and predicts what happens when those conditions are not met..

[hamdani yusuf]

If somebody comes up with a better model than relativity, we might indeed have to base our physics on a new constant. No big deal, as long at it degenerates to the einsteinian or newtonian solution in appropriate circumstances and predicts what happens when those conditions are not met..

Under the expanding universe model, speed of light doesn't seem to be a constant, especially over a long distance.

[Kryptid]

Under the expanding universe model, speed of light doesn't seem to be a constant, especially over a long distance.

Source?

[alancalverd]

Which doesn't imply a variation in c.