There is a lot to like about this paper..

I had heard the story about Einstein's vacillation, and his ire at the rejection of his GW paper with Rosen - at a GR21 plenary lecture - but this is a great intro for those who did not have that privilege. There is indeed a lot we can learn about or test in theories of gravity, by studying gravitational waves. I too am an advocate that we need to have GW instruments with sufficient sensitivity and bandwidth to discern which cosmological theories work. I got to talk a little with, and Andy Beckwith talked quite extensively with, Paul Steinhardt regarding primordial gravity waves - and how current detectors are not nearly good enough.

But Strominger's talk at GR21 focused on how even the meager observations to date allow us to constrain our choices of alternative gravity theories. I am somewhat undecided about whether GR, extended relativity theories, modified gravity, or quantum gravity, yields the correct answer. My intuition tells me that strict general relativists try to carry things a bit too far, and end up with unphysical assumptions and false predictions, so there has to be some modification to make gravity work as we see it in nature. Have you seen the recent papers talking about an echo in BH merger GWs? This is supposed to be a signal for quantum gravity, according to the authors. What do you think?

I have to agree with George Ellis's comment above, that the subject matter is somewhat off topic. But I think, especially after seeing Nathan's comments, that a slight change in the narrative could have brought the subject back into focus. For example; talking about how even Einstein the founder's mind and opinion wandered about the reality of GWs could have made that section work like a charm, to deliver a message of how the wandering led to a goal. But the linkage failed to appear within the body of your paper, so I can only give partial credit for that, in what is otherwise an excellent paper.

All the Best,

Jonathan

    Sorry Steve. Then, I hope to re-meet you in next Essay Contest.

    Cheers, Ch.

    Hi dear Jonathan,

    Thanks for your valuable comments.

    On one hand, I agree with your point of view that that strict general relativists try to carry things a bit too far and maybe we need some modification to make gravity work as we see it in nature. On the other hand, solar system tests are extremely precise. Thus, it seems that such a modification of general relativity should be very weak, see this technical paper of mine. Thanks for signaling the recent papers talking about an echo in BH merger GWs, I will read them soon.

    Concerning your and Ellis' criticism on the issue that the subject matter is somewhat off topic, I still emphasize the remarkable observation of Jack Hamilton James. He argues that our Essay is a unique and opposite way into the essay contest. In fact, the other Essays start with the external world and try to show how it produces intention. In our Essay we point out to start with maths and try and work it to fit the external world.

    Cheers, Ch.

    Thank you Very much Corda,

    For your kindness and support.

    Best Regards

    =snp.gupta

    Hi Christian,

    1. You essay is on topic. If I may summarize: Mathematics a lot of hard work = reality

    2. The essay was a fascinating read about the current events and history of gravity waves. And I did not needed aspirin and a nap after reading it! It is not as short as my essay, but that is OK.

    3. I will vote for your essay as many times as it takes to defeat the trolls :)

    4. I stumbled onto a way calculate the precession of Mercury without using GR. Created two papers that were recently published. I did not believe I could make this calculation, and not completely clober GR. Yes, very strange. Would you take a look ....I think it may generate some ideas. I will e-mail to you.

    Thanks for being in the contest.

    Don Limuti

      Hi Don,

      Thanks for your message with kind words. We are honored by your judgment on our Essay. Concerning the way to calculate the precession of Mercury without using GR, I know that there is some way which involves the equivalence principle. In that case, combining the equivalence principle with the precision of solar system tests, the strong implication is that the correct theory of gravity must be GR or some weak modification of GR, independently by the precession of Mercury. In any case, I will reply you by email.

      Cheers,

      Ch.

      Christian, Reza and Nathan,

      I checked out your essay and noted your response to questions about GR connections to the contest theme. I have been following the desire to go beyond observation of the BB with light using GR, and it now seems possible to do this with more resonance with LIGO upgrades and more than 2 stations. Such an achievement certainly connects our parochial world with the ultimate beginning. Perhaps you should have emphasized the ultimate BB potential more.

      Hope you get a chance to check out my approach.

      Regards,

      Jim Hoover

        Hi Jim,

        Thanks for your interesting comments. Concerning the possibility to observing the BB through GWs with LIGO upgrades and more than 2 stations, give a look to this paper of mine.

        Thanks again, I will read, comment and score your Essay soon.

        Cheers, Ch.

        There is something wrong in the link help page today. In any case, here is the paper: https://arxiv.org/abs/1110.1772

        Impressive, Christian. Since I first heard about the LIGO efforts, I have been fascinated by the prospect of breaking the light barrier and detecting what constitutes the BB, perhaps in our lifetime. I have a feeling will not solve the ultimate mystery but open up more pointed questions about our beginnings.

        Jim

        Thanks for your kind words.

        Christian, et al,

        I found your essay clear, well written and nice to read and interesting too. I knew Einstein had changed his mind on GW's (and many things) but not quite how much! OK the links with the topic were a touch homeopathic, but frankly I blame the topic, pregnant with quintupletaly poor assumptions and able to link to anything in physics!

        On GW's. I agree they exist and further that they are indeed a 'no brainer' and, this may shock, but I long ago designed a detector which still works perfectly. You tell me if you think it's flawed; I use water but must point out your analogy IS flawed as in space there's no 'surface' or medium interface on which the waves may form. I was then a bit disappointed you didn't get into what GW's 'ARE', which I consider best described simply as 'fluctuations in gravitational potential' due to positional changes (normally orbital) of the massive bodies. Do say if you think that's wrong, but I found definition important for detection.

        The set up? It uses the 'large elephant' scenario; There's always a large elephant in the room nobody has noticed; So practically; take a large volume of fluid with a long 'arm' length, then pass a massive body above it, slowly and repeatedly. Sure enough I find a detectable change in level and even a 'flow' corresponding to the motions. Using TWO massive bodies, together, opposite or orthogonally, and at different distances modifies the level and flow in a predictable manner. I have sets of 'tidal prediction' tables, not always precise but very good approximations. You can get copies here; gravity wave tidal predictions.

        The large set up and gauge is outside my office, with a max height range of 5.8m when in conjunction and peak flow of 3.1knots. It did need bodies the size of a star and small moon and the liquid volume of the North Sea and Atlantic to get that scale of change, but smaller works too. In the Med the max is some 1.5m (which Venitians are thankful for!)

        What I'm pointing out is that this really is exactly the SAME effect as the fluctuating potentials from two BINARY AGN's (or 'black holes' in old money). It's just so familiar and BIG it becomes invisible as we habitually don't apply fully evolved brain power to seeing it!

        In fact rather like the classical derivation of QM predictions in my essay!

        If you fancy collaborating on a paper I'm up for it, but it may be too shocking for the LIGO lot! Anyway very well written and thank you for the greater definition of history. Another top score coming to counter the non-reader trolling with 1's (I've now reached double figures!)

        Very Best

        Peter

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          • Post #49

          Dear Christian, et al,

          I have read with a great interest your essay which certainly deserves an appreciation and first of all for its ontological orientation.

          I did not doubt the experimental proof of the wave nature of gravitation, since it confirms my theoretical researches and conclusions concerning the mechanism of interactions. I consider all interactions (including gravitational) as wave reaction to the disturbance of material system caused by change of energy.

          I wish you further creative successes.

          Vladimir Rodin

            Dear Christian and fellow authors,

            Thank you for reading (and bemoaning) my assault on Einstein's physics which I defended on my page. Somebody (could be me) said Einstein was right although he arrived at his results in the wrong way. Anyway your essay is very well written and interesting which made a pleasant reading.

            Permit me to use the assumptions of my Beautiful Universe Model (BU), which is a sort of Cellular Automata description of physics, to speculate about gravitational waves.

            From my diffraction research I have concluded that gravity is akin to the distortion of the dielectric ether around matter - creating a density field that has a gradient index of refraction that - for example- bends light - an idea that also goes back to Thomas Young then Eddington . From there it is an easy step to say that de Broglie-like wave fields surrounding matter are associated with gravitational fields, and that when disturbed by motion this field generates waves.

            So you see that once one is free from the fetters of spacetime formulations physics seems lighter and freer to proceed to new horizons!

            Before dismissing CA theories please consider Gerard 't Hooft's new book showing Quantum Mechanics can emerge from CA. Can relativity be far behind?

            Cheers

            Vladimir

              Dear Peter,

              Thanks for your kind words and for appreciating our Essay.

              Concerning your proposal to detect GWs, the key point is that the effect of a propagating GW on a fluid is should be very weak. Thus, how can one extract the 'flow' corresponding to the motions from the various noises which are, in principle, present? I cannot see your sets of 'tidal prediction' tables because the link that you inserted does not work. Can you kindly re-insert it?

              Thanks again and good luck in the Contest.

              Cheers, Ch.

              P.S.

              As usual, lots of us are having the problem of trolls who give various 1's...

              Dear Vladimir,

              Thanks for your appreciation of our Essay.

              Your idea to consider interactions as wave reaction to the disturbance of material system caused by change of energy is interesting, but I think that it could work for the propagation of the interactions. When one analyzes the sources of the interaction, I think that one needs to go beyond the linear approximation.

              Thanks again and good luck in the Contest.

              Cheers, Ch.

              Dear Vladimir,

              Thanks for your kind comments.

              I do not see your vision of gravitation so different with respect to Einstein's vision. Replacing "dielectric ether" with "space-time" one finds an analogy.

              In addition, I do not want to dismiss CA theories. Gerard 't Hooft's approach is an attempt to insert determinism in quantum mechanics, and I agree with him.

              Thanks again and good luck in the Contest.

              Cheers, Ch.

              Thanks for your appreciation, dear Jim. We will see if we will detect what constitutes the BB in our lifetime. It should be very intriguing. I also agree with you that this will not solve the ultimate mystery but will surely open up more pointed questions about our beginnings. This is the beauty of science.

              Cheers, Ch.

              Christian, et al,

              It's a great time to be a relativist, isn't it? :-)

              You've written a marvelous essay, expertly exposing the importance of LIGO, and the challenges ahead, deserving my highest mark.

              Please allow me to focus on:

              " ... if a GW propagates in a region of space-time where two free-falling test masses are present, the GW effect will drive the masses to oscillate."

              In fact, only the phenomenon of oscillation allows us to know that a mass is present.

              "Concerning the previously cited possibility of ultimately discriminating between the general theory of relativity and extended theories of gravity, only a perfect knowledge of the motion of the test masses, which are the beam-splitter and the mirrors of the interferometer, will permit one to determine if the general theory of relativity is the definitive theory of gravity."

              General relativity was never intended to be the definitive theory of gravity. It was, as you imply, an intermediate step on the way to a unified field theory. If the test particles are falling in a positively curved trajectory (the geodesic of a positive curvature), they will interact. If in a negative trajectory, they won't. What could one possibly mean, however, by a 'negative trajectory'? Einstein said he thought of a quantum "... as a singularity, surrounded by a large vector field. With a large number of quanta a vector field can be composed that differs little from the one we presume for radiation."

              What better candidate for the mother of all fields than the neutrino field? What better source of consciousness than spacetime itself, compelling us to remember a trajectory we can never return to, and which perhaps never existed? I hope you get a chance to read my essay.

              All best,

              Tom