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Showing content with the highest reputation on 11/25/18 in all areas

  1. 1 point
    https://www.newscientist.com/article/mg24032022-600-exclusive-grave-doubts-over-ligos-discovery-of-gravitational-waves/ Exclusive: Grave doubts over LIGO’s discovery of gravitational waves """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" Sensationalisitc headlines? My thoughts? Whatever the outcome, in my view it again supports the scientific methodology as superior to anything we have. I'll let those far more initiated in this sort of stuff to offer comments, rather then my own. Interesting to say the least. [Perhaps someone could E-Mail aLIGO or VIRGO for a comment?] https://arstechnica.com/science/2018/10/danish-physicists-claim-to-cast-doubt-on-detection-of-gravitational-waves/ Danish physicists claim to cast doubt on detection of gravitational waves LIGO responds: "There is absolutely no validity to their claims." <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>> https://arstechnica.com/science/2018/10/danish-physicists-claim-to-cast-doubt-on-detection-of-gravitational-waves/ extract: "Then, in 2014, the BICEP2 collaboration—which hunts for telltale signatures of gravitational waves in the cosmic microwave background (the leftover radiation from the Big Bang)—announced it had detected indirect evidence of these ripples in the fabric of spacetime. Much fanfare ensued. Within weeks, however, serious doubts had begun to emerge. Ultimately, it turned out that the BICEP collaboration had mistaken clouds of cosmic dust for a signal. The blow was crushing. The gravitational-wave community was sufficiently burned by the BICEP2 debacle that LIGO opted for extreme caution and secrecy—ironically a big part of the reason the collaboration is viewed with distrust in some quarters. Its researchers spent several months between the signal detection and the official announcement in February 2016 to double, triple, and quadruple check their analysis to guard against another false detection. So how could this happen again? First, it's highly unlikely that it has happened again. But the answer is that separating signal from noise is very, very difficult in this kind of analysis. The signal is extremely faint (on the order of a billionth of a billionth the diameter of an atom); that's why you need such sensitive detectors to pick them up at all. Also, the Universe is actually a pretty noisy place. "The problem isn't so much the absolute weakness of the waves; the problem is that there are many other disturbances that also wiggle the interferometer," physicist Sabine Hossenfelder wrote at Forbes back in 2017—the first time Jackson's false-signal claims were making the rounds." https://arxiv.org/pdf/1811.00364.pdf "The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in presence of matter. In this paper, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due to large extra dimensions. Finally, the polarization content of the gravitational wave signal is studied. The results of all tests performed here show good agreement with GR". CONCLUSIONS: Using the binary neutron star coalescence signal GW170817, and in some cases also its associated electromagnetic counterpart, we have subjected general relativity to a range of tests related to the dynamics of the source (putting bounds on deviations of PN coefficients), the propagation of gravitational waves (constraining local Lorentz invariance violations, as well as large extra dimensions), and the polarization content of gravitational waves. In all cases we find agreement with the predictions of GR. The upcoming observing runs of the LIGO and Virgo detectors are expected to result in more detections of binary neutron star coalescences [84]. Along with electromagnetic observations, combining information from gravitational wave events (including binary black hole mergers) will lead to increasingly more stringent constraints on deviations from general relativity [25, 26], or conceivably potential evidence of the theory’s shortcomings.
  2. 1 point
    A very cool animation of the black holes that created the first detected gravitational waves (a simulation, not an "artists impression")
  3. 1 point
    While worded poorly I think this mostly correct. This is what you need to cite or better yet retract because its just wrong. AFAIK the only thing that alters a gravitational field is more or less mass. Also why do you spell gravitational like this "gravit." This is also wrong. It is simple aerodynamics which is why we can and do ignore any gravitational effects. Your not wrong that particles in the air have a gravitational attraction its just that its so small that we can ignore it. Cross posted with Strange.
  4. 1 point
    Thanks beecee for bringing this to my attention and also for all the other science news you post. I don't think it was just "sensationalist media propaganda" although there was an element of that in the story. I think Strange (above) got it about right. I think it is safe to assume for now that gravitational waves have been detected. After all the visual confirmation was the smoking gun IMO. Also I have a lot of respect for David Shoemaker who is on the team. Meanwhile people are out doing science with these results. https://ras.ac.uk/news-and-press/research-highlights/gravitational-waves-merged-hyper-massive-neutron-star Also the next wave of observations is on its way! https://www.ligo.caltech.edu/page/observatory-status Wish we could get interesting stuff like this to go on for 10 pages.
  5. 1 point
    I think people often assume a direct connection between success and intelligence (of any type). I don't think the two are always connected. Sometimes one becomes successful through a series of events beyond their understanding or influence. Other times through low levels of integrity. For example Giorgio Tsoukalos has no background in history, archaeology, or religion yet has flown all over the world to different historical sights as part of the Ancient Aliens show gaining access and exposure true experts ever do. Same goes for the folks on shows like Finding Bigfoot and Ghost Haunters. These individuals don't have some special talent or ability which drives their success. Rather they are just filling a niche which exists in society in-spite of them that educated people in the associated fields have too much integrity for. The Kardashian family draw crowds. Alex Jones draws crowds. Bringing such people onstage at a political rally would earn a politician far more attention than any well written speech or policy idea yet I don't think such is a sign of greater "emotional intelligence" as @koti put it. FoxNews ,Talk Radio, and Faux print journalism built the audience Trump speaks to. Trump just parrots what has already been broadcast for decades. I think people like Rupert Murdoch deserves more credit for the current state of affairs in the U.S. and UK than any current Politician. They pushed and pushed until a Trump and or a Brexit emerged. Here in the U.S. lets not forget that Ron Paul, Newt Gingrich, Ted Curz, Sarah Palin, Rick Perry, Michele Bachmann, Rudy Giuliani, and etc all had serious Presidential bids in recent years. Donald Trump is not magnitudes worse than that lot. Had Trump lost the GOP nomination in 2016 Ted Cruz/Carly Fiorina would have gotten it and not some combo of Romeny, McCain, Corker, Rice, or any other sane Republican. Trump isn't responsible for driving U.S. conservatives off the rails. They were already turned toward the cliff with the pedal all the way down when Trump jump on board.
  6. 1 point
    I just now asked God for a sign and my dog licked herself. I wasn't sure that was how God would present himself to me so I asked for another sign, and my OTHER dog licked herself. If that isn't proof of God I don't know what is.
  7. 1 point
    The paper critical of the aLIGO/VIRGO claims............ https://arxiv.org/pdf/1706.04191.pdf On the time lags of the LIGO signals: Abstract. rXiv:1706.04191v2 [astro-ph.IM] 9 Aug 2017 To date, the LIGO collaboration has detected three gravitational wave (GW) events appearing in both its Hanford and Livingston detectors. In this article we reexamine the LIGO data with regard to correlations between the two detectors. With special focus on GW150914, we report correlations in the detector noise which, at the time of the event, happen to be maximized for the same time lag as that found for the event itself. Specifically, we analyze correlations in the calibration lines in the vicinity of 35 Hz as well as the residual noise in the data after subtraction of the best-fit theoretical templates. The residual noise for the other two events, GW151226 and GW170104, exhibits similar behavior. A clear distinction between signal and noise therefore remains to be established in order to determine the contribution of gravitational waves to the detected signals. Concluding remarks: Ideally, the search for gravitational waves should be separated into two independent phases. An initial template-free step should identify candidate events and demonstrate that they are of astrophysical origin. The second step, which will inevitably involve comparison with general relativistic calculations, should attempt to determine the physical nature of the event. Fortunately, the LIGO GW150914 event is sufficiently strong that it can be seen in both the Hanford and Livingston detectors without templates and that the cross correlation is high. The evidence that this event is astrophysical lies primarily in the fact that this cross correlation is maximized by an inversion of the Livingston data and a 7 ms shift of the record that is within the allowed ±10 ms window. The results of Section 3 suggest, however, that similarly strong agreement between the Hanford and Livingston detectors can be obtained from time records constructed exclusively from narrow resonances in the Fourier transform of the data. In spite of efforts to “cleanse” the data of the effects of these resonances, their strength renders it difficult to be certain that there has not been significant “leakage” of these effects to neighboring frequencies. The strong and unexpected correlations in the phases of the Fourier coefficients noted in Section 2 may be indicative of such leakage. It has been reported for both GW150914 and for GW170104 that the residual noise following from the subtraction of the template from the cleaned data is consistent with Gaussian noise and does not contain features characteristic of gravitational wave signals. (See [1] and [5], respectively) This is taken to imply that there are no biases in the modeling of the waveforms. While our findings do not contradict the previous statement about near Gaussianity during the time of the events, this is to be contrasted with the present demonstration that the residuals show apparent correlations between the detectors. It is striking that these correlations are maximized by applying nearly the same time shifts as found for the GW events themselves — for all three GW events reported to date. The purpose in having two independent detectors is precisely to ensure that, after sufficient cleaning, the only genuine correlations between them will be due to gravitational wave effects. The results presented here suggest this level of cleaning has not yet been obtained and that the detection of the GW events needs to be re-evaluated with more careful consideration of noise properties. <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>>>>>>> My first thoughts are, why has this supposed doubt just raised its head?
  8. 1 point
    Oumuamau has been exhibiting some anomalous accelerations that are of unknown cause. Outgassing is a possibility but such outgassing should be visible but none has been observed.
  9. 1 point
    There is no measurement or observation that indicates that it is that thin. While that would be a requirement for the solar sail hypothesis to valid, this does not mean that it actually is that that thin. There nothing about the measurements we have made of it that indicates that it is made from so thin a material. You got the argument backwards. It is "IF the probe were a light sail then it would need to be very thin", not "It is very thin, so it could be a light sail".
  10. 1 point
    Interesting irony. https://mercyforanimals.org/straws-arent-the-real-problem-fishing-nets
  11. 1 point
    11/15 In all sincerity, thanks to everyone here for getting me to the point where I could score that well!
  12. 1 point
    Only one miss, and I can really not care: "The Large Hadron Collider at CERN uses 1.3 terawatt hours of electricity annually. That’s equivalent to:"
  13. -1 points
    The cosmological redshift is given by the expansion of the Planck-Length dx = sqrt(h*G/c^3) with G = Ru^2*const