Isn't that what they need the third detector to come online for to help with this?
Quote from: gosnold on 02/11/2016 06:18 pmHow do they know the distance between us and the event?Isn't that what they need the third detector to come online for to help with this?
How do they know the distance between us and the event?
Quote from: eeergo on 02/11/2016 06:27 pmThey measured the redshift (I'm not sure how, since this event was not accompanied by electromagnetic (i.e. light/X-ray/UV...) detection, so it's not obvious to me what reference they used for "redshifted gravitational waves" - maybe Jonathan can help? ) and, assuming this standard Universe expansion model, got a distance value that would cause that redshift. This turned out to be between 250 and 570 megaparsecs.Aren't these ultra-violent astrophysical events like Supernova explosions and Black Hole collisions supposed to give off gamma-ray bursts at the same time? Shouldn't they have detected an accompanying gamma-ray burst signal simultaneously in connection with the gravity waves?
They measured the redshift (I'm not sure how, since this event was not accompanied by electromagnetic (i.e. light/X-ray/UV...) detection, so it's not obvious to me what reference they used for "redshifted gravitational waves" - maybe Jonathan can help? ) and, assuming this standard Universe expansion model, got a distance value that would cause that redshift. This turned out to be between 250 and 570 megaparsecs.
Quote from: Star One on 02/11/2016 06:41 pmIsn't that what they need the third detector to come online for to help with this?They need it to better be able to triangulate the source direction in the sky. The more the better.
Sir Alex FergusonSir Alex Ferguson – @Furious_FergieJust had Wayne Rooney on the phone asking if gravitational waves are like Mexican waves.I just said aye.
Quote from: notsorandom on 02/11/2016 06:11 pmWhat would that even look like up close? What would that intensity of gravitational wave energy do to things?Unless I messed up my back-of-the-envelope calculations, even only 1 AU from the black hole pair the strain would be at parts per billion level.
What would that even look like up close? What would that intensity of gravitational wave energy do to things?
Actually it's more like 4 orders of magnitude... https://en.m.wikipedia.org/wiki/Orders_of_magnitude_(energy) but I agree with the idea :0
Another articlehttp://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-timeThis is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!
Quote from: FinalFrontier on 02/11/2016 10:40 pmAnother articlehttp://www.sciencemag.org/news/2016/02/gravitational-waves-einstein-s-ripples-spacetime-spotted-first-timeThis is so exciting. We might finally be getting closer to understanding how and what gravity actually is. If we can crack that nut it may eventually be possible for us to get to make artificial gravity a thing. That would have HUGE impacts for our entire civilization, but the biggest hurdle so far has even been understanding how gravity works and what exactly gravity is. Now we are solving that. Congratulations to the LIGO teams!Currently, we are finding that the "graviton" is basically massless. This basically confirms our theories. So far, this LIGO detection is pounding more nails in the coffin of the idea of artificial gravity and other hypothetical phenomenon that require new physics. We HOPE new discoveries start to pull some of those nails out, but the recent announcement was another one pounded in.
Quote from: ugordan on 02/11/2016 06:31 pmQuote from: gosnold on 02/11/2016 06:18 pmHow do they know the distance between us and the event?If I understood it correctly, using the observed shape of the waveform one can infer the masses involved and then the theory also gives you the energy (or power?) radiated. Then you go back to the observed amplitude of the oscillations (a.k.a. the local "strain") and, via the inverse square law, can work out the distance. With a certain error bar, of course.Yes, that gives the luminosity distance (for very far away objects there are several "distances"). They just convert the luminosity distance to redshift, because that's what everyone is used to in cosmology/extragalactic astronomy.Edit: The conversion from luminosity distance to redshift does depend on the cosmological model as eeergo mentioned, but in this case the merger was close enough so that it doesn't have a large effect.
Quote from: gosnold on 02/11/2016 06:18 pmHow do they know the distance between us and the event?If I understood it correctly, using the observed shape of the waveform one can infer the masses involved and then the theory also gives you the energy (or power?) radiated. Then you go back to the observed amplitude of the oscillations (a.k.a. the local "strain") and, via the inverse square law, can work out the distance. With a certain error bar, of course.
The observed frequency of the signal is redshifted by a factor of (1 + z), where z is the cosmological redshift. There is no intrinsic mass or length scale in vacuum general relativity, and the dimensionless quantity that incorporates frequency is fGm/c^3. Consequently, a redshifting of frequency is indistinguishable from a rescaling of the masses by the same factor. We therefore measure redshifted masses m, which are related to source frame masses by m= (1 + z)·m_source. However, the GW amplitude A_GW, Eq. (2), also scales linearly with the mass and is inversely proportional to the comoving distance in an expanding universe. This implies that A_GW ~ 1/D_L and from the GW signal alone we can directly measure the luminosity distance, but not the redshift.The observed time delay, and the need for the registered signal at the two sites to be consistent in amplitude and phase, allow us to localize the source to a ring on the sky [34, 35]. Where there is no precession, changing theviewing angle of the system simply changes the observed waveform by an overall amplitude and phase. Furthermore,the two polarizations are the same up to overall amplitude and phase. Thus, for systems with minimal precession, thedistance, binary orientation, phase at coalescence and sky location of the source change the overall amplitude andphase of the source in each detector, but they do not change the signal morphology. Phase and amplitude consistencyallow us to untangle some of the geometry of the source. If the binary is precessing, the GW amplitude and phase havea complicated dependency on the orientation of the binary, which provides additional information.