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This article discusses LIGO's detection of gravitational waves as a problem for alternate theories of gravity. But the claim of that discovery seems to have bee

This article discusses LIGO's detection of gravitational waves as a problem for alternate theories of gravity. But the claim of that discovery seems to have been withdrawn by the LIGO team. Here: https://www.nature.com/news/gravitational-waves-discovery-now-officially-dead-1.16830 https://www.nature.com/news/gravitational-waves-discovery-no... I'm an amateur but something feels amiss to me here. Can anyone shed more light on this contradiction?

bmuon 8y ago
I thought they had confirmed LIGO's detection of gravitational waves coming from a certain pulsar that Fermi saw independently. The article you link to seems to be about gravitational waves from the background. I'm also curious now.
civilitty 8y ago
That article is about a redaction from the research team at BICEP2, a telescope in the South Pole. It has nothing to do with the Super LIGO detector, which has detected gravitational waves from black hole collisions several times now.
- pdkl95 8y ago
  LIGO's comments[1] about the 6 gravitational wave detections they are currently confirming (and related publications): [1] https://www.ligo.org/detections.php https://www.ligo.org/detections.php After following the major science experiments over the last ~15 years, I've gotten the impression that the LIGO team is being very careful to not announce anything prematurely. In an interview[2] with Prof. Rana Adhikari about the first detection, he describes how incredibly lucky it was to detect a very strong wave in the middle of the detector's sensitivity range, only ~30 minutes after each site independently enabled data collection. That's the type of situation that raises serious questions about the validity of the data and might even suggest sabotage (someone could be faking data). Fortunately, it sounds like they were careful to investigate the alternative explanations, including searching the labs for anything that looked like a possible sabotage device. It's always good to see scientists paying extra attention to rigor. [2] https://www.youtube.com/watch?v=ViMnGgn87dg https://www.youtube.com/watch?v=ViMnGgn87dg
  - nonbel 8y ago
    Wow, I just read about the latest gravitational wave and I see that once again they detected it by deviating from the procedure used to generate the background model: >"Although such times are in general not included in searches, it was determined that LHO strain data were unaffected by the procedure at frequencies above 30 Hz, and may thus be used to identify a GW source and measure its properties." https://www.ligo.org/detections/GW170608/paper/GW170608_submitted.pdf https://www.ligo.org/detections/GW170608/paper/GW170608_subm... I'm not saying they aren't seeing anything, but the false alarm rate calculations are meaningless unless they process the data the exact same way for background. They keep making these special exceptions every time. EDIT: Mostly just saving this for myself... Here it is for the 5th detection: >"Single-detector gravitational-wave triggers had never been disseminated before in low latency. Given the temporal coincidence with the Fermi-GBM GRB, however, a GCN Circular was issued at 13:21:42 UTC (LIGO Scientific Collaboration & Virgo Collaboration et al. 2017a) reporting that a highly significant candidate event consistent with a BNS coalescence was associated with the time of the GRB." http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 4th detection: This one looks clean (but for the 1st detection the questionable info was not included in the main paper). https://www.ligo.org/detections/GW170814/paper/GW170814-PRLpublished.pdf https://www.ligo.org/detections/GW170814/paper/GW170814-PRLp... 2nd detection: >"Since GW150914 had already been confirmed as a real gravitational-wave signal [4], it was removed from the data when estimating the noise background." http://link.aps.org/doi/10.1103/PhysRevLett.116.241103 http://link.aps.org/doi/10.1103/PhysRevLett.116.241103 Earlier discussion about 1st and 3rd detections: Its claimed "significance estimates come solely from the offline analysis", which seemed to satisfy me at the time... https://news.ycombinator.com/item?id=14462719 https://news.ycombinator.com/item?id=14462719

bmuon 8y ago

I thought they had confirmed LIGO's detection of gravitational waves coming from a certain pulsar that Fermi saw independently. The article you link to seems to be about gravitational waves from the background. I'm also curious now.

civilitty 8y ago

That article is about a redaction from the research team at BICEP2, a telescope in the South Pole. It has nothing to do with the Super LIGO detector, which has detected gravitational waves from black hole collisions several times now.

pdkl95 8y ago
LIGO's comments[1] about the 6 gravitational wave detections they are currently confirming (and related publications): [1] https://www.ligo.org/detections.php https://www.ligo.org/detections.php After following the major science experiments over the last ~15 years, I've gotten the impression that the LIGO team is being very careful to not announce anything prematurely. In an interview[2] with Prof. Rana Adhikari about the first detection, he describes how incredibly lucky it was to detect a very strong wave in the middle of the detector's sensitivity range, only ~30 minutes after each site independently enabled data collection. That's the type of situation that raises serious questions about the validity of the data and might even suggest sabotage (someone could be faking data). Fortunately, it sounds like they were careful to investigate the alternative explanations, including searching the labs for anything that looked like a possible sabotage device. It's always good to see scientists paying extra attention to rigor. [2] https://www.youtube.com/watch?v=ViMnGgn87dg https://www.youtube.com/watch?v=ViMnGgn87dg
- nonbel 8y ago
  Wow, I just read about the latest gravitational wave and I see that once again they detected it by deviating from the procedure used to generate the background model: >"Although such times are in general not included in searches, it was determined that LHO strain data were unaffected by the procedure at frequencies above 30 Hz, and may thus be used to identify a GW source and measure its properties." https://www.ligo.org/detections/GW170608/paper/GW170608_submitted.pdf https://www.ligo.org/detections/GW170608/paper/GW170608_subm... I'm not saying they aren't seeing anything, but the false alarm rate calculations are meaningless unless they process the data the exact same way for background. They keep making these special exceptions every time. EDIT: Mostly just saving this for myself... Here it is for the 5th detection: >"Single-detector gravitational-wave triggers had never been disseminated before in low latency. Given the temporal coincidence with the Fermi-GBM GRB, however, a GCN Circular was issued at 13:21:42 UTC (LIGO Scientific Collaboration & Virgo Collaboration et al. 2017a) reporting that a highly significant candidate event consistent with a BNS coalescence was associated with the time of the GRB." http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 http://iopscience.iop.org/article/10.3847/2041-8213/aa91c9 4th detection: This one looks clean (but for the 1st detection the questionable info was not included in the main paper). https://www.ligo.org/detections/GW170814/paper/GW170814-PRLpublished.pdf https://www.ligo.org/detections/GW170814/paper/GW170814-PRLp... 2nd detection: >"Since GW150914 had already been confirmed as a real gravitational-wave signal [4], it was removed from the data when estimating the noise background." http://link.aps.org/doi/10.1103/PhysRevLett.116.241103 http://link.aps.org/doi/10.1103/PhysRevLett.116.241103 Earlier discussion about 1st and 3rd detections: Its claimed "significance estimates come solely from the offline analysis", which seemed to satisfy me at the time... https://news.ycombinator.com/item?id=14462719 https://news.ycombinator.com/item?id=14462719