I have participated in episode 401 of the Coffee Break podcast: Signal and Noise [iVoox, iTunes], entitled “Ep401: Earth Rotation; JWST; VIRGO; Medina Azahara; Agujeros Negros», Feb 02, 2023. «The weekly gathering in which we review the latest scientific news. In today’s episode: Resolved the fault in NIRISS, from the JWST (min 9:00); The miscounted rotation of the Earth’s core (26:00); VIRGO, gravitational waves and environmental noises (1:04:11); Did the earthquakes cause the abandonment of the caliphal city of Medina Alzahara? (1:56:00); “Supermassive” black holes in distant dwarf galaxies (2:22:00). All the comments made during the gathering represent only the opinion of the person who makes them… and sometimes not even that.
Go download episode 401.
As the video shows, we participate by videoconference Héctor Socas Navarro @HSocasNavarro (@pCoffeeBreak), Elizabeth Cordero @FuturaConjeturaSara Robisco Cavite @SaraRC83, José Edelstein @JoseEdelsteinGastón Giribet @GastonGiribetand Francis Villatoro @emulenews.
Héctor tells us about the problem that a JWST instrument has had. On January 15, 2023, NIRISS went offline (Near Infrared Imager and Slitless Spectrograph), the spectroscope between 0.6 and 5 µm for exoplanetary atmospheres developed by the Canadian Space Agency (CSA); there was a delay in the internal communications of the instrument that caused the software to shut down. It was rebooted and there seemed to be no damage. Problem analysis found the cause, a high-energy galactic cosmic ray that disrupted electrical systems. After restarting the instrument it seemed to work fine; A test observation was made on January 28, and it was confirmed to work perfectly on January 30. So NIRISS is back in science mode. More information in Doris Elín Urrutia, “NASA finds the culprit behind a Webb Telescope malfunction: powerful cosmic rays,” Inverse, 31 Jan 2023.
My turn to talk “On the Possible Seven-Decade Oscillation of the Differential Rotation of the Earth’s Solid Core,” LCMF, Jan 28, 2023, on the article Yi Yang, Xiaodong Song, “Multidecadal variation of the Earth’s inner-core rotation,” Nature Geoscience (23 Jan 2023), doi: https://doi.org/10.1038/s41561-022-01112-z; more information in Yi Yang, Xiaodong Song, “Rotation of the Earth’s inner core changes over decades and has come to near-halt,” Nature Geoscience (23 Jan 2023), doi: https://doi.org/10.1038/s41561- 022-01113-y.
«The core of the Earth is made up of a solid core surrounded by a liquid core; beyond are the mantle, upper mantle, and crust. In 1996 the differential rotation of the solid core was observed, which rotates at a slightly different speed than the mantle and crust. Several theoretical models proposed that such differential rotation would be oscillatory. Indications are published in Nature Geoscience that said oscillation (dt) has a period of about 70 years; this period resembles that of the variations in the length of the day (LOD) and the Earth’s magnetic field. Repetitive seismic waves have been used that travel the same path through the solid core between their source and the seismological station; 56 years of seismic data have been analyzed, between 1964 and 2021, analog (with greater error) until the 1970s and digital since the 1980s. The oscillation had a minimum near 1970 and a maximum near 2009; since a complete oscillation has not been observed, it is not known whether it is periodic or quasi-periodic. Future studies will have to confirm these indications.”
«The surprising thing about this scientific news is not the published results but how they have been disseminated in the media. Beyond the references to the certified film “The Core” (2003), “El núcleo” in Spain, the news headlines have been very poor; affirming that the Earth’s core has stopped or connecting its differential rotation with climate change, does not make any sense. Many media have rectified, after consulting their head geologists (we must thank them for their work), but the damage was already done. It is surprising that for some journalists, when reporting scientific news, what a film tells is more relevant than the opinion of scientists. Forgetting this matter, what must be highlighted in the new work is that the indications found have low statistical significance and that future studies are required to elevate them to evidence. Although the theoretical models suggest that such an oscillation must exist, we should not be guided by the confirmation bias. The seismic data analyzed cover a range of about 56 years, less than the 70 years of the apparent multi-decadal oscillation, with the most relevant data being the scarcest historical data. Without many more historical data it will be very difficult to confirm the oscillation in the next decades.
Isabel tells us that the Virgo gravitational wave detector can be used as a detector of environmental noises (which are detected to eliminate them from the data). Geophysical noise sources (wind, ocean waves, and earthquakes) and anthropogenic noise influence laser interferometers for gravitational wave detection; they are detected in order to compensate them or to discard the data they influence. The Virgo Collaboration publishes in Classical and Quantum Gravity an analysis of these noises in the third observation period (O3, from April 1, 2019 to March 27, 2020). This type of detection may be of scientific interest in its own right. The figure above shows three weeks of anthropogenic noise data and how it is reduced on weekends.
Isabel tells us that the most relevant noises are seismic. On average three earthquakes per month have caused the loss of the control point on the interferometer, which requires observation detection and laser realignment. She comments Héctor that he expects there to be a noise continuum, a seismic barrier, which Isabel comments occurs below 10 Hz.
There is a lot of environmental data that Virgo records that could have application to geophysicists, climatologists, and various environmental scientists. The article is The Virgo Collaboration (Acernese et al.), “The Virgo O3 run and the impact of the environment,” Classical and Quantum Gravity 39: 235009 (29 Nov 2022), doi: https://doi.org/10.1088 /1361-6382/ac776a, arXiv:2203.04014 [gr-qc] (08 Mar 2022); a summary in Nicolas Arnaud et al.,External environmental noise influences on Virgo during O3,” arXiv:2204.03993 [gr-qc] (08 Apr 2022).
Sara tells us that an article has been published that analyzes archaeoseismological samples from Medina Azahara (Córdoba, Spain), which show that it suffered seismic damage at the beginning of the 11th century. The Caliphate City of Medina Azahara was built in 936–937 (or 940–941 depending on the source) by the first caliph of al-Andalus Abd al-Rahman III. It is usually affirmed that the abandonment and destruction of the city occurred in the civil war (fitna de al-Andalus) that began between 1009 and 1010. But an archaeoseismological study indicates that earthquakes played a relevant role in the sudden abandonment of the city . Multiple effects of earthquakes are observed, such as falling keystones in arches, leaning walls, conjugate fractures in brick walls, conjugate fractures and folds in regular pavements, and broken dip corners in columns. Geological and structural analysis indicates that much of the observed damage can be attributed to an earthquake that devastated Medina Azahara during the 11th or 12th centuries. There are two possible candidates, the two strong earthquakes that occurred in 1024-1025 and in 1169-1170.
The article is Miguel Angel Rodriguez-Pascua, Maria Angels Perucha, …, Yolanda Sanchez-Sanchez, “Archaeoseismological Evidence of Seismic Damage at Medina Azahara (Córdoba, Spain) from the Early 11th Century,” Applied Sciences (MDPI) 13: 1601 ( 26 Jan 2023), doi: https://doi.org/10.3390/app13031601 .
Gastón tells us about the observation of supermassive black holes in dwarf galaxies in the early universe. Seven dwarf galaxies have been observed with a redshift between z=0.35 and z=0.93 (when the universe was between 10 billion and 6 billion years old); these dwarf galaxies harbor supermassive black holes with more than a million solar masses (something that had only been observed in low-z galaxies). Galaxies and their supermassive black holes are thought to coevolve (grow in mass at the same rate), but the new observations correspond to black holes having grown faster than their host galaxies.
The origin of these supermassive black holes would have to be intermediate mass black holes in the early universe (already formed when the universe was about a billion years old). As a result, these black holes would evolve faster than their host galaxies. The article is Mar Mezcua, Malgorzata Siudek, …, Silvia Bonoli, “Overmassive black holes in dwarf galaxies out to z∼0.9 in the VIPERS survey,” arXiv:2212.14057 [astro-ph.GA] (28 Dec 2022), doi: https://doi.org/10.48550/arXiv.2212.14057; more informative information in Alba Calejero, “Supermassive black holes found in distant dwarf galaxies,” News, CSIC, 30 Jan 2023.
Enjoy the podcast!