R Bamford 1, K J Gibson 2, A J Thornton 2, J Bradford 1, R Bingham 1,6, L Gargate 1,3, L O Silva 3, R A Fonseca 3, M Hapgood 1, C Norberg 4, T Todd 5 and R Stamper 1
Published 4 November 2008 • 2008 IOP Publishing Ltd Plasma Physics and Controlled Fusion, Volume 50, Number
Combing through historical seismic data, researchers using a machine learning model have unearthed distinct statistical features marking the formative stage of slow-slip ruptures in the earth’s crust months before tremor or GPS data detected a slip in the tectonic plates. Given the similarity between slow-slip events and classic earthquakes, these distinct signatures may help geophysicists understand the timing of the devastating faster quakes as well.
“The machine learning model found that, close to the end of the slow slip cycle, a snapshot of the data is imprinted with fundamental information regarding the upcoming failure of the system,” said Claudia Hulbert, a computational geophysicist at ENS and the Los Alamos National Laboratory and lead author of the study, published today in Nature Communications. “Our results suggest that slow-slip rupture may well be predictable, and because slow slip events have a lot in common with earthquakes, slow-slip events may provide an easier way to study the fundamental physics of earth rupture.”
Slow-slip events are earthquakes that gently rattle the ground for days, months, or even years, do not radiate large-amplitude seismic waves, and often go unnoticed by the average person. The classic quakes most people are familiar with rupture the ground in minutes. In a given area they also happen less frequently, making the bigger quakes harder to study with the data-hungry machine learning techniques.
A new study makes a compelling case for the development of “NEMO”—a new observatory in Australia that could deliver on some of the most exciting gravitational-wave science next-generation detectors have to offer, but at a fraction of the cost.
The study, co-authored by the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav), coincides with an Astronomy Decadal Plan mid-term review by Australian Academy of Sciences where “NEMO” is identified as a priority goal.
“Gravitational-wave astronomy is reshaping our understanding of the Universe,” said one of the study’s lead authors OzGrav Chief Investigator Paul Lasky, from Monash University.
#DigitalPresentism #DTheoryofTime #TemporalMechanics
Temporal philosophy is a fascinating but eerily difficult topic. Correctly answering the philosophical questions and paradoxes of time paves the way to unlocking one of the last remaining mysteries of mind since our perception of time and consciousness, as you know, are simply inseparable. A new theory of time, Digital Presentism, comes from the triangulation of temporal physics, digital physics and experiential realism. This essay addresses the flaming questions in philosophy of time: “Is time fundamental or emergent?”, “How does time exist, if at all?”, “How can we update the current epistemic status of temporal ontology?” For starters, let’s recap what we’ve learned so far about physics of time. Here’s a quick summary: in Time Series essays, we dissected the nature of time through the prism of these 7 common misconceptions:
Female #Astrophysicist Helped Build 1st #AtomicBomb
Today marks 75 years since the 1st use of #nuclear weapons in #war-time, when the #US dropped the 1st atomic bomb on #Hiroshima, #Japan. One of the very few female #scientists who worked on the #ManhattanProject went on to become a researcher in high-energy #physics, #astrophysics, #cosmology, & diatomic molecular #spectroscopy.
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In the center of our galaxy, hundreds of stars closely orbit a supermassive black hole. Most of these stars have large enough orbits that their motion is described by Newtonian gravity and Kepler’s laws of motion. But a few orbit so closely that their orbits can only be accurately described by Einstein’s theory of general relativity. The star with the smallest orbit is known as S62. Its closest approach to the black hole has it moving more than 8% of light speed.
Our galaxy’s supermassive black hole is known as Sagittarius A* (SgrA•. It is a mass of about 4 million suns, and we know this because of the stars that orbit it. For decades, astronomers have tracked the motion of these stars. By calculating their orbits, we can determine the mass of SgrA*. In recent years, our observations have become so precise that we can measure more than the black hole’s mass. We can test whether our understanding of black holes is accurate.
The most studied star orbiting SgrA* is known as S2. It is a bright, blue giant star that orbits the black hole every 16 years. In 2018, S2 made its closest approach to the black hole, giving us a chance to observe an effect of relativity known as gravitational redshift. If you toss a ball up into the air, it slows down as it rises. If you shine a beam of light into the sky, the light doesn’t slow down, but gravity does take away some of its energy. As a result, a beam of light becomes redshifted as it climbs out of a gravitational well. This effect has been observed in the lab, but S2 gave us a chance to see it in the real world. Sure enough, at the close approach, the light of S2 shifted to the red just as predicted.
The end of the universe as we know it will not come with a bang. Most stars will slowly fizzle as their temperatures fade to zero.
“It will be a bit of a sad, lonely, cold place,” said theoretical physicist Matt Caplan, who added no one will be around to witness this long farewell happening in the far far future. Most believe all will be dark as the universe comes to an end. “It’s known as ‘heat death,’ where the universe will be mostly black holes and burned-out stars,” said Caplan, who imagined a slightly different picture when he calculated how some of these dead stars might change over the eons.
Punctuating the darkness could be silent fireworks—explosions of the remnants of stars that were never supposed to explode. New theoretical work by Caplan, an assistant professor of physics at Illinois State University, finds that many white dwarfs may explode in supernova in the distant far future, long after everything else in the universe has died and gone quiet.
This magnitude 7.1 earthquake started deep underground, in a gash on the Atlantic seafloor, a little more than 650 miles off the coast of Liberia, in western Africa. It rushed eastward and upward, then did an about-face and boomeranged back along the upper section of the fault at incredible speeds‑so fast it caused the geologic version of a sonic boom.
The ferocity of shaking from an earthquake is usually focused in the direction the temblor is traveling. But a boomerang quake, or a “back-propagating rupture” in scientific terms, may spread the intense shaking across a wider zone. It remains uncertain how common boomerang earthquakes are—and how many travel at such great speeds. But the new study, published today in the journal Nature Geoscience, is a major step toward untangling the complex physics behind these events and understanding their potential hazards.
“Studies like this help us understand how past earthquakes ruptured, how future earthquakes may rupture, and how that relates to the potential impact for faults near populated areas,” says Kasey Aderhold, a seismologist with the Incorporated Research Institutions for Seismology, via email.
Dozens of times over the last decade NASA scientists have launched laser beams at a reflector the size of a paperback novel about 240,000 miles (385,000 kilometers) away from Earth. They announced today, in collaboration with their French colleagues, that they received signal back for the first time, an encouraging result that could enhance laser experiments used to study the physics of the universe.
The reflector NASA scientists aimed for is mounted on the Lunar Reconnaissance Orbiter (LRO), a spacecraft that has been studying the moon from its orbit since 2009. One reason engineers placed the reflector on LRO was so it could serve as a pristine target to help test the reflecting power of panels left on the moon’s surface about 50 years ago. These older reflectors are returning a weak signal, which is making it harder to use them for science.
Scientists have been using reflectors on the moon since the Apollo era to learn more about our nearest neighbor. It’s a fairly straightforward experiment: Aim a beam of light at the reflector and clock the amount of time it takes for the light to come back. Decades of making this one measurement has led to major discoveries.
International team develops a new method to determine the origin of stardust in meteorites.
Analysis of meteorite content has been crucial in advancing our knowledge of the origin and evolution of our solar system. Some meteorites also contain grains of stardust. These grains predate the formation of our solar system and are now providing important insights into how the elements in the universe formed.
Working in collaboration with an international team, nuclear physicists at the U.S. Department of Energy’s (DOE’s) Argonne National Laboratory have made a key discovery related to the analysis of “presolar grains” found in some meteorites. This discovery has shed light on the nature of stellar explosions and the origin of chemical elements. It has also provided a new method for astronomical research.
