4474 - ATOMS - have wave particle duality?

 

-  4474   -  ATOMS  -  have wave particle duality?  -   Atoms squished closer together than ever before, revealing seemingly impossible “quantum effects”.   Using a  laser technique, scientists have squished pairs of atoms closer together than ever before, revealing some truly mind-boggling quantum effects.

-------------------------------  4474    -    ATOMS  -  have wave particle duality?

-

-   Scientists have two atoms interacting at an extremely close separation. They pushed layers of atoms 10 times closer together than in any previous experiment, resulting in odd quantum effects.

-

-    The squished two layers of ultracold magnetic atoms are within 50 nanometers of each other.  This is 10 times closer than in previous experiments.  It revealing bizarre quantum effects not seen before.

-

-   The extreme proximity of these atoms will allow researchers to study quantum interactions at this length scale for the first time and could lead to important advances in the development of superconductors and quantum computers.

-

-    Unusual quantum behaviors begin to emerge at ultracold temperatures as the atoms are forced to occupy their lowest possible energy state.  In the nanokelvin regime, there's a type of matter called “Bose Einstein condensate” in which all the particles behave like waves. They are basically quantum mechanical objects.

-

-    Interactions between these isolated systems are particularly important for understanding quantum phenomena such as superconductivity and superradiance. But the strength of these interactions typically depends on the separation distance, which can create practical problems for researchers studying these effects; their experiments are limited by how close they can get the atoms.

-

-    Most atoms used in cold experiments, such as the alkali metals, have to have contact in order to interact.    We're interested in 'dysprosium atoms' which are special in that they can interact with each other at long range through dipole-dipole interactions weak attractive forces between partial charges on adjacent atoms.   But although there's this long-range interaction, there are still some types of quantum phenomena that cannot be realized because this dipole interaction is so weak.

-

-     Bringing cold atoms into close proximity while maintaining control of their quantum states is a significant challenge, and until now, experimental limitations have prevented researchers from fully testing theoretical predictions about the effects of these quantum interactions.

-

-    For the first time ever, physicists have captured a clear image of individual atoms behaving like a wave.  The image shows sharp red dots of fluorescing atoms transforming into fuzzy blobs of wave packets and is a stunning demonstration of the idea that atoms exist as both particles and waves one of the cornerstones of quantum mechanics.

-

-    The wave nature of matter remains one of the most striking aspects of quantum mechanics. First proposed by the French physicist Louis de Broglie in 1924 and expanded upon by Erwin Schrödinger two years later, “wave particle duality” states that all quantum-sized objects, and therefore all matter, exists as both particles and waves at the same time.   Schrödinger's famous equation is typically interpreted by physicists as stating that atoms exist as packets of wave-like probability in space, which are then collapsed into discrete particles upon observation. While bafflingly counterintuitive, this bizarre property of the quantum world has been witnessed in numerous experiments.

-

-    To image this fuzzy duality, the physicists first cooled lithium atoms to near-absolute zero temperatures by bombarding them with photons, or light particles, from a laser to rob them of their momentum. Once the atoms were cooled, more lasers trapped them within an optical lattice as discrete packets.

-

-    With the atoms cooled and confined, the researchers periodically switched the optical lattice off and on expanding the atoms from a confined near-particle state to one resembling a wave, and then back.

-

-    A microscope camera recorded light emitted by atoms in the particle state at two different times, with atoms behaving like waves in between. By putting together many images, the authors built up the shape of this wave and observed how it expands with time, in perfect agreement with Schrödinger's equation

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-   This imaging method consists in turning back on the lattice to project each wave packet into a single well to turn them into a particle again. It is not a wave anymore. 

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-    The scientists say this image is just a simple demonstration. Their next step will be using it to study systems of strongly interacting atoms that are less well understood.  Studying such systems could improve our understanding of strange states of matter, such as those found in the core of extremely dense neutron stars, or the quark-gluon plasma that is believed to have existed shortly after the Big Bang. 

-

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May 20, 2024            ATOMS  -  have wave particle duality?              4474

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--------------------- ---  Monday, May 20, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4473 - OLDEST GALAXY - how do we know?

 

-  4473   -  OLDEST  GALAXY  -   how do we know?  The oldest stars in the universe were found hiding near the Milky Way's edge, and they may not be alone.  Astronomers reanalyzed the chemical composition of three stars in the Milky Way's halo and found that they are between 12 and 13 billion years old. They may have also been stolen from other galaxies.

-----------------------------------  4473    -    OLDEST  GALAXY  -  how do we know?

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-    Three alien stars circling the Milky Way could be some of the oldest ever found in the universe.  The ancient celestial objects may have been among the first to form after the Big Bang and were likely stolen by our galaxy during gravitational tugs-of-war billions of years ago.

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-    Researchers reanalyzed three previously observed stars each located around 30,000 light-years from Earth in the Milky Way's halo which is a massive cloud of stars that orbit beyond our galaxy's main galactic disk. The basic chemical composition of these stars suggests they are all between 12 and 13 billion years old, making them almost as old as the universe itself, which formed 13,800,000,000 years ago.

-

-    The trio's trajectories through the Milky Way also hint that these stars did not originate in our galaxy but were instead stolen from the periphery of some of the universe's oldest galaxies as the Milky Way brushed past them billions of years ago.

-

-   The group of 60 ultra-faint stars orbiting the Milky Way could be new type of galaxy never seen before.  The ancient balls of gas,  dubbed “Small Accreted Stellar System” (SASS) stars, are part of our cosmic family tree.

-

-   Normally, stars this old can only be studied by spying on galaxies from the other side of the known universe or by reverse-engineering ancient stars from their descendants. However, the discovery of ancient stars on our cosmic doorstep gives scientists a rare opportunity to study them directly, and researchers are now confident there are more stars like these toward our galaxy's edge.

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-    The new discovery came about from an MIT class.  They revealed the stellar trio, which each had an unusually low abundance of heavy metals such as iron, strontium and barium in its atmosphere.   One of the stars had around 10,000 times less iron than the sun.

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-    These heavy metals are forged over eons in the heart of stars, and are also found in the exteriors of younger stars, which suck up ingredients that were dispersed by exploding dead stars. The fact that this trio has few heavy metals, means they were formed before most other stars had exploded.

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-   The stars' compositions hinted that they did not originate in the Milky Way. But to confirm this, the students traced the orbital trajectories of the three stars and found that they all had a retrograde motion, meaning they are circling our galaxy's supermassive black hole in the opposite direction from a majority of the other stars.

-

-    Based on the stars' compositions, researchers also believe that each star was ripped from a different galaxy.   In a brief follow-up exercise they identified another 65 retrograde stars with similarly simple compositions. These stars will now be studied further to determine if they are also SASS stars.

-

-

May 18, 2024            OLDEST  GALAXY  -   how do we know?                4473

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--------------------- ---  Saturday, May 18, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4472 - KNOT THEORY ORBITS - what are they for?

 

-  4472   -  KNOT  THEORY  ORBITS  -   what are they for?  -    When a spacecraft arrives at its destination, it settles into an orbit for science operations. But after the primary mission is complete, there might be other interesting orbits where scientists would like to explore. Maneuvering to a different orbit requires fuel, limiting a spacecraft’s number of maneuvers.

---------------  4472    -   KNOT  THEORY  ORBITS  -   what are they for?

-   Researchers have discovered that some orbital paths allow for no-fuel orbital changes. But the figuring out these paths also are computationally expensive. “Knot theory” has been shown to find these pathways more easily, allowing the most fuel-efficient routes to be plotted. This is similar to how our GPS mapping software plots the most efficient routes for us here on Earth.

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-   In mathematics, “knot theory” is the study of closed curves in three dimensions. Think of it as looking at a knotted necklace or a tangle of fishing line, and figuring out how to untangle them in the most efficient manner.

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-   In the same way, a spacecraft’s path could be computed in a crowded planetary system, around Jupiter and all its moons, for example, where the best, simplest and least tangled route could be computed mathematically.

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-   Applications of knot theory to the detection of “heteroclinic connections” between “quasi-periodic orbits,” using knot theory to untangle complicated spacecraft routes would decrease the amount of computer power in plotting out changes in spacecraft orbits.

-

-   Previously, when  NASA wanted to plot a route, their calculations relied on either brute force or guesswork.   These new techniques neatly reveal all possible routes a spacecraft could take from A to B, as long as both orbits share a common energy level.  This new process makes the task of planning missions much simpler.

-

-   Spacecraft navigation is complicated by the fact that nothing in space is a fixed position. Navigators must meet the challenges of calculating the exact speeds and orientations of a rotating Earth, a rotating target destination, as well as a moving spacecraft, while all are simultaneously traveling in their own orbits around the Sun.

-

-    Since fuel is a limited resource for space missions, it would be beneficial to require the least amount of fuel possible in making any changes to the course of a spacecraft in orbit. Spacecraft navigators use heteroclinic orbits, which are paths that allow a spacecraft to travel from one orbit to another using the most efficient amount of fuel,  or sometimes no fuel at all.

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-     When a spacecraft arrives at its destination, it settles into an orbit for science operations. But after the primary mission is complete, there might be other interesting orbits where scientists would like to explore. Maneuvering to a different orbit requires fuel, limiting a spacecraft’s number of maneuvers.   But this usually takes a large amount of computer power or a lot of time to figure out. 

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-   By using “knot theory”, they have developed “a method of robustly detecting “heteroclinic connections,” to quickly generate rough trajectories which can then be refined. This gives spacecraft navigators a full list of all possible routes from a designated orbit, and the one that best fits the mission can be chosen.

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-    The researchers tested their technique on various planetary systems, including the Moon, and the Galilean moons of Jupiter.  Spurred on by NASA’s Artemis program, the new Moon race is inspiring mission designers around the world to research fuel-efficient routes that can better and more efficiently explore the vicinity of the Moon.

-

-      Not only does this technique make that cumbersome task more straightforward, but it can also be applied to other planetary systems, such as the icy moons of Saturn and Jupiter.

-

-

May 16, 2024               KNOT  THEORY  ORBITS  -   what are they for?           4472

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--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Friday, May 17, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4471 - EXPANDING UNIVERSE - is it flat?

 

-  4471   -  EXPANDING  UNIVERSE  -    is it flat?   -    Our cosmic model of the universe, based on quantum mechanics and general relativity, deals with the geometry of the universe as influenced by matter and energy, which for most purposes is considered to be “flat”,  that is the same in all directions..

---------------  4471    -   EXPANDING  UNIVERSE  -    is it flat?

-    The topology of the universe itself: Is it infinite, does it have loops, etc.   This research is done as a part of the COMPACT collaboration consisting of an international team of scientists.

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-   There is growing evidence that the universe is not 'statistically isotropic,' i.e. that physics is the same in all directions. Topology is a very natural way for anisotropy to creep into our universe.

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-   “Cosmic microwave background”, CMB,  is a type of radiation belonging to the microwave spectrum. Predicted in the 1940s as a remnant of the Big Bang, it was detected in 1965 by accident.

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-   After the Big Bang, which is how the present universe came into existence, there was nothing but a soup of fundamental particles and gases at extremely high temperatures and pressures, often referred to as a “primordial soup”.

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-    As the universe expanded, it also cooled down. This led to the fundamental particles combining to form atoms. Up until this point, photons were interacting with these fundamental particles and scattering, not allowing them to travel freely. But once atoms started to form, photons traveled more freely.  This happened around 380,000 years after the Big Bang.

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-   This marked the propagation of CMB, which is considered an 'afterglow' of the Big Bang. It holds important information about the early universe and the subsequent processes that led to the formation of large-scale structures like stars and galaxies.

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-   CMB is present everywhere and, for the most part, is uniform in temperature. However, there are small fluctuations and anomalies in CMB data that haven't been explained.

-

-    Topology is a branch of mathematics that deals with the shape and structure of objects. The rules of topology are quite different from the rules of geometry. While geometry and topology are distinct concepts, geometry influences topology.

-

-   Geometry defines how space is curved (spacetime is considered flat at small scales), and topology defines the overall connectivity of space.  If we were to have “flat space”, we can't have topologies where space curves inwards or have loops. This means to travel between two points, we would have to take a straight line path without any detours or loops.

-

-   The universe may be like an old-time video game, where leaving the right side of the screen would see you popping in from the left, so you can get back where you started by a straight-line path. This is called being multiply connected.

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-   Essentially, the straight-line path suggests that despite the appearance of continuous motion, the underlying topology of space allows for unexpected connectivity, where what seems like a linear trajectory may actually loop back on itself.

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-   If the universe were to be 'multiply connected'  we would observe matched temperature circles. This is because light traveling from a source (like a star) could travel along two different paths and arrive at the observer (Earth) from two directions.

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-   This leaves behind similar temperature fluctuations on a CMB map (or heat map), resulting in matched temperature circles. However, there has been no evidence suggesting the presence of these matched temperature circles.

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-    The absence of matched temperature circles in the CMB data suggests that if nontrivial topology exists, the loops passing through our location (Earth) must be relatively small.

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-    If the CMB anomalies are due to cosmic topology, then the length of the shortest loops through us should not be more than about 20–30% longer than the diameter of the last scattering surface, a sphere with a radius equal to the distance that light has traveled in the history of the universe.

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-    The researchers propose additional ways for detecting such topology in the future.  Alterations in the statistical patterns of temperature fluctuations in CMB data as well as in the large-scale structure of the universe would come to light if nontrivial topology were present.

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-   But, these detections require enormous computational power and the researchers suggest the use of machine learning algorithms to speed up calculations and mining CMB data to detect this topology.

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-     Hopefully, we will someday detect cosmic topology and thereby understand the origin of the anisotropy of our universe and get a glimpse into the processes responsible for the original emergence of our universe.

-

-   The study also highlights that even in the absence of explicitly matched circles, the presence of statistical anisotropy (or anomalies) in the CMB indicates the potential existence of detectable information about the universe's structure and topology.

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May 17, 2024               EXPANDING  UNIVERSE  -    is it flat?                    4471

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Friday, May 17, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4470 - NUCLEAR ENERGY - will it work?

 

-  4470   -     NUCLEAR  ENERGY  -   will it work?  In December 2022, after more than a decade of effort and frustration, scientists at the US National Ignition Facility (NIF) announced that they had set a world record by producing a fusion reaction that released more energy than it consumed — a phenomenon known as “ignition”.

---------------------------------  4470    -   NUCLEAR  ENERGY  -   will it work? 

-    The stadium-sized laser facility, housed at the Lawrence Livermore National Laboratory (LLNL) in California, has achieved its goal of ignition in four out of its last six attempts, creating a reaction that generates pressures and temperatures greater than those that occur inside the Sun.

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-    The NIF was designed not as a power plant, but as a facility to recreate and study the reactions that occur during thermonuclear detonations after the United States halted underground weapons testing in 1992. The higher fusion yields are already being used to advance nuclear-weapons research, and have also fueled enthusiasm about fusion as a limitless source of clean energy.

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-     The NIF works by firing 192 laser beams at a frozen pellet of the hydrogen isotopes deuterium and tritium that is housed in a diamond capsule suspended inside a gold cylinder. The resulting implosion causes the isotopes to fuse, creating helium and copious quantities of energy.  December, 2022, those fusion reactions for the first time generated more energy , roughly 54% more, than the laser beams delivered to the target.

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-   The facility set a new record when its beams delivered the same amount of energy to the target, 2.05 megajoules, but, this time, the implosion generated 3.88 megajoules of fusion energy, an 89% increase over the input energy.

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-    Tiny variations in the laser pulses or minor defects in the diamond capsule can still allow energy to escape, making for an imperfect implosion, but the scientists now better understand the main variables at play and how to manipulate them.  We can still get more than a megajoule of fusion energy.

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-   It’s a long way from there to providing fusion energy to the power grid, however, and the NIF, although currently home to the world’s largest laser, is not well-suited for that task. The facility’s laser system is enormously inefficient, and more than 99% of the energy that goes into a single ignition attempt is lost before it can reach the target.

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-    Developing more efficient laser systems is one goal of the DOE’s new inertial-fusion-energy research program.   So far, most government investments in fusion-energy research have gone towards devices known as “tokamaks”, which use magnetic fields inside a doughnut-shaped ‘torus’ to confine fusion reactions.

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-   NIF latest series of experiments features a 7% boost in laser energy, which should, in theory, lead to even larger yields. The first experiment in this series was one of the successful ignitions  although it didn’t break the record, an input of 2.2 megajoules of laser energy yielded an output of 3.4 megajoules of fusion energy.

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-    Costing US$3.5 billion and housed at Lawrence Livermore National Laboratory in California, the NIF was designed to bolster nuclear-weapons science. Advances there could also help to develop nuclear fusion as a safe, clean and almost limitless source of energy.

-

-    The NIF’s ignition had been a decade behind schedule, and some feared that it was beyond reach.    The facility’s 192 laser beams delivered 2.05 megajoules of energy to a frozen pellet of the hydrogen isotopes deuterium and tritium, suspended in a gold cylinder. The resulting implosion caused the isotopes to release energy as they fused into helium, generating temperatures six times hotter than the core of the Sun. The reactions produced a record 3.88 megajoules of fusion energy.

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-   Other facilities have generated more fusion energy over longer periods of time, most notably in tokamak reactors, which use powerful magnetic fields to confine fusion reactions. This is the technology under development by the $22-billion ITER project, an international collaboration near Saint-Paul-lez-Durance, France. Before the NIF’s achievement, however, no lab had produced a fusion reaction that generated more energy than it had consumed.

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-   January 2024, pioneering nuclear-fusion reactor shuts down: what scientists will learn

The decommissioning of the Joint European Torus near Oxford, UK.   Scientists have begun to decommission one of the world’s foremost nuclear-fusion reactors, 40 years after it began operations. Researchers will study the 17-year process of dismantling the Joint European Torus (JET) near Oxford, UK, in unprecedented detail and use the knowledge to make sure future fusion power plants are safe and financially viable.

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-    Harnessing the fusion of atoms, the process that powers the Sun, could provide humans with a near-limitless source of clean energy. Creating the conditions for fusion in power plants and exploiting the resulting energy will require complex engineering that hasn’t yet been proved, meaning that commercial fusion power is still many decades away.

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-    But researchers are pushing ahead with designs for the first commercial reactors as excitement about fusion grows. In 2022, JET smashed the record for the amount of energy created through fusion. And the US National Ignition Facility (NIF) in Livermore, California, the flagship US fusion facility, now routinely generates more energy from a fusion reaction than was put in.

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-    The NIF calculations do not include the entire energy requirements of running the facility, which fusion plants would need to exceed to truly ‘break even’, but physicists have celebrated the milestones.

-

-    JET is important because the facility is a test bed for ITER, a US$22-billion fusion reactor being built near Saint-Paul-lez-Durance, France, which aims to prove the feasibility of fusion as an energy source in the 2030s. Jet has informed decisions on what materials to build ITER with and the fuel it will use, and it has been crucial to predicting how the bigger experiment will behave.

-

-    The thorniest part of decommissioning the JET site will be dealing with its radioactive components. The process of fusion does not leave waste that is radioactive for millennia, unlike nuclear fission, which powers today’s nuclear reactors. But JET is among the tiny number of experiments worldwide that have used significant amounts of tritium, a radioactive isotope of hydrogen.

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-    Tritium, which will be used as a fuel in future fusion plants including ITER, has a half-life of 12.3 years, and its radiation, alongside the high-energy particles released during fusion, can leave components radioactive for decades.

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-    Decommissioning a fusion experiment doesn’t have to mean “bulldozing everything within sight into rubble and not letting anyone near the site for ages.   Instead, engineers’ priorities will be to reuse and recycle parts. This will include removing tritium where possible.  This reduces radioactivity and allows tritium to be reused as fuel.

-

-    JET and ITER are both ‘tokamak’ reactors, which confine gas in their doughnut-shaped cavities. JET uses magnets to squeeze a plasma of hydrogen isotopes, ten times hotter than the Sun, until the nuclei fuse.

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-    The last time the fusion community decommissioned a comparable device was in 1997, when the Tokamak Fusion Test Reactor at Princeton Plasma Physics Laboratory in New Jersey shut down. Many parts, such as the equipment for injecting hot beams of gas into the reactor, were reused, as was the site itself. But the tokamak had to be filled with concrete, cut up and buried.

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-     JET engineers will use a newly refurbished robotic system to remove sample tiles for analysis. And they will use remotely operated lasers to measure how much tritium is in samples that remain inside the experiment. Like hydrogen, tritium is a gas that “penetrates all materials, and we need to know exactly how deep the tritium has penetrated.

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-     To extract the tritium from metals, engineers will heat the components in a furnace before capturing the released isotope in water. Tritium can be removed from water and turned back into fuel; leftover materials become low-level waste, the same classification given to radioactive waste made by universities and hospitals.

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-    Some unaffected parts of JET, such as diagnostic and test equipment, have already been repurposed in fusion experiments in France, Italy and Canada.   In its final experiments last Decembers scientists explored inverting the shape of the plasma in a way that might more readily confine heat.

-

-    They also deliberately damaged the facility by sending a high-energy beam of ‘runaway’ electrons — produced when plasma is disrupted — careering into the reactor’s inner wall.  Analysis of the damage, after the machine is opened up, will provide useful data to test the detailed predictions.

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May 17, 2024              NUCLEAR  ENERGY  -   will it work?                      4470

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Friday, May 17, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4469 - NORTHERN LIGHTS - May, 2024

 

-  4469   -    NORTHERN  LIGHTS  -     May 2024,  a huge solar flare sent a wave of energetic particles from the sun surging out through space.   The wave reached Earth, and people around the world enjoyed the sight of unusually vivid aurora in both hemispheres.  While the aurora is normally only visible close to the poles, this was spotted as far south as Hawaii in the northern hemisphere, and as far north as Mackay in the south.

-----------------------  4469    -   NORTHERN  LIGHTS  -   May, 2024

-   This spectacular spike in auroral activity appears because the sun is approaching the peak of its 11-year sunspot cycle, and periods of intense aurora are likely to return over the next year.

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-     What makes the glow, and the different colors?    It is all about atoms, how they get excited and how they relax.

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-   The auroras are caused by charged subatomic particles (mostly electrons) smashing into Earth's atmosphere. These are emitted from the sun all the time, but there are more during times of greater solar activity.

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-    Most of our atmosphere is protected from the influx of charged particles by Earth's magnetic field. But near the poles, they can sneak in and wreak havoc.

-

-    Earth's atmosphere is about 20% oxygen and 80% nitrogen, with some trace amounts of other things like water, carbon dioxide (0.04%) and argon.

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-   When high-speed electrons smash into oxygen molecules in the upper atmosphere, they split the oxygen molecules (O₂) into individual atoms. Ultraviolet light from the sun does this too, and the oxygen atoms generated can react with O₂ molecules to produce ozone (O₃), the molecule that protects us from harmful UV radiation.

-

-   But, in the case of the aurora, the oxygen atoms generated are in an excited state. This means the atoms' electrons are arranged in an unstable way that can "relax" by giving off energy in the form of light.

-

-   As you see in 4^th of July fireworks, atoms of different elements produce different colors of light when they are energized.   Copper atoms give a blue light, barium is green, and sodium atoms produce a yellow–orange color that you may also have seen in older street lamps. These emissions are "allowed" by the rules of quantum mechanics, which means they happen very quickly.

-

-   When a sodium atom is in an excited state it only stays there for around 17 billionths of a second before firing out a yellow–orange photon.   But, in the aurora, many of the oxygen atoms are created in excited states with no "allowed" ways to relax by emitting light. Nature finds a way.

-

-   The green light that dominates the aurora is emitted by oxygen atoms relaxing from a state called "¹S" to a state called "¹D." This is a relatively slow process, which on average takes almost a whole second.

-

-   In fact, this transition is so slow it won't usually happen at the kind of air pressure we see at ground level, because the excited atom will have lost energy by bumping into another atom before it has a chance to send out a green photon. But in the atmosphere's upper reaches, where there is lower air pressure and therefore fewer oxygen molecules, they have more time before bumping into one another and therefore have a chance to release a photon.

-

-   For this reason, it took scientists a long time to figure out that the green light of the aurora was coming from oxygen atoms. The yellow–orange glow of sodium was known in the 1860s, but it wasn't until the 1920s that Canadian scientists figured out the auroral green was due to oxygen.

-

-    The green light comes from a so-called "forbidden" transition, which happens when an electron in the oxygen atom executes an unlikely leap from one orbital pattern to another. (“Forbidden transitions” are much less probable than allowed ones, which means they take longer to occur.)

-

-   However, even after emitting that green photon, the oxygen atom finds itself in yet another excited state with no allowed relaxation. The only escape is via another forbidden transition, from the ¹D to the ³P state, which emits red light.

-

-    This transition is even more forbidden, and the ¹D state has to survive for about about two minutes before it can finally break the rules and give off red light. Because it takes so long, the red light only appears at high altitudes, where the collisions with other atoms and molecules are scarce.

-

-   Also, because there is such a small amount of oxygen up there, the red light tends to appear only in intense auroras.   This is why the red light appears above the green. While they both originate in forbidden relaxations of oxygen atoms, the red light is emitted much more slowly and has a higher chance of being extinguished by collisions with other atoms at lower altitudes.

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-   While green is the most common color to see in the aurora, and red the second most common, there are also other colors. In particular, ionized nitrogen molecules (N₂⁺, which are missing one electron and have a positive electrical charge), can emit blue and red light. This can produce a magenta hue at low altitudes.

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-   All these colors are visible to the naked eye if the aurora is bright enough. However, they show up with more intensity in the camera lens.

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-   There are two reasons for this. First, cameras have the benefit of a long exposure, which means they can spend more time collecting light to produce an image than our eyes can. As a result, they can make a picture in dimmer conditions.

-

-   The second is that the color sensors in our eyes don't work very well in the dark, so we tend to see in black and white in low light conditions. Cameras don't have this limitation.

-

-   When the aurora is bright enough, the colors are clearly visible to the naked eye.

-

-  When a huge solar flare sent a wave of energetic particles from the sun surging out through space reached Earth, and people around the world enjoyed the sight of unusually vivid aurora in both hemispheres. 

-

-    This spectacular spike in auroral activity appears to have ended, but the sun is approaching the peak of its 11-year sunspot cycle, and periods of intense aurora are likely to return over the next year.

-

-   Cameras have the benefit of a long exposure, which means they can spend more time collecting light to produce an image than our eyes can. As a result, they can make a picture in dimmer conditions.

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-    We tend to see in black and white in low light conditions. Cameras don't have this limitation.  But, when the aurora is bright enough, the colors are clearly visible to the naked eye.

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May 14, 2024               NORTHERN  LIGHTS  -   May, 2024                       4469

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--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Wednesday, May 15, 2024  ---------------------------------

 

 

 

 

 

           

 

 

STAR EXPLOSIONS - how astronomers learn?

 

-  4468   -  STAR  EXPLOSIONS  -  how astronomers learn?   The tumultuous massive star, in the final year or so of its life, ejected large amounts of matter into space before going supernova.   This massive star that exploded in the Pinwheel Galaxy in May appears to have unexpectedly lost one sun's worth of ejected mass during the final years of its life before going supernova.

------------------------------  4468    -  STAR  EXPLOSIONS  -  how astronomers learn?

-   On the night of May 19, 2024, Japanese amateur astronomer was conducting his regular supernova sweep using  telescopes based in three remote observatories dotted around the country. They were located in  Yamagata, Okayama and on the island of Shikoku.

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-    When amateur astronomers spotted the light of “SN 2023ixf” they immediately knew they had found something special. That’s because this star  had exploded in the nearby Pinwheel Galaxy (Messier 101), which is just 20 million light-years away in the constellation of Ursa Major, the Great Bear. Cosmically speaking, that's pretty close.

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-    Soon enough, amateur astronomers around the world started gazing at SN 2023ixf because the Pinwheel in general is a popular galaxy to observe. However, haste is  key when it comes to supernova observations: Astronomers are keen to understand exactly what is happening in the moments immediately after a star goes supernova. Yet all too often, a supernova is spotted several days after the explosion took place, so they don’t get to see its earliest stages.

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-    Considering how close, relatively speaking, SN 2023ixf was to us and how early it was identified, it was a prime candidate for close study.   The race to decode a supernova with several professional telescopes at their disposal including the 6.5-meter Multi Mirror Telescope (MMT) at the Fred Lawrence Whipple Observatory on Mount Hopkins in Arizona. They measured the supernova's light spectrum, and how that light changed over the coming days and weeks. When plotted on a graph, this kind of data forms a "light curve."

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-    The spectrum from “SN 2023ixf” showed that it was a type II supernova which is a category of supernova explosion involving a star with more than eight times the mass of the sun. In the case of SN 2023ixf, searches in archival images of the Pinwheel suggested the exploded star may have had a mass between 8 and 10 times that of our sun.

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-    The spectrum was also very red, indicating the presence of lots of dust near the supernova that absorbed bluer wavelengths but let redder wavelengths pass. This was all fairly typical, but what was especially extraordinary was the shape of the light curve.

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-   Normally, a type II supernova experiences what astronomers call a 'shock breakout' very early in the supernova's evolution, as the blast wave expands outwards from the interior of the star and breaks through the star's surface. Yet a bump in the light curve from the usual flash of light stemming from this shock breakout was missing. It  didn’t turn up for several days. Was this a supernova in slow motion, or was something else?

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-    The delayed shock breakout is direct evidence for the presence of dense material from recent mass loss.  These observations revealed a significant and unexpected amount of mass loss, close to the mass of the sun, in the final year prior to explosion.

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-    The unstable star was puffing off huge amounts of material from its surface. This creates a dusty cloud of ejected stellar material all around the doomed star. The supernova shock wave therefore not only has to break out through the star, blowing it apart, but also has to pass through all this ejected material before it becomes visible.  This took several days for this supernova.

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-    Massive stars often shed mass like the star Betelgeuse’s shenanigans over late 2019 and early 2020, when it belched out a cloud of matter with ten times the mass of Earth’s moon that blocked some of Betelgeuse’s light, causing it to appear dim.

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-    However, Betelgeuse isn’t ready to go supernova just yet, and by the time it does, the ejected cloud will have moved far enough away from the star for the shock breakout to be immediately visible. In the case of SN 2023ixf, the ejected material was still very close to the star, meaning that it had only recently been ejected, and astronomers were not expecting that.

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-   Submillimeter Array on Mauna Kea in Hawaii sees the universe at long wavelengths. It was able to see the collision between the supernova shockwave and the circumstellar cloud.  The only way to understand how massive stars behave in the final years of their lives up to the point of explosion is to discover supernovae when they are very young, and preferably nearby, and then to study them across multiple wavelengths.  Using both optical and millimeter telescopes we effectively turned SN 2023ixf into a time machine to reconstruct what its progenitor star was doing up to the moment of its death.

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-    We can think of an evolved massive star as being like an onion, with different layers. Each layer is made from a different element, produced by sequential nuclear burning in the star's respective layers as the stellar object ages and its core contracts and grows hotter.

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-    The outermost layer is hydrogen, then you get to helium. Then, you go through carbon, oxygen, neon and magnesium in succession until you reach all the way to silicon in the core. That silicon is able to undergo nuclear fusion reactions to form iron, and this is where nuclear fusion in a massive star’s core stops because iron requires more energy to be put into the reaction than comes out of it, which is not efficient for the star.

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-  Thus the core switches off, the star collapses onto it and then rebounds and explodes outwards.  One possibility is that the final stages of burning high-mass elements inside the star, such as silicon (which is used up in the space of about a day), is disruptive, causing pulses of energy that shudder through the star and lift material off its surface.

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-    What the story of SN 2023ixf does tell us is, at the very least, that despite all the professional surveys hunting for transient objects like supernovas, amateur astronomers can still make a difference.

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May 13, 2024          STAR  EXPLOSIONS  -  how astronomers learn?           4468

------------------------------------------------------------------------------------------                                                                                                                       

--------  Comments appreciated and Pass it on to whomever is interested. ---

---   Some reviews are at:  --------------     http://jdetrick.blogspot.com ----- 

--  email feedback, corrections, request for copies or Index of all reviews

---  to:  ------    jamesdetrick@comcast.net  ------  “Jim Detrick”  -----------

--------------------- ---  Wednesday, May 15, 2024  ---------------------------------