4585 - SEA LEVEL RISING - how fast are predictions?

 

-  4585 -   SEA  LEVEL  RISING  -   how fast are predictions?  -   Satellites are tracking the ongoing sea level rise swamping Pacific Island nations.  The small island nations of the South Pacific are facing the harsh reality of sea level rise. Within 50 years they will be swamped by rising seas linked to climate change.

----------------------------------   4585  -  SEA  LEVEL  RISING  -   how fast are predictions?

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-   Satellites were used to predict rising ocean levels. According to their data, Pacific nations such as Tuvalu, Kiribati, and Fiji will experience an increased rise in sea levels. That threatens the homes and livelihoods of millions of people.

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-    The team's job is to improve our understanding of sea-level change over time. The members analyzed the South Pacific threat at the request of the affected nations and coordinated with the U.S. State Department. They created high-resolution maps showing which areas of different Pacific Island nations would be vulnerable to high-tide flooding. The maps outline the potential for flooding. In addition, they take into account different greenhouse gas emissions scenarios, ranging from best-case to business-as-usual to worst-case.

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-    A combination of space-based and ground-based measurements can yield more precise sea level rise projections. That should give an improved understanding of the impacts on countries in the Pacific. Still, it’s one thing to create predictive models and share that data with affected nations. It’s quite another to actually experience the gradual rise of sea levels as the people of the South Pacific islands and other low-lying areas along the world’s coastlines.

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-   The data being used comes from measurements by satellites, shipboard and airborne instruments, and supercomputer analysis. The result is a more precise assessment of sea levels and their rise and fall over time. Using this data.

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-    Sea level rise is based on a number of factors, including melting of glaciers and other ice packs and ocean warming related to pumping greenhouse gases into the atmosphere. Based on the data from NASA satellites, the Pacific Islands most at risk will see at least a 15-cm sea level rise by 2050. That’s nearly an order of magnitude higher than all Pacific Island nations experience now.

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-    To give you an idea of how that will affect specific places, Tuvalu currently sees less than five high tide flood days per year. By 2050, residents will experience at least 25 flood days each year. Kiribati will see 65 flood events. The maps produced by the NASA-led team for these and other islands should help these nations plan for future flood mitigation efforts.

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-    Not every area in the world experiences the same amount of flooding. Local conditions and coastlines contribute to area-specific floods. The impact that 15 centimeters of sea level rise will have varies from country to country. Some regions will see nuisance flooding several times a year in flat or low-lying areas. Others face inundation for longer periods with higher amounts of water.

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-    The impacts of sea level rise will vary from place to place and depend on topography, shapes of coastlines, and other factors. Better predictive tools will help scientists understand where sea levels will rise the most and share that information with affected populations. Researchers would like to combine satellite data on ocean levels with ground-based measurements of sea levels at specific points, as well as with better land elevation information.

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-    The combination of space-based and ground-based measurements can yield more precise sea level rise projections and an improved understanding of the impacts on countries in the Pacific. Still, it’s one thing to create predictive models and share that data with affected nations. It’s quite another to actually experience the gradual rise of sea levels as the people of the South Pacific islands and other low-lying areas along the world’s coastlines.

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-    People in these regions experience different types of threats from the oceans. Flooding can occur when the ocean inundates the land during tropical storms, typhoons, and hurricanes. It can also happen during exceptionally high tides, called king tides.

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-   Another avenue for flooding is saltwater intrusion into underground areas. That pushes the water table to the surface.

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-   Places like Tuvalu will benefit from better tools to predict sea level rise. It’s not just a matter of preventing flooding, but one of a nation’s survival now and over the next few decades.  The future of the young people of Tuvalu is already at stake.  Climate change is more than an environmental crisis. It is about justice, survival for nations like Tuvalu, and global responsibility.

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October 23, 2024        SEA  LEVEL  RISING  -   how fast are predictions?             4585

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--------------------- ---  Thursday, October 24, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4584 - HUMANS - the oldest found around the world?

 

-  4584 -  HUMANS  -  the oldest found around the world?  -  An 86,000-year-old human bone found in Laos cave hints at 'failed population' from prehistory.   The discovery of a skull and shin bone fragment in a cave in Laos pushes back the earliest known date of Homo sapiens in Southeast Asia.

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-----------------------   4584  -  HUMANS  -  the oldest found around the world?

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-   Homo sapiens arrived in Southeast Asia as early as 86,000 years ago, a human shin bone fragment found deep within a cave in Laos reveals.   The cave of Tam Pà Ling, or “Cave of the Monkeys”, which sits at around 3,840 feet above sea level on a mountain in northern Laos. Human bone fragments previously found in the cave were 70,000 years old, making them some of the earliest evidence of humans in this area of the world. This discovery prompted archaeologists to dig deeper.

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-   Finding two new bones,  fragments of the front of a skull and a shin bone.  These bones were likely washed into the Tam Pà Ling cave during a monsoon. Even though the bones were fractured and incomplete, the researchers were able to compare their dimensions and shape with other bones from early humans, finding that they most closely matched Homo sapiens rather than other archaic humans, such as Homo erectus, Neandertals or Denisovans.

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-    The researchers used luminescence dating of nearby sediments and uranium-series dating of mammalian teeth from the same layers to produce an age range for the human remains. Luminescence dating is a technique that measures the last time crystalline materials, such as stones, were exposed to sunlight or heat, while U-series dating is a radiometric technique that, similar to carbon-14 dating, measures the decay of uranium over time into thorium, radium and lead. The skull, they estimated, was up to 73,000 years old, and the shin bone dates back as far as 86,000 years ago.

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-     Debates about human colonization of Southeast Asia have taken place for decades as researchers have attempted to understand how and when humans crossed straits and seas to eventually end up in Australia. Tam Pà Ling is therefore a prime place to ask some of these questions about migration, since mainland southeast Asia really sits at the crossroads of East Asia and island SE Asia/Australia.

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-   The “Cave of the Monkeys”, sits at around 3,840 feet above sea level in northern Laos.

While the genetic and stone tool evidence amassed to date strongly supports a single, rapid dispersal of Homo sapiens from Africa some time after 60,000 years ago, studies such as this one are producing evidence for earlier migrations, many of which may have been dead ends.

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-   Perhaps this was a group that dispersed to Southeast Asia and died out before they were able to contribute genes to today's human gene pool.    These 'failed' populations interesting to add, so that we aren't just looking at the 'successful' ones that 'made it'.

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-    No stone tools or other clues about these humans' lifestyles have been found in Tam Pà Ling. But archaeologists working on the prehistory of Asia have long suspected that, even before 65,000 years ago, ancient humans were capable of reaching islands and making sea crossings to populate seemingly remote parts of the world.

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-   From when our ancient relatives began walking on two feet to the first known medical amputation on Homo sapiens, here's what we learned in 2022 about our human ancestors.

Humans are exceptionally diverse, but we all have something in common: We're Homo sapiens, and we share a common ancestor. But the story of how we arose, spread around the globe and acted along the way is still emerging as scientists find new clues.

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-    The discovery of a 1.5 million-year-old vertebra from Israel hints that early humans migrated out of Africa not in one but multiple waves. It's unknown which human species the bone belongs to: Although there is just one human species today, there used to be multiple species in the genus Homo.

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-   Previously, researchers found evidence that a now-extinct human species left Africa for Eurasia at least 1.8 million years ago, and there's evidence that modern humans left Africa as early as 270,000 years ago. Now, the discovery of this vertebra (the oldest human bone ever found in Israel), reveals that humans likely left the African continent multiple times.

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-    Researchers have attempted to do a family tree for all of humanity to see how everyone is related. In their investigation, the scientists looked at thousands of genome sequences from 215 populations from around the globe, including from ancient and modern humans, as well as our ancient human relatives.

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-    A computer algorithm looked at genetic variations among genomes, enabling the team to see who was descended from and related to whom. After approximating where these ancestors lived, the researchers created a map for this gargantuan family tree. As one might expect, it all goes back to Africa.

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-   Bipedalism was common among the earliest known species of humankind, not only on the ground but also in trees. It coexisted with other types of movement in a tree environment, including quadrupedal (four-legged) movement using firm hand grips, clearly differing from that of gorillas and chimpanzees, which use the back of their phalanges for support ("knuckle walking").

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-    Walking on our own two feet is quite a feat, one that was pulled off by our ancestors as far back as 7 million years ago, researchers found. The discovery was made when researchers studied a thigh bone and a pair of forearm bones from the 7 million-year-old “Sahelanthropus tchadensis”, which may be the oldest-known hominin.  This is a relative of humans dating from the period after our ancestors split off from those of modern apes. It appears that S. tchadensis, who was found in Chad, both walked on two feet and also climbed trees.

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-    A 1.4 million-year-old jawbone found in Spain may belong to the oldest-known human relative in Europe. The upper jawbone has features that showcase the evolutionary pattern of the human face, suggesting that it's closer to modern humans than it is to ape-like primates. It's possible that this jawbone belongs to Homo antecessor, whose position in the human family tree is controversial but may be a cousin of modern humans and Neanderthals (Homo neanderthalensis). Until this finding, the oldest-known human relative in Europe dated to 1.2 million years ago.

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-    Four different “Australopithecus crania” that were found in the Sterkfontein caves, South Africa. The “Sterkfontein cave” fill containing this and other Australopithecus fossils was dated to 3.4 to 3.6 million years ago, far older than previously thought. The new date overturns the long-held belief that South African Australopithecus is a younger offshoot of East African Australopithecus afarensis.

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-   A new analysis of old, human-like bones revealed they may be more than 1 million years older than previously thought, researchers found. The new date range, 3.4 million to 3.7 million years old, of these Australopithecus bones from Sterkfontein, South Africa, improves the odds that this species gave rise to humans.

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-    The fossils would predate the iconic "Lucy" fossil which is a 3.2 million-year-old “Australopithecus afarensis” in East Africa whose species was a prime contender for being our direct ancestor.

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-    Researchers in Laos uncovered an ancient molar that may have belonged to a Denisovan girl who lived up to 164,000 years ago. Not much is known about the Denisovans, but along with Neanderthals, they're the closest extinct relatives of modern humans.

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-     Precious few fossils exist from these humans, who are named after Denisova Cave in southern Siberia where their first-known remains were found. Over the years, their bones have also been found in China. Now, the discovery of a 164,000-year-old tooth from Laos reveals that the Denisovans also lived in Southeast Asia at low altitudes where it was warm and humid.

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-    The oldest medical amputation on record is prehistoric, dating to a Stone Age patient who lost a leg in Borneo 31,000 years ago. A skilled surgeon cut off a child's leg, whose stump showed signs of healing. That child hunter-gatherer went on to live for another six to nine years after the surgery, according to an analysis of the individual's tooth enamel. Previously, the oldest medical amputation on record dated to 7,000 years ago.

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-    A massive icy barrier that stood up to 300 stories tall may have blocked the way of the people who left Eurasia to become the first Americans. The existence of this frigid obstacle suggests that these people didn't cross the Bering land bridge from Asia to America on foot, but rather sailed on boats along the coast.

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-   Researchers came to this conclusion after analyzing 64 geological samples from six locations across the ancient bridge area. They found that the ice-free corridor didn't completely open until about 13,800 years ago.  This is a confusing date given that other evidence suggests the first Americans arrived much earlier and that the Clovis culture found in New Mexico was already established at that time.

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-   Little kids today love running around and splashing in muddy puddles, and children from the last ice age were no different. Researchers found about 30 footprints from young children on top of track marks left by a giant sloth, one of the big creatures that once lived in the Americas. These 11,000-year-old prints, found in what is now New Mexico, suggest that the sloth's prints had become muddy, creating a prime spot for jumping.

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-     Thousands of years ago, ancient humans and animals left their footprints on a coastal stretch in England that researchers are calling a superhighway. Some of the tracks are about 8,500 years old, just a few thousand years after the last ice age ended. In addition to humans, researchers found the tracks of aurochs (an extinct ox species), red deer, wild boars, wolves, lynx and cranes. Based on the configuration of some of the human footprints, it's possible that these ancient people were hunting the species of animals whose prints are also preserved.

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October 24, 2024        HUMANS  -  the oldest found around the world?                 4584

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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, October 23, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4581 - SUN'S SOLAR CYCLE

 

-  4581  -  SUN'S  SOLAR  CYCLE  -  -    Sun has reached its Solar Maximum and it could last for one year, 2024?    For most of human history, the Sun appeared stable. It was fusing hydrogen into helium beyond our awareness and helping Earth remain habitable. But in our modern technological age, that facade fell away.

--------------------------------------------   4581  -  SUN'S  SOLAR  CYCLE

-   We now know that the Sun is governed by its powerful magnetic fields, and as these fields cycle through their changes, the Sun becomes more active. Right now the Sun is at its “solar maximum”, a time of increased activity.

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-    “Solar Maximum” means pretty much what it sounds like. In this phase of the cycle, our star is exhibiting maximum activity. The Sun’s intense magnetic fields produce more sunspots and solar flares than at any other time in its 11-year cycle.

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-    The Solar Maximum is all based on the Sun’s magnetic fields. These fields are measured in Gauss units, which describe magnetic flux density. The Sun’s poles measure about 1 to 2 gauss, but sunspots are much higher at about 3,000 gauss.

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-     (Earth is only 0.25 to 0.65 gauss at its surface.) Since the magnetic field is so much stronger where sunspots appear, they inhibit convective heating from deeper inside the Sun. As a result, sunspots appear as dark patches.

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-    During solar maximum, the number of sunspots, and therefore, the amount of solar activity, increases.  This increase in activity causes real effects at Earth and throughout our solar system. The effects came into focus for many of us recently. In May 2024, the Sun launched multiple CMEs.

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-     As the magnetic fields and charged particles reached Earth, they triggered the strongest geomagnetic storm in 200 decades. These created colorful aurorae that were visible much further from the poles than usual. NASA says that these aurorae were likely among the strongest displays in the last 500 years.

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-    Each cycle is different, making it difficult to label peak solar activity. Different peaks have different durations and have higher or lower peaks than others.  Understanding the Sun’s cycle is important because it creates space weather.

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-    During solar maximum, the increased sunspots and flares also mean more coronal mass ejections (CMEs.) CMEs can strike Earth, and when they do, they can trigger aurorae and cause geomagnetic storms. CMEs, which are blobs of hot plasma, can also affect satellites, communications, and even electrical grids.

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-     During the solar maximum, the Sun produces an average of three CMEs every day, while it drops to one CME every five days during the solar minimum. The CMEs’ effect on satellites causes the most concern. In 2003, satellites experienced 70 different types of failures. The failures ranged from erroneous signals in a satellite’s electronics to the destruction of electrical components. The solar storm that occurred in 2003 was deemed responsible for 46 of those 70 failures.

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-   CMEs are also a hazard for astronauts orbiting Earth. The increased radiation poses a health risk, and during storms, astronauts seek safety in the most shielded part of the ISS, Russia’s Zvezda Service Module.

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-    Galileo and other astronomers noticed sunspots hundreds of years ago but didn’t know exactly what they were. In a 1612 pamphlet titled “Letters on Sunspots,” Galileo wrote ‘The sun, turning on its axis, carries them around without necessarily showing us the same spots, or in the same order, or having the same shape.’ This contrasted with others’ views on the spots, some of which suggested they were natural satellites of the Sun.

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-   We’ve known about the Sun’s magnetic fields for 200 hundred years, though at first, scientists didn’t know the magnetism was coming from the Sun. In 1724, an English geophysicist noticed that his compass was behaving strangely and was deflected from magnetic north throughout the day. In 1882, other scientists correlated these magnetic effects with increased sunspots.

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-   In recent decades, we’ve learned much more about our stellar companion thanks to spacecraft dedicated to studying it. NASA and the ESA launched the Solar and Heliospheric Observatory (SOHO) in 1995, and NASA launched the Solar Dynamics Observatory (SDO) in 2010. In 2011, we got our first 360-degree view of the Sun thanks to NASA’s two Solar TErrestrial RElations Observatory (STEREO) spacecraft. In 2019, NASA launched the Parker Solar Probe, which also happens to be humanity’s fastest spacecraft.

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-   Our understanding of the Sun and its cycles is far more complete now. The current cycle, Cycle 25, is the 25th one since 1755.   Solar Cycle 25 sunspot activity has slightly exceeded expectations.   The most powerful flare so far in Cycle 25 was on October 3rd, when the Sun emitted an X9 class flare. But scientists anticipate more flares and activity to come. There can be significantly powerful storms even in the cycle’s declining phase, though they’re not as common.

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-    On October 3, 2024, the Sun emitted a strong solar flare.  As of this date, this solar flare is the largest of Solar Cycle 25 and is classified as an X9.0 flare. X-class denotes the most intense flares, while the number provides more information about its strength.

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-   The Sun’s 11-year cycle is just one of its cycles, nested in larger cycles. The Gleissberg cycle lasts between 80 to 90 years and modulates the 11-year cycle. The de Vries cycle or Suess cycle lasts between 200 and 210 years, and the Hallstatt cycle lasts about 2,300 years. Both of these cycles contribute to long-term solar variation.

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-   Even with all we know about the Sun, there are big gaps in our knowledge. The Sun’s magnetic poles switch during the 11-year cycle, and scientists aren’t sure why.   There’s a lot more to learn about the Sun, but we won’t run out of time to study it any time soon. It’s in the middle of its 10-billion-year lifetime and will be a main-sequence star for another five billion years.

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October 20, 2024                            4581

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

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

--------------------- ---  Wednesday, October 23, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4583 - MOON SAMPLES - from 50 years ago?

 

4583 -   MOON  SAMPLES  -  from 50 years ago?  -      Samples collected from the surface of the moon by the crew of Apollo 16 more than 50 years ago have helped scientists reconstruct billions of years of lunar history.  New analysis of a distinct set of lunar breccias  have never been scrutinized in detail before.

----------------------------------   4583  -  MOON  SAMPLES  -  from 50 years ago?

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-   Astronauts John Young, Charles Duke and Ken Mattingly brought more than 95 kilogram of samples from the moon back to Earth after their mission to the moon's Descartes highlands in 1972.

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-   Among those samples were "regolith breccias," which form when moon dust is fused into rock by asteroid impacts. Once fused into a rock, these breccias preserve the geochemical composition of the regolith at the moment of its formation, which can be carefully analyzed for clues about how and when they were created.

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-   The moon's distinctive, heavily cratered appearance is the result of countless collisions with asteroids since its formation around 4.5 billion years ago. Over such extensive history, the matter of what happened and when it happened quickly becomes complicated.

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-   Sophisticated analytical mass spectrometry techniques were used to analyze the makeup of gases trapped in smaller chip samples, known as soil-like breccias. These samples, which were among those raked from the moon's surface by the Apollo 16 crew, had never been subjected to mass spectrometry before.

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-   Mass spectrometry, which identifies molecules in samples and quantifies their relative abundance, can help us determine how much time the samples spent exposed on or near the moon's surface. That helps give us a clearer idea of the history of impacts on this particular area of the moon.

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-    This helped advance scientists' understanding of how the surface of the moon has been changed by the solar wind and violently blasted by asteroids over the course of more than 2 billion years.

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-    Over the course of the samples' time on the surface of the moon as regolith, they were exposed to varying amounts of solar wind, charged particles flowing from the sun which also carry traces of noble gases like argon and xenon, which built up on the outer layers of their mineral grains for millions of years before they were struck by an asteroid.

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-    The moon's history is the Earth's history too.  The record of asteroid bombardments etched on its face and under its surface can help us understand the conditions of the early solar system which formed our planet as well as its closest neighbor.

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-   Unlike the Earth, however, the moon's history is locked in geological time capsules on its surface, untouched by plate tectonics or erosion, which allows us to use cutting-edge technology like mass spectrometry to unlock their secrets.

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-    Previous research had analyzed the traces of noble gases within larger fragments of the Apollo 16 breccia samples, helping researchers separate the samples into two groups, "ancient," aged between 3.8 and 2.4 billion years old, and "young," which were formed between 2.5 and 1.7 billion years ago.

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-   NASA provided the researchers with 11 moon samples for analysis. Nine of the samples revealed a wide range of exposure ages, from 2.5 billion years ago to less than 1 billion. This suggests they are made up of lunar soil from an area which has had a varied history of impacts, where some were exposed to the solar wind for billions of years, while others were dredged up to the surface by more recent impacts.

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-   The team also found that two of the samples had much lower concentrations of noble gases, suggesting they were formed much more recently, and were perhaps exposed to solar wind for less than 1 million years. The team suggest that the impact which formed the nearby South Ray crater might have been the source of that sample.

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-   This study establishes for the first time that soil-like breccias are their own distinct category, with their own histories to share. Combined with analysis of the ancient and young rocks recovered by Apollo 16, we can build a much more complete picture of the history of this part of the moon during the early solar system, where heavier impacts on the lunar surface in its first billion years or so gave way to less intense periods from 2 billion years ago.

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-   The research could also help inform ongoing efforts to send future missions to the moon in the near future, like NASA's Artemis program, which plans to establish long-term human lunar habitats.

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-   One of the challenges of establishing long-term habitats for humans on the moon is making decisions about how we can use the natural resources which await future missions so they don't have to carry everything they'll need with them from Earth.  Studies like this add to our knowledge base about where useful elements like noble gases can be found in the lunar regolith, and how abundant they might be.

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-   It's remarkable to think that the samples Apollo 16 brought back more than half a century ago still have secrets to reveal about the moon's history, and that they could yet help shape how we explore the solar system in the decades to come.

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October 21, 2024                                                4583

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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”  -----------

--------------------- ---  Tuesday, October 22, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4582 - RELATIVITY - The Evidence for Einstein's Theory?

 

-  4582 -   RELATIVITY  -  The Evidence for Einstein's Theory?  -   Albert Einstein's famous theory of relativity has been borne out in the real world, measured in eclipses, distorted galaxies and even the universe's structure.   The theory of gravity is general relativity (GR), first cooked up by Albert Einstein himself in a magnificent feat that took seven years to complete and provided amazing insights into how the world works.

---------------------------  4582  -  RELATIVITY  -  The Evidence for Einstein's Theory?

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-    It's easy enough to state the bare essence of the theory, "Matter and energy tell space-time how to bend, and the bending of space-time tells matter how to move." But the actual mechanics take a whopping 10 equations to describe, with each one very difficult and highly interconnected with the others.

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-  Out of all the features of his new theory, Einstein was proudest of its ability to explain the details of the orbit of Mercury. That innermost planet has a slightly elliptical orbit, and that ellipse ever-so-slowly rotates around the sun. In other words, the place where Mercury is farthest from the sun slowly changes with time.

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-    If you apply simple Newtonian gravity to the sun-Mercury system, this change over time, called “precession”, doesn't show up.    Isaac Newton's view is incomplete. Once you add in the gentle gravitational nudging and tweaking due to the other planets, almost all of the precession can be explained, but,  not all.

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-    By the early 1900s, it was a well-known problem in solar system dynamics, but not one that caused much controversy. Most folks just added it to the ever-growing list of "slightly weird things we can't explain about the universe" and assumed that we would find a mundane solution some day.

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-   But Einstein thought Mercury was giving him a clue. When, after years of attempts, he was able to flex his general relativistic muscles and explain precisely the orbital oddities of Mercury, he knew he had finally cracked the gravitational code.

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-    Before Einstein put the finishing touches on the big GR, he came to some startling realizations about the nature of gravity. If you're isolated on a rocket ship that accelerates at a smooth and constant 1g — providing the same acceleration as Earth's gravity does — everything in your laboratory will behave exactly as it would on the planet's surface.

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-    Einstein reasoned objects will fall to the ground at the same speed as on Earth; your feet will stay firmly planted on the floor, etc.  This equivalence between gravity (as experienced on Earth) and acceleration (as experienced in the rocket) propelled Einstein forward to develop his theory.

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-     But hidden in that scenario is a surprising insight. Imagine a beam of light entering a window on the left side of the spaceship. By the time the light crosses the spaceship to exit, where will it be?

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-   From the perspective of an outside observer, the answer is obvious. The light travels in a perfectly straight line, perpendicular to the path of the rocket. During the time the light was passing through, the rocket pushed itself forward. The light will then enter the rocket at one window, near the tip, and exit near the bottom, close to the engines.

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-   From the inside the spacecraft, though, things seem strange. In order for the light to enter a window near the tip and exit near the engines, the beam's path has to be curved. Indeed, that's exactly what you see.

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-   And since gravity is exactly the same as acceleration, light must follow curved paths around massive objects.

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-    It's difficult to observe this one experimentally, because you need a lot of mass and some light that passes close to the surface to get a detectable effect. But the 1919 solar eclipse proved just the right opportunity, and an expedition led by Sir Arthur Eddington found the exact shifting of distant starlight that Einstein's nascent theory had predicted.

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-   Another interesting result comes out of creative thought experiments surrounding general relativity. This conclusion relies on the good old-fashioned Doppler effect, but it's applied to an unfamiliar scenario.

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-   If something is moving away from you, the sound it produces will get stretched out, shifting down to lower frequencies.  That's the Doppler effect. The same is true of light: A car moving away from you appears ever-so-slightly redder than it would be if the vehicle were stationary. (The redder light, the lower the frequency.)

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-   Cops can take advantage of this shift by bouncing a light off your car to catch you speeding. If movement shifts light's wavelength, then acceleration can too: A bit of light traveling from the bottom to the top of an accelerating rocket will experience a redshift. And under GR, what goes for acceleration goes for gravity.  Light emitted from the surface of the Earth will shift down into redder frequencies the farther upward it travels.

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-   It took a few decades to conclusively demonstrate this prediction, because the effect is so tiny. But in 1959, Robert Pound and Glen Rebka proposed, designed, built and executed an experiment that enabled them to measure the redshift of light as it traveled a few stories up the Jefferson Laboratory at Harvard University.

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-   Even with all that evidence, we continue to put general relativity to the test. Any sign of a crack in Einstein's magnificent work would spark the development of a new theory of gravity, perhaps paving the way to uncovering the full quantum nature of that force. That's something we currently don't understand at all.

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-   In all regards, GR passes with flying colors; from sensitive satellites to gravitational lensing, from the orbits of stars around giant black holes to ripples of gravitational waves and the evolution of the universe itself, Einstein's legacy is likely to persist for quite some time.

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October 21, 2024      RELATIVITY  -  The Evidence for Einstein's Theory         4582

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

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

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

--------------------- ---  Monday, October 21, 2024  ---------------------------------

 

 

 

 

 

           

 

 

- 4580 - LARGER GALAXY STRUCTURES?

 

-  4580  -  LARGER  GALAXY STRUCTURES?  -  The Milky Way might be part of an even larger structure than Laniakea.  If you want to pinpoint your place in the Universe, start with your cosmic address. You live on Earth->Solar System->Milky Way Galaxy->Local Cluster->Virgo Cluster->Virgo Supercluster->Laniakea.

-----------------------------------  4580  -    LARGER  GALAXY STRUCTURES?

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-   Thanks to new deep sky surveys, astronomers now think all above places are part of an even bigger cosmic structure in the “neighborhood” called the “Shapley Concentration”.

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-   Astronomers refer to the Shapley Concentration as a “basin of attraction”. That’s a region loaded with mass that acts as an “attractor”. It’s a region containing many clusters and groups of galaxies and comprises the greatest concentration of matter in the local Universe. All those galaxies, plus dark matter, lend their gravitational influence to the Concentration. There are many of these basins in the Universe, including Laniakea.

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-     Astronomers measured the motions of some 56,000 galaxies to understand these basins and their distribution in space.  Our universe is like a giant web, with galaxies lying along filaments and clustering at nodes where gravitational forces pull them together.   Just as water flows within watersheds, galaxies flow within cosmic basins of attraction. The discovery of these larger basins could fundamentally change our understanding of cosmic structure.

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-    “Redshift” surveys revealed a possible shift in the size and scale of our local galactic basin of attraction. We already know that we “live” in Laniakea, which is about 500 million light-years across. However, the motions of other clusters indicate there’s a larger “attractor” directing the cluster flow.

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-    The Cosmic Flows data suggest that we could be part of the “Shapley Concentration”, which could be 10 times the volume of Laniakea. It’s about half the volume of the largest structure in space, known as “the Great Wall”, which is a string of galaxies stretching across  1.4 billion light-years.

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-    The “2dF Galaxy Redshift Survey”  contains the structure known as the "Sloan Great Wall". The Shapley Concentration was first observed by astronomer Harlow Shapley in the 1930s as a “cloud” in the constellation Centaurus. This supercluster appears along the direction of motion of the Local Group of galaxies (where we live).

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-    Scientists speculated that this could be influencing our galaxy’s peculiar motion.  The Virgo Supercluster (and the Local Group and Milky Way Galaxy) appears to be moving toward the Shapley Concentration.

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-    Where do these basins of attraction come from? In one sense, they’re as old as the Universe and its cosmic web of matter. The seeds for the web and those basins of attraction were planted some 13.8 billion years ago.

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-    After the Big Bang, the infant Universe was in a hot dense state. As it expanded and cooled, the density of matter started to fluctuate. There were tiny differences in those density fluctuations. Think of them as the earliest “seeds” of galaxies, galaxy clusters, and even vaster structures that we see in today’s Universe.

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-   As astronomers survey the sky, they find evidence for all those different structures. Now, they have to explain them. The idea that the Shapley Concentration is the large basin that our Laniakea belongs to means that current cosmological models don’t quite explain its existence.

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-    Our cosmic surveys may not yet be large enough to map the full extent of these immense basins.   The main actor in all these galaxies, clusters, and superclusters, is gravity. The more mass, the more gravity influences motions and matter distribution.

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-     These basins of attraction exert a sort of “tug of war” on galaxies that lie between them. That influences their motions. In particular, redshift surveys will map the radial motion (along the line of sight), velocities (how fast they’re moving), and other related motions. By mapping the velocities of galaxies throughout our local Universe, they can define the region of space where each supercluster dominates.

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-   Astronomers aren’t mapping just the luminous material in galaxies. They also have to take into account the inferred existence of dark matter. There are other complications as well.   Not all galaxies are the same.   They differ in their shapes and matter density. Astronomers can get around this by measuring something called “galaxy peculiar velocity”. That’s the difference between its actual velocity and the expected “Hubble flow” velocity (which reflects gravitational interactions between galaxies).

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-    The results of these surveys should provide ever more precise 3D maps of these regions of space. That includes their structures as well as their motions and velocities. Those maps, in turn, should give greater insight into the distribution of all matter (including cold dark matter) throughout the Universe.

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October 19, 2024          LARGER  GALAXY STRUCTURES?                   4580

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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”  -----------

--------------------- ---  Sunday, October 20, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4579 - DARK MATTER MYSTERIES?

 

-  4579  -  DARK  MATTER  MYSTERIES?  -    Perhaps our theories of gravity are simply incorrect, and that the fundamental force works differently on large scales than we expect. Often known as "modified Newtonian dynamics," or MOND models, these suggestions that there is no dark matter and the ultrafast speeds at which stars and galaxies are seen to rotate around one another is a consequence of gravity behaving in surprising ways.

-------------------------------------------  4579  -  DARK  MATTER  MYSTERIES?

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-   In the 1930s, a Swiss astronomer named Fritz Zwicky noticed that galaxies in a distant cluster were orbiting one another much faster than they should have been given the amount of visible mass they had. He proposed than an unseen substance, which he called “dark matter”, might be tugging gravitationally on these galaxies.

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-   Since then, researchers have confirmed that this mysterious material can be found throughout the universe, and that it is six times more abundant than the normal matter that makes up ordinary things like stars and people.

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-     Originally, some scientists conjectured that the missing mass in the universe was made up of small faint stars and black holes, though detailed observations have not turned up nearly enough such objects to account for dark matter's influence.

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-    The current leading contender for dark matter's mantle is a hypothetical particle called a “Weakly Interacting Massive Particle”, or WIMP, which would behave sort of like a neutron except would be between 10 and 100 times heavier than a proton.

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-    If dark matter is made from WIMPs, they should be all around us, invisible and barely detectable. So why haven't we found any yet? While they wouldn't interact with ordinary matter very much, there is always some slight chance that a dark-matter particle could hit a normal particle like a proton or electron as it travels through space.

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-    Researchers have built experiment after experiment to study huge numbers of ordinary particles deep underground, where they are shielded from interfering radiation that could mimic a dark-matter-particle collision. The problem? After decades of searching, not one of these detectors has made a credible discovery.

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-    Earlier this year, the Chinese PandaX experiment reported the latest WIMP nondetection. It seems likely that dark-matter particles are much smaller than WIMPs, or lack the properties that would make them easy to detect.

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-    Ordinary matter is made up of everyday particles like protons and electrons, as well as a whole zoo of more exotic particles like neutrinos, muons and pions. So, some researchers have wondered if dark matter, which makes up 85 percent of the matter in the universe, might also be just as complicated.

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-   There is no good reason to assume that all the dark matter in the universe is built out of one type of particle.   Dark protons could combine with dark electrons to form dark atoms, producing configurations as diverse and interesting as those found in the visible world.

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-     Along with additional particles of dark matter, there is the possibility that dark matter experiences forces analogous to those felt by regular matter. Some researchers have searched for "dark photons," which would be like the photons exchanged between normal particles that give rise to the electromagnetic force, except they would be felt only by dark matter particles.

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-    Physicists in Italy are gearing up to smash a beam of electrons and their antiparticles, known as positrons, into a diamond.  If dark photons do exist, the electron-positron pairs could annihilate and produce one of the strange force-carrying particles, potentially opening a brand-new sector of the universe.

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-    Other dark-matter particles are starting to gain favor. One of the leading replacements is a hypothetical particle known as an “axion”, which would be extremely light, perhaps as little as 10 raised to the 31st power less massive than a proton.

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-    Axions are now being searched for in a few experiments. Recent computer simulations have raised the possibility that these axions could form star-like objects, which might produce detectable radiation that would be quite similar to mysterious phenomena known as “fast-radio bursts”.

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-    Astronomers discovered dark matter through its gravitational interactions with ordinary matter, suggesting that this is its main way of making its presence known in the universe. According to some theories, dark-matter particles should be their own antiparticles, meaning that two dark-matter particles would annihilate with one another when they meet.

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-    The “Alpha Magnetic Spectrometer” (AMS) experiment on the International Space Station has been searching for the telltale signs of this annihilation since 2011and has already detected hundreds of thousands of events. Scientists still aren't sure if these are coming from dark matter, and the signal has yet to help them pin down exactly what dark matter is.

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-    Because it so massively outweighs ordinary matter, dark matter is often said to be the controlling force that organizes large structures such as galaxies and galactic clusters. So, it was strange when, earlier this year, 2024, astronomers announced that they had found a galaxy named “NGC 1052-DF2” that seemed to contain hardly any dark matter at all. "Dark matter is apparently not a requirement for forming a galaxy”.

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-     A long-standing mystery in particle physics are the puzzling results of a European experiment known as DAMA/LIBRA. This detector located in an underground mine below the Gran Sasso mountain in Italy has been searching for a periodic oscillation in dark matter particles. This oscillation should arise as the Earth moves in its orbit around the sun while flying through the galactic stream of dark matter surrounding our solar system, sometimes called the “dark matter wind”. Since 1997, DAMA/LIBRA has claimed to see exactly this signal, though no other experiment has seen anything like this. 

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-   A signal from the beginning of time has led some physicists to suggest that dark matter might have an electrical charge. Radiation with a wavelength of 21 centimeters was emitted by stars in the universe's infancy, just 180 million years after the Big Bang. It was then absorbed by cold hydrogen that was around at the same time.

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-    Neutrons are regular matter particles with a limited lifetime. After around 14.5 minutes, a lone neutron unmoored from an atom will decay into a proton, an electron and a neutrino. But two different experimental setups give slightly different lifetimes for this decay, with the discrepancy between them about 9 seconds.

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-    Physicists suggested that if 1 percent of the time, some neutrons were decaying into dark-matter particles, it could account for this anomaly.   Astronomers monitored neutrons for a signal that could be dark matter but were unable to detect anything. They suggested that other decay scenarios might still be possible.    Given the difficulties that scientists have faced trying to detect and explain dark matter, a reasonable questioner might wonder if they're going about it all wrong.

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-    Dark matter is still an “unconfirmed model".  However, the latest evidence also suggests that dark matter is “real”.

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October 18, 2024            DARK  MA?TTER  MYSTERIES?                 4579

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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”  -----------

--------------------- ---  Sunday, October 20, 2024  ---------------------------------