-  4590 -  GALAXIES  -  what are the earliest found?  -   The James Webb Space Telescope (JWST) is the largest and most powerful space telescope built to date. Since it was launched in December 2021 it has provided groundbreaking insights. These include discovering the earliest and most distant known galaxies, which existed just 300 million years after the Big Bang.

----------------------------------   4590  -  GALAXIES  -  what are the earliest found?

-    Distant objects are also very ancient because it takes a long time for the light from these objects to reach telescopes. JWST has now found a number of these very early galaxies. We're effectively looking back in time at these objects, seeing them as they looked shortly after the birth of the universe.

-

-    These observations from JWST agree with our current understanding of cosmology and of galaxy formation. But they also reveal aspects we didn't expect. Many of these early galaxies shine much more brightly than we would expect given that they existed just a short time after the Big Bang.

-

-    Brighter galaxies are thought to have more stars and more mass. It was thought that much more time was needed for this level of star formation to take place. These galaxies also have actively growing black holes at their centers.  This is a sign that these objects matured quickly after the Big Bang.

-

-    Scientists have been able to study these early galaxies by combining JWST's detailed images with its powerful capabilities for spectroscopy.   Spectroscopy is a method for interpreting the electromagnetic radiation that's emitted or absorbed by objects in space. This in turn can tell you about the properties of an object.

-

-   Our understanding of cosmology and galaxy formation rests on a few fundamental ideas. One of these is the “cosmological principle”, which states that, on a large scale, the universe is homogeneous (the same everywhere) and isotropic (the same in all directions). Combined with Einstein's theory of general relativity, this principle allows us to connect the evolution of the universe to its energy and mass content.

-

-    The James Webb telescope has brought cosmology to a tipping point. Will it soon reveal new physics?  The standard cosmological model, known as the "Hot Big Bang" theory, includes three main components. One is the ordinary matter that we can see with our eyes in galaxies, stars and planets. A second ingredient is cold dark matter (CDM), slow-moving matter particles that do not emit, absorb or reflect light.

-

-    The third component is what's known the “cosmological constant” (Λ, or lambda). This is linked to something called “dark energy” and is a way of explaining the fact that the expansion of the universe is accelerating. Together, these components form what is called the ΛCDM model of cosmology.

-

-    “Dark energy” makes up about 68% of the total energy content of today's universe.  Despite not being directly observable with scientific instruments, “dark matter” is thought to make up most of the matter and comprises about 27% of the universe's total mass and energy content.

-

-   While dark matter and dark energy remain mysterious, the ΛCDM model of cosmology is supported by a wide range of detailed observations. These include the measurement of the universe's expansion, the cosmic microwave background, or CMB (the "afterglow" of the Big Bang) and the development of galaxies and their large-scale distribution and the way that galaxies cluster together.

-

-   The ΛCDM model lays the groundwork for our understanding of how galaxies form and evolve.   The CMB, which was emitted about 380,000 years after the Big Bang, provides a snapshot of early fluctuations in density that occurred in the early universe. These fluctuations, particularly in dark matter, eventually developed into the structures we observe, galaxies and stars.

-

-     How does gas in galaxies cool and condense to form stars?   The effects of supernovae, stellar winds and black holes that emit significant amounts of energy (sometimes called active galactic nuclei, or AGN) can all heat or expel gas from galaxies. This in turn can boost or curtail star formation and therefore influence the growth of galaxies.

-

-   The efficiency and scale of these "feedback processes", as well as their cumulative impact over time, are poorly understood. They are a significant source of uncertainty in mathematical models, or simulations, of galaxy formation.

-

-    Significant advances in complex numerical simulations of galaxy formation have been made over the past ten years. They relate star formation to the evolution of dark matter halos. These halos are massive, invisible structures made from dark matter that effectively anchor galaxies within them.

-

-   One model of galaxy formation assumes that the rate at which stars form in a galaxy is directly tied to gas flowing into those galaxies. This model also proposes that the star formation rate in a galaxy is proportional to the rate at which dark matter halos grow. It assumes a fixed efficiency at converting gas into stars.

-

-   This "constant star formation efficiency" model is consistent with star formation increasing dramatically in the first billion years after the Big Bang. The rapid growth of dark matter halos during this period would have provided the necessary conditions for galaxies to form stars efficiently. Despite its simplicity, this model has successfully predicted a wide range of real observations, including the overall rate of star formation.

-

-    JWST has ushered in a new era of discovery. With its advanced instruments, the space telescope can capture both detailed images and high resolution spectra that charts the intensity of electromagnetic radiation emitted or absorbed by objects in the sky. For JWST, these spectra are in the near infrared region of the electromagnetic spectrum. Studying this region is crucial for observing early galaxies whose optical light has turned into near infrared (or "redshifted") as the universe has expanded.

-

-    Redshift describes how the wavelengths of light from galaxies become stretched as they travel. The more distant a galaxy is, the greater its redshift.  Over the past two years, JWST has identified and characterized galaxies at redshifts with values of between 10 and 15. These galaxies, which formed around 200-500 million years after the Big Bang, are relatively small for galaxies (about 100 parsecs, or 3 quadrillion kilometres, across). They each consist of around 100 million stars, and form new stars at a rate of about one sun-like star per year.

-

-   While this does not sound very impressive, it implies that these systems double their content of stars within only 100 million years. For comparison, our own Milky Way galaxy takes about 25 billion years to double its stellar mass.

-

-    The surprising findings from JWST of bright galaxies at high redshifts, or distances, could imply that these galaxies matured faster than expected after the Big Bang. This is important because it would challenge existing models of galaxy formation.

-

-    The constant star-formation efficiency model while effective at explaining much of what we see, struggles to account for the large number of bright and distant galaxies observed with a redshift of more than ten.

-

-   To address this, scientists are exploring various possibilities. These include changes to their theories of how efficiently gas is converted into stars over time. They are also reconsidering the relative importance of the feedback processes how phenomena such as supernovae and black holes also help regulate star formation.

-

-    Some theories suggest that star formation in the early universe may have been more intense or "bursty" than previously thought, leading to the rapid growth of these early galaxies and their apparent brightness.

-

-    Others propose that different factors, such as lower amounts of galactic dust, a top-heavy distribution of star masses, or contributions from phenomena such as active black holes, could be responsible for the unexpected brightness of these early galaxies.

-

-   These explanations invoke changes to galaxy formation physics in order to explain JWST's findings. But scientists have also been considering modifications to broad cosmological theories. For example, the abundance of early, bright galaxies could be partly explained by a change to something called the matter power spectrum. This is a way to describe density differences in the universe.

-

-    One possible mechanism for achieving this change in the matter power spectrum is a theoretical phenomenon called "early dark energy". This is the idea that a new cosmological energy source with similarities to dark energy may have existed at early times, at a redshift of 3,000. This is before the CMB was emitted and just 380,000 years after the Big Bang.

-

-   This early dark energy would have decayed rapidly after the stage of the universe's evolution known as “recombination”.   Early dark energy could also alleviate the Hubble tension which is a discrepancy between different estimates of the universe's age.

-

-   However, other phenomena could account for the bright galaxies. Before JWST's observations are used to invoke changes to broad ideas of cosmology, a more detailed understanding of the physical processes in galaxies is essential.

 

The current record holder for the most distant galaxy — identified by JWST — is called JADES-GS-z14-0. The data gathered so far indicate that these galaxies have a large diversity of different properties.

-

-    Some galaxies show signs of hosting black holes that are emitting energy, while others seem to be consistent with hosting young, dust-free populations of stars. Because these galaxies are faint and observing them is expensive (it takes exposure times of many hours), only 20 galaxies for which the redshift is more than ten have been observed with spectroscopy to date, and it will take years to build a statistical sample.

-

-    A different angle of attack could be observations of galaxies at later cosmic times, when the universe was 1 billion to 2 billion years old (redshifts of between three and nine). JWST's capabilities give researchers access to crucial indicators from stars and gas in these objects that can be used to constrain the overall history of galaxy formation.

-

-    In the first year of JWST's operation, it was claimed that some of the earliest galaxies had extremely high stellar masses (the masses of stars contained within them) and a change in cosmology was needed to accommodate bright galaxies that existed in the very early universe. They were even dubbed "universe-breaker" galaxies.

-

-   Soon after, it was clear that these galaxies do not break the universe, but their properties can be explained by a range of different phenomena. Better observational data showed that the distances to some of the objects were overestimated (which led to an overestimation of their stellar masses).

-

-   The emission of light from these galaxies can be powered by sources other than stars, such as accreting black holes. Assumptions in models or simulations can also lead to biases in the total mass of stars in these galaxies.

-

-    As JWST continues its mission, it will help scientists refine their models and answer some of the most fundamental questions about our cosmic origins. It should unlock even more secrets about the universe's earliest days, including the puzzle of these bright, distant galaxies.

-

-

October 29, 2024         GALAXIES  -  what are the earliest found?               4590

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

--------  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 29, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4588 - UNIVERSE - You live in a golden age?

 

-  4588 -  UNIVERSE  -  You live in a golden age for learning about the universe because our most powerful telescopes have revealed that the universe is surprisingly simple on the largest visible scales. Likewise, our most powerful "microscope," the Large Hadron Collider, has found no deviations from known physics on the tiniest scales.

------------------------------------   4588  -  UNIVERSE  -  You live in a golden age?

-    The dominant theoretical approach combines “string theory”, a powerful mathematical framework with no successful physical predictions as yet, and "cosmic inflation” that, at a very early stage, the universe ballooned wildly in size. In combination, string theory and inflation predict the universe to be incredibly complex on tiny scales and completely chaotic on very large scales.

-

-    The nature of the expected complexity could take a bewildering variety of forms. On this basis, and despite the absence of observational evidence, many theorists promote the idea of a "multiverse": an uncontrolled and unpredictable cosmos consisting of many universes, each with totally different physical properties and laws.

-

-   So far, the observations indicate exactly the opposite. What should we make of the discrepancy? One possibility is that the apparent simplicity of the universe is merely an accident of the limited range of scales we can probe today, and that when observations and experiments reach small enough or large enough scales, the complexity will be revealed.

-

-    The other possibility is that the universe really is very simple and predictable on both the largest and smallest scales.  This possibility should be taken far more seriously. For, if it is true, we may be closer than we imagined to understanding the universe's most basic puzzles. And some of the answers may already be staring us in the face.

-

-   According to “string theory”, the basic building blocks of the universe are miniscule, vibrating loops and pieces of sub-atomic string. As currently understood, the theory only works if there are more dimensions of space than the three we experience. So, string theorists assume that the reason we don't detect them is that they are tiny and curled up.

-

-    Unfortunately, this makes string theory hard to test, since there are an almost unimaginable number of ways in which the small dimensions can be curled up, with each giving a different set of physical laws in the remaining, large dimensions.

-

-   Meanwhile, “cosmic inflation” is a scenario proposed in the 1980s to explain why the universe is so smooth and flat on the largest scales we can see. The idea is that the infant universe was small and lumpy, but an extreme burst of ultra-rapid expansion blew it up vastly in size, smoothing it out and flattening it to be consistent with what we see today.

-

-    “Inflation” is also popular because it potentially explains why the energy density in the early universe varied slightly from place to place. This is important because the denser regions would have later collapsed under their own gravity, seeding the formation of galaxies.

-

-   Over the past three decades, the density variations have been measured more and more accurately both by mapping the cosmic microwave background, the radiation from the big bang,  and by mapping the three-dimensional distribution of galaxies.

-

-   The early extreme burst of expansion  smoothed and flattened the universe and generated long-wavelength gravitational waves, ripples in the fabric of space-time. Such waves would be a "smoking gun" signal confirming that inflation actually took place. However, so far the observations have failed to detect any such signal. Instead, as the experiments have steadily improved, more and more models of inflation have been ruled out.

-

-    Furthermore, during inflation, different regions of space can experience very different amounts of expansion. On very large scales, this produces a multiverse of post-inflationary universes, each with different physical properties.

-

-   This inflation scenario is based on assumptions about the forms of energy present and the initial conditions. While these assumptions solve some puzzles, they create others. String and inflation theorists hope that somewhere in the vast inflationary multiverse, a region of space and time exists with just the right properties to match the universe we see.

-

-   If we follow the expanding universe backward in time, using Einstein's theory of gravity and the known laws of physics, space shrinks away to a single point, the "initial singularity."  In trying to make sense of this infinitely dense, hot beginning, theorists pointed to a deep symmetry in the basic laws governing light and massless particles. This symmetry, called "conformal" symmetry, means that neither light nor massless particles actually experience the shrinking away of space at the big bang.

-

-   By exploiting this symmetry, one can follow light and particles all the way back to the beginning. Doing so, we could describe the initial singularity as a "mirror": a reflecting boundary in time, with time moving forward on one side, and backward on the other.

-

-   Picturing the big bang as a mirror neatly explains many features of the universe which might otherwise appear to conflict with the most basic laws of physics. For example, for every physical process, quantum theory allows a "mirror" process in which space is inverted, time is reversed and every particle is replaced with its anti-particle (a particle similar to it in almost all respects, but with the opposite electric charge).

-

-    According to this powerful symmetry, called “CPT symmetry”, the "mirror" process should occur at precisely the same rate as the original one. One of the most basic puzzles about the universe is that it appears to violate CPT symmetry because time always runs forward and there are more particles than anti-particles.

-

-   Our mirror hypothesis restores the symmetry of the universe. When you look in a mirror, you see your mirror image behind it: if you are left-handed, the image is right-handed and vice versa. The combination of you and your mirror image is more symmetrical than if you are alone.

-

-   Likewise, our universe back through the big bang is its mirror image, a pre-bang universe in which (relative to us) time runs backward and antiparticles outnumber particles. For this picture to be true, we don't need the mirror universe to be real in the classical sense (just as your image in a mirror isn't real).

-

-    Quantum theory, which rules the microcosmos of atoms and particles, challenges our intuition, so at this point, the best we can do is think of the mirror universe as a mathematical device which ensures that the initial condition for the universe does not violate CPT symmetry.

-

-    This new picture provided an important clue to the nature of the unknown cosmic substance called “dark matter”. Neutrinos are very light, ghostly particles which, typically, move at close to the speed of light and which spin as they move along, like tiny tops.

-

-   If you point the thumb of your left hand in the direction the neutrino moves, then your four fingers indicate the direction in which it spins. The observed, light neutrinos are called "left-handed" neutrinos.

-

-    Heavy "right-handed" neutrinos have never been seen directly, but their existence has been inferred from the observed properties of light, left-handed neutrinos. Stable, right-handed neutrinos would be the perfect candidates for dark matter because they don't couple to any of the known forces except gravity.

-

-   This mirror hypothesis allowed the calculation to exactly how many would form, and to show they could explain the cosmic dark matter.   If the dark matter consists of stable, right-handed neutrinos, then one of three light neutrinos that we know of must be exactly massless. This prediction is now being tested using observations of the gravitational clustering of matter made by large-scale galaxy surveys.

-

-    Encouraged by this result led to another big puzzle: why is the universe so uniform and spatially flat, not curved, on the largest visible scales?  “Entropy” is a concept which quantifies the number of different ways a physical system can be arranged.

-

-     For example, if we put some air molecules in a box, the most likely configurations are those which maximize the entropy with the molecules more or less smoothly spread throughout space and sharing the total energy more or less equally. These kinds of arguments are used in “statistical physics”, the field which underlies our understanding of heat, work and thermodynamics.

-

-   The late physicist Stephen Hawking famously generalized statistical physics to include gravity. Using this elegant argument, he calculated the temperature and the entropy of black holes. Using this "mirror" hypothesis, astronomers managed to extend their arguments to cosmology and to calculate the entropy of entire universe.

-

-   To their surprise, the universe with the highest entropy (meaning it is the most likely, just like the atoms spread out in the box) is ”flat” and expands at an accelerated rate, just like the real one. So statistical arguments explain why the universe is flat and smooth and has a small positive accelerated expansion, with no need for cosmic inflation.

-

-   How would the “primordial density variations”, usually attributed to inflation, have been generated in our symmetrical mirror universe? Recently, they showed that a specific type of quantum field (a dimension zero field) generates exactly the type of density variations we observe, without inflation.   These density variations aren't accompanied by the long wavelength gravitational waves which inflation predicts, and which haven't been seen.

-

-   Even if this new theory fails, it has taught us a valuable lesson. There may well be simpler, more powerful and more testable explanations for the basic properties of the universe than those the standard orthodoxy provides.

-

-    By facing up to cosmology's deep puzzles, guided by observations and exploring directions as yet unexplored, we may be able to lay more secure foundations for both fundamental physics and our understanding of the universe.

-

-

October 27, 2024              UNIVERSE  -  You live in a golden age?              4588

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

--------  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 27, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4589 - EUCLID TELESCOPE - maps the universe?

 

-  4589 -  EUCLID  TELESCOPE  -  maps the universe?  -    The powerful telescope has captured millions of stars and galaxies in a mosaic that represents just the first piece of a massive puzzle the observatory has been designed to solve.  The European Space Agency mission, launched in July 2023, will create the largest and most accurate 3D map of the universe to help answer enduring questions about the “dark side” of the universe.

-------------------   4589  -   EUCLID  TELESCOPE  -  maps the universe?

-  Scientists assembled the first piece of the map, which includes 208 gigapixels, from 260 observations made between March 25 and April 8, 2024.  But it accounts for a tiny fraction of the broad survey that Euclid will make of the sky in the future, measuring the shape, distance and motion of billions of galaxies.

-

-    The stunning image is the first piece of a map that in six years will reveal more than one third of the sky. This is just 1% of the map, and yet it is full of a variety of sources that will help scientists discover new ways to describe the Universe.

-

-    One of Euclid’s primary goals is to observe dark matter and dark energy. While dark matter has never been detected, it is believed to make up 85% of the total matter in the universe. Meanwhile, dark energy is a mysterious force thought to play a role in the accelerating expansion of the universe.

-

-   Astronomers hope the telescope’s observations of millions of galaxies will reveal hidden forces that provide the universe with its structure and drive its mysterious acceleration rate.  Euclid’s wide perspective can record data from a part of the sky 100 times bigger than what NASA’s James Webb Space Telescope’s camera can capture.   The telescope’s sensitive cameras can also capture intricate details of many celestial objects at once.

-

-    In the 1920s, astronomers Georges Lemaître and Edwin Hubble discovered that the universe has been expanding since its birth 13.8 billion years ago. But research that began in the 1990s has shown that something sparked an acceleration of the universe’s expansion about 6 billion years ago, and the cause remains a mystery.

-

-    Unlocking the true nature of dark energy and dark matter could help astronomers understand what the universe is made of, how its expansion has changed over time, and whether there is more to understanding gravity than meets the eye. Dark matter and dark energy are also thought to play a role in the distribution and movement of objects, such as galaxies and stars, across the cosmos.

-

-   Euclid is designed to observe billions of galaxies that stretch 10 billion light-years away to reveal how matter may have been stretched and pulled apart by dark energy over time. These observations will effectively allow Euclid to see how the universe has evolved over the past 10 billion years.

-

-    During its observations, the telescope will catalog 1.5 billion galaxies and the stars within them, collecting a treasure trove of data for astronomers that includes each galaxy’s mass and number of stars created per year.

-

-    Euclid’s first images are a promising glimpse of the broader map it will reveal in the future.   The images capture detail from clusters of stars near an individual galaxy to some of the largest structures in the universe. We are beginning to see the first hints of what the full Euclid data will look like when it reaches the completion of the prime survey.

-

-

October 27, 2024        EUCLID  TELESCOPE  -  maps the universe?                4583

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

--------  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 27, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4587 - UNIVERSE - how big is it?

 

-  4587 -  UNIVERSE  -  how big is it?  We live in a golden age for learning about the universe. Our most powerful telescopes have revealed that the universe is surprisingly simple on the largest visible scales. Likewise, our most powerful "microscope," the Large Hadron Collider, has found no deviations from known physics on the tiniest scales.

-

--------------------------------------------   4587  -  UNIVERSE  -  how big is it?

-

-   The dominant theoretical ideas combines string theory, a powerful mathematical framework with no successful physical predictions, and "cosmic inflation", the idea that, at a very early stage, the universe ballooned wildly in size. In combination, string theory and inflation predict the universe to be incredibly complex on tiny scales and completely chaotic on very large scales.  What gives?

-

-    The nature of the expected complexity could take a bewildering variety of forms.   Despite the absence of observational evidence, many theorists promote the idea of a "multiverse": an uncontrolled and unpredictable cosmos consisting of many universes, each with totally different physical properties and laws.

-

-   So far, the observations indicate exactly the opposite. What should we make of the discrepancy? One possibility is that the apparent simplicity of the universe is merely an accident of the limited range of scales we can probe today, and that when observations and experiments reach small enough or large enough scales, the complexity may be revealed.

-

-   The other possibility is that the universe really is very simple and predictable on both the largest and smallest scales. If this is true, we may be closer than we imagined to understanding the universe's most basic puzzles. And some of the answers may already be staring us in the face.

-

-   The current orthodoxy is the culmination of decades of effort by thousands of serious theorists. According to string theory, the basic building blocks of the universe are miniscule, vibrating loops and pieces of sub-atomic string. As currently understood, the theory only works if there are more dimensions of space than the three we experience. So, string theorists assume that the reason we don't detect them is that they are too tiny and curled up.

-

-    This makes string theory hard to test, since there are an almost unimaginable number of ways in which the small dimensions can be curled up, with each giving a different set of physical laws in the remaining, large dimensions.

-

-    Meanwhile, “cosmic inflation” is a scenario proposed in the 1980s to explain why the universe is so smooth and flat on the largest scales we can see. The idea is that the infant universe was small and lumpy, but an extreme burst of ultra-rapid expansion blew it up vastly in size, smoothing it out and flattening it to be consistent with what we see today.

-

-   “Inflation” is also popular because it potentially explains why the energy density in the early universe varied slightly from place to place. This is important because the denser regions would have later collapsed under their own gravity, seeding the formation of galaxies.

-

-   Over the past three decades, the density variations have been measured more and more accurately both by mapping the cosmic microwave background, the radiation from the big bang, and by mapping the three-dimensional distribution of galaxies.

-

-    In most models of inflation, the early extreme burst of expansion which smoothed and flattened the universe also generated long-wavelength gravitational waves, ripples in the fabric of space-time. Such waves would be a "smoking gun" signal confirming that inflation actually took place. However, so far the observations have failed to detect any such signal. Instead, as the experiments have steadily improved, more and more models of inflation have been ruled out.

-

-   During inflation, different regions of space can experience very different amounts of expansion. On very large scales, this produces a multiverse of post-inflationary universes, each with different physical properties.

-

-    The “inflation scenario” is based on assumptions about the forms of energy present and the initial conditions. While these assumptions solve some puzzles, they create others. String and inflation theorists hope that somewhere in the vast inflationary multiverse, a region of space and time exists with just the right properties to match the universe we see.

-

-    Over the past several decades, there have been many opportunities for experiments and observations to reveal specific signals of string theory or inflation. But none have been seen. Again and again, the observations turned out simpler and more minimal than anticipated.

-

-    One of cosmology's greatest paradoxes, if we follow the expanding universe backward in time, using Einstein's theory of gravity and the known laws of physics, space shrinks away to a single point, the "initial singularity."

-

-   In trying to make sense of this infinitely dense, hot beginning, theorists pointed to a deep symmetry in the basic laws governing light and massless particles. This symmetry, called "conformal" symmetry, means that neither light nor massless particles actually experience the shrinking away of space at the big bang.

-

-    Astronomers can describe the initial “singularity” as a "mirror", a reflecting boundary in time (with time moving forward on one side, and backward on the other).   Picturing the big bang as a mirror neatly explains many features of the universe which might otherwise appear to conflict with the most basic laws of physics.

-

-    For every physical process, quantum theory allows a "mirror" process in which space is inverted, time is reversed and every particle is replaced with its anti-particle (a particle similar to it in almost all respects, but with the opposite electric charge).

-

-    According to this powerful symmetry, called “CPT symmetry”, the "mirror" process should occur at precisely the same rate as the original one. One of the most basic puzzles about the universe is that it appears to violate CPT symmetry because time always runs forward and there are more particles than anti-particles.

-

-    The  “mirror hypothesis” restores the symmetry of the universe. When you look in a mirror, you see your mirror image behind it: if you are left-handed, the image is right-handed and vice versa. The combination of you and your mirror image is more symmetrical than if you are alone.

-

-   Likewise, extrapolating our universe back through the big bang, its mirror image, a pre-bang universe in which (relative to us) time runs backward and antiparticles outnumber particles. For this picture to be true, we don't need the mirror universe to be real in the classical sense (just as your image in a mirror isn't real).

-

-   We think of the mirror universe as a mathematical device which ensures that the initial condition for the universe does not violate CPT symmetry.  Surprisingly, this new picture provided an important clue to the nature of the unknown cosmic substance called “dark matter”. -

-    Neutrinos are very light, ghostly particles which, typically, move at close to the speed of light and which spin as they move along, like tiny tops.    If you point the thumb of your left hand in the direction the neutrino moves, then your four fingers indicate the direction in which it spins. The observed, light neutrinos are called "left-handed" neutrinos.

-

-   Heavy "right-handed" neutrinos have never been seen directly, but their existence has been inferred from the observed properties of light, left-handed neutrinos. Stable, right-handed neutrinos would be the perfect candidates for dark matter because they don't couple to any of the known forces except gravity.

-

-    This mirror hypothesis allowed us to calculate exactly how many would form, and to show they could explain the cosmic dark matter.   If the dark matter consists of stable, right-handed neutrinos, then one of three light neutrinos that we know of must be exactly massless.   This prediction is now being tested using observations of the gravitational clustering of matter made by large-scale galaxy surveys.

-

-    Why is the universe so uniform and spatially flat, not curved, on the largest visible scales? The cosmic inflation scenario was invented by theorists to solve this problem.

-

-    Entropy is a concept which quantifies the number of different ways a physical system can be arranged. For example, if we put some air molecules in a box, the most likely configurations are those which maximize the entropy, with the molecules more or less smoothly spread throughout space and sharing the total energy more or less equally.

-

-   Physicists calculated the temperature and the entropy of black holes using this "mirror" hypothesis.    The universe with the highest entropy (meaning it is the most likely, just like the atoms spread out in the box) is flat and expands at an accelerated rate, just like the real one. So statistical arguments explain why the universe is “flat and smooth” and has a small positive accelerated expansion, with no need for cosmic inflation.

-

-   How would the primordial density variations, usually attributed to inflation, have been generated in our symmetrical mirror universe?   A specific type of quantum field (a dimension zero field) generates exactly the type of density variations we observe, without inflation. These density variations aren't accompanied by the long wavelength gravitational waves which inflation predicts, and which haven't been seen.

-

-   These results are very encouraging. But more work is needed to show that our new theory is both mathematically sound and physically realistic.  Even if our new theory fails, it has taught us a valuable lesson. There may well be simpler, more powerful and more testable explanations for the basic properties of the universe than those the standard orthodoxy provides.

-

-

October 26, 2024                UNIVERSE  -  how big is it?                    4587

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

--------  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 27, 2024  ---------------------------------

 

 

 

 

 

           

 

 

4586 - METEORITES AND ASTEROIDS - potential impacts

 

-  4586 -   METEORITES  AND  ASTEROIDS -  potential impacts.  -    Four "potentially hazardous" space rocks, which are between 100 and 580 feet across, will all make their closest approaches to Earth within less than 12 hours of one another on Thursday October 24, 2024. Two of them were only discovered earlier this month.

---------------------------   4586  -  METEORITES  AND  ASTEROIDS -  potential impacts

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-    A quartet of particularly hefty asteroids, including two that were discovered earlier this month and another that is as tall as a skyscraper, will make their closest approaches to Earth on Thursday, October 24,  all within 12 hours of one another. The "potentially hazardous" space rocks will all get similarly close to our planet, but pose zero threat to life on Earth.

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-   The first asteroid to make its closest approach will be “2015 HM1", the smallest of the four space rocks at around 100 feet across. It will reach its closest point to our planet at around 0:36 a.m. EDT when it reaches a minimum distance of 3.4 million miles from us.  That’s roughly   14 times the average distance between Earth and the moon.

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-    The next visitor will be the roughly 170-foot-wide space rock “2024 TP17”, which will make its closest approach at around 4:20 a.m. EDT and will get to within 2.9 million miles of our planet.

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-   The final two asteroids, “2002 NV16” and “2024 TR6”, will make their closest approaches within just four minutes of each other. 2002 NV16, which is around 580 feet across, making it the largest of the four, will reach a minimum distance of 2.8 million miles  at around 11:47 a.m. EDT.  It will be quickly followed by the 150-foot-wide asteroid 2024 TR6, which will come within 3.5 million miles of Earth at 11:51 a.m. EDT.

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-   The largest asteroid of the incoming quartet, 2002 NV16, will reach a minimum distance of 2.8 million miles from Earth, which is slightly closer than the other three space rocks will get to us.

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-   Two of the four asteroids, 2024 TR6 and 2024 TP17, were only recently discovered: the former was initially spotted on October 7, and the latter was first seen on October 12. That's not unusual; astronomers spot around 2,000 near-Earth asteroids every year, most of which are spotted as they near their closest approaches to Earth.

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-   The asteroids are all listed as potentially hazardous because their orbits around the sun bring them within 30 million miles of Earth. Most of them are not large enough to cause widespread damage if they ever hit the planet (which they won't). However, the largest of the incoming rocks, 2002 NV16, is large enough to wipe out a large city and cause planet-wide effects.

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-   The asteroids will not be visible from Earth. However, scientists may be able to capture radar images of the space rocks, which could help reveal more information about the newly discovered objects. Similar grainy images recently captured a bizarre snowman-shaped asteroid as it tumbled past Earth and revealed an unexpected trajectory change for a pyramid-size space rock.

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-   Some of the approaching asteroids will make even closer flybys of Earth over the next few decades: 2024 TR6 will return on August 5, 2039, when it will reach a minimum distance of 1.2 million miles from our planet; and 2024 TP17 will get to within 1.3 million miles of Earth on October 25, 2040.

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-   66 milllion years ago, Earth was struck by a city-size asteroid. The impact released the energy equivalent to the detonation of 72 trillion tons of TNT, carving a 100-mile-wide scar in what is now Mexico's Yucatán Peninsula.

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-   The most infamous effect of this asteroid, named the “Chicxulub impactor”, was the death of the nonavian dinosaurs along with around three-quarters of Earth's species in an event called the “Cretaceous-Paleogene extinction”.

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-    In an effort to prevent similarly catastrophic collisions, NASA's “Center for Near Earth Object Studies” (CNEOS) operates the Sentry impact-monitoring system, which continuously performs long-term analyses of possible future orbits of potentially hazardous asteroids. Here are the five asteroids that pose the greatest risk to Earth.

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-   1. Bennu.   Size: 0.30 mile.   Mass: 74 million tons.  Discovered in September, 1999 and officially designated "101955 Bennu (1999 RQ36)," the near-Earth asteroid Bennu currently poses the greatest risk of impacting our planet, but fortunately, not for some time. NASA scientists calculate that when Bennu makes a close approach to Earth on Septembr 24, 2182, there is a 0.037% — or 1 in 2,700 — chance that the asteroid will strike our planet.

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-    This carbon-rich asteroid is believed to have broken away from a larger asteroid between 2 billion and 700 million years ago. On September 24, 2023, NASA's OSIRIS-REx spacecraft returned a sample of Bennu to Earth, and the space rock has been analyzed by teams of researchers across the globe.

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-    Early results suggest that Bennu contains the building blocks of life, including the simple amino acid glycine, as well as many water-bearing minerals. This suggests Bennu's parent body witnessed many water-related episodes before eventually fracturing.

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-    If Bennu impacted Earth, it would release the energy equivalent to the detonation of          1.4 billion tons of TNT, causing regional destruction but lacking the potential to cause global devastation. If it were to impact a densely populated area, Bennu could cause millions of deaths.

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-    2. “29075 (1950 DA)”   Size: 0.81 mile.   Mass: 78 million tons.  The second-riskiest object is the asteroid was lost after its initial discovery in February 1950 and rediscovered 50 years later. “1950 DA” is believed to be a loose-rubble-pile asteroid with high iron-nickel content. Currently, 1950 DA has a 0.0029% — or 1 in 34,500 — chance of impacting Earth on March 16, 2880.

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-   If 1950 DA were to hit Earth, it would release the energy equivalent to 75 billion tons of TNT.  This isenough to trigger a global catastrophe that could potentially wipe out humanity.

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-    3.   “2023 TL4    Size: 0.20 mile.   Mass: 47 million tons.  This asteroid was discovered in 2023.  It shows that a newfound space object can immediately become one of the most potentially hazardous asteroids. From observations collected between October 8 and Octo 19, 2023, astronomers calculated that 2023 TL4 has a 0.00055% — or 1 in 181,000 — chance of striking Earth on October 10, 2119. Should such an impact occur, 2023 TL4 would release the energy equivalent to the detonation of 7.5 billion tons of TNT.

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-    4. “2007 FT3”.   Size: 0.21 mile.   Mass: 54 million tons.   2007 FT3 is defined as a "lost asteroid" because astronomers haven't seen it since 2007. This object's orbit is currently not well constrained, but NASA predicts that the asteroid has a 0.0000096% — or 1 in 10 million — chance of striking our planet on March 3, 2030. The asteroid has a slightly lower probability of 0.0000087% — or 1 in 11.5 million — chance of striking Earth on October 5, 2024.

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-   Should such an impact happen in 2024 or 2030, FT3 would release the energy equivalent to the detonation of 2.6 billion tons of TNT.  That is enough to cause massive regional damage, but not to trigger a global catastrophe.

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-    5. “1979 XB”.   Size: 0.41 mile.  Mass: 390 million tons.   Another lost asteroid, 1979 XB, hasn't been seen for around 40 years and thus also has a poorly understood orbit. From what CNEOS scientists do understand, the asteroid, which was first observed on December 11, 1979, has a 0.000055% — or 1 in 1.8 million — chance of striking Earth on Dec. 14, 2113. Such a collision would release the same energy as the detonation of 30 billion tons of TNT.

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-  “99942 Apophis”  ESA Herschel Space Observatory captured asteroid Apophis in its field of view during the approach to Earth on January 5 and 6, 2013.nnSize: 0.21 mile.   Mass:            27 million tons.

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-    Discovered in June 2004, Apophis was quickly identified as one of the most hazardous asteroids that could impact Earth. But that changed in 2021, when a radar observation campaign better constrained the asteroid's orbit. This led astronomers to conclude that the 1,100-foot-wide Apophis poses no risk to Earth for at least 100 years.

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-   Skywatchers will be able to watch Apophis during its close approach in 2029 as it passes within 20,000 miles with binoculars and telescopes, without the fear that its returns in 2036 and 2068 will threaten the planet.

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-   The idea of an asteroid strike is frightening, but all of the space rocks on this list are listed as "zero," or "white," on the “Torino Impact Hazard scale”.  Level 0, the white zone, indicates zero risk of impact or at least a risk so low it might as well be zero. This level applies not only to asteroids that will miss Earth but also to small objects from space that will burn up in the atmosphere and thus pose no threat.

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-   Levels 8 to 10, on the other hand, are in the red zone, representing asteroids that will certainly collide with Earth, with effects ranging from localized destruction (Level 8) and unprecedented regional devastation (Level 9) to global climatic catastrophe (Level 10) that may threaten the future of civilization as we know it.

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-    At the moment, there are no objects on the “Sentry Risk table” about level 0. Bennu and 1950 DA don't have Torino ratings because their predicted impacts are more than 100 years into the future. As NASA states, "There is currently no known significant threat of impact for the next hundred years or more."

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-   Of course, there still could be potentially hazardous objects out there waiting to be found.  Thousands of potential "city-killers" and even some "planet-killers" may be hiding in the sun's glare.  This is why CNEOS is ever vigilant in its search for near-Earth asteroids.

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October 24, 2024     METEORITES  AND  ASTEROIDS -  potential impacts       4586

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