3280 - QUANTUM MECHANICS - versus classical physics?

  -  3280   -   QUANTUM  MECHANICS  -  versus classical physics? Quantum Mechanic’s rules rely on “probabilities‘.   Quantum mechanics only reproduces classical physics on average. Based on these two insights, Neils Bohr argued that a quantum theory can never explain classical physics. 

-------------  3280  -   QUANTUM  MECHANICS  -  versus classical physics?

-  Quantum Mechanics does not make sense. All the rules of physics that we're used to simply do not work in the quantum world. 

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-  Put a “particle” in a box. According to classical physics (and common sense), that particle should stay in that box forever. But under quantum mechanics, that particle can simply be outside the box the next time you look. 

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-  In classical thinking, you can measure the momentum and position of something to an arbitrary degree of precision. Not so in the quantum world the more you know about one, the less you know about the other. Is something a wave or a particle?

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-  According to the classical viewpoint, you can pick one and only one. But quantum mechanics says something can be both a wave and a particle at the same time.

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-  The quantum world works under different rules, but,  at some point the rules of the subatomic give way to the rules of the macroscopic. But how? We're not exactly sure, and it's been a long, strange journey in trying to answer that question.

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-  The first person to put some useful labels on the ‘quantum world” was physicist Niels Bohr. In the early 1900s, scientists around the world were beginning to awaken to the strange and unexpected behavior of atomic and subatomic systems. 

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-  Scientists had, after decades of  work, realized that certain properties, like energy, come in discrete packets of levels dubbed "quanta." And while physicists were beginning to sketch out a mathematical foundation to explain these experiments, nobody had yet developed a complete, consistent framework. 

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-  Bohr was one of the first to attempt it and he promoted some ideas that would become the cornerstones of modern quantum theory.

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-  The first appeared in his early attempt to model the atom. In the 1920s, we had known through a variety of very cool experiments that the atom is made of a heavy, dense, positively charged nucleus surrounded by a swarm of tiny, light, negatively charged electrons. We also knew that these atoms could only absorb or emit radiation at very specific energies.

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-  Bohr put the electrons "in orbit" around the nucleus, orbiting around that dense core like planets in a miniature solar system. In a real solar system, the planets can have whatever orbit they like. But in Bohr's atom the electrons were stuck on little tracks of only have certain predefined orbital distances. 

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-  By jumping from one orbit to another, the atom could receive or emit radiation at specific energies. Its quantum nature was thus encoded.   

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-  There are a lot of potential ways to construct a quantum model of the atom why should this one be used? He found that when the electrons orbited very far away from the nucleus, their quantum nature disappeared and the atom could be perfectly described by classical electromagnetism. 

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-This was called the “Correspondence Principle“, and it was Bohr's argument that his model of the atom was the best. You can have any quantum theory you want, but the right ones are the ones that give way to classical physics under some limit. In the case of his atom, when the electrons got far away from the nucleus.

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-  Bohr's model of the atom was incomplete and would later be replaced by the “valence shell model” that remains to this day. But his Correspondence Principle lived on, and it formed a cornerstone of all quantum theories to come, a guiding light that allowed physicists to construct and select the right mathematics to describe the subatomic world.

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-  Around the same time Werner Heisenberg came up with his soon-to-be-famous “Uncertainty Principle“. Try to measure the “position” of a tiny particle, and you'll end up losing information about its “momentum“. Go for the opposite, trying to pin down its momentum, and you'll become ignorant about its position.

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-  Bohr took this idea and ran with it. He saw Heisenberg's Uncertainty Principle as a part of a much larger facet of the quantum world: that everything comes in pairs. 

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-  Consider the most famous pair in the quantum world, the wave and the particle. In classical systems, something is either purely a wave or purely a particle. You can pick one or the other to classify some behavior. But in quantum mechanics, these two properties are paired up: everything is simultaneously both a particle and a wave and always exhibits some properties of both.

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-  Quantum rules rely on probabilities, quantum mechanics only reproduces classical physics on average. Based on these two insights, Bohr argued that a quantum theory can never explain classical physics. In other words, atoms operate under one set of rules, and trains and people operate on another set of rules. They can and must be connected via the Correspondence Principle, but otherwise they live separate and parallel lives.

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-  Was Bohr right? Some physicists argue that we just haven't worked hard enough, and that we do fundamentally live in a quantum world, and that we can reproduce classical physics from purely quantum rules. 

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-  Other physicists argue that Bohr nailed it and we don't need to talk about it anymore. Most just keep their heads down and crunch through the math without worrying about it too much.  Just do your physics as long as you get the right answers.  

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-  September 16, 2021     QUANTUM  MECHANICS  -  classical physics?    3280                                                                                                                                                    

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

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--------------------- ---  Friday, September 17, 2021  ---------------------------

3279 - BIG BANG THEORY - what does it mean?

  -  3279   -   BIG  BANG  THEORY  -  what does it mean?     For almost a century, the term “ Big Bang Theory” has been bandied about by scholars. But what exactly does it mean? How was our Universe conceived in a massive explosion, what proof is there of this, and what does the theory say about the long-term projections for our Universe?

---------------------  3279  -   BIG  BANG  THEORY  -  what does it mean?     

-    In 1927, Catholic priest Georges Lemaître published a paper in which he reviewed the General Theory of Relativity, published by Albert Einstein in 1916, and found that “not only was the Universe expanding, but that it had originated at a finite point in time.”

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-  Few people took notice of Lemaître’s conclusions, but one person who did was Einstein himself, who told him: “Your calculations are correct, but your grasp of physics is abominable.”

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-  By 1929, however, it was Einstein’s calculations that had come under fire, stemming from “systematic observations of other galaxies” made by American astronomer Edwin Hubble, and Lemaitre’s findings began to find supporters.

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-   In 1929 Britain’s Royal Astronomical Society met to examine the conflicting data, and renowned mathematician Sir Arthur Eddington volunteered to work out a solution.   Hearing of this, Lemaître sent Eddington a copy of his 1927 paper, and in March 1931 the Society published an English translation.

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-  Most scientists who read Lemaitre’s paper accepted that the universe was “expanding“,  but, resisted the implication that the universe had a “beginning”.

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-  One of those who certainly resisted was Eddington, who wrote in the journal Nature that the notion of a beginning of the world was “repugnant”.  Lemaître responded with a letter to Nature, headlined “The beginning of the world from the point of view of quantum theory”:

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-  Lemaitre’s  quantum theory suggests a beginning of the world very different. Thermodynamical principles from the point of view of quantum theory stateds: 

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----------------  (1) Energy of constant total amount is distributed in “discrete quanta“.

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----------------   (2) The number of distinct quanta is ever increasing. If we go back in the course of time we must find fewer and fewer quanta, until we find all the energy of the universe packed in a few or even in a unique quantum.

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-    As Lemaitre’s findings gained acceptance, more people began to comment on the fact that Lemaitre was a Catholic priest.  Lemaître follows two paths to the truth: The famous physicist tells why he finds no conflict between science and religion.    His view is interesting and important not because he is a Catholic priest, not because he is one of the leading mathematical physicists of our time, but because he is both.

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-  Lemaître was born in 1894 in Charleroi, Belgium. He was educated in Jesuit and Catholic schools, studying physics and mathematics. He was ordained as a priest in 1923 and in 1924 traveled to Britain, to Cambridge University, where he studied under Eddington.

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-  He then went to the US and earned a PhD in physics from the Massachusetts Institute of Technology. In 1925 he returned to Belgium as a lecturer at the Catholic University of Louvain, near Brussels. He continued teaching and writing until his death in 1966.

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-  Lemaître and the primeval-atom Universe and the “big bang theory”.

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-  In 2018, half a century after Lemaître’s death, what was known as the Hubble Law describing how galaxies move away from each other was renamed the Hubble Lemaître Law.

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-   Today, the consensus among scientists, astronomers and cosmologists is that the Universe as we know it was created in a massive explosion that not only created the majority of matter, but the physical laws that govern our ever-expanding universe.

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-

-  The basics of this Big Gang Theory are fairly simple. In short, the Big Bang hypothesis states that all of the current and past matter in the Universe came into existence at the same time,  13,800,000,000  years ago.

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-   At this time, all matter was compacted into a very small ball with infinite density and intense heat called a “Singularity“.   The Singularity began expanding, and the universe as we know it began.

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-  While this is not the only modern theory of how the Universe came into being.  There is the “Steady State Theory” or the “Oscillating Universe Theory“.  Not only does the model explain the origin of all known matter, the laws of physics, and the large scale structure of the Universe, it also accounts for the expansion of the Universe and a broad range of other phenomena.

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-  Working backwards from the current state of the Universe, scientists have theorized that it must have originated at a single point of infinite density and finite time that began to expand. 

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-  After the initial expansion, the theory maintains that Universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies.

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-  This all began roughly 13.8 billion years ago, and is thus considered to be the age of the universe. 

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-    The earliest times of the Universe, lasting from approximately 10^-43 to 10^-11 seconds after the Big Bang are the subject of extensive speculation. Given that the laws of physics as we know them could not have existed at this time, it is difficult to fathom how the Universe could have been governed. 

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-    The Planck Era was the earliest known period of the Universe. At this time, all matter was condensed on a single point of infinite density and extreme heat. During this period, it is believed that the quantum effects of gravity dominated physical interactions and that no other physical forces were of equal strength to gravitation.

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-  This Planck period of time extends from point 0 to approximately 10^-43 seconds, and is so named because it can only be measured in “Planck time“. Due to the extreme heat and density of matter, the state of the universe was highly unstable. It thus began to expand and cool, leading to the manifestation of the fundamental forces of physics.

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-  From 10^-43 second and 10^-36, the universe began to cross transition temperatures. It is here that the fundamental forces that govern the Universe are believed to have began separating from each other. The first step in this was the force of gravitation separating from gauge forces, which account for strong and weak nuclear forces and electro-magnetism.

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-  Then, from 10^-36 to 10^-32 seconds after the Big Bang, the temperature of the universe was low enough, 1028 Kelvin, that the forces of electromagnetism (strong force) and weak nuclear forces (weak interaction) were able to separate as well, forming two distinct forces.

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-  With the creation of the first fundamental forces of the universe, the Inflation Epoch began, lasting from 10^-32 seconds in Planck time to an unknown point. Most cosmological models suggest that the Universe at this point was filled homogeneously with a high-energy density, and that the incredibly high temperatures and pressure gave rise to rapid expansion and cooling.

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-  This began at 10^-37 seconds, where the phase transition that caused for the separation of forces also led to a period where the universe grew “exponentially“. It was also at this point in time that baryogenesis occurred, which refers to a hypothetical event where temperatures were so high that the random motions of particles occurred at relativistic speeds.

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-  As a result of this, particle–antiparticle pairs of all kinds were being continuously created and destroyed in collisions, which led to the predominance of matter over antimatter in the present universe. 

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-  After inflation stopped, the universe consisted of a quark–gluon plasma, as well as all other elementary particles. From this point onward, the Universe began to cool and matter coalesced and formed.

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-  As the universe continued to decrease in density and temperature, the energy of each particle began to decrease and phase transitions continued until the fundamental forces of physics and elementary particles changed into their present form. 

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-  About 10^-11 seconds after the Big Bang, particle energies dropped considerably. At about 10^-6 seconds, quarks and gluons combined to form baryons such as protons and neutrons, and a small excess of quarks over antiquarks led to a small excess of baryons over antibaryons.

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-  Since temperatures were not high enough to create new proton-antiproton pairs (or neutron-anitneutron pairs), mass annihilation immediately followed, leaving just one in 10^10 of the original protons and neutrons and none of their antiparticles.

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-   A similar process happened at about 1 second after the Big Bang for electrons and positrons. After these annihilations, the remaining protons, neutrons and electrons were no longer moving relativistic and the energy density of the universe was dominated by photons and to a lesser extent, neutrinos.

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-  A few minutes into the expansion, the period known as Big Bang “nucleosynthesis” also began. Thanks to temperatures dropping to 1 billion Kelvin and the energy densities dropping to about the equivalent of air, neutrons and protons began to combine to form the universe's first deuterium and helium atoms. However, most of the Universe's protons remained uncombined as hydrogen nuclei.

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-  After about 379,000 years, electrons combined with these nuclei to form atoms, mostly hydrogen, while the radiation decoupled from matter and continued to expand through space, largely unimpeded. 

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-  This radiation is now known to be what constitutes the “Cosmic Microwave Background” (CMB), which today is the oldest light in the Universe.  As the CMB expanded, it gradually lost density and energy, and is currently estimated to have a temperature of:

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---------------- 2.7260 ± 0.0013 Kelin  and an energy density of 0.25 eV/cm3

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---------------    (  4.005×10-14 Joules/meter^3;              400–500 photons/cm3). 

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-  The CMB can be seen in all directions at a distance of roughly 13.8 billion light years, but estimates of its actual distance place it at about 46 billion light years from the center of the Universe.

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-  Over the course of the several billion years that followed, the slightly denser regions of the almost uniformly distributed matter of the Universe began to become gravitationally attracted to each other. They therefore grew even denser, forming gas clouds, stars, galaxies, and the other astronomical structures that we regularly observe today.

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-  This is what is known as the “Structure Epoch“, since it was during this time that the modern Universe began to take shape. This consists of visible matter distributed in structures of various sizes, ranging from stars and planets to galaxies, galaxy clusters, and super clusters, where matter is concentrated, that are separated by enormous gulfs containing few galaxies.

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-  In this model, cold dark matter is estimated to make up about 23% of the matter/energy of the universe, while baryonic matter makes up about 4.6%.   Baryonic Matter is everything we know and see.  It is only 4.6% of this Universe!

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-  The “Cosmological Constant“, a theory originally proposed by Albert Einstein that attempted to show that the balance of mass-energy in the universe was static. In this case, it is associated with “Dark Energy“, which served to accelerate the expansion of the universe and keep its large-scale structure largely uniform.

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-   If the Universe began as a tiny point of infinite density that started to expand, does that mean it will continue to expand indefinitely? Or will it one day run out of expansive force, and begin retreating inward until all matter crunches back into a tiny ball again?

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-  In this "Big Crunch" scenario, the universe will reach a maximum size and then begin to collapse in on itself. This will only be possible if the mass density of the Universe is greater than the “critical density“. In other words, as long as the density of matter remains at or above a certain value (1 to 3 ×10^-26 kg of matter per meter^3), the Universe will eventually contract.

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-  Alternatively, if the density in the universe were equal to or below the critical density, the expansion would slow down but never stop. In this scenario, known as the "Big Freeze", the Universe would go on until star formation eventually ceased with the consumption of all the interstellar gas in each galaxy. Meanwhile, all existing stars would burn out and become white dwarfs, neutron stars, and blackholes.

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-  Very gradually, collisions between these blackholes would result in mass accumulating into larger and larger blackholes. The average temperature of the universe would approach absolute zero, and blackholes would evaporate after emitting the last of their “Hawking radiation“. Finally, the entropy of the universe would increase to the point where no organized form of energy could be extracted from it.

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-   Dark Energy theories suggest that ultimately galaxy clusters, stars, planets, atoms, nuclei, and matter itself will be torn apart by the ever-increasing expansion. This scenario is known as the "Big Rip", in which the expansion of the Universe itself will eventually be its undoing.

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-  History of the Big Bang Theory occurred as a result of deep-space observations conducted in the early 20th century. In 1912, American astronomer Vesto Slipher conducted a series of observations of spiral galaxie and measured their Doppler Redshift. In almost all cases, the spiral galaxies were observed to be moving away from our own.

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-  In 1922, Russian cosmologist Alexander Friedmann developed what are known as the Friedmann equations, which were derived from Einstein's equations for general relativity. Contrary to Einstein's which was advocating at the time with his a Cosmological Constant, Friedmann's work showed that the universe was likely in a state of expansion.

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-  In 1924, Edwin Hubble's measurement of the great distance to the nearest spiral nebula showed that these systems were indeed other galaxies. At the same time, Hubble began developing a series of distance indicators using the 100-inch Hooker telescope at Mount Wilson Observatory. And by 1929, Hubble discovered a correlation between distance and recession velocity which is now known as “Hubble's law“.

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-  And then in 1927, Georges Lemaitre independently derived the same results as Friedmann's equations and proposed that the inferred recession of the galaxies was due to the expansion of the universe. 

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-  In 1931, Lemaitre took this further, suggesting that the current expansion of the Universe meant that the father back in time one went, the smaller the Universe would be. At some point in the past the entire mass of the universe would have been concentrated into a single point from which the very fabric of space and time originated.

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-  These discoveries triggered a debate between physicists throughout the 1920s and 30s, with the majority advocating that the universe was in a steady state. In this model, new matter is continuously created as the universe expands, thus preserving the uniformity and density of matter over time.

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-   Papers submitted by Stephen Hawking and other physicists showed that singularities were an inevitable initial condition of general relativity and a Big Bang model of cosmology. In 1981, physicist Alan Guth theorized of a period of rapid cosmic expansion , "Inflation", that resolved other theoretical problems.

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-  The 1990s saw the rise of Dark Energy as an attempt to resolve outstanding issues in cosmology. In addition to providing an explanation as to the universe's missing mass (along with Dark Matter, originally proposed in 1932 by Jan Oort), it also provided an explanation as to why the universe is still accelerating, as well as offering a resolution to Einstein's Cosmological Constant.

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-  Significant progress was made thanks to advances in telescopes, satellites, and computer simulations, which have allowed astronomers and cosmologists to see more of the universe and gain a better understanding of its true age. 

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-  In the 2020’s  cosmologists have fairly precise and accurate measurements of many of the parameters of the Big Bang model, not to mention the age of the Universe itself. 

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-  And it all began with the noted observation that massive stellar objects, many light years distant, were slowly moving away from us. And while we still are not sure how it will all end, we do know that on a cosmological scale, that won't be for a long, LONG time!

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-  September 15, 2021   BIG  BANG  THEORY  -  what does it mean?     3272                                                                                                                                                    

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--------------------- ---  Thursday, September 16, 2021  ---------------------------

3276 - COMET - Bernardinelli-Bernstein”.

  -  3276   -   COMET  -  Bernardinelli-Bernstein”.  This comet was the largest such icy body identified to date, perhaps more than 100 miles across. It sprouted a tail when it was remarkably far from the sun.  

------------------------------------  comet 67P

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---------------------  3276  -   COMET  -  Bernardinelli-Bernstein”.  

- Trans-Neptunian objects (TNOs) are hunks of rock that circle the sun but remain out beyond Neptune's orbit. That's about 30 times the Earth's average distance from the sun, which is about 93 million miles and which scientists call an astronomical unit, AU. But most TNOs never stray farther from the sun than a few hundred AUs.

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-  The researchers spotted Comet Bernardinelli-Bernstein in data called the “Dark Energy Survey (DES)”, which ran on a telescope at the Cerro Tololo Inter-American Observatory in Chile from 2013 to 2019.

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-  The Dark Energy Survey was a survey designed to help scientists understand “dark energy“, a mysterious substance that scientists have not yet seen directly but is believed to make up 68% of the universe and warps our view of other galaxies. 

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-The DES project captured more than 80,000 images of the sky, revisiting specific patches about every two weeks. In each image are tens of thousands of cosmic objects of all shapes and sizes.

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-  A supercomputer software was designed in a way to spot TNOs within the Dark Energy Survey images. Using the time and location of each image to stack up solar system views, the researchers set the algorithm to identify when at least seven different images lined up to show a speck moving according to the laws that govern the movement of solar system objects.

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-    Based on the object's brightness and distance, the scientists initially estimated that this comet's nucleus, the icy rock at its core, was 60 to 120 miles wide.

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-  Since scientists know of plenty of TNOs of that size, but as far as comets go, that size estimate is truly massive. Among the comets scientists have studied in detail, only two are in the same class: Comet Hale-Bopp, which made a close approach to Earth in 1997, and Comet C/2002 VQ94 (LINEAR), which came no deeper into the solar system than Jupiter's orbit.

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-  Large comets are rare because they vaporize ice that makes them so spectacular to see robs them of their being.   Every pass by the sun leaves the comet a little bit smaller than before. 

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-  The history of our young solar system sported a ring of small, icy rubble surrounding the massive planets. But when the planets migrated through the solar system, their huge gravity kicked the frozen rubble around.  Some flew out into interstellar space; some ended up in what scientists call the “Kuiper Belt“, where Pluto orbits.

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-   Some ended up in the much more distant “Oort Cloud” where comets like Bernardinelli-Bernstein lurk. From there, as tides flow through the Milky Way and neighboring stars pass our solar system, gravity occasionally kicks a snowball inward. 

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-  There are plenty of Kuiper Belt objects that look like the new comet.  Scientists turned their telescopes to the object's modern location and combed through archival data to rescue sightings that were missed in original analysis. And in those objects, it was clear that Comet Bernardinelli-Bernstein wasn't fully frozen and had already woken up a little by the time it first appeared in scientists' images.

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-  Comets grow their distinctive fuzzy comas when their ices warm up enough to vaporize away into a gaseous cloud surrounding the nucleus. The phenomena obscures the nucleus and brightens the comet, which means that if Comet Bernardinelli-Bernstein was active in even the earliest sightings, scientists had overestimated its size.

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-     Observations of Comet Bernardinelli-Bernstein gathered by an outpost of the Las Cumbres Observatory in South Africa in June, 2021, show activity on the comet despite its huge distance from the sun.

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-  Calculating the size of an active comet is much more complicated than measuring a bare nucleus.  Scientists have only spotted a handful of comets active so far away from the sun, where temperatures are still too cold for water ice to turn to vapor, a typical type of comet activity. 

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-  Given a 2021 discovery and a 2031 close approach to the sun, plus old observations from as early as 2010,  scientists have a decades-long look at the object that's rare for this class of comet that makes such long journeys.

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-  September 15, 2021     COMET  -  Bernardinelli-Bernstein”.           3276                                                                                                                                                    

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

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--------------------- ---  Wednesday, September 15, 2021  ---------------------------

3277 - TIME - crystals move time backwards?

  -  3277   -   TIME  -  crystals move time backwards?  -  Researchers working in partnership with Google may have just used the tech giant's quantum computer to create a completely new phase of matter, a time crystal. 

---------------------  3277  -   TIME  -  crystals move time backwards?

-  Researchers working in partnership with Google may have just used the tech giant's quantum computer to create a completely new phase of matter, a time crystal. 

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-  With the ability to forever cycle between two states without ever losing energy, time crystals dodge one of the most important laws of physics.   The “second law of thermodynamics” states that the disorder, or entropy, of an isolated system must always increase. These bizarre time crystals remain stable, resisting any dissolution into randomness, despite existing in a constant state of flux. 

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-  In 2021 scientists were able to create the time crystal for roughly 100 seconds using qubits (quantum computing version of the traditional computer bit) inside the core of Google's Sycamore quantum processor. 

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-  The existence of this weird new matter phase, and the entirely new realm of physical behaviors it reveals, is incredibly exciting to physicists, especially as time crystals were only first predicted to exist just nine years ago.

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-  Time crystals are fascinating objects to physicists because they essentially sidestep the second law of thermodynamics, one of the most ironclad laws in physics. It states that entropy (a rough analog for the amount of disorder in a system) always increases. If you want to make something more ordered, you need to put more energy into it. 

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-  This tendency for disorder to grow explains a lot of things, such as why it's easier to stir ingredients into a mixture than it is to separate them out again.   It also sets the arrow of time, with the past universe always more ordered than the present; watching a video in reverse is likely to look strange to you primarily because you're witnessing the counterintuitive reversal of this entropic flow. 

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-  The second law of thermodynamics says that all systems evolve toward a state of more disorder, where energy is shared out evenly across the system.

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- Time crystals don't follow this rule. Instead of slowly approaching thermal equilibrium , "thermalizing",  so that their energy or temperature is equally distributed throughout their surroundings, they get stuck between two energy states above that equilibrium state, cycling back and forth between them indefinitely. 

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-   Qubits can be either a 1 or a 0,  the two possible positions in a two-state system, or a weird mix of the probabilities of both states called a “superposition“. What is weird about time crystals is that no amount of shaking, or zapping from one state to another, can move the time crystal's qubits into the lowest energy state, which is a random configuration; they can only flip it from its starting state to its second state, then back again. 

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-   It doesn't end up looking random, it just gets jammed stuck. It's like it remembers what it looked like initially, and it repeats that pattern over time.

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-  In this sense, a time crystal is like a pendulum that never stops swinging.  Even if you totally physically isolate a pendulum from the universe, so there's no friction and no air resistance, it will eventually stop. 

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-  In fact, there's no way for a large-scale object to behave like a time crystal without sounding absurd, because the only rules that enable time crystals to exist are the spooky and surreal rules that govern the world of the very small, ie: quantum mechanics. 

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-  In the quantum world, objects behave both like point particles and little waves at the same time, with the magnitude of these waves in any given region of space representing the probability of finding a particle at that location.

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-   But randomness such as random defects in a crystal's structure or a programmed randomness in the interaction strengths between qubits can cause a particle's probability wave to cancel itself out everywhere apart from one very small region. Rooted in place, unable to move, change states or thermalize with its surroundings, the particle becomes localized.

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-  A time crystal was a phase of matter. For something to be considered a phase, it usually has to be very stable in the face of fluctuations. Solids will not melt if the temperatures around them vary slightly; neither will slight fluctuations cause liquids to evaporate or freeze suddenly.

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-   In the same way, if the microwave beam used to flip the qubits between states was adjusted to be close to but slightly off from the exact 180 degrees needed for a perfect flip, the qubits still nonetheless flipped to the other state.

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-  Another hallmark of moving from one phase to another is the breaking of physical symmetries, the idea that the laws of physics are the same for an object at any point in time or space. 

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-  As a liquid, the molecules in water follow the same physical laws at every point in space and in every direction, but cool water down enough so that it transforms into ice and its molecules will pick regular points along a crystal structure, or lattice, to arrange themselves across. Suddenly, the water molecules have preferred points in space to occupy, and they leave the other points empty, the spatial symmetry of the water has been spontaneously broken.

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-  In much the same way that ice becomes a crystal in space by breaking with spatial symmetry, time crystals become crystals in time by breaking with time symmetry. At first, before their transformation into the time crystal phase, the row of qubits will experience a continuous symmetry between all moments in time.

-

-   But the periodic cycle of the microwave beam chops the constant conditions experienced by the qubits down into discrete packets making the symmetry imposed by the beam a discrete time-translation symmetry. 

-

-  By flipping back and forth at twice the period of the wavelength of the beam, the qubits break with the discrete time-translation symmetry imposed by the laser. They are the first objects we know of that are able to do this.

-

-  All of this weirdness makes time crystals rich in new physics.   Google's quantum computer needs to be perfectly isolated from its environment to prevent its qubits from undergoing a process called decoherence, which eventually breaks down the quantum localization effects, destroying the time crystal. 

-

-  The researchers are working on ways to better isolate their processor and mitigate the impact of decoherence, but it's unlikely they will eliminate the effect for good.

-

-  Numerous other projects have succeeded in making what convincingly appear to be time crystals in other ways, with diamonds, helium-3 superfluids, quasiparticles called magnons and with Bose-Einstein condensates, for the most part the crystals produced in these setups dissipate too quickly for detailed study.

-

-  The theoretical newness of the crystals is in some ways a double-edged sword, as physicists currently struggle to find clear applications for them.  They could be used as highly accurate sensors. Other proposals include using the crystals for better memory storage or for developing quantum computers with even faster processing power.

-

-  The greatest application of time crystals may already be here: They allow scientists to probe the boundaries of quantum mechanics.  

-

-  September 14, 2021      TIME  -  crystals move time backwards?      3277                                                                                                                                                    

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

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--------------------- ---  Wednesday, September 15, 2021  ---------------------------

3278 - SUN - Solar Flares, are we prepared?

  -  3278    -  SUN  -  Solar Flares, are we prepared?  A severe solar storm could plunge the world into an "internet apocalypse" that keeps large swaths of society offline for weeks or months at a time.  When the next big solar storm does blast out of our star, people on Earth will have about 13 hours to prepare for its arrival.

---------------------  3278 -   SUN  -  Solar Flares, are we prepared?

-  The sun is always showering Earth with a mist of magnetized particles known as “solar wind‘.   Our planet's magnetic shield blocks this electric wind from doing any real damage to Earth or its inhabitants, instead sending those particles toward the poles and leaving behind an aurora in their wake.

-

-  But sometimes, every century or so, that wind escalates into a full-blown solar storm,  and, the results of such extreme “space weather” could be catastrophic to our modern way of life.

-

-  A severe solar storm could plunge the world into an "internet apocalypse" that keeps large swaths of society offline for weeks or months at a time.

-

-  With the Corona Virsus pandemic we saw how unprepared the world was. There was no protocol to deal with it effectively, and it's the same with internet resilience.  Our infrastructure is not prepared for a large-scale solar event.

-

-  Part of the problem is that extreme solar storms, ie: “coronal mass ejections“, are relatively rare; scientists estimate the probability of an extreme space weather directly impacting Earth to be between 1.6% to 12% per decade.

-

-  In recent history, only two such storms have been recorded, one in 1859 and the other in 1921. The earlier incident, known as the “Carrington Event“, created such a severe geomagnetic disturbance on Earth that telegraph wires burst into flame, and auroras, usually only visible near the planet's poles, were spotted near equatorial Colombia. Smaller storms can also pack a punch; one in March 1989 blacked out the entire Canadian province of Quebec for nine hours.

-

-  Since then, human civilization has become much more reliant on the global internet, and the potential impacts of a massive geomagnetic storm on that new infrastructure remain largely unstudied.

-

-  The good news is, local and regional internet connections are likely at low risk of being damaged because fiber-optic cables themselves aren't affected by geomagnetically induced currents. 

-

-  However, the long undersea internet cables that connect continents are a different story. These cables are equipped with repeaters to boost the optical signal, spaced at intervals of roughly 30 to 90 miles. These repeaters are vulnerable to geomagnetic currents, and entire cables could be made useless if even one repeater goes offline.

-

-  If enough undersea cables fail in a particular region, then entire continents could be cut off from one another.

-

-   What's more, nations at high latitudes, such as the U.S. and the U.K., are far more susceptible to solar weather than nations at lower latitudes. In the event of a catastrophic geomagnetic storm, it's those high-latitude nations that are most likely to be cut off from the network first. It's hard to predict how long it would take to repair underwater infrastructure.  Large-scale internet outages lasting weeks or months are possible.

-

-  In the meantime, millions of people could lose their livelihoods.  The economic impact of an Internet disruption for a day in the US is estimated to be over $7 billion.   What if the network remains non-functional for days or even months?

-

-  Grid operators need to start taking the threat of extreme solar weather seriously as global internet infrastructure inevitably expands. Laying more cables at lower latitudes is a good start  as is developing resilience tests that focus on the effects of large-scale network failures. 

-

-  When the next big solar storm does blast out of our star, people on Earth will have about 13 hours to prepare for its arrival.

-

-  September 15, 2021       SUN  -  Solar Flares, are we prepared       3278                                                                                                                                                    

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

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

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

--------------------- ---  Wednesday, September 15, 2021  ---------------------------

3273 - UNIVERSE - how did it all begin?

  -  3273   -  UNIVERSE  -  how did it all begin?   The Big Bang wasn’t the beginning of time and space, and cosmic inflation, which preceded it, cannot be the beginning either, unless it went on for an eternity. After a century of cosmic revolutions, we’re right back where we started: unable to answer the most fundamental question we can ask, “how did it all begin?”

---------------------  3273  -   UNIVERSE  -  how did it all begin?

-  Most of us are perfectly willing to extrapolate the phenomena we see back in time in an unbroken chain of cause-and-effect events.  However, this didn’t go back in an infinite chain, but rather there was a “first cause” that led to the very existence of the Universe.

-

-   For a long time, this picture was supported by the notion of the classical Big Bang, which seemed to imply that the Universe began from a “singularity“: an infinitely hot and dense state from which space and time emerged out of “nothing“.  

-

-  The Big Bang was the start of our Universe as we know it, but not of space and time themselves. The Big Bang was just another “effect“  We think we know what caused the Big Bang. It reopens the question of whether the Universe had a beginning at all, and the answer so far is that we aren’t sure. 

-

-  The first observation of the cosmic redshift which were receding spectral lines of light

First noted by Vesto Slipher in 1917.  The Big Bang, originally, was an idea that attempted to explain this expanding Universe we observed based on two pieces of evidence:

-

--------------------  the demonstrated validity of our current theory of gravity, that is General Relativity, 

-

-------------------  the observed fact that the more distant a galaxy was observed to be from us, on average, the greater the amount its light appeared to be “redshifted” before arriving at our eyes.

-

-  General Relativity implied certain inevitable consequences. One of them was that the Universe could not be evenly, uniformly filled with matter and remain stable; a static, matter-filled Universe would inevitably collapse into a blackhole.   Gravity says so.

-

-  A second one was that a Universe that was evenly filled, not merely with matter but any type of energy, would either expand or contract according to a particular set of physical rules. 

-

-  And third, that when the Universe expanded or contracted, the wavelength of any waves (including de Broglie waves, for matter particles) would also expand or contract by the exact same proportional amount.  As the fabric of the Universe expands, the wavelength of radiation stretches out lower less energy frequencies.

-

-  Putting these pieces of information together led to a phenomenal possibility. The more distant an object is from us, the longer it takes the light it emits to reach our eyes. If the Universe is expanding as the light travels through it, then the longer it takes that emitted light to complete the journey to our eyes, the greater the amount that light’s wavelength will lengthen due to the Universe’s expansion. And the farther away we look, the farther back in time we’re seeing.

-

-   At the greatest distances of all, we’re seeing the Universe as it was:

-

------------------------  earlier in time,

-

-----------------------  back when it was smaller, denser, and expanding faster,

-

-----------------------  when it was in a more uniform, less clumpy state.

-

-  The first person to realize this was Georges Lemaître in 1927. He put together some early distance-determining data from Edwin Hubble with Vesto Slipher’s spectroscopic observations showing the redshifted light from distant galaxies, and concluded that the Universe must be expanding today. 

-

-  If the universe is getting cooler, larger, and less dense today, then it must have been hotter, smaller, and denser in the past. Lemaître immediately extrapolated this as far as he could: to infinite temperatures and densities and an infinitesimal size. He called this initial state the “primeval atom,” and noted that space and time could have emerged from a state of non-existence from a singularity at the very beginning.

-

-   It wasn’t until the 1940s that George Gamow came along and uncovered the key predictions of this “Big Bang” scenario:

-

----------------   there would be a growing cosmic web over time,

-

----------------   preceded by an early era without any galaxies or stars: a cosmic dark ages,

-

----------------     before the dark ages, the Universe would have been so hot that neutral atoms couldn’t form, 

-

---------------    when the Universe cools enough, we should see that leftover background of radiation with a particular, blackbody spectrum,

-

---------------     even before that, the temperatures and densities should have allowed nuclear fusion, meaning that we should have a mix of hydrogen, helium, and other light elements and isotopes that could be precisely calculated using nuclear physics equations.

-

-  In the mid-1960s,  Bell Labs scientists Arno Penzias and Bob Wilson discovered that all-sky glow at just 3,000 Kelvin: what was initially called the “primeval fireball” and what’s known today as the “Cosmic Microwave Background“.

-

-  The three big puzzles that emerged in the aftermath of the Big Bang’s widespread acceptance were:

-

----------------------  The monopole problem: if the Universe got arbitrarily hot in the past, there should be high-energy relics from that very early state still remaining in our Universe, but none have ever been observed.

-

------------------------  The horizon problem: if the Universe began from an extremely hot, dense state, then there should be an upper limit to the size of structures and to the scale of uniformity in the Universe, but the observed scales of both are larger than the predicted limits.

-

-----------------------  The flatness problem: assuming the Universe came into existence with a certain density and a certain expansion rate, those rates must balance perfectly to avoid the Universe either immediately recollapsing or expanding into total, empty oblivion, yet there’s no explanation for this “perfect balance“.

-   The Universe was simply “born” with the properties we observe it to have: This line of thought sometimes applies, as it does in the case of our Solar System. Just like all of the 10^24 star systems in the observable Universe, ours was born from a protostar with a nebula and a disk around it, which then spawned planets, asteroids, and frozen, icy, outer bodies, leading to the system we inhabit today. Lots of chances will lead, inevitably, to some low-probability outcomes, like the emergence of intelligent life, on some of them.

-

-  But this approach relies on there being a large number of possible outcomes, all with their own likelihoods, and a large number of chances for those outcomes to occur. 

-

-  The other approach is frequently more fruitful: to search for a mechanism that could set up and give rise to the initial conditions we’ve observed. Such a mechanism needs to rise to the threefold challenges of reproducing all of the successes of the theory it’s attempting to supersede, of explaining the problems or puzzles the prevailing theory cannot, and of making testable predictions that are different from the pre-existing idea.

- 

-  40 years ago  the idea of “cosmic inflation” was introduced by Alan Guth and others including Alexei Starobinskii, Andrei Linde, Paul Steinhardt, and Andy Albrecht. 

 -

-  That inflation proposed that there was an epoch to the Universe prior to the hot Big Bang where space expanded differently from how it expands today. In a Universe filled with stuff, the expansion rate is directly proportional to the energy density of that “stuff,” whatever it is. 

-

-  That means if your Universe is filled with:

-

---------------------   matter, the expansion rate drops as the volume of the Universe increases, since matter’s energy density is the number of particles divided by the volume they occupy,

-

--------------------    radiation, the expansion rate drops extra compared to matter, since radiation’s energy density is the number of particles divided by their occupying volume divided by their wavelength, which stretches as the Universe expands,

-

-------------------  or a quantum field inherent to space, then both the expansion rate and the energy density remain constant, since space and the fields present within it cannot “dilute” as the Universe expands.

-

-  That was the big idea behind “inflation“: that the Universe was dominated by some form of energy inherent to space, that it underwent a period of exponential expansion, and that when the quantum field behind inflation decayed into matter-and-radiation, inflation came to an end and the Universe “reheated,” and the conditions that we identify with the hot Big Bang then arose.

-

-  How cosmic inflation solves the horizon, flatness, and monopole problems?

This possible solution was brilliant, but would it work? It took some substantial theoretical work to modify Guth’s original, promising idea until it could reproduce the Big Bang’s successes. 

-

-  It was immediately clear how it resolved the monopole, horizon, and flatness problems: 

-

--------------------  the Universe reached a maximum temperature at the end of inflation, preventing the “monopole problem”, 

-

-------------------   the Universe has larger-scale uniformity and structure than anticipated because inflation “stretched” various regions of space to larger scales that the traditional (non-inflationary) cosmic horizon,

-

--------------------   the Universe is flat, today, because inflation’s dynamics determined both the initial energy density and the initial expansion rate.

-

-  In addition, there were four new predictions that were made concerning cosmic inflation where the predictions differed from the hot Big Bang.

-

-------------------------  The Universe achieves a maximum temperature that’s orders of magnitude below the Planck scale.

-

------------------------  The Universe possesses an initial spectrum of fluctuations where the fluctuations are slightly stronger on large scales than small ones.

-

-----------------------  The Universe is born with imperfections that are 100% adiabatic and 0% isocurvature in nature.

-

-----------------------  The Universe should possess super-horizon fluctuations, exhibiting structure on cosmic scales that exceed the distance that light could have traveled since the Big Bang.

-

-  All four of these predictions have now been tested, and inflation, as compared to the non-inflationary hot Big Bang, is 4-for-4 in its successes.

-

-    If inflation did arise from a pre-existing state, then what was that state like? It could have arisen from a non-inflationary spacetime with a condition and then gave rise to the inflationary state that set up the hot Big Bang.

-

-   There is no information accessible to us in our visible Universe, that would allow us to determine how inflation arose, or even whether inflation arose at all. In fact, because of the relentless expansion of the Universe during inflation, it can take a region as small as the Planck length on all sides, the smallest possible size at which the laws of physics make sense, and that region will be stretched to larger than the presently observable Universe in under 10^-32 seconds.

-

-    This final fraction-of-a-second of inflation is the only interval that has any way of imprinting itself onto our Universe. Anything that occurred prior, including earlier phases of inflation, the beginning of inflation (if it had one), or whatever occurred previously, has been wiped clean from our Universe by the dynamics of inflation itself. 

-

-  The Big Bang wasn’t the beginning of time and space, and cosmic inflation, which preceded it, cannot be the beginning either, unless it went on for an eternity. After a century of cosmic revolutions, we’re right back where we started: unable to answer the most fundamental question we can ask, “how did it all begin?”

-

-  How did I get here?  What does it all mean?  How will it all end?

-

-  September 12, 2021         UNIVERSE  -  how did it all begin?        3273                                                                                                                                                    

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

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--------------------- ---  Tuesday, September 14, 2021  ---------------------------

3275 - GRAVITY WAVES - DeBroglie discovers waves -

  -  3275  -   GRAVITY  WAVES  -  DeBroglie discovers waves?  -  We need to perform an experiment that indicates General Relativity isn’t enough, and reveals a hint of the Universe’s theorized “quantum gravitational nature“. The dream of directly detecting gravitons is a much larger prize.   One that we expect to be far more impractically difficult to actually achieve.

-------------  3275  -   GRAVITY  WAVES  -  DeBroglie discovers waves

-   In 1924, a young French noble managed to turn quantum physics on its head, just as it was finding its feet. Even the most conservative physicists were beginning to accept the duality revolution: light is not only a wave, but also behaves like a beam of particles (photons), as Einstein had established with his explanation of the photoelectric effect, which earned him the Nobel Prize in 1921.

-

-  Then Louis de Broglie (15 August 1892 – 19 March 1987), a novice scientist whose first degree was in history, thought otherwise: what if particles also behaved like waves?

-

-   A century ago there were still questions as attractive as this, to which one might dedicate a doctoral thesis. And that is exactly what de Broglie did. After studying in depth for several years the bases of quantum physics established by Max Planck and Albert Einstein, he presented his thesis in 1924 with an important theoretical discovery: “electrons behave as waves and, not only that, all particles and objects are associated with matter waves“.

-

-  This is the “de Broglie Hypothesis“. Putting together Planck’s equations (quantization of energy: E = hν) and Einstein’s (special relativity: E = mc2), de Broglie calculated what the length of these matter waves associated with each particle would be, depending on its velocity and mass. 

-

-  According to de Broglie, “our whole world is quantum“, not just light, a conclusion so bold that it was immediately rejected by many physicists, and ignored by others.

-

-  Although in 1924 he presented his doctoral thesis the French physicist had already done other research, which had led him to clash with some of the most influential physicists of the moment. Not so with Einstein, who enthusiastically supported de Broglie’s conclusions, but even Einstein’s support was not enough to prove him right: his hypothesis had to be experimentally demonstrated.

-

-  If the electron were a particle that behaved like a wave, then it would have to show typical properties of waves, such as diffraction and interference. And then some very strange things would happen: for example, one electron would be able to traverse two different holes at the same time. This was demonstrated by the electron diffraction experiment of Davisson and Germer (1927), thus confirming the hypothesis of de Broglie.

-

-   Louis de Broglie succeeded in laying one of the pillars of quantum physics: the wave–particle duality, which states that waves can behave like particles and vice versa. From his idea of matter waves was born wave mechanics, the new formulation of quantum physics that Schrödinger developed to apply to atoms and molecules.

-

-   The wave properties of electrons was the basis for inventing the electron microscope (released in 1932), which allows us to see things much smaller than typical optical microscopes permit, because the wavelength of the electron is much shorter than that of photons of visible light.

-

-  The Universe, if you look at it closely and carefully enough, is fundamentally quantum in nature. If you try and divide matter up into smaller and smaller pieces, eventually you arrive at indivisible components that cannot be broken up any further. 

-

-  These particles interact by exchanging a specific type of quantum that couples to their various charges. Gluons mediate the “strong nuclear force“, interacting with particles that have a color charge. 

-

-  The W and Z bosons mediate the “weak nuclear force“, coupling to the particles that have weak hypercharge and isospins.

-

-   And the photon mediates the “electromagnetic force“, acting on particles with an electric charge.

-

-   Gravitation, though, might be the outlier as our theory of gravitation is classical General Relativity.  In theory, though, there should be a quantum counterpart, mediated by a hypothetical quantum particle known as the “graviton“. Only, is it possible to find out whether gravitons actually exist? 

-

-  The first quantum particle discovered was the photon: the quantum associated with light. While it’s true that photons mediate the electromagnetic force, the photons that do so are virtual: they provide us with a way of calculating the electromagnetic field that permeates all of space. That stands in contrast to real photons: the photons we can emit, absorb, and otherwise measure in our instruments and detectors.

-

-  Every time you see something, that’s a result of a photon exciting a molecule in the rods or cones present in the retinas of your eyes, which then stimulates an electrical signal to your brain, which interprets the set of data coming in and constructs an image of what you observed.

-

-   The act of ‘seeing” is an inherently quantum act, with each photon carrying a specific amount of energy that either will or won’t be absorbed by particular molecules. Although the photoelectric effect, first described by Einstein, was what demonstrated the quantum nature of light, it’s important to recognize that all light is quantum in nature.

-

-  Alternating expansion and contraction of space is due to passing gravitational waves.

We can describe many of the phenomena associated with light perfectly well by viewing light as a wave, however, and gravitation has what’s quickly become a well-known analogue: gravitational waves.

-

-   Just as a charged particle moving through an electromagnetic field will emit electromagnetic waves (in the form of photons), a mass moving through a region of curved spacetime (which is the analogue of a gravitational field) will emit gravitational radiation, or gravitational waves.

-

-  When the advanced “LIGO detectors’ began taking data in 2015, they quickly began discovering the strongest sources of gravitational radiation in the Universe in the frequency range that the interferometers were sensitive to merging blackholes. 

-

-  Over the past 5 years, 2015 - 2020, those detectors were upgraded, joined by the Virgo detector, and have to date discovered more than 50 total gravitational wave events. From merging blackholes to merging neutron stars to, quite possibly, neutron stars merging with blackholes, they’ve demonstrated that gravitational radiation is very real, and in agreement with Einstein’s predictions.

-

-  The big question then becomes, once we know gravitational waves are real, whether they exhibit wave-particle duality as well? In other words, just as photons exhibit wave-like properties but also particle-like, quantum properties, is the same thing true for gravitational waves? Is there a particle-like counterpart that this radiation is made of, with the tremendous amounts of energy carried by gravitational waves distributed into individual, discrete quanta?

-

-  It’s a compelling and eminently reasonable idea. Water waves, for example, are made of particles, even though they don’t appear that way. But if you were to float, say, a bunch of ping pong balls atop the surface of the water, you can get an idea for visualizing what’s truly occurring. 

-

-  Individual ping pong balls would move up-and-down, back-and-forth, etc., along the surface of the water, and you can imagine that the individual molecules along a wavy surface of water are doing something similar.

-

-   Even though there’s an awful lot we don’t yet know about gravitational waves, including whether they’re made of individual quanta or not, there are a lot of properties we have been able to discern:

-

-----------------------  gravitational waves do carry real, finite, measurable amounts of energy that can be deposited into detectors,

-

-----------------------  gravitational waves propagate at a specific speed through space, specifically, the speed of gravity, which differs from the speed of light by no more than 1 part in 10^15,

-

-----------------------  gravitational waves compress-and-expand the space they travel through in mutually perpendicular directions, which enables LIGO and Virgo to detect them,

-

-----------------------  and they ought to interfere with any other ripples in space both constructively and destructively, obeying the same rules that any other wave would obey.

-

-  They have already observed that gravitational waves, just like photons, do indeed stretch their wavelengths as they travel through the expanding Universe. As the background of the underlying space expands, so do the wavelengths of the gravitational waves we observe.

-

-  As the fabric of the Universe expands, the wavelengths of radiation get stretched as well.  But all of this would be true whether gravitation were purely classical in nature or whether there were a more fundamental quantum theory of gravity that Einstein’s General Relativity is only an approximation for. If it’s quantum, that implies that every gravitational wave we see, in analogy with every light wave that we see:

-

-----------------------  is made of a large number of quantum particles,

-

-----------------------  where each quantum has an inherently zero rest mass,

meaning that it propagates at the speed of light (which equals the speed of gravity).

-

-    There are a few properties that would be unique to gravitons: properties that it wouldn’t share with photons. One of them is that, owing to the nature of the theory of gravitation, the particle that mediates the gravitational force would have to have a spin of 2, rather than a spin of 1 like the photon.

-

-   Because it’s massless, its spin can only be +2 or -2; it can have no intermediate value. 

-

-  Additionally, gravitons would only interact through the gravitational force. They’d respond to any other quantum that had mass or carried energy, but they should be uncharged and would be unaffected under all of the other fundamental interactions.

-

-  All massless particles travel at the speed of light, irrespective of energy or wavelength, including the photon and gluon.

- 

-  One way that the Universe could surprise us would be if gravitons turned out to actually have a very tiny, non-zero rest mass. Just as many of the fundamental particles (even including some of the force-carrying bosons, such as the W-and-Z bosons from the weak interactions) have a finite mass inherent to them, it’s possible that a graviton might as well. 

-

-  From our current gravitational wave measurements, however, and the energy received by our detectors, we’ve constrained the graviton’s mass to be mind-bogglingly tiny. If it does have a mass, it’s got to be less than 1.6 × 10^-22 eV/c2, or some 10^28 times lighter than the electron.

-

-    The key place to look for gravitons, or a signature of the “particle” part of the nature of these gravitational waves that we’ve demonstrated exist, would be where quantum gravitational effects are anticipated to be strongest and most pronounced: at the shortest distance scales and where gravitational fields are strongest. There’s no better place in the Universe to probe this regime than where two blackholes merge, as close to their singularities as you can conceivably get.

-

-  General Relativity is perfectly adequate, for all the blackholes expected to exist in our Universe, for describing the entirety of the effects that happen outside of a blackhole’s event horizon.

-

-  But when you get very close to a singularity, or specifically when two singularities merge together to create a different singularity, we anticipate that quantum effects may show up: quantum effects that signal a departure from the predictions of General Relativity. 

-

-  If we wanted to realistically do that, we’d have to be able to take data right around the exact moment the singularities merged, and we’d have to do it on extremely fast timescales. 

-

-  Today, LIGO is sensitive to events that occur on millisecond timescales, but if we could probe the Universe on sub-picosecond timescales, including at the very end of the inspiral phase, at the moment of the merger, and at the start of the subsequent ringdown phase , that might be possible.

-

-   We presently have laser pulses that hit the femtosecond or even attosecond timescales (10^-15 seconds to 10^-18 seconds), and with enough interferometers working at once, we might be sensitive enough to actually detect any signatures of quantum gravity.

-

-   Detecting the much sought-after B-modes predicted by cosmic inflation would indirectly demonstrate that gravitation is inherently quantum in nature, but there would be no direct detection of gravitons.

-

-   If you fired an electron through a double slit and could measure whether its gravitational field passed through both slits or just one, that would reveal whether gravity was quantum in nature or not, but, we wouldn’t detect gravitons.

-

-  Other schemes exist as well, and they’re very clever. If you passed photons of various wavelengths through a crystal and the “steps” the crystal moved were discrete instead of continuous, you could prove that space was quantized. 

-

-   If you brought masses into a quantum superposition of states and the energy levels were dependent on gravitational self-energy, you could determine whether gravity was quantized or not. And there are other potential signatures as well that could indirectly reveal whether gravity is inherently quantum in nature.

-

-    If we could demonstrate that gravity is inherently quantum in nature, that would be tremendous. If we could demonstrate that space is quantized, that would change how we view our reality. And if we could perform an experiment whose results disagreed with the straightforward predictions of General Relativity, that would spur us towards tremendous developments and new advances.

-

-  But none of that would be the same as demonstrating that gravitons actually exist, anymore than measuring the orbital decay of pulsing neutron stars demonstrated that gravitational waves really exist.  That discovery was consistent with everything we now think about gravitational waves. But it didn’t prove that gravitational waves existed; we needed direct detection for that. 

-

-  For right now, our next step should be to perform an experiment that indicates General Relativity isn’t enough, and reveals a hint of the Universe’s theorized quantum gravitational nature.

-

-   The dream of directly detecting gravitons is a much larger prize: one that we expect to be far more impractically difficult to actually achieve.  The everlasting mystery of “gravity”.

-

-  September 13, 2021     GRAVITY  WAVES  -  DeBroglie discovers waves      3275                                                                                                                                                    

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--------------------- ---  Tuesday, September 14, 2021  ---------------------------