Sull'Autore
George Musser is an award-winning journalist, a contributing editor for Scientific American, and the author of The Complete Idiot's Guide to String Theory. He is the recipient of a Jonathan Eberhart Planetary Sciences Journalism Award from the American Astronomical Society and an American Institute mostra altro of Physics Science Communication Award for Science Writing. He was a Knight Science Journalism Fellow at MIT and has appeared on Today, CNN, NPR, the BBC, Al Jazeera, and other outlets. He lives in Glen Ridge, New Jersey, with his wife and daughter. Follow him an Twitter at @ gmusser and visit his website at www.georgemusser.com. mostra meno
Opere di George Musser
Spooky Action at a Distance: The Phenomenon That Reimagines Space and Time--and What It Means for Black Holes, the Big… (2015) 208 copie
Putting Ourselves Back in the Equation: Why Physicists Are Studying Human Consciousness and AI to Unravel the Mysteries… (2023) 24 copie
Upiorne dzialanie na odleglosc i jego wplyw na czarne dziury, Wielki Wybuch i teorie wszystkiego (2018) 2 copie
Aveva ragione Einstein? 1 copia
Opere correlate
Etichette
Informazioni generali
- Nome canonico
- Musser, George
- Sesso
- male
- Premi e riconoscimenti
- National Magazine Award for Editorial Excellence (2002)
- Breve biografia
- George Musser is a staff editor and writer for Scientific American magazine in New York and the author of The Complete Idiot’s Guide to String Theory. He did his undergraduate studies in electrical engineering and mathematics at Brown University and his graduate studies in planetary science at Cornell University, where he was a National Science Foundation Graduate Fellow. His thesis work modeled mantle convection on Venus in order to explain broad plateaus, known as coronae, mapped by the Magellan orbiter. Musser served as editor of Mercury magazine and of the Universe in the Classroom tutorial series at the Astronomical Society of the Pacific, a science and science-education nonprofit based in San Francisco.
Utenti
Recensioni
Putting Ourselves Back in the Equation: Why… di George Musser
A splendid cornucopia of meaty ideas. After describing the structure of neural networks both natural and artificial, author Musser discusses two physics-of-the-mind theories, integrated information theory and predictive coding theory. The former is Giulio Tononi's well-known quantitative model of consciousness only, while the latter, previously unfamiliar to me, is introduced as "arguably the closest that neuroscientists have yet come to a grand unified theory of the mind" (p 67). Next, he provides a chapter on the notorious concept of alleged connections between consciousness and quantum mechanics (QM), wherein wavefunction collapse is either a cause or an effect. From this he is led to consider kinds of observer-dependent reality such as those in the Everettian (many-worlds), Rovellian (relational), and Fuchsian (QBist) QM interpretations. Continuing, he draws upon the domains of cosmology (citing ludicrous ideas like Boltzmann brains) and causation (reductionism vs emergentism, free will, agency theory) to argue that absence of the human element can make theories incomplete. His final numbered chapter is full of profound new ideas on time and space, too intricate for my powers of concise summarization.… (altro)
1 
fpagan | Feb 8, 2024 |
fpagan | Feb 8, 2024 | 
I've held off reviewing this book for ages.....mainly because it seemed so complex to review. Admittedly, I found parts of it extremely difficult to follow and that has contributed to my reluctant review. There are also a number of American colloquialisms that I had to guess at: eg. "Einstein blew off a lot of his classes"....was Einstein farting a lot in class or just missing a lot of classes?
Musser really focuses on the incompatibility of Bohr's descriptions with Einstein's. and "Like Einstein, Bell fretted that non locality defied the theory of relativity. Physicists can't give up quantum theory; it passes all experimental tests. For relativity to be wrong is equally unthinkable......Bell concluded 'We have an apparent incompatibility, at the deepest level, between the two fundamental pillars of contemporary theory". (Though most physicists didn't see the incompatibility or ignored it).
P9: Einstein "figured that that the world was in fact local and merely gave the impression of being non-local, and he sought a deeper mechanism whereby two particles can act in unison."
Quantum mechanics as expounded by Schrodinger proposed that ALL forms of energy and matter, not just light, can behave as both particle and wave. The Schrodinger equation does not describe a wave but a wave "function"....a curious mathematical abstraction that encodes the qualities of particles and systems of particles. The wave function is non-local.....even a single particle's wavefront spans the entire universe. Heisenberg...leaned towards a particle first theory and came up with his own set of equations. They proved to be mathematically equivalent to Schrodinger's.
Bohr's and Heisenbergs views evolved into the so-called Copenhagen Interpretation...that nature is essentially random and when a wave function collapses then a particle pops up in the "random" location.
Einstein objected to this interpretation....."The probability that THIS particle is found at a given point assumes an entirely peculiar mechanism of action at a distance, which prevents the wave continuously distributed in space from producing an action at two places". This action at a distance implies to my mind a contradiction with the postulates of relativity". To Einstein, the natural conclusion was that there wasn't any bubble that popped and left a particle behind. Bohr thought it enough that quantum mechanics provided "some mathematical methods which are adequate for the description of our experiments"...What more could anyone want?
Einstein responded with the famous EPR paper .......Bohr probably won the debate but a bit of a pyrrhic victory...really carried by Bohr's disciples.... and Einstein was only redeemed around 1989 by Arthur Fine's work. Musser is rather interesting about the "sociology of belief among physicists..."I began to realise that the failure to reach consensus is fascinating in its own right, a very human response to the depth of mysteries posed by quantum mechanics". Einstein posed the dilemma: quantum mechanics is either non-local or incomplete. Bell closed off the second possibility: he showed that not even incompleteness coud avoid non-locality
p132. Quantum field theory was the relativity-friendly, hence light-friendly, sequel to quantum mechanics. To develop it, Physicists in the 1920's and 1930's took two approaches, depending on whether they thought light is ultimately particle or wave. (Dirac, Feynman....were partial to particles....atoms can emit light by creating a photon and absorb light by destroying one. Classical electromagnetic waves are built up from "gobs" of photons......Pauli, gave primacy to waves...electromagnetic waves fill all the space around us......what we observe as particles are units of wave energy.
Both approaches seem to give the right answers but both left out gravity from quantum field theory. Both versions of the theory are "local".
p134. Hans Halvorson (a philosopher of physics) suggests that our world consists neither of particles nor of fields.....The particles that appear in the equations of quantum field theory are actually a type of wave. Such "particles" exist at no one location, but through the entire field, just as a note plucked on a guitar string ...spans the entire length...their only claim to the term "particle" is that they represent discrete chunks of energy and momentum.
On the other hand, "Quantum field theory specifies what a field does but not what it is."...."It definitely can't be an array of pixels".
Musser toys with various theories (which I just found confusing) about "super entanglement"...and "gravitational non-locality if space has a boundary"...without coming to any conclusions..... then morphs into a discussion of quantum gravity....giving some praise to Fotini Markopoulou's view that it must be a theory of the world ..not just the microword. He delves into theories of black holes ..without really drawing any conclusions relevant to the main story. And he delves into the idea that if a boundary and the volume of space are equivalent and can be collapsed .......then the boundary is the fundamental reality and the volume is derived from it; The "holographic principle".....p165. Musser trips lightly over the holographic principle with an aside about Juan Maldacena's paper about the duality of anti de Sitter (the interior of a higher dimensional ball)...like a bounded universe) and Conformal field Theory (meaning the surface of the ball). So, a realm governed by gravity (described by the general theory of relativity and its quantum elaboration) is equivalent to a realm governed only by non-gravitational forces (described by quantum field theory with gauge invariance). Maldacena's analysis therefore achieves the long-sought unification of these two branches physics. Though it seems to me that it begs the question whether space HAS a boundary. And Musser falls back on that rather lame excuse..."more research is needed".
p169. Spacetime is doomed: "Spacetime can't be fundamental," says the theorist Nima Arkani-hamed. "It has to come out of something more basic"......Nonlocality is no longer the mystery: it's the way things are, and locality becomes the puzzle.....And Musser attempts to synthesise these ideas about giving up on the space-time continuum. We can say that the world is ordered and space is a convenient notion for describing that order.
P173..Most attention has been given to space.........But time also plays a powerful organising role in the universe, and, as with space, this structure has two aspects...first it is hierarchical, (events can be closely related, distantly related etc. ..and second Time is an abstraction at which we arrive by means of the changes of things; made because all things are interconnected). He then looks at networks...like human networks as models of space; and matrix models with string theory. p190. Matrix models do have some peculiarities, but they establish a remarkable principle: a bunch of particles obeying quantum physics can organise themselves so that you'd swear they live and move within space, even if space wasn't in the original specification of the system. ..p192 "Quantum entanglement is the thing that is responsible for connecting up the spacetime into one piece (Mark van Raamsdonk);......"When we first encountered quantum entanglement, it seemed to transcend space. Today physicists think it might be what creates space" .
p194. Michael Heller advocates a concept called non commutative geometry, ...which takes a top-down view of physics, in which global structures...ones that span the entire universe ...are fundamental, and local geometric concepts such as "points" and "things" derive from those global structures, rather than the usual bottom up view in which the universe is built from zillions of localised things". "There are no points, no time instant". Heller says. Everything is global.
P195. Emergent-spacetime models also give us a new way to understand the big-bang. If space emerges from spaceless building blocks ...then the birth of the universes is no more inscrutable than the birth of a living creature. (I don't really follow his logic here; he talks of "matter and energy sloshing around the network, in a pre-bang epoch...and two galaxies on opposite sides of the sky separated by a gulf of space are unable to communicate with each other now. But at the dawn of time, there was no space and no gulf between them"......OK: but then there were no galaxies either). He mentions black holes without any conclusions that I could see. He suggests that spaces might even be nested like matryoshka dolls. But there are lots of criticisms about all these models which still work within the basic framework of quantum physics and general relativity. But, p200, "Notably the models presuppose time; they don't incorporate Leibnitz' and Mach's suggestion that time should emerge as surely as space does"..."Yet this separation of time and space runs counter to Einstein's great insight that the two are fundamentally inseparable".
p204. Heisenberg proposed to treat messy collisions as a black box: ....the s matrix. It worked well for a time but by the 1970's quantum field theory proved able to explain the nuclear forces the old-fashioned spatio-temporal way... and the s matrix was forgotten. Meanwhile Roger Penrose came up with the idea of twistors...built of light rays. The intersection of light rays gives you a point...a swirling pattern of light rays reproduces a spinning particle. Local structures in spacetime are encoded non-locally....but the idea didn't work..they didn't cast images in a mirror. However, a leading string theorist, Edward Witten, tried tying string theory and twistors together..and eventually a technique called "amplitudehedron" emerged. ..Basically you draw a polyhedron that captures the structure of a particle interaction....but so far it only works with highly idealised theories of nuclear forces.
A problem I have with all the above e "grab-bag" of theories that I don't know how seriously to take any of them. They all appear to have profound flaws yet Musser doesn't attempt to draw any conclusions..he just describes. I didn't find this very helpful. In fact, found it confusing and it made his book hard to follow.
p214...Musser seems to confound human relations and networks with space time networks. I think he takes the metaphor too far ...and essentially it become meaningless.
He concludes that "if it does turn out that space and time are the products of some deeper level of reality, who knows what new phenomena await our discovery ....dark matter and dark energy? faster than light travel?".
I was hoping for a more prescriptive ending. He runs us through masses of speculation ....seems to give a slight thumbs-up to string theory (though others have suggested it is a theory going nowhere and nothing can be falsified with string theory).
So in the end, a bit disappointing. Three and a half stars from me.… (altro)
Musser really focuses on the incompatibility of Bohr's descriptions with Einstein's. and "Like Einstein, Bell fretted that non locality defied the theory of relativity. Physicists can't give up quantum theory; it passes all experimental tests. For relativity to be wrong is equally unthinkable......Bell concluded 'We have an apparent incompatibility, at the deepest level, between the two fundamental pillars of contemporary theory". (Though most physicists didn't see the incompatibility or ignored it).
P9: Einstein "figured that that the world was in fact local and merely gave the impression of being non-local, and he sought a deeper mechanism whereby two particles can act in unison."
Quantum mechanics as expounded by Schrodinger proposed that ALL forms of energy and matter, not just light, can behave as both particle and wave. The Schrodinger equation does not describe a wave but a wave "function"....a curious mathematical abstraction that encodes the qualities of particles and systems of particles. The wave function is non-local.....even a single particle's wavefront spans the entire universe. Heisenberg...leaned towards a particle first theory and came up with his own set of equations. They proved to be mathematically equivalent to Schrodinger's.
Bohr's and Heisenbergs views evolved into the so-called Copenhagen Interpretation...that nature is essentially random and when a wave function collapses then a particle pops up in the "random" location.
Einstein objected to this interpretation....."The probability that THIS particle is found at a given point assumes an entirely peculiar mechanism of action at a distance, which prevents the wave continuously distributed in space from producing an action at two places". This action at a distance implies to my mind a contradiction with the postulates of relativity". To Einstein, the natural conclusion was that there wasn't any bubble that popped and left a particle behind. Bohr thought it enough that quantum mechanics provided "some mathematical methods which are adequate for the description of our experiments"...What more could anyone want?
Einstein responded with the famous EPR paper .......Bohr probably won the debate but a bit of a pyrrhic victory...really carried by Bohr's disciples.... and Einstein was only redeemed around 1989 by Arthur Fine's work. Musser is rather interesting about the "sociology of belief among physicists..."I began to realise that the failure to reach consensus is fascinating in its own right, a very human response to the depth of mysteries posed by quantum mechanics". Einstein posed the dilemma: quantum mechanics is either non-local or incomplete. Bell closed off the second possibility: he showed that not even incompleteness coud avoid non-locality
p132. Quantum field theory was the relativity-friendly, hence light-friendly, sequel to quantum mechanics. To develop it, Physicists in the 1920's and 1930's took two approaches, depending on whether they thought light is ultimately particle or wave. (Dirac, Feynman....were partial to particles....atoms can emit light by creating a photon and absorb light by destroying one. Classical electromagnetic waves are built up from "gobs" of photons......Pauli, gave primacy to waves...electromagnetic waves fill all the space around us......what we observe as particles are units of wave energy.
Both approaches seem to give the right answers but both left out gravity from quantum field theory. Both versions of the theory are "local".
p134. Hans Halvorson (a philosopher of physics) suggests that our world consists neither of particles nor of fields.....The particles that appear in the equations of quantum field theory are actually a type of wave. Such "particles" exist at no one location, but through the entire field, just as a note plucked on a guitar string ...spans the entire length...their only claim to the term "particle" is that they represent discrete chunks of energy and momentum.
On the other hand, "Quantum field theory specifies what a field does but not what it is."...."It definitely can't be an array of pixels".
Musser toys with various theories (which I just found confusing) about "super entanglement"...and "gravitational non-locality if space has a boundary"...without coming to any conclusions..... then morphs into a discussion of quantum gravity....giving some praise to Fotini Markopoulou's view that it must be a theory of the world ..not just the microword. He delves into theories of black holes ..without really drawing any conclusions relevant to the main story. And he delves into the idea that if a boundary and the volume of space are equivalent and can be collapsed .......then the boundary is the fundamental reality and the volume is derived from it; The "holographic principle".....p165. Musser trips lightly over the holographic principle with an aside about Juan Maldacena's paper about the duality of anti de Sitter (the interior of a higher dimensional ball)...like a bounded universe) and Conformal field Theory (meaning the surface of the ball). So, a realm governed by gravity (described by the general theory of relativity and its quantum elaboration) is equivalent to a realm governed only by non-gravitational forces (described by quantum field theory with gauge invariance). Maldacena's analysis therefore achieves the long-sought unification of these two branches physics. Though it seems to me that it begs the question whether space HAS a boundary. And Musser falls back on that rather lame excuse..."more research is needed".
p169. Spacetime is doomed: "Spacetime can't be fundamental," says the theorist Nima Arkani-hamed. "It has to come out of something more basic"......Nonlocality is no longer the mystery: it's the way things are, and locality becomes the puzzle.....And Musser attempts to synthesise these ideas about giving up on the space-time continuum. We can say that the world is ordered and space is a convenient notion for describing that order.
P173..Most attention has been given to space.........But time also plays a powerful organising role in the universe, and, as with space, this structure has two aspects...first it is hierarchical, (events can be closely related, distantly related etc. ..and second Time is an abstraction at which we arrive by means of the changes of things; made because all things are interconnected). He then looks at networks...like human networks as models of space; and matrix models with string theory. p190. Matrix models do have some peculiarities, but they establish a remarkable principle: a bunch of particles obeying quantum physics can organise themselves so that you'd swear they live and move within space, even if space wasn't in the original specification of the system. ..p192 "Quantum entanglement is the thing that is responsible for connecting up the spacetime into one piece (Mark van Raamsdonk);......"When we first encountered quantum entanglement, it seemed to transcend space. Today physicists think it might be what creates space" .
p194. Michael Heller advocates a concept called non commutative geometry, ...which takes a top-down view of physics, in which global structures...ones that span the entire universe ...are fundamental, and local geometric concepts such as "points" and "things" derive from those global structures, rather than the usual bottom up view in which the universe is built from zillions of localised things". "There are no points, no time instant". Heller says. Everything is global.
P195. Emergent-spacetime models also give us a new way to understand the big-bang. If space emerges from spaceless building blocks ...then the birth of the universes is no more inscrutable than the birth of a living creature. (I don't really follow his logic here; he talks of "matter and energy sloshing around the network, in a pre-bang epoch...and two galaxies on opposite sides of the sky separated by a gulf of space are unable to communicate with each other now. But at the dawn of time, there was no space and no gulf between them"......OK: but then there were no galaxies either). He mentions black holes without any conclusions that I could see. He suggests that spaces might even be nested like matryoshka dolls. But there are lots of criticisms about all these models which still work within the basic framework of quantum physics and general relativity. But, p200, "Notably the models presuppose time; they don't incorporate Leibnitz' and Mach's suggestion that time should emerge as surely as space does"..."Yet this separation of time and space runs counter to Einstein's great insight that the two are fundamentally inseparable".
p204. Heisenberg proposed to treat messy collisions as a black box: ....the s matrix. It worked well for a time but by the 1970's quantum field theory proved able to explain the nuclear forces the old-fashioned spatio-temporal way... and the s matrix was forgotten. Meanwhile Roger Penrose came up with the idea of twistors...built of light rays. The intersection of light rays gives you a point...a swirling pattern of light rays reproduces a spinning particle. Local structures in spacetime are encoded non-locally....but the idea didn't work..they didn't cast images in a mirror. However, a leading string theorist, Edward Witten, tried tying string theory and twistors together..and eventually a technique called "amplitudehedron" emerged. ..Basically you draw a polyhedron that captures the structure of a particle interaction....but so far it only works with highly idealised theories of nuclear forces.
A problem I have with all the above e "grab-bag" of theories that I don't know how seriously to take any of them. They all appear to have profound flaws yet Musser doesn't attempt to draw any conclusions..he just describes. I didn't find this very helpful. In fact, found it confusing and it made his book hard to follow.
p214...Musser seems to confound human relations and networks with space time networks. I think he takes the metaphor too far ...and essentially it become meaningless.
He concludes that "if it does turn out that space and time are the products of some deeper level of reality, who knows what new phenomena await our discovery ....dark matter and dark energy? faster than light travel?".
I was hoping for a more prescriptive ending. He runs us through masses of speculation ....seems to give a slight thumbs-up to string theory (though others have suggested it is a theory going nowhere and nothing can be falsified with string theory).
So in the end, a bit disappointing. Three and a half stars from me.… (altro)
I've held off reviewing this book for ages.....mainly because it seemed so complex to review. Admittedly, I found parts of it extremely difficult to follow and that has contributed to my reluctant review. There are also a number of American colloquialisms that I had to guess at: eg. "Einstein blew off a lot of his classes"....was Einstein farting a lot in class or just missing a lot of classes?
Musser really focuses on the incompatibility of Bohr's descriptions with Einstein's. and "Like Einstein, Bell fretted that non locality defied the theory of relativity. Physicists can't give up quantum theory; it passes all experimental tests. For relativity to be wrong is equally unthinkable......Bell concluded 'We have an apparent incompatibility, at the deepest level, between the two fundamental pillars of contemporary theory". (Though most physicists didn't see the incompatibility or ignored it).
P9: Einstein "figured that that the world was in fact local and merely gave the impression of being non-local, and he sought a deeper mechanism whereby two particles can act in unison."
Quantum mechanics as expounded by Schrodinger proposed that ALL forms of energy and matter, not just light, can behave as both particle and wave. The Schrodinger equation does not describe a wave but a wave "function"....a curious mathematical abstraction that encodes the qualities of particles and systems of particles. The wave function is non-local.....even a single particle's wavefront spans the entire universe. Heisenberg...leaned towards a particle first theory and came up with his own set of equations. They proved to be mathematically equivalent to Schrodinger's.
Bohr's and Heisenbergs views evolved into the so-called Copenhagen Interpretation...that nature is essentially random and when a wave function collapses then a particle pops up in the "random" location.
Einstein objected to this interpretation....."The probability that THIS particle is found at a given point assumes an entirely peculiar mechanism of action at a distance, which prevents the wave continuously distributed in space from producing an action at two places". This action at a distance implies to my mind a contradiction with the postulates of relativity". To Einstein, the natural conclusion was that there wasn't any bubble that popped and left a particle behind. Bohr thought it enough that quantum mechanics provided "some mathematical methods which are adequate for the description of our experiments"...What more could anyone want?
Einstein responded with the famous EPR paper .......Bohr probably won the debate but a bit of a pyrrhic victory...really carried by Bohr's disciples.... and Einstein was only redeemed around 1989 by Arthur Fine's work. Musser is rather interesting about the "sociology of belief among physicists..."I began to realise that the failure to reach consensus is fascinating in its own right, a very human response to the depth of mysteries posed by quantum mechanics". Einstein posed the dilemma: quantum mechanics is either non-local or incomplete. Bell closed off the second possibility: he showed that not even incompleteness coud avoid non-locality
p132. Quantum field theory was the relativity-friendly, hence light-friendly, sequel to quantum mechanics. To develop it, Physicists in the 1920's and 1930's took two approaches, depending on whether they thought light is ultimately particle or wave. (Dirac, Feynman....were partial to particles....atoms can emit light by creating a photon and absorb light by destroying one. Classical electromagnetic waves are built up from "gobs" of photons......Pauli, gave primacy to waves...electromagnetic waves fill all the space around us......what we observe as particles are units of wave energy.
Both approaches seem to give the right answers but both left out gravity from quantum field theory. Both versions of the theory are "local".
p134. Hans Halvorson (a philosopher of physics) suggests that our world consists neither of particles nor of fields.....The particles that appear in the equations of quantum field theory are actually a type of wave. Such "particles" exist at no one location, but through the entire field, just as a note plucked on a guitar string ...spans the entire length...their only claim to the term "particle" is that they represent discrete chunks of energy and momentum.
On the other hand, "Quantum field theory specifies what a field does but not what it is."...."It definitely can't be an array of pixels".
Musser toys with various theories (which I just found confusing) about "super entanglement"...and "gravitational non-locality if space has a boundary"...without coming to any conclusions..... then morphs into a discussion of quantum gravity....giving some praise to Fotini Markopoulou's view that it must be a theory of the world ..not just the microword. He delves into theories of black holes ..without really drawing any conclusions relevant to the main story. And he delves into the idea that if a boundary and the volume of space are equivalent and can be collapsed .......then the boundary is the fundamental reality and the volume is derived from it; The "holographic principle".....p165. Musser trips lightly over the holographic principle with an aside about Juan Maldacena's paper about the duality of anti de Sitter (the interior of a higher dimensional ball)...like a bounded universe) and Conformal field Theory (meaning the surface of the ball). So, a realm governed by gravity (described by the general theory of relativity and its quantum elaboration) is equivalent to a realm governed only by non-gravitational forces (described by quantum field theory with gauge invariance). Maldacena's analysis therefore achieves the long-sought unification of these two branches physics. Though it seems to me that it begs the question whether space HAS a boundary. And Musser falls back on that rather lame excuse..."more research is needed".
p169. Spacetime is doomed: "Spacetime can't be fundamental," says the theorist Nima Arkani-hamed. "It has to come out of something more basic"......Nonlocality is no longer the mystery: it's the way things are, and locality becomes the puzzle.....And Musser attempts to synthesise these ideas about giving up on the space-time continuum. We can say that the world is ordered and space is a convenient notion for describing that order.
P173..Most attention has been given to space.........But time also plays a powerful organising role in the universe, and, as with space, this structure has two aspects...first it is hierarchical, (events can be closely related, distantly related etc. ..and second Time is an abstraction at which we arrive by means of the changes of things; made because all things are interconnected). He then looks at networks...like human networks as models of space; and matrix models with string theory. p190. Matrix models do have some peculiarities, but they establish a remarkable principle: a bunch of particles obeying quantum physics can organise themselves so that you'd swear they live and move within space, even if space wasn't in the original specification of the system. ..p192 "Quantum entanglement is the thing that is responsible for connecting up the spacetime into one piece (Mark van Raamsdonk);......"When we first encountered quantum entanglement, it seemed to transcend space. Today physicists think it might be what creates space" .
p194. Michael Heller advocates a concept called non commutative geometry, ...which takes a top-down view of physics, in which global structures...ones that span the entire universe ...are fundamental, and local geometric concepts such as "points" and "things" derive from those global structures, rather than the usual bottom up view in which the universe is built from zillions of localised things". "There are no points, no time instant". Heller says. Everything is global.
P195. Emergent-spacetime models also give us a new way to understand the big-bang. If space emerges from spaceless building blocks ...then the birth of the universes is no more inscrutable than the birth of a living creature. (I don't really follow his logic here; he talks of "matter and energy sloshing around the network, in a pre-bang epoch...and two galaxies on opposite sides of the sky separated by a gulf of space are unable to communicate with each other now. But at the dawn of time, there was no space and no gulf between them"......OK: but then there were no galaxies either). He mentions black holes without any conclusions that I could see. He suggests that spaces might even be nested like matryoshka dolls. But there are lots of criticisms about all these models which still work within the basic framework of quantum physics and general relativity. But, p200, "Notably the models presuppose time; they don't incorporate Leibnitz' and Mach's suggestion that time should emerge as surely as space does"..."Yet this separation of time and space runs counter to Einstein's great insight that the two are fundamentally inseparable".
p204. Heisenberg proposed to treat messy collisions as a black box: ....the s matrix. It worked well for a time but by the 1970's quantum field theory proved able to explain the nuclear forces the old-fashioned spatio-temporal way... and the s matrix was forgotten. Meanwhile Roger Penrose came up with the idea of twistors...built of light rays. The intersection of light rays gives you a point...a swirling pattern of light rays reproduces a spinning particle. Local structures in spacetime are encoded non-locally....but the idea didn't work..they didn't cast images in a mirror. However, a leading string theorist, Edward Witten, tried tying string theory and twistors together..and eventually a technique called "amplitudehedron" emerged. ..Basically you draw a polyhedron that captures the structure of a particle interaction....but so far it only works with highly idealised theories of nuclear forces.
A problem I have with all the above e "grab-bag" of theories that I don't know how seriously to take any of them. They all appear to have profound flaws yet Musser doesn't attempt to draw any conclusions..he just describes. I didn't find this very helpful. In fact, found it confusing and it made his book hard to follow.
p214...Musser seems to confound human relations and networks with space time networks. I think he takes the metaphor too far ...and essentially it become meaningless.
He concludes that "if it does turn out that space and time are the products of some deeper level of reality, who knows what new phenomena await our discovery ....dark matter and dark energy? faster than light travel?".
I was hoping for a more prescriptive ending. He runs us through masses of speculation ....seems to give a slight thumbs-up to string theory (though others have suggested it is a theory going nowhere and nothing can be falsified with string theory).
So in the end, a bit disappointing. Three and a half stars from me.… (altro)
Musser really focuses on the incompatibility of Bohr's descriptions with Einstein's. and "Like Einstein, Bell fretted that non locality defied the theory of relativity. Physicists can't give up quantum theory; it passes all experimental tests. For relativity to be wrong is equally unthinkable......Bell concluded 'We have an apparent incompatibility, at the deepest level, between the two fundamental pillars of contemporary theory". (Though most physicists didn't see the incompatibility or ignored it).
P9: Einstein "figured that that the world was in fact local and merely gave the impression of being non-local, and he sought a deeper mechanism whereby two particles can act in unison."
Quantum mechanics as expounded by Schrodinger proposed that ALL forms of energy and matter, not just light, can behave as both particle and wave. The Schrodinger equation does not describe a wave but a wave "function"....a curious mathematical abstraction that encodes the qualities of particles and systems of particles. The wave function is non-local.....even a single particle's wavefront spans the entire universe. Heisenberg...leaned towards a particle first theory and came up with his own set of equations. They proved to be mathematically equivalent to Schrodinger's.
Bohr's and Heisenbergs views evolved into the so-called Copenhagen Interpretation...that nature is essentially random and when a wave function collapses then a particle pops up in the "random" location.
Einstein objected to this interpretation....."The probability that THIS particle is found at a given point assumes an entirely peculiar mechanism of action at a distance, which prevents the wave continuously distributed in space from producing an action at two places". This action at a distance implies to my mind a contradiction with the postulates of relativity". To Einstein, the natural conclusion was that there wasn't any bubble that popped and left a particle behind. Bohr thought it enough that quantum mechanics provided "some mathematical methods which are adequate for the description of our experiments"...What more could anyone want?
Einstein responded with the famous EPR paper .......Bohr probably won the debate but a bit of a pyrrhic victory...really carried by Bohr's disciples.... and Einstein was only redeemed around 1989 by Arthur Fine's work. Musser is rather interesting about the "sociology of belief among physicists..."I began to realise that the failure to reach consensus is fascinating in its own right, a very human response to the depth of mysteries posed by quantum mechanics". Einstein posed the dilemma: quantum mechanics is either non-local or incomplete. Bell closed off the second possibility: he showed that not even incompleteness coud avoid non-locality
p132. Quantum field theory was the relativity-friendly, hence light-friendly, sequel to quantum mechanics. To develop it, Physicists in the 1920's and 1930's took two approaches, depending on whether they thought light is ultimately particle or wave. (Dirac, Feynman....were partial to particles....atoms can emit light by creating a photon and absorb light by destroying one. Classical electromagnetic waves are built up from "gobs" of photons......Pauli, gave primacy to waves...electromagnetic waves fill all the space around us......what we observe as particles are units of wave energy.
Both approaches seem to give the right answers but both left out gravity from quantum field theory. Both versions of the theory are "local".
p134. Hans Halvorson (a philosopher of physics) suggests that our world consists neither of particles nor of fields.....The particles that appear in the equations of quantum field theory are actually a type of wave. Such "particles" exist at no one location, but through the entire field, just as a note plucked on a guitar string ...spans the entire length...their only claim to the term "particle" is that they represent discrete chunks of energy and momentum.
On the other hand, "Quantum field theory specifies what a field does but not what it is."...."It definitely can't be an array of pixels".
Musser toys with various theories (which I just found confusing) about "super entanglement"...and "gravitational non-locality if space has a boundary"...without coming to any conclusions..... then morphs into a discussion of quantum gravity....giving some praise to Fotini Markopoulou's view that it must be a theory of the world ..not just the microword. He delves into theories of black holes ..without really drawing any conclusions relevant to the main story. And he delves into the idea that if a boundary and the volume of space are equivalent and can be collapsed .......then the boundary is the fundamental reality and the volume is derived from it; The "holographic principle".....p165. Musser trips lightly over the holographic principle with an aside about Juan Maldacena's paper about the duality of anti de Sitter (the interior of a higher dimensional ball)...like a bounded universe) and Conformal field Theory (meaning the surface of the ball). So, a realm governed by gravity (described by the general theory of relativity and its quantum elaboration) is equivalent to a realm governed only by non-gravitational forces (described by quantum field theory with gauge invariance). Maldacena's analysis therefore achieves the long-sought unification of these two branches physics. Though it seems to me that it begs the question whether space HAS a boundary. And Musser falls back on that rather lame excuse..."more research is needed".
p169. Spacetime is doomed: "Spacetime can't be fundamental," says the theorist Nima Arkani-hamed. "It has to come out of something more basic"......Nonlocality is no longer the mystery: it's the way things are, and locality becomes the puzzle.....And Musser attempts to synthesise these ideas about giving up on the space-time continuum. We can say that the world is ordered and space is a convenient notion for describing that order.
P173..Most attention has been given to space.........But time also plays a powerful organising role in the universe, and, as with space, this structure has two aspects...first it is hierarchical, (events can be closely related, distantly related etc. ..and second Time is an abstraction at which we arrive by means of the changes of things; made because all things are interconnected). He then looks at networks...like human networks as models of space; and matrix models with string theory. p190. Matrix models do have some peculiarities, but they establish a remarkable principle: a bunch of particles obeying quantum physics can organise themselves so that you'd swear they live and move within space, even if space wasn't in the original specification of the system. ..p192 "Quantum entanglement is the thing that is responsible for connecting up the spacetime into one piece (Mark van Raamsdonk);......"When we first encountered quantum entanglement, it seemed to transcend space. Today physicists think it might be what creates space" .
p194. Michael Heller advocates a concept called non commutative geometry, ...which takes a top-down view of physics, in which global structures...ones that span the entire universe ...are fundamental, and local geometric concepts such as "points" and "things" derive from those global structures, rather than the usual bottom up view in which the universe is built from zillions of localised things". "There are no points, no time instant". Heller says. Everything is global.
P195. Emergent-spacetime models also give us a new way to understand the big-bang. If space emerges from spaceless building blocks ...then the birth of the universes is no more inscrutable than the birth of a living creature. (I don't really follow his logic here; he talks of "matter and energy sloshing around the network, in a pre-bang epoch...and two galaxies on opposite sides of the sky separated by a gulf of space are unable to communicate with each other now. But at the dawn of time, there was no space and no gulf between them"......OK: but then there were no galaxies either). He mentions black holes without any conclusions that I could see. He suggests that spaces might even be nested like matryoshka dolls. But there are lots of criticisms about all these models which still work within the basic framework of quantum physics and general relativity. But, p200, "Notably the models presuppose time; they don't incorporate Leibnitz' and Mach's suggestion that time should emerge as surely as space does"..."Yet this separation of time and space runs counter to Einstein's great insight that the two are fundamentally inseparable".
p204. Heisenberg proposed to treat messy collisions as a black box: ....the s matrix. It worked well for a time but by the 1970's quantum field theory proved able to explain the nuclear forces the old-fashioned spatio-temporal way... and the s matrix was forgotten. Meanwhile Roger Penrose came up with the idea of twistors...built of light rays. The intersection of light rays gives you a point...a swirling pattern of light rays reproduces a spinning particle. Local structures in spacetime are encoded non-locally....but the idea didn't work..they didn't cast images in a mirror. However, a leading string theorist, Edward Witten, tried tying string theory and twistors together..and eventually a technique called "amplitudehedron" emerged. ..Basically you draw a polyhedron that captures the structure of a particle interaction....but so far it only works with highly idealised theories of nuclear forces.
A problem I have with all the above e "grab-bag" of theories that I don't know how seriously to take any of them. They all appear to have profound flaws yet Musser doesn't attempt to draw any conclusions..he just describes. I didn't find this very helpful. In fact, found it confusing and it made his book hard to follow.
p214...Musser seems to confound human relations and networks with space time networks. I think he takes the metaphor too far ...and essentially it become meaningless.
He concludes that "if it does turn out that space and time are the products of some deeper level of reality, who knows what new phenomena await our discovery ....dark matter and dark energy? faster than light travel?".
I was hoping for a more prescriptive ending. He runs us through masses of speculation ....seems to give a slight thumbs-up to string theory (though others have suggested it is a theory going nowhere and nothing can be falsified with string theory).
So in the end, a bit disappointing. Three and a half stars from me.… (altro)
Spooky Action at a Distance was an enlightening exploration into the history of non-locality in physics although there are several aspects to it and in many places in the text I was unsure exactly how the phenomenon being explained qualified as non-local. The premise of the book is that space, and likely time as well, are emergent properties of whatever is going on in a level below quantum mechanics and general relativity, but it couldn't in the end come up with more than a quick sketch of what a physics without space or time would look like. Still, I'm glad I read the book to see where the current frontier of physics is at.… (altro)
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