In 1935 Erwin Schrödinger outlined a hypothetical experiment to indicate that something is wrong with the traditional analysis of Quantum Mechanics.
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The [wave-function] of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts. [1]
Schrödinger's cat quickly became the most famous example of what is now referred to as the measurement problem, "the most controversial problem in physics today", [2] with more than 30 youtube video clips devoted to it. (Less widely known is that Einstein suggested a similar bomb experiment to make the very same point, claiming "a sort of blend of not-yet and already-exploded systems [can not be] a real state of affairs". [3])
The measurement problem arises due to the fact that QM does not offer a picture of reality when no one is looking. Rather we have particles that are neither here nor there, states that are in superpositions, and equations that only give probabilities. The majority of physicists believe that these superpositions are real, and several even acknowledge that the cat can be both half dead and half alive. Then there are physicists who opt not to talk about reality.
I am a positivist who believes that physical theories are just mathematical models we construct, and that it is meaningless to ask if they correspond to reality, just whether they predict observations.-- Stephen Hawking. [4]
Something was obviously missing.
That something came along later in the form of Quantum Field Theory-- a theory that does provide a picture of reality, even when no one is looking. However there are various interpretations and understandings of Quantum Field Theory, while some physicists deny it completely. For instance, N. David Mermin wrote in Physics Today, "I hope you will agree that you are not a continuous field of operators on an infinite-dimensional Hilbert space, [5] and Meinard Kuhlmann wrote in Scientific American, "quantum field theory ... sounds like a theory of fields. Yet the fields supposedly described by the theory are not what physicists classically understand by the term field". [6]
Among those who approve Quantum Field Theory, most follow Richard Feynman's method based on particles and virtual particles, while Julian Schwinger's (and Sin-Itiro Tomonaga's) version, which is based only on fields, is much less well-known. [7] Surprisingly enough, Frank Wilczek reports that Feynman later changed his mind:
Feynman told me that when he realized that his theory of photons and electrons is mathematically equivalent to the usual theory, it crushed his deepest hopes ... He gave up when, as he worked out the mathematics of his version of quantum electrodynamics, he found the fields, introduced for convenience, taking on a life of their own. He told me he lost confidence in his program of emptying space. [8]
While both methods lead to the identical equations, the physical pictures are quite different. It is Schwinger's Quantum Field Theory that we refer to in this article, but since this version is so little known, we need to first give a brief description.
Definition of field. A field is a property of space. This idea was proposed by Michael Faraday in 1845 as an explanation for electric and magnetic forces. However the concept that space has properties was not easy to acknowledge, so when James Maxwell predicted the existence of EM waves in 1864, an ether was invented to carry the waves. It took many years before the ether was dispensed with and physicists approved that space itself has properties:
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Showing posts with label Dr. Rodney A. Brooks. Show all posts
Showing posts with label Dr. Rodney A. Brooks. Show all posts
Thursday, February 16, 2017
Wednesday, August 10, 2016
"SPOOKY ACTION AT A DISTANCE" IS IT REALLY SPOOKY?
"Spooky action at a distance", as Einstein called it, refers to the experimental fact that particles can have an effect on each other instantly, even when separated by large distances. For example, if two photons are created collectively in what is called an entangled state and the angular momentum of one is altered, then the angular momentum of the other one will shift in a corresponding fashion at the same time, no matter how far apart the particles are. This "spooky" behavior has been known for almost a hundred years and still is a source of befuddlement.
Still there is a concept in which the end result is not spooky, but rather a natural consequence. I'm referring to Quantum Field Theory, which identifies a world made only of fields, with no particles. What we refer to as a particle is really a chunk, or quantum, of a field. Quanta are not localized like particles, but are spread out across space. For example, photons are parts of the electromagnetic field and protons are pieces of the matter field. These units evolve in a deterministic way as per the basic field equations and there is a term in these equations that limits the speed of propagation to the velocity of light.
However the QFT equations don't tell the whole story. There are events that are not described by the field equations-- for example, when a field quantum transfers energy or momentum to another object. This event is non-local in the sense that the change in, or even disappearance of, the quantum happens immediately, no matter how spread-out the field may be. It can also happen with two knotted quanta-- no matter how much they are separated. In QFT, this is required if each quanta is to act as a unit, as per the fundamental basis of QFT.
There is a major contrast between quantum collapse in QFT and wave-function collapse in QM. The previous is a real physical change in the fields while the following is a change in our knowledge. Although we don't have a theory to describe quantum collapse, there is nothing irregular about it. To quote from Fields of Color: The theory that escaped Einstein:
In QFT the photon is a spread-out field, and the particle-like activity happens because each photon, or quantum of field, is consumed as a unit ... It is a spread-out field quantum, but when it is absorbed by an atom, the entire field vanishes, no matter how spread-out it is, and all its energy is placed into the atom. There is a big "whoosh" and the quantum is gone, like an elephant disappearing from a magician's theater.
Quantum collapse is not an easy concept to accept-- perhaps more difficult than the concept of a field. Here I have been working hard, trying to convince you that fields are a real property of space-- indeed, the only truth-- and now I am seeking you to accept that a quantum of field, spread out as it may be, quickly disappears into a tiny absorbing atom. Yet it is a process that can be visualized without inconsistency. In fact, if a quantum is an entity that lives and dies as a unit, which is the very meaning of quantized fields, then quantum collapse must take place. A quantum can not separate and put half its energy in one place and half in another; that would violate the fundamental quantum principle. While QFT does not provide a reason for when or why collapse occurs, some day we may have a theory that does. In any case, quantum collapse is vital and has been demonstrated experimentally.
Some physicists, including Einstein, have been bothered by the non-locality of quantum collapse, claiming that it violates an essential postulate of Relativity: that nothing can be sent out quicker than the speed of light. Now Einstein's postulate (which we must keep in mind was only a guess) is without a doubt valid in relation to the evolution and propagation of fields as explained by the field equations. However quantum collapse is not described by the field equations, so there is no reason to assume or to insist that it falls in the domain of Einstein's postulate.
Read more here.
Wednesday, April 13, 2016
Recent Physics Theory Resolves Paradoxes
By Rodney Brooks
For one hundred years, most people have seen it impossible to understand physics. Examples include Joseph Heller ("writhing in an exasperating quandary over quantum mechanics"), Bill Clinton ("I hope I can finally understand physics before I leave the earth", Richard Feynman ("One had to lose one's common sense"), and even Albert Einstein ("fifty years of pondering have not brought me any closer to answering the question, what are light quanta?).
Julian Schwinger's Insight to Physics
And yet, there is a concept that makes perfect sense and can be understood by any person. This theory, with origins in the 1930s, was ultimately developed by Julian Schwinger, who once had been considered "the heir-apparent to Einstein's mantle". This success occurred many years after Schwinger had already achieved physics fame for solving the "renormalization" problem, defined by the NY Times as "the most important development in the last 20 years" and was duly awarded the Nobel prize.
However for Schwinger this wasn't good enough. He felt that Quantum Field Theory, as it stood then, was still lacking. His target was to integrate matter fields and force fields on an equivalent basis. Following numerous years of hard work, he presented a collection of five papers entitled "The theory of quantized fields" in 1951-54.
Physicists have been combating a particles-vs.-fields battle for over 100 years. There have been three "rounds", beginning when Einstein's concept of light as a particle (called photon) triumphed over Maxwell's perspective that light is a field. Round 2 happened when Schrödinger's hope for a field theory of matter was overcome by the particle-like behavior that physicists could not ignore. And round 3 happened when Schwinger's field-based solution of renormalization was usurped by Feynman's easier-to-use particle based approach.
For that reason, and others, Schwinger's final advancement of Quantum Field Theory, which he regarded as far more important than his Nobel prize work, has been regretfully ignored, and is undoubtedly not known to most physicists-- and to all of the general public.
Nevertheless there are signs that QFT, in the true Schwingerian sense is reemerging, so in this sense it is a "new" theory There have been a number of books and articles, such as "The Lightness of Being" by Nobel laureate Frank Wilczek, "There are no particles, there are only fields" by Art Hobson, and "Fields of Color- The theory that escaped Einstein" by Rodney Brooks. The last one explains QFT to a lay reader, without any equations, and shows how this remarkable "new" theory" resolves the paradoxes of Relativity, Quantum Mechanics and physics that have confused so many people.
Learn more here!
For one hundred years, most people have seen it impossible to understand physics. Examples include Joseph Heller ("writhing in an exasperating quandary over quantum mechanics"), Bill Clinton ("I hope I can finally understand physics before I leave the earth", Richard Feynman ("One had to lose one's common sense"), and even Albert Einstein ("fifty years of pondering have not brought me any closer to answering the question, what are light quanta?).
Julian Schwinger's Insight to Physics
And yet, there is a concept that makes perfect sense and can be understood by any person. This theory, with origins in the 1930s, was ultimately developed by Julian Schwinger, who once had been considered "the heir-apparent to Einstein's mantle". This success occurred many years after Schwinger had already achieved physics fame for solving the "renormalization" problem, defined by the NY Times as "the most important development in the last 20 years" and was duly awarded the Nobel prize.
However for Schwinger this wasn't good enough. He felt that Quantum Field Theory, as it stood then, was still lacking. His target was to integrate matter fields and force fields on an equivalent basis. Following numerous years of hard work, he presented a collection of five papers entitled "The theory of quantized fields" in 1951-54.
Physicists have been combating a particles-vs.-fields battle for over 100 years. There have been three "rounds", beginning when Einstein's concept of light as a particle (called photon) triumphed over Maxwell's perspective that light is a field. Round 2 happened when Schrödinger's hope for a field theory of matter was overcome by the particle-like behavior that physicists could not ignore. And round 3 happened when Schwinger's field-based solution of renormalization was usurped by Feynman's easier-to-use particle based approach.
For that reason, and others, Schwinger's final advancement of Quantum Field Theory, which he regarded as far more important than his Nobel prize work, has been regretfully ignored, and is undoubtedly not known to most physicists-- and to all of the general public.
Nevertheless there are signs that QFT, in the true Schwingerian sense is reemerging, so in this sense it is a "new" theory There have been a number of books and articles, such as "The Lightness of Being" by Nobel laureate Frank Wilczek, "There are no particles, there are only fields" by Art Hobson, and "Fields of Color- The theory that escaped Einstein" by Rodney Brooks. The last one explains QFT to a lay reader, without any equations, and shows how this remarkable "new" theory" resolves the paradoxes of Relativity, Quantum Mechanics and physics that have confused so many people.
Learn more here!
Friday, November 13, 2015
The Uncertainty Principle
The probabilistic analysis of Schrödinger's equation at some point resulted in the uncertainty principle of Quantum Mechanics, formulated in 1926 by Werner Heisenberg. This principle says that an electron, or any other particle, can not have its precise position known, or even specified. More exactly, Heisenberg formulated a formula that connects the uncertainty in location of a particle to the uncertainty of its momentum. So not only do we have wave-particle duality to deal with, we need to take care of particles that may be here or may be there, but we just can't say where. If the electron is truly a particle, then it only stands to reason that it should be someplace.
Resolution. In Quantum Field Theory there are no particles (stop me if you have indeed heard this before) and thus no location-- certain or uncertain. Alternatively there are blobs of field that are spread over space. As opposed to a particle that is either here or here or perhaps there, we have a field that is here and here and there. Spreading out is a thing that only a field can do; a particle can not do this. Actually Heisenberg's Uncertainty Principle is not very different from Fourier's Theorem (found in 1807) that relates the spatial spread of any wave to the spread of its wave length.
This does not suggest that there is no uncertainty in Quantum Field Theory. There is uncertainty in regard to field collapse, but field collapse is not explained by the formulas of QFT; Quantum Field Theory can just forecast possibilities of when it happens. Nevertheless there is a significant difference between field collapse in QFT and the corresponding wave-function collapse in QM. The former is an actual physical change in the fields; the latter is just a change in our understanding of where the particle is...
For the full article visit the Fields of Color Blog.
Friday, October 30, 2015
Scientific American, EINSTEIN DIDN'T SAY THAT!
In the September "Einstein" issue of Scientific American, audiences are given the impression that gravity is caused by curvature of space-time. For instance, on the 1st page of that segment, we read "gravity ... is the by-product of a curving universe", on p. 43 we discover that "the Einstein tensor G describes how the geometry of space-time is warped and curved by massive objects", and on p. 56 there is a reference to "Albert Einstein's explanation of how gravity emerges from the bending of space and time".
In reality, many physicist today emphasize "curvature" as the definition for gravity. As Stephen Hawking penned in A Brief History of Time, "Einstein made the revolutionary suggestion that gravity is not a force like other forces, but is a consequence of the fact that space-time is not flat, as had been previously assumed: it is curved, or warped.".
The issue is, that's NOT what Einstein said. Einstein made it rather clear that gravity is a force like other forces, along with (obviously) specific distinctions. In the actual paper cited by Scientific American ("The foundation of the general theory of relativity", 1916) he wrote," [there is] a field of force, namely the gravitational field, which possesses the remarkable property of imparting the same acceleration to all bodies". The G tensor, said Einstein "describes the gravitational field." The term "gravitational field" or just "field" occurs 58 times in this article, while the word "curvature" doesn't turn up at all (except in relation to "curvature of a ray of light"). And Einstein is not the only physicist who believes that. For example Sean Carroll, a prominent physicist of today, wrote:.
Einstein's general relativity describes gravity in terms of a field that is defined at every point in space ... The world is really made out of fields ... deep down it's really fields ... The fields themselves aren't "made of" anything-- fields are what the world is made of ... Einstein's ... "metric tensor"... can be thought of as a collection of ten independent numbers at every point.-- Sean Carroll.
To suppress the field concept and emphasize "curvature" not only misstates Einstein's perspective; it likewise offers folks a false or deceptive understanding of basic relativity.
So where does "curvature" originated from? According to Einstein (in the cited paper), the gravitational field causes physical adjustments in the length of measuring rods (just like temperature can cause such changes) and it is these changes that produce a non-Euclidean metric of space. Actually, as Einstein indicated, these changes can take place even in a space which is without gravitational fields-- i.e., a rotating system. He then showed that this non-Euclidean geometry is mathematically equal to the geometry on a curved surface, which had been developed by Gauss and extended (mathematically) to any number of dimensions by Riemann. That this is a mathematical equivalence is clearly stated by Einstein in a later paper: "mathematicians long ago solved the formal problems to which we are led by the general postulate of relativity".
For the full article visit the blog at Fields of Color.
Wednesday, September 30, 2015
When Do Fields Collapse?
A notable question in physics now concerns collapse of the "wave-function": When does it occur? There have been many speculations (see, e.g., Ghirardi-- Rimini-- Weber theory, Penrose Interpretation, Physics forum) and experiments (e.g., "Towards quantum superposition of a mirror") about this. The most extreme viewpoint is the belief that Schrödinger's cat is at the same time alive and dead, although Schrödinger proposed this particular thought-experiment (like Einstein's less-well-known bomb experiment) to demonstrate how silly this type of an idea is.
The concern arises because Quantum Mechanics can only calculate probabilities until an observation happens. But Quantum Field Theory, which deals in real field intensities-- not probabilities, delivers a practical indisputable answer. Unfortunately, Quantum Field Theory in its authentic sense of "there are no particles, there are only fields" (Art Hobson, Am. J. Phys. 81, 2013) is ignored or misinterpreted by a large number of physicists. In QFT the "state" of a system is illustrated by the field intensities (technically, their expectation value) at every point. These fields are real properties of space that behave deterministically depending on the field equations-- with one exception.
The exception is field collapse, but in Quantum Field Theory this is an incredibly different thing from "collapse of the wave function" in QM. It is a physical event, not a change in chances. It occurs when a quantum of field, regardless of how spread-out it may be, suddenly deposits its energy into a single atom and vanishes. (There are also other kinds of collapse, such as scattering, coupled collapse, internal change, and so on) Field collapse is not explained by the field equations-- it is an independent event, but just because we don't possess a theory for it doesn't imply it can not take place. The fact that it is non-local bothers some physicists, but this non-locality has been demonstrated in many experiments, and it does not result in any disparities or paradoxes.
So once field collapse happens, the ultimate "decision"-- the climax-- is reached. This is QFT's answer to when does collapse occur: when a quantum of field colapses. In the case of Schrödinger's cat, this is when the radiated quantum (perhaps an electron) is grabbed by an atom in the Geiger counter.
Right before a field quantum finally collapses, it may have interacted or entangled with numerous other atoms along the way. These interactions are described (deterministically) by the field equations. However the quantum can not have indeed collapsed into any of those atoms, because collapse can transpire only once, so whatever you refer to it as-- interaction, entanglement, perturbation, or just "diddling"-- these initial interactions are undoable and do not bring about macroscopic changes. Then, when the last collapse takes place, those atoms become "undiddled" and return to their undisturbed state.
To sum up, in QFT the "decision" is developed when a quantum of field deposits all its energy into an absorbing atom. In addition to replying to this inquiry, QFT additionally explains why time dilates in Special Relativity and settles the wave-particle duality issue of Quantum Mechanics. One can simply wonder the reason that this particular concept hasn't already been embraced and made the grounds for our awareness of nature. I think it is truly time for physicists to WAKE UP AND SMELL THE QUANTUM FIELDS.
Get more info on the Fields of Color Blog!
Thursday, September 10, 2015
Book Clarifies Confusing Quantum Field Theory
The following is a current article written about Quantum Field Theory and the book, Fields of Color. The write-up appeared in the Leisure World News on September 4, 2015.
The publication "Fields of Color: The Theory that Escaped Einstein" clarifies the perplexing Quantum Field Theory in order that a layman can understand it. Written by Leisure World resident Rodney Brooks, it features no equations-- in fact, no math-- and it makes use of colors to represent fields, which in themselves are difficult to picture. It demonstrates the field picture of nature resolves the paradoxes of quantum mechanics and relativity that have puzzled so many people. It is original, comprehensive, and entertaining.
Brooks is blown away and pleased with the success of his book, which was released in 2011. He says 6,000 copies have been sold, rare for a self-published book on physics. On top of that, the publication has a 4.4 (out of 5) star rating on Amazon along with greater than 90 reader reviews-- a higher score than Einstein's own book on relativity and above Stephen Hawking's popular book "The Theory of Everything.".
In its essence, quantum field theory (QFT) illustrates a world comprised of fields, not particles (neutrons, electrons, protons) as most physicists believe. Nevertheless the field principle is difficult to grasp. To quote from Chapter 1 of "Fields of Color": "To put it briefly, a field is a property or a condition of space. The field concept was introduced into physics in 1845 by Michael Faraday as an explanation for electric and magnetic forces. However, the idea that fields can exist by themselves as "properties of space" was too much for physicists of the time to accept." (Chapter 1 in its entirety can be read at http://www.quantum-field-theory.net/).
Colors of Fields.
Later on this principle was expanded to other fields. "In Quantum Field Theory the entire fabric of the cosmos is made of fields, and I use (arbitrary) colors to help people visualize them," says Brooks. "If you can picture the sky as blue, you can picture the fields that exist in space. Besides the EM (electromagnetic) field ('green'), there are the strong force field ('purple') that holds protons and neutrons together in the atomic nucleus and the weak force field ('brown') that is responsible for radioactive decay. Gravity is also a field ('blue'), and not 'curvature of space-time' which most people, including me, have trouble visualizing.".
He carries on: "In QFT, space is the same old three-dimensional space that we intuitively believe in, and time is the time that we intuitively believe in. Even matter is made of fields-- in fact two fields. I use yellow for light particles like the electron and red for heavy particles,.
like the proton. But make no mistake, in QFT these 'particles' are not little balls; they are spread-out chunks of field, called quanta. Thus the usual picture of the atom with electrons traveling around the nucleus like little balls, is replaced by a 'yellowness' of the space around the nucleus that represents the electron field.".
Brooks' interest in physics was first kindled when at age 14 he read Arthur Eddington's "The Nature of the Physical World." This publication describes how a table is made of little atoms that consequently can be divided into even tinier objects. "So this is what the world is built of," Brooks thought back then. In college at the University of Florida he majored in math with a minor in physics. He was then drafted into the army for two years.
Quantum Field Theory Answers Problem.
Fast forward to graduate school at Harvard University where Brooks was a National Science Foundation scholar, majoring in physics. During the course of this time, he enrolled in a three-year formal lecture series instructed by Julian Schwinger. The Nobel prize-winning physicist had just completed his reformulation of QFT, so the timing was perfect. "I was surprised that all the paradoxes of relativity and quantum mechanics that had previously perplexed me evaporated or were resolved," Brooks says.
After acquiring his Ph.D. at Harvard under Nobel laureate Norman Ramsey, Brooks worked for 25 years at the National Institutes of Health in Bethesda, Md., in neuroimaging. His first research study was regarding the brand new procedure of Computered Tomography (CT), during which time he devised the approach now known as dual-energy CT. Later, he did research on Positron Emission Tomography (PET) and ultimately in Magnetic Resonance Imaging (MRI). All in all, Brooks published 124 peer-reviewed articles.
Once he retired, he and his wife, Karen Brooks, relocated to New Zealand in 2001. That was when he became aware of the prevalent confusion about physics, specifically quantum mechanics and relativity, whilst his cherished QFT that fixes the confusion was disregarded, misunderstood, or neglected.
"Consequently I undertook the mission of illustrating the concepts of quantum field theory to the public," Brooks says.
His book was initially published in New Zealand in 2010, and is presently in its second edition.
In 2012, his grandchildren, who reside in Maryland called out, and he and his wife relocated to Leisure World, where he moves ahead to work on his purpose. Whilst Einstein ultimately came to think that reality must contain fields and fields alone, he preferred there to be a solitary "unified" field that would not merely consist of gravity and electromagnetic forces (the only two forces recognized back then), but would additionally contain matter.
He invested the last 25 years of his life unsuccessfully looking for this unified field theory.
Referring to the particle picture that he espoused, physicist Richard Feynman once said, "The theory ... describes Nature as absurd from the point of view of common sense. And it agrees fully with experiment. So I hope you can accept Nature as She is-- absurd.".
Brooks, alternatively, concludes his initial chapter by saying, "I hope you can accept Nature as She is: beautiful, consistent and in accord with common sense-- and made of quantized fields.".
Find out more on the Fields of Color Blog.
Friday, August 21, 2015
Space-Time Curvature & Quantum Field Theory
General Relativity is the name provided for Einstein's theory of gravity that was defined in Chapter 2 of my book. As the idea is usually shown, it explains gravity as a curvature in four-dimensional space-time. Now it is a concept far over and above the reach of common people. Just the concept of four-dimensional space-time causes the majority of us to shudder ... The answer in Quantum Field Theory is easy: Space is space and time is time, and there is no curvature. In QFT gravity is a quantum field in ordinary three-dimensional space, just like the other 3 force fields (EM, strong and weak).
This does not actually suggest that four-dimensional notation is not useful. It is a convenient way of handling the mathematical connection between space and time which is needed by special relativity. One could almost say that physicists couldn't live without having it. Still, spatial and temporal evolution are fundamentally different, and I say shame on people who aim to foist and push the four-dimensional concept onto the general public as vital to the understanding of theory of relativity.
The idea of space-time curvature likewise had its origin in mathematics. When seeking a mathematical approach that could embody his Principle of Equivalence, Einstein was led to the formulas of Riemannian geometry. And indeed, these formulas define four-dimensional curvature, for individuals who are able to imagine it. You see, mathematicians are not confined by physical constraints; equations that have a physical definition in 3 dimensions can possibly be generalized algebraically to any variety of dimensions. But when you do this, you are truly handling algebra (equations), not geometry (spatial configurations).
By expanding our minds, several of us are able to even make a faint mental image of what four-dimensional curvature might be like if it did exist. Nevertheless, claiming that the gravitational field equations are equal to curvature is definitely not the same as stating that there is curvature. In Quantum Field Theory, the gravitational field is just another force field, like the EM, strong and weak fields, though with a higher complication which is demonstrated in its higher spin value of 2.
While QFT resolves these paradoxical declarations, I really don't wish to leave you having the thought that the theory of quantum gravity is problem-free. While computational issues concerning the EM field were overcome with process referred to as renormalization, comparable challenges involving the quantum gravitational field have not been conquered. Fortunately they do not interfere with macroscopic computations, for which the QFT formulas become the same to Einstein's.
Your choice. Once again you the reader have an option, as you did in concern to the two methods to special relativity. The option is not about the formulas, it has to do with their perception. Einstein's equations can be deciphered as suggesting a curvature of space-time, unpicturable as it may be, or as detailing a quantum field in three-dimensional space, just like the other quantum force fields. To the physicist, it actually doesn't make much difference. Physicists are far more concerned with solving their formulas rather than with analyzing them. If you will permit me another Weinberg quote:
The important thing is to be able to make predictions about images on the astronomers photographic plates, frequencies of spectral lines, and so on, and it simply doesn't matter whether we ascribe these predictions to the physical effects of gravitational fields on the motion of planets and photons or to a curvature of space and time. (The reader should be warned that these views are heterodox and would meet with objections from many general relativists.)-- Steven Weinberg
Therefore in case you prefer, you can believe that gravitational effects are due to a curvature of space-time (despite the fact that you can't visualize it). Or, like Weinberg (and me), you can view gravity as a force field that, similar to the other force fields in Quantum Field Theory, exists in three-dimensional space and progresses in time according to the field equations.
Click for more Fields of Color
Monday, July 20, 2015
Why is the Speed of Light Constant?
The query "The reason is the speed of light constant?" is typically asked about by individuals attempting to learn physics. Google has 2760 links to that question. However the answer is so easy that a 10-year-old can understand it, that is, if you accept Quantum Field Theory.
Bring the ten-year-old to a lake and drop a rock in the water. Show her that the waves move through the water at a specific velocity, and tell her that this velocity depends solely on the properties of water. You may drop different items at different areas and show her that the waves go at the exact same rate, no matter the size of the object or location of the water.
Then tell her that sound travels through air with a fixed velocity that depends solely on the properties of air. You might wait for a thunderstorm and time the difference in between the lightning and the noise. Inform her that a whisper moves as fast as a scream. I believe a ten-year-old can perceive the concept that water and air have properties that establish the velocity of these waves, even if she does not understand the equations.
Any person who can understand this can then comprehend why the speed of light is constant. You see, in Quantum Field Theory space has properties, exactly as air and water have properties. These properties are known as fields.
As Nobel laureate Frank Wilczek wrote, "One of the most basic results of special relativity, that the speed of light is a limiting velocity for the propagation of any physical influence, makes the field concept almost inevitable.".
When you recognize the concept of fields (which of course is certainly not an easy one), that is really all you have to understand. Light is waves in the electromagnetic field that travel through space (not space-time) at a velocity governed by the properties of space. They abide by fairly basic formulas (not that you have to recognize them), just like sound and water waves follow basic formulas. OK, the Quantum Field Theory equations are a little bit more intricate, but quoting Wilczek again, "The move from a particle description to a field description will be especially fruitful if the fields obey simple equations ... Evidently, Nature has taken the opportunity to keep things relatively simple by using fields.".
Even so this inquiry can have a different meaning: "Why is the speed of light independent of motion?" This fact was first illustrated by the renowned Michelson-Morley experiment, in which light beams were measured as the earth revolved and rotated. The shocking result was actually that the speed of light was precisely the same no matter the earth's movement.
As I wrote in my publication (see quantum-field-theory. net): That the speed of light must be independent of movement was most surprising ... It makes no sense for a light beam - or anything, for that concern - to travel at the exact same speed regardless of the movement of the observer ... except if "something funny" is going on. The "something funny" ended up being much more astonishing than the M-M result itself. Essentially, objects contract when they move! More specifically, they contract in the direction of movement. Think about it. If the path length of Michelson's device in the forward direction contracted by the exact same amount as the extra distance the light beam would certainly have to travel due to motion, the two effects would cancel out. Indeed, this is the only way that Michelson's null result can be illustrated.
However the idea that objects contract when in motion was just as confusing as the Michelson-Morley outcome. Why should this be? Again the explanation is offered by Quantum Field Theory. Quoting once again from my publication:.
We need to recognize that even though the molecular configuration of an object appears to be stationary, the component fields are constantly interacting with one another. The EM field interacts with the matter fields and vice versa, the strong field interacts with the nucleon fields, etc. These interactions are what holds the object together. Now if the object is moving rather fast, this interaction between fields will certainly become more difficult because the fields, on the average, will need to interact through larger distances. Thus the object in motion ought to somehow adjust itself so that the identical interaction between fields can take place. How can it do this? The only way is by decreasing the distance the component fields need to travel. Since the spacing between atoms and molecules, and hence the dimensions of an item, are determined by the nature and arrangement of the force fields that bind them together, the dimensions of an object must therefore be affected by movement.
It is essential to recognize that it is not just Michelson's apparatus that contracted, it is anything and everything in the world, including Michelson himself. Even if the earth's speed and the consequent contraction were a lot greater, we on earth would continue to be ignorant of it. As John Bell discussed a moving observer:.
But will she not see that her meter sticks are contracted when laid out in the [direction of motion] - and even decontract when turned in the [other] direction? No, because the retina of her eye will also be contracted, so that just the same cells receive the image of the meter stick as if both stick and observer were at rest. - J. Bell (B2001, p. 68).
To conclude, for those who wish to comprehend physics, I say use Quantum Field Theory and: WAKE UP AND SMELL THE FIELDS.
Thursday, July 2, 2015
EXACTLY WHAT DOES THE ELECTRON LOOK LIKE?
In June, 2014, I lectured at the Physics Department of the Czech Technical University in Prague. I began by asking the question "What does the electron look like?", and I presented 2 images. The first was the familiar Rutherford photo of particles orbiting a nucleus, and the 2nd was a (very simplified) photo of the electron as a field in the area surrounding the nucleus.
Then I wanted a vote. Rather remarkably only four people in the crowd chose the field photo, and not a single person picked the particle photo. In other words, THEY DID N'T KNOW. So here we are, 117 years after the electron was identified, and this highly educated group of physicists had no idea what it looks like.
Naturally when the electron was discovered by J. J. Thomson, it was naturally pictured as a particle. After all, particles are simple to imagine, while the field idea, let alone a quantized field, is not a very easy one to understand. But this photo soon ran into problems that led Niels Bohr in 1913 to offer that the particles in orbit image must be replaced by something new: undefined electron conditions that satisfy the following two postulates:
1. [They] have a peculiarly, mechanically unexplainable [emphasis added] stability.
2. In contradiction to the classical EM theory, no radiation takes place from the atom in the stationary states on their own, [however] a process of transition among two stationary states can be followed by the emission of EM radiation.
This led Louis de Broglie to suggest that the electron has wave properties. There then followed a sort of conflict, with Paul Dirac leading the "particle side" and Erwin Schrodinger the "wave side":.
We insist that the atom in truth is just the ... phenomenon of an electron wave captured, as it were, by the nucleus of the atom ... From the point of view of wave mechanics, the [particle image] would be just fictitious.-- E. Schrodinger.
Nevertheless the fact that a free electron acts like a particle could not be overcome, and so Schrodinger gave in and Quantum Mechanics became a theory of particles that are defined by probabilities.
A 2nd battle happened in 1948, when Richard Feynman and Julian Schwinger (along with Hideki Tomanaga) created various methods to the "renormalization" problem that plagued physics. Again the particle view espoused by Feynman triumphed, in huge part considering that his particle diagrams demonstrated simpler to deal with than Schwinger's field equations. So 2 generations of physicists have been brought up on Feynman designs and led to believe that nature is made from particles.
In the meantime, the theory of quantized fields was refined by Julian Schwinger:.
My retreat started at Brookhaven National Laboratory in the summer of 1949 ... Like the silicon chip of more recent years, the Feynman diagram was delivering computing to the masses ... But inevitably one has to bring it all together again, and then the piecemeal method loses a bit of its appeal ... Quantum field theory must work with [force] fields and [matter] fields on a completely equal ground ... Here was my challenge.-- J. Schwinger.
Schwinger's last variation of the theory was released between 1951 and 1954 in a collection of five documents entitled "The Theory of Quantized Fields". In his terms:.
It was to be the purpose of further developments of quantum mechanics that these 2 distinct timeless principles [particles and fields] are combined and become transcended in something that has no classical counterpart-- the quantized field that is a fresh conception of its very own, an unity that replaces the classical duality.-- J. Schwinger.
I believe that the primary reason these work of arts have been ignored is that many physicists considered them too tough to understand. (I know 1 who could not get past the very first page.).
Therefore the choice is all yours. You can believe that the electron is a particle, in spite of the many inconsistencies and absurdities, not to mention questions like how significant the particles are and what are they made of. Or you can believe it is a quantum of the electron field. The choice was described this way by Robert Oerter:.
Wave or particle? The answer: Both, and neither. You could consider the electron or the photon as a particle, but only if you wanted to let particles behave in the bizarre way illustrated by Feynman: appearing again, disrupting each other and canceling out. You can also think of it as a field, or wave, but you had to keep in mind that the detector always registers one electron, or none-- certainly never half an electron, no matter just how much the field has been split up or stretched out. Ultimately, is the field just a calculational instrument to tell you where the particle will be, or are the particles just calculational tools to tell you what the field values are? Take your pick.-- R. Oerter.
What Oerter neglected to mention is that QFT explains why the detector constantly registers one electron or none: the field is quantized. The Q in QFT is extremely important.
So when you choose, dear reader, I really hope you will not pick the image of nature that does not make sense-- that even its proponents call "bizarre". I wish that, like Schwinger, Weinberg, Wilczek, Hobson (and me), you will choose a truth made of quantum fields-- properties of space that are explained by the equations of QFT, the most philosophically appropriate picture of nature that I can think of.
More on the blog at Fields of Color.
Wednesday, April 22, 2015
Looking at the Principle of Relativity the Easier Way
In the entire history of physics there is no equation more famous than e = mc2. This partnership amongst mass (m) and energy (e) was derived in 1905 by Albert Einstein from his Principle of Relativity. The derivation wasn't easy and warranted a paper by itself, referred to as "Does the inertia of a body depend upon its energy content?". The equation continues to baffle and dumbfound lay people, since in the usual particle picture of nature, it is difficult to see exactly why there is an equivalence between mass and energy.
In the meantime, a new theory called Quantum Field Theory was created. QFT was perfected in the 1950s by Julian Schwinger in 5 papers called "Theory of Quantized Fields". In QFT there are no particles, there are only fields-- quantized fields. Schwinger succeeded in placing matter fields (leptons and hadrons) on an equal footing with force fields (gravity, electromagnetic, strong and weak), despite the obvious differences among them. Moreover, Schwinger established the theory from fundamental axioms, as opposed to Richard Feynman's particle picture, which he justified because "it works". Regrettably it was Feynman who won the battle, and today Schwinger's method (and Schwinger himself) are mainly forgotten.
Yet QFT has lots of benefits. It has a stronger basis than the particle picture. It describes lots of things that the particle picture does not, including the numerous paradoxes connected with Relativity Theory and Quantum Mechanics, that have puzzled so many people. Philosophically, lots of people can accept fields as basic properties of space, instead of particles, whose composition is unknow. Or if there visualized as point particles, one can only ask "points of what?" And above all, QFT offers an easy derivation and understanding of e = mc2, as follows.
Mass. In classical physics, mass is a measure of the inertia of a body. In QFT some of the field equations contain a mass term that impacts the rate at which quanta of these fields evolve and propagate, slowing it down. Thus mass takes on the same inertial role in QFT that it does in classical physics. But this is not all it does; this exact same phrase causes the fields to oscillate, and the greater the mass, the higher the frequency of oscillation. The result, if you're imagining these fields as a color in space (as in my book "Fields of Color"), is a kind of glimmer, and the greater the mass, the quicker the glimmer. It might appear unusual that the same term that slows the spatial development of a field also provokes it to oscillate, but it is actually straightforward mathematics to show from the field equations that the frequency of oscillation is given by f = mc2/h, where h is Planck's constant.
Energy. In classical physics, energy means the capability to perform work, which is specified as applying a force over a distance. This definition, however, does not offer much of an image, so in classical physics, energy is a rather abstract idea. In QFT, on the other hand, the energy of a quantum is established by the oscillations in the field that comprises the quantum. In fact, Planck's famous relationship e = hf, where h is Planck's constant and f is frequency, found in the centennial year of 1900, follows directly from the equations of QFT.
Well, since both mass and energy are associated with oscillations in the field, it does not take an Einstein to see that there must be a connection between the two. In fact, any schoolboy can combine the two equations and find (big drum roll, please) e = mc2. Not only does the formula tumble right out of QFT, its significance can be imagined in the oscillation or "shimmer" of the fields. Nobel laureate Frank Wilczek calls these oscillations "a marvelous bit of poetry" that produce a "Music of the Grid" (Wilczek's phrase for space viewed as a lattice of points):.
"Instead of plucking a string, blowing through a reed, banging on a drumhead, or clanging a gong, we play the instrument that is empty space by plunking down different combos of quarks, gluons, electrons, photons, ... and let them settle till they get to balance with the spontaneous activity of Grid ... These resonances represent particles of different mass m. The masses of particles sound the Music of the Grid.".
This QFT derivation of e = mc2 is not typically known. In fact, I have never seen it in the books I've read. And still I consider it just one of the great accomplishments of QFT.
Find more information about the Principle of Relativity on the Fields of Color Blog!!
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