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Unification of Fundamentals Physics: The First 1988 Dirac Memorial Lecture
This is an expanded version of the third Dirac Memorial Lecture, given in 1988 by the Nobel Laureate Abdus Salam. Salam's lecture presents an overview of the developments in modern particle physics from its inception at the turn of the century to the present theories seeking to unify all the fundamental forces. In addition, two previously unpublished lectures by Paul Dirac, and Werner Heisenberg are included. These lectures provide a fascinating insight into their approach to research and the developments in particle physics at that time. Nonspecialists, undergraduates and researchers will find this a fascinating book. It contains a clear introduction to the major themes of particle physics and cosmology by one of the most distinguished contemporary physicists.
156 pages, Paperback
First published May 25, 1990
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About the author
Abdus Salam
31 books32 followersPakistani theoretical physicist Abdus Salam shared a Nobel Prize of 1979 for helping to develop the theory of the electroweak force, unifying the electromagnetic force and the weak force, two of the four fundamental forces of nature.
This astrophysicist, also the first Muslim to win for his work, belonged to Ahmadiyya community. After Salam gained the highest marks ever recorded for the matriculation examination at the University of the Punjab and then cycled home from Lahore at the age of 14 years in 1940, the whole town turned to welcome him. He won a scholarship to government college, University of the Punjab, and took his Magister Artium in 1946. In the same year, he was awarded a scholarship to Saint John's College, Cambridge, where he took a BA (honours) with a double first in mathematics and physics in 1949. In 1950, he received the Smith's Prize from Cambridge University for the most outstanding pre-doctoral contribution to physics. He also obtained a PhD in theoretical physics at Cambridge; his thesis, published in 1951, contained fundamental work in quantum electrodynamics which had already gained him an international reputation.
Salam returned to Pakistan in 1951 to teach mathematics at Government College, Lahore, and in 1952 became head of the mathematics department of the Punjab University. To pursue a career of research in theoretical physics, he with no alternative at that time left his own country and worked abroad. Many years later, he succeeded in finding a way to solve the heartbreaking dilemma that many young and gifted theoretical physicists from developing countries faced.
At the ICTP, Trieste, which he created, he instituted the famous "associateships" which allowed deserving young physicists to spend their vacations in an invigorating atmosphere in close touch with their peers in research and with the leaders in their own field.
In 1954, Salam left his country for a lectureship at Cambridge, and since then has visited Pakistan as adviser on science policy. His work for Pakistan has, however, been far-reaching and influential. He was a founding member of the Pakistan Atomic Energy Commission, a member of the Scientific Commission of Pakistan and was Chief Scientific Adviser to the President from 1961 to 1974. Salam was also responsible for initiating research on water logging and salinity problems in Pakistan. He also played a critical role in agricultural research, PAEC and SUPARCO, the international space agency in Pakistan.
Since 1957 till his death, he was Professor of Theoretical Physics at Imperial College, London, and since 1964 combined this position with that of Director of the ICTP, Trieste.
For more than forty years he had been a prolific researcher in theoretical elementary particle physics. He had either pioneered or been associated with all the important developments in this field, maintaining a constant and fertile flow of brilliant ideas. For the past thirty years he used his academic reputation to add weight to his active and influential participation in international scientific affairs. He served on a number of United Nations committees concerned with the advancement of science and technology in developing countries.
Abdus Salam is known to be a devout Muslim, whose religion, inseparable from his work and family life, occupied not a separate compartment of his life. He once wrote: "The Holy Quran enjoins us to reflect on the verities of Allah's created laws of nature; however, that our generation has been privileged to glimpse a part of His design is a bounty and a grace for which I render thanks with a humble heart."
After a long illness, Abdus Salam died in Oxford, England. People finally brought his body back to Pakistan, where thirteen thousand men and women visited to pay their last respects. Thirty thousand persons attended his funeral prayers.
Reference: biography by Miriam Lewis, now a
This astrophysicist, also the first Muslim to win for his work, belonged to Ahmadiyya community. After Salam gained the highest marks ever recorded for the matriculation examination at the University of the Punjab and then cycled home from Lahore at the age of 14 years in 1940, the whole town turned to welcome him. He won a scholarship to government college, University of the Punjab, and took his Magister Artium in 1946. In the same year, he was awarded a scholarship to Saint John's College, Cambridge, where he took a BA (honours) with a double first in mathematics and physics in 1949. In 1950, he received the Smith's Prize from Cambridge University for the most outstanding pre-doctoral contribution to physics. He also obtained a PhD in theoretical physics at Cambridge; his thesis, published in 1951, contained fundamental work in quantum electrodynamics which had already gained him an international reputation.
Salam returned to Pakistan in 1951 to teach mathematics at Government College, Lahore, and in 1952 became head of the mathematics department of the Punjab University. To pursue a career of research in theoretical physics, he with no alternative at that time left his own country and worked abroad. Many years later, he succeeded in finding a way to solve the heartbreaking dilemma that many young and gifted theoretical physicists from developing countries faced.
At the ICTP, Trieste, which he created, he instituted the famous "associateships" which allowed deserving young physicists to spend their vacations in an invigorating atmosphere in close touch with their peers in research and with the leaders in their own field.
In 1954, Salam left his country for a lectureship at Cambridge, and since then has visited Pakistan as adviser on science policy. His work for Pakistan has, however, been far-reaching and influential. He was a founding member of the Pakistan Atomic Energy Commission, a member of the Scientific Commission of Pakistan and was Chief Scientific Adviser to the President from 1961 to 1974. Salam was also responsible for initiating research on water logging and salinity problems in Pakistan. He also played a critical role in agricultural research, PAEC and SUPARCO, the international space agency in Pakistan.
Since 1957 till his death, he was Professor of Theoretical Physics at Imperial College, London, and since 1964 combined this position with that of Director of the ICTP, Trieste.
For more than forty years he had been a prolific researcher in theoretical elementary particle physics. He had either pioneered or been associated with all the important developments in this field, maintaining a constant and fertile flow of brilliant ideas. For the past thirty years he used his academic reputation to add weight to his active and influential participation in international scientific affairs. He served on a number of United Nations committees concerned with the advancement of science and technology in developing countries.
Abdus Salam is known to be a devout Muslim, whose religion, inseparable from his work and family life, occupied not a separate compartment of his life. He once wrote: "The Holy Quran enjoins us to reflect on the verities of Allah's created laws of nature; however, that our generation has been privileged to glimpse a part of His design is a bounty and a grace for which I render thanks with a humble heart."
After a long illness, Abdus Salam died in Oxford, England. People finally brought his body back to Pakistan, where thirteen thousand men and women visited to pay their last respects. Thirty thousand persons attended his funeral prayers.
Reference: biography by Miriam Lewis, now a
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April 9, 2018
This book consists of three lectures by eminent (Nobel prize winning) physicists as well as an introductory Foreword by John C. Taylor (University of Cambridge).
The first lecture (1988) is by Mr. Salam - deals with the attempts through the ages of philosophers, mathematicians, and physicists to unify fundamental forces, that is, to come up with a plausible theory explaining gravity, time, space and so forth. Next, Mr. Salam provides an introduction to the two 1968 lectures by Werner Heisenberg and Paul Adrian Maurice Dirac - which are the other two lectures in the volume. Mr. Heisenberg's lecture is entitled "Theory, Criticism, and a philosophy" and the title of Mr. Dirac's talk is "Methods in theoretical physics."
Since I'm only a layperson - certainly not a nerd or anything like that - I have no way of knowing what additional particles have been discovered since the publication of this book about 30 years ago, or subsequent theoretical advances. Still, as of the late 80s, the book reflects the extent of knowledge or theoretical explanations about fundamental forces, the composition of matter and so forth - so it's still interesting to read. Thankfully, it contains only a minimal amount of jargon or formulas or calculations and so can be enjoyed or at least read by almost anyone with an interest in the subject.
Cosmology, and the nature of matter, and what time is, have been subjects of speculation since time immemorial. Obviously, the explanations originally were religious - but eventually some challenged the religious explanation of creation and also proposed theories as to the atomic composition of matter. The theories were eventually verified as more and more accurate means of observation confirmed the atomic theories. This is the simplest way of describing the advancement of knowledge in the approximately 2,500 years since Democritus (and probably philosophers in other areas of the world) first suggested that matter might consist of atoms. The contributions to the theory since then were made by many thinkers across cultures, and we can say that the progress of knowledge continues to this day, as particle accelerators continue to reveal more information about mysteries concerning atomic composition, what holds particles together, and how the universe (or at least our universe) began.
If someone like me could get something out of this book, then anyone can. It's not a popularization of a complex subject, but it's accessible to the average reader nonetheless.
Quotes:
From Mr. Abdus' (1988 Dirac Memorial Lecture):
"...Al-Biruni ... flourished in Afghanistan a thousand years ago. ... Al-Biruni ... to my knowledge, was the first physicist to say explicitly that physical phenomena on the Sun, earth and the Moon obey the same laws."
"...six hundred years later... Galileo used his telescope ... to observe the shadows cast by mountains on the moon. ...he was able to assert that the laws of shadow making were the same on the Moon as on the Earth. This was the first demonstration of the fundamental principle -- now known as the Galilean Symmetry -- which asserted the universality of physical laws."
"Around 1680 [Isaac Newton] ... asserted that the force of "terrestrial" gravity (which makes apples fall to the ground...) was the same as "celestial" gravity (the force which keeps planets in motion around the Sun)."
"The next unification of fundamental forces was postulated some 150 years later. ...Faraday and Ampere [1820s to 1830s] in the context of electromagnetism -- the 'force of life' (so called because all chemical binding is electromagnetic in origin, and so are all phenomena of nerve impulses)."
"Faraday and Ampere, in the greatest unification modern times, were the first to show that electricity and magnetism were but two aspects of one single force - electromagnetism."
"Classical electromagnetism found its culmination fifty years later in the work of Maxwell, who showed that if an electric charge is accelerated (i.e. its speed changes or there is a change of direction), it would emit energy in the form of electromagnetic radiation (radio waves, heat waves, light rays, X-rays, gamma rays which differ from each other in respect of their wavelengths only)."
"[Maxwell] ... was unfortunate in that he died at the early age of 48 and did not live to see electromagnetic radiation produced by accelerating electric charges - demonstrated by Hertz in Germany some ten years after Maxwell's death."
"[Einstein's] ... Special Theory of Relativity (1905) places space and time on an equal footing. One consequence of this work was the time dilatation formula which says that the faster a body moves, the longer its life is - as observed by a stationary observer."
"Einstein went further in this general theory of relativity (1915). He geometrised physics in the sense that in his theory, the curvature of space and time determined gravity."
"...Russian astrophysicist Friedmann...found that an expanding universe could arise as a solution of Einstein's equations. This was experimentally confirmed by Hubble, who discovered that distant galaxies are receding from us, precisely in accordance with these ideas. In 1965,Penzias and Wilson accidentally found a radiative background with temperature of 3 degrees kelvin (-270 degrees Centigrade) which apparently filled all of space."
"Rutherford's experiments (done around 1910) showed that atoms are not elementary; rather they consist of a small, dense, central nuclei (some 10 -12 power cm in radius) surrounded by orbiting electrons."
"Later still the 1932 researches of Chadwick and Joliot-Curie revealed that the nucleus itself is made up of yet smaller particles: the protons (p) and the neutrons (n), each 10 -13 power cm in radius."
"If protons and neutrons are at a distance larger than 10 -13 power cm, the strong nuclear force is essentially zero. All that remains at distances larger is the electromagnetic force (between protons) and, of course, the universal force of gravity."
"Later research (by Hofstadter around 1956) has made it plausible that protons and neutrons are themselves not elementary point particles but have a definite size and are therefore composites. Today we believe, as the result of findings at SLAC (Stanford Linear Accelerator Centre), that they are made of of still smaller objects called quarks, which may themselves be elementary and point-like -- an idea introduced into the subject (in 1963) by Gell-Mann and Zweig."
"Corresponding to the six quarks, there are six "lighter" particles -- the so-called leptons, which also divide into three doublets (N e, e), (N m, m) and (N t, t)."
"...a charged particle and its antiparticle can annihilate each other, the surplus energy going into the production of photons (gamma's)."
"Dirac's crucial step was to take the lowest possible energy state the one with all the negative energy states filled with electrons - to be the one in which no particles are observed (the so-called "vacuum" state)."
"...Dirac was able to predict the existence of a new particle, the positron - the antiparticle of the election."
"...one of Dirac's great contributions to the theory of elementary particles: his famous equation which can describe the spins and helicitis of the elementary entities like the electrons, the quarks and their antiparticles and also, of the free proton and the free neutron (and their antiparticles)."
"For our purposes, the forces of central importance (besides gravity and electromagnetism) are the two nuclear forces - the "strong" and the "weak"."
"The weak nuclear force was first discovered by madame Curie as the force responsible for the so-called beta radioactivity. It plays a crucial role in the energy production by the sun."
"One of the most well-known examples of (spontaneously) broken symmetry is the theory of ferromagnetism, which was worked out by Werner Heisenberg in 1928."
"Before the phase transition took place, (that is, when the temperature was higher than 300 proton masses) there was just a single electroweak force. Immediately afterwards it split into two distinct forces, electromagnetism and the weak nuclear..."
"...particles with integer intrinsic spins... are called bosons,and those with half-integer intrinsic spins... are called fermions."
"...the present age of the universe...fifteen billion years."
"One can distinguish three eras of cosmology:
(a) The most recent era, which started around 10 twelfth power seconds (10 fifth power years) after the Hot Bang, with Penzias-Wilson radiation, and continues till today - 10 18th power seconds after the Hot Bang. This is the Large-Scale Matter Era in which galaxies and superclusters have evolved. We know the physics of this era but the astrophysics is still misty.
(b) The second, the so-called Electroweak Era, started with the phase transition corresponding to the spontaneous breaking of the electroweak symmetry at a temperature around 300 proton masses - which according to the calculations of Friedmann, took place around 10 minus twelfth power seconds - and continues up the emission of the Penzias-Wilson radiation.
(c) The third and the earliest era is the Speculative Era, which may have extended from 10 minus 43rd power seconds after the Hot Bang and continued up to 10 minus twelfth power seconds. During this long period, string theories in two dimensions ... may have given rise to four-dimensional space-time as we know it today."
"Physics would change its paradigm once again with the fundamental entities no longer appearing as point particles but as tiny strings."
From Mr. Heisenberg's (1968) lecture:
"[In 1922, Niels Bohr] ... said "we are now in ta new field of physics, in which we know that the old concepts probably don't work. We see that they don't work, because otherwise atoms wouldn't be stable. On the other hand when we want to speak about atoms, we must use words and these words can only be taken from the old concepts, from the old language. Therefore we are in a hopeless dilemma, we are like sailors coming to a very far away country. They don't know the country and they see peole whose language they have never heard, so they don't know how to communicate. Therefore, as far as the classical concepts work, that is, so far as we can speak about the motion of electrons, about their velocity, about their energy, etc., I think that my pictures are correct or at least I hope that they are correct, but nobody knows how far such a language goes."
"[In 1926 Einstein] ...said "whether you can observe a thing or not depends on the theory which you use. It is the theory which decides what can be observed". His argument was like this: "Observation means that we construct some connection between a phenomenon and our realization of the phenomenon. There is something happening in the atom, the light is emitted, the light hits the photographic plate, we see the photographic plate and so on and so on. In this whole course of events between the atom and your eye and your consciousness you must assume that everything works as in the old physics. if you change the theory concerning this sequence of events then of course the observation would be altered". So he insisted that it was the theory which decides about what can be observed. ... A few words more in connection with my discussion with Einstein. Einstein had pointed out to me that it is really dangerous to say that one should only speak about observable quantities. Every reasonable theory will, besides all things which one immediately observe, also give the possibility of observing other things more indirectly. For instance, Mach himself had believed that the concept of the atom was only a point of convenience, a point of economy thinking, he didn't believe in the reality of the atoms. Nowadays everybody would say that this is nonsense, that it is quite clear that the atoms really exist. I also feel that one cannot gain anything by claiming it is only a convenience of our thinking to have the atoms -- though it may be logically possible. These were the points which Einstein raised."
"Then [in 1926] I remembered thEinstein's remark in our discussion. I remembered that Einstein had said that "It is the theory which decides what can be observed". From there it was easy to turn around our question and not to ask "How can I represent in quantum mechanics this orbit of an electron in a cloud chamber?" but rather to ask "Is it not true that always only such situations occur in Nature, even in a cloud chamber, which can be described by the mathematical formalism of quantum mechanics?"
"I think that really the most decisive discovery in connection with the properties or the nature of elementary particles was the discovery of antimatter by Dirac. ... I believe that this discovery of particles and antiparticles by Dirac has changed our whole outlook on atomic physics completely."
"Either you can divide matter again and again into smaller and smaller bits or you cannot divide matter up to infinity and then you come to smallest particles. Now all of a sudden we saw a third possibility: we can divide matter again and again but we never get to smaller particles because we must create particles by energy, by kinetic energy, and since we have pair creation this can go on forever. ... Of course then the problem arose: "What kind of mathematical scheme can describe such a situation?"
From Mr. Dirac's (1968) lecture:
"In any region of physics where very little is known, one must keep to the experimental basis if one is not to indulge in wild speculation that is almost certain to be wrong. I do not wish to condemn speculation altogether. It can be entertaining and may be indirectly useful even if it does turn out to be wrong. One should always keep an open mind receptive to new ideas, so one should not completely oppose speculation but one must take care not to get too involved in it."
"It is usually assumed that the laws of nature have always been the same as they are now. There is no justification for this. The laws may be changing, and in particular quantities which are considered to be constants of nature may be varying with cosmological time. Such variations would completely upset the model makers."
"The ultimate goal is to obtain suitable starting equations from which the whole of atomic physics can be deduced. We are still far from it. One way of proceeding towards it is first to perfect the theory of low-energy physics, which is quantum electrodynamics, and then try to extend it to higher and higher energies. However, the present quantum electrodynamics does not conform to the high standard of mathematical beauty that one would expect for a fundamental physical theory, and leads one to suspect that a drastic alteration of basic ideas is still needed."
The first lecture (1988) is by Mr. Salam - deals with the attempts through the ages of philosophers, mathematicians, and physicists to unify fundamental forces, that is, to come up with a plausible theory explaining gravity, time, space and so forth. Next, Mr. Salam provides an introduction to the two 1968 lectures by Werner Heisenberg and Paul Adrian Maurice Dirac - which are the other two lectures in the volume. Mr. Heisenberg's lecture is entitled "Theory, Criticism, and a philosophy" and the title of Mr. Dirac's talk is "Methods in theoretical physics."
Since I'm only a layperson - certainly not a nerd or anything like that - I have no way of knowing what additional particles have been discovered since the publication of this book about 30 years ago, or subsequent theoretical advances. Still, as of the late 80s, the book reflects the extent of knowledge or theoretical explanations about fundamental forces, the composition of matter and so forth - so it's still interesting to read. Thankfully, it contains only a minimal amount of jargon or formulas or calculations and so can be enjoyed or at least read by almost anyone with an interest in the subject.
Cosmology, and the nature of matter, and what time is, have been subjects of speculation since time immemorial. Obviously, the explanations originally were religious - but eventually some challenged the religious explanation of creation and also proposed theories as to the atomic composition of matter. The theories were eventually verified as more and more accurate means of observation confirmed the atomic theories. This is the simplest way of describing the advancement of knowledge in the approximately 2,500 years since Democritus (and probably philosophers in other areas of the world) first suggested that matter might consist of atoms. The contributions to the theory since then were made by many thinkers across cultures, and we can say that the progress of knowledge continues to this day, as particle accelerators continue to reveal more information about mysteries concerning atomic composition, what holds particles together, and how the universe (or at least our universe) began.
If someone like me could get something out of this book, then anyone can. It's not a popularization of a complex subject, but it's accessible to the average reader nonetheless.
Quotes:
From Mr. Abdus' (1988 Dirac Memorial Lecture):
"...Al-Biruni ... flourished in Afghanistan a thousand years ago. ... Al-Biruni ... to my knowledge, was the first physicist to say explicitly that physical phenomena on the Sun, earth and the Moon obey the same laws."
"...six hundred years later... Galileo used his telescope ... to observe the shadows cast by mountains on the moon. ...he was able to assert that the laws of shadow making were the same on the Moon as on the Earth. This was the first demonstration of the fundamental principle -- now known as the Galilean Symmetry -- which asserted the universality of physical laws."
"Around 1680 [Isaac Newton] ... asserted that the force of "terrestrial" gravity (which makes apples fall to the ground...) was the same as "celestial" gravity (the force which keeps planets in motion around the Sun)."
"The next unification of fundamental forces was postulated some 150 years later. ...Faraday and Ampere [1820s to 1830s] in the context of electromagnetism -- the 'force of life' (so called because all chemical binding is electromagnetic in origin, and so are all phenomena of nerve impulses)."
"Faraday and Ampere, in the greatest unification modern times, were the first to show that electricity and magnetism were but two aspects of one single force - electromagnetism."
"Classical electromagnetism found its culmination fifty years later in the work of Maxwell, who showed that if an electric charge is accelerated (i.e. its speed changes or there is a change of direction), it would emit energy in the form of electromagnetic radiation (radio waves, heat waves, light rays, X-rays, gamma rays which differ from each other in respect of their wavelengths only)."
"[Maxwell] ... was unfortunate in that he died at the early age of 48 and did not live to see electromagnetic radiation produced by accelerating electric charges - demonstrated by Hertz in Germany some ten years after Maxwell's death."
"[Einstein's] ... Special Theory of Relativity (1905) places space and time on an equal footing. One consequence of this work was the time dilatation formula which says that the faster a body moves, the longer its life is - as observed by a stationary observer."
"Einstein went further in this general theory of relativity (1915). He geometrised physics in the sense that in his theory, the curvature of space and time determined gravity."
"...Russian astrophysicist Friedmann...found that an expanding universe could arise as a solution of Einstein's equations. This was experimentally confirmed by Hubble, who discovered that distant galaxies are receding from us, precisely in accordance with these ideas. In 1965,Penzias and Wilson accidentally found a radiative background with temperature of 3 degrees kelvin (-270 degrees Centigrade) which apparently filled all of space."
"Rutherford's experiments (done around 1910) showed that atoms are not elementary; rather they consist of a small, dense, central nuclei (some 10 -12 power cm in radius) surrounded by orbiting electrons."
"Later still the 1932 researches of Chadwick and Joliot-Curie revealed that the nucleus itself is made up of yet smaller particles: the protons (p) and the neutrons (n), each 10 -13 power cm in radius."
"If protons and neutrons are at a distance larger than 10 -13 power cm, the strong nuclear force is essentially zero. All that remains at distances larger is the electromagnetic force (between protons) and, of course, the universal force of gravity."
"Later research (by Hofstadter around 1956) has made it plausible that protons and neutrons are themselves not elementary point particles but have a definite size and are therefore composites. Today we believe, as the result of findings at SLAC (Stanford Linear Accelerator Centre), that they are made of of still smaller objects called quarks, which may themselves be elementary and point-like -- an idea introduced into the subject (in 1963) by Gell-Mann and Zweig."
"Corresponding to the six quarks, there are six "lighter" particles -- the so-called leptons, which also divide into three doublets (N e, e), (N m, m) and (N t, t)."
"...a charged particle and its antiparticle can annihilate each other, the surplus energy going into the production of photons (gamma's)."
"Dirac's crucial step was to take the lowest possible energy state the one with all the negative energy states filled with electrons - to be the one in which no particles are observed (the so-called "vacuum" state)."
"...Dirac was able to predict the existence of a new particle, the positron - the antiparticle of the election."
"...one of Dirac's great contributions to the theory of elementary particles: his famous equation which can describe the spins and helicitis of the elementary entities like the electrons, the quarks and their antiparticles and also, of the free proton and the free neutron (and their antiparticles)."
"For our purposes, the forces of central importance (besides gravity and electromagnetism) are the two nuclear forces - the "strong" and the "weak"."
"The weak nuclear force was first discovered by madame Curie as the force responsible for the so-called beta radioactivity. It plays a crucial role in the energy production by the sun."
"One of the most well-known examples of (spontaneously) broken symmetry is the theory of ferromagnetism, which was worked out by Werner Heisenberg in 1928."
"Before the phase transition took place, (that is, when the temperature was higher than 300 proton masses) there was just a single electroweak force. Immediately afterwards it split into two distinct forces, electromagnetism and the weak nuclear..."
"...particles with integer intrinsic spins... are called bosons,and those with half-integer intrinsic spins... are called fermions."
"...the present age of the universe...fifteen billion years."
"One can distinguish three eras of cosmology:
(a) The most recent era, which started around 10 twelfth power seconds (10 fifth power years) after the Hot Bang, with Penzias-Wilson radiation, and continues till today - 10 18th power seconds after the Hot Bang. This is the Large-Scale Matter Era in which galaxies and superclusters have evolved. We know the physics of this era but the astrophysics is still misty.
(b) The second, the so-called Electroweak Era, started with the phase transition corresponding to the spontaneous breaking of the electroweak symmetry at a temperature around 300 proton masses - which according to the calculations of Friedmann, took place around 10 minus twelfth power seconds - and continues up the emission of the Penzias-Wilson radiation.
(c) The third and the earliest era is the Speculative Era, which may have extended from 10 minus 43rd power seconds after the Hot Bang and continued up to 10 minus twelfth power seconds. During this long period, string theories in two dimensions ... may have given rise to four-dimensional space-time as we know it today."
"Physics would change its paradigm once again with the fundamental entities no longer appearing as point particles but as tiny strings."
From Mr. Heisenberg's (1968) lecture:
"[In 1922, Niels Bohr] ... said "we are now in ta new field of physics, in which we know that the old concepts probably don't work. We see that they don't work, because otherwise atoms wouldn't be stable. On the other hand when we want to speak about atoms, we must use words and these words can only be taken from the old concepts, from the old language. Therefore we are in a hopeless dilemma, we are like sailors coming to a very far away country. They don't know the country and they see peole whose language they have never heard, so they don't know how to communicate. Therefore, as far as the classical concepts work, that is, so far as we can speak about the motion of electrons, about their velocity, about their energy, etc., I think that my pictures are correct or at least I hope that they are correct, but nobody knows how far such a language goes."
"[In 1926 Einstein] ...said "whether you can observe a thing or not depends on the theory which you use. It is the theory which decides what can be observed". His argument was like this: "Observation means that we construct some connection between a phenomenon and our realization of the phenomenon. There is something happening in the atom, the light is emitted, the light hits the photographic plate, we see the photographic plate and so on and so on. In this whole course of events between the atom and your eye and your consciousness you must assume that everything works as in the old physics. if you change the theory concerning this sequence of events then of course the observation would be altered". So he insisted that it was the theory which decides about what can be observed. ... A few words more in connection with my discussion with Einstein. Einstein had pointed out to me that it is really dangerous to say that one should only speak about observable quantities. Every reasonable theory will, besides all things which one immediately observe, also give the possibility of observing other things more indirectly. For instance, Mach himself had believed that the concept of the atom was only a point of convenience, a point of economy thinking, he didn't believe in the reality of the atoms. Nowadays everybody would say that this is nonsense, that it is quite clear that the atoms really exist. I also feel that one cannot gain anything by claiming it is only a convenience of our thinking to have the atoms -- though it may be logically possible. These were the points which Einstein raised."
"Then [in 1926] I remembered thEinstein's remark in our discussion. I remembered that Einstein had said that "It is the theory which decides what can be observed". From there it was easy to turn around our question and not to ask "How can I represent in quantum mechanics this orbit of an electron in a cloud chamber?" but rather to ask "Is it not true that always only such situations occur in Nature, even in a cloud chamber, which can be described by the mathematical formalism of quantum mechanics?"
"I think that really the most decisive discovery in connection with the properties or the nature of elementary particles was the discovery of antimatter by Dirac. ... I believe that this discovery of particles and antiparticles by Dirac has changed our whole outlook on atomic physics completely."
"Either you can divide matter again and again into smaller and smaller bits or you cannot divide matter up to infinity and then you come to smallest particles. Now all of a sudden we saw a third possibility: we can divide matter again and again but we never get to smaller particles because we must create particles by energy, by kinetic energy, and since we have pair creation this can go on forever. ... Of course then the problem arose: "What kind of mathematical scheme can describe such a situation?"
From Mr. Dirac's (1968) lecture:
"In any region of physics where very little is known, one must keep to the experimental basis if one is not to indulge in wild speculation that is almost certain to be wrong. I do not wish to condemn speculation altogether. It can be entertaining and may be indirectly useful even if it does turn out to be wrong. One should always keep an open mind receptive to new ideas, so one should not completely oppose speculation but one must take care not to get too involved in it."
"It is usually assumed that the laws of nature have always been the same as they are now. There is no justification for this. The laws may be changing, and in particular quantities which are considered to be constants of nature may be varying with cosmological time. Such variations would completely upset the model makers."
"The ultimate goal is to obtain suitable starting equations from which the whole of atomic physics can be deduced. We are still far from it. One way of proceeding towards it is first to perfect the theory of low-energy physics, which is quantum electrodynamics, and then try to extend it to higher and higher energies. However, the present quantum electrodynamics does not conform to the high standard of mathematical beauty that one would expect for a fundamental physical theory, and leads one to suspect that a drastic alteration of basic ideas is still needed."
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