Evolution of Physics by Einstein

books_evolution

e-book: The Evolution of Physics

I am currently studying this book by Einstein to get an insight into his thinking. This book was originally published in 1938 by Cambridge University Press. It was a popular success, and was featured in a Time magazine cover story.

Here is some information on this book from Wikipedia:

Background of collaboration

Einstein agreed to write the book partly as a way to help Infeld financially. Infeld collaborated briefly in Cambridge with Max Born, before moving to Princeton, where he worked with Einstein at the Institute for Advanced Study. Einstein tried to get Infeld a permanent position there, but failed. Infeld came up with a plan to write a history of physics with Einstein, which was sure to be successful, and split the royalties. When he went to Einstein to pitch the idea, Infeld became incredibly tongue-tied, but he was finally able to stammer out his proposal. “This is not at all a stupid idea,” Einstein said. “Not stupid at all. We shall do it.”

Book’s point of view

In the book, Einstein pushed his realist approach to physics in defiance of much of quantum mechanics. Belief in an “objective reality,” the book argued, had led to great scientific advances throughout the ages, thus proving that it was a useful concept even if not provable. “Without the belief that it is possible to grasp reality with our theoretical constructions, without the belief in the inner harmony of our world, there could be no science,” the book declared. “This belief is and always will remain the fundamental motive for all scientific creation.”

In addition, Einstein used the text to defend the utility of field theories amid the advances of quantum mechanics. The best way to do that was to view particles not as independent objects but as a special manifestation of the field itself: “Could we not reject the concept of matter and build a pure field physics? We could regard matter as the regions in space where the field is extremely strong. A thrown stone is, from this point of view, a changing field in which the states of the greatest field intensity travel through space with the velocity of the stone.”

Contents

The book has four chapters: The Rise of The Mechanical ViewThe Decline of the Mechanical ViewField, Relativity, and Quanta.

The third chapter (Field, Relativity) examines lines of force starting with gravitational fields (i.e., a physical collection of forces), moving on to descriptions of electric and magnetic fields. The authors explain that they are attempting to “translate familiar facts from the language of fluids…into the new language of fields.” They state that the Faraday, Maxwell, and Hertz experiments led to modern physics. They describe how “The change of an electric field produced by the motion of a charge is always accompanied by a magnetic field.”

The two pillars of the field theory (pp.142-148)

The reality of the field (pp.148-156)

Field and ether (pp.156-160)

The mechanical scaffold (pp.160-171)

Ether and motion (pp.172-186)

Time, distance, relativity (pp.186-202)

Relativity and mechanics (pp.202-209)

The time-space continuum (pp.209-220)

General relativity (pp.220-226).

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Comments

  • vinaire  On March 4, 2014 at 8:28 PM

    I am with Einstein in favoring the objectivity and simplicity of the Field Theory. I don’t feel enamored by Quantum Mechanics.

  • vinaire  On March 4, 2014 at 8:33 PM

    I believe that underlying all reality there is a primordial field disturbed by a primordial energy. This DISTURBANCE THEORY can account for electromagnetism as well as for awareness; for matter as well as for self.
    .

  • vinaire  On March 4, 2014 at 9:07 PM

    I like the purpose of this book, “To sketch in broad outline the attempts of the human mind to find a connection between the world of ideas and the world of phenomena… “

  • vinaire  On March 4, 2014 at 9:09 PM

    It is interesting that Einstein recognizes MOTION to be the most fundamental mystery of nature.

  • vinaire  On March 4, 2014 at 9:13 PM

    From Aristotle to Galileo, the most significant progress was moving forward from an intuitive view to a mindful one of examining things in the minutest detail.

  • vinaire  On March 4, 2014 at 9:19 PM

    The Law of inertia is a fascinating fact of nature.

    “Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.”

    This law of inertia cannot be derived directly from experiment, but only by speculative thinking consistent with observation.
    .

  • vinaire  On March 4, 2014 at 9:22 PM

    In general the action of an external force changes not only the speed but also the direction of the motion. An understanding of this fact prepares us for the generalization introduced into physics by the concept of vectors.

  • vinaire  On March 4, 2014 at 11:01 PM

    Force seems to neutralize inertia temporarily.

    When there is no inertia, what is left?

    • vinaire  On March 5, 2014 at 7:10 AM

      It seems that force and inertia are inverse of each other.

      • Chris Thompson  On March 5, 2014 at 8:34 AM

        Not proportional?

      • vinaire  On March 5, 2014 at 8:43 AM

        Force is proportional to the rate of change in velocity, which is known as acceleration. The constant of proportionality is mass.

        Mass represents inertia. When there is no change is velocity, then there is no force. But mass is still there. The velocity becomes uniform. And there is momentum and kinetic energy.

        There seems to be more to the nature of inertia than what is known at present.

        • Chris Thompson  On March 5, 2014 at 6:29 PM

          Right, so then from this, I’m not sure how to visualize force and inertia being inverse. I’m willing to but even if we don’t understand inertia, it is proportional to mass is proportional to force or else, what? Please explain more.

        • vinaire  On March 5, 2014 at 6:50 PM

          When there is no external force acting on the object, its motion is uniform. The motion can be perceived as zero or of any value because it is relative. The inertia is not manifested.

          The inertia manifests itself as resistance only when external force is applied. So, when there is force there is also inertia. When there is no force, there is no inertia.

          Therefore, inertia is like a reaction to the force.

        • Chris Thompson  On March 5, 2014 at 7:52 PM

          Maybe awareness is like inertia. When there is a force vector, there is a commensurate reaction to that vector. When there is a phenomena, there is a reaction of awareness to that phenomena. When there is no relative phenomena, there is no commensurate awareness. When there is too much phenomena, too much awareness ensues in the form of confusion, shutting down, etc.,.

          There seems to be a “sweet-spot” of randomness for each of us — Not too little and not too much.

        • vinaire  On March 5, 2014 at 8:06 PM

          That is an excellent observation. 🙂

        • Chris Thompson  On March 5, 2014 at 8:15 PM

          Thank you, but it is just an idea. I am looking forward to having and spending time with the math, first with the disturbance levels and see how those metrics sound to me when done. Then see if some of these other relations can be described using the poetic rhythms of math.

        • vinaire  On March 5, 2014 at 8:19 PM

          That’s a nice project.

        • Chris Thompson  On March 5, 2014 at 8:23 PM

          I feel I should do something tangible with — learn to speak math — before I attempt to tutor others.

        • vinaire  On March 5, 2014 at 8:27 PM

          Sure!

  • vinaire  On March 5, 2014 at 7:13 AM

    Einstein says. “The initial and fundamental steps are always of a revolutionary character. Scientific imagination finds old concepts too confining, and replaces them by new ones… The continued development along any line already initiated is more in the nature of evolution, until the next turning point is reached when a still newer field must be conquered.”

  • vinaire  On March 5, 2014 at 7:20 AM

    Einstein says, “One of the most important characteristics of modern physics is that the conclusions drawn from initial clues are not only qualitative but also quantitative… To draw quantitative conclusions we must use the language of mathematics… Mathematics as a tool of reasoning is necessary if we wish to draw conclusions which may be compared with experiment.”

  • Chris Thompson  On March 5, 2014 at 8:52 PM

    I continue to wonder about and cannot shake the idea of time-lapse regarding the speed of action-reaction that we call acceleration and as it relates to inertia. We say there is “resistance” but what do we mean by that? What is resisting an instantaneous movement from one state to another. At the microscopic, are these accelerations by quanta or continuous?

  • Chris Thompson  On March 5, 2014 at 8:52 PM

    It seems Einstein loves the metaphor as much as I.

  • Chris Thompson  On March 5, 2014 at 9:20 PM

    Is EMR the unleashed “force” of the universe itself?

  • Chris Thompson  On March 5, 2014 at 9:22 PM

    “Continuous” is an interesting concept.

  • Bud  On March 6, 2014 at 2:08 AM

    I read a supposed quote from Einstein that said there is no such thing as matter, it is just another form of energy. If so no rules associated with matter do not apply. There for nothing is impossible?????

    • vinaire  On March 6, 2014 at 5:27 AM

      In my opinion, what is IS. We simply need to understand it better.

      Sorry, that may come across as somewhat abrupt, but there is no lack of sincerity on my part.

      .

  • vinaire  On March 6, 2014 at 8:30 PM

    Mechanics seems to be an interaction between two very different disturbance levels… Solid objects belong to one disturbance level, and the space between them belongs to another disturbance level. We generally compare solid objects relative to each other against the background of space. Uniform velocity seems to be associated with inertia or the disturbance level. Gravitational force between two objects depends on the space between them.

    • Chris Thompson  On March 6, 2014 at 10:22 PM

      If we visualize space as an elastic medium whose elasticity we term gravity, it gives us another model to stretch or minds.

      Possibly quanta has its beginnings as a precipitate of such a medium.

      Maybe space is a greatly uncoiled singularity.

      Is the space between galaxies of the same substance and mechanic as the space within galaxies?

  • vinaire  On March 7, 2014 at 9:28 AM

    Here is a nice excerpt from the book about gravitational and inertial mass:

    A body at rest gives way before the action of an external force, moving and attaining a certain velocity. It yields more or less easily, according to its inertial mass, resisting the motion more strongly if the mass is large than if it is small. We may say, without pretending to be rigorous: the readiness with which a body responds to the call of an external force depends on its inertial mass. If it were true that the earth attracts all bodies with the same force, that of greatest inertial mass would move more slowly in falling than any other. But this is not the case: all bodies fall in the same way. This means that the force by which the earth attracts different masses must be different. Now the earth attracts a stone with the force of gravity and knows nothing about its inertial mass. The “calling” force of the earth depends on the gravitational mass. The “answering” motion of the stone depends on the inertial mass. Since the ” answering ” motion is always the same all bodies dropped from the same height fall in the same way it must be deduced that gravitational mass and inertial mass are equal.

    .

  • vinaire  On March 8, 2014 at 6:16 AM

    Here is an excerpt from the book about potential and kinetic energy:

    (In a rollercoaster) At its highest point the car has zero velocity and is one hundred feet from the ground. At the lowest possible point it is no distance from the ground, and has its greatest velocity. These facts may be expressed in other terms. At its highest point the car has potential energy but no kinetic energy or energy of motion. At its lowest point it has the greatest kinetic energy and no potential energy whatever. At all intermediate positions, where there is some velocity and some elevation, it has both kinetic and potential energy. The potential energy increases with the elevation, while the kinetic energy becomes greater as the velocity increases. The principles of mechanics suffice to explain the motion. Two expressions for energy occur in the mathematical description, each of which changes, although the sum does not vary. It is thus possible to introduce mathematically and rigorously the concepts of potential energy, depending on position, and kinetic energy, depending on velocity.

    .

  • vinaire  On March 8, 2014 at 6:25 AM

    Furthermore,

    In the real switchback, where friction prevents the car from again reaching as high a point as that from which it started, there is still a continuous change between kinetic and potential energy. Here, however, the sum does not remain constant, but grows smaller… Something more than kinetic and potential energies is now involved, namely, the heat created by friction. Does this heat correspond to the diminution in mechanical energy, that is kinetic and potential energy? A new guess is imminent. If heat may be regarded as a form of energy, perhaps the sum of all three heat, kinetic and potential energies remains constant. Not heat alone, but heat and other forms of energy taken together are, like a substance, indestructible…

    The progress of science has destroyed the older concept of heat as a substance. We try to create a new substance, energy, with heat as one of its forms.

    .

  • vinaire  On March 8, 2014 at 6:29 AM

    There is conservation of mass.
    There is conservation of energy.
    Mass is a form of energy.
    There is conservation of “mass and energy”.
    .

  • vinaire  On March 8, 2014 at 6:58 AM

    From The Evolution of Physics:

    In every event in nature one form of energy is being converted into another, always at some well-defined rate of exchange.

  • vinaire  On March 8, 2014 at 7:01 AM

    From The Evolution of Physics:

    If we regard the whole universe as a closed system, we can proudly announce with the physicists of the nineteenth century that the energy of the universe is invariant, that no part of it can ever be created or destroyed.

    • Chris Thompson  On March 8, 2014 at 9:28 PM

      “If . . . “

    • vinaire  On March 8, 2014 at 9:32 PM

      That’s correct. I have been thinking that awareness is a form of energy too, or it is something that should be included in the conservation postulate along with mass and energy.

  • vinaire  On March 8, 2014 at 7:10 AM

    From The Evolution of Physics:

    Our two concepts of substance are, then, matter and energy. Both obey conservation laws: An isolated system cannot change either in mass or in total energy. Matter has weight but energy is weightless. We have therefore two different concepts and two conservation laws. Are these ideas still to be taken seriously? Or has this apparently well-founded picture been changed in the light of newer developments? It has! Further changes in the two concepts are connected with the theory of relativity. We shall return to this point later.
    .

  • vinaire  On March 8, 2014 at 7:26 AM

    Scientists have been looking at the conservation of physical elements only.

    Is there a broader law pertaining to the conservation of “physical and metaphysical” elements?
    .

  • vinaire  On March 8, 2014 at 7:36 AM

    From The Evolution of Physics:

    The results of scientific research very often force a change in the philosophical view of problems which extend far beyond the restricted domain of science itself. What is the aim of science? What is demanded of a theory which attempts to describe nature? These questions, although exceeding the bounds of physics, are intimately related to it, since science forms the material from which they arise. Philosophical generalizations must be founded on scientific results. Once formed and widely accepted, however, they very often influence the further development of scientific thought by indicating one of the many possible lines of procedure. Successful revolt against the accepted view results in unexpected and completely different developments, becoming a source of new philosophical aspects. These remarks necessarily sound vague and pointless until illustrated by examples quoted from the history of physics.

    .

  • vinaire  On March 8, 2014 at 9:27 AM

    MOTION
    INERTIA
    VELOCITY
    CHANGE IN VELOCITY (magnitude and direction – vector)
    FORCE (proportional to change in velocity)
    ACCELERATION AND MASS
    FORCE AND DISTANCE
    .

  • vinaire  On March 8, 2014 at 9:28 AM

    EXPERIMENTS
    CONSISTENCY OF CONCEPTS
    SIMPLICITY IN THE UNDERSTANDING OF REALITY
    OBJECTIVE TRUTH AS THE IDEAL LIMIT OF A CONCEPT
    CONCEPT OF MASS: INERTIAL AND GRAVITATIONAL
    .

  • vinaire  On March 8, 2014 at 9:29 AM

    MOTION – FRICTION – HEAT
    MECHANICAL ENERGY: POTENTIAL & KINETIC
    MECHANICAL EQUIVALENT OF HEAT AS ENERGY
    CONCEPT OF ENERGY: MECHANICAL, HEAT
    ENERGY IS ANYTHING THAT CAN BE CONVERTED TO MECHANICAL ENERGY AND HEAT
    .

  • vinaire  On March 9, 2014 at 7:07 AM

    > matter demonstrates its existence as a source of force by its action on other matter.
    > The easiest matter to imagine are spherical particles.
    > The easiest forces to imagine are those of attraction and repulsion.
    > The force vectors lie on a line connecting the material points.
    > Simple postulate: the force between any two given particles depends only on the distance between them,
    > But is it possible to describe all physical phenomena by forces of this kind alone?

  • Chris Thompson  On March 9, 2014 at 10:24 AM

    PS: This is a slammin’ good book. No one understands Einstein’s Relativity better than he. The language is very easy to read. Thanks for turning me on to it.

  • Chris Thompson  On March 9, 2014 at 10:34 AM

    Looking at space as having properties and quantities such as weight and mass takes everyday physics in a fresh direction. Referring to space as being elastic and gathering itself is a different look at gravity than “massive objects attract.”

  • vinaire  On March 9, 2014 at 12:57 PM

    > Success of mechanics has contributed to the belief that it is possible to describe all natural phenomena in terms of simple forces between unalterable objects. Is this belief correct?

  • vinaire  On March 9, 2014 at 2:36 PM

    THE MECHANICAL VIEW
    THE KINETIC THEORY OF MATTER
    AVAGADRO’S NUMBER –> WEIGHT OF ATOMS
    > In the kinetic theory of matter and in all its important achievements we see the realization of the general philosophical programme: to reduce the explanation of all phenomena to the interaction between particles of matter.

  • vinaire  On March 9, 2014 at 2:37 PM

    > Heat must be mechanical energy if every problem is a mechanical one.
    > More heat in the vessel [containing gas molecules] means a greater average kinetic energy.
    > Heat is just the kinetic energy of molecular motion.
    > To any definite temperature there corresponds a definite average kinetic energy per molecule.
    > Kinetic theory predicts that pressure would increase as gas is compressed.
    > Kinetic theory predicts that at the same presure, volume and temperature, the number of molecules would be the same.
    > It explains quantitatively as well as qualitatively the laws of gases as determined by experiment.
    > A fall in the temperature of matter means a decrease in the average kinetic energy of its particles.
    > It is therefore clear that the average kinetic energy of a liquid particle is smaller than that of a corresponding gas particle.
    > Kinetic theory of matter also explains the mysterious Brownian Motion.
    > Thus, the bombarding particles (molecules) have mass and velocity.
    .

  • vinaire  On March 9, 2014 at 2:50 PM

    From The Evolution of Physics:

    In mechanics the future path of a moving body can be predicted and its past disclosed if its present condition and the forces acting upon it are known. Thus, for example, the future paths of all planets can be foreseen. The active forces are Newton’s gravitational forces depending on the distance alone. The great results of classical mechanics suggest that the mechanical view can be consistently applied to all branches of physics, that all phenomena can be explained by the action of forces representing either attraction or repulsion, depending only upon distance and acting between unchangeable particles.

    In the kinetic theory of matter we see how this view, arising from mechanical problems, embraces the phenomena of heat and how it leads to a successful picture of the structure of matter.

    .

  • vinaire  On March 9, 2014 at 2:56 PM

    II. THE DECLINE OF THE MECHANICAL VIEW
    The two electric fluids
    The magnetic fluids
    The first serious difficulty
    The velocity of light
    Light as a substance
    The riddle of color
    What is a wave?
    The wave theory of light
    Longitudinal or transverse light waves?
    Ether and the mechanical view

    .

  • vinaire  On March 9, 2014 at 3:28 PM

    Example of a theory:
    There exist two electric fluids, one called positive ( + ) and the other negative ( – )… Two electric fluids of the same kind repel each other, while two of the opposite kind attract… There are two kinds of bodies, those in which the fluids can move freely, called conductors, and those in which they cannot, called insulators.

    The aim of every theory is to guide us to new facts, suggest new experiments, and lead to the discovery of new phenomena and new laws… There are no eternal theories in science… Every theory has its period of gradual development and triumph, after which it may experience a rapid decline… Nearly every great advance in science arises from a crisis in the old theory.
    .

  • vinaire  On March 9, 2014 at 3:44 PM

    A hundred years after Newton discovered the law ofgravitation, Coulomb found a similar dependence of electrical force on distance… But gravitational attraction is always present, while electric forces exist only if the bodies possess electric charges… In the gravitational case there is only attraction, but electric forces may either attract or repel… Like heat the electric fluids are also members of the family of weightless substances.
    .

  • vinaire  On March 9, 2014 at 3:57 PM

    > Analogy: Electric charge is like Heat
    > Analogy: Electric potential is like Temperature
    > The tendency of charge to escape from a conductor is a direct measure of its potentials.
    > ARBITRARY CONVENTION: The electric fluid flows from the conductor having the higher (+) potential to that having the lower (-).

  • vinaire  On March 9, 2014 at 7:15 PM

    From The Evolution of Physics:

    Although we can consistently carry out the mechanical view in the domain of electric and magnetic phenomena introduced here, there is no reason to be particularly proud or pleased about it. Some features of the theory are certainly unsatisfactory if not discouraging. New kinds of substances had to be invented: two electric fluids and the elementary magnetic dipoles. The wealth of substances begins to be overwhelming!

    The forces are simple. They are expressible in a similar way for gravitational, electric, and magnetic forces. But the price paid for this simplicity is high: the introduction of new weightless substances. These are rather artificial concepts, and quite unrelated to the fundamental substance, mass.

    .

  • vinaire  On March 10, 2014 at 12:32 PM

    A magnet behaves like an electric dipole (two oppositely charged spheres separated by an insulator)… But the magnet consists of very small elementary magnetic dipoles which cannot be broken into separate poles… Order reigns in the magnet as a whole, for all the elementary dipoles are directed in the same way… The dependence of magnetic attraction or repulsion on distance is the same as in Newton’s law of gravitation and Coulomb’s law of electrostatics… We see again in this theory the application of a general point of view: the tendency to describe all phenomena by means of attractive and repulsive forces depending only on distance and acting between unchangeable particles.
    .

  • vinaire  On March 10, 2014 at 12:33 PM

    Then came the breakdown of the belief that all phenomena can be explained mechanically… In a Voltaic battery a higher potential in copper relative to zinc is maintained even when the two plates are connected… There seems to be an unlimited supply of an endless current of “electrical fluid”… This is similar to unlimited supply of “heat fluid” when boring the cannons… In an attempt to save the fluid theory, we may assume that some constant force acts to regenerate the potential difference and cause a flow of electric fluid… from the standpoint of energy, a noticeable quantity of heat is generated in the wire carrying the current… this is the chain of transformations which are taking place: chemical energy -> energy of the flowing electric fluid, i.e., the current -> heat.
    .

  • vinaire  On March 10, 2014 at 12:34 PM

    The experiment which actually revealed the great difficulties in applying the mechanical ideas is as follows… When a circuit is closed initiating a surge of current in a ring of wire, it generates a force perpendicular to the plane of wire. This force is observed in the movement of a magnetic needle… This experiment shows a relation between two apparently quite different phenomena, magnetism and electric current. It also shows that the force between the magnetic pole and the small portions of the wire through which the current flows does not lie along lines connecting the wire and needle, or the particles of flowing electric fluid and the elementary magnetic dipoles.

    For the first time there appears a force quite different from that to which, according to our mechanical point of view, we intended to reduce all actions in the external world.
    .

  • vinaire  On March 10, 2014 at 2:56 PM

    From The Evolution of Physics:

    This difficulty was stressed even more by an experiment performed with great skill by Rowland nearly sixty years ago. Leaving out technical details, this experiment could be described as follows. Imagine a small charged sphere. Imagine further that this sphere moves very fast in a circle at the centre of which is a magnetic needle. This is, in principle, the same experiment as Oersted’s, the only difference being that instead of an ordinary current we have a mechanically effected motion of the electric charge. Rowland found that the result is indeed similar to that observed when a current flows in a circular wire. The magnet is deflected by a perpendicular force.

    Let us now move the charge faster. The force acting on the magnetic pole is, as a result, increased; the deflection from its initial position becomes more distinct. This observation presents another grave complication. Not only does the force fail to lie on the line connecting charge and magnet, but the intensity of the force depends on the velocity of the charge. The whole mechanical point of view was based on the belief that all phenomena can be explained in terms of forces depending only on the distance and not on the velocity. The result of Rowland’s experiment certainly shakes this belief. Yet we may choose to be conservative and seek a solution within the frame of old ideas.

    .

  • vinaire  On March 12, 2014 at 8:16 AM

    From The Evolution of Physics:

    In the old theories of electric fluids, in the corpuscular and wave theories of light, we witness the further attempts to apply the mechanical view. But in the realm of electric and optical phenomena we meet grave difficulties in this application.

    A moving charge acts upon a magnetic needle. But the force, instead of depending only upon distance, depends also upon the velocity of the charge. The force neither repels not attracts but acts perpendicular to the line connecting the needle and the charge.

    In optics we have to decide in favour of the wave theory against the corpuscular theory of light. Waves spreading in a medium consisting of particles, with mechanical forces acting between them, are certainly a mechanical concept. But what is the medium through which light spreads and what are its mechanical properties? There is no hope of reducing the optical phenomena to the mechanical ones before this question is answered. But the difficulties in solving this problem are so great that we have to give it up and thus give up the mechanical views as well.

    .

  • vinaire  On March 12, 2014 at 4:21 PM

    From The Evolution of Physics – III. FIELD, RELATIVITY – The field as representation

    > We know from mechanical view that two particles attract each other and that this force of attraction decreases with the square of the distance.
    > Imagine a 3D space with sun at the center. Any test body brought somewhere within the vicinity of the sun will be attracted along the line connecting the centres of the two bodies.
    > We can imagine such lines directed toward the sun from all around the sun for different positions of the test body.
    > We may view these as lines of force of the gravitational field of the sun that are constructed in space, where no matter is present.
    > These lines only indicate how a test body would behave if brought into the vicinity of the sphere for which the field is constructed.
    > The lines in our space model are always perpendicular to the surface of the sphere.
    > Since they diverge from one point, they are dense near the sphere and become less and less so farther away.
    > If we increase the distance from the sphere twice or three times, then the density of the lines will be four or nine times less.
    > Thus, the density of the lines of force in space shows how the force varies with the distance.
    > The lines of force help explain the force generated by a circulating charge that is perpendicular to its plane, which cannot be explained by the traditional mechanical view.
    > This is “lines of force” or “field” model. The mechanical model was two-dimensional. This model is three-dimensional.
    > The properties of the field alone appear to be essential for the description of phenomena; the differences in source do not matter.
    > The concept of field reveals its importance by leading to new experimental facts.
    > The field translates the laws into a simple, clear language, easily understood.
    > an electrostatic field does not influence a magnetostatic one and vice versa. The words “static field” mean a field that does not change with time.
    > Electrostatic, magnetostatic and gravitational fields are all of different character. They do not mix; each preserves its individuality regardless of the others.
    > As long as a charge is at rest there is only an electro static field. But a magnetic field appears as soon as the charge begins to move.
    > the faster the electric field changes, the stronger the accompanying magnetic field.

    We have tried here to translate familiar facts from the language of fluids, constructed according to the old mechanical view, into the new language of fields. We shall see later how clear, instructive, and far
    reaching our new language is.

    .

  • vinaire  On March 12, 2014 at 9:27 PM

    From The Evolution of Physics – III. FIELD, RELATIVITY – The two pillars of the field theory

    > “The change of an electric field is accompanied by a magnetic field.”
    > “The change of a magnetic field is accompanied by an electric field.”
    > New facts suggested by the field theory are confirmed by experiment!
    > To use the field concept and its language consistently, we must regard the magnetic field as a store of energy. Only in this way shall we be able to describe the electric and magnetic phenomena in accordance with the law of conservation of energy.

    Starting as a helpful model, the field became more and more real. It helped us to understand old facts and led us to new ones. The attribution of energy to the field is one step farther in the development in which the field concept was stressed more and more, and the concepts of substances, so essential to the mechanical point of view, were more and more suppressed.

    .

  • vinaire  On March 13, 2014 at 7:00 AM

    From The Evolution of Physics – III. FIELD, RELATIVITY – The reality of the field

    > The quantitative, mathematical description of the laws of the field is summed up in what are called Maxwell’s equations.
    > These equations form a pattern for a new type of law.
    > Maxwell’s equations are laws representing the structure of the field.
    > One of the principal steps leading to Maxwell’s equations is an idealized experiment performed in imagination by repeating Faraday’s experiment with a circuit shrinking to a point. We may imagine the same with Oersted’s experiment.
    > the whole step yields a connection between the changes of the magnetic and electric fields at an arbitrary point in space and at an arbitrary instant.
    > the electromagnetic field is, in Maxwell’s theory, something real. The electric field is produced by a changing magnetic field, quite independently, whether or not there is a wire to test its existence; a magnetic field is produced by a changing electric field, whether or not there is a magnetic pole to test its existence.
    > the electromagnetic field once created exists, acts, and changes according to Maxwell’s laws.
    > Maxwell’s equations describe the structure of the electromagnetic field. All space is the scene of these laws and not, as for mechanical laws, only points in which matter or charges are present.
    > In Newton’s theory only big steps connecting distant events are permissible. In Maxwell’s theory there are no material actors. The equations allow us to predict what will happen a little farther in space and a little later in time, if we know what happens here and now. They allow us to increase our knowledge of the field by small steps.
    > the study of Maxwell’s equations gives a much deeper insight into the problem of the oscillating electric charge. It predicts the electromagnetic wave. Energy radiates from the oscillating charge travelling with a definite speed through space.
    > As field represents energy, all these changes spreading out in space, with a definite velocity, produce a wave.
    > The electromagnetic wave spreads in empty space. This, again, is a consequence of the theory.
    > (Vinaire) An electromagnetic wave travels in space. But what is that space? Is that space a distant harmonic?
    > From Maxwell’s equations: the velocity of an electromagnetic wave is equal to the velocity of light.
    > The theoretical discovery of an electromagnetic wave spreading with the speed of light is one of the greatest achievements in the history of science.
    .

  • vinaire  On March 13, 2014 at 11:27 AM

    For the first time I have understood the deep revolutionary aspect of the Maxwell’s Equations..

    The idea of FIELD started with Faraday. It was put forth as a theory by Maxwell. This provided a new reality that was firmly put in place by Einstein’s Theory of Relativity.

  • vinaire  On March 13, 2014 at 2:31 PM

    From “The Evolution of Physics”:

    To use a comparison, we could say that creating a new theory is not like destroying an old barn and erecting a skyscraper in its place. lt is rather like climbing a mountain, gaining new and wider views, discovering unexpected connections between our starting point and its rich environment. But the point from which we started out still exists and can be seen, although it appears smaller and forms a tiny part of our broad view gained by the mastery of the obstacles on our adventurous way up.

    .

  • vinaire  On March 13, 2014 at 2:38 PM

    From “The Evolution of Physics” – III. FIELD, RELATIVITY – Field and Ether

    > The electromagnetic wave is a transverse one and is propagated with the velocity of light in empty space.
    > The fact that their velocities are the same suggests a close relationship between optical and electromagnetic phenomena.
    > The same Maxwell’s equations describe both electric induction and optical refraction.
    > From the physical point of view, the only difference between an ordinary electromagnetic wave and a light wave is the wave-length: this is very small for light waves, detected by the human eye, and great for ordinary electromagnetic waves, detected by a radio receiver.
    > The physicist of the early years tried to describe the action of two electric charges only by concepts referring directly to the two charges. The field did not exist for him. The electromagnetic field is, for the modern physicist, as real as the chair on which he sits.
    > The new theory shows the merits as well as the limitations of the old theory and allows us to regain our old concepts from a higher level.
    > Our only way out seems to be to take for granted the fact that space has the physical property of transmitting electromagnetic waves, and not to bother too much about the meaning of this statement.
    > We may still use the word ether, but only to express some physical property of space.
    .

    • Chris Thompson  On March 13, 2014 at 6:04 PM

      We may call it either or we may call it a field, but it looks like we may be talking about the raw properties of space.

    • vinaire  On March 13, 2014 at 7:20 PM

      As a scientist, Einstein is very careful in what he writes. You’ll get a better idea by reading this section.

  • vinaire  On March 14, 2014 at 9:34 AM

    From “The Evolution of Physics” – III. FIELD, RELATIVITY – The mechanical scaffold

    > The earth is our co-ordinate system and it is rotaing.
    > The observation of the law of inertia on earth deviates slighly from a simple statement of it, because of its rotation.
    > We use a mechanical scaffold, called the frame of reference, or coordinate system, to measure any location in space and time.
    > If two coordinate systems rotate with respect to each other, then the laws of mechanics cannot be valid in both.
    > Galilean relativity principle: if the laws of mechanics are valid in one c.s., then they are valid in any other c.s. moving uniformly relative to the first.
    > Inertial systems are those for which the laws of mechanics are valid. The question as to whether an inertial system exists at all is still unsettled.
    > We can always transform not only positions, but also velocities from one c.s. to another if we know the relative velocities of the two c.s.
    > The distance of two points is, however, invariant, that is, independent of the choice of the c.s. Similarly, another quantity independent of the c.s. is the change of velocity.

    Our conclusions can be summarized as follows :

    (1) We know of no rule for finding an inertial system. Given one, however, we can find an infinite number, since all c.s. moving uniformly, relative to each other, are inertial systems if one of them is.

    (2) The time corresponding to an event is the same in all c.s. But the co-ordinates and velocities are different, and change according to the transformation laws.

    (3) Although the co-ordinates and velocity change when passing from one c.s. to another, the force and change of velocity, and therefore the laws of mechanics are invariant with respect to the transformation laws.

    .

  • vinaire  On March 15, 2014 at 5:20 AM

    From “The Evolution of Physics” – III. FIELD, RELATIVITY – Ether and motion

    > The Galilean relativity principle is valid for mechanical phenomena. The same laws of mechanics apply to all inertial systems moving relative to each other. Is this principle also valid for non-mechanical phenomena?
    > All problems concentrated around this question immediately bring us to the starting-point of the relativity theory.
    > In case of sound the medium also moves with the source of sound (or the c.s.) and the classical transformation applies.
    > In the case of light, there is no mechanical medium that moves with the c.s. or with the source of light.
    > Indirect experimentation shows that the velocity of light is always the same in all c.s. independent of whether or not the emitting source moves, or how it moves.
    .

  • vinaire  On March 15, 2014 at 5:29 AM

    (Vinaire) The medium that helps sound propagate is at the same disturbance level as the source of sound. But the medium of light (field) that helps light propagate is at a very different disturbance level as the source of light. The mechanical c.s. is tied to the mechanical source.

    In case of sound the source as well as the medium of sound is rigidly connected to the c.s. (coordinate system) because they belong to the same disturbance level (DL100).

    In case of light, the source of light is considered to be mechanical (DL100), but the medium of light is considered to be a field, which is at the disturbance level of DL50.

    How can a DL100 be the source of DL50?
    .

  • vinaire  On March 15, 2014 at 5:33 AM

    How do we consider the motion in DL100 relative to the motion in DL50?

    .

    • vinaire  On March 15, 2014 at 5:37 AM

      The classical transformations apply only when both c.s. are at DL100.
      .

    • vinaire  On March 15, 2014 at 5:45 AM

      DL50 seems to make the background for motion at DL100. Here we have two very different relative motions. There is relative motion at DL100. Then there is relativity of DL100 with respect to DL50.

      This is similar to the time dimension where motion is occurring in the present. But the whole “plane of present” can be looked upon in some historical perspective in a much larger sense of time.

      .

    • vinaire  On March 15, 2014 at 5:54 AM

      In case of sound, the vibration of the object creates displacement in the medium. Both the vibrating object and the displaced medium are at the same macro level.

      In case of light, the “vibration” is occurring at a subatomic level, and so is the displacement of “media”. It is a whole different level.

      Motion at macro level may be compared to another motion at macro level. Similarly, motion at subatomic level may be compared to another motion at subatomic level.

      How can the motion at subatomic level be compared to the motion at macro level in any significant manner?
      .

  • vinaire  On March 15, 2014 at 5:56 AM

    This seems to be a problem of scales in the realm of relativity.
    .

    • vinaire  On March 15, 2014 at 6:16 AM

      It is also a problem of levels. A macro level cannot “operate” at subatomic level. A macro object is inherently incapbale of motion at subatomic level.

      It is ludicrous to think of a macro object moving at the speed of light. It would be like thinking of a stone shrinking to the size of an electron.

    • vinaire  On March 15, 2014 at 6:18 AM

      All the ridiculous projections from Einsteins Theory of Relativity are simply that – ridiculous projections.
      .

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