Thursday, 29 July 2010

Speculations: nature of matter: lines of force

~~An extract~~

The lines of force have their roots in the magnet, and though they may expand into infinite space, they eventually return to the magnet. Now these lines may be intersected close to the magnet or at a distance from it. Faraday finds distance to be perfectly immaterial so long as the number of lines intersected is the same. For example, when the loop connecting the equator and the pole of his barmagnet performs one complete revolution round the magnet, it is manifest that all the lines of force issuing from the magnet are once intersected. Now it matters not whether the loop be ten feet or ten inches in length, it matters not how it may be twisted and contorted, it matters not how near to the magnet or how distant from it the loop may be, one revolution always produces the same amount of current electricity, because in all these cases all the lines of force issuing from the magnet are once intersected and no more.

From the external portion of the circuit he passes in idea to the internal, and follows the lines of force into the body of the magnet itself. His conclusion is that there exist lines of force within the magnet of the same nature as those without. What is more, they are exactly equal in amount to those without. They have a relation in direction to those without; and in fact are continuations of them.... 'Every line of force, therefore, at whatever distance it may be taken from the magnet, must be considered as a closed circuit, passing in some part of its course through the magnet, and having an equal amount of force in every part of its course.'

Discovery of diamagnetism--researches on magne-crystallic action.

~~An extract~~

Faraday's thoughts ran intuitively into experimental combinations, so that subjects whose capacity for experimental treatment would, to ordinary minds, seem to be exhausted in a moment, were shown by him to be all but inexhaustible. He has now an object in view, the first step towards which is the proof that the principle of Archimedes is true of magnetism. He forms magnetic solutions of various degrees of strength, places them between the poles of his magnet, and suspends in the solutions various magnetic bodies. He proves that when the solution is stronger than the body plunged in it, the body, though magnetic, is repelled; and when an elongated piece of it is surrounded by the solution, it sets, like a diamagnetic body, equatorially between the excited poles. The same body when suspended in a solution of weaker magnetic power than itself, is attracted as a whole, while an elongated portion of it sets axially.

...After the description of the general character of this new force, Faraday states with the emphasis here reproduced its mode of action: 'The law of action appears to be that the line or axis of MAGNE-CRYSTALLIC force (being the resultant of the action of all the molecules) tends to place itself parallel, or as a tangent, to the magnetic curve, or line of magnetic force, passing through the place where the crystal is situated.' The magne-crystallic force, moreover, appears to him 'to be clearly distinguished from the magnetic or diamagnetic forces, in that it causes neither approach nor recession, consisting not in attraction or repulsion, but in giving a certain determinate position to the mass under its influence.' And then he goes on 'very carefully to examine and prove the conclusion that there was no connection of the force with attractive or repulsive influences.' With the most refined ingenuity he shows that, under certain circumstances, the magne-crystallic force can cause the centre of gravity of a highly magnetic body to retreat from the poles, and the centre of gravity of a highly diamagnetic body to approach them. His experiments root his mind more and more firmly in the conclusion that 'neither attraction nor repulsion causes the set, or governs the final position' of the crystal in the magnetic field. That the force which does so is therefore 'distinct in its character and effects from the magnetic and diamagnetic forms of force. On the other hand,' he continues, 'it has a most manifest relation to the crystalline structure of bismuth and other bodies, and therefore to the power by which their molecules are able to build up the crystalline masses.'

And here follows one of those expressions which characterize the conceptions of Faraday in regard to force generally:--'It appears to me impossible to conceive of the results in any other way than by a mutual reaction of the magnetic force, and the force of the particles of the crystals upon each other.' He proves that the action of the force, though thus molecular, is an action at a distance; he shows that a bismuth crystal can cause a freely suspended magnetic needle to set parallel to its magne-crystallic axis. Few living men are aware of the difficulty of obtaining results like this, or of the delicacy necessary to their attainment. 'But though it thus takes up the character of a force acting at a distance, still it is due to that power of the particles which makes them cohere in regular order and gives the mass its crystalline aggregation, which we call at other times the attraction of aggregation, and so often speak of as acting at insensible distances.' Thus he broods over this new force, and looks at it from all possible points of inspection. Experiment follows experiment, as thought follows thought. He will not relinquish the subject as long as a hope exists of throwing more light upon it. He knows full well the anomalous nature of the conclusion to which his experiments lead him. But experiment to him is final, and he will not shrink from the conclusion. 'This force,' he says, 'appears to me to be very strange and striking in its character. It is not polar, for there is no attraction or repulsion.' And then, as if startled by his own utterance, he asks--'What is the nature of the mechanical force which turns the crystal round, and makes it affect a magnet?'... 'I do not remember,' he continues 'heretofore such a case of force as the present one, where a body is brought into position only, without attraction or repulsion.'

Plucker, the celebrated geometer already mentioned, who pursued experimental physics for many years of his life with singular devotion and success, visited Faraday in those days, and repeated before him his beautiful experiments on magneto-optic action. Faraday repeated and verified Plucker's observations, and concluded, what he at first seemed to doubt, that Plucker's results and magne-crystallic action had the same origin.

At the end of his papers, when he takes a last look along the line of research, and then turns his eyes to the future, utterances quite as much emotional as scientific escape from Faraday. 'I cannot,' he says, at the end of his first paper on magne-crystallic action, 'conclude this series of researches without remarking how rapidly the knowledge of molecular forces grows upon us, and how strikingly every investigation tends to develop more and more their importance, and their extreme attraction as an object of study. A few years ago magnetism was to us an occult power, affecting only a few bodies, now it is found to influence all bodies, and to possess the most intimate relations with electricity, heat, chemical action, light, crystallization, and through it, with the forces concerned in cohesion; and we may, in the present state of things, well feel urged to continue in our labours, encouraged by the hope of bringing it into a bond of union with gravity itself.'

The law of action in relation to this point is, that in diamagnetic crystals, the line along which the repulsion is a maximum, sets equatorially in the magnetic field; while in magnetic crystals the line along which the attraction is a maximum sets from pole to pole. Faraday had said that the magne-crystallic force was neither attraction nor repulsion. Thus far he was right. It was neither taken singly, but it was both. By the combination of the doctrine of diamagnetic polarity with these differential attractions and repulsions, and by paying due regard to the character of the magnetic field, every fact brought to light in the domain of magne-crystallic action received complete explanation. The most perplexing of those facts were shown to result from the action of mechanical couples, which the proved polarity both of magnetism and diamagnetism brought into play. Indeed the thoroughness with which the experiments of Faraday were thus explained, is the most striking possible demonstration of the marvellous precision with which they were executed.
~~Author: John Tyndall

Faraday As A Discoverer

~~An extract~~

Discovery of Magneto-electricity: Explanation of Argo's magnetism of rotation: Terrestrial magneto-electric induction: The extra current.

The work thus referred to, though sufficient of itself to secure no mean scientific reputation, forms but the vestibule of Faraday's achievements. He had been engaged within these walls for eighteen years. During part of the time he had drunk in knowledge from Davy, and during the remainder he continually exercised his capacity for independent inquiry. In 1831 we have him at the climax of his intellectual strength, forty years of age, stored with knowledge and full of original power. Through reading, lecturing, and experimenting, he had become thoroughly familiar with electrical science: he saw where light was needed and expansion possible. The phenomena of ordinary electric induction belonged, as it were, to the alphabet of his knowledge: he knew that under ordinary circumstances the presence of an electrified body was sufficient to excite, by induction, an unelectrified body. He knew that the wire which carried an electric current was an electrified body, and still that all attempts had failed to make it excite in other wires a state similar to its own.

What was the reason of this failure? Faraday never could work from the experiments of others, however clearly described. He knew well that from every experiment issues a kind of radiation, luminous in different degrees to different minds, and he hardly trusted himself to reason upon an experiment that he had not seen. In the autumn of 1831 he began to repeat the experiments with electric currents, which, up to that time, had produced no positive result. And here, for the sake of younger inquirers, if not for the sake of us all, it is worth while to dwell for a moment on a power which Faraday possessed in an extraordinary degree. He united vast strength with perfect flexibility. His momentum was that of a river, which combines weight and directness with the ability to yield to the flexures of its bed. The intentness of his vision in any direction did not apparently diminish his power of perception in other directions; and when he attacked a subject, expecting results he had the faculty of keeping his mind alert, so that results different from those which he expected should not escape him through preoccupation.

He began his experiments 'on the induction of electric currents' by composing a helix of two insulated wires which were wound side by side round the same wooden cylinder. One of these wires he connected with a voltaic battery of ten cells, and the other with a sensitive galvanometer. When connection with the battery was made, and while the current flowed, no effect whatever was observed at the galvanometer. But he never accepted an experimental result, until he had applied to it the utmost power at his command. He raised his battery from 10 cells to 120 cells, but without avail. The current flowed calmly through the battery wire without producing, during its flow, any sensible result upon the galvanometer.

'During its flow,' and this was the time when an effect was expected-- but here Faraday's power of lateral vision, separating, as it were, from the line of expectation, came into play--he noticed that a feeble movement of the needle always occurred at the moment when he made contact with the battery; that the needle would afterwards return to its former position and remain quietly there unaffected by the flowing current. At the moment, however, when the circuit was interrupted the needle again moved, and in a direction opposed to that observed on the completion of the circuit.

This result, and others of a similar kind, led him to the conclusion 'that the battery current through the one wire did in reality induce a similar current through the other; but that it continued for an instant only, and partook more of the nature of the electric wave from a common Leyden jar than of the current from a voltaic battery.' The momentary currents thus generated were called induced currents, while the current which generated them was called the inducing current. It was immediately proved that the current generated at making the circuit was always opposed in direction to its generator, while that developed on the rupture of the circuit coincided in direction with the inducing current. It appeared as if the current on its first rush through the primary wire sought a purchase in the secondary one, and, by a kind of kick, impelled backward through the latter an electric wave, which subsided as soon as the primary current was fully established.

Faraday, for a time, believed that the secondary wire, though quiescent when the primary current had been once established, was not in its natural condition, its return to that condition being declared by the current observed at breaking the circuit. He called this hypothetical state of the wire the electro-tonic state: he afterwards abandoned this hypothesis, but seemed to return to it in later life. The term electro-tonic is also preserved by Professor Du Bois Reymond to express a certain electric condition of the nerves, and Professor Clerk Maxwell has ably defined and illustrated the hypothesis in the Tenth Volume of the 'Transactions of the Cambridge Philosophical Society.'

The mere approach of a wire forming a closed curve to a second wire through which a voltaic current flowed was then shown by Faraday to be sufficient to arouse in the neutral wire an induced current, opposed in direction to the inducing current; the withdrawal of the wire also generated a current having the same direction as the inducing current; those currents existed only during the time of approach or withdrawal, and when neither the primary nor the secondary wire was in motion, no matter how close their proximity might be, no induced current was generated.

Faraday has been called a purely inductive philosopher. A great deal of nonsense is, I fear, uttered in this land of England about induction and deduction. Some profess to befriend the one, some the other, while the real vocation of an investigator, like Faraday, consists in the incessant marriage of both. He was at this time full of the theory of Ampere, and it cannot be doubted that numbers of his experiments were executed merely to test his deductions from that theory. Starting from the discovery of Oersted, the illustrious French philosopher had shown that all the phenomena of magnetism then known might be reduced to the mutual attractions and repulsions of electric currents. Magnetism had been produced from electricity, and Faraday, who all his life long entertained a strong belief in such reciprocal actions, now attempted to effect the evolution of electricity from magnetism. Round a welded iron ring he placed two distinct coils of covered wire, causing the coils to occupy opposite halves of the ring. Connecting the ends of one of the coils with a galvanometer, he found that the moment the ring was magnetised, by sending a current through the other coil, the galvanometer needle whirled round four or five times in succession. The action, as before, was that of a pulse, which vanished immediately. On interrupting the circuit, a whirl of the needle in the opposite direction occurred. It was only during the time of magnetization or demagnetization that these effects were produced. The induced currents declared a change of condition only, and they vanished the moment the act of magnetization or demagnetization was complete.

The effects obtained with the welded ring were also obtained with straight bars of iron. Whether the bars were magnetised by the electric current, or were excited by the contact of permanent steel magnets, induced currents were always generated during the rise, and during the subsidence of the magnetism. The use of iron was then abandoned, and the same effects were obtained by merely thrusting a permanent steel magnet into a coil of wire. A rush of electricity through the coil accompanied the insertion of the magnet; an equal rush in the opposite direction accompanied its withdrawal. The precision with which Faraday describes these results, and the completeness with which he defines the boundaries of his facts, are wonderful. The magnet, for example, must not be passed quite through the coil, but only half through; for if passed wholly through, the needle is stopped as by a blow, and then he shows how this blow results from a reversal of the electric wave in the helix. He next operated with the powerful permanent magnet of the Royal Society, and obtained with it, in an exalted degree, all the foregoing phenomena.

And now he turned the light of these discoveries upon the darkest physical phenomenon of that day. Arago had discovered, in 1824, that a disk of non-magnetic metal had the power of bringing a vibrating magnetic needle suspended over it rapidly to rest; and that on causing the disk to rotate the magnetic needle rotated along with it. When both were quiescent, there was not the slightest measurable attraction or repulsion exerted between the needle and the disk; still when in motion the disk was competent to drag after it, not only a light needle, but a heavy magnet. The question had been probed and investigated with admirable skill both by Arago and Ampere, and Poisson had published a theoretic memoir on the subject; but no cause could be assigned for so extraordinary an action. It had also been examined in this country by two celebrated men, Mr. Babbage and Sir John Herschel; but it still remained a mystery. Faraday always recommended the suspension of judgment in cases of doubt. 'I have always admired,' he says, 'the prudence and philosophical reserve shown by M. Arago in resisting the temptation to give a theory of the effect he had discovered, so long as he could not devise one which was perfect in its application, and in refusing to assent to the imperfect theories of others.' Now, however, the time for theory had come. Faraday saw mentally the rotating disk, under the operation of the magnet, flooded with his induced currents, and from the known laws of interaction between currents and magnets he hoped to deduce the motion observed by Arago. That hope he realised, showing by actual experiment that when his disk rotated currents passed through it, their position and direction being such as must, in accordance with the established laws of electro-magnetic action, produce the observed rotation.

Introducing the edge of his disk between the poles of the large horseshoe magnet of the Royal Society, and connecting the axis and the edge of the disk, each by a wire with a galvanometer, he obtained, when the disk was turned round, a constant flow of electricity. The direction of the current was determined by the direction of the motion, the current being reversed when the rotation was reversed. He now states the law which rules the production of currents in both disks and wires, and in so doing uses, for the first time, a phrase which has since become famous. When iron filings are scattered over a magnet, the particles of iron arrange themselves in certain determinate lines called magnetic curves. In 1831, Faraday for the first time called these curves 'lines of magnetic force'; and he showed that to produce induced currents neither approach to nor withdrawal from a magnetic source, or centre, or pole, was essential, but that it was only necessary to cut appropriately the lines of magnetic force. Faraday's first paper on Magneto-electric Induction, which I have here endeavoured to condense, was read before the Royal Society on the 24th of November, 1831.

On January 12, 1832, he communicated to the Royal Society a second paper on Terrestrial Magneto-electric Induction, which was chosen as the Bakerian Lecture for the year. He placed a bar of iron in a coil of wire, and lifting the bar into the direction of the dipping needle, he excited by this action a current in the coil. On reversing the bar, a current in the opposite direction rushed through the wire. The same effect was produced when, on holding the helix in the line of dip, a bar of iron was thrust into it. Here, however, the earth acted on the coil through the intermediation of the bar of iron. He abandoned the bar and simply set a copper plate spinning in a horizontal plane; he knew that the earth's lines of magnetic force then crossed the plate at an angle of about 70degrees. When the plate spun round, the lines of force were intersected and induced currents generated, which produced their proper effect when carried from the plate to the galvanometer. 'When the plate was in the magnetic meridian, or in any other plane coinciding with the magnetic dip, then its rotation produced no effect upon the galvanometer.'

At the suggestion of a mind fruitful in suggestions of a profound and philosophic character--I mean that of Sir John Herschel-- Mr. Barlow, of Woolwich, had experimented with a rotating iron shell. Mr. Christie had also performed an elaborate series of experiments on a rotating iron disk. Both of them had found that when in rotation the body exercised a peculiar action upon the magnetic needle, deflecting it in a manner which was not observed during quiescence; but neither of them was aware at the time of the agent which produced this extraordinary deflection. They ascribed it to some change in the magnetism of the iron shell and disk.

But Faraday at once saw that his induced currents must come into play here, and he immediately obtained them from an iron disk. With a hollow brass ball, moreover, he produced the effects obtained by Mr. Barlow. Iron was in no way necessary: the only condition of success was that the rotating body should be of a character to admit of the formation of currents in its substance: it must, in other words, be a conductor of electricity. The higher the conducting power the more copious were the currents. He now passes from his little brass globe to the globe of the earth. He plays like a magician with the earth's magnetism. He sees the invisible lines along which its magnetic action is exerted, and sweeping his wand across these lines evokes this new power. Placing a simple loop of wire round a magnetic needle he bends its upper portion to the west: the north pole of the needle immediately swerves to the east: he bends his loop to the east, and the north pole moves to the west. Suspending a common bar magnet in a vertical position, he causes it to spin round its own axis. Its pole being connected with one end of a galvanometer wire, and its equator with the other end, electricity rushes round the galvanometer from the rotating magnet. He remarks upon the 'singular independence' of the magnetism and the body of the magnet which carries it. The steel behaves as if it were isolated from its own magnetism.

And then his thoughts suddenly widen, and he asks himself whether the rotating earth does not generate induced currents as it turns round its axis from west to east. In his experiment with the twirling magnet the galvanometer wire remained at rest; one portion of the circuit was in motion relatively to another portion. But in the case of the twirling planet the galvanometer wire would necessarily be carried along with the earth; there would be no relative motion. What must be the consequence? Take the case of a telegraph wire with its two terminal plates dipped into the earth, and suppose the wire to lie in the magnetic meridian. The ground underneath the wire is influenced like the wire itself by the earth's rotation; if a current from south to north be generated in the wire, a similar current from south to north would be generated in the earth under the wire; these currents would run against the same terminal plate, and thus neutralise each other.

This inference appears inevitable, but his profound vision perceived its possible invalidity. He saw that it was at least possible that the difference of conducting power between the earth and the wire might give one an advantage over the other, and that thus a residual or differential current might be obtained. He combined wires of different materials, and caused them to act in opposition to each other, but found the combination ineffectual. The more copious flow in the better conductor was exactly counterbalanced by the resistance of the worse. Still, though experiment was thus emphatic, he would clear his mind of all discomfort by operating on the earth itself. He went to the round lake near Kensington Palace, and stretched 480 feet of copper wire, north and south, over the lake, causing plates soldered to the wire at its ends to dip into the water. The copper wire was severed at the middle, and the severed ends connected with a galvanometer. No effect whatever was observed. But though quiescent water gave no effect, moving water might. He therefore worked at London Bridge for three days during the ebb and flow of the tide, but without any satisfactory result. Still he urges, 'Theoretically it seems a necessary consequence, that where water is flowing there electric currents should be formed. If a line be imagined passing from Dover to Calais through the sea, and returning through the land, beneath the water, to Dover, it traces out a circuit of conducting matter one part of which, when the water moves up or down the channel, is cutting the magnetic curves of the earth, whilst the other is relatively at rest.... There is every reason to believe that currents do run in the general direction of the circuit described, either one way or the other, according as the passage of the waters is up or down the channel.' This was written before the submarine cable was thought of, and he once informed me that actual observation upon that cable had been found to be in accordance with his theoretic deduction.[1]

Three years subsequent to the publication of these researches-- that is to say, on January 29, 1835--Faraday read before the Royal Society a paper 'On the influence by induction of an electric current upon itself.' A shock and spark of a peculiar character had been observed by a young man named William Jenkin, who must have been a youth of some scientific promise, but who, as Faraday once informed me, was dissuaded by his own father from having anything to do with science. The investigation of the fact noticed by Mr. Jenkin led Faraday to the discovery of the extra current, or the current induced in the primary wire itself at the moments of making and breaking contact, the phenomena of which he described and illustrated in the beautiful and exhaustive paper referred to.

Seven-and-thirty years have passed since the discovery of magneto-electricity; but, if we except the extra current, until quite recently nothing of moment was added to the subject. Faraday entertained the opinion that the discoverer of a great law or principle had a right to the 'spoils'--this was his term--arising from its illustration; and guided by the principle he had discovered, his wonderful mind, aided by his wonderful ten fingers, overran in a single autumn this vast domain, and hardly left behind him the shred of a fact to be gathered by his successors.

And here the question may arise in some minds, What is the use of it all? The answer is, that if man's intellectual nature thirsts for knowledge, then knowledge is useful because it satisfies this thirst. If you demand practical ends, you must, I think, expand your definition of the term practical, and make it include all that elevates and enlightens the intellect, as well as all that ministers to the bodily health and comfort of men. Still, if needed, an answer of another kind might be given to the question 'What is its use?' As far as electricity has been applied for medical purposes, it has been almost exclusively Faraday's electricity. You have noticed those lines of wire which cross the streets of London. It is Faraday's currents that speed from place to place through these wires. Approaching the point of Dungeness, the mariner sees an unusually brilliant light, and from the noble phares of La Heve the same light flashes across the sea. These are Faraday's sparks exalted by suitable machinery to sunlike splendour. At the present moment the Board of Trade and the Brethren of the Trinity House, as well as the Commissioners of Northern Lights, are contemplating the introduction of the Magneto-electric Light at numerous points upon our coasts; and future generations will be able to refer to those guiding stars in answer to the question. What has been the practical use of the labours of Faraday? But I would again emphatically say, that his work needs no such justification, and that if he had allowed his vision to be disturbed by considerations regarding the practical use of his discoveries, those discoveries would never have been made by him. 'I have rather,' he writes in 1831, 'been desirous of discovering new facts and new relations dependent on magneto-electric induction, than of exalting the force of those already obtained; being assured that the latter would find their full development hereafter.'

In 1817, when lecturing before a private society in London on the element chlorine, Faraday thus expressed himself with reference to this question of utility. 'Before leaving this subject, I will point out the history of this substance, as an answer to those who are in the habit of saying to every new fact. "What is its use?" Dr. Franklin says to such, "What is the use of an infant?" The answer of the experimentalist is, "Endeavour to make it useful." When Scheele discovered this substance, it appeared to have no use; it was in its infancy and useless state, but having grown up to maturity, witness its powers, and see what endeavours to make it useful have done.'

Footnote to Chapter 3

[1] I am indebted to a friend for the following exquisite morsel:--

'A short time after the publication of Faraday's first researches in magneto-electricity, he attended the meeting of the British Association at Oxford, in 1832. On this occasion he was requested by some of the authorities to repeat the celebrated experiment of eliciting a spark from a magnet, employing for this purpose the large magnet in the Ashmolean Museum. To this he consented, and a large party assembled to witness the experiments, which, I need not say, were perfectly successful. Whilst he was repeating them a dignitary of the University entered the room, and addressing himself to Professor Daniell, who was standing near Faraday, inquired what was going on. The Professor explained to him as popularly as possible this striking result of Faraday's great discovery. The Dean listened with attention and looked earnestly at the brilliant spark, but a moment after he assumed a serious countenance and shook his head; "I am sorry for it," said he, as he walked away; in the middle of the room he stopped for a moment and repeated, "I am sorry for it:" then walking towards the door, when the handle was in his hand he turned round and said, "Indeed I am sorry for it; it is putting new arms into the hands of the incendiary." This occurred a short time after the papers had been filled with the doings of the hayrick burners. An erroneous statement of what fell from the Dean's mouth was printed at the time in one of the Oxford papers. He is there wrongly stated to have said, "It is putting new arms into the hands of the infidel."'
~~Author: John Tyndall

Tuesday, 27 July 2010

James Prescott Joule

James Prescott Joule was born at Salford, England on Christmas Eve of the year 1818. His father and his grandfather before him were brewers, and the business, in due course, descended to Mr. Joule and his elder brother, and by them was carried on with success till it was sold, in 1854. Mr. Joule's grandfather came from Elton, in Derbyshire, settled near Manchester, where he founded the business, and died at the age of fifty-four, in 1799. His father, one of a numerous family, married a daughter of John Prescott of Wigan. They had five children, of whom James Prescott Joule was the second, and of whom three were sons--Benjamin, the eldest, James, and John--and two daughters--Alice and Mary. Mr. Joule's mother died in 1836 at the age of forty-eight; and his father, who was an invalid for many years before his death, died at the age of seventy-four, in the year 1858.

Young Joule was a delicate child, and was not sent to school. His early education was commenced by his mother's half sister, and was carried on at his father's house, Broomhill, Pendlebury, by tutors till he was about fifteen years of age. At fifteen he commenced working in the brewery, which, as his father's health declined, fell entirely into the hands of his brother Benjamin and himself.

Mr. Joule obtained his first instruction in physical science from Dalton, to whom his father sent the two brothers to learn chemistry. Dalton, one of the most distinguished chemists of any age or country, was then President of the Manchester Literary and Philosophical Society, and lived and received pupils in the rooms of the Society's house. Many of his most important memoirs were communicated to the Society, whose "Transactions" are likewise enriched by a large number of communications from his distinguished pupil. Dalton's instruction to the two young men commenced with arithmetic, algebra, and geometry. He then taught them natural philosophy out of Cavallo's text-book, and afterward, but only for a short time before his health gave way, in 1837, chemistry from his own "New System of Chemical Philosophy." "Profound, patient, intuitive," his teaching must have had great influence on his pupils. We find Mr. Joule early at work on the molecular constitution of gases, following in the footsteps of his illustrious master, whose own investigations on the constitution of mixed gases, and on the behavior of vapors and gases under heat, were among the most important of his day, and whose brilliant discovery of the atomic theory revolutionized the science of chemistry and placed him at the head of the philosophical chemists of Europe.

Under Dalton, Mr. Joule first became acquainted with physical apparatus; and the interest excited in his mind very soon began to produce fruit. Almost immediately he commenced experimenting on his own account. Obtaining a room in his father's house for the purpose, he began by constructing a cylinder electric machine in a very primitive way. A glass tube served for the cylinder; a poker hung up by silk threads, as in the very oldest forms of electric machine, was the prime conductor; and for a Leyden jar he went back to the old historical jar of Cunaeus, and used a bottle half filled with water, standing in an outer vessel, which contained water also.
Enlarging his stock of apparatus, chiefly by the work of his own hands, he soon entered the ranks as an investigator, and original papers followed each other in quick succession. The Royal Society list now contains, the titles of ninety-seven papers due to Joule, exclusive of over twenty very important papers detailing researches undertaken by him conjointly with Thomson, with Lyon Playfair, and with Scoresby.

Mr. Joule's first investigations were in the field of magnetism. In 1838, at the age of nineteen, he constructed an electro-magnetic engine, which he described in Sturgeon's "Annals of Electricity" for January of that year. In the same year, and in the three years following, he constructed other electro-magnetic machines and electro-magnets of novel forms; and experimenting with the new apparatus, he obtained results of great importance in the theory of electro-magnetism. In 1840 he discovered and determined the value of the limit to the magnetization communicable to soft iron by the electric current; showing for the case of an electro-magnet supporting weight, that when the exciting current is made stronger and stronger, the sustaining power tends to a certain definite limit, which, according to his estimate, amounts to about 140 lb. per square inch of either of the attracting surfaces. He investigated the relative values of solid iron cores for the electro-magnetic machine, as compared with bundles of iron wire; and, applying the principles which he had discovered, he proceeded to the construction of electro-magnets of much greater lifting power than any previously made, while he studied also the methods of modifying the distribution of the force in the magnetic field.

In commencing these investigations he was met at the very outset, as he tells us, with "the difficulty, if not impossibility, of understanding experiments and comparing them with one another, which arises in general from incomplete descriptions of apparatus, and from the arbitrary and vague numbers which are used to characterize electric currents. Such a practice," he says, "might be tolerated in the infancy of science; but in its present state of advancement greater precision and propriety are imperatively demanded. I have therefore determined," he continues, "for my own part to abandon my old quantity numbers, and to express my results on the basis of a unit which shall be at once scientific and convenient."

The discovery by Faraday of the law of electro-chemical equivalents had induced him to propose the voltameter as a measurer of electric currents, but the system proposed had not been used in the researches of any electrician, not excepting those of Faraday himself. Joule, realizing for the first time the importance of having a system of electric measurement which would make experimental results obtained at different times and under various circumstances comparable among themselves, and perceiving at the same time the advantages of a system of electric measurement dependent on, or at any rate comparable with, the chemical action producing the electric current, adopted as unit quantity of electricity the quantity required to decompose nine grains of water, 9 being the atomic weight of water, according to the chemical nomenclature then in use.

He had already made and described very important improvements in the construction of galvanometers, and he graduated his tangent galvanometer to correspond with the system of electric measurement he had adopted. The electric currents used in his experiments were thenceforth measured on the new system; and the numbers given in Joule's papers from 1840 downward are easily reducible to the modern absolute system of electric measurements, in the construction and general introduction of which he himself took so prominent a part. It was in 1840, also, that after experimenting on improvements in voltaic apparatus, he turned his attention to "the heat evolved by metallic conductors of electricity and in the cells of a battery during electrolysis." In this paper, and those following it in 1841 and 1842, he laid the foundation of a new province in physical science-electric and chemical thermodynamics-then totally unknown, but now wonderfully familiar, even to the roughest common sense practical electrician. With regard to the heat evolved by a metallic conductor carrying an electric current, he established what was already supposed to be the law, namely, that "the quantity of heat evolved by it [in a given time] is always proportional to the resistance which it presents, whatever may be the length, thickness, shape, or kind of the metallic conductor," while he obtained the law, then unknown, that the heat evolved is proportional to the "square" of the quantity of electricity passing in a given time. Corresponding laws were established for the heat evolved by the current passing in the electrolytic cell, and likewise for the heat developed in the cells of the battery itself.

In the year 1840 he was already speculating on the transformation of chemical energy into heat. In the paper last referred to and in a short abstract in the "Proceedings of the Royal Society", December, 1840, he points out that the heat generated in a wire conveying a current of electricity is a part of the heat of chemical combination of the materials used in the voltaic cell, and that the remainder, not the whole heat of combination, is evolved within the cell in which the chemical action takes place. In papers given in 1841 and 1842, he pushes his investigations further, and shows that the sum of the heat produced in all parts of the circuit during voltaic action is proportional to the chemical action that goes on in the voltaic pile, and again, that the quantities of heat which are evolved by the combustion of equivalents of bodies are proportional to the intensities of their affinities for oxygen. Having proceeded thus far, he carried on the same train of reasoning and experiment till he was able to announce in January, 1843, that the magneto-electric machine enables us to "convert mechanical power into heat". Most of his spare time in the early part of the year 1843 was devoted to making experiments necessary for the discovery of the laws of the development of heat by magneto-electricity, and for the definite determination of the mechanical value of heat.

At the meeting of the British Association at Cork, on August 21, 1843, he read his paper "On the Calorific Effects of Magneto-Electricity, and on the Mechanical Value of Heat." The paper gives an account of an admirable series of experiments, proving that "heat is generated" (not merely "transferred" from some source) by the magneto-electric machine. The investigation was pushed on for the purpose of finding whether a "constant ratio exists between the heat generated and the mechanical power" used in its production. As the result of one set of magneto-electric experiments, he finds 838 foot pounds to be the mechanical equivalent of the quantity of heat capable of increasing the temperature of one pound of water by one degree of Fahrenheit's scale. The paper is dated Broomhill, July, 1843, but a postscript, dated August, 1843, contains the following sentences:

"We shall be obliged to admit that Count Rumford was right in attributing the heat evolved by boring cannon to friction, and not (in any considerable degree) to any change in the capacity of the metal. I have lately proved experimentally that "heat is evolved by the passage of water through narrow tubes". My apparatus consisted of a piston perforated by a number of small holes, working in a cylindrical glass jar containing about 7 lb. of water. I thus obtained one degree of heat per pound of water from a mechanical force capable of raising about 770 lb. to the height of one foot, a result which will be allowed to be very strongly confirmatory of our previous deductions. I shall lose no time in repeating and extending these experiments, being satisfied that the grand agents of nature are, by the Creator's fiat, "indestructible", and that wherever mechanical force is expended, an exact equivalent of heat is "always" obtained."

This was the first determination of the dynamical equivalent of heat. Other naturalists and experimenters about the same time were attempting to compare the quantity of heat produced under certain circumstances with the quantity of work expended in producing it; and results and deductions (some of them very remarkable) were given by Séguin (1839), Mayer (1842), Colding (1843), founded partly on experiment, and partly on a kind of metaphysical reasoning. It was Joule, however, who first definitely proposed the problem of determining the relation between heat produced and work done in any mechanical action, and solved the problem directly.

It is not to be supposed that Joule's discovery and the results of his investigation met with immediate attention or with ready acquiescence. The problem occupied him almost continuously for many years; and in 1878 he gives in the "Philosophical Transactions" the results of a fresh determination, according to which the quantity of work required to be expended in order to raise the temperature of one pound of water weighed in vacuum from 60° to 61° Fahr., is 772.55 foot pounds of work at the sea level and in the latitude of Greenwich. His results of 1849 and 1878 agree in a striking manner with those obtained by Hirn and with those derived from an elaborate series of experiments carried out by Prof. Rowland, at the expense of the Government of the United States.

His experiments subsequent to 1843 on the dynamical equivalent of heat must be mentioned briefly. In that year his father removed from Pendlebury to Oak Field, Whalley Range, on the south side of Manchester, and built for his son a convenient laboratory near to the house. It was at this time that he felt the pressing need of accurate thermometers; and while Regnault was doing the same thing in France, Mr. Joule produced, with the assistance of Mr. Dancer, instrument maker, of Manchester, the first English thermometers possessing such accuracy as the mercury-in-glass thermometer is capable of. Some of them were forwarded to Prof. Graham and to Prof. Lyon Playfair; and the production of these instruments was in itself a most important contribution to scientific equipment.
As the direct experiment of friction of a fluid is dependent on no hypothesis, and appears to be wholly unexceptionable, it was used by Mr. Joule repeatedly in modified forms. The stirring of mercury, of oil, and of water with a paddle, which was turned by a falling weight, was compared, and solid friction, the friction of iron on iron under mercury, was tried; but the simple stirring of water seemed preferable to any, and was employed in all his later determinations.

In 1847 Mr. Joule was married to Amelia, daughter of Mr. John Grimes, Comptroller of Customs, Liverpool. His wife died early (1854), leaving him one son and one daughter.

The meeting of the British Association at Oxford, in this year, proved an interesting and important one. Here Joule read a fresh paper "On the Mechanical Equivalent of Heat." Of this meeting Sir William Thomson writes as follows to the author of this notice:

"I made Joule's acquaintance at the Oxford meeting, and it quickly ripened into a lifelong friendship.

"I heard his paper read in the section, and felt strongly impelled at first to rise and say that it must be wrong, because the true mechanical value of heat given, suppose in warm water, must, for small differences of temperature, be proportional to the square of its quantity. I knew from Carnot that this "must" be true (and it "is" true; only now I call it 'motivity,' to avoid clashing with Joule's 'mechanical value'). But as I listened on and on, I saw that (though Carnot had vitally important truth, not to be abandoned) Joule had certainly a great truth and a great discovery, and a most important measurement to bring forward. So, instead of rising, with my objection, to the meeting, I waited till it was over, and said my say to Joule himself, at the end of the meeting. This made my first introduction to him. After that I had a long talk over the whole matter at one of the "conversaziones" of the Association, and we became fast friends from thenceforward. However, he did not tell me he was to be married in a week or so; but about a fortnight later I was walking down from Chamounix to commence the tour of Mont Blanc, and whom should I meet walking up but Joule, with a long thermometer in his hand, and a carriage with a lady in it not far off. He told me he had been married since we had parted at Oxford! and he was going to try for elevation of temperature in waterfalls. We trysted to meet a few days later at Martigny, and look at the Cascade de Sallanches, to see if it might answer. We found it too much broken into spray. His young wife, as long as she lived, took complete interest in his scientific work, and both she and he showed me the greatest kindness during my visits to them in Manchester for our experiments on the thermal effects of fluid in motion, which we commenced a few years later"

"Joule's paper at the Oxford meeting made a great sensation. Faraday was there and was much struck with it, but did not enter fully into the new views. It was many years after that before any of the scientific chiefs began to give their adhesion. It was not long after, when Stokes told me he was inclined to be a Joulite."

"Miller, or Graham, or both, were for years quite incredulous as to Joule's results, because they all depended on fractions of a degree of temperature--sometimes very small fractions. His boldness in making such large conclusions from such very small observational effects is almost as noteworthy and admirable as his skill in extorting accuracy from them. I remember distinctly at the Royal Society, I think it was either Graham or Miller, saying simply he did not believe Joule, because he had nothing but hundredths of a degree to prove his case by."

The friendship formed between Joule and Thomson in 1847 grew rapidly. A voluminous correspondence was kept up between them, and several important researches were undertaken by the two friends in common. Their first joint research was on the thermal effects experienced by air rushing through small apertures The results of this investigation give for the first time an experimental basis for the hypothesis assumed without proof by Mayer as the foundation for an estimate of the numerical relation between quantities of heat and mechanical work, and they show that for permanent gases the hypothesis is very approximately true. Subsequently, Joule and Thomson undertook more comprehensive investigations on the thermal effects of fluids in motion, and on the heat acquired by bodies moving rapidly through the air. They found the heat generated by a body moving at one mile per second through the air sufficient to account for its ignition. The phenomena of "shooting stars" were explained by Mr. Joule in 1847 by the heat developed by bodies rushing into our atmosphere.

It is impossible within the limits to which this sketch is necessarily confined to speak in detail of the many researches undertaken by Mr. Joule on various physical subjects. Even of the most interesting of these a very brief notice must suffice for the present.

Molecular physics, as I have already remarked, early claimed his attention. Various papers on electrolysis of liquids, and on the constitution of gases, have been the result. A very interesting paper on "Heat and the Constitution of Elastic Fluids" was read before the Manchester Literary and Philosophical Society in 1848. In it he developed Daniel Bernoulli's explanation of air pressure by the impact of the molecules of the gas on the sides of the vessel which contains it, and from very simple considerations he calculated the average velocity of the particles requisite to produce ordinary atmospheric pressure at different temperatures. The average velocity of the particles of hydrogen at 32° F. he found to be 6,055 feet per second, the velocities at various temperatures being proportional to the square roots of the numbers which express those temperatures on the absolute thermodynamic scale.

His contribution to the theory of the velocity of sound in air was likewise of great importance, and is distinguished alike for the acuteness of his explanations of the existing causes of error in the work of previous experimenters, and for the accuracy, so far as was required for the purpose in hand, of his own experiments. His determination of the specific heat of air, pressure constant, and the specific heat of air, volume constant, furnished the data necessary for making Laplace's theoretical velocity agree with the velocity of sound experimentally determined. On the other hand, he was able to account for most puzzling discrepancies, which appeared in attempted direct determinations of the differences between the two specific heats by careful experimenters. He pointed out that in experiments in which air was allowed to rush violently or "explode" into a vacuum, there was a source of loss of energy that no one had taken account of, namely, in the sound produced by the explosion. Hence in the most careful experiments, where the vacuum was made as perfect as possible, and the explosion correspondingly the more violent, the results were actually the worst. With his explanations, the theory of the subject was rendered quite complete.

Space fails, or I should mention in detail Mr. Joule's experiments on magnetism and electro-magnets, referred to at the commencement of this sketch. He discovered the now celebrated change of dimensions produced by the magnetization of soft iron by the current. The peculiar noise which accompanies the magnetization of an iron bar by the current, sometimes called the "magnetic tick," was thus explained.

Mr. Joule's improvements in galvanometers have already been incidentally mentioned, and the construction by him of accurate thermometers has been referred to. It should never be forgotten that "he first" used small enough needles in tangent galvanometers to practically annul error from want of uniformity of the magnetic field. Of other improvements and additions to philosophical instruments may be mentioned a thermometer, unaffected by radiation, for measuring the temperature of the atmosphere, an improved barometer, a mercurial vacuum pump, one of the very first of the species which is now doing such valuable work, not only in scientific laboratories, but in the manufacture of incandescent electric lamps, and an apparatus for determining the earth's horizontal magnetic force in absolute measure.

Here this imperfect sketch must close. My limits are already passed. Mr. Joule has never been in any sense a public man; and, of those who know his name as that of the discoverer who has given the experimental basis for the grandest generalization in the whole of physical science, very few have ever seen his face. Of his private character this is scarcely the place to speak. Mr. Joule is still among us. May he long be spared to work for that cause to which he has given his life with heart-whole devotion that has never been excelled.

In June, 1878, he received a letter from the Earl of Beaconsfield announcing to him that Her Majesty the Queen had been pleased to grant him a pension of £200 per annum. This recognition of his labors by his country was a subject of much gratification to Mr. Joule.

Mr. Joule received the Gold Royal Medal of the Royal Society in 1852, the Copley Gold Medal of the Royal Society in 1870, and the Albert Medal of the Society of Arts from the hand of the Prince of Wales in 1880.

Source: Scientific American Supplement. Vol. XIV, No. 363

Monday, 26 July 2010

Arguments On Reincarnation


IF readers have erroneously thought the preceding arguments merely metaphysical, of no personal importance, they may now see that they lead to the most important issue possible for each one of us.

Reverting to Argument II. If thought, will, and feeling are part of the same source from which substance springs, and thus interconnected with substance, time, space, energy, then there is the possibility of consciousness being connected with substance and yet not necessarily dependent for continuity upon the maintenance of the physical form.

If consciousness is inherent in space, time, matter, energy, then there are as many grades of evolution in it as there are in matter. There must be electronic consciousness, atomic consciousness, energic consciousness, etheric consciousness; as well as the varied and comprehensive consciousness of organized beings, which must be compounds of the consciousnesses of all their component elements.

There is an organizing will and force in our involuntary processes; in the birth and growth of our bodies; in our so-called "subconscious mind" which has such powerful influence on our fates. These consciousnesses are part of our man-consciousness and yet partly separable from it, since they act largely without its knowledge.

These conscious organizing factors are not only necessary to maintain life, but organic evolution could not have taken place without them, as Prof. Seba Eldridge has shown. Eldridge shows that they have to be independent of the vital processes in order to regulate them; therefore, they must inhere in other forms of substance than those of which the organs are composed. They must be forms so far evolved that material means can know them only by their effects. And how about the ruling consciousness and will of man, which presides over all the organs, and can modify and direct their action?

The contradictory qualities ascribed to the "ether" indicate clearly the probability that instead of one "ether" as usually thought, science has to deal with a whole series of substances of a non-physical nature, lumped as yet under the one term. So taught the ancients, who approached the problem from the conscious side of things instead of the unconscious, unlike modern science.

If there be such a range of substances, each carrying its own shade or degree of consciousness, there is the possibility of the physical body being merely the visible aspect of a compound organism of vastly greater scope, not all parts of which need go to pieces with the visible part, any more than taking an organ from the body involves necessarily the death of the body.

There is an obvious difference in the quality and capacity of the consciousness of a rock, a plant, an animal, and a man. These differences must have come about by evolution, from the simple to the complex. Does such consciousness lie entirely in the visible substance of each of these forms, which go to pieces for good at death? Hardly, since in each living form the visible substance is drawn from lower forms, even from the mineral. If one claims that increasing complexity of organism creates a fuller consciousness, then a locomotive is more conscious than a rock, and a printing press more conscious than a locomotive.

This is the reductio ad absurdum, to which materialistic reasoning leads. Moreover, to control body and brain, often against their own impulses, involves a power superior to them. The simplest possible solution is the existence of a form or forms of highly evolved substance, interpenetrating and affecting the physical body, though invisible, as the magnetic field interpenetrates and affects iron. That is, a form coherent enough, old enough, to contain and carry past experience, and also able to act as a biological magnet to draw together and hold a new form from time to time through the processes of birth.

Is there any scientific obstacle to the idea of consciousness as existing within the limits of the body, but wedded to invisible forms of substance? Certainly not. Dr. Mathews shows this:

That we have aspirations and strivings for better things, for self-mastery, which are present in some degree in all human beings, is self evident. That is the kernel of the religion of every man in whatever philosophical system he may enshroud it. Do these aspirations spring from our atoms, or from something between them? Do they come from the ether which penetrates us and is, at times at least, gripped by our electrons, as it at other times grips them? Or since that ether flows through our electrons, are they inherent in the very atoms of which our bodies are made? Here is the whole question of the nature of man; the common puzzle for theologian and scientist; the common ground on which science and religion meet.
At the close of his volume he evidently leans toward the hypothesis of the invisible as containing greater possibilities.
... But the greater part of the volume of the body is the present, the uncreated, the immortal. It is part of the great universe; part of "I am."
Which of these two things are we: the gossamer, spider web of mortal; or the dense, unknown, immaterial, immortal ether which forms its background?

But whichever we are, we are part of the One, for the ether, the One, is streaming through our electrons either in time or space. While the distortion of these electrons may be but temporary and they be mortal, that essence of which they are made, the real essence, is the immortal. Perhaps this essence is the "élan vital" of Bergson; the driving force of evolution; the source of the unconquerable soul of man, and of its age and aeon-long struggle for freedom.

If evolution through reincarnation is not implied in this thought when logically carried out, what is?
The mental difference, therefore, between the different orders of life is due to the past nature and scope of the evolution of the respective controlling forms. In the mineral, for instance, such a form is hardly even incipient, its functioning confined solely to cohesion. Nothing but the preservation and transmission of acquired function and intelligence will explain the "ladder of life," with its closely-knit gradations of form and intelligence.

To science at the present date the forces behind evolution -- and we can give quote after quote -- are such an insoluble mystery that many have given up even discussing it. We have set forth above the true "missing link" without which no solution is possible.

The materialistically-inclined refuse to accept it -- as they say openly -- because it "would close the door to further knowledge." There is no logic in this -- the idea ought to be a stimulus instead of a discouragement. If there is a permanent form in man, it has been evolved under natural law and can become as much an object of study as anything else, if the proper means are found.

It happens that the ancients found that means.

COMPILER'S NOTE: The following is a separate item which followed the above article but was on the same page. I felt it was useful to include it here:

If the doctrine of Metempsychosis(1) had been properly understood in its application to the indestructibility of matter and the immortality of spirit, it would have been perceived that it is a sublime conception. If the Pythagorean metempsychosis should be thoroughly explained and compared with the modern theory of evolution, it would be found to supply every "missing link" in the chain of the latter.

Next article:
Arguments on Reincarnation
IV: Nature of Memory

COMPILER'S NOTE: I added this footnote; it was not in the article. If it doesn't paint an accurate enough picture, or is incorrect, I hope the Editors of THEOSOPHY magazine will spot it and point it out to me, so that I can make the necessary corrections.

(1) "Metempsychosis" is the progress of the soul from one stage of existence to another.
Back to text.

Thursday, 22 July 2010

The Benefits of Blue Blood

It fuels the journeys of shorebirds along the Eastern Seaboard and feeds some loggerhead sea turtles and sharks. The horseshoe crab is intricately woven into the web of life. Yet this harmless and primitive sea creature not only plays a key role in nature, it occupies a crucial place in the human world as well.

Over three decades ago, medicine claimed this ancient animal as a new life-saving tool. In 1971 researchers discovered that when they exposed the horseshoe crab to E. coli bacteria, the crab’s blood clotted. The clotting indicated the presence of endotoxins, toxic substances released by E. coli and other gram-negative bacteria that could produce severe symptoms in exposed humans such as fever or hemorrhagic stroke.

The simplicity of its immune system is actually what makes the crab’s blood useful to our biomedical industry. Horseshoe crabs live under the constant threat of infection in a habitat that can easily contain billions of bacteria per milliliter. To fight off infection, the horseshoe crab has a compound in its blood — LAL, or Limulus Amebocyte Lysate — which immediately binds and clots around fungi, viruses, and bacterial endotoxins.

LAL’s endotoxin binding and clotting ability is what makes it so invaluable to our own pharmaceutical industry. Once the LAL test was recognized by the Food and Drug Administration (FDA) as an alternative to then current methods of testing for endotoxins, the pharmaceutical industry tapped in. Horseshoe crabs were abundant, their blood easy to harvest and the test took only one hour.

Today, LAL has become the worldwide standard screening test for bacterial contamination. Every drug certified by the FDA must be tested using LAL, as do surgical implants such as pacemakers and prosthetic devices.

Horseshoe crab blood has not only become a key weapon in our medical arsenal, it has also become big business. On the world market, a quart of horseshoe crab blood has a price tag of an estimated $15,000, leading to overall revenues from the LAL industry estimated at U.S. $50 million per year. But that pales in comparison to its value to the pharmaceutical industry.

Of course, to obtain LAL you need horseshoe crabs — and lots of them. According to the Atlantic States Marine Fisheries Commission, that $50 million dollar industry requires the blood of approximately 250,000 horseshoe crabs.

While the blood of a horseshoe crab can be extracted without killing the animal, there is some question of how harmful bleeding is to the animals. The LAL industry says the bleeding causes no long-term injury.

Adult horseshoe crabs are collected by trawlers and transported to the LAL lab, where they are washed to remove sand and other marine debris from their exoskeletons. Those crabs without visible injuries are placed on a rack and bled with a large-gauge needle. Up to 30% of the crab’s blood is removed. Within 72 hours, the bled horseshoe crabs are returned to the water, where their blood volume rebounds in about a week.

LAL manufacturers have measured mortality rates of less then 3%. Yet two recent studies estimate that between 10% and 15% of crabs do not survive the bleeding procedure, which accounts for the mortality of 20,000 to 37,500 horseshoe crabs per year. Another concern is that it takes the crab a few months to rebuild its blood cell count level back up after a bleeding. Horseshoe crabs could be bled up to three or four times a year, which would take a toll on the health of the animals. But LAL manufacturers claim they only bleed them once a year.

Whether we can or will protect the health of horseshoe crabs for their own benefit, for the good of other creatures, or for our own use remains to be seen. Despite supporting the fishing industry for over 100 years, the condition of horseshoe crab populations has largely been ignored by fishery managers until recently. With growing concern over declining populations, regulations on the harvest of Horseshoe Crabs have just recently been imposed, though some states are already loosening restrictions.

Perhaps science can step in and “give back” to the animal for all of the good it has done us. Researchers are focusing their attention on producing LAL without the horseshoe crab, exploring the potential to cultivate and produce LAL from other sources.

Saturday, 17 July 2010

On Faraday's Lines of Force

The present state of electrical science seems peculiarly unfavourable to speculation. The laws of the distribution of electricity on the surface of conductors have been analytically deduced from experiment ; some parts of the mathematical theory of magnetism are established, while in other parts the experimental data are wanting ; the theory of the conduction of galvanism and that of the mutual attraction of conductors have been reduced to mathematical formulae, but have not fallen into relation with the other parts of the science. No electrical theory can now be put forth, unless it shews the connexion not only between electricity at rest and current electricity, but between the attractions and inductive effects of electricity in both states. Such a theory must accurately satisfy those laws, the mathematical form of which is known, and must afford the means of calculating the effects in the limiting cases where the known formulae are inapplicable. In order therefore to appreciate the requirements of the science, the student must make himself familiar with a considerable body of most intricate mathematics, the mere retention of which in the memory materially interferes with further progress. The first process therefore in the effectual study of the science, must be one of simplification and reduction of the results of previous investigation to a form in which the mind can grasp them. The results of this simplification may take the form of a purely mathematical formula or of a physical hypothesis. In the first case we entirely lose sight of the phenomena to be explained ; and though we may trace out the consequences of given laws, we can never obtain more extended views of the connexions of the subject. If, on the other hand, we adopt a physical hypothesis, we see the phenomena only through a medium, and are liable to that blindness to facts and rashness in assumption which a partial explanation encourages. We must therefore discover some method of investigation which allows the mind at every step to lay hold of a clear physical conception, without being committed to any theory founded on the physical science from which that conception is borrowed, so that it is neither drawn aside from the subject in pursuit of analytical subtleties, nor carried beyond the truth by a favourite hypothesis.

In order to obtain physical ideas without adopting a physical theory we must make ourselves familiar with the existence of physical analogies. By a physical analogy I mean that partial similarity between the laws of one science and those of another which makes each of them illustrate the other. Thus all the mathematical sciences are founded on relations between physical laws and laws of numbers, so that the aim of exact science is to reduce the problems of nature to the determination of quantities by operations with numbers. Passing from the most universal of all analogies to a very partial one, we find the same resemblance in mathematical form between two different phenomena giving rise to a physical theory of light.

The changes of direction which light undergoes in passing from one medium to another, are identical with the deviations of the patli of a particle in moving through a narrow space in which intense forces act. This analogy, which extends only to the direction, and not to the velocity of motion, was long believed to be the true explanation of the refraction of light ; and we still find it useful in the solution of certain problems, in which we employ it without danger, as an artificial method. The other analogy, between light and the vibrations of an elastic medium, extends much farther, but, though its importance and fruitfulness cannot be over-estimated, we must recollect that it is founded only on a resemblance in form between the laws of light and those of vibrations. By stripping it of its physical dress and reducing it to a theory of " transverse alternations," we might obtain a system of truth strictly founded on observation, but probably deficient both in the vividness of its conceptions and the fertility of its method. I have said thus much on the disputed questions of Optics, as a preparation for the discussion of the almost universally admitted theory of attraction at a distance.

We have all acquired the mathematical conception of these attractions. We can reason about them and determine their appropriate forms or formulae. These formulae have a distinct mathematical significance, and their results are found to be in accordance with natural phenomena. There is no formula in applied mathematics more consistent with nature than the formula of attractions, and no theory better established in the minds of men than that of the action of bodies on one another at a distance. The laws of the conduction of heat in uniform media appear at first sight among the most different in their physical relations from those relating to attractions. The quantities which enter into them are temperature, heat, conductivity. The word force is foreign to the subject. Yet we find that the mathematical laws of the uniform motion of heat in homogeneous media are identical in form with those of attractions varying inversely as the square of the distance. We have only to substitute source of heat for centre of attraction, flow of heat for accelerating effect of attraction at any point, and temperature for potential, and the solution of a problem in attractions is transformed into that of a problem in heat.

Now the conduction of heat is supposed to proceed by an action between contiguous parts of a medium, while the force of attraction is a relation between distant bodies, and yet, if we knew nothing more than is expressed in the mathematical formulae, there would be nothing to distinguish between the one set of phenomena and the other.

It is true, that if we introduce other considerations and observe additional facts, the two subjects will assume very different aspects, but the mathematical resemblance of some of their laws will remain, and may still be made useful in exciting appropriate mathematical ideas.

It is by the use of analogies of this kind that I have attempted to bring before the mind, in a convenient and manageable form, those mathematical ideas which are necessary to the study of the phenomena of electricity. The methods are generally those suggested by the processes of reasoning which are found in the researches of Faraday, and which, though they have been interpreted mathematically by Prof. Thomson and others, are very generally supposed to be of an indefinite and unmathematical character, when compared with those employed by the professed mathematicians. By the method which I adopt, I hope to render it evident that I am not attempting to establish any physical theory of a science in which I have hardly made a single experiment, and that the limit of my design is to shew how, by a strict application of the ideas and methods of Faraday, the connexion of the very different orders of phenomena which he has discovered may be clearly placed before the mathematical mind. I shall therefore avoid as much as I can the introduction of anything which does not serve as a direct illustration of Faraday's methods, or of the mathe matical deductions which may be made from them. In treating the simpler parts of the subject I shall use Faraday's mathematical methods as well as his ideas. When the complexity of the subject requires it, I shall use analytical notation, still confining myself to the development of ideas originated by the same philosopher.

I have in the first place to explain and illustrate the idea of " lines of force."

When a body is electrified in any manner, a small body charged with positive electricity, and placed in any given position, will experience a force urging it in a certain direction. If the small body be now negatively electrified, it will be urged by an equal force in a direction exactly opposite.

The same relations hold between a magnetic body and the north or south poles of a small magnet. If the north pole is urged in one direction, the south pole is urged in the opposite direction.

In this way we might find a line passing through any point of space, such that it represents the direction of the force acting on a positively electrified particle, or on an elementary north pole, and the reverse direction of the force on a negatively electrified particle or an elementary south pole. Since at every point of space such a direction may be found, if we commeilce at any point and draw a line so that, as we go along it, its direction at any point shall always coincide with that of the resultant force at that point, this curve will indicate the direction of that force for every point through which it passes, and might be called on that account a line of force. We might in the same way draw other lines of force, till we had filled all space with curves indicating by their direction that of the force at any assigned point.

We should thus obtain a geometrical model of the physical phenomena, which would tell us the direction of the force, but we should still require some method of indicating the intensity of the force at any point. If we consider these curves not as mere lines, but as fine tubes of variable section carrying an incompressible fluid, then, since the velocity of the fluid is inversely as the section of the tube, we may make the velocity vary according to any given law, by regulating the section of the tube, and in this way we might represent the intensity of the force as well as its direction by the motion of the fluid in these tubes. This method of representing the intensity of a force by the velocity of an imaginary fluid in a tube is applicable to any conceivable system of forces, but it is capable of great simplification in the case in which the forces are such as can be explained by the hypothesis of attractions varying inversely as the square of the distance, such as those observed in electrical and magnetic phenomena. In the case of a perfectly arbitrary system of forces, there will generally be interstices between the tubes; but in the case of electric and magnetic forces it is possible to arrange the tubes so as to leave no interstices. The tubes will then be mere surfaces, directing the motion of a fluid filling up the whole space. It has been usual to commence the investigation of the laws of these forces by at once assuming that the phenomena are due to attractive or repulsive forces acting between certain points. We may however obtain a different view of the subject, and one more suited to our more difficult inquiries, by adopting for the definition of the forces of which we treat, that they may be represented in magnitude and direction by the uniform motion of an incompressible fluid.

I propose, then, first to describe a method by which the motion of such a fluid can be clearly conceived ; secondly to trace the consequences of assuming certain conditions of motion, and to point out the application of the method to some of the less complicated phenomena of electricity, magnetism, and galvanism ; and lastly to shew how by an extension of these methods, and the introduction of another idea due to Faraday, the laws of the attractions and inductive actions of magnets and currents may be clearly conceived, without making any assump- tions as to the physical nature of electricity, or adding anything to that which has been already proved by experiment.

By referring everything to the purely geometrical idea of the motion of an imaginary fluid, I hope to attain generality and precision, and to avoid the dangers arising from a premature theory professing to explain the cause of the phenomena. If the results of mere speculation which I have collected are found to be of any use to experimental philosophers, in arranging and interpreting their results, they will have served their purpose, and a mature theory, in which physical facts will be physically explained, will be formed by those who by interrogating Nature herself can obtain the only true solution of the questions which the mathematical theory suggests.

~~James Clerk Maxwell

A new theory of Magnetic Fields

The tip of the iceberg

When man first discovered that a piece of loadstone hanging on a thread would always point in the same direction; when Oersted discovered that an electric current in wire affected a compass needle; when Faraday discovered that electricity can be generated by moving a magnet inside a wire coil; they perceived only the tip of the iceberg. The phenomena which we observe and have used to construct wonderful technologies are just the by products of the true nature of magnetism.

What I will show is that magnetism is as fundamental to the structure of matter as the electric force which binds the negative electrons to their positive nuclei. As we delve into the inner mechanisms of nature, magnetism becomes ever more significant. It is the regulator of processes. The phenomena we observe in the macro world are bye products of the inner workings of matter.

Without this insight, Oersted, Ampere, Faraday, Gauss, Biot, Savart and Michelson were working in the dark. The laws they developed are not fundamental laws of nature, but mathematical models designed to mimic the observed phenomena. As a result, they are not wholly self consistent and do not make complete sense. I remember sitting in a lecture trying to follow the mathematics. I am dyslexic and so was unable to take meaningful notes. The other students were writing everything down without understanding. I was more concerned with the way a term of seemed to come and go from equations. This was before the days of S.I. Units and there were four or five systems of units in operation. I plucked up courage and interrupted the lecture. It was easy with only 20 students in the cosy little physics department of Royal Holloway College.

"Excuse me Doctor F..... , but ......"

My memory is not good enough to recount the exact details, but it transpired under cross examination that the good doctor had compiled his notes from two text books. What he had not realised was that the two books were based on two different sets of units. In one set, an equation would need a term of , while in the other it would be absent. You will not be surprised by the good doctor's reply.

"I did that to keep you on your toes"

I tell this tale because it is symptomatic of the way in which knowledge is passed from one generation to the next. All too often, teachers do not understand what they are teaching. They have learnt it, not understood it. The students blindly copy down the notes and they in turn learn it without understanding.

Being dyslexic, I am a stranger to this process. It has taken me 40 years to acquire the technology and learn how to use it to overcome this disability. I could not record information in writing and recover it. My disability meant that any notes I made were not comprehensible to me. I never had the luxury of being able to learn. I had to understand. I have to understand. If I cannot understand something, I cannot capture it in my mind. If it has a structure which I can comprehend, its in for good.

In the enforced leisure of my early retirement, I have been revising my physics. I found that I could not understand the principles of electricity and magnetism. So I did what I should have done 30 years ago and worked out the theory for myself. Searching out and wrestling with the paradoxes, I hope I now comprehend the subject. In the film "The man went up a hill and came down a mountain" there are two Welsh farmers. Brothers, they are and know locally as Thomas Tupp and Thomas Tupp Too. The word tupp means "thick" or stupid, or educationally disadvantaged. One of the brothers introduces them.

"I'm Thomas Tupp and this is my brother Thomas Tupp Too.
"Folk say we are tupp, but we are not so tupp that we do not know that we are tupp."

And therein lies the dilemma of the scientific community. When people do not realise their own intellectual limits, they do not enter into the struggle to understand that which they have failed to comprehend. Learning is no substitute for understanding. It is in admitting a lack of understanding and in wrestling with the problem that the mistakes of the past are rectified. I came across a paper by TFG Searle, a colleague of JJ Thompson. He was looking at the magnetic field which should in theory surround a moving charge. This was just a few years after the discovery of the electron. JJ Thompson devoted a vast amount of energy to trying to explain the existence of matter in terms of vortices in the aether. Searle's paper tried to show that a moving spherical charge would posses the property of inertia. It does not manage to do that but ends in hope that he might be able to do so one day. A second paper on the subject nearly ten years latter is a load of rubbish.

This is the basic concept. A moving charge generates a magnetic field. Magnetic fields contain energy. To accelerate a charge, you must do work in order to create the magnetic field. So the charge resists being accelerated with a kind of inertial force. The concept is correct, but existing electromagnetic theory makes the task of calculating this impossible. The law of Biot-Savart tells us the magnetic field must be

When we accelerate the charge, increases. Magnetic flux moves outwards from the surface of the charge. Faraday's law says that this movement generates an electric field. This electric field can then act on the surface of the charge and produce a force. But there is a problem. When we try to calculate the number of lines of force which surround the charge, this is the integral of over a half plane extending to infinity from the line of motion of the charge, we get infinity. If Faraday is right, then nothing in the universe could move.

What I have done is to work out how magnetic flux must behave in order to overcome this paradox. It turns out that magnetism gives charges the property of inertia. We find that what we had called mass can be accounted for entirely in terms of energy in magnetic fields. The phenomena observed in the study of electricity and magnetism are but the tip of the iceberg.

Invisible fingers

When Oersted discovered that an electric current in wire affected a compass needle, he missed the point. The magnetic effect is a clue to something far more fundamental to our understanding. The pertinent question is "how is it that the movement of an electric current within a wire can generate an effect outside the wire". The accepted answer that it generates a magnetic field which flows out into the surrounding space is in a sense wrong. What is actually happening is that the electric fields which surround the individual electrons extend out into the surrounding space and move with their electrons. This gives the electric current the ability to generate a magnetic field beyond the wire.
When an electron and a proton form an atom of hydrogen, we find that we cannot measure an electric field of either from a distance. We have a theoretical method of measurement of an electric field by measuring the force on a small test charge. In practice this is impossible, but we can still perform a thought experiment. If we have one proton, it is surrounded by an electric field pointing outward. If we have one electron, it is surrounded by an electric field pointing inwards. When we put the two together, the result is that our test charge no longer shows any signs of experiencing a force. There are two possible reasons for this. Either the test charge experiences two equal and opposite forces, or it experiences no force. Either the two electric fields coexist in space, or they combine to eliminate each other. The accepted view is that they combine to eliminate each other.
The accepted view has its good points. It explains how the energy in the electric fields of the two charges in the atom is less than it would be if they were separate. Thus it provides a storage mechanism for the potential energy which must be given to the two charges in order to free the electron from the proton. But we might well ask if potential energy has to be physically stored. Might it be equally valid to say that potential energy exists by virtue of the geometry of the situation. What I would like to suggest is that the magnetic field generated in the region surrounding a current carrying wire is prima facie evidence for the fact the electric fields of individual charges coexist. They are like invisible fingers reaching out into space from every single charge. When the charge moves, the electric field moves with it. When an electric current flows in a wire, there is an imbalance in the random thermal velocities of the conduction band electrons. This is felt in the region beyond the wire in the relative movement of the coexisting electric fields of the conduction band electrons and of the other charges of the crystal lattice of the wire. It is this relative movement of the electric fields which generates the magnetic field.

The nature of magnetic flux

The relationship between moving charges and their magnetic fields can, I believe, be best understood in the following terms.
Electric fields in relative motion to each other have a property which is called magnetic intensity and is represented by the vector . Every moving charge, that is every charge because they are all moving all the time, has by virtue of the movement of its electric field an associated magnetic intensity field. This is a mathematical artefact of the movement of the electric field and has no real existence. The magnetic intensity at a point is the sum of the individual magnetic intensities of all the charges in the universe at that point and we can express this in the equation.

This sums up the combined effects of relative movements of electric fields and the effect of this combined relative movement is to encourage the formation of a magnetic field. We are accustomed to describe magnetic fields by their magnetic induction . We normally write the equation

but I would modify this to

where the sign is read "would like to be equal to".

The vector has been a convenient descriptor for magnetic fields being defined in terms of the ability of the field to exert a force on a moving conductor. However it has served more than anything else as a device for enabling us to avoid wrestling with trying to understand the nature of magnetic flux.

Magnetic flux is first and foremost a form of energy. It is an energy density flux. It cannot be created or destroyed except that at the surface of a charge, it may be generated or adsorbed changing to and from mechanical energy strictly in accordance with the law of conservation of energy. It is subject to the very severe limitation that it can only move into and out of charges parallel to their electric fields. It has directional properties. These properties are best described by the scalar and vector forms of the magnetic energy density.

We as humans are right at the limits of our ability when we try to comprehend the nature of magnetic flux. It is no surprise that we need to periodically rethink our concept of it. We kneed a stating point and so I am going to use an analogy.

The two properties of magnetic flux; energy density and magnetic induction have the same relationship to one another as do the tilth and the furrows of a field. That is a perfect analogy for anyone with a rural background, but may need a little explaining to others. You start with a plain uncultivated field. Below the grass is soil. You plough the field to create a layer of tilth in which to plant the crop. The plough leaves a geometric pattern of ridges running the length of the field which are called furrows. This tilled soil or tilth as it is called is both created by the ploughing and is the substance from which the pattern of the furrows is made.

When we consider a magnetic field, we need to be aware that it has these two properties of tilth and furrows. The tilth is the energy content of the magnetic field and the energy density might be thought of as the depth of tilth. The furrows are the magnetic induction which we characterise by drawing lines of force. The formation and behaviour of the magnetic field is governed by the properties of both tilth and furrow. At any instance, the lines of force must form continuous loops.

The process by which magnetic energy density flux adds and subtracts is most peculiar and can only be understood in terms of the directional properties of the magnetic field. This is rather technically demanding and is discussed in all its mathematical detail within the section on accelerating a charge.

The observed form of magnetic fields depends entirely on the scale upon which we observe them. From close up, all we see is the individual magnetic fields which surround each charge. The intensity of these fields is many orders of magnitude more than that of any magnetic field we might create in a laboratory or in an electric motor. This field forms circular loops about the line of motion of the charge. At this scale we can use the term "field of motion" to describe the magnetic field surrounding the charge. As we move away from an individual charge, the strength its magnetic field falls off until we find it merging into and combining with the fields of other charges. Eventually we reach human scales and see magnetic fields as revealed by iron filing patterns. But to gain an understanding of the nature of magnetism, we need to consider a simple moving charge. Put aside your concept of an electron and consider a fictional entity which I call a pure charge. It has no mass, no angular momentum and no intrinsic magnetic moment. It is simply a hollow spherical surface of charge.

Imagine we find our charge moving some distance away from any other charge. Nevertheless, the region it is moving through is permeated by the presence of the electric fields of a universe full of charge. It is against this background presence that we measure the velocity of our charge, because it is its relative motion to that background presence which generates its magnetic field. We will consider simple changes in the motion of the charge. First let us accelerate the charge in the direction it is moving. We are increasing the magnetic field and its energy content increases. The magnetic energy density is becoming greater. This means that magnetic energy flux has to be created at the surface of the charge and move outwards. If we calculate the rate of increase of energy in the field of motion of the charge, we can then use the idea that there must be a continuity of presence and movement of the magnetic energy density flux, to calculate the speed with which energy density flux is emerging from the surface of the charge. At this level, we can apply Faraday's law using the velocity with which the energy density flux is moving from the surface. We get the correct answer. That is to say that the force we get is the force required to do the mechanical work to increase the energy content of the field of motion of the charge.

Newton's laws

The mathematical analysis can be done for an acceleration in any direction. We find that acceleration is always resisted by a force which is proportional to the acceleration. The other two factors governing the magnitude of the force is the magnitude of the charge and its radius.

The first important result of the proof is that the property we call inertia exists for a pure charge and can be wholly accounted as an electromagnetic interaction.

The second is that starting from a modified understanding of the nature of magnetic flux, we have taken the laws of Biot-Savart and Faraday and proved that Newtons second law of motion, , applies to a pure charge. With this, the laws of mechanics can be deduced.

Faraday's law revisited

It is hard for us imagine how difficult Faraday's original experiment must have been for we are familiar with sensitive moving coil galvanometers. These however did not exist. The galvanometers of the day relied on electrostatic forces and were very insensitive. The famous experiment of Faraday in which a magnet is moved into and out of a coil producing a voltage in the coil has a sequel in which the coil is moved over the magnet and then removed. These two experiments led Faraday to conclude that it was the relative motion between the magnet and the coil which generated the voltage. This concept of relative motion is fundamental to the accepted theory, but it hides from us the real process.

I want to look at the situation where the magnet is moving. In the absence of any coil, we are quite happy to calculate that the moving magnetic field generates an electric field. This is consistent with the theory of the propagation of electromagnetic radiation discovered by Maxwell. The electric field results in an electric polarisation of space. That results in a displacement current flowing which in turn generates a magnetic field which in turn..... And the result is a travelling electromagnetic wave. What is not quite so obvious is the fact that if we place a test charge in the way, it will feel the electric field induced by the motion of the magnetic field pulling in one direction while it finds that the polarisation of space pulls it in the opposite direction with an equal force. So the movement of the magnet should have no effect, but it does.

The answer is far more subtle. The electric field of a charge extends throughout all space falling off in intensity according to the inverse square law. As it moves, the effect of its motion is felt everywhere because of its contribution to the magnetic intensity. We have defined magnetic intensity as and we know that the magnetic energy density is given by . We also know that . When we substitute these equations into each other, we get a most interesting result.

The significance of this result is that the magnetic energy density at a point in a magnetic field is equal to the sum of the energy densities of the individual fields of the individual charges. These contributions can be positive or negative depending on whether the motion of the individual charge is contributing to the magnetic field or lessening it at that point. Now magnetic energy density flux can only move within the confines of the electric fields of charges. If we assume that each charge has its own personal energy density field which is influenced by the prevailing magnetic induction, we find that variations in the magnetic field around a charge will cause magnetic energy density flux to move into and out of the surface of the charge as its position relative to magnetic fields changes.

Let us try to imagine a very well defined situation in which a region of strong magnetic field moves towards the charge. So long as the charge remains outside this region of magnetic field, the energy content of the magnetic energy density flux belonging to the charge remains fairly constant. As soon as the charge moves into the region, there is dramatic change because the energy content now depends on the distance of the charge from the boundary of the region. The charge is moving away from one boundary towards the other and that means that magnetic energy density flux is flowing out of the charge on one side and into it on the other. It is this process which generates the force on the charge. Now the effect on the charge is opposite to the effect of the charge on the field. That means that if the motion of the charge relative to the field is such as to have no effect on the field, then the field has no effect on the charge. The more the motion of the charge affects the field, the greater the force on the charge.

A charge does not have to be within a magnetic field to be affected by it when the field is varying in size and/or strength and/or orientation. The transformer relies very much on this principle. Conventional wisdom has it that magnetic flux moves outwards from the turns of the primary coil into the core as magnetic field builds, then moves back into the turns as the field collapses. In this process, it is said to cut all the turns of wire both of the primary and of the primary coils. This in fact does not happen! There are two factors which contradict this picture. The first can be seen if we imagine a loosely wound coil and draw lines of force for increasing currents. What we find in our two dimensional picture of the expanding magnetic field is that there are zero points between the turns of the coil. The lines of force cannot pass these points. What happens is that lines of force moving towards these points thin and appear to part to join with other lines on the far side of the point. The result of this is that local to each wire, we only find magnetic flux moving outward from the wire. We do not see the flux of the whole field cutting the individual turns as the field changes. The second thing is that within the magnetic core, the process of magnetisation and demagnetization is accomplished by movement of the boundaries of the individual magnetic domains of the material. This involves individual electron orbits changing orientation so that their flux links with neighbours on one side rather than on the other. If we were to attempt to draw diagrams of the movement of the lines of force during this process, we would again find the movements to be local. The mass movement of magnetic flux just does not happen in the way the theory imagines. There has to be a second mechanism which accounts for the induced emf in the coils. It is the process I have described in the previous paragraph.

What the reader needs to understand is that analysis of the workings of a transformer are based on a model which is consistent with energy conservation. It is this consistency which enables the theory to supply answers which are the same as the observed behaviour of the components. The actual mechanism which I have described is also consistent with the conservation of energy and so accounts for the match between theory and practice.

The intimate connection

The process which I have described above becomes more important as we reduce the scale on which we look at a group of charges. Let us imagine that we have a stream of moving charges forming an electric current. The combined effect of the individual movements of the electrons forms the electric current and this generates a magnetic field. We might think of a long thin wire as carrying the current and we find that the surrounding magnetic field has a given energy content per unit length of the wire. If we now stop one electron dead in its tracks, we find that it resists being stopped exerting a force and transferring energy to whatever stopped it. Now the energy which the electron transfers comes from two sources. There is the energy stored in the magnetic field surrounding the electron and we can think of this as the kinetic energy of the electron. Then there is the energy which the electron contributed to the magnetic field which the current generates. But the removal of one electron from the group would mean that the the current is reduced and the surrounding magnetic field needs to shrink. This loss of energy from the magnetic field results in equal amounts of energy have to be transferred to each electron of the current. This flow of energy into the surfaces of the individual charges results in the generation of a force tending to accelerate each electron in the direction of the current. I call this the intimate connection because it links the motion of all of the electrons which constitute the current. A collision which decelerates on electron accelerates all the other electrons. This is the essence of the effect which we call self inductance.

If we come down to the scale of an atom, we find that this process continues. The motion of the electrons is totally chaotic, but basically takes the electrons along sections of curved paths. I call this process pseudo orbiting. The process of moving in an arc should be accompanied by the field of motion of the electron rotating with it, but this process is limited because the further we are from the magnetic field, the faster the magnetic field would have to move. We reach a region where the magnetic energy density flux is literally left behind. If we had a single electron orbiting a nucleus, then the result would be the establishment of a stable orbital magnetic field. Let us imagine that we had one electron orbiting a helium nucleus so that we can imagine a second electron being captured by it. We now have an extremely complex situation in which the resulting orbital magnetic field is composed of energy from both electrons. The electrons interact producing chaotic pseudo orbiting and all the time, magnetic energy density flux is moving into and out of their surfaces generating forces on them. If the change in motion of the electrons is such as to increase their common magnetic field, then the forces on each electron as the magnetic field attempts to grow will tend to lessen the growth in the field, but then if their change of motion is such as to decrease their common magnetic field, the forces generated by the movement of magnetic energy density flux into and out of their surfaces will oppose this tendency. What we can say is that fluctuations in the magnetic fields within and around the atom provides a mechanism for energy exchange between the electrons which has an additional effect on their motion.

What we will find when we attempt to model this and to try to understand the chaotic behaviour of electrons within an atom is only to be guessed at. Will we be able to account for the atomic spectra. Is it possible that some brilliant mathematician will produce phase space models of the chaotic behaviour identical to the present probability distributions of quantum mechanics? One thing is certain: there is more to magnetism than we ever imagined.

© Copyright Bruce Harvey 1997.