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James Clerk Maxwell

Data de nascimento: 13. Junho 1831
Data de falecimento: 5. Novembro 1879

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James Clerk Maxwell foi um físico e matemático escocês. É mais conhecido por ter dado forma final à teoria moderna do eletromagnetismo, que une a eletricidade, o magnetismo e a óptica. Esta é a teoria que surge das equações de Maxwell, assim chamadas em sua honra e porque foi o primeiro a escrevê-las juntando a lei de Ampère, modificada por Maxwell, a lei de Gauss, e a lei da indução de Faraday. Maxwell demonstrou que os campos elétricos e magnéticos se propagam com a velocidade da luz. Ele apresentou uma teoria detalhada da luz como um efeito electromagnético, isto é, que a luz corresponde à propagação de ondas eléctricas e magnéticas, hipótese que tinha sido posta por Faraday. Foi demonstrado em 1864 que as forças elétricas e magnéticas têm a mesma natureza: uma força elétrica em determinado referencial pode tornar-se magnética se analisada noutro, e vice-versa. Ele também desenvolveu um trabalho importante em mecânica estatística, estudou a teoria cinética dos gases e descobriu a distribuição de Maxwell-Boltzmann. Seu trabalho em eletromagnetismo foi a base da relatividade restrita de Einstein e o seu trabalho em teoria cinética de gases fundamental ao desenvolvimento posterior da mecânica quântica.

Citações James Clerk Maxwell

„Words from empty words they sever—
Words of Truth from words of Pride.“

— James Clerk Maxwell
Context: By the hollow mauntain-side Questions strange I shout for ever, While echoes far and wide Seem to mock my vain endeavour; Still I shout, for though they never Cast my borrowed voice aside, Words from empty words they sever— Words of Truth from words of Pride. Part III Poems, "Reflection from Various Surfaces" (April 18, 1853)

„But we have no right to think thus of the unsearchable riches of creation, or of the untried fertility of those fresh minds into which these riches will continue to be poured.“

— James Clerk Maxwell
Context: This characteristic of modern experiments — that they consist principally of measurements — is so prominent, that the opinion seems to have got abroad, that in a few years all the great physical constants will have been approximately estimated, and that the only occupation which will then be left to men of science will be to carry on these measurements to another place of decimals. If this is really the state of things to which we are approaching, our Laboratory may perhaps become celebrated as a place of conscientious labour and consummate skill, but it will be out of place in the University, and ought rather to be classed with the other great workshops of our country, where equal ability is directed to more useful ends. But we have no right to think thus of the unsearchable riches of creation, or of the untried fertility of those fresh minds into which these riches will continue to be poured. It may possibly be true that, in some of those fields of discovery which lie open to such rough observations as can be made without artificial methods, the great explorers of former times have appropriated most of what is valuable, and that the gleanings which remain are sought after, rather for their abstruseness, than for their intrinsic worth. But the history of science shews that even during the phase of her progress in which she devotes herself to improving the accuracy of the numerical measurement of quantities with which she has long been familiar, she is preparing the materials for the subjugation of the new regions, which would have remained unknown if she had been contented with the rough methods of her early pioneers. I might bring forward instances gathered from every branch of science, shewing how the labour of careful measurement has been rewarded by the discovery of new fields of research, and by the development of new scientific ideas. But the history of the science of terrestrial magnetism affords us a sufficient example of what may be done by experiments in concert, such as we hope some day to perform in our Laboratory. Introductory Lecture on Experimental Physics held at Cambridge in October 1871, re-edited by W. D. Niven (2003) in Volume 2 of The Scientific Papers of James Clerk Maxwell, Courier Dover Publications, p. 241; this has sometimes been misquoted in a way which considerably alters its intent: "in a few years, all the great physical constants will have been approximately estimated, and … the only occupation which will then be left to the men of science will be to carry these measurement to another place of decimals."

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„Colour as perceived by us is a function of three independent variables“

— James Clerk Maxwell
Context: Colour as perceived by us is a function of three independent variables at least three are I think sufficient, but time will show if I thrive. Maxwell, in a letter to William Thomson, The Scientific Letters and Papers of James Clerk Maxwell: 1846-1862 (1990), p. 245.

„I hope that you will not tell me you have little fault to find with me, without finding that little and communicating it.“

— James Clerk Maxwell
Context: I maintain that all the evil influences that I can trace have been internal and not external, you know what I mean—that I have the capacity of being more wicked than any example that man could set me, and that if I escape, it is only by God's grace helping me to get rid of myself, partially in science, more completely in society, — but not perfectly except by committing myself to God as the instrument of His will, not doubtfully, but in the certain hope that that Will will be plain enough at the proper time. Nevertheless, you see things from the outside directly, and I only by reflexion, so I hope that you will not tell me you have little fault to find with me, without finding that little and communicating it. Letter to Rev. C. B. Tayler ( 8 July 1853) in Ch. 6 : Undergraduate Life At Cambridge October 1850 to January 1854 — ÆT. 19-22, p. 189

„But listen, what harmony holy
Is mingling its notes with our own!
The discord is vanishing slowly,
And melts in that dominant tone.
And they that have heard it can never
Return to confusion again,
Their voices are music for ever,
And join in the mystical strain.“

— James Clerk Maxwell
Context: But listen, what harmony holy Is mingling its notes with our own! The discord is vanishing slowly, And melts in that dominant tone. And they that have heard it can never Return to confusion again, Their voices are music for ever, And join in the mystical strain. Part III Poems, To the Air of "Lörelei." (January, 1858)

„This velocity is so nearly that of light, that it seems we have strong reason to conclude that light itself“

— James Clerk Maxwell
Context: The general equations are next applied to the case of a magnetic disturbance propagated through a non-conductive field, and it is shown that the only disturbances which can be so propagated are those which are transverse to the direction of propagation, and that the velocity of propagation is the velocity v, found from experiments such as those of Weber, which expresses the number of electrostatic units of electricity which are contained in one electromagnetic unit. This velocity is so nearly that of light, that it seems we have strong reason to conclude that light itself (including radiant heat, and other radiations if any) is an electromagnetic disturbance in the form of waves propagated through the electromagnetic field according to electromagnetic laws. A Dynamical Theory of the Electromagnetic Field (1864), §20.

„I mean—that I have the capacity of being more wicked than any example that man could set me, and that if I escape, it is only by God's grace“

— James Clerk Maxwell
Context: I maintain that all the evil influences that I can trace have been internal and not external, you know what I mean—that I have the capacity of being more wicked than any example that man could set me, and that if I escape, it is only by God's grace helping me to get rid of myself, partially in science, more completely in society, — but not perfectly except by committing myself to God as the instrument of His will, not doubtfully, but in the certain hope that that Will will be plain enough at the proper time. Nevertheless, you see things from the outside directly, and I only by reflexion, so I hope that you will not tell me you have little fault to find with me, without finding that little and communicating it. Letter to Rev. C. B. Tayler ( 8 July 1853) in Ch. 6 : Undergraduate Life At Cambridge October 1850 to January 1854 — ÆT. 19-22, p. 189

„It is of great advantage to the student of any subject to read the original memoirs on that subject, for science is always most completely assimilated when it is in the nascent state“

— James Clerk Maxwell
Context: It is of great advantage to the student of any subject to read the original memoirs on that subject, for science is always most completely assimilated when it is in the nascent state... A Treatise on Electricity and Magnetism (1873), Preface, p. xiii.

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„Happiness and Misery must inevitably increase with increasing Power and Knowledge“

— James Clerk Maxwell
Context: I believe, with the Westminster Divines and their predecessors ad Infinitum that "Man's chief end is to glorify God and to enjoy him for ever." That for this end to every man has been given a progressively increasing power of communication with other creatures. That with his powers his susceptibilities increase. That happiness is indissolubly connected with the full exercise of these powers in their intended direction. That Happiness and Misery must inevitably increase with increasing Power and Knowledge. That the translation from the one course to the other is essentially miraculous, while the progress is natural. But the subject is too high. I will not, however, stop short, but proceed to Intellectual Pursuits. Letter to Lewis Campbell (9 November 1851) in Ch. 6 : Undergraduate Life At Cambridge October 1850 to January 1854 — ÆT. 19-22, p. 158

„In every branch of knowledge the progress is proportional to the amount of facts on which to build“

— James Clerk Maxwell
Context: In every branch of knowledge the progress is proportional to the amount of facts on which to build, and therefore to the facility of obtaining data. Letter to Lewis Campbell (9 November 1851) in Ch. 6 : Undergraduate Life At Cambridge October 1850 to January 1854 — ÆT. 19-22, p. 159

„We may find illustrations of the highest doctrines of science in games and gymnastics, in travelling by land and by water, in storms of the air and of the sea, and wherever there is matter in motion.“

— James Clerk Maxwell
Introductory Lecture on Experimental Physics held at Cambridge in October 1871, re-edited by W. D. Niven (2003) in Volume 2 of The Scientific Papers of James Clerk Maxwell, Courier Dover Publications, p. 243.

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„I have also cleared the electromagnetic theory of light from all unwarrantable assumption, so that we may safely determine the velocity of light by measuring the attraction between bodies kept at a given difference of potential, the value of which is known in electromagnetic measure.“

— James Clerk Maxwell
Letter to C. Hockin, Esq. (Sept 7, 1864) as quoted by Lewis Campbell, William Garnett, [https://books.google.com/books?id=B7gEAAAAYAAJ The Life of James Clerk Maxwell: With Selections from His Correspondence and Occasional Writings] (1884)

„The equations at which we arrive must be such that a person of any nation, by substituting the numerical values of the quantities as measured by his own national units, would obtain a true result.“

— James Clerk Maxwell
Encyclopedia Brittanica article, quoted by Patricia Fara in Science A Four Thousand Year History (2009) citing Simon Schaffer article in The Values of Precision (1995) ed. M. Norton Wise

„Mathematicians may flatter themselves that they possess new ideas which mere human language is yet unable to express. Let them make the effort to express these ideas in appropriate words without the aid of symbols, and if they succeed they will not only lay us laymen under a lasting obligation, but we venture to say, they will find themselves very much enlightened during the process, and will even be doubtful whether the ideas as expressed in symbols had ever quite found their way out of the equations of their minds.“

— James Clerk Maxwell
"Thomson & Tait's Natural Philosophy" in Nature, Vol. 7 (Mar. 27, 1873) A review of ' [https://archive.org/details/elementsnatural00kelvgoog] (1873) by Sir W. Thomson, P. G. Tait. See [https://archive.org/details/nature7818721873lock Nature, Vol. 7-8,] Nov. 1872-Oct. 1873, pp. 399-400, or The Scientific Papers of James Clerk Maxwell, [https://books.google.com/books?id=lzlRAAAAYAAJ&pg=PA328 p. 328.]<!--Commented out this source: A Dynamical Theory of the Electromagnetic Field, Introduction.[https://books.google.com/books?id=p1pKAwAAQBAJ&pg=PA5&lpg=PA5&dq=Mathematicians+may+flatter]-->

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