Frasi di William Herschel (39 frasi) | Citazioni e frasi celebri

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William Herschel frasi celebri

“Non puoi aspettarti di vedere al primo sguardo. Osservare è per certi versi un'arte che bisogna apprendere. citazione necessaria”

William Herschel

“Ho osservato stelle la cui luce, come si può dimostrare, deve impiegare 2 milioni di anni per raggiungere la Terra.”

William Herschel

citato in AA.VV., Il libro dell'astronomia, traduzione di Roberto Sorgo, Gribaudo, 2017, p. 89. ISBN 9788858018347

“Assomigliano a piccole stelle al punto che è difficile distinguerli da queste ultime. Da ciò, dal loro aspetto asteroidale, ne trarrei il nome, chiamandoli asteroidi.”

William Herschel

citato in AA.VV., Il libro dell'astronomia, traduzione di Roberto Sorgo, Gribaudo, 2017, p. 99. ISBN 9788858018347

William Herschel: Frasi in inglese

“I have made it a rule never to employ a larger telescope when a smaller will answer the purpose.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works".

“I have availed myself of the labors of preceding astronomers, but have been induced thereto by my own actual observation of the solar phenomena.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" quote from his paper "Nature and Construction of the Sun and Fixed Stars" (1795).
Contesto: I should not wonder if, considering all this, we were induced to think that nothing remained to be added; and yet we are still very ignorant in regard to the internal construction of the sun.... The spots have been supposed to be solid bodies, the smoke of volcanoes, the scum floating on an ocean of fluid matter, clouds, opaque masses, and to be many other things.... The sun itself has been called a globe of fire, though, perhaps, metaphorically.... It is time now to profit by the observations we are in possession of. I have availed myself of the labors of preceding astronomers, but have been induced thereto by my own actual observation of the solar phenomena.<!-- p. 145-146

“That the emission of light must waste the sun, is not a difficulty that can be opposed to our hypothesis.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" quote from his paper "Nature and Construction of the Sun and Fixed Stars" (1795).
Contesto: That the emission of light must waste the sun, is not a difficulty that can be opposed to our hypothesis. Many of the operations of Nature are carried on in her great laboratory which we cannot comprehend. Perhaps the many telescopic comets may restore to the sun what is lost by the emission of light.<!-- p. 148

“Nebulæ can be selected so that an insensible gradation shall take place”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works"
Contesto: Nebulæ can be selected so that an insensible gradation shall take place from a coarse cluster like the Pleiades down to a milky nebulosity like that in Orion, every intermediate step being represented. This tends to confirm the hypothesis that all are composed of stars more or less remote.

“A knowledge of the construction of the heavens has always been the ultimate object of my observations…”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811)

“It is evident that we cannot mean to affirm that the stars of the fifth, sixth, and seventh magnitudes are really smaller than those of the first, second, or third, and that we must ascribe the cause of the difference in the apparent magnitudes of the stars to a difference in their relative distances from us.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" from a memoir, published (1817).
Contesto: It is evident that we cannot mean to affirm that the stars of the fifth, sixth, and seventh magnitudes are really smaller than those of the first, second, or third, and that we must ascribe the cause of the difference in the apparent magnitudes of the stars to a difference in their relative distances from us. On account of the great number of stars in each class, we must also allow that the stars of each succeeding magnitude, beginning with the first, are, one with another, further from us than those of the magnitude immediately preceding.

“The starlike appearance of the following six nebulæ is so considerable that the best description… was to compare them to stars with certain deficiencies.”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811)
Contesto: The starlike appearance of the following six nebulæ is so considerable that the best description... was to compare them to stars with certain deficiencies.<!-- p. 328

“In future… we shall look upon those regions into which we may now penetrate by means of such large telescopes, as a naturalist regards a rich extent of ground or chain of mountains containing strata variously inclined and directed, as well as consisting of very different materials. The surface of a globe or map therefore will but ill delineate the interior parts of the heavens.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" from a memoir (1784).

“It will be necessary to explain the spirit of the method of arranging the observed astronomical objects under consideration in such a manner, that one shall assist us to understand the nature and construction of the other.”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811)
Contesto: It will be necessary to explain the spirit of the method of arranging the observed astronomical objects under consideration in such a manner, that one shall assist us to understand the nature and construction of the other. This end I propose to obtain by assorting them into as many classes as will be required to produce the most gradual affinity... and it will be found that those contained in one article, are so closely allied to those in the next, that there is perhaps not so much difference between them... as there would be in an annual description of the human figure were it given from the birth of a child till he comes to be a man in his prime.<!-- p. 270-271

“An object may not only contain stars, but also nebulosity not composed of them.”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811), p. 270

“This tends to confirm the hypothesis that all are composed of stars more or less remote.”

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William Herschel

“It is very probable that the great stratum called the Milky Way is that in which the sun is placed, though perhaps not in the very centre of its thickness.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works".
Contesto: It is very probable that the great stratum called the Milky Way is that in which the sun is placed, though perhaps not in the very centre of its thickness.... We gather this from the appearance of the Galaxy, which seems to encompass the whole heavens, as it certainly must do if the sun is within it.<!-- p. 159-160

“We may conceive that, perhaps in progress of time these nebulæ which are already in such a state of compression, may be still farther condensed so as actually to become stars.”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811), p. 318

“An equal scattering of the stars may be admitted in certain calculations; but when we examine the milky way, or the closely compressed clusters of stars… this supposed equality of scattering must be given up.”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“A standard of reference for the arrangement of the stars may be had by comparing their distribution to a certain properly modified equality of scattering. The equality which I propose does not require that the stars should be at equal distances from each other, nor is it necessary that all those of the same nominal magnitude should be equally distant from us.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" from a memoir, published (1817).

“The number of compound nebulæ… being so considerable, it will follow, that if they owe their origin to the breaking up of some former extensive nebulosities of the same nature with those which have been shewn to exist at present, we might expect that the number of separate nebulæ should far exceed the former, and that moreover these scattered nebulas should be found not only in great abundance, but also in proximity or continuity with each other… Now this is exactly what by observation, we find to be the state of the heavens.”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“When I resided at Bath I had long been acquainted with the theory of optics and mechanics, and wanted only that experience so necessary in the practical part of these sciences. This I acquired by degrees at that place where in my leisure hours, by way of amusement, I made several two-foot, five-foot, seven-foot, ten-foot and twenty-foot Newtonian telescopes, beside others, of the Gregorian form, of eight, twelve, and eighteen inches, and two, three, five, and ten feet focal length. In this way I made not less than two hundred seven-foot, one hundred and fifty ten-foot, and about eighty twenty-foot mirrors, not to mention the Gregorian telescopes.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" Footnote: At least one of these telescopes had the principal mirror made of glass instead of metal. Philosophical Transactions of the Royal Society of London (1803).

“To conclude, if we call light, those rays which illuminate objects, and radiant heat, those which heat bodies, it may be inquired whether light be essentially different from radiant heat? In answer to which I would suggest that we are not allowed, by the rules of philosophizing, to admit two different causes to explain certain effects, if they may be accounted for by one. …If this be a true account of the solar heat, for the support of which I appeal to my experiments, it remains only for us to admit that such of the rays of the sun as have the refrangibility of those which are contained in the prismatic spectrum, by the construction of the organs of sight, are admitted under the appearance of light and colors, and that the rest, being stopped in the coats and humors of the eye, act on them, as they are known to do on all the other parts of our body, by occasioning a sensation of heat.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" on his discovery of the infrared light.

“I compared it to H Geminorum and the small star in the quartile between Auriga and Gemini, and finding it so much larger than either of them, suspected it to be a comet.”

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William Herschel

His discovery of Uranus. Scientific Papers, vol. 1, page 30 "Account of a Comet".

“A nebulous matter, diffused in such exuberance throughout the regions of space, must surely draw our attention to the purpose for which it probably may exist; and it must be the business of a critical inquirer to attend to all the appearances under which it will be exposed to his view…”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“In consequence of this arrangement I began to construct the forty-foot telescope about the latter end of 1785. The woodwork of the stand and machines for giving the required motions to the instrument were immediately put in hand. In the whole of the apparatus none but common workmen were employed, for I made drawings of every part of it, by which it was easy to execute the work, as I constantly inspected and directed every person's labor; though sometimes there were not less than forty different workmen employed at the same time. While the stand of the telescope was preparing, I also began the construction of the great mirror, of which I inspected the casting, grinding, and polishing, and the work was in this manner carried on with no other interruption than that occasioned by the removal of all the apparatus and materials from where I then lived, to my present situation at Slough.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works"

“This consideration must alter the form of our proposed inquiry; for the question being thus at least partly decided, since it is ascertained that we have rays of heat which give no light, it can only become a subject of inquiry whether some of these heat-making rays may not have a power of rendering objects visible, superadded to their now already established power of heating bodies. This being the case, it is evident that the onus probandi [burden of proof] ought to lie with those who are willing to establish such an hypothesis, for it does not appear that Nature is in the habit of using one and the same mechanism with any two of our senses. Witness the vibration of air that makes sound, the effluvia that occasion smells, the particles that produce taste, the resistance or repulsive powers that affect the touch—all these are evidently suited to their respective organs of sense.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" on his discovery of the infrared.

“We can hardly suppose a possibility of the production of a globular form without a consequent revolution of the nebulous matter, which in the end may settle in a regular rotation about some fixed axis.”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“In the year 1783 I finished a very good twenty-foot reflector with a large aperture, and mounted it upon the plan of my present telescope. After two years' observation with it, the great advantage of such apertures appeared so clearly to me that I recurred to my former intention of increasing them still further; and being now sufficiently provided with experience in the work which I wished to undertake, the President of the Royal Society, who is always ready to promote useful undertakings, had the goodness to lay my design before the king. His Majesty was graciously pleased to approve of it, and with his usual liberality to support it with his royal bounty.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works".

“The changes that are thus proved to have already happened, prepare us for those that may be expected hereafter to take place, by the gradual condensation of the nebulous matter”

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William Herschel

Astronomical Observations relating to the Construction of the Heavens... (1811)
Contesto: I compared also the present appearance of this nebula with the delineation which Huyghens has given of it in his Systema Saturnium... The changes that are thus proved to have already happened, prepare us for those that may be expected hereafter to take place, by the gradual condensation of the nebulous matter; for had we no where an instance of any alteration in the appearance of nebula, they might be looked upon as permanent celestial bodies, and the successive changes, to which by the action of an attracting principle they have been conceived to be subject, might be rejected as being unsupported by observation.<!-- p. 324

“Instead of inquiring after the nature of the cause of the condensation of nebulous matter, it would indeed be sufficient for the present purpose to call it merely a condensing principle; but since we are already acquainted with the centripetal force of attraction which gives a globular figure to planets, keeps them from flying out of their orbits in tangents, and makes one star revolve around another, why should we not look up to the universal gravitation of matter as the cause of every condensation, accumulation, compression, and concentration of the nebulous matter?”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“We may… have surmised nebulae to be no other than clusters of stars disguised by their very great distance, but a longer experience and better acquaintance with the nature of nebulae, will not allow a general admission of such a principle, although undoubtedly a cluster of stars may assume a nebulous appearance when it is too remote for us to discern the stars of which it is composed.”

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William Herschel

p, 125
Astronomical Observations relating to the Construction of the Heavens... (1811)

“The number of stands I invented for these telescopes it would not be easy to assign. …In 1781 I began to construct a thirty foot aërial reflector, and having made a stand for it, I cast the mirror thirty-six inches in diameter. This was cracked in cooling. I cast it a second time, and the furnace I had built in my house broke.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works".

“These [binary stars] may serve another very important end…. Several stars of the first magnitude have been observed or suspected to have a proper motion; hence we may surmise that our sun, with all its planets and comets, may also have a motion towards some particular point of the heavens…. If this surmise should have any foundation, it will show itself in a series of some years in a kind of systematical parallax, or change due to the motion of the whole solar system.”

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William Herschel

Origine: Sir William Herschel: His Life and Works (1880), Ch.4 "Life and Works" quote from "Researches on the Motion of the Sun and of the Solar System in Space" (1782), p. 149