Isaac Newton’s Legacy

Today’s installment concludes Discovery of Gravity,
our selection from Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton by Sir David Brewster published in 1855.

If you have journeyed through all of the installments of this series, just one more to go and you will have completed a selection from the great works of six thousand words. Congratulations! For works benefiting from the latest research see the “More information” section at the bottom of these pages.

Previously in Discovery of Gravity.

Time: 1666
Place: Woolsthrope, England

Although there could be little doubt that the comets were retained in their orbits by the same laws which regulated the motions of the planets, yet it was difficult to put this opinion to the test of observation. The visibility of comets only in a small part of their orbits rendered it difficult to ascertain their distance and periodic times; and as their periods were probably of great length, it was impossible to correct approximate results by repeated observations. Newton, however, removed this difficulty by showing how to determine the orbit of a comet, namely, the form and position of the orbit, and the periodic time, by three observations. By applying this method to the comet of 1680 he calculated the elements of its orbit, and, from the agreement of the computed places with those which were observed, he justly inferred that the motions of comets were regulated by the same laws as those of the planetary bodies. This result was one of great importance; for as the comets enter our system in every possible direction, and at all angles with the ecliptic, and as a great part of their orbits extends far beyond the limits of the solar system, it demonstrated the existence of gravity in spaces far removed beyond the planet, and proved that the law of the inverse ratio of the squares of the distance was true in every possible direction, and at very remote distances from the center of our system.

Such is a brief view of the leading discoveries which the Principia first announced to the world. The grandeur of the subjects of which it treats, the beautiful simplicity of the system which it unfolds, the clear and concise reasoning by which that system is explained, and the irresistible evidence by which it is supported might have insured it the warmest admiration of contemporary mathematicians and the most welcome reception in all the schools of philosophy throughout Europe. This, however, is not the way in which great truths are generally received. Though the astronomical discoveries of Newton were not assailed by the class of ignorant pretenders who attacked his optical writings, yet they were everywhere resisted by the errors and prejudices which had taken a deep hold even of the strongest minds.

The philosophy of Descartes was predominant throughout Europe. Appealing to the imagination, and not to the reason, of mankind it was quickly received into popular favor, and the same causes which facilitated its introduction, extended its influence and completed its dominion over the human mind. In explaining all the movements of the heavenly bodies by a system of vortices in a fluid medium diffused through the universe Descartes had seized upon an analogy of the most alluring and deceitful kind. Those who had seen heavy bodies revolving in the eddies of a whirlpool or in the gyrations of a vessel of water thrown into a circular motion had no difficulty in conceiving how the planets might revolve round the sun by an analogous movement. The mind instantly grasped at an explanation of so palpable a character and which required for its development neither the exercise of patient thought nor the aid of mathematical skill. The talent and perspicuity with which the Cartesian system was expounded, and the show by which it was sustained, contributed powerfully to its adoption, while it derived a still higher sanction from the excellent character and the unaffected piety of its author.

Thus entrenched, as the Cartesian system was, in the strongholds of the human mind, and fortified by its most obstinate prejudices, it was not to be wondered at that the pure and sublime doctrines of the Principia, were distrustfully received and perseveringly resisted. The uninstructed mind could not readily admit the idea that the great masses of the planets were suspended in empty space and retained in their orbits by an invisible influence residing in the sun; and even those philosophers who had been accustomed to the rigor of true scientific research, and who possessed sufficient mathematical skill for the examination of the Newtonian doctrines, viewed them at first as reviving the occult qualities of the ancient physics, and resisted their introduction with a pertinacity which it is not easy to explain.

Prejudiced, no doubt, in favor of his own metaphysical views, Leibnitz himself misapprehended the principles of the Newtonian philosophy, and endeavored to demonstrate the truths in the Principia by the application of different principles. Huygens, who above all other men was qualified to appreciate the new philosophy, rejected the doctrine of gravitation as existing between the individual particles of matter and received it only as an attribute of the planetary masses. John Bernouilli, one of the first mathematicians of his age, opposed the philosophy of Newton. Mairan, in the early part of his life, was a strenuous defender of the system of vortices. Cassini and Maraldi were quite ignorant of the Principia, and occupied themselves with the most absurd methods of calculating the orbits of comets long after the Newtonian method had been established on the most impregnable foundation; and even Fontenelle, a man of liberal views and extensive information, continued, throughout the whole of his life, to maintain the doctrines of Descartes.

The chevalier Louville of Paris had adopted the Newtonian philosophy before 1720; Gravesande had introduced it into the Dutch universities at a somewhat earlier period; and Maupertuis, in consequence of a visit which he paid to England in 1728, became a zealous defender of it; but notwithstanding these and some other examples that might be quoted, we must admit the truth of the remark of Voltaire, that though Newton survived the publication of the Principia more than forty years, yet at the time of his death he had not above twenty followers out of England.

This ends our series of passages on Discovery of Gravity by Sir David Brewster from his book Memoirs of the Life, Writings and Discoveries of Sir Isaac Newton published in 1855. This blog features short and lengthy pieces on all aspects of our shared past. Here are selections from the great historians who may be forgotten (and whose work have fallen into public domain) as well as links to the most up-to-date developments in the field of history and of course, original material from yours truly, Jack Le Moine. – A little bit of everything historical is here.

More information on Discovery of Gravity here and here and below.

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