Newtonianism

“ Moreover, his assertion that the notion of a body acting where it is not, is one that no competent thinker could entertain, is antagonistic to the whole current conception of attractive and repulsive forces, and therefore of "the attractive force of gravitation." What, then, was that labour of unsurpassed magnitude and excellence and immortal influence which Newton did perform? In the first place, Newton defined the laws, rules, or observed order of the phenomena of motion, which come under our daily observation, with greater precision than had been before attained ”

“ And an entire command of the conceptions and processes of mathematics is not only consistent with, but is the necessary condition and principal instrument of every important step in the discovery of physical principles. Newton was eminent above the philosophers of his time, in no one talent so much as in the power of mathematical deduction. When he had caught sight of the law of universal gravitation, he traced it to its consequences with a rapidity, a dexterity, a beauty of mathematical reasoning which no other person could approach ”

“ Judging from what we know of physical laws, we may expect the which belongs to it to be distinguished by having simple mathematical properties. Physics, this time as a physics of fields, is again pursuing the object of reducing the totality of natural phenomena to a single physical law: it was believed that this goal was almost within reach once before when Newton’s Principia, founded on the physics of mechanical point-masses, was celebrating its triumphs. But the treasures of knowledge are not like ripe fruits that may be plucked from a tree. ”

“ Newton was a Christian; Newton, whose mind burst forth from the fetters fastened by nature upon our288 finite conceptions; Newton, whose science was truth, and the foundations of whose knowledge of it was philosophy; not those visionary and arrogant presumptions which too often usurp its name, but philosophy resting upon the basis of mathematics, which, like figures, can not lie; Newton, who carried the line and rule to the uttermost barriers of creation, and explored the principles by which all created matter exists and is held together. ”

“ Chemistry here comes to the aid of mechanics, and we may say boldly that that matter, which is identical with ours, is subject, like it, to the laws of gravitation. Certainly, when Newton decomposed a beam of white light, and laid the first basis of the theory of the spectrum, he had not the slightest suspicion that his law of gravitation would, at a later period, find in it wings to carry it into regions where all measurement ceases and all calculation is powerless. ”

“ But it is obvious that we have no right to assume that Newton’s law or those of mechanics are above all suspicion. The laws of physical science present no a priori inevitableness; and our sole reason for accepting them is because they appear to be borne out to a high degree of approximation when we compare their rational consequences with the results of observation. Approximation is thus all we can aspire to in physical science; and even classical scientists recognised the possibility that more precise observation might prove Newton’s law and those of mechanics to stand in need of correction. ”

“ And so it would be, if truths, like the sun, rose by their own proper motion, without human effort; but not otherwise. I believe that if Newton had not lived, the world must have waited for the Newtonian philosophy until there had been another Newton, or his equivalent. No ordinary man, and no succession of ordinary men, could have achieved it. I will not go the length of saying that what Newton did in a single life, might not have been done in successive steps by some of those who followed him, each singly inferior to him in genius. ”

“ Monsieur Roger continued:
"By much reflection, by hard work and calculation, Newton made an admirable discovery,—that of universal attraction. Yes, he discovered that all bodies, different though they may be, attract each other: they draw towards each other; the bodies which occupy the celestial spaces,—planets and suns,—as well as the bodies which are found upon our earth. The force which attracts bodies towards the earth, which made this stone fall, as Newton's apple fell, has received the name of weight. ”

“ These little globes, so fragile that they disappear in a breath, hardly seem worthy of the attention of a thinker, and still less the examination of a philosopher; but it is nevertheless true that Newton made experiments on the colours shown on the surface of these apparently insignificant objects which ended in the most brilliant discoveries, just as on seeing an apple fall he began a train of thought which only terminated in the enunciation of the hypothesis of the earth's power of gravity. ”

“ That the Principia of Newton should have remained so generally unknown in this country to the present day is a somewhat remarkable fact; because the name of the author, learned with the very elements of science, is revered at every hearth-stone where knowledge and virtue are of chief esteem, while, abroad, in all the high places of the land, the character which that name recalls is held up as the noblest illustration of what Man may be, and may do, in the possession and manifestation of pre-eminent intellectual and moral worth ”

“ Newton himself does not appear to have been averse to explaining gravity by impulse. So little is it true that if one theory be true the other must be false. The attempt to explain gravity by the impulse of streams of particles flowing through the universe in all directions, which I have mentioned in the Philosophy, is so far from being inconsistent with the Newtonian theory, that it is founded entirely upon it. And even with regard to the doctrine, that the heavenly bodies move by an inherent virtue ”

“ As a matter of fact, it is little short of a miracle, in view of the insignificance of our mathematical ability, that theoretical physics should have been possible at all. Had our solar system contained two suns such as are present in the double-star systems, or had one of the planets been comparable in size to the sun, it is safe to say that Newton, in spite of his genius, would never have discovered his law of gravitation ”

“ Newton is not well understood even in our days. Some dictionaries say that Newton discovered the law of gravity. This law was introduced by Newton to save his theory. The inertia principle states that any material body, which is left free, is moving in a straight line, with constant velocity to infinity. But in the external reality such a phenomenon is not met. The planets are moving on closed trajectories in space. The only solution to save the theory was to invent a new force, which was called "gravity". ”

“ When Newton, in this manner, discovered the laws of the solar system, he created, for all posterity, the true idea of science. He gave the most perfect example we are ever likely to have, of that union of reasoning and observation, which by means of facts that can be directly observed, ascends to laws which govern multitudes of other facts laws which not only explain and account for what we see, but give us assurance before hand of much that we do not see, much that we never could have found out by observation, though, having been found out, it is always verified by the result. ”

“ And the advantage thus derived, as we have seen, is not confined to the astronomer, who has often been able, by making fundamental physical and chemical discoveries, to repay his debt to the physicist and chemist for the apparatus and methods which he owes to them.
NEWTON AND EINSTEIN Take, for another example, the greatest law of physics—Newton's law of gravitation. Huge balls of lead, as used by Cavendish, produce by their gravitational effect a minute rotation of a delicately suspended bar, carrying smaller balls at its extremities. But no such feeble means sufficed for Newton's purpose. ”

“ Newton, in whose fertile and capacious intellect the dim, nebulous elements of truth were condensed by patient thinking into the completed star, discovered the most universal of all natural laws, the law of gravitation, before he was twenty-five, though an error of observation, not his own, prevented him from demonstrating it until he was forty. ”

“ And yet the explanation does not wholly satisfy you? Very likely: to some phenomena there is, as yet, no explanation. Perhaps Newton himself could not explain quite to his own satisfaction why he was haunted at midnight by the spectrum of a sun; though I have no doubt that some later philosopher whose ingenuity has been stimulated by Newton's account, has, by this time, suggested a rational solution of that enigma. [8] To return to your own case. I have offered such interpretations of the mysteries that confound you as appear to me authorized by physiological science. ”

“ This part of mechanics was cultivated by the ancients in the five powers which relate to manual arts, who considered gravity (it not being a manual power) , no otherwise than as it moved weights by those powers. Our design not respecting arts, but philosophy, and our subject not manual but natural powers, we consider chiefly those things which relate to gravity, levity, elastic force, the resistance of fluids, and the like forces, whether attractive or impulsive; and therefore we offer this work as the mathematical principles if philosophy ”

“ It must be remembered that the successors of Newton were very apt to declare that Newton had demonstrated attraction as a physical cause: he had taken reasonable pains to show that he did not pretend to this. If any one had said to Newton, I hold that every particle of matter is a responsible being of vast intellect, ordered by the Creator to move as it would do if every other particle attracted it, and gifted with power to make its way in true accordance with that law, as easily as a lady picks her way across the street ”

“ Newton himself had not been able to realize the conception, or we should not have had his hypothesis of a subtle ether, the occult cause of gravitation; and his writings prove, that although he deemed the particular nature of the intermediate agency a matter of conjecture, the necessity of some such agency appeared to him indubitable. It would seem that even now the majority of scientific men have not completely got over this very difficulty ”

“ Now, a general theorem of mechanics proves that whenever a body is moving under the attraction of a central body, the law of areas is always verified; whence we must conclude that the sun could never be considered as rotating round the earth under the sole action of the earth’s attraction. Supplementary forces would have had to be brought into play, but their introduction would have been so arbitrary, and the mathematical difficulties so great that even Newton might have been nonplussed ”

“ If we are concerned solely with the facts of planetary motion and mechanics known to Newton, then Newton’s laws of mechanics and his law of gravitation are by far the simpler. But if we supplement the facts known to him with those more recently discovered, Einstein’s synthesis has the advantage, for Newton’s co-ordination would necessitate a number of additional hypotheses ad hoc. In the same way, so far as our everyday experience is concerned, a non-rotating earth is the simpler solution, whereas, when the planetary motions are taken into consideration, the reverse holds true. ”

“ Six years later a new determination of the size of the earth gave him a new basis for calculation, and, in an excitement so great that he could hardly see his figures, Newton found that the fall of a stone to the earth and the sweep of the moon in her orbit were due to the same cause. The mechanism by means of which the force is exerted remained unrevealed to Newton, and has baffled all inquirers since his day, but the discovery that all the movements of the heavens could be described by one simple physical law, represents the greatest achievement in the history of science. ”

“ Of course we purchase our emancipation from the fundamental difficulties mentioned, at the cost of a modification and complication of Newton's law which has neither empirical nor theoretical foundation. We can imagine innumerable laws which would serve the same purpose, without our being able to state a reason why one of them is to be preferred to the others; for any one of these laws would be founded just as little on more general theoretical principles as is the law of Newton. ”

“ In our moon we have a neighbour which has long been in the habit of answering truthfully questions addressed to her by astronomers. Of old, she told Newton about gravitation, and when he doubted, and urged opposing evidence offered—as men in his time supposed—by the earth, she set him on the right track, so that when in due time the evidence offered by the earth was corrected, Newton was prepared at once to accept and propound the noble theory which rendered his name illustrious. ”

“ Some there are who say that gravity is præternatural, and call it a perpetual miracle. Therefore they would have it rejected, because præternatural causes have no place in physics. It is hardly worth while to spend time in answering this ridiculous objection which overturns all philosophy. For either they will deny gravity to be in bodies; which cannot be said; or else, they will therefore call it præternatural because it is not produced by the other affections of bodies, and therefore not by mechanical causes. But certainly there are primary affections of bodies ”