Hitherto we have explained the phenomena of the heavens and of our sea by the power of gravity, but have not yet assigned the cause of this power. This is certain, that it must proceed from a cause that penetrates to the very centres of the sun and planets, without suffering the least diminution of its force; that operates not according to the quantity of the surfaces of the particles upon which it acts (as mechanical causes used to do), but according to the quantity of the solid matter which they contain, and propagates its virtue on all sides to immense distances, decreasing always as the inverse square of the distances.

And with respect to the general cause, it seems manifest to me that it is none other than God himself, who, in the beginning, created matter along with motion and rest, and now by his ordinary concourse alone preserves in the whole the same amount of motion and rest that he placed in it. For although motion is nothing in the matter moved but its mode, it has yet a certain and determinate quantity, which we easily see may remain always the same in the whole universe, although it changes in each of the parts of it.

The initial shock [of acceleration] is the worst part of it, for he is thrown upward as if by an explosion of gun powder…. Therefore he must be dazed by opiates beforehand; his limbs must be carefully protected so that they are not torn from him and the recoil is spread over all parts of his body. Then he will meet new difficulties: immense cold and inhibited respiration…. When the first part of the journey is completed, it becomes easier because on such a long journey the body no doubt escapes the magnetic force of the earth and enters that of the moon, so that the latter gets the upper hand. At this point we set the travellers free and leave them to their own devices: like spiders they will stretch out and contract, and propel themselves forward by their own force – for, as the magnetic forces of the earth and moon both attract the body and hold it suspended, the effect is as if neither of them were attracting it – so that in the end its mass will by itself turn toward the moon.

First of all, it is necessary to note that each pendulum has its own time of vibration, so limited and fixed in advance that it is impossible to move it in any other period than its own unique natural one. Take in hand any string you like, to which a weight is attached, and try the best you can to increase or diminish the frequency of its vibrations; this will be a mere waste of effort. On the other hand, we confer motion on any pendulum, though heavy and at rest, by merely blowing on it. This motion may be quite large if we repeat our puffs; yet it will take place only in accord with the time appropriate to its oscillations. If at the first puff we shall have moved it half an inch from the vertical, by adding the second when, returned toward us, it would commence its second vibration, we confer a new motion on it; and thus successively with more puffs given at the right time (not when the pendulum is going toward us, for thus we should impede the motion and not assist it), and continuing with many impulses, we shall confer on it impetus such that much greater force than a breath would be needed to stop it.

The heavenly motions are nothing but a continuous song for several voices (perceived by the intellect, not by the ear); a music which, through discordant tensions, through sincopes and cadenzas, as it were (as men employed them in imitation of those natural discords), progresses towards certain predesigned, quasi six-voiced clausuras, and thereby sets landmarks in the immeasurable flow of time, tt is, therefore, no longer surprising that man, in imitation of his creator, has at last discovered the art of figured song, which was unknown to the ancients. Man wanted to reproduce the continuity of cosmic time within a short hour, by an artful symphony for several voices, to obtain a sample test of the delight of the Divine Creator in His works, and to partake of his joy by making music in imitation of God.

Nature and Nature's law lay hid in night.

God said: “Let Newton be”; and all was light.

Everybody knows that heat can cause movement, that it possesses great motive power; steam engines so common today are a vivid and familiar proof of it. … The study of these engines is of the greatest interest, their importance is enormous, and their use increases every day. They seem destined to produce a great revolution in the civilized world….

Despite studies of all kinds devoted to steam engines, and in spite of the satisfactory state they have reached today, the theory of them has advanced very little and the attempts to improve them are still directed almost by chance.

“Also I do not at all believe that the judgment wch is given can be taken for a final judgment of the [Royal] Society. Yet Mr Newton has caused it to be published to the world by a book printed expressly for discrediting me, and sent it into Germany, into France and into Italy in the name of the Society …

As for me I have always carried myself with the greatest respect that could be towards Mr Newton. And tho it appears now that there is great room to doubt whether he knew my invention before he had it from me; yet I have spoken as if he had of himself found something like my method; but being abused by some flatterers ill advised, he has taken the liberty to attaque me in a manner very sensible. Judge now Sr, from what side that should principally come wch is requisite to terminate this controversy.”

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 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.

It is amazing! Although I had as yet no clear idea of the order in which the perfect solids had to be arranged, I nevertheless succeeded … in arranging them so happily, that later on. when I checked the matter over, I had nothing to alter. Now I no longer regretted the lost time; I no longer tired of my works; I shied from no computation, however difficult. Day and night I spent with calculations to see whether the proposition that i had formulated tallied with the Copernican orbits or whether my joy would be carried away by the winds…. Within a few days everything fell into its place. I saw one symmetrical solid after the other fit in so precisely between the appropriate orbits, that if a peasant were to ask you on what kind of hook the heavens are fastened so that they don't fall down, it would be easy for thee to answer him. Farewell!

In the center of all the celestial bodies rests the sun. For who could in this most beautiful temple place this lamp in another or better place than that from which it can illuminate everything at the same time? Indeed, it is not unsuitable that some have called it the light of the world; others, its mind, and still others, its ruler. Trismegistus calls it the visible God; Sophocles' Electra, the all-seeing. So indeed, as if sitting on a royal throne, the Sun rules the family of the stars which surround it.

You see, therefore, that living force [kinetic energy] may be converted into heat, and that heat may be converted into living force, or its equivalent attraction through space. All three, therefore – namely, heat, living force, and attraction through space (to which I might also add light, were it consistent with the scope of the present lecture) – are mutually convertible into one another. In these conversions nothing is ever lost. The same quantity of heat will always be converted into the same quantity of living force. We can therefore express the equivalency in definite language applicable at all times and under all circumstances.

And in each of these decades [the 1950s and 1960s] more oil was consumed than in all of man's previous history combined.

A prominent literary writer, I think it was Chesterton, once spoke of the electron as “only the latest hypothesis which will in its turn give way to the abra-ca-da-bra of tomorrow.” This sort of ignorance will disappear in time, just as will Kipling's “village that voted the earth was flat, flat as my hat, flatter than that:” In any case, the most direct and unambiguous proof of the existence of the electron will probably be generally admitted to be found in the oil-drop experiment here under discussion.

Then from these forces, by other propositions which are also mathematical, I deduce the motions of the planets, the comets, the moon, and the sea. I wish we could derive the rest of the phenomena of Nature by the same kind of reasoning from mechanical principles, for I am induced by many reasons to suspect that they may alt depend upon certain forces by which the particles of bodies, by some cause hitherto unknown, are either mutually impelled towards one another, and cohere in regular figures, or are repelled and recede from one another. These forces being unknown, philosophers have hitherto attempted the search of Nature in vain, but I hope the principles here laid down will afford some light either to this or some truer method of philosophy.

I often say that when you can measure what you are speaking about and express it in numbers you know something about it; but when you cannot measure it, express it in numbers, your knowledge is of a meagre and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science.