The Feynman Lectures on Physics Vol 1 Quotes

“psychoanalysis is not a science: it is at best a medical process, and perhaps even more like witch-doctoring.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“Mathematics is not a science from our point of view, in the sense that it is not a natural science. The test of its validity is not experiment.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“It is probably better to realize that the probability concept is in a sense subjective, that it is always based on uncertain knowledge, and that its quantitative evaluation is subject to change as we obtain more information.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“Philosophers have said before that one of the fundamental requisites of science is that whenever you set up the same conditions, the same thing must happen. This is simply not true, it is not a fundamental condition of science.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“In learning any subject of a technical nature where mathematics plays a role, one is confronted with the task of understanding and storing away in the memory a huge body of facts and ideas, held together by certain relationships which can be “proved” or “shown” to exist between them. It is easy to confuse the proof itself with the relationship which it establishes. Clearly, the important thing to learn and to remember is the relationship, not the proof. In any particular circumstance we can either say “it can be shown that” such and such is true, or we can show it. In almost all cases, the particular proof that is used is concocted, first of all, in such form that it can be written quickly and easily on the chalkboard or on paper, and so that it will be as smooth-looking as possible. Consequently, the proof may look deceptively simple, when in fact, the author might have worked for hours trying different ways of calculating the same thing until he has found the neatest way, so as to be able to show that it can be shown in the shortest amount of time! The thing to be remembered, when seeing a proof, is not the proof itself, but rather that it can be shown that such and such is true. Of course, if the proof involves some mathematical procedures or “tricks” that one has not seen before, attention should be given not to the trick exactly, but to the mathematical idea involved.”
― Richard Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat

“there is a physical problem that is common to many fields, that is very old, and that has not been solved. It is not the problem of finding new fundamental particles, but something left over from a long time ago—over a hundred years. Nobody in physics has really been able to analyze it mathematically satisfactorily in spite of its importance to the sister sciences. It is the analysis of circulating or turbulent fluids.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“Although it is interesting and worth while to study the physical laws simply because they help us to understand and to use nature, one ought to stop every once in a while and think, “What do they really mean?” The meaning of any statement is a subject that has interested and troubled philosophers from time immemorial, and the meaning of physical laws is even more interesting, because it is generally believed that these laws represent some kind of real knowledge. The meaning of knowledge is a deep problem in philosophy, and it is always important to ask, “What does it mean?”
― Richard Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat

“What else can you do with the law of gravitation? If we look at the moons of Jupiter we can understand everything about the way they move around that planet. Incidentally, there was once a certain difficulty with the moons of Jupiter that is worth remarking on. These satellites were studied very carefully by Rømer, who noticed that the moons sometimes seemed to be ahead of schedule, and sometimes behind. (One can find their schedules by waiting a very long time and finding out how long it takes on the average for the moons to go around.) Now they were ahead when Jupiter was particularly close to the earth and they were behind when Jupiter was farther from the earth. This would have been a very difficult thing to explain according to the law of gravitation—it would have been, in fact, the death of this wonderful theory if there were no other explanation. If a law does not work even in one place where it ought to, it is just wrong. But the reason for this discrepancy was very simple and beautiful: it takes a little while to see the moons of Jupiter because of the time it takes light to travel from Jupiter to the earth. When Jupiter is closer to the earth the time is a little less, and when it is farther from the earth, the time is more. This is why moons appear to be, on the average, a little ahead or a little behind, depending on whether they are closer to or farther from the earth. This phenomenon showed that light does not travel instantaneously, and furnished the first estimate of the speed of light. This was done in 1676.”
― Richard P. Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat

“We could, of course, use any notation we want; do not laugh at notations; invent them, they are powerful. In fact,mathematics is, to a large extent, invention of better notations.”
― Richard Feynman, The Feynman Lectures on Physics Vol 1

“There was an interesting early relationship between physics and biology in which biology helped physics in the discovery of the conservation of energy, which was first demonstrated by Mayer in connection with the amount of heat taken in and given out by a living creature.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“No phenomenon directly involving a frequency has yet been detected above approximately 10^12 cycles per second. We only deduce the higher frequencies from the energy of the particles, by a rule which assumes that the particle-wave idea of quantum mechanics is valid.”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“So we see that a substance’s properties must be limited in a certain way; one cannot make up anything he wants, or he would be able to invent a substance which he could use to produce more than the maximum allowable work when he carried it around a reversible cycle. This principle, this limitation, is the only real rule that comes out of the thermodynamics.”
― Richard P. Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat

“Now the jiggling motion is what we represent as heat:
when we increase the temperature, we increase the motion. If we heat the water,
the jiggling increases and the volume between the atoms increases, and if the
heating continues there comes a time when the pull between the molecules is not
enough to hold them together and they do fly apart and become separated from
one another. Of course, this is how we manufacture steam out of water—by
increasing the temperature; the particles fly apart because of the increased motion.”
― Richard Feynman, The Feynman Lectures on Physics Vol 1

“Even a very small effect sometimes requires profound changes in our ideas”
― Richard Feynman, The Feynman Lectures on Physics Vol 1

“Only with quantitative observations can one arrive at quantitative relationships, which are the heart of physics.”
― Richard P. Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat

“If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or atomic fact, or whatever you wish to call it) that all things are made of atoms...(italics in original).”
― Richard Feynman, The Feynman Lectures on Physics Vol 1

“A description of nature is what we are concerned with here. From this point
of view, then, a gas, and indeed all matter, is a myriad of moving particles. Thus
many of the things we saw while standing at the seashore can immediately be
connected. First the pressure: this comes from the collisions of the atoms with
the walls or whatever; the drift of the atoms, if they are all moving in one direc-
tion on the average, is wind; the random internal motions are the heat. There are
waves of excess density, where too many particles have collected, and so as they
Tush off they push up piles of particles farther out, and so on. This wave of excess
density is sound. It is a tremendous achievement to be able to understand so much.
Some of these things were described in the previous chapter.”
― Richard Feynman, The Feynman Lectures on Physics Vol 1

“We do not yet know all the basic laws: there is an expanding frontier of ignorance”
― Richard P. Feynman, The Feynman Lectures on Physics Vol 1

“else can you do with the law of gravitation? If we look at the moons of Jupiter we can understand everything about the way they move around that planet. Incidentally, there was once a certain difficulty with the moons of Jupiter that is worth remarking on. These satellites were studied very carefully by Rømer, who noticed that the moons sometimes seemed to be ahead of schedule, and sometimes behind. (One can find their schedules by waiting a very long time and finding out how long it takes on the average for the moons to go around.) Now they were ahead when Jupiter was particularly close to the earth and they were behind when Jupiter was farther from the earth. This would have been a very difficult thing to explain according to the law of gravitation—it would have been, in fact, the death of this wonderful theory if there were no other explanation. If a law does not work even in one place where it ought to, it is just wrong. But the reason for this discrepancy was very simple and beautiful: it takes a little while to see the moons of Jupiter because of the time it takes light to travel from Jupiter to the earth. When Jupiter is closer to the earth the time is a little less, and when it is farther from the earth, the time is more. This is why moons appear to be, on the average, a little ahead or a little behind, depending on whether they are closer to or farther from the earth. This phenomenon showed that light does not travel instantaneously, and furnished the first estimate of the speed of light. This was done in 1676.”
― Richard P. Feynman, The Feynman Lectures on Physics, Vol. I: The New Millennium Edition: Mainly Mechanics, Radiation, and Heat