"SIX EASY PIECES: ESSENTIALS OF PHYSICS EXPLAINED BY ITS MOST BRILLIANT TEACHER" by Richard P. Feynman, Robert B. Leighton, Matthew Sands

• Science is a people-driven activity like all human endeavor, and just as subject to fashion and whim. In this case fashion is set not so much by choice of subject matter, but by the way scientists think about the world.
• Theoretical physics is one of the toughest intellectual exercises, combining abstract concepts that defy visualization with extreme mathematical complexity.
• A summation of his teaching philosophy was found among his papers in the Caltech archives, in a note he had scribbled to himself while in Brazil in 1952: First figure out why you want the students to learn the subject and what you want them to know, and the method will result more or less by common sense.
• It’s impossible to learn very much by simply sitting in a lecture, or even by simply doing problems that are assigned.
• Each piece, or part, of the whole of nature is always merely an approximation to the complete truth, or the complete truth so far as we know it. In fact, everything we know is only some kind of approximation, because we know that we do not know all the laws as yet.
• The principle of science, the definition, almost, is the following: The test of all knowledge is experiment. Experiment is the sole judge of scientific “truth.”
• all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another.
• Now the jiggling motion is what we represent as heat: when we increase the temperature, we increase the motion.
• order to confine a gas we must apply a pressure.
• Air consists almost entirely of nitrogen, oxygen, some water vapor, and lesser amounts of carbon dioxide, argon, and other things.
• An ion is an atom which either has a few extra electrons or has lost a few electrons.
• Everything is made of atoms.
• From the point of view of basic physics, the most interesting phenomena are of course in the new places, the places where the rules do not work—not the places where they do work!
• The ultimate basis of an interaction between the atoms is electrical.
• the chemical properties depend upon the electrons on the outside, and in fact only upon how many electrons there are.
• Magnetic influences have to do with charges in relative motion, so magnetic forces and electric forces can really be attributed to one field, as two different aspects of exactly the same thing.
• The electromagnetic field can carry waves; some of these waves are light, others are used in radio broadcasts, but the general name is electromagnetic waves.
• The only thing that is really different from one wave to another is the frequency of oscillation.
• If we increase the frequency to 500 or 1000 kilocycles (1 kilocycle = 1000 cycles) per second, we are “on the air,” for this is the frequency range which is used for radio broadcasts.
• Instead, it was discovered that things on a small scale behave nothing like things on a large scale.
• there is a rule in quantum mechanics that says that one cannot know both where something is and how fast it is moving.
• it is not possible to predict exactly what will happen in any circumstance.
• We just have to take what we see, and then formulate all the rest of our ideas in terms of our actual experience.
• There is no distinction between a wave and a particle. So quantum mechanics unifies the idea of the field and its waves, and the particles, all into one.
• The fact that a particle has zero mass means, in a way, that it cannot be at rest. A photon is never at rest; it is always moving at 186,000 miles a second.
• To summarize it, I would say this: outside the nucleus, we seem to know all; inside it, quantum mechanics is valid—the principles of quantum mechanics have not been found to fail. The stage on which we put all of our knowledge, we would say, is relativistic space-time; perhaps gravity is involved in space-time. We do not know how the universe got started, and we have never made experiments which check our ideas of space and time accurately, below some tiny distance, so we only know that our ideas work above that distance.
• All proteins are not enzymes, but all enzymes are proteins.
• Proteins have a very interesting and simple structure. They are a series, or chain, of different amino acids.
• But the most remarkable discovery in all of astronomy is that the stars are made of atoms of the same kind as those on the earth.
• It is important to realize that in physics today, we have no knowledge of what energy is.
• The general name of energy which has to do with location relative to something else is called potential energy.
• In quantum mechanics it turns out that the conservation of energy is very closely related to another important property of the world, things do not depend on the absolute time.
• What is this law of gravitation? It is that every object in the universe attracts every other object with a force which for any two bodies is proportional to the mass of each and varies inversely as the square of the distance between them.
• First of all, Kepler found that each planet goes around the sun in a curve called an ellipse, with the sun at a focus of the ellipse.
• Kepler’s second observation was that the planets do not go around the sun at a uniform speed, but move faster when they are nearer the sun and more slowly when they are farther from the sun,
• Thus Kepler’s three laws are: I. Each planet moves around the sun in an ellipse, with the sun at one focus. II. The radius vector from the sun to the planet sweeps out equal areas in equal intervals of time. III. The squares of the periods of any two planets are proportional to the cubes of the semimajor axes of their respective orbits: T ∝ a3/2.
• Any great discovery of a new law is useful only if we can take more out than we put in.
• The moon pulls the water up under it and makes the tides—people
• If a law does not work even in one place where it ought to, it is just wrong.
• so far as we now know, gravity seems to go out forever inversely as the square of the distance.
• Even light, which has an energy, has a “mass.”
• “Quantum mechanics” is the description of the behavior of matter in all its details and, in particular, of the happenings on an atomic scale.