6 Easy Pieces
Main Takeaways, Questions, Moments of Genius…
→ We do not yet know all the basic laws: there is an expanding frontier of ignorance. Also the correct statement of the laws of physics involves some very unfamiliar ideas which require advanced mathematics for their description. 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. Therefore, things must be learned only to be unlearned again or more likely, to be corrected.
→ The principle of science, the definition almost, is: The test of all knowledge is experiment. Experiment is the sole judge of scientific truth. But what is the source of knowledge? Where do the laws that are to be tested come from? Experiment helps to produce these laws, in the sense that it gives us hints. But also needed is imagination to create from these hints the great generalizations- to guess at the wonderful, simple, but very strange patterns beneath them all, and then to experiment to check again whether we have made the right guess. This imagining process is so difficult that there is a division of labor in physics: there are the theoretical physicists who imagine, deduce, and guess at new laws, but do not experiment; and then there are the experimental physicists who experiment, imagine, deduce, and guess. How can the results of an experiment be wrong? Only be being inaccurate. For example, the mass of an object never seems to change: a spinning top has the same mass as a still one. So a “law” was invented: mass is constant, independent of speed. That “law” is now found to be incorrect. Mass is found to increase with velocity, but appreciable increases require velocities near that of light. A true law is: if an object moves with a speed of less than one hundred miles a second, the mass is constant to within one part in a million. For ordinary speeds we can certainly forget it and use the simple constant-mass law as a good approximation. But for high speeds we are wrong, and the higher the speed, the more wrong we are. Finally and most interestingly, philosophically we are completely wrong with the approximate law. Our entire picture of the world has to be altered even though the mass changes only by a little bit. This is a very peculiar thing about the philosophy, oh the ideas behind the laws. Even in a very small effect sometimes requires profound changes in our ideas.
→ There are circumstances in which atoms change combinations and form new molecules. A process in which the rearrangement of the atomic patterns occurs, is what we call a chemical reaction. The other processes so far described are called physical processes, but there is no sharp distinction between the two. [Nature does not care what we call it, she just keeps on doing it.] In the case of Oxygen, two oxygen atoms stick together very strongly. Why not three or four? That is one of the very peculiar characteristics of such atomic processes. Atoms are very special: they like certain particular partners, certain particular directions, and so on. It is the job of physics to analyze why each one wants what it wants. At any rate, two oxygen atoms form saturated and happy, a molecule.