Conceptual Science

​ In Chapter 9-2 of The Feynman Lectures on Physics, Richard Feynman pauses to sharpen a distinction that, in everyday language, we often blur: the difference between speed and velocity. Although the two words are used interchangeably in conversation, physics takes advantage of the linguistic redundancy to separate two subtly different ideas. Velocity, in Feynman’s precise usage, is a vector: it possesses both a magnitude and a direction. Speed, by contrast, is reserved for the magnitude of that vector alone. In other words, speed tells us how fast something is moving, whereas velocity tells us how fast and in what direction. Feynman illustrates this distinction by imagining an object moving through three-dimensional space. During a tiny interval of time,  Δ  t, the object experiences three small coordinate changes: Δ  x in the x-direction, Δ  y in the y-direction, Δ  z in the z-direction. These increments form the edges of a small parallelepiped, an...

Few moments in the history of science are as transformative as the discovery of the laws of motion. In Chapter 9–1 of  The Feynman Lectures on Physics , Richard Feynman captures this transformation with his characteristic clarity and enthusiasm. He opens the chapter with an almost dramatic statement: before Newton, the movements of the heavens were a mystery; after Newton, the cosmos itself seemed to obey a comprehensible mathematical order. Pendulums, planets, and springs could all be described by the same underlying principles. Feynman’s goal in this chapter is to guide the reader through that same intellectual journey - from mystery to understanding - showing how Newton’s laws of motion turned vague intuition into precise physical law. Galileo and the Birth of Inertia Feynman begins with Galileo, whose insight into motion marked the first great leap forward. Galileo recognised that an object not acted upon by an external influence would continue to move at a constant speed in a ...