Conceptual Science

Richard Feynman’s  Lectures on Physics  are famous not just for their clarity, but for the way in which he draws the reader into the very texture of physical thought. Chapter 8–1, “Description of Motion,” exemplifies this gift. At first sight, the subject appears trivial: how does one describe the movement of a car or a ball? Yet, as Feynman shows, even the simplest description conceals subtleties and points of philosophical depth. Feynman begins with a straightforward claim:  to discover laws, we must first be able to describe change.  The most obvious kind of change in the physical world is a change of position with time - motion. This is the essential foundation, because without a clear way to record and communicate motion, the more advanced laws of dynamics and mechanics cannot even be formulated. His examples are deliberately homely: a car’s radiator cap, the centre of a falling ball. Such illustrations ground the discussion in everyday experience, while simulta...

Newton’s law of gravitation had reigned unchallenged for more than two centuries. Its elegance was undeniable: every mass in the Universe attracts every other with a force proportional to their masses and inversely proportional to the square of their distance. For the orbits of planets, the tides, the fall of apples, it worked with clockwork precision. Yet it carried a hidden assumption: that this gravitational influence was instantaneous. If Jupiter were nudged in its orbit, Earth would “know” at once. To Newton himself, this was an uncomfortable mystery - he admitted he had no mechanism for how gravity acted at a distance. But for generations, physicists accepted the law because it worked. By the early 20th century, Einstein’s special relativity had set a hard limit: no information, no cause or effect, could travel faster than the speed of light. If gravity was instantaneous, it would violate this principle. Something had to give. The solution was General Relativity - a theory in whi...

In Chapter 7-7 of  The Feynman Lectures on Physics , Richard Feynman probes a deceptively simple question— what is gravity?  He begins by highlighting that Newton’s law of universal gravitation is profoundly successful in describing planetary motion yet remains silent on  why  gravity occurs—it doesn’t explain the mechanism, only the mathematics. Feynman muses that this abstraction is characteristic of physics: laws like energy conservation or mechanics provide accurate, predictive formulas without delving into the underlying machinery. He illustrates how speculative models such as the “particle wind” or push-gravity idea—where high-speed particles bombard Earth unevenly due to screening by the Sun—can reproduce the inverse-square law yet fail elsewhere, producing an unreal orbital drag that doesn’t align with observation. To ground the discussion, Feynman recalls the extraordinary precision experiments of  Loránd Eötvös , a Hungarian physicist working in the ea...

In  Chapter 7-6  of  The Feynman Lectures on Physics , Richard Feynman poses a wonderfully straightforward question: if gravitation reaches across the void between planets and stars, why can’t we simply measure it here on Earth by placing a marble next to a heavy ball of lead and watching them draw together? The answer, as he explains, is that the gravitational force between such objects is vanishingly small. Detecting it demands extraordinary care: sealing the apparatus against air currents, avoiding any electrical charge, and measuring movements so tiny they flirt with invisibility. The man who first succeeded in this endeavour was  Henry Cavendish , whose famous experiment was designed to measure the strength of gravity directly between laboratory-sized masses. By doing so, he could determine the gravitational constant  G , the last unknown in Newton’s universal law of gravitation, and from that deduce the mass of the Earth itself. Cavendish called it “weighi...

In Chapter 7-5 of  The Feynman Lectures on Physics , titled  Universal Gravitation , Richard Feynman offers a profound reflection on how far Newton’s law of gravitation can be stretched—beyond apples and planetary orbits, out to the farthest reaches of the cosmos. It is a tour not just of gravitational theory, but of its explanatory power, its history, and the surprising way it links local phenomena to the structure of the universe itself. Let us walk through this chapter, adding historical depth and scientific detail to the many examples Feynman touches upon. The Shape of the Earth and Other Spheres Feynman opens with a deceptively simple question:  Why is the Earth round?  The answer, grounded in Newton’s law, is that  gravity pulls matter inward , trying to minimise potential energy. The Earth’s roughly spherical shape is the result of gravity acting uniformly in all directions over geologic time. But the Earth isn’t a perfect sphere—it’s slightly  flatt...

In Chapter 7-4 of  The Feynman Lectures on Physics , Richard Feynman takes us on a journey not just through physics but through the intellectual revolution triggered by  Sir Isaac Newton  in the 17th century. Titled  Newton’s Law of Gravitation , the lecture is a lucid and imaginative exposition that connects planetary motion with a simple fact: objects fall. What begins as an inquiry into Kepler’s laws blossoms into Newton’s powerful realisation that the force keeping the  moon in orbit  is the same force that pulls  apples to the ground . It’s a chapter rich in insight, narrative flair, and deeply revealing examples. From Kepler’s Laws to Newton’s Generalisation Feynman starts with Newton’s appreciation of  Kepler’s second law , the principle that planets sweep out equal areas in equal times. This seemingly geometric truth holds a deeper message: it tells us that the force acting on a planet must be  centrally directed , pointing straight a...