Feynman's Lost Lecture: The Motion of Planets Around the Sun

Feynman's Lost Lecture: Motion of Planets Around the Sun is a book based on a lecture by Richard Feynman

Richard Feynman

Richard Phillips Feynman was an American physicist known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics...

. Restoration of the lecture notes and conversion into book form was undertaken by Caltech physicist David L. Goodstein and archivist Judith R. Goodstein. Feynman had given the lecture on the motion of bodies at Caltech on March 13, 1964, but the notes and pictures were lost for a number of years and consequently not included in The Feynman Lectures on Physics
The Feynman Lectures on Physics
The Feynman Lectures on Physics is a 1964 physics textbook by Richard P. Feynman, Robert B. Leighton and Matthew Sands, based upon the lectures given by Feynman to undergraduate students at the California Institute of Technology in 1961–63. It includes lectures on mathematics, electromagnetism,...

series. The lecture notes were later found, but unfortunately without the photographs of his illustrative chalkboard

Chalkboard

A chalkboard or blackboard is a reusable writing surface on which text or drawings are made with sticks of calcium sulfate or calcium carbonate, known, when used for this purpose, as chalk. Chalkboards were originally made of smooth, thin sheets of black or dark grey slate stone...

drawings. One of the editors, David L. Goodstein, stated that at first without the photographs, it was very hard to figure out what diagrams he was referring to in the audiotapes, but a later finding of his own private lecture notes made it possible to understand completely the logical framework with which Feynman delivered the lecture.

Overview

You can explain to people who don't know much of the physics, the early history... how Newton discovered... Kepler's Laws, and equal areas, and that means it's toward the sun, and all this stuff. And then the key - they always ask then, "Well, how do you see that it's an ellipse if it's the inverse square?" Well, it's God damned hard, there's no question of that. But I tried to find the simplest one I could.

In a non-course lecture delivered to a freshman physics audience, Feynman undertakes to present an elementary, geometric demonstration of Newton

Isaac Newton

Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

's discovery of the fact that Kepler

Johannes Kepler

Johannes Kepler was a German mathematician, astronomer and astrologer. A key figure in the 17th century scientific revolution, he is best known for his eponymous laws of planetary motion, codified by later astronomers, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican...

's first observation, that the planets travel in elliptical orbits, is a necessary consequence of Kepler's other two observations.

The structure of Feynman's lecture:

A historical introduction to the material
An overview of some geometric properties of an ellipse
Newton's demonstration that equal areas in equal times is equivalent to forces toward the sun
Feynman's demonstration that equal changes in velocity occur in equal angles in the orbit
Feynman's demonstration, using techniques of Fano, that these velocity changes imply that the orbit is elliptical
Discussion of Rutherford's experiments with scattering of alpha particles, and the discovery of the atomic nucleus

The audio recording of the lectures also includes twenty minutes of informal Q&A at the blackboard with students who had attended the lecture.

Overview

See also