What makes these lectures timeless? Elementary physics has been taught to undergraduates for nearly a century with relatively little change. Over the past 50 years the subject has been even more static. Textbooks and introductory courses have largely targeted those planning to study medicine and engineers with a focus on formulaic problem-solving and exam preparation, rather than cultivating a wonder for nature and the development of physical intuition.
Superficially, Feynman’s primer touches on the same topics that others do: mechanics, thermodynamics, optics, electricity and magnetism, and modern physics. Beneath this veneer of common cause, his introduction to elementary physics seems to have higher aspirations — the love of nature and a grasp of it through experimentation and reasoning. In Feynman’s hands, even a topic as mundane as projectile motion becomes the story of how Galileo and Newton unlocked the secrets of planetary motion. Feynman’s physics is about simplicity, beauty, unity and analogy, presented with enthusiasm and insight that bursts from the page.
He works this magic even in areas often thought to be the most boring parts of the curriculum. For example, his fascination with the way that Newton's second law of motion, F = ma, can describe the motions of large, composite objects such as galaxies leads intuitively to the profound idea of the centre of mass. Feynman also repeatedly appeals to 'variational' principles based on minimizing quantities such as travel time (pictured). This is seen nowhere more impressively than in the way he develops optics by thinking about the transit of light rays as they pass through various media, whether lenses or the atmosphere. These same ideas return in his treatment of the elliptical motions of planets. When talking about Brownian motion (the random movement of particles in a gas or liquid as they collide with molecules of that medium), he elegantly teaches us the fluctuation–dissipation theorem, which relates how rapidly particles diffuse to the drag force they experience, without ever naming it as such. And he similarly provides an advanced but accessible introduction to elasticity — the likes of which, unfortunately, advanced physics students rarely see even now.
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Rob Phillips, Fred and Nancy Morris Professor of Biophysics and Biology
Reprinted by permission from Macmillan Publishers Ltd: Nature, 2013