Feynman Lectures on Physics

Volume 1

  • Three body problem is a very simple model that shows that the power of mathematical analysis are limited and it is necessary to use numerical methods.
  • The Physical world is complex and precise rigorous mathematical definitions never work in the real world. Phyiscs needs an approximate view of nature to make progress.
  • Torque is defined in direct analogue with Forse x distance = Work. Torque x angle = Work.
  • If Newtons laws is right on a certain small scale, then it will be right on a larger scale. We can consider a baseball as composed of many interacting particles obeying Newtons laws or we can consider it as the ball as a whole obeying Newtons Law.
  • To solve the algebreic equation x2 = -1, you have to introduce a new form of number i. Its a miracle that once you do this you can then solve every algebric equation. You might naively think that each equation that comes along may need its own new construction.
  • Imaginary numbers are the connection/unification of algebra and geometry.
  • The magnetic field in a light wave leads to a force on the electron in the direction of the wave. When light shines on a charge and the charge oscillates there is a driving force in the direction of the light beam: radiation pressure.
  • A hot stove cools because the atoms of the fuel are jiggling around around and their charges are oscillating. These oscillating charges radiate light, which takes away energy.
  • 44-6 (Bottom) Echos of Deutsch. "So we see that a substance's properties must be limited in a certian way; one cannot make up anything he want, or he would be able to invent a substance which he could use to produce more than the maximum allowable work when he carried it around a revesible cycle. This principle, this limitation, is the only real rule that comes out of thermodynamics"
  • Nice way to see how the wave reflected from a fixed end of a string is inverted. The image wave travelling in the other direction has to be inverted to cancel at x=0.

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