Back in 1948, the journal Physical Review published a paper entitled “Space-Time Approach to Quantum Electrodynamics” by a young physicist named R.P. Feynman at Cornell University. The paper described ...

Cylindrical and spherical coordinates, double and triple integrals, line and surface integrals. Change of variables in multiple integrals; gradient, divergence, and ...

Alternate title: You Khan't Divide a Vector by a Vector. Get it? Maybe you don't, but that is ok. Really, I was going to make this a video critique of Sal Khan's – video critique of my video critique.

Corrected: This story has been updated to reflect Ralph Pantozzi’s full statement. Corrected: A previous version of this story misstated the location of Kent Place School. It is located in Summit, N.J ...