Professor Susskind answers a question about neutrino mixing and relates the oscillating quantum states of a neutrino to a precessing electron spin in a magnetic field. He then discusses a recent article about whether an electron is a sphere. After these topics, Professor Susskind continues the previous discussion about second quantization, and demonstrates that the position and momentum creation and annihilation operators are Fourier conjugates of each other. Topics: Neutrino mixing Second quantization Fourier conjugates