(Lecture: 10 minutes)

• Acceleration behaves like Gravity
  • linear acceleration
  • down isn't down
• Curvature matters
  • East isn't East
• Space + Time = Spacetime
  • energy + momentum = 4-momentum
  • charge + current = 4-current
  • scalar potential + vector potential = 4-potential
  • electric field + magnetic field = electromagetic field tensor