• Virtually all of physics deals with fields.
    • Ex: electric and magnetic fields, gravitational and other force fields, wave functions, etc
  • A field is something with data that varies from point to point
    • There are scalar fields that vary point to point
      • Ex: temperature of pressure distributions
    • Fields like the Newtonian gravitation field are best described by vector fields, which associate a vector to each point
      • Others, like the electromagnetic field and charge distributions are best modeled by form fields
      • Some others, like the Einstein field of general relativity, are none of the above
  • Definition: Vector Field. A vector field on is a function whose input is a point in and whose output is a vector (also in ) emanating from that point.

  • Vector fields are distinct from functions that return points
    • The identity function in , takes a point in and returns the same point. But the vector field takes a point in and assigns it to a vector starting at that point.
  • Vector fields are often used to describe the flow of fluids or gases; the vector assigned to each point describes the direction and velocity of the gas at a given point