A student builds a simple circuit and a magnet under one of the circuit wires. When the switch is closed charges flow int the circuit and the wire moves

Magnetic field, current and motion are mutually dependent.

Explanation:

Fleming's right hand principle explains that when any two of current, magnetic field and motion are available, the third would be induced. These three variable are mutually perpendicular to one another. This principle has its application in an electric fan which induces the motion of the blades due to flow of current and magnetic field in the coil.

In the simple circuit, the interaction between the flow of charges (i.e current) and the magnetic fields of the permanent magnet induced the motion of the wire.

3. dark matter

empty space could also be a simple vacuum