Shive Wave Machine
A row of horizontal rods connected by a torsion spine. Drag the left end to send a pulse, then watch it propagate, reflect, and superpose. The boundary conditions change everything.
The Shive wave machine
John Shive built the original wave machine at Bell Labs in the 1960s. It consists of horizontal rods welded to a central torsion wire. When you twist one rod, the disturbance propagates through the wire from rod to rod — a mechanical wave you can see in slow motion.
Boundary conditions
A fixed end reflects the wave with inversion — a crest returns as a trough. A free end reflects without inversion — a crest returns as a crest. This is fundamental to how standing waves form in strings, pipes, and quantum wells.
Superposition
When two waves meet, their displacements add. Two pulses can pass through each other, momentarily canceling or doubling, then continue unchanged. This is the superposition principle.