Mach effect

The Mach effect can refer to:
 * Mach bands are an optical illusion that are often referred as "the Mach effect".
 * Mach's principle – a hypothesis attempting to explain a frame of reference for rotation
 * Mach effect or Mach effects (for spacecraft propulsion) – see Woodward effect
 * Mach-effect thruster – a hypothetical reactionless drive