A null experiment shows that superluminal group velocity of tunneling photons is not superluminal energy flow because it is not sensitive to Earth's absolute motion

A method for showing that superluminal group velocity, associated with tunneling photons, is not superluminal energy flow, is to measure possible preferred frame effects. In Lorentz invariant theories, causal superluminal energy propagation in one reference frame is acausal in other frames. But Lorentz-violating theories have a preferred frame in which causal evolution is defined and superluminal propagation becomes causal in all reference frames. Null measurements show that preferred frame effects do not exist relative to a CMB rest frame velocity of about 370 km/s.