The relativistic Doppler effect: when a zero frequency shift or a red shift exists for sources approaching the observer

摘要

It is shown without making use of Lorentz transformation that there exists aphenomenon of relativistic zero-frequency shift in Doppler effect for a planewave in free space, observed in two inertial frames of relative motion, and thezero shift takes place at a maximum aberration of light. When it is applied toanalysis of a moving point light source, two unconventional physicalimplications result: (1) a light source, when it is approaching (moving closerto) the observer, may cause a red shift; (2) a zero-frequency-shift observationdoes not necessarily mean that the light source is not moving closer, and incontrast, the light source may be moving closer to the observer at a highspeed. This fundamental result of special relativity may provide an alternativeway to experimentally examine the principle of relativity, and might have asignificant application in astrophysics.