Good day, I was playing a bit with a Doppler effect scenario and tried to combine it a bit with Special Relativity and I concluded something that I don’t quite understand, or that I at least don’t get the meaning of. I am aware that the scenario and my concluded formula don’t describe the full Relativistic Doppler effect but the result got me interested. The scenario is the following: Person A is moving away from Person B. Person B is holding a lasergun that emits a specific frequency of light pulses towards A. Because of Special Relativity, Person A who is moving away would still measure the light pulses approaching him at c and he would think that Person B with the lasergun is moving away from him instead. From the Doppler asymmetry, Person A would therefore conclude that the time duration t between each light pulse that he’d receive is calculated by: P x (1 + v/c) = t (Lightsource moving away) In which P is de original time period between the light pulses (1 / f) that Person B is shooting. However, Person B with the lasergun measures the light pulses going away from him at c and think that Person A is moving away from him. From the Doppler asymmetry, he’d think that person A would measure a time duration t’ between his light pulses which is calculated by: P / (1- v/c) = t’ (Observer is moving away) Out of curiosity, I then wanted to calculate the factor by which t and t’ are separated by calculating the ratio of these 2 formulas: This simplifies to: What got me surprised, is that this concluded ratio of t’ and t is equal to the Lorentz factor squared. However, I don’t get exactly why this is the case. Is this just coincidence or does it have a meaning and if so, what’s the meaning behind it? From what I understand, time dilation between 2 observers should be always separated merely by the Lorentz factor, not the square of it. I’m very new to this so could someone please enlighten me on this in a simple way?