I have seen a video in which the time dilation due to velocity is explained by saying that light and light interactions inside a moving body must travel a longer distance in space, which reduces the passage of time. Video: This explanation is new to me, and in fact, I recently heard an almost identical one a few months ago. Til now I have always considered that time itself was affected by speed, and that what is described above was more a consequence (effect) than a cause. As most, they would be equivalent. I am suspecting that this kind of explanation comes from some relatively recent book or other science divulgation media, which has popularized this view. I have these objections to that explanation, and because I am too used to the usual, conventional, explanation, would be very glad that someone can correct me if I am wrong in some of my objections. My objections are these: Time dilation is a consequence coming directly from the 2 postulates. Lorentz transformations apply and we have time dilation, which affects directly to rate of clocks. Time is "going slower" (time dilation) for the moving object, i. e., the proper time of the (moving) ship is shortened respect to (rest) Earth. In the explanation due to speed interactions (video and similar ones), it is assumed that there exists a maximum speed, that this speed is that of light, and that time emerges from this maximum speed, so for particles distant each other, and moving, it will take a longer time to communicate, and the passage of time will be lesser for these particles. Also that all sorts of interactions, even subatomic, will attain to this speed. All the assumptions in point 3 are derived from the result of c = maximum speed, which comes from Lorentz transf. if we start with the 2 postulates, so indeed we are already stating that time dilation applies (circularity). For a muon, and its spontaneous radioactive decay, being a point particle and the decay a stochastic quantum process, the explanation of maximum speed would not seem to apply and would not explain the dilatation which allows them to travel through the entire atmosphere of the Earth. Time dilation explains it. As for transveral Doppler effect, I am not sure if the interpretation of maximum speed of light would explain it, but slower time passage does, directly (this I am not sure). My sensation with this explanation is that it is closer to the Lorentzian interpretation of relativity, rather than actual Einstenian relativity. Suggestions are appreciated.