If velocity is relative and if we cannot say which is moving away from what *objectivley, how do we say that time dilation is relative as well if we can tell who experienced the time dilation, as special relativity shows - and other experiments (muon concentrations etc). For example the jets clock is proven to run slower (and not the clock on the platform, in relation to the jet), gps atomic clocks are corrected for SR effects etc---these seem to me to argue that we do know which objects are undergoing time dilation not in a relative sense. Do experiments like the jet clocks or gps statellite clocks or muon concentration experiments get around the frame change symmetry breaking explanation any better? Does the frame change symmetry break per the twin experiment account for the reason why time dilation is relative and not objective and does this "frame change reason" account for why time dilation is relative for all other experiments (jet clocks, gps, muons)? I've heard some claim that time dilation is not relative bc we Know who will age less, (even if its after the fact and initially experienced as relative) and some say the twin paradox 'frame change' is not pertinent to how we understand the jet clock time dilation, gps satellite time dilation and high muon concentrations. thoughts?