Due to the principle of relativity two observers moving relative to each other will each measure the other to be time dilated. But, as in the twin paradox , if they meet they will find that time passed slower for one of the two (let's skip over the experimental challenges inherent to conveying this information for the moment). The Earth is moving relative to a lot of different celestial bodies. Is there an inertial reference frame whose clocks are ticking faster than ours? Ie. is time dilation isotopic?