Write4U; In the graphic, the vertical distance is the x axis, with the ground G at the origin and M the muon frame, and ct the time axis. M approaches the ground at .95c, reaching it at Gt=t1. Applying time dilation (red), the corresponding time Mt=t'=t. The interval (0-t) is projected onto the time axis for M to the right. Postulate 1 states the physics is the same in all inertial frames, thus if d muons decay in the interval (0-t) on the ground, the same number decay for the total time interval for M. More decay in the interval (t-t1) on the ground, so there are fewer muons on the ground than arriving from altitude. The lower right corner is the description by an observer moving with the muons, with a time of t' and a distance of MG', a world scaled by 1/gamma, approx. (.31). Please Register or Log in to view the hidden image!