Practicing Lorentz transformations but still not absolutely clear about conditions for observer's frame of reference. For example:
Suppose that just as one of Einstein's long and surreally fast trains is passing a station platform, lightning strikes the platform at two points making scorch...
George's workthrough (#5) to 38.7us/day is impressive. It is sometimes said that if that figure were not taken into account, the position indicated by a GPS user device would drift by about 11km/day but I've never seen an accompanying explanation. Multiplying 38us/day by the speed of light...