1) briefly explain how we can use spectral lines to determine an object's radial motion. can we also learn the object's tangential motion (across our line of sight) from its spectral lines? 2) time dilation on the space station. the space station orbits earth at a speed of about 30,000 km/hr. while 1 hour passes on earth, how much time passes on the station? assume that both the station and earth are in free-float frames, although in reality they are not.