Hi all. I've been thinking of how one can measure the speed (& indirectly velocity, since we know it's direction of travel) of an object. The object is not necessarily an airplane or an automobile since they've their special devices built for velocity measurement. I was thinking of measuring my speed while me running a few miles or velocity of a ping-pong ball thrown in a particular direction. Can we build a device for measuring speeds of these objects? Or are there already devices for measuring speeds of arbitrary objects? Cheers.