...Spaceship earth has had velocity since the beginning, and the effects on the progress of time and measured distance is dependent on *changes* in that velocity. Such changes throughout history are completely unknown, but velocity is known to be changing. This has significant impact on the credibility of radio-isotope dating. The calculated "age" is a time-extrapolation which assumes zero or constant velocity over the calculated time -- which we know is an invalid assumption, except, perhaps, over extremely limited time durations. Thus, radio-isotope dating is helpful in producing "relative" age of things (which things came before or after other things), but is entirely inconclusive when it comes to establishing an absolute age.