522: Judging Age & Origins, part 1 - Earth Rocks Astronomy Cast 522: Judging Age & Origins, part 1 - Earth Rocks by Fraser Cain & Dr. Pamela Gay People always want to know how old everything is. And more specifically, they want to know how we know how old everything is. Well, here at Astronomy Cast, it's our job to tell you now only what we know, but how we know what we know. And today we'll begin a series on how we know how old everything is.