A person I work with is a creationist. At least, I think he is. He believes the Earth is less than 10,000 years old, but had no idea why until I told him why he was supposed to believe that. He is excruciatingly ignorant of why he believes what he does. Time after time he'll say something silly like this and I'll correct him. After some back and forth, it almost always comes down to me telling him what his reasons should be for believing in incorrect information. This is like playing chess against myself.
Yesterday, we got to discussing the age of the Earth. As I stated above, he said the earth is less than 10,000 years old. I brought out radioactive dating, varves, tree rings, petroleum, stalactites, and the Grand Canyon. Then I had to explain what radioactivity was, what a varve was, why tree rings are usefull, and how petroleum forms. He dismissed the radioactive information because I have no way to show him other than from books. Varves are out because he doesn't believe, and I can't show, how 20 million of them were counted at the Green River Formation. For tree rings, he said it took 10-15 years for the first ring to form to which I replied that for a 2,000 year old tree, this was insignificant.
Here is what I would like to know. What evidence can I present that requires no telescopes, no microscopes, no radioactivity, no travel, nothing. Just everday examples of the age of the Earth that will convince someone who is practically 100% ignorant of science. I need examples that require zero reliance on authority, especially the authority of any book other than the Bible. Thank you.