He was 16, I was 15 and we were friends, two bored high-school boys on summer vacation. It was 1968. We were hanging around his mother's house, in the backyard, trying to think of something to do. A large cow pasture met the end of his back yard and a barbed-wire fence separated the two. I suggested we climb over the fence and wander around the pasture - maybe we would find something to do over there. He agreed. Soon, we were in the pasture. There were no cows there that day so walking around was safe. The farmer's house and barn were too far away to matter. It was a sunny day with a wide open sky. An animal had burrowed, leaving a few rocks exposed to the surface. I suggested that we have a rock-throwing contest. Who could throw the highest and the farthest? It was really no contest. I was scrawny and he was bigger and much more muscular. We each chose a rock that fit our throwing hand very well. I told him to go ahead and throw first. I wanted to see how high and far he could throw so I would know what I needed to beat. He pulled back his arm and threw the rock as hard as he could. It seemed to take no more than a second for the rock to climb about 20 feet high when there was a loud, metallic "CLANK!" and the rock did a dead fall from that point. We quickly turned towards each other with looks of panic and ran as fast as we could back to the barbed-wire fence, scrambled over it, sprinted into his mother's house and hid in the basement for two hours. There were no trees, telephone wires or anything else that we could see in the sky. I hadn't even thrown my rock yet. I will always wonder what invisible, metal thing that rock hit.