h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

I was listening to 'Excess Baggage' (Rasio 4, Saturday 20th August). Jamie Andrew, a mountaineer and writer, was being interviewed. He has worked on various maintenance and construction projects and, nine years ago, worked on the Forth Bridge. He was saying that it was possible to walk inside the girders from one end of the bridge to the other. The interviewer asked him whether he was ever aware of the water beneath. He said that, on one occasion, he came to a two-inch diameter hole which was for drainage purposes, and there were shimmering patterns on the 'roof' caused by the riuppling water. Then, to his amazement, the image o a ship sailed across the ceiling - the hole was acting as a pinhole camera