Charts, Diagrams and Timelines

What a Coral Reef Is

A coral reef looks like rock and is built by animals. A coral polyp is a soft creature the size of a pinhead. It draws calcium from the sea water and builds a hard cup around itself. Millions of polyps, cup upon cup, become a reef. Inside each polyp live tiny algae. The algae make food from sunlight and pass most of it to the polyp. In exchange they get shelter and the polyp's waste. Neither could build a reef alone. When the water gets too warm, the polyps expel the algae. Without them the coral turns white and starves. That is what bleaching means. A reef takes centuries to build and can bleach in a single hot summer.

The Accidental Photograph

In 1895 Wilhelm Röntgen was working with a covered tube in a darkened room when he noticed a screen across the laboratory glowing. Something was passing through the cover and crossing the room. He did not know what it was, so he called it X — the unknown. He spent seven weeks alone in the laboratory testing it. He put wood, rubber and metal in the way. Metal stopped it; the rest did not. Then he asked his wife to put her hand between the tube and a photographic plate. The picture showed the bones of her hand and her wedding ring. Within a year, X-rays were being used in hospitals. Röntgen refused to patent them.