Jimmy Randle, age 10, of High Point, North Carolina, for his question:

What does the X in X ray mean?

The letter X is the math symbol for something unknown. In a math equation, it is the secret you want to solve. The other items in the equation are symbols for things you already know. It is lined up as a sort of detective game. You use your reasoning powers to compare all the items and if you succeed, the items you know reveal the secret of the mysterious X. Nobody knew that X rays existed until 1895, when your great grandparents were children. They were discovered by Wilhelm Konrad Roentgen. He knew that these powerful, invisible rays could take photographs of bones hidden inside the body. But he did not know what this mysterious energy was. So he called it X rays. Scientists soon found out what it is and named it roentgen rays, in honor of the man who discovered it. This up to date term is pronounced runt gun rays.