MUMMIES, DINOSAURS, MOON ROCKS

Subtitling their work ``How We Know How Old Things Are,'' the authors write with enthusiasm and include up-to-date information about ``many ways of finding the age of objects ranging from the relatively young—like pottery and old musical instruments—to fossils and the earth itself.'' Each method is put in the context of current and evolving scientific puzzles that will appeal to young readers: Methods include Carbon 14 dating, thermoluminescence, potassium-argon dating, dendrochronology, analysis of DNA, etc. Examples are wide ranging and intriguing, e.g., where did Columbus land that Christmas of 1492 and establish La Navidad? Scientists analyzed the strontium atoms in a pig's tooth found on one site and determined that it probably came from Spain close to the port from which Columbus sailed. In other stories, the scientists separate human blood from pigment in cave paintings to learn more about the artists or employ a process known as a polymerase chain reaction to look for genes in Neanderthal blood. Like a good detective story, the book will hook even casual readers, who will be subsequently enthralled. (b&w photos, diagrams, glossary, further reading, index) (Nonfiction. 10+)