Incredible But True Incredible But True Human World History Makers Cities Of The World Art And Music Sporting Headlines Plant Life Fish, Amphibians, Reptiles Birds and Mammals Creepy Crawlies Marine Life Restless Earth Earth's Secrets Changing Weather Seas And Oceans Comparisons Amazing Structures Machines And Man World Of Inventions Travelling Around Mysterious Universe	Time-keeping Wizard The world's most accurate timekeeper is an atomic clock produced in the USA. About the size of a desktop computer, it is accurate to 1 second in 1.6 million years.   Previous: Back Book: Incredible But True Section: Incredible But True Chapter: Machines And Man