Some nuclear waste products will remain radioactive for 24,000 years—long after our civilization is forgotten. When the U.S. Department of Energy applied for permission to build a depository at Yucca...

Some nuclear waste products will remain radioactive for 24,000 years—long after our civilization is forgotten. When the U.S. Department of Energy applied for permission to build a depository at Yucca Mountain, Nevada, they worried that future civilizations might be unaware that twenty-firstcentury Americans happened to bury radioactive materials there. How to warn them? Signs in English won’t work—what if no one can decipher the long-dead English language? They decided on markers using six languages and a variety of symbols. In case everything is unknown to our descendants, they made the markers look unpleasant and foreboding, to give people an instinctive feeling of dread. Unfortunately, they can’t be sure that what we find unpleasant will not be considered beautiful in 20,000 years—just consider the short time it took for polyester leisure suits to shift from hip to hideous.