Dirt is still being produced all the time, albeit in much lesser quantities. Beneath the soil's surface, rocks constantly react with rainwater or groundwater and slowly grind together to break down into smaller minerals. So in that respect, dirt really isn't that old. Then again, Pavich notes, a lot of what came out of the big bang was essentially dust, which then condensed to form the stars and, later on, planets. "If you think about it," he says, "dirt and its origin are older than the stars."