The Water Cycle
Run and get a glass of water and put it on the table next to you. Take a good long look at the water. Now -- can you guess how old it is?
The water in your glass may have fallen from the sky as rain just last week, but the water itself has been around pretty much as long as the earth has!
When the first fish crawled out of the ocean onto the land, your glass of water was part of that ocean. When the Brontosaurus walked through lakes feeding on plants, your glass of water was part of those lakes. When kings and princesses, knights and squires took a drink from their wells, your glass of water was part of those wells.