>There was a documentary at TV. He said "Milky Way and Andromeda will be merge and our Sun take earth in 4,5 billion years". My five years old daughter understood what means all off these things except what a long time is 4,5 billion years and beginned cry. I said her 4,5 billion years is very long but couldn't success... :)

Give her a very big hug and tell her you will protect her from anything with the nerve to mess with her.

When my older daughter was little she was convinced there was a monster hiding in her closet. I told her don't be silly, Allie, there is no such thing as monsters. She didn't believe me. I was told don't tell them there is no such thing because she won't believe you. I was told what they want to hear is that you will protect them from any monster foolish enough to come into their room. I said I will throw any monster through the window and into the street. "Into the street!" she said. It satisfied her. If you want uncertainty as a constant companion, have a kid.