Here's a fun interactive site that will give you an appreciation for how big and how small the universe and it's constituents are. Go to the link and move the scroll bar to zoom in or out to see how big the universe is compared to our planet and how big we are compared to the smallest parts of an atom.
Give it a try and spend a little time just being amazed. You won't be able to stop playing with it.
I recall reading somewhere that if the sizes of all objects in the universe are averaged together it turns out that the average size is exactly the size of human beings. I don't know if there's some significance to that or if it's just an interesting coincidence, so I'll leave it to you to mull over as you play with the scroll bar.
