We did an experiment about the strength of eggshells. We cracked two eggs and placed them upside down on the counter. Then we added books to see how many the eggshells would hold up before cracking. We got up to 9 normal sized books. (Tera had a lot of faith because the first one she brought in was the Merriam Children's Dictionary.) We had her take that one back and we started with a few paperbacks then added hard back readers. Finally they cracked. We talked about how the dome shape gave it the strength because it equally distributes the weight. We talked about how architects also use the dome shape in buildings because of that very reason.
(I'm manic blogging right now so hopefully I'm not overwhelming the few people who follow my blog)