Egg-speriment. (Hands-On Science).

The male bower bird knows how to build a sturdy home. He builds his nest with an arched doorway because an arch is one of nature's strongest shapes. When weight is placed on top of an arch, the force that the weight creates doesn't push straight down, but instead is carried outward along the curve of the arch. An eggshell may seem fragile, but its arched shape makes it deceptively strong. Discover the mighty egg in action!

YOU NEED:

4 raw eggs * modeling clay * phone books or other heavy books * a board large enough to hold the books (such as a large, thin chopping block)

* aluminum roasting pan

* scale

TO DO:

1. Shape the modeling clay into "cushions" for the eggs. Divide the clay into eight round balls. Then flatten the balls into small disks. Use your thumb to make an indentation in the center of each disk.

2. Place one cushion on the top and one cushion on the bottom of each egg.

3. Place the eggs in the pan, pointed side up. Space them so that each egg will support one corner of the board. Gently place the board on top of the eggs.

4. For the next part of the experiment you'll stack books on top of the board. But before you begin, predict how many books and how many kilograms (or pounds) the eggs will hold. If this is a group experiment, survey your classmates.

5. Place books on the board, one at a time. Center them in the middle of the board. Continue adding phone books until at least one of the eggs breaks.

CONCLUSIONS:

How many books did the eggs support? Also, weigh the books. Is this more or less than you expected? Why are the eggs so strong?

DON'T STOP NOW!

Look at the buildings, bridges, and other structures around you. Where do you see arches? What do they support? Explore the strength of other shapes. Is there another shape that's particularly strong?