It's all in the shape. Whether you want to crush, bend, twist, or slice an object, its shape is as important to its strength as what it's made of. Although an eggshell may be quite fragile, the shape of an egg gives it tremendous strength.

You can easily see the importance of shape if you build different bridges out of cardboard. For example, take two strips of cardboard, place one on top of the other, and lay them across the top of two equal piles of books. This bridge will barely support an empty jar.

You can greatly strengthen the bridge, however, if you take the lower strip and bend it into an arch, with its two ends braced against the bottom of the book piles and its top pressing against the other strip of cardboard.

This new structure will easily support a jar filled with sand or water.

The arch is one of the strongest structures known for supporting a load. The dome, which is just a three dimensional arch, is often used to cover extra large buildings, such as sports stadiums. The dome shape carries the weight of the roof evenly through its curved walls to the broad base, so that no single point on the dome supports the whole load. This shape has the advantage of not needing pillars to support the roof. Pillars would get in the way of people's view.

Does the shape of the dome remind you of anything? An egg has the shape of two domes put together which is why it's so strong.

© 1997, Canadian Broadcasting Corporation