May 27, 1937 marked the initial celebrations of the opening of the Golden Gate Bridge, a project that was started in January of 1933 and cost more than 35 million dollars. (Source: Wikipedia)

A popular Magic School Bus episode involves making a bridge out of materials found in the bathroom in order to cross the bathtub, in which an alligator is lurking. DragonFly TV has on online episode called the "Bridge Building Club" which follows a middle-school team's efforts at designing and testing a balsa wood bridge.

Understanding bridge design and the structural principles involved starts young. Connected building blocks stacked vertically make a tower. But the same connected stack stretched side to side between two elevated objects creates a bridge. Getting started is easy. Making it structurally sound is more complicated. How wide can it be? Will it sag? Will it break apart? Can it bear weight?

For hands-on fun with bridges and an introduction to structural design, check out the following Science Buddies science fair project ideas:

• The Effect of Bridge Design on Weight Bearing Capacity (Science Buddies' difficulty level 4-6)
• Bridges That Can Take a Shake! (Science Buddies' difficulty level 2-3)
• Keeping You in Suspens(ion) (Science Buddies' difficulty level 5)
• The Design Process: Creating a Stronger Truss (Science Buddies' difficulty level 7)
• Fallen Arches: The Surprising Strength of Eggshells (Science Buddies' difficulty level 5)