Happy Bridge Day!

They help us almost every day, either when you drive to work, to school, or just to visit your grandparents. You're right, it’s Bridge Day!

We use bridges to get over rivers, exit or enter highways, or for some other use. But have you ever thought about how bridges work, and what's Bridge Day?

Bridges are basically ramps for cars, bikes, trucks, trains, etc, though one thing they fear most is: Gravity, the force that pulls things toward Earth.

Bridges need to have these two forces to stay above ground: Compression, a force which squeezes inward, and tension, which is the opposite. There are two important kinds of bridges, suspension and arch bridges.

Suspension bridges are in compression, while the deck hangs on cables that are in tension. One example is the Golden Gate Bridge.

Arch bridges distribute compression down the arch, while the structure is pushing in on itself.

Bridge Day, which is on the third Saturday in Oct, today, was created in 1980 to commemorate the completion of an arch bridge, the New River Gorge Bridge.