I had this article planned for a couple of days now. This was before we were informed of the terrible tragedy in Minnesota, where a bridge, over the Mississippi, collapsed. It is kind of a bizarre coincidence, but I decided to go ahead with it anyway. Bridges are important devices that have had a few different uses through the ages. The first and primary use was to allow people to cross over obstacles and get to the other side without having to risk life and limb or take a lot of time. These bridges were built over water and over things like valleys. Another use for bridges was to allow people to cross over fortifications that had been dug to protect buildings. Castles had bridges that went over moats. Bridges have even been built that connect two high buildings, allowing the occupants to cross from one building to the other without ever having to go down to the street. The idea for the bridge may have come from nature. Early man had to notice that a fallen tree might have spanned two cliffs or that a land bridge might have connected to large areas of land.

No one really knows when the very first bridge was constructed. The Persians built a bridge in 490 BC, it linked both sides of the Bosphorus. Darius, the emperor of Persia, commissioned it. So how was this bridge constructed? It resembled the pontoon bridges of today. It was constructed by linking boats together until the line of boats reached both shores. Darius was said to be very happy with this bridge and it enabled him to move his huge army from one side of the river to the other. It is suspected that bridges were built as early as 4,000 BC. Traces of them have been found in different parts of the world. It seems that they were most popular in the Mediterranean region. Any article about early bridges would be remiss if it didn't mention the great bridge that was built in about a week by Julius Ceaser, that crossed the Rhine river. Caesar decided to give a show of strength to the German tribes. He had about 35,000 men and they had amassed about 200,000. The Rhine river stood in his way. He ordered his engineers to build a bridge across it. As they started to do so, the Germans were awe struck, they had never seen anything like this before. As it came closer and closer to their shore, they began to panic. By the time it reached them, they decided to run. Caesar and his men pranced all over the land for weeks and were never attacked. Finally the Romans decided to leave and crossed the bridge, ripping it up as they went. This bridge was truly one of the marvels of ancient times. There is no way that we could duplicate this feat in the same time today.

The Romans were perhaps the most prolific builders the ancient world has ever known. They were also very capable builders and many of their structures still stand, after thousands of years, all over the world. They adopted the engineering knowledge of all the other civilizations that came before them and applied it to their building techniques. If one was to examine some old Roman structures in detail, they would find that some of the methods used in construction were the same as the ones we use today. A magnificent remnant of a bridge in Rome is the Ponte Rotto. It was built about 193 BC. It is now but a section of a bridge. The piers in the Tiber are left with the section of road above them. It is obvious what a great structure this must have been. It is so sturdy that it might just outlast its modern counter parts that were built next to it.

London Bridge

Today there are bridges all over the planet. Unfortunately some of them are not maintained as well as they should be. This is true even for this county's bridges, as witnessed by the recent bridge collapse in Minnesota. That was a bridge that wasn't inspected in the last couple of years. Bridges have to be inspected and maintenance performed at least every year to make sure that any damage is spotted and repaired before it turns into real problem that could threaten the structure.

The highest bridge in the world is in southern France, it is the Millau Vladuct. The highest point the bridge reaches is 1,118 feet, Ouch! You almost need oxygen crossing it. That was a bit of an exaggeration, but I think that you get the point. The world's longest bridges are measured without the ground support. The longest bridge in the world is, drum roll please, Lake Pontchartrain Causeway being 126,024 feet long (38,422 meters). This is followed closely by the Manchac Swamp bridge of I-55 which is 120,400 feet long (36,710 meters). There are different categories under the longest bridges, but I went for THE LONGEST BRIDGE regardless of category. I guess if I were to ask what was the world's shortest bridge it would be a plank across a puddle. The longest Roman bridge was Trajan's Bridge. It spanned the Danube and stood for over 1,000 years. I guess bridge makers today could learn a thing or two from its remarkable longevity. It was 1,135 meters long and 15 meters wide and 19 meters high. It was built by Apollodorus of Damascus and used wooden arches set on pillars made of masonry. They were constructed with bricks, mortar and pozzolana cement. This large bridge was started in 103 AD and finished in 105 AD. This has a lot of people puzzled. How did the Romans build such a large bridge in such a short period of time? It is thought that maybe they diverted the river while bridge construction took place.

Golden Gate Bridge

Today, new ways of spanning obstacles are being thought up. We certainly still use bridges, but the way we construct some of them and the materials used are sometimes different than those traditional materials that we have become used to hearing about in bridge construction. Engineers are using things like light weight materials and in one case even cardboard to make bridges. A new system of support has been employed on some bridges, where cables are fed from the center of the bridge and don't go all the way to the ends. As new materials are being discovered, bridge construction may even change more. We seem to be finding more stronger and lighter materials every year. Can you imagine a bridge constructed of a material made entirely of nanotubes? Don't laugh, it could happen and who knows, it might even be in the works already.

So why did that bridge in Minnesota collapse? The bridge was rated as structurally deficient a few years ago, but you all know how slow government is to fix anything. What had happened was that the joints and bearings were corroded and finally gave way under the stress of traffic. Ironically, the bridge was being repaired when it collapsed. It has been said that about 8% of all Minnesota's bridges have been rated as structurally deficient. I guess that a program will be put into effect now to repair them, but I can't be sure.