Oh boy, let me tell you about one of my favorite fails in history. One of the most memorable failures in history happened during the final siege of Tenochtitlan in 1521. The Spanish were eager to find a way to attack the Mexica positions. Antonio de Sotelo, a soldier who said he knew a lot about military machines, persuaded Hernán Cortés to build a huge stone-throwing catapult.
Sotelo and the carpenters spent several days building the machine with timber, stone, lime, and heavy ropes. The Spaniards set it up on a platform in Tlatelolco as Mexica defenders watched from the rooftops nearby. When they finally loaded a large stone and let it go, the rock flew almost straight up into the air.
Instead of hitting the Mexica positions, the stone fell straight back down onto the machine. Bernal Díaz del Castillo wrote that the impact destroyed the device. The Mexica account in the Florentine Codex also describes the failed test, saying the stone landed far from the target and the Spaniards quickly started arguing with each other.
History has plenty of famous mistakes. One example is the Leaning Tower of Pisa, which started having problems almost right away. Construction began in 1173, and the tower began to tilt before the third floor was even finished.
The problem was the ground itself. The soft, compressible soil could not hold up such a large building, but work on the tower still went on for generations.
Eventually, the tower leaned so much that it was in real danger of falling. Engineers later discovered that the ground under the foundation was the main cause. In modern times, experts reduced the tilt a bit by taking out small amounts of soil under the foundation instead of rebuilding the whole tower.
Not every problem comes down to engineering. When Christopher Columbus crossed the Atlantic, he thought Asia was much closer than it really was. He based his calculations partly on Ptolemy’s geography, which made Earth seem smaller, and he also used the wrong length for the miles on his maps.
These mistakes made the trip west seem much shorter than it was. So when Columbus reached the Caribbean, he believed he was somewhere near Asia.
A surviving map from 1491 shows the kind of geographic assumptions people made at the time. It placed Japan much too close to Asia. Columbus did not have a map of the Americas, since European mapmakers did not know about them yet.
Our mistakes have even reached space. The Space Shuttle Challenger was built on years of engineering, but a small part in one of its solid rocket boosters ended up causing the disaster.
The O-ring seal could not handle the unusually cold weather at launch, so hot gases leaked through the joint. This damage led to the shuttle breaking apart soon after takeoff.
This disaster revealed issues that went beyond just the hardware. NASA and contractor managers had noticed O-ring erosion on earlier flights, but over time, they began to see it as an acceptable risk. Poor communication also meant that decision-makers did not have all the information about the engineering concerns before the launch.
Sometimes people really do miss things that are right in front of them. Researchers call this inattentional blindness. In the well-known “invisible gorilla” experiment, about half the people who were busy counting basketball passes did not notice someone in a gorilla suit walking through the scene.
This effect is not just about some people paying less attention than others. The task itself is important. When people focus on one thing, they can miss unexpected events happening around them.
That is why an obvious mistake can go unnoticed by several people, even if no one is trying to ignore it.
Even when people spot a problem and warn others, things can still go very wrong. Some engineers were already concerned about the Tacoma Narrows Bridge before it collapsed in 1940. Professor F. B. Farquharson studied how the bridge moved and warned that a certain twisting motion could destroy it.
Despite the warnings, the project continued. A federal field engineer later refused to recommend accepting the finished bridge because of design concerns, but the authorities accepted it anyway. On November 7, strong winds caused the twisting motion engineers had feared, and the 600-foot center span eventually broke apart.
And what about the most expensive “Oops” in history? Boston’s Big Dig started with a $2.6 billion budget and was supposed to finish in 1998. In the end, the project cost about $14.6 billion and ran years past its original deadline.
This huge project replaced an old elevated highway with tunnels, and engineers also had to link major roads and transportation centers. The high cost was not due to a single big error.
About $6.5 billion of the $12 billion increase was due to inflation. The project also struggled with management and contract administration issues. The National Academies pointed out that the original estimates were intentionally optimistic, which made a tough engineering project even more expensive.
