Mistakes are a very common occurrence in both history and everyday lives. While some barely have any effect, some result in unexpected consequences. Sometimes, one person’s mistake could be another person’s luck, yet sometimes that mistake could mean a terrible blow to everyone. Most of the times we cannot foresee the future or how these unexpected events could unfold. It is not always possible to avoid mistakes and we can only learn from the consequences. But, at times they do happen. Here are some such “oops” moments in history.

1 Three lost cigars caused the Confederacy to lose the Civil War to the Union. A Union corporal discovered those cigars wrapped in a piece of paper which turned out to be a copy of lost Special Order 191 containing details of how Confederate troops would attack Washington.

The Special Order 191, also known as the “Lost Dispatch” or the “Lost Order,” was drafted on September 9, 1862, during the Maryland Campaign of the American Civil War and was issued by the Confederate Army General Robert E. Lee. Copies of the order were made and distributed to various Confederate officers. One of the copies went missing and on September 13, 1862, was found by a Corporal Barton W. Mitchell of the Union XII Corps. It was wrapped around three cigars at a site one of the Confederate Major Generals just vacated.

Upon realizing the significance of the document, it was immediately forwarded to Maj. Gen. George B. McClellan, the commander of the Army of the Potomac, who was delighted at now knowing the Confederate troops’ movements. McClellan stopped Lee’s invasion at the Battle of Antietam. (source)

2 The “Cluster,” a group of four European spacecraft, were lost when one of the rockets failed to achieve orbit due to a software design error. The rocket soon disintegrated under high aerodynamic forces making it one of the most infamous and expensive software bugs in history with a loss of $370 million.

The “Cluster” was designed for research into Earth’s magnetosphere and consisted of four 1,200 kilograms (2,600 pounds) cylindrical spacecraft which were meant to fly in a tetrahedron formation. The Cluster was launched on Ariane 5, a European heavy-lift launch vehicle, on June 4, 1996. However, 37 seconds after the launch, the rocket veered off its path and began to disintegrate under high aerodynamic forces. It then began self-destructing in accordance with its automated flight termination system.

While designing, the inertial reference platform used for the previous model Ariane 4 was used in Ariane 5 as well. But Ariane 5’s path differed from Ariane 4, and the speeds were far greater. During the investigation, a different inertial reference platform was used to simulate Ariane 5’s flight, and it was revealed that the rocket failed in exactly the same way it did in actual flight. It was also revealed that the greater horizontal acceleration caused a data conversion from 64-bit floating point to a 16-bit signed integer to overflow and result in hardware exception.(source)

3 In 1971, a team of Soviet engineers, fearing the spread of poisonous methane gas, set fire to a crater after a rig collapsed while drilling for natural gas reserves. That was more than 40 years ago and the gas is still burning to this day.

The Darvaza gas crater, also known as the “Door to Hell” or “Gates of Hell”, is a natural gas field located near the village of Derweze, Turkmenistan. The site was identified by Soviet engineers in 1971 and originally believed to contain a substantial amount of oil. While doing the preliminary survey, they drilled to find a natural gas pocket. Soon, the ground under the drilling rig collapsed into a wide crater. Fearing the release of poisonous gases into the nearby towns, they set fire to it expecting the gas to burn off in a few weeks. However, the crater is still afire with flames and boiling mud, and has a diameter of 70 meters (230 feet). (source)

4 The Chicago Daily Tribune was so sure Thomas E. Dewey would win the 1948 presidential election that they printed the next day’s edition with an incorrect headline: “Dewey Defeats Truman.” It was famously held up by Truman after he won the elections, smiling triumphantly at the error.

The year before the elections, the linotype machine printers were on strike. The Tribune switched to a method in which the papers were composed on typewriters, which were then photographed, and then engraved onto printing plates. This meant that the paper had to go to press several hours earlier. Due to the pressing deadlines during the election time, the Tribune relied on its veteran Washington correspondent and political analyst Arthur Sears Henning, who was right four out of five times before.

Assured by Henning’s prediction and the polls, the Tribune went to press with the headline: “Dewey Defeats Truman”. Henning further wrote that: “Dewey and Warren won a sweeping victory in the presidential election yesterday.”(source)

5 In 1999, NASA’s Mars Climate Observer came too close to Mars and burned up in its upper atmosphere because of unit conversion errors. One team at NASA used the metric system while a team at Lockheed Martin used the imperial system.

The Mars Climate Orbiter was a robotic space probe launched by NASA on December 11, 1998, to study the climate, atmosphere, and surface of Mars. The orbiter was built, developed, and operated by Lockheed Martin, an American aerospace company, for NASA. However, the navigation commands for the orbiter’s thrusters were provided by its engineers in the imperial system while NASA had been using the metric system since 1990.

After a 286-day journey, the orbiter finally reached Mars and the process of inserting it into an orbit began on September 23, 1999. The mismatch in the units caused it to go to an altitude of 57 kilometers. Eighty kilometers was considered a safe altitude and 226 kilometers was the intended altitude. At such a low altitude, it is believed to have disintegrated due to atmospheric stresses. (1, 2)