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Cuban Missile Crisis -

The closest the world has ever come to nuclear war was in 1962, during what is now known as the Cuban Missile Crisis. Just three people, John F. Kennedy, Nikita Khrushchev, and Fidel Castro, held the fate of humanity in their hands.

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Cuban Missile Crisis -

When the USSR began building missile silos and transporting materials to their ally Cuba, the United States saw this as a direct provocation of war, and the parties involved became stuck in a nuclear standoff that forced the world to hold its breath for 13 days, until Khrushchev agreed to back out of his Cuban missile program.

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NORAD training mix-up -

NORAD (North American Aerospace Defense Command) dropped the ball in 1979, when a nuclear attack training tape was perceived as a real attack. Thankfully, there was a fair amount of skepticism involving the legitimacy of the warnings, and no counteraction was taken until the alarms were proven false.

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4581 Asclepius -

There have been more than a couple of close calls involving stellar objects hurtling dangerously close to Earth. One such scare came in 1981, when the asteroid 4581 Asclepius whizzed by our planet. If the asteroid was just six hours earlier, it would have collided with Earth, with an impact 12 times stronger than a nuclear bomb.

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Toba Supervolcano -

One of the largest volcanic eruptions in history, the Toba Supervolcano in present-day Indonesia covered around 4,350 miles (7,000 km) of Southeast Asia in ash some 47,000 years ago, and spewed out 700 cubic miles (2,800 cubic km) of magma.

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Toba Supervolcano -

Around the same time as the eruption, human life in the area dramatically decreased and was almost entirely wiped out. This was truly an apocalyptic event for the ancient peoples in the region. Today, the massive caldera of the volcano is filled with water and is referred to as Lake Toba (pictured).

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A fumbled hydrogen bomb -

On an average day in New Mexico in 1957, a plane transporting what was at the time the largest hydrogen bomb in existence, dropped that bomb by accident just outside of Albuquerque. The 42,000-pound (19,050-kg) bomb, by sheer luck, landed in a completely unpopulated area and didn't harm a soul, although it did leave a crater in the desert 12 feet (3.7 m) deep and 25 feet (7.6 m) wide.

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2012 solar storm -

The Sun may seem incomprehensibly far away, but its own stellar events can have serious implications here on Earth. In 2012, for example, power grids and communication networks around the globe were almost completely destroyed by a solar storm flare that missed Earth by only a week.

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The comet that killed the dinosaurs -

Known as the Cretaceous-Tertiary mass extinction, the comet that collided with Earth some 65 million years ago obliterated almost every sign of life on our planet. The fact that some small mammals and underwater critters were spared and able to repopulate the Earth is one of biological history's great strokes of luck.

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Smallpox -

One of the most dangerous and resilient diseases in history, smallpox has dealt serious and almost irreparable damage to Earth's population on numerous occasions. Thankfully, an effective vaccine program was rolled out in the 20th century before the sinister sickness was given another chance.

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NORAD strikes again -

During the Cold War, NORAD had a bit of a history of silly, potentially apocalyptic mistakes. In 1980, a microchip happened to bug out and falsely indicated that the USSR had sent no less than 220 nukes in the direction of the United States. President Jimmy Carter was only moments away from being advised to call a counterattack before the bug was found.

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The Black Death -

An infamous and gruesome sickness that wiped out 60% of the European population in the 1300s, the Black Death set back civilization by an inestimable number of decades or even centuries, and could have easily brought an end to European civilization as we know it.

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The Carrington Event -

During a solar storm similar to the one that caused the scare in 2012, in 1859 a solar flare really did knock out global communications. Thankfully, entire governments, bank accounts, and livelihoods didn't depend on electricity the way they do today, but the collapse of the telegram system was relatively catastrophic for its time.

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Mount Tambora eruption -

The most destructive volcanic event in modern history, the 1815 eruption of Indonesia's Mount Tambora caused mass death, crop failures, and sudden and severe climate change.

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Mount Tambora eruption -

The entire globe was covered by the ash that was spread by this eruption. The Sun was completely blacked out for multiple days in Indonesia, and six feet (1.5 m) of ash covered the ground. It is estimated that more than 100,000 people died from the eruption, directly or indirectly.

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Chelyabinsk meteor -

Many might remember the feeling of terror when the Chelyabinsk meteor crashed in Southeastern Russia in 2013. The meteor's size and velocity gave it a power equal to that of an atomic bomb, and it could have easily razed a city to the ground had it landed in a more populated area.

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Idaho Falls explosion -

The Idaho Falls explosion of 1961 could have proven catastrophic for Idaho, potentially equating to a North American Chernobyl. After mistakes were made during the removal of a control rod, the Idaho Falls nuclear plant collapsed and could have caused widespread destruction were it not quickly and properly dealt with.

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NORAD's mistaken message -

One of the numerous terrifying mistakes made by NORAD during the Cold War occurred in 1971, when an Air Force base accidentally sent out an emergency communications message that confirmed that it was not a drill. Reporters and radio listeners held their breath for around five minutes waiting for the news that the entire nation had been fearing for years, until it was made apparent that NORAD officers had sent the wrong recording to radio stations and that it was, in fact, a routine drill.

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Chernobyl disaster -

One of the most terrifying nuclear collapses in history, and certainly the most infamous, was the Chernobyl disaster of 1986. After the collapse of one of the site's main reactors, astounding levels of radiation were released into the surrounding area.

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Chernobyl disaster -

The meltdown made a ghost town of nearby Pripyat nearly overnight, a city that is still too radioactive to inhabit to this day. The Chernobyl reactor itself has been relegated to a massive concrete sarcophagus that will stay in place for the next century.

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The Bollina observation -

The comets observed by Mexican amateur astronomer Jose Bollina were of no great importance at the time, but further studies of the 450-strong meteor shower revealed that these objects were in fact dangerously close to Earth, possibly missing our planet by just a few hours.

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Norwegian rocket incident -

Rockets aren't always fired with violence in mind, but you'd be forgiven for assuming they were. In 1995, Norway launched an experimental rocket in order to study the Northern Lights. When Russian scanners picked up the rocket, they perceived it as an act of war, and were dangerously close to retaliating and starting World War III before the truth was revealed.

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Able Archer 83 -

War games were common around the world during the Cold War in order to keep the various militaries in top shape. Sometimes, however, these practice exercises were misunderstood, and brought the superpowers to the brink of World War III. This is exactly what occurred during NATO's Able Archer 83 exercises, which the USSR thought to be a legitimate preparation for war. The world almost ended over a simple misunderstanding before the training program ended.

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Klebsiella planticola -

Back in the 1990s, scientists came dangerously close to wiping out all agriculture on the European continent. A German GMO manufacturer was just about to release a new organism, Klebsiella planticola, before a third-party study discovered that the product would quickly and efficiently decimate any and all crops it came in contact with. If Klebsiella planticola ever reached the market, it could have caused the worst famine humanity has ever seen.

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Shaanxi earthquake -

One of the most devastating earthquakes in recorded history occurred in 1556 in the Shaanxi province of China. An estimated 830,000 people died in the disaster, surely setting the area's development back by decades upon decades.

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Hyakutake Comet -

The Great Comet of 1996, also named the Hyakutake Comet after the astronomer who discovered it, Yuji Hyakutake, is the closest a comet has come to Earth in two centuries.

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Flooding of the Yangtze 1931 -

When China's most important water formation, the Yangtze River, flooded in 1931, the consequences proved catastrophic and could have easily caused a local societal collapse. No less than 3.7 million people died from the flooding and the widespread crop failures it caused.

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Spanish Flu -

More lethal than World War I, more deadly than even the Black Plague, the Spanish Flu of the early 20th century claimed the lives of as many as 40 million people. Had it not been stopped, it would have continued to decimate the global population.

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Soviet nuke scare -

During the Cold War, the USSR had its own fair share of false alarms. A glitch in Soviet radar technology sent warnings of a full-scale nuclear assault initiated by the Americans. The technician on shift at the time, Stanislav Petrov (pictured), trusted his instincts that something wasn't quite right, and chose not to alert his higher-ups, who surely wouldn't have wasted time ordering a counterattack.

Sources: (Gizmodo) (List25) (Genetic Literacy Project)

See also: The most famous resignations in history

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