The Doomsday Clock provides a symbolic measurement of how close humanity is to its own annihilation. Established in 1947 by the Science and Security Board of Bulletin of the Atomic Scientists, the Doomsday Clock was initially set at seven minutes to midnight, making its debut on the cover of Time in that same year.

The founding members of the board were scientists involved with the Manhattan Project.

The clock was developed as a way to communicate the dangers of nuclear weapons to the public as tensions between the Americans and Soviets during the Cold War began to rise. At that time, America was the only nation known to have nuclear weapon technology.

Since then, the board has reviewed the clock every year to determine the state of humanity’s safety. The board, which includes 17 Nobel laureates, now considers climate change and emerging technologies to be among the biggest threats to humankind.

The Doomsday Clock has oscillated between two minutes and 17 minutes to midnight over its 68 years of existence. Here are some of the more terrifying moments in history that brought the world less than five minutes from Doomsday since the clock was first set.

Three minutes to midnight – 1949

In 1949, seismic activity raised suspicions that the Soviets had carried out an underground nuclear test. Fear of the progression of the Soviet nuclear program sent the American government into a panic, and a nuclear arms race blasted off. The Americans increased funding to accelerate military programs and later develop the hydrogen bomb.

Two minutes to midnight – 1953

In 1952, the Americans tested their first hydrogen bomb. The bomb resulted in a yield of 10.4 megatons with a fireball more than three miles wide, destroying an island. The test was only meant to prove the theory behind the bomb, as a deployable bomb had yet to be developed.

Soon after, in 1953, the Soviets also carried out hydrogen bomb testing. While their bomb was much less powerful, with a yield of 400 kilotons, it was small enough for deployment. With the power of destruction increasing on both sides, the Doomsday Clock ticked closer to midnight.

Four minutes to midnight – 1981

Nearly 30 years later, Cold War reached a new height. While various events had led to the Doomsday Clock’s hand moving further away from midnight, indicating hope for the future, the events of 1981 brought the hand mere minutes to the hour once again. The Soviet invasion of Afghanistan, provocative American rhetoric, and a rapidly increasing arsenal of intercontinental ballistic missiles and planes capable of delivering nuclear bombs on both sides threatened the future of humankind.

Three minutes to midnight – 1984

In 1984, the Bulletin of Atomic Scientists moved the hand closer to midnight, explaining that “every channel of communications has been constricted or shut down; every form of contact has been attenuated or cut off. And arms control negotiations have been reduced to a species of propaganda.”

Three minutes to midnight – 2015

While the Cold War has long since ended, relations between Russia and the U.S. are once again icy. Nuclear weapon proliferation continues to be a threat. It is thought that there are nine nations currently operating with nuclear weapons, including Russia, the U.S., France, China, the United Kingdom, Israel, Pakistan, India, and North Korea.

In addition to the risk of nuclear catastrophe, climate change continues to melt polar ice caps, thaw permafrost, and destroy shorelines, with a continued dependency on fossil fuels further threatening the safety of humanity.