It is getting closer to midnight.
On Thursday, the group of scientists who orchestrate the Doomsday Clock, a symbolic instrument informing the public when the earth is facing imminent disaster, moved its minute hand to 2 1/2 minutes before the final hour.
It was the closest the clock had been to midnight since 1953, the year after the United States and the Soviet Union conducted competing tests of the hydrogen bomb.
Though scientists maintain the clock's status, it is not a scientific instrument, or even a physical one. The movement of its symbolic hands is decided upon by the Science and Security Board of the Bulletin of the Atomic Scientists. The organization introduced the clock on the cover of its June 1947 edition, placing it at seven minutes to midnight. Since then, it has moved closer to midnight and farther away, depending on the board's conclusions.
Thursday's announcement was made by Rachel Bronson, the executive director and publisher of the bulletin. She was assisted by theoretical physicist Lawrence Krauss, climate scientist and meteorologist David Titley, and former U.S. Ambassador Thomas Pickering.
In an op-ed for The New York Times, Titley and Krauss elaborated on their concerns, citing the increasing threats of nuclear weapons and climate change, as well as President Donald Trump's pledges to impede what they see as progress on both fronts, as reasons for moving the clock closer to midnight.
"Never before has the Bulletin decided to advance the clock largely because of the statements of a single person," they wrote. "But when that person is the new president of the United States, his words matter."
The board has held the responsibility for the clock's movements since 1973, when the bulletin's editor, Eugene Rabinowitch, died. Composed of scientists, and nuclear and climate experts, the board meets biannually to discuss where the clock's hands should fall in light of world events.
In the 1950s, the scientists feared nuclear annihilation, and since then, the board has begun to consider other existential threats, including climate change, compromised biosecurity and artificial intelligence.
The end of the Cold War came as a relief to those who had lived in fear of nuclear annihilation for decades, and the minute hand slowly moved away from danger. In 1990, it was at 10 minutes to midnight. The next year, it was a full 17 minutes away, at the relatively undisturbing time of 11:43.
"The illusion that tens of thousands of nuclear weapons are a guarantor of national security has been stripped away," the Bulletin said at the time.
But over the next two decades the clock slowly ticked back. Conflict between India and Pakistan, both of whom staged nuclear weapons tests three weeks apart, had the clock at nine minutes to midnight in 1998. By 2007, fears about Iranian and North Korean nuclear capacity had pushed it to 11:55.
By 2015, the scientists were back in a state of unmitigated concern, with the clock at three minutes to midnight, the closest it had been since 1984.
"Unchecked climate change, global nuclear weapons modernizations, and outsized nuclear weapons arsenals pose extraordinary and undeniable threats to the continued existence of humanity," the bulletin said. "World leaders have failed to act with the speed or on the scale required to protect citizens from potential catastrophe."
"These failures of political leadership endanger every person on Earth," it added.