Doomsday has always been at least seven minutes away. That's according to the "Doomsday Clock," a symbolic timepiece that ticks off humanity's proximity to, well, doom. (Doom!)

The clock, introduced by members of the Bulletin of the Atomic Scientists in 1947, was designed to warn people about the implications of global nuclear armament. It has since expanded its doomscale to track other potential disasters for humanity—most recently, climate change.

The way the clock works: The closer to midnight it is set, the worse off we are.

Today the Bulletin announced doomtime is now three minutes to midnight, whereas at last check, in 2012, we were five minutes away from doom. Here's the latest explanation:

Unchecked climate change, global nuclear weapons modernizations, and outsized nuclear weapons arsenals pose extraordinary and undeniable threats to the continued existence of humanity, and world leaders have failed to act with the speed or on the scale required to protect citizens from potential catastrophe.

It was already 11:53 p.m. when the clock was introduced, which is a pretty grim place to start—and, of course, just the right amount of dramatic tension to get people's attention.

Over the years, the minute hand has crept forward and back. (And our net movement has been forward—that is, closer to calamity—over the years.)

Humanity was farthest from doom in 1991, after the signing of the Strategic Arms Reduction Treaty and the dissolution of the Soviet Union. It was closest to doom in 1953, when the Bulletin announced it was 11:58 on the doom clock. (The reason: The ongoing development of thermonuclear bombs in the United States and hydrogen bomb tests in the Soviet Union.)

We've been as close to doom o'clock as we are now on three occasions, including today:

  • 1949: When the Soviet Union tested the atomic bomb and the arms race began
  • 1984: When the arms race intensified during the Cold War and relations between the United States and the Soviet Union reached "their iciest point," according to the Bulletin
  • 2015: Climate change and the threat of nuclear-weapons use

Creeping forward two minutes in a period of three years may seem slow by regular timekeeping standards. But the clock has only ever spanned 14 total minutes—in either direction—over the past 66 years. The biggest time jump was between 1990 and 1991, when there was a seven-minute shift away from doom.

Back in the halcyon days of 1991, just after the end of the Cold War, the Bulletin declared humanity to be 17 glorious minutes away from doom—practically an eternity compared with previous and subsequent Doomsday Clock readings.

The device is an effective way to highlight some of the biggest challenges the planet faces, but it's also a pretty clunky one, technologically speaking.

Clocks have always been a way of looking ahead (or, around and around). People wear watches with the assumption that time will continue to march forward and that we will continue to have a need to keep track of it. What time is it? is mostly a way of asking, What time is it about to be? We set alarms with the expectation that the sun will, in fact, rise again tomorrow.

A metaphorically appropriate alternative—Doomsday Seesaw, anyone?—may not carry the same sense of urgency as a tick-tocking clock. But the idea that we're so close to doom now, as bad as things may be, also seems at least a little unimaginative. What might the world even look like at 11:01 p.m. on the Doomsday Clock? Or, better yet, around dinnertime? And what if we've already gone so far past doom that it's really 5 a.m., an idea a letter writer to The New York Times floated in 1995.

Assuming that everything comes crashing down at midnight, the most desirable time on the clock would have to be noon, farthest from doom in either direction.