The Doomsday Clock Keeps Ticking: Out There

"The Bomb and I go way back. In Seattle, where I grew up in the 1950s and ’60s, it was common wisdom that in the event of nuclear war, we were No. 2 on the target list because Seattle was the home of Boeing, maker of B-52 bombers and Minuteman missiles.

In school we had various drills for various catastrophes, and we had to remember which was which. Earthquake? Run outside. The Bomb? Run inside, to an inner corridor that had no windows. In the summer, my high-school friends and I would disappear for a couple of weeks into the backcountry of the Cascades or the Olympic Mountains. I always wondered whether we would emerge to find the world in ashes.

Once, in Santa Monica in 1971, I thought it was finally happening. I woke up on the floor, having been bounced out of my bed early one February morning. There was a huge roar. Everything was shaking. I crept to my one window and pulled aside the curtain, expecting to see a mushroom cloud rising over the Los Angeles basin. I saw nothing. When the radio came back, I learned there had been a deadly earthquake in the San Fernando Valley.

I was sent on this trip down memory lane by the announcement on Jan. 23 from the Bulletin of the Atomic Scientists that it had decided not to change the setting of the Doomsday Clock, a metaphorical timepiece invented in 1947 as a way to dramatize the threat of nuclear Armageddon. The clock was originally designed with a 15-minute range, counting down to midnight — the stroke of doom — and the Bulletin’s members move it from time to time in response to current events, which now include threats like climate change and pandemics.

In a burst of optimism in 1991, after the Soviet Union broke up and the first Strategic Arms Reduction Treaty was signed, the clock was turned way back to 17 minutes to midnight. “The Cold War is over,” the Bulletin’s editors wrote. “The 40-year-long East-West nuclear arms race has ended.”

A year ago, after Russia invaded Ukraine and brandished the threat of using nuclear weapons, the clock was set to 90 seconds to midnight, the closest it has yet come to The End. The threat of nuclear weapons in Ukraine has diminished since then, but the clock remains poised at 90 seconds before zero.

This year’s announcement came on the same day that “Oppenheimer,” Christopher Nolan’s biopic of the man who directed the invention of the Bomb, received 13 Oscar nominations. In an interview before the film’s release, Mr. Nolan described Robert J. Oppenheimer as the most important human in history because his invention had either made war impossible or doomed us to annihilation.

The jury is still out. Among cosmologists, the question is whether we are the only beings in the universe that have subjected ourselves to such a fate. How special are we and our doomsday clock?

Back in 1950, during a lunchtime conversation with colleagues about U.F.O. sightings, the physicist Enrico Fermi wondered aloud: “Where is everybody?” The cosmos is vast and possibly filled with alien life — so why are humans so seemingly alone?

In the 1970s and ’80s, the astrophysicists Michael H. Hart and Frank J. Tipler expanded on what came to be known as the Fermi paradox. The Milky Way galaxy is 10 billion years old, they noted, but any intelligent civilization that arose in it should need only 100 million years or so to visit or colonize every planet in it — perhaps by sending self-replicating robot probes into space so that the number of planets or stars visited would double, say, every 10,000 years.

Yet there is no evidence that Earth has been visited, or even pinged by interstellar radio signal — the Great Silence, radio astronomers call it. Why?

One simple answer is that other civilizations are too sparse in space and time for us to ever know of one another’s existence. Or that we truly are alone, despite the intimations of possibility in images from the James Webb Space Telescope of galaxies scattered like sand in the winds of time. Life arose on Earth within half a billion years of its formation, which suggests to hopeful astrobiologists that generating life is easy, at least in microbial form. Maybe intelligence is the hard part.

Another theory is that intelligent civilizations, when they do arise, don’t long survive their own intelligence, or at least not long enough to make a dent in the cosmos. Robin Hanson, an economist at George Mason University, has suggested that major civilizations inevitably succumb to what he calls the Great Filter: a barrier or series of them that either prevents life from forming in the first place or clips a technological race’s wings before it can go interstellar. War, pestilence, climate change and misbegotten genetic experiments are on the list of potential apocalypses. Are we lucky to have gotten this far, or is disaster ahead?

In another chilling view, humanity is akin to a child lost in a forest full of dangerous, paranoid creatures, i.e., extraterrestrial civilizations. We are safe as long as we keep our mouths shut.

In the 1980s, Jeremiah P. Ostriker and Edwin L. Turner, astronomers at Princeton, used mathematical models from ecology to explore the idea of galactic colonization to which Drs. Hart and Tipler alluded. They proposed that a variety of intelligent civilizations would pop up everywhere in the galaxy and eventually interact, sometimes trading, sometimes fighting. Only the most aggressive and paranoid would survive those interactions, leaving one killer species supreme. Realizing this, other civilizations would not want to draw attention to themselves. This notion came to be known as the Dark Forest, after the title of a popular 2008 science-fiction novel by Liu Cixin.

Any new intelligent civilization appearing in that galaxy — humankind, for instance — would last only until its signals had been emitted long enough to be detected by the killer cosmic neighbors. Dr. Ostriker put “long enough” at maybe 5,000 years.

“Our signals have reached out to only 100 or so light-years, as that is how long we have been sending out radio waves and other signs of advancement,” he said in a recent interview. “If we ever do receive signals from outer space, we should treat them with extreme caution.”

The idea has featured in various science-fiction novels, including “The Killing Star” (1995), by Charles R. Pellegrino and George Zebrowski, and “The Forge of God” (1987), by Greg Bear.

Any way you look at it, our prospects are grim. But there might be a threadbare glimmer of hope, for some forms of life at least. Even full-on thermonuclear war would not kill everything; some microbes can live in nuclear reactors and other unlikely environments. We are all made of microbes descended from the first cells that appeared 4.5 billion years ago on a nascent Earth that would be uninhabitable to us.

The secret sauce of life is evolution and natural selection, not any particular species. The extinction of a species — dinosaurs, polio viruses, us — is a loss for the vigor of the world, but it opens realms of possibility for others, new avenues of evolution. With another billion years to go before the sun burns Earth to a crisp, our planet’s most interesting life-forms may be yet to come.

Of course, if we mind the Doomsday Clock, we could still change our ways and survive to inherit the galaxy. Even 90 seconds to midnight isn’t too late to improve our game in relation to one another and to Earth.

“It’s difficult to assess what’s good news and what’s bad news, from the perspective of humanity in the next century,” said Daniel Holz, a physicist at the University of Chicago and a member of the Bulletin. “Black hole physics is a hell of a lot easier.”" [1]

1. The Doomsday Clock Keeps Ticking: Out There. Overbye, Dennis.  New York Times (Online)New York Times Company. Feb 12, 2024.