Answers to common questions

Co-editor Hyman Goldsmith asked artist Martyl Langsdorf to come up with a design for the cover of the June 1947 edition of the Bulletin, the first issue published as a magazine rather than a newsletter. Martyl—as she was known professionally—was married to a physicist, Alexander Langsdorf, who worked on the Manhattan Project at the University of Chicago.

At first, the artist considered using the symbol for uranium. But as she listened to the scientists who had worked on the Bomb, as they passionately debated the consequences of the new technology and their responsibility to inform the public, she felt their sense of urgency. So she sketched a clock to suggest that we didn’t have much time left to get atomic weapons under control.

Graphic designer Michael Bierut reimagined the iconic image in 2007.

Martyl set the original Clock at seven minutes to midnight because, she said, “it looked good to my eye.”

In the early days, Bulletin Editor Eugene Rabinowitch decided whether the hand should be moved. A scientist himself, fluent in Russian, and a leader in the international disarmament movement, he was in constant conversation with scientists and experts within and outside governments in many parts of the world. Based on these discussions, he decided where the clock hand should be set and explained his thinking in the Bulletin’s pages.

When Rabinowitch died in 1973, the Bulletin’s Science and Security Board took over the responsibility and has since met twice a year to discuss world events and reset the clock as necessary. The board is made up of scientists and other experts with deep knowledge of nuclear technology and climate science, who often provide expert advice to governments and international agencies. They consult widely with their colleagues across a range of disciplines and also seek the views of the Bulletin’s Board of Sponsors, which includes nine Nobel Laureates.

After the Soviet Union successfully tested its first atomic bomb in 1949, Rabinowitch reset the clock from seven minutes to midnight to three minutes to midnight.

In 2023, the Science and Security Board set the time to 90 seconds to midnight, largely (though not exclusively) because of the dangers of the war in Ukraine. Before 2023, the closest the hand was set to midnight was 100 seconds to midnight in 2020.

In 1991, with the end of the Cold War, the United States and the Soviet Union signed the Strategic Arms Reduction Treaty, the first treaty to provide for deep cuts to the two countries’ strategic nuclear weapons arsenals, prompting the Bulletin to set the clock hand to 17 minutes to midnight.

No. They were not moved during the 10-day crisis because too little was known at the time about the circumstances of the standoff or what the outcome would be. In fact, after the crisis, US and Soviet leaders installed a direct telephone line for communication, and within months signed the Partial Test Ban Treaty outlawing underground nuclear weapons testing—the first treaty addressing the nuclear weapons threat. On the basis of these steps, the Bulletin set the clock back from seven minutes to midnight to 12 minutes to midnight in 1963.

Since February 2019, the Doomsday Clock has been located in the Bulletin offices at the University of Chicago: 1307 East 60th Street, 1st floor. Click on the "Timeline" link on the Doomsday Clock page for an interactive timeline of the clock’s history and the reasoning behind each resetting.

The Doomsday Clock is not a forecasting tool, and we are not predicting the future. Rather, we study events that have already occurred and existing trends. Our Science and Security Board tracks numbers and statistics—looking, for example, at the number and kinds of nuclear weapons in the world, the parts per million of carbon dioxide in the atmosphere, the degree of acidity in our oceans, and the rate of sea level rise. The board also takes account of the pace of leaders’ and citizens’ efforts to reduce nuclear dangers, and the urgency of actions by governments, markets, and civil society organizations to reduce greenhouse gas emissions.

The Bulletin is a bit like a doctor making a diagnosis. We look at data, as physicians look at lab tests and x-rays, and also take harder-to-quantify factors into account, as physicians do when talking with patients and family members. We consider as many symptoms, measurements, and circumstances as we can. Then we come to a judgment that sums up what could happen if leaders and citizens don’t take action to treat the conditions.

Ensuring the survival of our societies and the human species is not a political agenda. Cooperating with other countries to achieve control of extremely dangerous technologies should not involve partisan politics. If scientists involved with the Bulletin are critical of current policies on nuclear weapons and climate change, it is because those policies increase the possibility of self-destruction.

The Bulletin has moved the Clock hand away from midnight almost as often as it has moved it toward midnight, and as often during Republican administrations in the United States as during Democratic ones. It moved the hand farthest away in 1991 when US President George H.W. Bush’s administration signed the Strategic Arms Reduction Treaty with the Soviet Union.

As long as nuclear weapons exist and can be used, the risk that we could destroy civilization also exists. Such a calamity has not occurred because national leaders have so far heeded warnings, and because at critical times in the past 78 years, they have set up communication channels with adversaries, negotiated treaties to control the weapons, taken steps to radically reduce arsenals, and engaged erstwhile enemies in cooperative projects. Preventing nuclear war requires continued diplomacy, more exchanges of information, and open communications that engender trust.

Likewise, as long as Earth’s climate continues to change, we are at risk of suffering the potential consequences, in particular disruptions in the environment—such as extended droughts, changes in growing seasons, sea level rise, and fisheries die-offs—that threaten human survival.

Humans invented both nuclear weapons and the fossil-fuel powered machines that contribute to climate change; we know how they work, so presumably we can find ways to reduce or eliminate the harm. But we need concerted cooperation worldwide to prevent calamity.

Each of these threats has the potential to destroy civilization and render the Earth largely uninhabitable by human beings. They are also intertwined: Some advocate for more nuclear power to reduce carbon dioxide emissions, but increasing the number of nuclear reactors, and the amount of enriched uranium and plutonium required for their operation, would also increase the risk of spreading nuclear weapons. Likewise, if we don’t reduce emissions, some natural resources, like fresh water, could become more scarce, leading to conflicts that might spiral into war and the possible use of nuclear weapons.

We can’t afford to address one threat without addressing the other. And in fact, the international cooperation required to reduce and prohibit nuclear weapons would likely also lead to cooperation to save us from deadly climate disruption. At the end of the day, trying to answer the question is like standing around in a burning house arguing about whether it is better to die of smoke inhalation or from a falling timber.

First, get smart about the problems. Nuclear weapons and climate change may seem to be outside our daily experience and beyond our control, but we all have a stake in avoiding untimely death. We want to live our lives free from destruction by nuclear weapons and from the growing scarcity of natural resources brought about by a warming planet. These interests in survival should motivate us to learn as much as we can about the powerful technologies that could destroy our way of life.

Second, share what you’ve learned with others—in your family, workplace, church, school, or social media feeds. The more we talk to each other about what matters most—surviving and flourishing—the more confidence we’ll have about expressing our interests.

Third, tell your government representatives that you don’t want even more of your tax money spent on nuclear weapons or on subsidizing carbon dioxide-producing fossil fuel technologies. Write letters, tell them at town hall meetings, email their offices, and let them know that your security depends on getting rid of nuclear weapons and on finding ways to keep our planet habitable for humanity.