As of the launch of this question, it is generally believed that no fewer than nine countries in the world have nuclear weapons (Arms Control Association, Federation of American Scientists). Whether a detonation is characterized as a test, an accident, a warning, or an attack would be immaterial, and the detonation of a device in orbit around Earth would count. A radiological device (aka "dirty bomb") would not count (Mass.gov). Whether or not a nuclear device has been detonated will be determined using credible open source media reporting. That determination must be made during the question's open period to count, as well as the detonation.

Confused? Check our FAQ or ask us for help. To learn more about Good Judgment and Superforecasting, click here.

To learn more about how you can become a Superforecaster, see here. For other posts from our Insights blog, click here.

NOTE 5 October 2023: The question is concerned with a nuclear device being detonated. A nuclear-fueled delivery system, like a missile, for a nuclear device is immaterial.

The question closed "No" with a closing date of 1 January 2024.

See our FAQ to learn about how we resolve questions and how scores are calculated.