Nine countries, including North Korea, have nuclear weapons. What would happen if a nuclear bomb was dropped-- say, in New York City? We talk to nuclear historian Dr. Alex Wellerstein, nuclear engineer Dr. Tetsuji Imanaka, and epidemiologist Dr. Eric Grant.

UPDATE 04/27: We've adjusted this episode to correct the elevated risk of cancer in survivors of the Hiroshima and Nagasaki nuclear bombs. If you survived the atomic bombs your risk of cancer is 10% higher than someone who is the same age as you.

Check out our full transcript here: http://bit.ly/2salOAK

Selected readings:

Alex’s nuclear weapon simulation website

Tetsuji’s paper calculating the radiation exposure of Hiroshima survivors

This review of the Life Span Study of atomic bomb survivors This sobering report on nuclear winter

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This episode has been produced by Heather Rogers, Wendy Zukerman, our senior producer Kaitlyn Sawrey, Rose Rimler, and Shruti Ravindran, with help from Romilla Karnick. We’re edited by Blythe Terrell. Additional thoughts from Lulu Miller. Fact checking by Michelle Harris. Mix and sound design by Emma Munger. Music written by Bobby Lord and Emma Munger. Thanks for recording help from John Wild. For this episode we also spoke to Prof. Richard Wakeford, Dr. Richard Turco, Prof. Brian Toon, Prof. Alan Robock, Dr. Dale Preston, Dr. William Kennedy, Dr. Jonathan D. Pollack, and a bunch of other experts on North Korea and nuclear weapons. Thank you so much. Also, special thanks to Shigeko Sasamori and Kathleen Sullivan. An extra special thanks to the Zukerman family and Joseph Lavelle Wilson.

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President Trump made history over the weekend when he became the first sitting American president to step into North Korea. But the biggest impact of that gesture may have been on Iran. Guest: David E. Sanger, a national security correspondent for The New York Times and the author of “The Perfect Weapon: War, Sabotage, and Fear in the Cyber Age.” For more information on today’s episode, visit nytimes.com/thedaily.

Background reading:

• Trump administration officials are at odds over what demands to make in new talks with North Korea, with some now considering a nuclear freeze as a first step.
• Iran on Monday violated a key element of the 2015 nuclear deal, from which Mr. Trump withdrew the United States last year.

For more information on today’s episode, visit nytimes.com/thedaily. Transcripts of each episode will be made available by the next workday.

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