Try to survive, and don’t forget your sunscreen

"Little Boy" was the bomb dropped on Hiroshima in 1945, and here's roughly what happened. First, a flash bright enough to blind anyone who looked straight at it, sometimes for good. Then the heat: severe burns for anyone within 2 km, sunscreen obviously not included in the survival kit. The blast came next and leveled almost everything, total flattening up to 1.5 km, crumbling buildings and mass casualties out to 3 km. And then the black rain fell, radioactive dust drifting tens of kilometers out, doing its damage slowly through cancer instead of quickly through blast force. Not exactly a holiday destination, then or for decades after.

How you might not die

Say a bomb is inbound. Don't panic, panicking just wastes the little time you have. If you're standing in the fireball or catch the flash directly, there's nothing to be done, you're gone before you'd even register it. Between 1.5 and 4 kilometers out, though, you've actually got a shot. Get underground: a subway, a parking garage, a cave if you happen to live near one. Staying above ground means the shockwave gets you if the fire doesn't. After that comes the fallout, radioactive dust settling into the air, the water, everything. From there, your job is simple: stay put, seal the space, and wait. The first day is the most lethal, the next few aren't much better, and only after about forty-eight hours do you get a real chance at breathing outside air again.

Want the official version? FEMA, the US emergency agency, sums it up in three steps: get inside, stay inside, stay tuned. Read their nuclear explosion info sheet (PDF).

💡Note: these survival estimates are based on what actually happened in Hiroshima in 1945.

The atom-proof backpack

Under 18, pregnant, or breastfeeding? Pack iodine tablets, they protect your thyroid from radiation. But only take them when the authorities tell you to: taken too early or for no reason, they can do more harm than good. Beyond that: water, food that keeps, warm clothes, and a hand-crank flashlight that doesn't care about EMPs. An old phone is worth keeping too. Wrap it in a metal box with its cable and a power bank, which should soften an EMP's punch, though nothing's guaranteed there. Throw in a radio, a first aid kit, something to cover your face against fallout dust, tape and plastic sheeting for sealing gaps, and basic hygiene supplies. And bring something to read. Even the apocalypse gets boring.

💡Tip: still got an old metal tin lying around? Yes, an old Pokémon card box counts. Drop a basic phone in there, ideally something ancient like a brick-style Nokia, battery removed and wrapped in cloth or paper.
That tin acts as a makeshift Faraday cage, which should improve its odds against an EMP. No promises, but it beats leaving it out in the open.

Myths that get people killed

Be ready before it happens

Nobody wants to think about this one. That's exactly why a little preparation puts you ahead of almost everyone.

• Know where the nearest underground spaces are: at home, at work and at school.
• Find out how your country sounds the alarm, and what the sirens mean.
• Check your emergency kit twice a year: replace water and food before they expire, and test the batteries.
• Live near a nuclear power plant? Check if you're in a zone where iodine tablets are handed out, and where to get them.
• Agree with your family that everyone takes shelter where they are. Don't drive across town to pick up your kids: schools shelter their students too.
• Keep a set of spare clothes in your shelter spot, in case you have to change out of dusty ones.

Real story: the man who survived both bombs

In August 1945, engineer Tsutomu Yamaguchi was on a business trip to Hiroshima. On the morning of August 6, he was about three kilometers from the center when the bomb exploded. He was badly burned and temporarily blinded, but he survived the night in a shelter.

The next day, he traveled home to Nagasaki. On August 9, while telling his boss about the explosion in Hiroshima, the second bomb exploded over Nagasaki, again about three kilometers away. He survived that one too, and lived until the age of 93. He is the only person officially recognized by Japan as a survivor of both bombings.

💡Tip: in Hiroshima, even ordinary clothes blocked part of the heat flash, and light-colored clothes worked better than dark ones. Covered skin is protected skin.

Did you know?

Hiroshima's bombing in August 1945 killed roughly 78,000 people on impact, with that number climbing to around 140,000 by the end of the year. Radiation sickness and cancer kept killing people for decades after, and by 2004, Hiroshima's own city estimates put the total closer to 237,000.
And that was from a 15-kiloton device, a relatively small one by today's standards.