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Comment by mttyng | Hacker News Reader

Assuming we (Earth) get some reasonable warning time for a problematic impact, the logistics of alerting -and then moving- a large metropolitan area like NYC, for example, are interesting. Where do we place these people? What about the city's infrastructure? Do we just stand by, brace for impact and hope for the best? Or is there something more we could do to mitigate the disaster? I know a lot of that depends on the amount of time beforehand, but I find the problem intriguing.

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You may be interested in a recent episode of the 99 Percent Invisible podcast (https://99percentinvisible.org/episode/atomic-tattoos/). The title of the podcast comes from a Cold War program carried out in 1952 in which students could opt to receive a small tattoo of their blood type, with the goal of creating a "walking blood bank" in the event of a disaster requiring mass transfusions.

Related to your question, the episode also explores the history of "duck and cover." It turns out it's there is some credibility to the technique. In September 1945, the US sent a team called the Atomic Bomb Casualty Commission to Japan to research and interview survivors of nuclear blasts. They located survivors just a few blocks from the explosion epicenter, who had been sheltered by concrete basements. They also heard stories of people who were killed just by shattering windows and falling debris. With just some ability to shelter, survivability might be higher than you suspect.

That's really interesting, for itself and other reasons. The US sending a commission into Japan (in '45!) for the sole purpose of studying survivability related to atomic blasts seems sort of mind-blowing to me.

Thank you for the podcast reference.

We had a recent example of the value of "duck and cover" - and more specifically what happens if you don't do it - the Chelyabinsk meteor.

"Its explosion created panic among local residents, and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide's flash."

Many of the injured went to a window to see the spectacle in the sky, not realizing that the shock wave was about to shatter the window in their face.

https://en.wikipedia.org/wiki/Chelyabinsk_meteor

>Many of the injured went to a window to see the spectacle in the sky, not realizing that the shock wave was about to shatter the window in their face.

Same thing happened in the Halifax explosion.

That explosion was close enough that there would be basically no chance to react between the actual explosion and the shock wave.

And from that article, there's even a way to compare the effects of duck & cover:

"A fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, was hailed as a hero after saving 44 children from imploding window glass cuts. Despite not knowing the origin of the intense flash of light, Karbysheva thought it prudent to take precautionary measures by ordering her students to stay away from the room's windows and to perform a duck and cover maneuver and then to leave a building. Karbysheva, who remained standing, was seriously lacerated when the blast arrived and window glass severed a tendon in one of her arms and left thigh; none of her students, whom she ordered to hide under their desks, suffered cuts."

Back in elementary school, we practiced duck-and-cover not as a defense against nuclear war (although we were only a couple of kilotons from the DoE Pantex plant), but against tornadoes. They're not entirely different, effectwise.

see how evacuations before large hurricanes or other predictable disasters are going. It's problematic at best.

Those don't serve as good examples since e.g. for hurricanes by the time the evacuation order is given the weather itself is causing issues for the evacuation.

It would still be a logistical nightmare, but other things being equal should proceed in a more orderly fashion than a hurricane evacuation, especially since the exact time of impact would be known in advance.

They do serve as a good indicator. The primary problems that occur during evacuations are "people don't believe it will hit them" and "there's no way to move all those people." I'd also doubt that our math is good enough to precisely calculate the impact point of a meteorite more than few days in advance. Hit/no-hit probably, and which region, yes, but off by 50km? Meteorites break up on atmospheric impact, getting the precise point right is probably impossible.

The earth is rotating so fast. You’d need really precise timing to know where it would hit.

we can account for a nanosecond discrepancy in the flow of time between two objects separated by hundreds of miles. IE: accounting for reletivity to sync time between phones and satellites. We have the technology.

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