

Ask HN: What would happen if an EMP were detonated over the United States? - SpikeX

As the title states, what would happen if a large EMP were detonated over the United States so as to disable/destroy non-shielded electrical equipment? Are most things protected from electromagnetic interference, or are we talking full-blown riots across the entire country? What would be affected? Would you be able to use your cell phone? Get money out of your bank account(s)? How bad would it actually be?
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HedgeMage
It depends a lot on the power and placement of the EMP, as well as when it
went off. There are a lot of scenarios in which it just wouldn't be that bad.
Just for fun, let's muse on the worst-case scenario: all except specially
shielded (mostly military) electronics would become non-functional, and
replacing all that would take serious time and money. Money, by the way, that
we can't get to because all of our banking systems are electronic, and that
may not have much real value after such a disaster.

I know a few of my fellow hams who still maintain very old-school rigs that
wouldn't be affected beyond hand repair by an EMP. The country would pretty
much rely on us for communication.

Without a working car, my son and I would be left on foot to get to the family
farm, unless we could trade for horses along the way. Once there, living off-
grid isn't a problem. My grandparents never fully trusted modern technology,
so my brother and I were schooled in preserving food without power, cooking,
heating/cooling a home off-grid, and so on. If this happened in the middle of
a harsh winter, we'd face a couple of hard months before scaling up our farm
and food preservation efforts, but having confidence that it was temporary
would do a lot to get us through.

Not only do all of these give us a way to survive, but they give me things to
barter for what we don't have or can't produce.

Cities would have riots, starvation, dehydration, and disease. Suitably rural
communities would get by okay, and possibly prosper, under such conditions.
City life is just plain unsustainable -- there's nowhere to grow/raise
adequate food, no one is taught life skills like growing/raising food (or they
rely on commercial fertilizers, garden hoses, etc. to do so), preserving food
without electric refrigeration, and so on. Even disposing of sewage and
getting clean water depend on electronic-controlled infrastructure. Garbage
would pile up like mad without trucks to come get it.

An acquaintance of mine once asked what he should do in such a doomsday
scenario. I told him that there was really no way he'd survive, as he lacked
any useful skills. He pointed out that he was an extremely good coder, and I
asked him what he was going to program. He asked if he could come to the farm
with me, and I explained that we can't afford to take on people who aren't
prepared to lend anything to our survival.

It varies a lot by scale, the type of land, and what other resources are
available, but as a rough estimate you need about 1 acre per person you wish
to sustain at a bare minimum. On a smaller scale, with less-than-ideal land,
or with inexperienced/incompetent farmers, you need much more than that. If
you want someone with those resources to let you make a home on their property
(we WILL shoot you if you try to trespass and take resources), you'd better
have something to offer in return.

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Detrus
I think the History Channel had a scaremongering show about coke can sized
EMPs at 30,000 feet having the range to take out most of US
electrical/computer systems.

If such EMPs did have the range, it would be scary indeed. Everything except
hardened military equipment would go if a terrorist could sneak one in on a
plane. Some records may be backed up in datacenters in other countries, that's
the only protection for civilians.

But coke can EMPs at 30,000 feet don't really have the range. You'd need a
specially designed nuclear warhead around 1 megaton at far higher altitude to
take out a big chunk of the US.

I asked a related question on Quora [http://www.quora.com/Are-datacenters-
protected-against-EMP-a...](http://www.quora.com/Are-datacenters-protected-
against-EMP-attacks) lots of links in the answers

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fagatini
Depends on the size, of course. It would take more than 1 to cripple the
entire country I would assume, but yes, if enough went off the country would
grind to a halt. Cell phones, ATMs, etc would not work, at least for a time.

There are tons of books about this. [http://www.amazon.com/One-Second-After-
William-Forstchen/dp/...](http://www.amazon.com/One-Second-After-William-
Forstchen/dp/0765317583/ref=pd_sim_b_4) was a good one. Fiction, but still.

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tlb
A sufficiently powerful EMP could destroy all electronic circuits, even ones
that aren't powered on. It might take a long time to recover.

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fagatini
And you know what they say, "all first world countries are just 3 meals away
from chaos" or something to that effect.

