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In this question, I found out that a single EMP is not enough to stop all mobile phones from working. So as a follow-up question: how many EMPs would you need, and how expensive would this be?

To be clear, it is ok when other things become disabled too, if that makes it easier.

Also, both nuclear and non-nuclear EMPs are allowed.

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    $\begingroup$ Worth noting, as it was in your other question, that any individual or networked chain of EMPs capable of wiping out every mobile phone (or giving them all zero bars by wiping out their base stations) would also kill hundreds of millions of people, either by direct blast effects or the fact that most other electronics would also stop. $\endgroup$
    – jdunlop
    Jun 27, 2023 at 21:43
  • $\begingroup$ An EMP which is not so strong that it kills the users will have just about zero effect on the mobile phones themselves. What you may try is to fry the transponders in the cellular towers; but any EMP which is strong enough to fry the transponders will also fry all the wired infrastructure -- telephones, cable TV, power grid etc. $\endgroup$
    – AlexP
    Jun 27, 2023 at 22:53
  • $\begingroup$ In the immediate aftermath of an EMP, you wouldn't be able to reach anyone on your cell phone - not because it doesn't work, but because the cell network would collapse under the strain of everyone in the affected area trying to call their friends and/or the authorities. This is a well-studied effect of major disasters. $\endgroup$
    – Cadence
    Jun 28, 2023 at 0:05

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The US Department of Health and Human Services has some literature on that.

According to this page from them, Electromagnetic Pulse (EMP) Following a Nuclear Detonation:

Although experts have not achieved consensus on expected impacts, generally they believe that the most severe consequence of the pulse would not travel beyond about 2 miles (3.2 km) to 5 miles (8 km) from a ground level 10 KT IND detonation.

Also:

Cell phones and handheld radios have relatively small antennas, and if they are not connected to electrical power supplies during the electromagnetic pulse (EMP) they may not be affected, but they do rely on an intact infrastructure for communications.

So basically you'd need to make sure that every single cell tower in the world is hit by a nuke.

I am going out on a tentacle here and assume that there is a strong correlation between the presence of an electric grid and cell phone towers. So if you want to know which areas you need covered by a blast, that's basically everywhere in a world map except for oceans and some major deserts/forests.

In another question I showed some actual calculations made by boffins that show we'd need all the uranium on Earth's crust combined, most of which is unreachable with current tech, to approximate the blast from the dino killing asteroid. That impact had a radius of less than half the surface of the world... If you spread it carefully you could hit all continental areas, but at this point I am thinking that you would need an interstellar economy in order to procure all that uranium. So I am guessing it would cost more than the annual global GDP per year for wvery year you spend on this project.

And that is just considering materials. Your total implementation cost would be much greater due to three factors:

  1. Labour costs, even if your minions are not unionized,
  2. Lawsuits from destroying every city in the world as collateral damage, but mostly
  3. some cell phones connect to satellites, you have to knock those out too.

So there's too many factors to consider that could affect the final cost, but I will say it should approximate to between 0 and 1 Au Bon Pain lawsuits.

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    $\begingroup$ I made the point in your second quote in a comment to the OP's previous question. Riemann? Does it matter what else is disabled in the process? Would it count if the cell towers were disabled and not the phones themselves? From a physics point of view, there isn't a way to only disable cell phones with an EMP. Now, if all you want to do is jam them.... $\endgroup$
    – JBH
    Jun 28, 2023 at 4:54
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    $\begingroup$ @JBH it is ok to disable other things as well $\endgroup$
    – Riemann
    Jun 28, 2023 at 10:43
  • $\begingroup$ Hold on do we need to hit every cell tower? There are nodes (servers) where the information is gathered and processed right? That severely limits the amount of places that need an EMP. You can connect to the celltower but the celltower can’t forward your calls anywhere. $\endgroup$
    – Demigan
    Jun 28, 2023 at 10:50
  • $\begingroup$ @Demigan many of those places are underground and "shielded" and wouldn't be impacted by EMP. $\endgroup$ Jun 28, 2023 at 20:04
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The starfish test of a 1.5M ton warhead in 1962 caused an EMP pulse in Hawaii which was 900 miles away. It shut down their phone system. Starfish test

This was not a weapon designed to cause an emp pulse. the EMP was a side affect. A high altitude detonation can easily cover a million square miles (1000 miles by 1000 miles). To cover the continental US would only take about 4 weapons.

The effects of EMP are very brief. In some cases the currents generated ae high enough to damage the device. In other cases they probably can be restarted. The biggest issue would not be cell phones, but power lines. With the long wires, enormous amounts of current would be created destroying transformers and switching equipment. Basically the entire electrical grid would have to be rebuilt, if we can power the equipment needed to make the new components.

Besides nuclear weapons we can also get a EMP event from a solar flare. look up the Carrington Event in 1859 which shut down the telegraph system and even started a few fires from the overloaded lines. Carrington Event

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  • $\begingroup$ Your method seems to be much cheaper than the one in the other answer $\endgroup$
    – Riemann
    Jun 28, 2023 at 15:03
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    $\begingroup$ It's worth noting that modern circuits are much tougher than those that prevailed in the phone/power systems of the 1960s. $\endgroup$
    – jdunlop
    Jun 29, 2023 at 0:04
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    $\begingroup$ As a further clarification, most modern circuit boards are much more fragile than their 1960s equivalents, but they also lack long wires in which to generate an induced current. $\endgroup$
    – jdunlop
    Jun 29, 2023 at 21:59

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