"God sometimes does His work with gentle drizzle, not storms. Drip. Drip. Drip." - John Newton (Amazing Grace)
Question #90171 posted on 08/08/2017 7:14 p.m.
Q:

Dear 100 Hour Board,

Are nuclear bombs scalable downwards? Lets say for example that there is a colony of sentient ants that decides that the only way to avoid being fumigated or smashed by humans is to develop nuclear technology. Would an ant sized nuclear bomb work the same as a human sized one? Would we be in any real danger?

-Little Boy

A:

Dear Littlest Boy,

Did you ever read the Island series of books by Gordon Korman? I just bring it up because that was the first time I'd ever heard of Fat Man and Little Boy.

Anyway.

This Quora post enlightened me on the finer points of how nuclear bombs work. Essentially, what you've got is a bunch of Plutonium that's teetering on unstable, but isn't quite there yet. You surround the Plutonium with an explosive; when the bomb hits its target, the explosive goes off and compresses the Plutonium. When the Plutonium hits "critical mass," it becomes too dense to support itself, so it becomes very un-dense very quickly. In other words, it explodes.

Now, according to that same Quora post, there's a limit to the amount of Plutonium you can use to cause a reaction like this; if you have too little Plutonium, the amount of energy needed for the explosion to compress that Plutonium to unstable densities becomes too big, and the reaction fails. The limit is apparently a chunk of Plutonium about the size of a softball, and they used chunks like this to make W54's, small-scale nuclear weapons that could feasibly be stuffed into a backpack-sized container, thus giving rise to the term "backpack nuke" (which is a very scary term).

We fortunately have some footage of what it looks like when a W54 detonates, as they were used in the M28/M29, otherwise known as the "Davy Crockett." Here's the video (which was helpfully provided by this blog). As you can see, it's a fairly small explosion for a nuclear weapon. The Davy Crockett was comparable to blowing up somewhere between 10-20 tons of TNT. In contrast, the Fat Man bomb, which was dropped on Nagasaki, was the equivalent of 20 kilotons of TNT; it was roughly 1,000 times more powerful than the Davy Crockett. Why even have the Davy Crockett, then? Well, as Wikipedia notes, the Davy Crockett created an "extreme radiation hazard;" the detonation produced an almost instantly lethal amount of radiation within a 500-ft. radius of the blast zone, and anyone within a quarter-mile of the blast would have likely died from the exposure. The goal was not so much to cause massive amounts of destruction and more to slow the enemy down by creating really big radiation zones, which just sort of depresses me to think about.

Getting back to the point, this is all to say that an ant-sized nuclear weapon isn't really possible: the amount of Plutonium would just be too small. Even if such a thing were possible, though, if we use the Davy Crockett as an example, it seems to me that an ant nuclear weapon would only be about as dangerous as a firework, with perhaps an added risk of radiation exposure. 

Let's just be friends with the ants anyway. They can be kind of terrifying as they are, anyway.

-Frère Rubik

A:

Dear Little Boy Riding Hood,

I have no clue about the first two questions, but I think the real danger would be that a colony of ants was smart enough to develop nuclear technology. Just think, next they would have GMO foods. Think of the dangers!

-Sunday Night Banter