Thread by @andrewfacini

Still can't believe a blockbuster film brought in millions of people and then sat them down for 3h featuring Edward Teller arguing with Oppenheimer about fission vs fusion bombs.

If you came away curious about that debate, here are some of the parameters & stakes involved 🧵1/21

"Not kilotons, but megatons" — but what's a 1-ton bomb like? How about 100 lbs? Do you grok a 1-pound firework?

Beyond a certain threshold, it's all abstracted far from day-to-day experience, and we lose touch. Same problem as properly grasping millionaire vs. billionaire. 2/

So we need a few handholds to work our way up from something intuitive to the kinds of blasts we're talking about with nuclear bombs.

Here are two charts showing *conventional* explosions you may remember. Linear scales became indecipherable quick here, but that's the point. 3/

In case you haven't seen it, check out the footage from Beirut. This was an fertilizer explosion, ammonium nitrate caught in a fire.

It had a blast (roughly) equivalent to 500 tons of TNT going off—a half a kiloton. Neighborhood-level destruction. 4/

In the film, JRO mentions the 1917 Halifax disaster as a comparable - and indeed that was the largest human-made explosion prior to Trinity. Here it is on the chart: almost 5x the blast that Beirut was.

It's already hard to imagine things at this scale, but maps can help. 5/

But even if Halifax gives us a useful example, we have to stretch again to grasp the Trinity test: 5x the strength.

At 22 kt, the very earliest nuclear weapon easily overshadows Beirut, Tianjin, and Halifax. This was effectively the same bomb that was used to attack Nagasaki. 6/

Side-note, the fireball in the film is wonderfully artistic, but not all that accurate. Trinity was a hard event to film (nobody had ever done it before), but here's a somewhat later nuclear test which captures the terrifying ground-effects clearly. 7/

The bomb used to attack Hiroshima was a "gun-type" design, also mentioned quickly in the movie. It was a little less powerful at ~16 kilotons, but you've probably seen the devastation there—how far it reached, how much was gone. To say nothing of the radiation effects. 8/

But for about 6 years, Oppenheimer's preference of pursuing fission-only bombs held. The US built many models of nuclear bomb from 1945-1952, mostly more powerful than those first ~20kt bombs developed at Los Alamos. The strongest fission-only bomb at 500kt (!) was the Mk-18. 9/

All the while, as shown in the film, Teller was convinced of the technological feasibility of fusion—aka thermonuclear or hydrogen bomb, the "Super." Theory was that a fission bomb released enough energy to cause lighter elements to fuse, releasing much, much more in turn. 10/

And Teller was right. Despite JRO's reluctance about feasibility (tbf the first thermonuclear bomb in 1952 basically required a building and it took some time to miniaturize the system), fusion bombs were soon a thing—and so were blasts now in the *megaton* range. 11/

2 years later, the Mk-17 thermonuclear bomb was fielded by the USAF. The big bomb was capable of a 15-megaton blast, a true city-eraser and not much else.

With subsequent models, the warheads became smaller in form-factor, but for a long time stayed in the megaton range. 12/

Importantly, this all coincided with the world's first long-range missiles. Accuracy was much less of a problem if your warhead was so overbuilt. This would change, later, though.

(Check out @wellerstein's MISSLEMAP to learn more about that dynamic: ) 13/ https://t.co/r8mcYxW5DXnuclearsecrecy.com/missilemap/

Anyway, this is why the Teller argument was important during Oppenheimer's tenure at Los Alamos. When the USSR exploded its fission bomb in 1949 and Strauss and the AEC had that emergency meeting, you can see them circling radii on maps to think this all through. 14/

Strauss' argument, and that of a lot of civ-mil power brokers, was that going from nuclear to thermonuclear bombs would keep the US in "the lead" against the Soviets. JRO believed an arms race was a dead end when it comes to deterrence, and the film shows where that got him. 15/

Of course, today we have the thermonuclear bomb and at least for the US, exclusively the thermonuclear bomb in our arsenal. The models have been greatly slimmed-down in both size + strength as missiles got more accurate, but we're still talking hundreds-of-kilotons for most. 16/

Even given all this setup, it's still really hard to wrap one's head around the fact that the B83, the strongest weapon the US has today at 1.2MT, is ~20x less powerful than one we built 50 years ago.

...and yet still it's enough to kill millions in a single breath. 17/

There are a lot of points to make here ofc, but I think the biggest one that stands out is rooted where we started: it's really, really hard to grasp just how powerful these things are. It's way too easy to lose perspective, to forget that we're talking about whole cities. 18/

This is a particular dilemma for policymakers, who do have to balance effective ways to maintain deterrence (we can't have a single mistake there) with public perceptions of safety and security.

And to not again indulge the instinct to start a terribly dangerous arms race. 19/

We're losing that last point now, frustratingly.

One of the counterintuitive things about nuclear weapons is that smaller bombs (closer to Trinity-sized) are *destabilizing* in that they're seen as more usable in a pinch. It's complicated. 20/ thebulletin.org/2023/07/a-new-…

Also before I go, most of the charts and such from this thread are from my lecture on this topic! Feel free to check it out, peruse the maps, and ask any Qs. 21/21 docs.google.com/presentation/d…