Everyone involved was confident the gun-type bomb would work. They'd tested bringing two pieces of enriched uranium close together in criticality experiments. That experiment killed several people at Los Alamos.
The big worry was it going off prematurely. When the Enola Gay took off to drop the uranium bomb on Hiroshima, their orders were that if they had to turn back, dump the bomb in deep water. A billion dollars to the bottom of the sea. That was preferable to taking the chance of blowing the airfield on Tinian off the map if the B-29 had a fire on landing.
Making enriched uranium was slow, but working. The gaseous-diffusion plant cascades were working, after months of startup. The second gaseous diffusion plant at Oak Ridge, K-27, opened in September 1945, a few weeks after the end of the war. If the war had dragged on, there would have been more uranium bombs.
>Everyone involved was confident the gun-type bomb would work.
Yes. That's why the design of the Little Boy bomb carried by the Enola Gay was only "unit tested." That's not what the Trinity test tested. The uranium gun-type bomb dropped on Hiroshima was basically a backup plan in case the plutonium-implosion design--which was the primary focus of Los Alamos during the later part of the Manhattan Project--couldn't be made to work.
And it was the plutonium-implosion design that was tested at Trinity. (And was the design dropped on Nagasaki.)
> They'd tested bringing two pieces of enriched uranium close together in criticality experiments. That experiment killed several people at Los Alamos.
The Demon core story is quite fascinating, I compiled several Wikipedia articles to construct the full narrative: https://svedic.org/history/demon-core
Anytime I'm jimmying something open with a screwdriver I can't help think of this story and how crazy dangerous holding two hemispheres of plutonium apart with a screwdriver really is.
That's a surprisingly accessible read and I would recommend it to folks curious about "what does intense irradiation do to the human body". But it's also quite haunting.
Exactly. I won’t comment on the scientists confidence, but getting a chunk of plutonium to go critical isn’t that hard.
Getting it to go critical in a consistent way is hard. Slam two sub-critical pieces together with your hands and it will go critical then blow itself apart, going sub-critical. Little energy release and more just throwing plutonium around.
> They'd tested bringing two pieces of enriched uranium close together in criticality experiments. That experiment killed several people at Los Alamos.
I thought the Los Alamos demon core was plutonium?
No.[1] It took a few years before plutonium bombs were reliable and storable. Documents of the period use the term "GI-proof". On the other hand, keeping assembled enriched uranium bombs around wasn't a good idea. For a year or two after the war, the US had zero nuclear weapons ready to go. On a few days notice, though...
A lot of people would have been very surprised if it had failed.
The physics wasn't considered a mystery by then. Failure would have been caused by fixable engineering and design mistakes - or sabotage - not because the idea was unworkable.
There might have been some completely unexpected physics at scale. But given that nuclear reactors were already a thing, that would have been very surprising.
> There might have been some completely unexpected physics at scale. But given that nuclear reactors were already a thing, that would have been very surprising.
Trinity was a plutonium device. Reactors were uranium devices. Nobody was really sure if the plutonium implosion device would work - that's why they did the test; they were very sure that the uranium bullet device, that was used on Hiroshima without testing, would work.
But some people expected that: "The observers set up a betting pool on the results of the test. Edward Teller was the most optimistic, predicting 45 kilotons of TNT (190 TJ). [...] Others were less optimistic. Ramsey chose zero (a complete dud), Robert Oppenheimer chose 0.3 kilotons of TNT (1.3 TJ) [...]" (Wikipedia)
This is right on - understanding the equation of state, in extremis, is critical in characterizing the kinetics on the way to disassembly. The metallic phases generated during implosion don't exist in a power reactor.
I think the uncertainty had more to do with the implosion mechanism than nuclear physics. The ability to simulate the hydrodynamics of an imploding sphere was obviously pretty limited in 1945, and while Los Alamos devised a series of pretty ingenious experiments to test how symmetrical such implosions could be made, for obvious reasons they had to use mock setups with metals other than Plutonium. So there seems to have been a fair amount of skepticism that such a mechanism could be made to work right up until Trinity.
That's true, but if you think about today, there are lot of things that are well understood by scientists and yet disputed by many politicians and members of the public. If the Trinity test had failed, it's not inconceivable it would have colored the leadership's perceptions of the feasibility of atomic bombs in general.
The Trinity test remains the most intellectually arrogant moment in history. The bomb could have ignited the atmosphere, turned us into another sun for reasons we didn't understand. They worried about this, and were fairly confident in their calculations. But every century of physics brings the realization we had little clue a century earlier. If the Trinity test had behaved in an unexpected way, we wouldn't be reading this. That's what I assumed the headline meant. I was disappointed.
This appears to be a misunderstanding or myth. It was well understood prior to Trinity that such an occurrence was not possible. The issue was carefully studied by multiple top physicists affiliated with the Manhattan Project.
You’re getting hammered for this, but you’re probably correct. One could imagine a parallel universe where our test didn’t go so favorably.
One could also imagine a future physics breakthrough that we’re fairly confident about, which turns out to be horribly wrong.
However, with each decade that the standard model turns out to be correct, one could also imagine that this chance will never happen again; that we’ll be forever confident in our predictions. (This seems the most arrogant statement of all, though.)
The most important kind of intelligence is knowing what one does not know. There's a mindset counter to this, that substitutes a model for reality and then fervently believes the model. Math and physics exerts a very strong selection force attracting people fond of this substitution. The responses here do not surprise me.
Our extrapolations always take the form of moving along a tangent vector out from prior experience. Prior to relativity, Newtonian physics was the belief that we actually lived in that tangent space. Surprises come when the deviations are large enough for reality to curve away from our models. I thought I understood how materials behaved, till I was stuck briefly on a mountain at -30F. People dance on decks that collapse. They smoke joints on exposed foam mattresses. Surprises happen.
I appreciate that in this universe, our experience confirmed that physicists' absolute faith in the Trinity experiment was well-founded. A billion runs of parallel universes would have likely work out. Take this out to a quadrillion runs? It turns out that alien life has always been here at the subatomic level. Like dogs not liking fireworks, that nuclear ping really pissed them off, so they engineer a virus that wipes us out. Or it turns out that indeed there's a quantum basis to consciousness. After that nuclear ping, the atmosphere is fine, but everyone on that side of the Earth keels over, no longer able to think.
The Trinity test was a step further out along the tangent vector than we'd ever taken before. We were deliberately creating a version of a Carrington Event on Earth, with absolute certainty that we understood and anticipated all consequences. The odds of calamity were small, but our existence was at stake.
Igniting the atmosphere was merely the most obvious candidate for an unintended consequence. Countering this possibility does not address the underlying problem of what we do not know. My other scenarios are obviously far less likely. Yet, Neanderthals would never have detected radio waves. What are we not detecting? Who understands consciousness? There are limits to our understanding of physical reality.
Those with unquestioning faith in our current understanding of science are no different from those with unquestioning faith in a religion. With the Trinity test, we were playing with matches.
These type of concerns are pretty meaningless IMO. If we're going to speculate about stuff like what might annoy subatomic alien life or somehow creating some kind of quantum echoes or whatever that somehow destroy all consciousness, that brings us to the point of anything at all might happen for any reason at all. For all we know, me lifting my right pinky finger a quarter inch right now will result in the entire planet just winking out of existence.
Such things get into non-falsifiability. Sure, we can never prove true or false the idea that something we aren't even aware of might exist and do catastrophic things for reasons that make no sense to us. But if we take such ideas seriously, how could we ever do anything at all? Considering such ideas can only be either pointless speculation, or a power exercise - it's very good to be the person who decides what activities have an unacceptable risk of causing catastrophically bad things to happen for inscrutable reasons, and what don't.
We're inside a balloon together, poking at it with a needle. You're off on some philosophical discourse about falsifiability. And all I'm trying to say is we've never poked that hard before, are you sure you know what you're doing?
A long time ago I saw some documentary about the ruins of the Khmer (No! NOT Ancient Aliens! Seriuosly!) where they overlaid the groundplot by LIDAR into the aerials which have shown only jungle. The thing is, that groundplot looked exactly like the planar layout of some on-die microwave emitter I've seen in some site like IEEE or phys.org a few weeks before.
I just thought as above, so below.
The older I get, the less unlikely I think of some so called
"pseudo-history".
> However, with each decade that the standard model turns out to be correct, one could also imagine that this chance will never happen again; that we’ll be forever confident in our predictions. (This seems the most arrogant statement of all, though.)
Even with a perfect model complex systems will continue to surprise us so long as our intelligence and knowledge is finite.
See software development for an endless source of examples.
I'm not following. You're suggesting they had an exaggerated sense of their own abilities? It doesn't seem they did, given they accomplished what they set out to do. And their calculations turned out to be correct w/r/t the risk of igniting the atmosphere.
It seems odd to suggest they were arrogant because they didn't have physics knowledge that wasn't available to them - or anyone - at the time.
"In the twenty-two hundred recorded points of my conferences with Hitler, nuclear fission comes up only once, and then is mentioned with extreme brevity. Hitler did sometimes comment on its prospects, but what I told him of my conferences with the physicists confirmed his view that there was not much profit in the matter. Actually, Professor Heisenberg had not given any final answer
to my question whether a successful nuclear fission could be kept
under control with absolute certainty or might continue as a chain reaction. Hitler was plainly not delighted with the possibility that the earth under his rule might be transformed into a glowing star.
Occasionally, however, he joked that the scientists in their unworldly urge to lay bare all the secrets under heaven might some day set the globe on fire. But undoubtedly a good deal of time would pass before that came about, Hitler said; he would certainly not live to see it. "
From the Making of the Atomic Bomb by Richard Rhodes. Such an amazing book, and required reading for any scientist IMO.
This is a pretty fascinating exploration into what wasn't known about the bomb prior to the test, the range of expectations about what would happen, and the various things that the test results affected.
I find it most fascinating that when Little Boy was detonated the portion of only about one kilogram underwent fission out of the total Uranium mass of 64 kg. So much destruction from such a tiny amount of stuff...
if you have never been to the nuclear science museum in Albuquerque NM is amazing... and a little surreal.
I remember walking outside to see the planes and icbms, off in a corner mixed in with some scrap was a pallet with a big metal cylinder thing. I thought it was construction equipment or just trash but, nope, it was a B41. The B41 is a 25mt air dropped bomb, the largest strategic nuke ever fielded by the US.
I had a couple moments like that at the museum. Behind a door was a bomb casing with B61 written on it with a sharpie.
these were the most destructive devices ever conceived of by man but just strewn about like what you'd find in some old timer's garage.
They got the bit about nuclear power wrong though. Fission was discovered in Germany just before WWII, which is why Einstein (the real one) was concerned that the Germans might develop nuclear weapons first and advised the US to do it. At that point it wasn't obvious that a bomb was possible even if fission was, but even if it wasn't, the application of fission to power generation would still have been obvious.
If anything they'd have probably had more nuclear power generation, because the proliferation risk wouldn't have been a concern and the scary association with city-destroying weapons wouldn't have been such a PR problem.
I really enjoyed the Manhattan series, which covered similar ground. Some reasonably accurate but dramatised scenes about viability of the bomb types and exploring how to get there, both physically and in maths. https://en.m.wikipedia.org/wiki/Manhattan_(TV_series)
"One" I think. Probably was "ne" and got autocorrected to "me" instead of "one" (would make sense, "less than me" probably occurs more often than "less than one").
TFA asks a bunch of what-if questions -- very good ones indeed.
> Would a failure at Trinity have changed the outcome of World War II in any significant way? Ultimately this question relies on what you think caused the Japanese to offer up a conditional surrender on August 10th, and then an unconditional surrender on August 14th. In particular, it depends on how important you think the Nagasaki bombing was for the decision-making of the Japanese high command.
I think it's pretty clear that a) the Japanese had been willing to surrender on one condition (keeping the emperor) for weeks, b) the U.S. was holding out for an unconditional surrender, c) the USSR entering the war pushed Japan to make, and the U.S. to accept, a privately-conditional / publicly-unconditional surrender. I believe the bombs made little real difference. From a Japanese perspective they destroyed nothing that hadn't already been firebombed to smithereens -- all large- and medium-sized cities already had been firebombed to smithereens. It's really hard to believe that the war with Japan would have had a different outcome if either or both bombs had not been dropped.
But I found this very interesting:
> After getting the successful results from Trinity, Truman took a very hard line with Stalin. He believed that the bomb gave him leverage for both the end of World War II and the peace that would follow. Though he did not try to argue that the Soviets should not declare war on Japan or stop their invasion plans, he was less convinced he would need the Soviet entry into the war, and did not encourage them.
Well! If he had been certain enough to demand that Stalin not enter the war, that might have meant we'd have no North Korea today. Interesting thought.
The mayor of Nagasaki reported that the bomb was a dud, and only then realized he'd heard nothing from the north half of the city. Same statistical paradox as the Brits reinforcing the parts of planes that returned with bullet holes, until someone said, "Um", ...
The Japanese surrendered before realizing that Nagasaki had been half destroyed.
The bomber crew was going to release on radar alone, against orders, realizing this made more sense than releasing over the ocean before landing. Then they saw an opening in the clouds. Not a good day for visibility; Nagasaki wasn't even the primary target.
>...On June 9, the Emperor's confidant Marquis Kōichi Kido wrote a "Draft Plan for Controlling the Crisis Situation," warning that by the end of the year Japan's ability to wage modern war would be extinguished and the government would be unable to contain civil unrest.
>...Kido's proposal did not contemplate Allied occupation of Japan, prosecution of war criminals or substantial change in Japan's system of government, nor did Kido suggest that Japan might be willing to consider relinquishing territories acquired prior to 1937 including Formosa, Karafuto, Korea, the formerly German islands in the Pacific and even Manchukuo.
In July, Togo told the ambassador to the Soviet Union:
>...Although the directing powers, and the government as well, are convinced that our war strength still can deliver considerable blows to the enemy, we are unable to feel absolutely secure peace of mind ... Please bear particularly in mind, however, that we are not seeking the Russians' mediation for anything like an unconditional surrender.
>In reply, Satō clarified:
>It goes without saying that in my earlier message calling for unconditional surrender or closely equivalent terms, I made an exception of the question of preserving [the imperial family].[49]
>On July 21, speaking in the name of the cabinet, Tōgō repeated:
With regard to unconditional surrender we are unable to consent to it under any circumstances whatever. ...
>...b) the U.S. was holding out for an unconditional surrender
It is more accurate to say they were holding out an acceptance of the Potsdam Declaration.
>...c) the USSR entering the war pushed Japan to make, and the U.S. to accept, a privately-conditional / publicly-unconditional surrender.
It is not like the US didn't know the Soviet Union was going to enter the war. When the Japanese government demanded that the emperor would remain in power, the reply simply was:
>...From the moment of surrender the authority of the Emperor and the Japanese government to rule the state shall be subject to the Supreme Commander of the Allied powers who will take such steps as he deems proper to effectuate the surrender terms. ... The ultimate form of government of Japan shall, in accordance with the Potsdam Declaration, be established by the freely expressed will of the Japanese people.
Eventually Japan agreed to the Potsdam Declaration.
>...From a Japanese perspective they destroyed nothing that hadn't already been firebombed to smithereens
That is basically true and had been true for months. The question is why did so many have to die in Okinawa? I think an argument can be made that the atomic bomb made it very clear to the emperor how ruinous the situation was and pointing at the bomb allowed him to save face:
>...In a meeting with the Emperor, Yonai spoke of his concerns about growing civil unrest:
>I think the term is inappropriate, but the atomic bombs and the Soviet entry into the war are, in a sense, divine gifts. This way we don't have to say that we have quit the war because of domestic circumstances.
Indeed the major reason that Hirohito publicly mentioned in his speech to the nation was:
>...Moreover, the enemy has begun to employ a new and most cruel bomb, the power of which to do damage is, indeed, incalculable, taking the toll of many innocent lives. Should we continue to fight, not only would it result in an ultimate collapse and obliteration of the Japanese nation, but also it would lead to the total extinction of human civilization.
>...It's really hard to believe that the war with Japan would have had a different outcome if either or both bombs had not been dropped.
There is no way that Japan would have "won" the war at point, but if the surrender of Japan had been delayed and the invasion occurred, there would have been many more casualties on both sides. Both sides were preparing for a horrific battle:
>...Instead, everything was staked on the beachhead; more than 3,000 kamikazes would be sent to attack the amphibious transports before troops and cargo were disembarked on the beach.[8]
If this did not drive the Allies away, they planned to send another 3,500 kamikazes along with 5,000 Shin'yō suicide motorboats and the remaining destroyers and submarines—"the last of the Navy's operating fleet"—to the beach.
On the other side:
>...Operation Olympic, the invasion of Kyūshū, was to begin on "X-Day", which was scheduled for 1 November 1945. The combined Allied naval armada would have been the largest ever assembled, including 42 aircraft carriers, 24 battleships, and 400 destroyers and destroyer escorts. Fourteen U.S. "division-equivalents" (13 divisions and two regimental combat teams)[28] were scheduled to take part in the initial landings.
and if that armada wasn't enough:
>...Ken Nichols, the District Engineer of the Manhattan Engineer District, wrote that at the beginning of August 1945, "[p]lanning for the invasion of the main Japanese home islands had reached its final stages, and if the landings actually took place, we might supply about fifteen atomic bombs to support the troops.
The published article annotated modes of failure with respect to the desired operational objective of a 5kton blast, 500 ton, various component failures, and their implications. It's written from a operational impact perspective on the war, Potsdam, and cold war implications.
Perhaps setting the atmosphere ablaze would have been an exceptional success? I remember someone telling me that this possibility was still being discussed before the Trinity test and, again, after thermonuclear bombs entered the arena. This seems to be a nice summary: http://large.stanford.edu/courses/2015/ph241/chung1/
I think they refer to the failure mode where: Nothing happened for a day or two. All the experts travel to the location to try to understand what went wrong, in situ... and THEN the explosion occurs.
This really wasn't a plausible failure mode. They had many (9?) detonators which had to be very precisely simultaneous, and had done a lot of tests of those alone (this was cheap & easy). As long as just one of them worked, you would burn all the explosives (just not in the right order) and destroy the device.
Not sure how you would quantify this, but enough? Inventing detonators that worked fast enough (i.e. small enough error in firing time) was one of the challenges. They did a lot of tests of those explosive lenses. (32, not 9, of course.)
The electronics to fire them would have comparatively easy to test well, and I'm sure they over-designed it all. I doubt that duplicating it would have made anything better.
The big worry was it going off prematurely. When the Enola Gay took off to drop the uranium bomb on Hiroshima, their orders were that if they had to turn back, dump the bomb in deep water. A billion dollars to the bottom of the sea. That was preferable to taking the chance of blowing the airfield on Tinian off the map if the B-29 had a fire on landing.
Making enriched uranium was slow, but working. The gaseous-diffusion plant cascades were working, after months of startup. The second gaseous diffusion plant at Oak Ridge, K-27, opened in September 1945, a few weeks after the end of the war. If the war had dragged on, there would have been more uranium bombs.