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Suppose a message was sent to the past with a diagram, description, and use, of the simplest fission weapon.

It didn't describe how to mine Uranium, enrich it, or even a description of WHY it works or atomic theory, but did indicate "U235 (and indicate element 92) needed to be separated and concentrated from U238".

If the USA or another superpower got the message, took it seriously, and wanted to build it, how early could humans have achieved this? Given that explosives, mining, atomic theory, and industry was pretty well along in 1900, I'd think 1900 or earlier. I suspect a sufficiently large enrichment plant would be the tricky part.

Leon Frickenschmidt
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    In 1900 nobody had any idea that isotopes existed; which is to say, they didn't even know that a chemical element might have more than one atomic species. They wouldn't have known that there was anything to separate. It was only in 1913 that Frederick Soddy showed that there were indeed multiple species of atoms with the same chemical properties. (He got a Nobel prize for this.) The first large-scale isotope separation facility was built during WW2, specifically for the purpose to make an atomic bomb, at considerable expense. – AlexP Jun 29 '22 at 22:20
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    "Considerable expense" is perhaps putting it lightly. The Manhattan project borrowed fifteen thousand tons of silver from the treasury for the centrifuges alone... centrifuges that also couldn't have been constructed much earlier than they were. – jdunlop Jun 29 '22 at 22:46
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    Yea, this is a material science issue, like Babbage's inability to cut gears with enough precision to make his difference engine work. As a rough estimate, if a person showed up in 1800 with all of the knowledge to build a nuclear bomb, he might crank one out in about seventy years, but he'd have to become an industrial magnate in order to gather the resources. – Robert Rapplean Jun 29 '22 at 22:55
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    I think it's a really interesting question - but, yes, I agree with other commenters that this probably isn't possible much before WWII. For example, building powerful enough centrifuges relies on some seriously precise engineering - if you've never seen what happens to an unbalanced centrifuge, it's definitely worth looking up on youtube – lupe Jun 29 '22 at 22:57
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    @jdunlop: The funny thing is that the centrifuges failed and centrifugal separation was abandoned for the Manhattan Project. (Only after the war was the Zippe centrifuge invented -- in the Soviet Union by German prisoner engineers! The Americans got the design from one of the POWs when he was released in 1956.) The isotope separation for the Manhattan Project was eventually done using mainly gaseous diffusion and electromagnetic separation. – AlexP Jun 29 '22 at 23:03
  • @AlexP - centrifuges we’re worked on early in the project, but set aside since other approaches were deemed more likely in the short term. – Jon Custer Jun 29 '22 at 23:34
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    @jdunlop - I think you mean the Calutrons, which urge silver as wire for the magnets. – Jon Custer Jun 30 '22 at 01:24
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    Related (almost full duplicate): Nuclear weapons with 1850s technology – Alexander Jun 30 '22 at 05:41
  • @jdunlop: The calutrons used the silver wire, not the centrifuges. The calutrons were used instead of centrifuges to separate the isotopes. – JRE Jun 30 '22 at 12:56
  • It is questionable whether this information would have had any impact whatsoever on when we developed nuclear weapons. We developed them when we thought that we desperately needed them, not when (or because) we thought it would be easy. And it turned out to be a lot harder than we thought. – RBarryYoung Jun 30 '22 at 16:10
  • @JRE - yep, Jon Custer already pointed that out. – jdunlop Jun 30 '22 at 16:32
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    Didn't we lose the Fundamentals of Calculus for a few thousand years because some monk decided to erase an important book? https://en.wikipedia.org/wiki/Archimedes_Palimpsest I think that could have gotten some nukes a bit faster... generally... – tuskiomi Jun 30 '22 at 16:48
  • I'd argue that calutrons are more complex and expensive that centrifuges. – Alexander Jun 30 '22 at 16:57
  • @RobertRapplean One person's mind can't hold this much knowledge. He'd need to advance every industry in the world. We're probably talking in 130 years, like by 1930 over 1945, that's it. – Therac Jun 30 '22 at 18:31
  • @ZOMVID-21, He wouldn't have to know everything. Most of it he could have derived from base principals, but with prescience of key developments. An immense amount of science was held back because the established people, those who are and were the binding agents of the community, didn't pass along ideas that they, themselves, couldn't accept. – Robert Rapplean Jun 30 '22 at 20:40
  • @tuskiomi, The Method of Mechanical Theorems describes integration using a method similar to Riemann sums, which is considerably less powerful and more laborious than the methods of Newton and Leibniz. (It's also a method that's been re-discovered frequently, although rarely with the mathematical rigor that either Archimedes or Riemann brought to the subject.) – Mark Jun 30 '22 at 21:56
  • @RobertRapplean Well, if He were to not merely travel back in time, but also be anointed as the World Leader, then perhaps indeed - they could change the course of history that much. Not sure what need they might possibly have for a nuclear bomb, though. Otherwise - even as a leader of France or England or Russia, and neither of these was a democracy - they'd still miss out on most of the developments. And prescience of a few key facts doesn't equal prescience of all the blunders that predated them. Their first interference with science would change its history. – Therac Jun 30 '22 at 22:09
  • @ZOMVID-21, you have a mistaken impression of how the world works. Cornelius Vanderbilt was one of the wealthiest men in history, and he built his fortune by foreseeing improvements in transportation. He was the Elon Musk of his age. Just a solid idea of what is truly possible and a drive to make it happen are enough to make you wealthier than most countries. If Vanderbilt knew what I know, I guarantee he could have built a nuke. – Robert Rapplean Jul 02 '22 at 06:19
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    @RobertRapplean Exactly: an idea of what is possible. Vanderbilt built his fortune with steam trains, not jet airliners. Unfortunately (or fortunately), nuclear weapons without advanced materials technology are not - no more than colonizing Mars using cannonball spaceships. Millions of people today know all the physics behind how a nuke works, and still only just over a dozen countries are able to build them. – Therac Jul 02 '22 at 10:01
  • @RobertRapplean I bet some in Vietnam, Cyprus, Serbia, Iraq or Ukraine might disagree with your assessment regarding the value of nuclear weapons. Of these, only Iraq could qualify as "saber-rattling", though not extremist. Anyway, not to get political... – Therac Jul 05 '22 at 07:47
  • Just 12 years ago, Iran, an 80-million country, failed in its nuclear program again because of a virus in imported equipment. They've spent 30 years trying to get there. Other than the US, Russia and possibly soon China, the few countries who can now build nukes, still can only do so by importing specialized equipment and materials from the original nuclear powers and their allies. – Therac Jul 05 '22 at 07:52
  • @ZOMVID-21, You're making my point for me. All of the things you describe are political, not technological. The hardest part would be purifying the fissionables, and people who can't imagine a nuke wouldn't know it was worth stopping. – Robert Rapplean Jul 05 '22 at 11:20
  • @RobertRapplean No one's stopping Iran from building centrifuges and refining the fissionables. The problem is, Iran can't build the centrifuges on its own. 80 million people, high industrial economy, and they still can't do it. – Therac Jul 05 '22 at 13:23
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    @ZOMVID-21 Yes they are, Stuxnet was built for exactly that purpose as part of a wider effort: Operation Olympic Games. – Leon Frickenschmidt Jul 06 '22 at 19:36
  • Once again, you fail to understand politics. Iranian politicians gain popularity by giving the finger to the big boys. If they actually HAD the bomb, then they'd have to admit that they didn't want to use it because the international community would either disassemble their government or level their cities, depending on which of OUR political parties you listen to. – Robert Rapplean Jul 07 '22 at 06:00
  • If we could have had nukes any earlier, we would have had them. – Justin Thyme the Second Aug 12 '22 at 22:44

1 Answers1

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Probably Not Much Earlier Than We Did

The problem is less with the concept of a nuclear bomb - Enrico Fermi famously speculated as to the liberation of atomic energy for destructive purposes in the early 20s - and much, much more with the necessary materials science required to make the fissile material. It took thousands of centrifuges, billions of dollars, the accidental discovery of Teflon...

The "billions of dollars" part is also a big deal. It was \$2B to get to the first bomb's worth of material, in 1942 dollars. That would only have been $1.2B in 1900, assuming that individual tasks wouldn't cost more in real values (which they would have), but that would have been 10% of the entire GNP of the time. It's hard to imagine, barring an existential threat (which WWI was not!) a country spending an amount of money nearly impossible to contemplate on something that atomic theory didn't yet support.

You'd also need advances in mining. Chemical leaching in place of traditional smelting.

By the time the US felt it needed an atomic bomb, it already had plenty of scientists who postulated that it was possible... and had all the other tools it needed, as long as it had the motivation to spend an enormous sum of money. In 1900, it didn't have the technology, nor any of the other tools. Knowing that it was possible wouldn't magically advance those - particularly lacking the motivation.

Addendum:

Per @AlexP's comment, the centrifuges weren't even successful, though they would be eventually. But I should also point out that prior to WWII, there wasn't really a country on earth that would be called a "superpower". Prior to WWI, the United States barely had an army!

jdunlop
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    This is a great answer - I'd also add that, even with a good understanding of the atomic theory, even with the necessary uranium, it's still a pretty daunting task, involving a bunch of accidents (the demon core incident), stuff just not working, and a lot of creative solutions to work round the existing tech and materials science – lupe Jun 30 '22 at 05:18
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    Great answer, +1, but prior to WWII, there wasn't really a country on earth that would be called a "superpower"': The British empire would have been considered a superpower by the current understanding of the word. – User65535 Jun 30 '22 at 08:54
  • @User65535 true, they would definitely have had the manpower/resources necessary. – Hobbamok Jun 30 '22 at 09:10
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    @Hobbamok - they really wouldn't. The USA eclipsed them in terms of gross GNP before 1900. No one had the manpower/resources necessary. – jdunlop Jun 30 '22 at 09:11
  • @jdunlop uhm yeah they had. What they didn't have was the INDUSTRIAL capacity, which is a huge boost in GNP. – Hobbamok Jun 30 '22 at 09:13
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    @Hobbamok - that's the point. To make an atomic weapon, you need enormous industrial capacity. That is the resource you require, and the resource they lacked. – jdunlop Jun 30 '22 at 09:14
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    @User65535 - the definition of "Superpower" in common parlance is "a state that cannot be ignored on the world stage and without whose cooperation no world problem can be solved." The sun might not set on the British Empire, but there were plenty of international conflicts that did not consider their reaction. No countries went to war during the Cold War era without considering the Soviet or American reactions to doing so, which characterizes a global superpower. – jdunlop Jun 30 '22 at 09:18
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    I suspect a sufficiently large enrichment plant would be the tricky part. "When it was built in 1944, the four-story K-25 gaseous diffusion plant was the world's largest building, comprising over 5,264,000 square feet (489,000 m2) of floor space and a volume of 97,500,000 cubic feet (2,760,000 m3)." - "By 31 December 1946, when the Manhattan Project ended, 110,048,961 man-hours of construction work had been performed at the K-25 site. The total cost, including that of K-27, was $479,589,999 (equivalent to $5.57 billion in 2020)." – Mazura Jun 30 '22 at 10:27
  • @jdunlop Which 19th / early 20th century international conflicts were the British utterly irrelevant to? And was the USA a superpower before it got the bomb, or only after? It's not ludicrous to imagine the prewar UK, France, or Germany paying the equivalent of $5.57b, right? Surely the harder limit is technical, not economic. –  Jun 30 '22 at 14:15
  • It wasn't (a really never has been) the US' army that made it a superpower. It was its resources and industrial capacity. By 1915 the US was producing more iron and more coal than the rest of the world combined, and a larger GDP than all of Europe combined. It also had the world's largest oil reserves, and of course more manpower than any other industrialized nation. – T.E.D. Jun 30 '22 at 15:18
  • @SeanOConnor - the Sino-Japanese and Russo-Japanese wars had no British involvement or mediation, just as a start. And pre-which war? 'cause a country devoting more than 10% of its GNP to anything when not on a total war footing is... kind of astonishing. – jdunlop Jun 30 '22 at 16:32
  • @jdunlop I don’t know where you found that definition, but by it the world has 0 superpowers, so it’s not particularly useful. – Tim Jun 30 '22 at 17:38
  • @Tim - Britannica:

    A superpower is a state that cannot be ignored on the world stage and without whose cooperation no world problem can be solved. During the Cold War, for instance, the United States could not intervene in world affairs without taking into account the position of the U.S.S.R., and vice versa. The possession of highly superior military capabilities is generally considered to be the most important element in distinguishing a superpower such as the United States from a major power such as France or the United Kingdom.

     – jdunlop Jun 30 '22 at 17:43
  • @jdunlop The Japanese were allied with the British in the Pacific at the time of the Russo-Japanese war and trained their naval officers leading up to it as well as supplying the technology for their ships, and by balance oc power preventing the USA from coming in against the Japs. Not trivial. –  Jul 01 '22 at 09:14