Who Invented the Atomic Bomb?

Interestingly, Albert Einstein, who in 1905 predicted the equivalence of matter and energy, and Leo Szilard, who invented the nuclear chain reaction in 1933 and patented it in 1936, co-authors of the letter to U.S. president Franklin Roosevelt warning of the prospect of a uranium bomb and urging the U.S. to launch its own uranium project, had previously collaborated on the invention of the Einstein-Szilard Refrigerator, which they jointly patented in 1930.

There are a number of howlers in the pop-up illustrations in this video, but the narration is correct.


Major grains of salt over the author’s and Szilard’s possible ignorance of patent law and possible oddities of ancient UK patent law:

On July 4, 1934 Leo Szilard filed a patent application for the atomic bomb In his application, Szilard described not only the basic concept of using neutron induced chain reactions to create explosions, but also the key concept of the critical mass. The patent was awarded to him - making Leo Szilard the legally recognized inventor of the atomic bomb.

Szilard did not patent this prescient and tremendously important idea for personal gain. His motive was to protect the idea to prevent its harmful use, for he immediately attempted to turn the idea over to the British government for free so that it could be classified and protected under British secrecy laws.

Emphasis added.


It appears to be:


More Szilard:

Author’s page not updated for a while:


An excellent resource on the history of intellectual property law, patents, military secret classification, and nuclear technology is Alex Wellerstein’s 2021 book, Restricted Data: The History of Nuclear Secrecy in the United States. Although, as the subtitle indicates, the focus is on the U.S., there is discussion of the bumpy road in relations between Britain and U.S., which agreed to full co-operation and information sharing when Britain turned over its work on atomic energy to the U.S. for free and then was stiffed by the U.S. after the end of World War II to such an extent they needed to independently develop their own thermonuclear bomb.

Restricted Data tracks the emergence of the doctrine of “born secret”, where certain kinds of information, even if developed independently with no government involvement, would be immediately declared secret with access denied even to the inventors if they did not possess the required clearances. Along with this was the mandatory licensing of patents on such technologies to the U.S. government. Pulling the other way were the “Atoms for Peace” program and the desire of scientists for international collaboration on non-weapons aspects of nuclear technology such as magnetic confinement fusion energy.

Alex Wellerstein operates Restricted Data: The Nuclear Secrecy Blog, which publishes infrequent but deep dive articles on all aspects of nuclear weapons history and technology.


I have an adjacent question: Why is the Einstein-Szilard refrigerator not mass produced and sold? I suspect that with modern materials, it would favorably disrupt the market (and be “green” to boot).


The main reason is that it was less efficient than electric-powered compressor-based refrigeration cycles, especially after chlorfluorocarbon refrigerants (Freon) became available. The lack of moving parts made it more inherently reliable and the ability to use, for example, bottled gas as the heat source made it attractive for remote areas without electricity. On the other hand, it required three working fluids: water, ammonia (which is toxic), and butane (flammable and, mixed with air, explosive).

Ammonia is an excellent refrigerant gas, and is used on the International Space Station to reject as much as 70 kW of waste heat to space through the large external radiator panels. Inside the station, there are monitors to detect ammonia leaks, which could, if not controlled, render the station uninhabitable.


Aren’t pentane and propane expanding in use?


Wasn’t this prompted at least in part by retribution for Britain vetting Klaus Fuchs, who turned out to be one of the Manhattan Project spies?


The timing doesn’t work for that. The sharing of nuclear technology with other countries, including World War II allies who were active participants and contributors to the Manhattan Project, was terminated by the Atomic Energy Act of 1946, also called the McMahon Act after its U.S. senator author. The McMahon Act was introduced in the senate on 1945-12-20, passed unanimously by the senate on 1946-06-01, passed by the house on 1946-07-20, and signed into law on 1946-08-01.

At that time, Klaus Fuchs was employed at the Los Alamos Laboratory in the theory section with the highest of security clearances. In May 1946 he filed a patent along with John von Neumann on using a fission trigger to ignite thermonuclear fusion in a weapon. He continued to work at Los Alamos into 1946 preparing for the Operation Crossroads (Bikini Atoll) tests. After the enactment of the McMahon Act, he returned to Britain where he headed the Theoretical Physics Division of the Atomic Energy Research Establishment until 1949. It was only then that Venona decrypts identified Fuchs as a Soviet spy, leading to his arrest on 1950-02-02. (He served nine years in prison in Britain and, upon his release, emigrated to East Germany where he lived the rest of his life.)

Thus, Fuchs’ espionage did not contribute to passage of the McMahon Act, but the defection of Igor Gouzenko to Canada in September 1945 and the subsequent arrest of 22 people he identified as Soviet spies, including British atomic scientist Alan Nunn May, contributed to its enactment. May, however, worked mostly on reactors and knew little of weapons design.

The McMahon Art was viewed as a betrayal and major affront by the British, who had been assured (along with Canada) of full sharing of nuclear energy and weapons information in the 1943 Quebec Agreement and (bilaterally between the U.S. and U.K.) in the 1944 Hyde Park Agreement. It particularly galled Britain that they hosted U.S. Strategic Air Command nuclear-armed bombers since 1948 (thus becoming a Soviet target), but were denied information on the weapons they carried.

In 1954, the U.S. congress amended the McMahon Act to allow information sharing and in June 1958, the 1958 US–UK Mutual Defence Agreement restored sharing of nuclear weapons information.


I have read (don’t remember where) that the HUAC - active beginning before the years in question and continuing after - turned out to be substantially correct in alleging many Soviet spies in the US government. One would never know from the “official”, politically correct historical point of view that there were any such spies at the time. McCarthy and the HUAC are universally despised. Now, as to tactics, it was despicable, but as to basic assertions, as borne out by release of documents following the collapse of the USSR, the substantive allegations were considerably correct.


An excellent recounting of the revelations of what was going on with Soviet espionage in the U.S. in the 1930s and 1940s is the 1999 book, Venona: Decoding Soviet Espionage in America, which documents the U.S. VENONA project, running from 1943 to 1980, to decrypt piles of Soviet diplomatic and intelligence traffic which had been sloppily encrypted with re-used “one-time” pads. A collection of VENONA decrypts may be read on the U.S. National Security Agency’s “VENONA Documents” Web site. All 3000 decrypted and translated documents have now been published.

An excellent revisionist biography of Joseph McCarthy informed by, among other sources, the VENONA decrypts, is M.Stanton Evans’ Blacklisted by History. The fury with which the establishment went against McCarthy after his May, 1950 speech in Wheeling, West Virginia, is instructive when pondering their bared-fangs assault on Donald Trump over a conversation regarding Ukraine.