THE WORLD IS STILL far from safe from nuclear weapons. While President Obama and Russian President Dmitry Medvedev recently agreed to modest mutual nuclear weapons reductions, the North Koreans are intensifying their quest to build and test ballistic missiles, are continuing their nuclear weapons production project, and have shown no sign of giving up their push to sell nuclear technology to other nations, such as Syria.
Meanwhile, thousands of centrifuges continue to spin in Iran’s nuclear center at Natanz, bringing Iran ever closer to its goal (denied by the Iranian regime but widely believed by many governments) of producing nuclear weapons.
In Pakistan, the pace of production of nuclear bombs is reported to have picked up in recent months, raising the danger that some of these weapons could fall into the hands of fanatics.
Coincidental with these emerging nuclear threats to world security, this year also marks the 70th anniversary of the discovery of nuclear chain reaction - the scientific process that opened the way to the production of atomic bombs and launched the nuclear age in which we live.
And the devil is of our own making. In 1939, various pieces of information in about 100 scientific papers crystallized in the joint thinking of Danish physicist Niels Bohr, Leo Szilard, a Hungarian-born American scientist, Enrico Fermi, the Italian genius who had left his homeland because of fascism, and John Archibald Wheeler of Princeton, all meeting at the Columbia University faculty dining room. The foursome - perhaps the greatest meeting of brains in history - developed the idea of chain reaction of uranium fission.
They enlisted Einstein to write his famous letter to FDR urging US development of an atomic bomb, a device that exploits the process of chain reaction, to counter such possible development by the Nazis. And the rest - the Manhattan Project, which produced the bomb - is history.
But what science historians did not know until recently is how far the Germans really were from obtaining their own bomb. When I met him at Berkeley in 1972, Werner Heisenberg, who had been the chief German scientist in the Nazi atomic bomb project, did not say a word about his wartime work. But three decades later, in 2002, after public pressure brought on by Michael Frayn’s immensely successful play “Copenhagen,’’ the Niels Bohr archive in Copenhagen was forced to open its files - despite Bohr’s will forbidding the release of his letters until 10 years later - and the true picture emerged.
From these released documents, as well as the transcripts of secretly recorded conversations among 10 captured Nazi scientists, including Heisenberg, held captive on an English country estate after the Nazi surrender (recently released to archives by the British government), it became clear that the technical knowledge needed to make a bomb was far outside their reach. In addition, Hitler refused to provide financial support for this project beyond its infancy because he favored Peenemunde - the enterprise that created the dreaded V-1 and V-2 rockets that rained terror on Britain.
Other documents, based on the American “Magic’’ spying operation on Japan, were originally classified “Top Secret,’’ and “Ultra Top Secret’’ and were recently released by the US government. They show that the Japanese were seeking to surrender in the period before the atomic bombing of Hiroshima and Nagasaki.
Avoiding the immensely expensive and resource-depleting Manhattan Project - or abandoning it before completion and burying its secrets - would have prevented not only the deaths of hundreds of thousands of Japanese civilians, but arguably also the Cold War and the present alarming state of nuclear proliferation.
Joseph Stalin did not possess the resources that would have allowed him to explore making an atomic bomb on his own unless impelled to do so by American nuclear development. Neither would any other country have had the resources and know-how to make a bomb.
Once the Manhattan Project became a reality, the blueprint for a bomb had been created - in a massive scientific-industrial effort only possible in the United States - and the Soviet Union, France, Britain, China, and now Pakistan, Iran, and North Korea could follow suit without the immense effort of having to reinvent this terrible “wheel.’’ In fact, we trained some of the Iranian nuclear scientists who now work on Iranian President Mahmoud Ahmadinejad’s atomic bomb project in our own universities: Back at Berkeley in the 1970s, most of the Iranian foreign students I knew were studying nuclear engineering. I wonder how many went back to Iran to work on the bomb.
Amir D. Aczel is a research fellow in the history of science at Boston University and the author of “Uranium Wars: The Scientific Rivalry that Created the Nuclear Age,’’ to be published in September. 
