However as physicist Frank Shut explains on the HistoryExtra podcast, this story started lengthy earlier than wartime Los Alamos. It started in Britain, and it started with the query: what if the Nazis acquired there first?
“There isn’t a defence… apart from to have one your self”
In early 1939, information of a startling discovery had begun to ripple by way of the worldwide physics neighborhood.
In Germany, scientists Otto Hahn and Fritz Strassmann had proven that bombarding uranium atoms with neutrons might trigger them to separate – releasing large quantities of vitality.
The implications had been apparent to physicists. When a neutron hits a uranium nucleus, the atom splits and might emit extra neutrons. If these neutrons strike different uranium atoms, a series response begins – every fission releasing warmth and radiation.
Harnessed and managed, this new analysis created a theoretical pathway to growing a weapon able to unimaginable destruction. However might it truly work?
In Britain, two physicists – Otto Frisch and Rudolf Peierls, each refugees fleeing from the clutches of Nazism – determined to analyze.
“Frisch and Peierls did the calculation,” Shut explains, “and found, to their shock and horror, that you simply solely wanted to make concerning the dimension of a grapefruit of uranium-235, and that may have an explosive energy equal to a thousand tonnes of dynamite.”
A weapon that dimension may very well be delivered by a single bomber, but do the identical harm because the Allied firebombing of Dresden inflicted in the course of the finish of the warfare, a number of years later – a marketing campaign that concerned lots of of plane over a number of nights.
“There isn’t a defence towards such a weapon apart from to have one your self,” says Shut. “And so they suppose: what if the Nazi scientists have already realised this themselves? May Germany be constructing a bomb proper now?”
It was that terrifying prospect that triggered the race to construct the bomb.
Oppenheimer: father of the bomb, or midwife?
Thanks partly to Christopher Nolan’s 2023 movie Oppenheimer, J Robert Oppenheimer is now essentially the most recognisable face behind the event of nuclear weapons. However Shut argues that this distorts the timeline – and overlooks Britain’s foundational function.
In truth, by the point america entered the warfare in December 1941, British scientists had already achieved a lot of the important thing theoretical work. “Oppenheimer is commonly described as the daddy of the atomic bomb,” Shut provides. “[But] I feel he was the midwife of the atomic bomb – not the daddy.”
Tube Alloys: Britain’s top-secret bomb venture
In 1940, with Nazi bombers looming over British cities and the specter of invasion ever-present, Frisch and Peierls’ findings prompted rapid motion. The British authorities launched a secret atomic programme, beneath the bland-sounding codename Tube Alloys.
“This was a secret that was taken motion on solely in the UK,” Shut says. “And it started a venture pursuing methods of enriching uranium.”
That meant isolating uranium-235 – the uncommon isotope that would maintain a series response – from uranium-238, which was extra considerable however didn’t assist fission. Pure uranium incorporates simply 0.7 per cent uranium-235.
British scientists centered on a technique known as gaseous diffusion, wherein uranium fuel is handed by way of a sequence of membranes to steadily improve the focus of U-235. It was technically demanding – however in concept, doable.
At this level, america, nonetheless impartial, noticed nuclear physics as a area for peaceable analysis – a method of growing new vitality programs moderately than weaponry.
British science meets American business
That quickly modified. As Nazi victories mounted and Britain stood alone in Europe, Winston Churchill sought deeper scientific and navy cooperation with america. In September 1940, a delegation of British scientists crossed the Atlantic armed with technical briefings – together with key knowledge on uranium enrichment.
The collaboration took on a brand new dimension, nonetheless, following the Japanese assault on Pearl Harbor on 7 December 1941. The US entered the warfare the next day, and British concept mixed with America’s huge industrial capability. By 1943, British physicists together with Rudolf Peierls had relocated to the US to assist construct enrichment crops at Oak Ridge, Tennessee.
“That turned the massive laboratory the place the uranium-235 was created, which ultimately turned the gas of the bomb that was dropped over Hiroshima,” Shut explains.
Trinity and the 2 bombs
Whereas work on the uranium bomb superior, scientists additionally pursued a second design utilizing plutonium – a man-made ingredient created in nuclear reactors. Not like uranium-235, plutonium required a extra advanced implosion mechanism to set off detonation.
To show it will work, they constructed and examined a prototype. The end result was the Trinity check, carried out in New Mexico on 16 July 1945.
“The Trinity check was the second they examined the plutonium weapon,” says Shut. “And it certainly exploded. That was when the atomic age actually started.”
A couple of weeks later, two bombs had been dropped: Little Boy, a uranium bomb, on Hiroshima; and Fats Man, a plutonium bomb, on Nagasaki. Japan surrendered quickly after. The Second World Warfare was over, and the nuclear age had begun in earnest.
As for the scientists engaged on the venture, the stark actuality of what they’d created turned instantly apparent. “They realised they’d found a totally new weapon of warfare.”
An ethical gamble within the fog of warfare
Ultimately, Germany and the opposite Axis forces by no means constructed a bomb. Whereas some Nazi physicists investigated fission, they by no means made the identical conceptual leap as Frisch and Peierls. Nor did researchers in Japan or Italy.
The one different scientists who got here to the identical insights had been within the Soviet Union – and their analysis was stored secret for many years.
However none of that was identified in 1940. And, as Shut argues, that uncertainty – the paradox as as to if the enemies of the Allies additionally possessed this horrible energy – meant they had been confronted with an unenviable dilemma: what if we don’t act, however they do?
Frank Shut was chatting with Matt Elton on the HistoryExtra podcast. Take heed to the full conversation.