Among the elegies for the inhabitants of Hiroshima, there exists an especially arresting and resonant example authored by an Australian poet.

Reflecting on the impact of the blast on one of its young victims, Bruce Dawe recounted the morning of August 6, 1945, when a "single plane loosed a single bomb" and the city below — but also the very prospect of posterity — "became suddenly phantasmal".

A suspected "human shadow" left by the vaporisation of a person at Hiroshima. (Wikimedia Commons: Matsuhige Yoshito)

When humans first split atoms, they also split history.

"The atomic bomb," wrote its chief developer, the physicist J. Robert Oppenheimer, "has led us up those last few steps to the mountain pass; and beyond there is a different country".

That different country is the age in which we now live.

Among the chroniclers who described its dawn were some astute enough to notice that fission had produced unforeseen fissures: with the advent of the bomb, human knowledge itself seemed to fracture, with science on one side and conscience on the other.

Oppenheimer was perhaps an exception to this dichotomy, and combined academic interests from both sides of the divide — erudite, sensitive and cultured, he was, in some respects, an unlikely atomic father figure.

Oppenheimer's name is currently on many a movie-goer's lips, thanks to Christopher Nolan's latest effort to render physics a suitable subject for the big screen.

Cillian Murphy stars as the eponymous central character in the Christopher Nolan movie Oppenheimer. (Supplied: Universal)

But one episode absent from the blockbuster is the meeting, with an Australian scientist, that got Oppenheimer involved with the bomb in the first place.

'The birth of the Manhattan Project'

History teems with chance encounters — instances in which human atoms collide with other human atoms, sometimes causing chain reactions.

The meeting between Oppenheimer and Adelaide-born physicist Mark Oliphant in California, in September 1941, was one such moment.

Oliphant pictured during his September 1941 trip to Berkeley, where he met with Oppenheimer and Lawrence. (Donald Cooksey/Public domain)

Fremantle-based historical researcher and geoscientist Darren Holden, who has investigated the encounter in detail, notes that it was the Australian, not the American, who instigated it.

"Oliphant's meeting brought in Oppenheimer who had, up until then, been part of the chorus line of theoretical physicists and had certainly not been involved in any applied bomb research," Dr Holden wrote in a research paper on the subject.

Darren Holden has investigated the meeting between Oliphant and Oppenheimer, and its role in the Manhattan Project. (Supplied)

By 1939, scientists were aware not only of the latent power of the atom, but of the possibility of a bomb: after the discovery of fission by chemists in Germany and physicists in Denmark and Sweden, a letter signed by Einstein was sent to US President Franklin Roosevelt, warning of unprecedented and "extremely powerful" weapons.

The following year, another major breakthrough occurred when two of Oliphant's colleagues at the University of Birmingham — Jewish refugees Otto Frisch and Rudolf Peierls — demonstrated the feasibility of a "super-bomb" using the isotope uranium-235, rather than the more plentiful but far less fissile uranium-238.

"They came up with the uranium-235 critical mass equations, that show that a nuclear bomb with uranium would be able to be constructed and able to be transported by aircraft," Dr Holden said.

Armed with this knowledge, Oliphant left Britain for America in 1941.

Amid concerns that Nazi Germany could develop such a weapon, and worried that nuclear research was languishing in the UK, he took matters into his own hands.

"He decided that he needed to act, and – I believe – without authority, in order to convince the Americans. He needed an ally," Dr Holden said.

That ally was experimental physicist Ernest Lawrence, whom Oliphant met in Berkeley with the intention of involving America — then still a neutral nation — in Allied efforts to produce a bomb.

J. Robert Oppenheimer several years after the Berkeley meeting with Oliphant. (Wikimedia: Ed Westcott/US Government)

It was Lawrence who sought the assistance of Oppenheimer, by asking him to "check the numbers" in the Frisch-Peierls paper.

"It was essentially at that point that Oppenheimer was brought in," Dr Holden said.

Remorse or pride?

The physicists who built the first nuclear weapons became, in the public imagination, demigods who had unlocked a fundamental secret of the universe to end a world war.

"Oppenheimer became a pin-up boy of American science after the war," Dr Holden said.

In books and films, there has been a tendency to depict Oppenheimer as a tortured soul. (Supplied: Universal)

But literary voices – especially those who specialised in the depiction of dystopias — were among the first to articulate the moral magnitude of what had changed.

"The nuclear scientist will prepare the bed on which [humankind] must lie," Aldous Huxley stated in a 1946 foreword to Brave New World.

George Orwell was more mordant. In a post-war essay, the future author of Nineteen Eighty-Four offered words of caution about where science untempered by moral considerations might lead:

A popular theory persists that the physicists who devised and developed the bomb were racked with guilt.

Photo shows An image combining a portrait of CSIRO scientist Hedley Marston with a photo of a nuclear test.

Hedley Marston was, in many respects, an establishment man — but when he began studying nuclear fallout from British bomb tests at Maralinga, he became incensed.

But did they really regret their involvement? Was Oppenheimer, as two of his biographers have called him, an "American Prometheus"? And to what extent is the label "Australia's Oppenheimer" a fitting description of Oliphant?

In Oliphant's case, the evidence points in different directions.

Dr Holden notes that Oliphant and Oppenheimer continued to collaborate after the war, but on a cause very different to the one that had occupied them in 1941.

"[They] worked together to try and convince the governments of the world, and the United Nations, to ban atomic weapons for everybody," he said.

Nevertheless, less than 50 years after Hiroshima, the putatively pacifist Oliphant (by then Sir Mark) remained sufficiently pleased with his work on the bomb to write a letter to The Advertiser newspaper in 1986 in which he championed the British contributions to the Manhattan Project.

In an incisive evaluation of Oliphant's legacy, Dr Holden has argued that the physicist was "naive to assume" that wartime scientific gains "would be utilised in peacetime only for the greater good", and that Oliphant "remained proud rather than remorseful of his time at the Manhattan Project".

Oliphant, Oppenheimer and the dozens of other physicists and chemists involved in the construction of the bomb thus remain ambiguous figures in the history of scientific research.

Their proximity to what was one of the most intensive, elaborate, formidable and destructive engineering endeavours ever undertaken perhaps denied them the kind of perspective afforded to non-scientists like Bruce Dawe, whose poem (quoted above) on the shadow of a Japanese child "blasted upon" a surface at Hiroshima ends with these words:

"In your blackened absence, this stencilled outline on the wall haunts us all with its unending play."