Speaker Spotlight
Professor Frank Close
Frank Close OBE FRS is Professor Emeritus of Theoretical Physics, and Fellow Emeritus at Exeter College, University of Oxford. He previously served as Head of the Theoretical Physics Division at the Rutherford Appleton Laboratory, Vice President of the British Science Association, and Head of Communications and Public Understanding at CERN.
In 1996, he received the Kelvin Medal from the Institute of Physics for his outstanding contributions to the public understanding of physics. He was appointed an OBE in 2000 for services to research and public engagement with science, and in 2013 was awarded the Michael Faraday Prize for science communication by the Royal Society. He is also the only professional physicist to have won the British Science Writers Prize three times.
In this Speaker Spotlight, Frank Close, Emeritus Professor of Theoretical Physics at the University of Oxford, previews his talk Destroyer of worlds: the prequel and sequel to Oppenheimer on 31 March. He shares the serendipities, myths, and monumental effort behind the atomic age – and why understanding the full story matters more than ever.
"Had WW2 not led to the atomic bomb, and made the “destroyer” aspect so visible, the lifesaving use of targeted radiation is what nuclear physics would be best known for."
How close was history to missing the discovery of radioactivity entirely?
Three pieces of serendipity led to the chance discovery of radioactivity by Henri Becquerel in Paris, in February 1896. First, he thought X rays were linked to fluorescence - the ability of minerals such as some uranium salts to glow in the dark after first being exposed to light. They aren’t, but uranium was the first piece of his good fortune. Second, due to bad weather in Paris during January, Becquerel couldn’t expose his uranium to sunlight. After three weeks he decided to proceed anyway; he took the uranium out of the desk drawer, where they had been hidden together with some photographic plates, and discovered that the plates were fogged: uranium radiates energy even in the dark! Added to which the smudge was so faint it could easily have been missed. So began a scientific detective story: what is radioactivity; where does it come from and how can we make use of this source of energy?
Which myths about the atomic age obscure the real story of scientific discovery?
During the 1930s the atomic nucleus was explained as made of two particles - electrically charged protons and their neutral twins - neutrons. In 1934, Marie Curie’s daughter Irene and her husband Frederic Joliot discovered how to modify the arrangement of these particles and create novel combinations that are radioactive. For the first time a means of liberating useful energy from the atomic nucleus had been found. Today, this is used in medical diagnostics, PET scans and many other applications. Nuclear radiation in the right place is a lifesaver; in the wrong place it’s a destroyer. Had WW2 not led to the atomic bomb, and made the “destroyer” aspect so visible, the lifesaving use of targeted radiation is what nuclear physics would be best known for.
How did World War II transform nuclear science’s goals and pace?
One aspect is implicit in the answer to question 2: it made nuclear physics appear “bad” and obscured the vast amount of “good” that nuclear science can do. The discovery of nuclear fission of uranium in 1938 and of the chain reaction led to the theoretical possibility of an explosive release of energy. In practice a bomb is not so easy - contrary to an impression in the Oppenheimer film that its hero foresaw the weapon within hours of fission’s discovery. Chain reactions occur only in a rare form of uranium known as U235; “normal” uranium, U238, is not explosive. To make a weapon requires “enriching” uranium - making nearly pure U235. This turned out to be a vast industrial process, requiring the collaboration of thousands of scientists and engineers, plus the industrial might of the USA. Where before the war scientific research had been done by individuals or collaborations of two or three people, post war “big science” took over with international collaborations now commonplace.
Hiroshima atom bomb cloud, believed to have been taken about 30 minutes after detonation of about 10km (6 miles) east of the hypocentre.
Hiroshima atom bomb cloud, believed to have been taken about 30 minutes after detonation of about 10km (6 miles) east of the hypocentre.
What does the Manhattan Project reveal about the gap between scientific possibility and practical achievement?
Leading on from the previous question: In 1939 Niels Bohr, the greatest theoretical atomic physicist of his time, pointed out that uranium and a chain reaction aren’t enough to make an explosion for if it were, then the rocks of the earth, which contain uranium, would be detonating all the time when hit by cosmic rays or by the effects of natural radioactivity. He pointed out the potentially explosive form, “U235”, is less than 1% of naturally occurring uranium, making the rocks safe. To produce a bomb from pure U235 Bohr foresaw would require the dedicated attention of an entire nation and its industrial complex. He judged this would make a weapon impractical. The size of the Manhattan project proved Bohr right, as regards the immense effort required, but he was wrong that it would be unachievable. Unknown to Bohr and everyone at that time was the key discovery made in Birmingham by two Jewish émigré physicists - Rudolf Peierls and Otto Frisch: you only need to make a few kilograms of U235 to make an atomic bomb. That key insight is what started the secret R&D that evolved into the Manhattan Project.
How crucial was knowledge transfer in the USSR getting the bomb so quickly?
It has been estimated that it saved the USSR 18 months to 2 years. My judgment is that that is a fair estimate. Much scientific research involves chasing false trails, in a sophisticated form of trial and error. Thanks to information from spies, the USSR was able to bypass many of the errors because they had in effect been provided with a route map. When the first atomic bomb was tested, in the New Mexico desert on 16 July 1945, spies sent the blueprints of a working bomb to Moscow. From this point on the Soviet Union knew precisely what it had to do to make a bomb.
What’s the biggest public misunderstanding about nuclear science from 1896 to 1962?
That waste from nuclear power stations is more dangerous than from conventional power. Half-life is the measure of how long a sample takes to give up half of its latent radioactivity. Materials with short half-lives, which are potentially hazardous, need only to be contained for a short time before they are effectively impotent. Conversely, half-lives of thousands of years, which give an impression of the planet being contaminated by intense radiation in perpetuity, are dribbling their energy out so slowly that on any sensible timescale they cause little danger. For example, something with an infinite half-life is effectively stable.
Psychologically there is the “air crash” phenomenon. Air crashes are relatively rare and make headlines; meanwhile thousands are killed on the roads and aren’t given the same prominence. Likewise, a handful of nuclear events - Windscale, Three Mile Island, Chernobyl - make headlines but the numbers affected are insignificant relative to those suffering from industrial pollution.
"Much scientific research involves chasing false trails, in a sophisticated form of trial and error."
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