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the laser
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(Light Amplification by Stimulated Emission of Radiation)

We are used to the existence of lasers in all kinds of user-friendly areas of life. Their bright beams entertain us in light-shows or by operating our CD players; they scan bar codes when we shop, heal us in the operating theatre, or help us print from our computers.

The first laser was built in 1960 in a civilian laboratory. Between 1959 and 1965 about $100 million was directed to civilian laser research – by the US Department of Defence. The Pentagon had foreseen the use of lasers in range-finding, highlighting military targets, and surveillance techniques, some of them from space. It was the military’s drive towards newer, smarter ways of making war that drove laser research projects.

In 1967 the Atomic Energy Commission, which already controlled the data generated by its own laboratories, asserted that certain researches in other laboratories should also be kept, by law, from publication.

Many scientists objected. Margaret Mead, then Chair of the Committee on Science in the Promotion of Human Welfare, called the AEC’s proposals ‘an unprecedented infringement of academic freedom’ and free scientific enquiry”.

Since the proscribed list was itself classified information, no-one knew which projects were secret. So a few months later the AEC issued a further statement. This referred to restricted data ‘concerning atomic weapons and nuclear explosive devices, including lasers and laser systems’.


The reason for secrecy became clear: thermonuclear fusion reactions (H-bombs) could be set off by lasers. Until then stockpiled hydrogen bombs had relied on atomic triggers based on expensive uranium; only a few countries could afford them. But with relatively inexpensive lasers, other governments could find the road to nuclear weapons opening up before them. Laser-triggered hydrogen bombs could be made in much smaller plant, and secretly underground.

The AEC did not want to share information that might benefit foreign laboratories; scientific discovery was once again to be kept out of the public domain for military reasons.

H-bombs have a lower profile these days, but laser weapons have a high one. Now, fearing possible missile threats from the near and middle east, the Ministry of Defence wants to follow America in setting up a ‘curtain’ of lasers which can target and destroy a missile soon after launch. A former adviser to the MoD has pointed out that the UK cannot afford to set up such a system on its own: the whole of Europe has to be involved. A new kind of escalation is already in progress.


An excellet book about the making of the atom bomb is - The Making of the Atomic Bomb by Richard Rhodes.
Available here via Amazon Co Uk


In 1914 H G Wells published ‘The World Set Free’, in which he foresaw the liberation of atomic energy for industrial and military use. In 1933, the Hungarian physicist Leo Szilard, a refugee in London, happened to notice an article in the Times which, he said, “set him pondering”. At a meeting of scientists, Ernest Rutherford had happened to say: ‘anyone who looked for a source of power in the transformation of the atoms was talking moonshine’.

Szilard was combative by nature, and he had read ‘The World Set Free’. As he waited to cross Southampton Row, it occurred to him to work out how Rutherford might be wrong. And the idea of a nuclear chain reaction, capable of unleashing great power, came to him. ‘I didn’t see at the moment just how one would go about finding the right element, or what experiments would be needed, but the idea never left me.’

People to whom Szilard mentioned the idea (including Rutherford) poured scorn on it. Over the next few years he more or less abandoned it. But in January 1939 a number of things happened.

The Austrian physicists Lise Meitner and her nephew Otto Frisch (soon to become head of nuclear physics at Harwell) had perceived the existence of nuclear fission. Frisch said ‘I felt like someone who has caught an elephant by the tail’. He shared his news with the Danish physicist Niels Bohr. Bohr, about to sail for America, promised to say nothing until the discovery was officially published; but a Belgian colleague, Léon Rosenfeld, was travelling with Bohr, and they spent the voyage thinking about how the uranium atom could be split. Rosenfeld, thinking that Frisch’s report was already in print, eagerly announced it to the Princeton physics department at just about the same time that Frisch was posting his article in a Copenhagen letterbox.

Eugene Wigner, another Hungarian physicist, was in hospital with jaundice when he heard from Princeton that a chain reaction was possible; he relayed the news to his friend Leo Szilard, visiting from New York. ‘All the things which H G Wells predicted,’ said Szilard, ‘appeared suddenly real to me.’

Now he wanted to convince other people of his fear that a possible chain reaction – an atomic explosion – meant a possible atomic bomb. Now that war in Europe was beginning, American researches should be kept secret: then no bomb-making need be attempted. But the information was already travelling fast – like the virus that sent Szilard to bed when he got home.

It was not until July 1939 that Szilard and Wigner drove to Long Island to ask support from America’s most famous guest: Albert Einstein. Lost and about to give up, Szilard spotted a small boy and, almost as joke, leant out of the car and asked if he knew where Professor Einstein lived. The child did know, and took them there.

Einstein, persuaded by Szilard’s fears, wrote his now famous letter to President Roosevelt. It was, he said, ‘now possible to set up a nuclear chain reaction in a large mass of uranium’ which could lead to the construction of an “extremely powerful bomb of a new type”; and Germany, also equipped with physics laboratories, was already known to be protecting its uranium supplies.

After the war Einstein said, “If I had known that the Germans would not succeed in constructing the atom bomb, I would never have lifted a finger.” But his letter had set off a chain reaction of its own. Without consulting Congress, President Roosevelt set in motion the unstoppable colossus called the Manhattan Project, and all that has followed from it.

One cold December day in 1942 the Italian nuclear physicist Enrico Fermi set in motion the first large-scale practical experiment in nuclear fission. It was a success: for the first time energy had been released from the atomic nucleus, under human control.

Eugene Wigner said, ‘We had known that we were about to unlock a giant; still, we could not escape an eerie feeling when we knew we had actually done it. We felt, I presume, as everyone feels who has done something that he knows will have very far-reaching consequences which he cannot foresee.’ Leo Szilard was there too. Afterwards he found himself alone with Fermi. ‘I shook hands with him, and I said I thought this day would go down as a black day in the history of mankind.’

Szilard was certain that testing and using bombs was a terrible mistake. When he and Einstein tried to say so in 1945, the new President told them that Congress would not want $2 billion to have been spent with no result. Szilard got up a petition, signed by 67 scientists; but it never reached Truman. The bomb was dropped on Hiroshima on August 6; and researches into making the even more destructive hydrogen bomb were already well advanced.

Moscow only took an interest in physics when spies learned what was happening at Los Alamos. Soviet physicists suddenly found themselves being offered urgent encouragement and facilities they had never dreamed of. Drawn into the military/scientific net, eager to meet intellectual challenges, many turned a blind eye to Stalin’s harsh régime. (They did not know Stalin had said, ‘leave them in peace. We can shoot them later.’) Believing they were in control, the physicists were prisoners in their own well-equipped gulag. In fact they were to stay there, researching for new and more advanced weapons, and taking the first steps towards the possibility of ‘star wars’.

We are all living with these chain reactions still.




 Thu, Feb 6, 2003


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