Home page Interviews


Originally published in “Tuttoscienze” of “La Stampa”, 2 October 2002

In the enterprise of the Manhattan Project for the development of the atom bomb, which according to its director Robert Oppenheimer transformed scientists into “shatterers of the world”, “the one who paused was Joseph Rotblat”, who left the Project. However, after that “pause”, the nuclear physicist Rotblat did not take one day of rest at all. Lively and extremely lucid, at 93, he still works in Pugwash, the movement which he founded in ’57 with other eminent scientists, and with which in 1995 he shared the Nobel Prize for Peace for their efforts in the promotion of nuclear disarmament. He gave us this interview from the base of Pugwash in London. And as he tells us the astonishing story of the first experiments of nuclear fission, one century of physics and history unfold in his room which is full of black and white photos.

How were you “enrolled” in the Manhattan Project?

The idea of the bomb occurred to me early in 1938, in Poland, my native country. I knew about the discovery of fission, and since I had my own experiment ready, I soon verified that when the atom of uranium splits up in two parts, in the fission process, some neutrons are also emitted. And this opened the possibility of a chain reaction, in which many fissions take place and a large amount of energy is also released in a very short time, and this means a mighty explosion. However, I decided not to think about this possibility: I abhorred the idea. And also when I went to work in Liverpool with Chadwick, the physicist who discovered the neutron, I still rejected it, even if I was worried because the German publications mentioned the possibility of an atom bomb. But when the war broke out, I had to put aside my moral scruples: I went to Chadwick and I suggested to him that we begin to work on the bomb. I reasoned according to the principle of deterrence: if Hitler could acquire the atom bomb, the only way to prevent him using it against us was that we also had the bomb and could threaten retaliation. We began to work in November 1939, and when the Americans started the Project, in 1943, some of us were “enrolled”.

What was your role?

I had to establish the energy of the neutrons emitted by the nuclei of uranium in the process of fission. In the nuclear reactors for the production of energy, the neutrons are slowed down to control the chain reaction and to avoid the explosion, whereas for the bomb, we need fast neutrons, and we had to establish, first of all, their energy.

What happened when scientists discovered that Hitler didn’t have the bomb?

Actually, at that point I was not anymore in Los Alamos. I left as soon as I learned that the Germans had given up with the bomb. Chadwick, who was the head of the British project, had contacts with the Intelligence, they were friends and he knew about my moral scruples; in November 1944, he told me that he had just received the news. Actually, the Germans had given up in 1942, but we didn’t know at all. The information was confidential, the other scientists didn’t have it, and I was the only one who left the Project.

The Manhattan Project was a top secret project supervised by General Groves, the builder of the Pentagon. How was it possible for you to leave?

I had great difficulties. They even suspected that I was a Russian spy and one of the conditions for letting me go was that I had to tell no one the reason why I was leaving.

And was Groves really terrible?

He was a military man. However, I was shocked by his views. He was quite friendly with Chadwick, and during a private diner he said: “You realise of course that the main purpose of the Project is to subdue the Russians”. That was in March 1944: the Russians were our allies and we were working against Hitler. Imagine my shock! And when I told my colleagues, they didn’t believe me!

Who had a clear idea of what was happening in the Project?

Primarily Chadwick; Bohr almost prophetically realised that if the Americans and the British built the bomb by themselves, excluding the Russians, the Russians would try to build their own atom bomb, thereby triggering a dangerous arms race, which, according to him, could be avoided only through a common approach to the utilisation of the nuclear energy, both for peaceful and military purposes. We talked a lot in Los Alamos, and I knew about the problem from him. But when he spoke with Churchill, all Churchill could understood was that Bohr wanted to give away secrets to the Russians and thus he was a dangerous person, so all Bohr’s project effectively collapsed. The course of history could have been changed.

After you left the Project, you co-founded Pugwash the principal goal of which is the elimination of nuclear weapons. What is your strategy?

We work on effective treaties of elimination, that is, on treaties which will be binding on the governments who signed them. Such treaties exist already for the other weapons of mass-destruction, namely chemical and biological.

The principle of deterrence dominated 60 years of strategic world policy. Whit what can it be substituted?

With negotiation. Take Europe, for centuries disputes had been solved with terrible wars. Today, the idea that France and Italy could have a war is inconceivable. The impossible became possible. And if it happened in Europe, it could happen also somewhere else.

After September 11, you wrote to “The Times” warning about the possibility of terrorists acquiring nuclear weapons. Given the level of expertise, money and technology required for these weapons, do you think this is a real possibility?

Yes, it is not exaggeration. The “Gun method” of detonation, used in the Hiroshima bomb, is very simple. For a group of terrorists who have resources, which probably include scientists, technology is not a problem. Neither is the material a problem. For the Gun, you need uranium 235. It is very simple, if you have enough money, to acquire it: you only need 40 Kilos and in Russia there are 1000 tons. You can transport into another country, put it into a garage and detonate by remote control.

Bush and Putin agreed on a substantial reduction in nuclear arms. Does this make you feel more confident?

I welcome every cut, but this is not real. They don’t destroy arms, they only put them into a storage and, if they need them, they them pull out. It’s a sham.