Dr. Hahn is not reliable of speech, when speaking of himself. He says he is not learned, not distinguished, not famous as a scientist. He sacrifices truth to modesty - and I sympathize with him in his temptation.
It must certainly be a great joy for you and Strassmann that you have made the whole world of physics excited. That is really wonderful!
Prof. Dr. Lise Meitner, Stockholm, to Otto Hahn, February 24th, 1939.
Otto Hahn's humane and scientific personality is an indivisible whole. A very lively intellectual intuition, a very sound ability, an exceptional and critical ability for observation, an unshakeable dependability and doggedness next to great inner modesty and natural kindness mark the man as they do his work.
A man of the world. He has been the most helpful of the professors and his sense of humour and common sense has saved the day on many occasions. He is definitely friendly disposed to England and America.
With his humour and his sound humanity Otto Hahn quickly gained ground at the Geneva Conference to which we other members of the German delegation became very indebted. We even went to the official Soviet reception, at which we were also able to bask in Hahn's fame. This visit took place against resistance from the Foreign Office, for the Federal Republic of Germany had no diplomatic relations with Moscow.
The discovery of nuclear fission by Otto Hahn and Fritz Strassmann opened up a new era in human history. It seems to me that what makes the science behind this discovery so remarkable is that it was achieved by purely chemical means.
The significance accorded to the outcome from the scientific point of view becomes clear when one reads in the first publication of nuclear fission that Professor Hahn, who had over thirty years of practical and theoretical experience in the sphere of radioactivity and whose judgement unquestionably commanded the greatest weight among fellow scientists both in Germany and the whole world, announced the new discovery only hesitatingly. The radiochemical methods he applied, which were partly developed by him, tested out hundreds of times in the course of thirty years, and found to be reliable, did not permit any doubt about the finding.
Otto Hahn was also in Geneva. He was small and quiet, with a retiring manner. Little tufts of thin white hair framed his face, and there was often a bewildered expression in his blue eyes, as if he were still astonished at the great things that had come from his discovery of fission.
I must emphasise, that this proof of fission with such a low presence of the identifying preparation was in actuality a masterpiece of radiochemistry, in which at that time hardly anybody else other than Otto Hahn and Strassmann would have been able to succeed.
Can one, may one, hold the researcher responsible for the consequences of his work? Everyone who knew Otto Hahn knew with what unsparing clarity he had put this question to himself. We admire him, who as a researcher in his work, just as much as a man in his thought and deed, was ever a model of uprightness and conscientiousness, and even more so by the questions and answers he raised and gave by virtue of his personal conduct.
It has been given to very few men to make contributions to science and to humanity of the magnitude of those made by Otto Hahn. He has made those contributions over a span of nearly two generations, beginning with a key role in the earliest days of radiochemistry in investigating and unraveling the complexities of the natural radioactivities and culminating with his tremendous discovery of the nuclear fission of uranium. I believe that it is fair to refer to Otto Hahn as the father of radiochemistry and of its more recent offspring, nuclear chemistry. For his special genius the world of science will be forever grateful.
Prof. Dr. Glenn T. Seaborg, President of the United States Atomic Energy Commission, Washington, 1966.
There are occurrences far removed from social and political events, let alone any sensation, and without relation to the course of history - and yet their taking place leads the world, deeply moved, to hold its breath for a moment, and people, far and wide, to halt for a moment of reflection amid the rush of the everyday: Otto Hahn, almost 90 years old, has left the world. A good, a simple man has entered his name in both the history of the natural sciences and the history of humanity. As long as intellect and character, scholarship and humanity maintain their value, Otto Hahn will be of relevance to the coming generations.
The number of those who had been able to be near Otto Hahn is small. His behaviour was completely natural to him, but for the next generations he will serve as a model, regardless of whether one admires in the attitude of Otto Hahn his humane and scientific sense of responsibility or his personal courage.
Otto Hahn's achievements are known universally and will hold a special place in the history of science. He is remembered too for his whole character, his generosity of spirit, his belief in the proper use of scientific discovery and for his humanity.
It was remarkable, how, after the war, this rather unassuming scientist who had spent a lifetime in the laboratory, became an effective administrator and an important public figure in Germany. Hahn, famous as the discoverer of nuclear fission, was respected and trusted for his human qualities, simplicity of manner, transparent honesty, common sense and loyalty.
Prof. Dr. Linus Pauling, Pasadena, at the Nobel conference in Lindau, Bavaria, 1981.
Otto Hahn is widely portrayed as a warm, considerate, charming person. The characterization is accurate. In fact, precisely because the personality of this decent human being suffered no great changes throughout his career, he offers us a touchstone to determined the extent of changes in scientists' perceptions of their obligations to society during the twentieth century. The important thing is not that scientists may disagree on where their responsibility to society lies, but that they are conscious that a responsibility exists, are vocal about it, and when they speak out they expect to affect policy. Otto Hahn, it would seem, was even more than just an example of this twentieth-century conceptual evolution; he was a leader in the process.
The discovery by Otto Hahn that the uranium nucleus could be split marks, on the one hand, the culmination of one of the most fascinating periods in the history of physics and, on the other, heralds the advent of a new age in Man's understanding and mastery of nature.
Ever since my early youth, I have admired Otto Hahn as a scientist and a human being. The reason for Hahn's peace work was simply that, knowing more than other citizens about atomic weapons, he felt it his duty to speak about this issue that was so crucial for mankind. He could make things clear, he had to use his knowledge. And it is why Otto Hahn, with atomic weapons in mind, wrote shortly before his death of 'the necessity of world peace'.
Thanks to his moral integrity Otto Hahn was trusted everywhere. He used it to point uncompromisingly to three important goals. For him the cessation of nuclear weapon tests, not transferring atomic weapons in order not to let the number of atomic powers become larger, and general disarmament were the essential challenges. Hahn occasionally emphasised that he was not a politician. Yet his speeches, appeals, warnings, and his appearance in public betrayed a purposeful political engagement. His distinctively humanitarian convictions directed him logically to this path. - As we must conclude, Otto Hahn is not to be held personally responsible for the consequences of his discovery, but he suffered from them and because of the constantly smouldering conflicts of conscience became a tireless watchman for the world of a life worth living, at peace, without anxiety caused by the atom. His engagement with science, humanity and peace is exemplary and to be remembered for following generations.
Dr. Klaus Hoffmann, Dresden, author of 'Otto Hahn - Achievement and Responsibility', New York etc. 2001.