Light and life. Address delivered at the opening meeting of the International Congress on Light Therapy in Copenhagen 15. August 1932.

Copenhagen: IIe Congrès International de la Lumière, 1932.

First edition of this famous lecture, which marks Bohr’s first detailed attempt to apply concepts arising from quantum mechanics (particularly complementarity) to areas outside physics. “Here, for the first time, Bohr raised a question that was to preoccupy him, off and on, until his death: Would it ever be possible to push the analysis of living processes to the limit where they can be described in terms of pure physics and chemistry?” (Pais, p. 441). Bohr’s lecture can be viewed as one of the foundation stones of molecular biology in that it inspired the young physicist Max Delbrück—who was in the audience when Bohr delivered it—to switch from physics to biology. “It is fair to say that with Max, Bohr found his most influential philosophical disciple outside the domain of physics, in that through Max, Bohr provided one of the intellectual fountainheads for the development of 20th century biology” (quoted in Pais, p. 442). This pamphlet, dated 1932, apparently predates both the lecture’s publication in Danish in Naturens Verden, in English in Nature, and in German in Naturwissenschaften, all of which were published in 1933.

“Bohr had a life-long interest in philosophy, publishing three volumes of philosophical essays. He was also the son of the distinguished physiologist Christian Bohr, a student of Carl Ludwig, who discovered the cooperative binding of oxygen to hemoglobin. It is therefore not entirely surprising that, when he was asked to give a lecture at the International Congress of Light Therapists in Copenhagen in August 1932, Niels Bohr chose to speak on the philosophy of biology. His lecture, the text of which was subsequently published in Nature, was entitled ‘Light and Life’.

“In ‘Light and Life,’ Bohr noted that one of the fundamental tenets of quantum mechanics was the principle of complementarity. This stated that although it is possible to determine the location or the velocity of a subatomic particle such as an electron, it is not possible to determine both, because the act of measurement itself perturbs the system. Techniques that analyzed the position of an electron altered its velocity; techniques that measured the velocity altered the position. Location and velocity are therefore complementary properties of the electron. Not complementary in the ordinary sense of adding together to make a whole, but rather mutually exclusive, as these properties can only be measured in different frames of reference.

“Bohr saw an analogy between physicists’ attempts to characterize the atom and biologists’ attempt to characterize the cell. Living cells were, to be sure, made of ordinary matter, and therefore amenable to chemical analysis, but the matter was organized in a complex and particular way. To study the chemistry, the organization had to be destroyed; to study the organization, one has to operate at a level at which the chemistry is invisible. Bohr therefore proposed that the chemical basis of an organism and its organizational hierarchy are complementary properties, just as velocity and location are complementary properties of an electron.

“In stating that the unique characteristic of living systems was their organization or (in another passage) their teleological (functionally adapted) properties, Bohr was careful to avoid the implication that he was reviving the old vitalist doctrine that different physical laws operate in living organisms: ‘I think we all agree with Newton that the real basis of science is the conviction that Nature under the same conditions will always exhibit the same regularities. If we were able to push the analysis of the mechanism of living organisms as far as that of atomic phenomena, we should scarcely expect to find any features differing from the properties of inorganic matter.’

“As a result of the ‘Light and Life’ talk, a young theoretical physicist sitting in the audience was influenced to become a biologist. According to the Bohr biographer Abraham Pais, his role in turning Max Delbrück into a biologist was Niels Bohr’s ‘greatest contribution to biology’” (Hunter, pp. 217-8).

“Delbrück was German, born to the aristocracy of the intellect — his father was the professor of history and his uncle the professor of theology in the University of Berlin — and trained as a quantum physicist. His mind and style had been formed by Niels Bohr, the physicist, philosopher, poet, and incessant Socratic questioner who made Copenhagen one of the capital cities of science between the wars. Delbruck's ideas about the physical properties of the gene, in a youthful paper of 1935, had led Schrödinger to write What is Life? Delbrück was perhaps the earliest of the theoretical physicists who have crossed over to biology; Szilard, Crick, Maurice Wilkins were others, while Linus Pauling, arriving at biology from a different tangent, was a physical chemist whose strength was founded in quantum mechanics. The move from physics has been the intellectual immigration that has mattered most to biology” (Judson, p. 50). Delbrück became a leader of what was known as the “phage group” of bacterial geneticists; in 1969, he received a share of the Nobel Prize for physiology / medicine for describing the means by which living cells are infected with viruses.

G. K. Hunter, Vital Forces: The Discovery of the Molecular Basis of Life, 2000; H. F. Judson, The Eighth Day of Creation, 1979; A. Pais, Niels Bohr’s Times, 1991.

4to (236 x 158 mm), pp 10, original printed wrappers, a virtually mint copy. Rare.

Item #3792

Price: $3,200.00