I revisit Niels Bohr's famous 1932 'Light and Life' lecture, confronting it with current knowledge. Topics covered include: life origin and evolution, quantum mechanics and life, brain and mind, consciousness and free will, and light as a tool for biology, with special emphasis on optical tweezers and their contributions to biophysics. Specialized knowledge of biology is not assumed.
I revisit Niels Bohr's famous 1932 'Light and Life' lecture, confronting it with current knowledge. Topics covered include: life origin and evolution, quantum mechanics and life, brain and mind, consciousness and free will, and light as a tool for biology, with special emphasis on optical tweezers and their contributions to biophysics. Specialized knowledge of biology is not assumed.
On August 15, 1932 Niels Bohr gave opening address of International Congress on Therapy held in Copenhagen. Bohr's title was Light and Life, and his purpose was to draw attention to epistemological implications for life sciences of fundamental changes that quantum theory had brought to conception of natural law (Bohr 1933). He thought that these changes, which extend to very idea of nature of scientific explanation, were important not only for a full appreciation of new situation brought to physics by quantum theory. According to Bohr, these developments had also created an entirely new background for viewing problems of biology, especially as concerns our views on position of living organisms in realm of natural science. In particular, Bohr proposed that notion of complementarity, which he had first presented 5 years earlier at International Congress of Physics in Como, relevant also for physiological and psychological aspects of life. Bohr began his address by stating what nowadays stigmatized as reductionist credo, namely that subtle character of riddle of life notwithstanding, any scientific explanation of biological phenomena necessarily must consist of reducing description of more complex phenomena to that of simpler ones. But, Bohr continued, discovery of an essential limitation of mechanical description of natural phenomena, as revealed by recent development of atomic theory, has lent new interest to old problem of how far program of reductive biological explanations can be carried. Bohr then presented a brief historical account of rise of quantum theory in connection with study of light, which he thought is perhaps least complex of all physical phenomena. Yet, it turned out that despite its lack of complexity, phenomenon of light cannot be given a coherent mechanical explanation, inasmuch as from viewpoint of classical physical theories, the quantum of action . . . must be considered as an irrational notion. The spatial continuity of light propagation, on one hand, and atomicity of light effects on other hand, must, therefore, be considered as complementary aspects of one reality, in sense that each expresses an important feature of phenomena of light. Those aspects are complementary, because, although they are conceptually irreconcilable from a mechanical point of view, they can never be shown to be in direct, or empirical, contradiction. The reason for this that any closer analysis of either wave aspect or particle aspect of light demands mutually exclusive observational arrangements.
On August 15, 1932 Niels Bohr gave opening address of International Congress on Therapy held in Copenhagen. Bohr's title was Light and Life, and his purpose was to draw attention to epistemological implications for life sciences of fundamental changes that quantum theory had brought to conception of natural law (Bohr 1933). He thought that these changes, which extend to very idea of nature of scientific explanation, were important not only for a full appreciation of new situation brought to physics by quantum theory. According to Bohr, these developments had also created an entirely new background for viewing problems of biology, especially as concerns our views on position of living organisms in realm of natural science. In particular, Bohr proposed that notion of complementarity, which he had first presented 5 years earlier at International Congress of Physics in Como, relevant also for physiological and psychological aspects of life. Bohr began his address by stating what nowadays stigmatized as reductionist credo, namely that subtle character of riddle of life notwithstanding, any scientific explanation of biological phenomena necessarily must consist of reducing description of more complex phenomena to that of simpler ones. But, Bohr continued, discovery of an essential limitation of mechanical description of natural phenomena, as revealed by recent development of atomic theory, has lent new interest to old problem of how far program of reductive biological explanations can be carried. Bohr then presented a brief historical account of rise of quantum theory in connection with study of light, which he thought is perhaps least complex of all physical phenomena. Yet, it turned out that despite its lack of complexity, phenomenon of light cannot be given a coherent mechanical explanation, inasmuch as from viewpoint of classical physical theories, the quantum of action . . . must be considered as an irrational notion. The spatial continuity of light propagation, on one hand, and atomicity of light effects on other hand, must, therefore, be considered as complementary aspects of one reality, in sense that each expresses an important feature of phenomena of light. Those aspects are complementary, because, although they are conceptually irreconcilable from a mechanical point of view, they can never be shown to be in direct, or empirical, contradiction. The reason for this that any closer analysis of either wave aspect or particle aspect of light demands mutually exclusive observational arrangements.
Abstract In August of 1932, quantum physicist Niels Bohr (1885–1962) delivered to the Second International Congress on Light Therapy meeting in Copenhagen his most extended treatment to that date concerning his reflections on the relevance of the new quantum mechanics for biological questions. Developing this against the backdrop of the “mechanism–vitalism” debate, he sketched out how he envisioned the relations of the new physics with classical issues of function, purpose, and teleology in biology. His address, republished here in its earliest English version, was also given in the context of his ongoing discussions of the relations of physics and biology with the German theoretical quantum physicist Ernst Pascual Jordan (1902–1980). Jordan’s subsequent interpretation of Bohr’s arguments resulted in considerable controversy and a long-term misunderstanding of Bohr’s main points. This contribution gives a detailed summary of this historical discussion and the controversies that surrounded Bohr’s arguments. It also examines Bohr’s final statements on the relations of physics and biology in the period before his death in November of 1962. A closing discussion considers the relevance of Bohr’s insights for contemporary discussions of biological reductionism and the place of the human knower in the scientific process. This is followed by the transcription of the rare 1932 text.
Overview, Victor Weisskopf Niels Bohr and the development of physics, A.Pais on the origins of the Copenhagen interpretation, Arthur I.Miller Niels Bohr and atomic physics today, Daniel Kleppner condensed matter physics - does quantum mechanics matter?, Michael E.Fisher nuclear physics - comments and reflections, Herman Feshbach the new ether, J.D.Bjorken recent developments in cosmology, George Field black holes and the foundations of quantum mechanics, Gerard't Hooft do black holes emit black body radiation?, T.D.Lee quarternionic quantum field theory, Stephen L.Adler light and life - Niels Bohr's legacy to contemporary biology, Gunther S.Stent Bertlmann's socks and the nature of reality, J.S.Bell fifty years later - when gedanken experiments become real experiments, Alain Aspect Philippe Grangier physical and philosophical issues in the Bohr-Einstein debate, Abner Shimony the Soviet reaction to Bohr's quantum mechanics, Loren R.Graham Niels Bohr and the first principles of arms control, Martin J.Sherwin American attitudes on security - comments, John Steinbruner science, technology and the arms race - European perspectives, Edoardo Amaldi.
Niels Bohr developed the framework of complementarity in response to the binding of measuring device and quantum system into an irreducible whole or "individual" at the instant of measurement. On the grounds that an organism and its environment are also bound irreducibly upon interaction, Bohr extended complementarity to biology and psychology, treating mechanistic reduction of the organism and neural objectification of consciousness as mere perspectives opposed by equally valid perspectives. In contrast to Bohr's aversion to metaphysical speculation, Heisenberg suggested that the quantum-mechanical wave function represents a real entity which determines probable outcomes of measurements given the forces acting on the system. In light of Bohr's parallel between quantum and biological systems, the probability wave of the atom ought to be mirrored in the equally intangible consciousness of the organism. I propose further that life is indeed an irreducible property of the organism and that mechanistic biology mischaracterizes life. Key to my analysis is the dual nature of time.
I: Hoffding as Mentor.- I.- 1. Harald Hoffding, His Life and Thought.- 2. Hoffding and Bohr Senior.- II.- 1. The Ekliptika Circle.- 2. Bohr and William James.- 3. Bohr and Kierkegaard.- 4. The Student Bohr on Formal Logic.- III.- 1. The Friendship.- 2. The Years Around 1927.- 3. Hoffding on Complementarity.- IV.- 1. Hoffding's Theory of Knowledge.- 2. Totality as a Category.- 3. Hoffding's Philosophy of Mind and Psychology of Free Will.- 4. Hoffding on Biology.- 5. Analogy and Scientific Progress.- II: Bohr and the Atomic Description of Nature.- V.- 1. The Principle of Correspondence.- 2. The Search for an Interpretation.- VI.- 1. Complementarity.- 2. Quantum Mechanics and Psychology.- 3. Bohr on Biology.- VII.- 1. The Objectivity of Knowledge.- 2. The EPR Discussion.- 3. The Conditions for Description.- VIII.- 1. Bohr and Realism.- 2. Hoffding on Reality.- 3. Objective Anti-Realism.- Epilogue: The Legacy.- Notes.