The Niels Bohr Archive's Tuesday 19 December 2000 at 14:15
History of Science Seminar Auditorium A, Niels Bohr Institute
Blegdamsvej 17, Copenhagen
O N E H U N D R E D Y E A R S O F Q U A N T A
On 14 December 1900 Max Planck gave his seminal lecture to the German Physical
Society, introducing the quantum concept for the first time. To join in the
celebration of this crucial episode in the history of modern physics, we have
invited two prominent historians of science who have studied the event, its
origins and its implications. They will discuss, respectively, the related
questions of Planck's original understanding of his idea and his fellow
physicists' understanding of it once it had been introduced.
Olivier Darrigol
CNRS, Paris
Continuities and Discontinuities in Planck's "Akt der Verzwfeiflung"
Planck's famous communication of December 1900 cannot be understood without
taking into account an essential difference between his and Boltzmann's
conceptions of the relation between the micro-world and the macro-world. For
Boltzmann, macroscopic laws are in principle completely determined by the
underlying microscopic dynamics. For Planck, the microscopic dynamics is partly
undetermined and must be supplemented by additional assumptions in order to
reach macroscopic laws. Thanks to this leeway, Planck could introduce finite
energy elements and derive his famous black-body law without giving up the
continuity and determinism of former dynamical theories. The purpose of this
paper is to explain the origins, peculiarities and evolution of Planck's
approach; to show how it ultimately yielded the correct black-body law; and to
examine the status of the energy elements which Planck thereby introduced.
Ole Knudsen
Department of the History of Science, Aarhus University
How an Average Physicist Understood Planck's Quantum:
O.W. Richardson's Textbook from 1916
In 1914 O.W. Richardson published an advanced textbook, "The Electron Theory of
Matter," based on his lectures to graduate students at Princeton where he was
professor of physics from 1906 to 1914. The book got a very favourable review
(signed "N.B.") in Nature and must have sold well, for a second, revised,
edition containing a much extended account of Niels Bohr's new atomic theory
appeared in 1916. Based on this book and on some of Richardson's research papers
from 1901 to 1916, I shall try to describe his view of the quantum, a view which
I claim to be typical of the period.
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