It is an old thruth that when scientists get older their interest in the history of science and culture intensifies. When the astrophysicist Subrahmanyan Chandrasekhar gave his first lecture at the Lindau Meetings in 1988, its theme was Einstein’s theory of general relativity from 1916. When six years later, Chandrasekhar returned to give his second and last lecture, the title was Newton and Michelangelo, i.e. something out of the 16th and 17th century! His lecture about the general theory of relativity first gives a pedagogical account of the way that the young patent clerk Albert Einstein first realized the need to enlarge the special theory of relativity. As I remember it from my time at the Nobel Museum, where in 2005 we produced an exhibition about Einstein’s Nobel Prize, this insight came when he in 1906 was asked to write a review article on the special theory. He then saw that all physical laws except gravitation could be included in the special theory. When analyzing the force of gravity, he arrived at his famous principle of equivalence, that gravitation is just a form of acceleration. So, as Chandrasekhar argues, the physical insight came early, but it then took 10 years of work to find the field equations. One particular reason that it took so long was that Einstein, with his tremendous physical insight, was not very good at higher mathematics. Several times he was led astray and it took a long time before he understood how the general covariance needed should be expressed. In the second part of his lecture, Chandrasekhar discusses why physicists today believe in the theory of general relativity. From the historical point of view, this acceptance of the new theory came from the classical observations: The perihelion motion of Mercury and the bending of light close to the sun. But these observations only test small effects in the post-Newtonian approximation. Chandrasekhar argues that the belief in the general theory of relativity comes more from its internal consistency and the fact that it does not contradict other physical theories. He also stresses the fact that there are exactly solvable problems as, e.g., black holes, ”the hydrogen atoms of general relativity”. Today, with the observations of the accelerated expansion of the Universe, we are in the situation that the theory of general relativity is again tested and this time on the most grand scale conceivable! Anders Bárány |