[...]... have a nucleus, and electrons are orbiting around these nuclei The size of the atoms (the size of the outer orbit of the electrons) is of the order of 1/100 000 000 cm, the nucleus is 100 000 times smaller The atom is therefore largely empty Compare this: suppose the nucleus is something like a tennis ball (about 2.5 inch or 6.35 cm diameter) Then the first electron circles at a distance of about 6.35... example, the theory of relativity owes very much to the experiments of Michelson concerning the speed of light And Planck came to his discovery due to very precise measurements on blackbody radiation done in the same place, Berlin, in which he was working On the other hand, to devise useful experiments an experimental physicist needs some understanding of the existing theory It is the combination of experiment... quantized He thought of emission in packets, but not that light could exist only in such packets His hypothesis was on the nature of the process of emission, not on the nature of the radiated light It seems a small step, but it is precisely this type of step that is so difficult to make It is interesting to quote here the recommendation made by Planck and others when nominating Einstein for the Prussian 16... (1831–1879) This man wrote down the laws of electromagnetism, and explained light as electromagnetic waves His equations stand till today His theory has had enormous consequences From it developed the theory of relativity, and on the practical side the discovery and application of radio waves by Hertz and Marconi Maxwell must be ranked among the giants of physics such as Newton and Einstein The genius of Maxwell... in the old days Einstein, well aware of all this, somehow never discovered quantum mechanics This is one of the more astonishing things: why did he not discover quantum theory? Knowing all about the wave theory of light and having introduced the concept of the photon, he never fused these concepts into one theory According to Pais, Einstein pondered about this problem in a most intensive way in the. .. speed it is possible to compute how many people are seated inside that car (provided the mass of the car itself and the average weight of the passengers is known) This is essentially the method by which the mass of a particle with a very small lifetime can be measured Measure the energy and the velocity and then the mass may be determined When the velocity of some material object becomes close to the speed... come to the more esoteric part: the understanding of the theory of elementary particles Chapter 10 contains a further discussion of the Higgs particle and the experimental search for it Finally, in Chapter 11 a short description of the theory of strong interactions will be presented The strong interactions are responsible for the forces between the quarks, giving rise to the particle zoo, the complex... nucleus because the electric forces help to push the proton out Taking that difference in binding energy of proton and neutron into account the decay of a neutron in a nucleus is usually impossible While the mass of the neutron is larger than the sum of the masses of a proton and an electron, the margin is small (about 0.7 MeV) The difference in binding energies of neutron and proton may (and often will)... and not so popular level and each has its particular virtues Two books deserve special mention: 6 E L E M E N TA R Y PA R T I C L E P H Y S I C S A Pais: Subtle is the Lord The Science and the Life of Albert Einstein, Oxford University Press 1982, ISBN 0-19-853907-X A Pais: Inward Bound Of Matter and Forces in the Physical World, Oxford University Press 1986, ISBN 0-19-851997-4 These two books, masterpieces,... threefold? These actors come in triples, they look the same, they are dressed completely the same way, they speak the same language, they differ only in their sizes But then they really do differ: one of the actors is 35 000 times bigger than his otherwise identical companion! That is what we see today when systematizing elementary particles And no one has any idea why they appear threefold It is the great . PHYSICS A. Pais: Subtle is the Lord The Science and the Life of Albert Einstein, Oxford University Press 1982, ISBN 0-19-853907-X. A. Pais: Inward Bound. Of Matter and Forces in the Physical. have a nucleus, and electrons are orbiting around these nuclei. The size of the atoms (the size of the outer orbit of the electrons) is of the order of 1/100 000 000 cm, the nucleus is 100 000 times. discussed, and in Chapter 4 some of the aspects of ordinary mechanics and the theory of relativity. In other words, we must also discuss the stage on which the actors appear. An overview of the basic