This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find.Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.The mass of the nucleus determines the atomic weight of the element but has otherwise only a slight influence on the properties of the substance, these depending primarily on the electric charge of the nucleus which, apart from the sign, is always an integral multiple of the charge of an electron. Negatively charged particles, the so-called electrons, which are held within the atom by the attraction of a much heavier positively charged atomic nucleus, enter as common building stones in all atoms. I shall merely remind you of the main features of the picture of the atom which we have gained through these discoveries. Time does not permit of my describing in detail the extraordinary extension of our experience, here dealt with, which is characterized by the discoveries of cathode rays, Röntgen rays, and the radioactive substances.
It is this peculiar situation which I shall attempt to portray here. However, at the same time as every doubt regarding the reality of atoms has been removed and as we have gained a detailed knowledge even of the inner structure of atoms, we have been reminded in an instructive manner of the natural limitation of our forms of perception. We are aware even of phenomena which with certainty may be assumed to arise from the action of a single atom, or even of a part of an atom. Similarly, the extraordinary development in the methods of experimental physics has made known to us a large number of phenomena which in a direct way inform us of the motions of atoms and of their number. We need only think of the insight into the structure of the universe which we have gained by the aid of the telescope and the spectroscope, or of the knowledge of the finer structure of organisms which we owe to the microscope. However, what has happened in so many other fields has happened also here because of the development of observational technique, the limit of possible observations has continually been shifted. Quite apart from the fundamental question of whether we are justified in demanding visualizable pictures in fields which lie outside the reach of our senses, the atomic theory originally was of necessity of a hypothetical character and, since it was believed that a direct insight into the world of atoms would, from the very nature of the matter, never be possible, one had to assume that the atomic theory would always retain this character. To explain this, it has been assumed, since early times, that the phenomena arise from the combined action and interplay of a large number of minute particles, the so-called atoms, which are themselves unchangeable and stable, but which, owing to their smallness, escape an immediate perception. Natural phenomena, as experienced through the medium of our senses, often appear to be extremely variable and unstable. First published in English in 1934 by Cambridge University Press.
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Henry Quastler Adolphe Quételet Lord Rayleigh Jürgen Renn Emil Roduner Juan Roederer Jerome Rothstein David Ruelle Tilman Sauerīiosemiotics Free Will Mental Causation James Symposiumīased on a lecture to the Scandinavian Meeting of Natural Scientists and published in Danish in Fysisk Tidsskrift in 1929.
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