Unknown

"If the ships could attain a relative speed equal to that of light, observers on each ship would think the other ship had shrunk to zero in length, acquired an infinite mass, and that time on the other ship had slowed to a full stop! If inertial mass did not vary in this way, then the steady application of force, such as the force supplied by rocket motors, could keep increasing a ship's velocity until it passed the speed of light. ...When the ship has contracted to one-tenth its rest length, its relativistic mass has become ten times as great. ...ten times as much force is required to produce the same increase in speed."

"Two ships are passing each other with uniform speed close to that of light. As they pass, a beam of light on the other ship is sent from the ceiling to the floor. There it strikes a mirror and is reflected back to the ceiling again. You will see the path of this light as a V [shape]. If you had sufficiently accurate instruments (of course no such instrument exists), you could clock the time it takes this light beam to traverse the V-shaped path. By dividing the length of the path by the time, you obtain the speed of light. ...an astronaut inside the other ship is doing the same thing [measuring his light beam's speed]. From his point of view... the light simply goes down and up along the same line, obviously a shorter distance than along the V that you observed. ...he also obtains the speed of light. ...But his light path is shorter. ...There is only one possible explanation: his clock is slower. Of course, the situation is perfectly symmetrical. If you send a beam down and up inside your ship, he will see its path as V-shaped. He will deduce that your clock is slower."

"If two spaceships are in relative motion, an observer on each ship will measure the other ship as contracted slightly in the direction of its motion. ...The theory does not say that each ship is shorter than the other; it says that astronauts on each ship measure the other ship as shorter."

"If an astronaut traveled as fast as light his clock would stop completely."

"There is no absolute time throughout the universe by which absolute simultaneity can be measured. Absolute simultaneity of distant events is a meaningless concept."

"In the special theory of relativity, the speed of light becomes... a new absolute. ...Regardless of the motion of its source, light always moves through space with the same constant speed."

"It is not possible to measure uniform motion in any absolute way."

"Imagine two spaceships, A and B. There is nothing in the cosmos except these two ships. They move toward each other at uniform speed. ...To speak of an absolute motion of either ship is to say something that has no meaning. There is only one reality: a relative motion that brings the ships together at uniform speed."

"The special theory of relativity carries the classical relativity of Newton forward another step. It says that in addition to being unable to detect the train's motion by a mechanical experiment, it is also impossible to detect its motion by an optical experiment."

"Classical physics—the physics of Isaac Newton—made clear that if you are on a uniformly [non-accelerating] moving object, say a train car that is closed on all sides so you cannot see the scenery as you go by, there is no mechanical experiment by which you can prove that you are moving. ...If you toss a ball straight up in the air, it comes straight down again. This is exactly what would happen if you standing still."

"Einstein, following the steps of Ernst Mach, took a bolder view. The reason Michelson and Morley were unable to detect an ether wind, Einstein said, is simple: There is no ether wind. He did not say that there was no ether; only... [that the ether] is of no value in measuring uniform motion."

"There were many other experiments that had created a highly unsatisfactory state of affairs with respect to theory about electromagnetic phenomenoa. If the Michelson-Morley test had never been made, the special theory would still have been formulated."

"Lorentz made an important addition to his original theory. He introduced changes in time. Clocks, he said, would be slowed down by the ether wind, and in just such a way as to make the velocity of light always measure 299,800 meters per second."

"FitzGerald's theory was put into elegant mathematical form by the Dutch physicist Hendrick Antoon Lorentz, who had independently thought of the same explanation. ...The theory came to be known as the Lorentz-FitzGerald contraction theory."

"The speed of light in an unobtainable limit; when this is reached the formula becomes \scriptstyle \sqrt{1-\frac{c^2}{c^2}} which reduces to 0. ...In other words, if an object could obtain the speed of light, it would have no length at all in the direction of its motion!"

"The strangest explanation [for the Michelson–Morley experiment] was put forth by an Irish physicist, George Francis Fitzgerald. Perhaps, he said, the ether wind puts pressure on a moving object, causing it to shrink a bit in the direction of motion. To determine the length of a moving object, its length at rest must be multiplied by the following simple formula, in which \scriptstyle v^2 is the velocity of the object multiplied by itself, \scriptstyle c^2 is the velocity of light multiplied by itself: \scriptstyle \sqrt{1-\frac{v^2}{c^2}}."

"G. J. Whitrow points out in his book The Structure and Evolution of the Universe, a very simple explanation [for the Michelson–Morley experiment] would immediately occurred to everyone: the earth doesn't move!"

"Jules Henry Poincaré... who anticipated many aspects of relativity theory, once put it this way... Suppose... everything in the universe became a thousand times larger than before. ...would you be able to tell that anything had changed? Is there an experiment you could perform that would prove you had altered in size? No, said Poincaré... "Larger" means larger in relation to something else. ...Size, then, is relative. There is no absolute way to measure an object."

"Румбъікан вӱдьӀштӧ кол куӌаш ќанъъіле."

"Загляне сонца i ў наша аконца."

"My first encounter with the concept of "information service" came with the reading of The Social Function of Science by Desmond Bernal, first published in 1939-a work that stimulated a whole generation of young scientists to think about the role of science in society, its organisation, its future. In it, he wrote that in every laboratory "there should be someone deputed to watch the whole of current literature for items which might be relevant to the work of the laboratory, and to be able to indicate without loss of time where such items are likely to be found." Such a person "would have to be chosen partly for his comprehensive scientific interests, which need to be much greater than those of the other laboratory workers, and partly for his inclination to systematic thinking." Already I felt that I might be suited to such a role."

"The area of scientific interest is... the study of the objectives, functions, structure, properties, behaviour, performance and effects of informative communication processes and information systems. To this study the name "information science" can legitimately be attached."

"In its whole sweep, therefore, information work includes: science, that helps us to understand our problems; technology, that helps us to solve them; and the art of participating in each delicate interpersonal communication into which we are invited. The fusion of these three aspects of the craft creates a “triple glow” of optimal service."

"”Information science” emerges (a) when conceptual explorations, not directed towards immediate practical or technical ends, begin to take place, and (b) they are seen to be concerned with a definable area of interest [that of facilitating the transmission of information between people]."

"We communicate with each other to inform, to instruct, to persuade, to amuse, to annoy. Informing and instructing aim to alter the receiver's concepts, whereas persuading, amusing or annoying aim to change his preferences or feelings. In a work situation people do make jokes and enemies, and use the arts of persuasion, but much of their communication has an informal or instructional aspect."

"An information system is an organisation of people, materials and machines that serves to facilitate the transfer of information from one person to another. Its function is social: to aid human communication. If we take this to mean all reception of signals by the human senses (sight, sound, small, touch, taste,...)- then communication is an incessant and essential accompaniment of all human activity. If we restrict the meaning of signals to flowing between people, much of the daily life of most of us is occupied by such interpersonal acts."

"The areas traditionally concerned with such systems are: publishing in all its ramification, librarianship, bibliography, documentation, record management, archives and the like. Systematic study of the activities in all these areas has lead to increased recognition of their common features. They are all concerned with information systems, and their study may include in the wider field of 'information science and technology' (as the Americans put it) or 'informatics' (as Soviet writers would have it)."

"Systems transfer or transform materials, energy or information - and usually all three. An information system is one whose prime function is to transfer or transform information: the telephone system is an obvious example. This book concentrates on certain types of information system: those concerned with the transfer of information between specialists, mainly with reference to their work, and mainly based on documents. The focus is thus on specialised documentary information systems."

"There is as yet no unified theory of retrieval systems, and a good deal of retrieval practice is still an empirical art, unsullied by theory."

"Four years ago, when the first edition of this book was written, information retrieval was beginning to crystallize out as a unified discipline. The process has gone further today. Several other books... have also offered a general survey, although each has contributed its own special emphasis. Many conferences on the subject have been held, and a constant stream of new articles has appeared, both in documentation journals and in those in the data processing field. Information retrieval is now recognized as a discipline, and further advances in theory are being made, What I described in the first edition as the key operation in retrieval — the subject description of documents — is being explored theoretically and experimentally, although we are still a long way from reducing this operation to rule (Chapter 3). There has been less new work on the design of descriptor languages, although ideas on the display of descriptor relations through thesauri and 'semantic maps' have been developed (Chapter 4). Access to files has been examined, particularly by those experienced in data processing."

"# The physical mechanisms (hardware) in which the structure is embodied."

"# The general structural features of the system considered as a network of units of information linked to each other and to documentary items. This may be called structural analysis."

"# The way in which units of information, and relevant relations between them, are defined in the system. This is the semantic level of subject analysis."

"A retrieval system can be studied at three levels:"

"An information retrieval system is therefore defined here as any device which aids access to documents specified by subject, and the operations associated with it. The documents can be books, journals, reports, atlases, or other records of thought, or any parts of such records—articles, chapters, sections, tables, diagrams, or even particular words. The retrieval devices can range from a bare list of contents to a large digital computer and its accessories. The operations can range from simple visual scanning to the most detailed programming."

"Four basic operations in the effective use of graphic records (documents), to store information and make it available, have been listed by Hyslop: A, recording information in documents; B, storing recorded information—documentary items; C, identifying items containing information relevant to a given problem, situation, or subject; D, providing the identified items from storage. Information storage and retrieval in the wide sense covers all these operations. In the narrow sense used in this paper, information retrieval means only C, identifying documentary items by subject."

"Throughout the nineteenth century, apart from the division in theoretical sciences and arts, classifiers attempted to divide the sciences into two groups. Already they had before them the examples of Francis Bacon (speculative and descriptive) and Hobbes (quantitative and qualitative). For Coleridge, the sciences were either pure (Grammar, Logic, Rhetoric, Mathematics, Metaphysics) or mixed. Arthur Schopenhauer’s similar groups were called pure and empirical, Wilhelm Wundt in 1887 called them formal and empirical, Globot mathematical and theoretical, and the St. Louis Congress of Arts and Sciences (1904) normative and physical. made similar division of the sciences into abstract and concrete"

"History presents a series of cultural epochs. Each is a span of years within which knowledge presents a more or less unified structure which can be expressed in a classification, but each new epoch requires a new classification."

"The structure if a fully developed classification can be technically described in the following way:"

"Classification in documentation is a tool for selection. It is essentially a 'finding system' for subject items... It is an artificial language, designed as a tool to aid in the selection of information from a store in response to search questions. The classification serves to standardise subject description, so that the description of a subject used by indexer and inquirer are more likely to coincide, thus maximising the probability of finding all items relevant to an inquiry."

"The scope of a specialised documentary classification is usually designated by its title, the subject field that it professes to classify. It is no easy task to state what is meant by a subject field. In general it can be expressed as Thing-Activity. A definable group of things... is selected, and from the many relations in which they subsist a certain number are selected as relevant."

"In scientific information, then, we find that subjects - the themes and topics on which books and articles are written - cluster into fields, each of which can be analysed into its characteristic set of facets of terms."

"The most important characteristic of documentary classification is that it is concerned with subjects, not just entities of taxonomic classification. What is the nature of the specific subjects - the themes on which books, parts of books, articles or parts of articles are written? A study of book titles alone would suggest that literary subjects have simple names like 'War, Religion', 'Boats', 'Musica; pitch', 'Colour', 'Acridines', 'Wild flowers', and so on. But the study of articles on the documentation level reveals that such titles are simple in appearance only. Such a literary subject is in reality a complex aggregate of specific subjects, eahc which is the main theme discussed from one particular aspect."

"Scientific information is faced with the following problem. On the one hand, we have the world’s literature of science and technology, past and present, in many languages; on the other, and enquirer with a question. How to select, from a vast mass of words, the few that are the most closely relevant to an enquiry? It is this selection process that makes use of classification."

"In science there are uses many classifications of entities - plants, animals, rocks, soils, stars, diseases, occupations, and so on. In these taxonomies a classification must display genetic relations - for example, an evolutionary family tree of animal species - but its prime purpose is to aid in the identification of entities... Classification enables us to select, from the whole universe of known entities, the one that best matches one newly encountered."

"The basic rules of classification are - Each characteristic of division must produce at least two classes - Only one principle of division must be used at a time, to produce mutually exclusive classes. - The species of any genius must be completely exhaustive of their parent class."

"Classification in its simplest terms, means putting together things or ideas that are alike, and keeping separate those that are different."

"The classification of subject matter may be carried out for all sort of special purposes - to arrange books on shelves, to group inventions in patents, to classify the raw materials, intermediates and products of importance to a particular manufacturer, and so on. All such arrangements have their particular uses and their particular problems."

"The preface to the first edition of this book... shows that in 1958 the classification ideas in it were felt to controversial, needing to be championed. A few years before, the had issued a memorandum proclaiming "the need for a faceted classification as the basis of all methods of information retrieval'. As part-author of this memorandum, I must now judge the claim to have been too bold, even brash."

"Interaction is the mode of life of living organisms. Each must feed on its environment, ingesting chemicals or other organisms. This is something more than "interaction", it is activity directed towards the environment. Since the organism must be selective in what it ingests, it needs to discriminate among the entities in its environment. From very primitive forms of discrimination, the sensory mechanisms of organisms have evolved into the senses of man, interpreted by an internal cognitive apparatus, memories of past experiences, and an ability to take rational decisions. By "rational" I mean activity that achieves intended results because it is based on a reliable understanding of the nature of the environment. In interacting with each other to carry out tasks jointly, men have further developed language, leading to a shared understanding of the environment. This shared understanding is knowledge."