Theory

Theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context, the results might for example include generalized explanations of how nature works. The word has its roots in ancient Greek, but in modern use it has taken on several different related meanings. A theory is not the same as a hypothesis. A theory provides an explanatory framework for some observation, and from the assumptions of the explanation follows a number of possible hypotheses that can be tested in order to provide support for, or challenge, the theory.

A theory can be normative (or prescriptive), meaning a postulation about what ought to be. It provides "goals, norms, and standards". A theory can be a body of knowledge, which may or may not be associated with particular explanatory models. To theorize is to develop this body of knowledge.

As already in Aristotle's definitions, theory is very often contrasted to "practice" (from Greek praxis, πρᾶξις) a Greek term for "doing", which is opposed to theory because pure theory involves no doing apart from itself. A classical example of the distinction between "theoretical" and "practical" uses the discipline of medicine: medical theory involves trying to understand the causes and nature of health and sickness, while the practical side of medicine is trying to make people healthy. These two things are related but can be independent, because it is possible to research health and sickness without curing specific patients, and it is possible to cure a patient without knowing how the cure worked.

Chess theory

The game of chess is commonly divided into three phases: the opening, middlegame, and endgame. There is a large body of theory regarding how the game should be played in each of these phases, especially the opening and endgame. Those who write about chess theory, who are often but not necessarily also eminent players, are referred to as "theorists" or "theoreticians".

"Opening theory" commonly refers to consensus, broadly represented by current literature on the openings. "Endgame theory" consists of statements regarding specific positions, or positions of a similar type, though there are few universally applicable principles. "Middlegame theory" often refers to maxims or principles applicable to the middlegame. The modern trend, however, is to assign paramount importance to analysis of the specific position at hand rather than to general principles.

The development of theory in all of these areas has been assisted by the vast literature on the game. In 1913, preeminent chess historian H. J. R. Murray wrote in his 900-page magnum opus A History of Chess that, "The game possesses a literature which in contents probably exceeds that of all other games combined." He estimated that at that time the "total number of books on chess, chess magazines, and newspapers devoting space regularly to the game probably exceeds 5,000". In 1949, B. H. Wood opined that the number had increased to about 20,000.David Hooper and Kenneth Whyld wrote in 1992 that, "Since then there has been a steady increase year by year of the number of new chess publications. No one knows how many have been printed..." The world's largest chess library, the John G. White Collection at the Cleveland Public Library, contains over 32,000 chess books and serials, including over 6,000 bound volumes of chess periodicals. Chess players today also avail themselves of computer-based sources of information.

Scientific theory

A scientific theory is a well-substantiated explanation of some aspect of the natural world that is acquired through the scientific method and repeatedly tested and confirmed through observation and experimentation. As with most (if not all) forms of scientific knowledge, scientific theories are inductive in nature and aim for predictive power and explanatory capability.

The strength of a scientific theory is related to the diversity of phenomena it can explain, and to its elegance and simplicity. See Occam's razor. As additional scientific evidence is gathered, a scientific theory may be rejected or modified if it does not fit the new empirical findings; in such circumstances, a more accurate theory is then desired. In certain cases, the less-accurate unmodified scientific theory can still be treated as a theory if it is useful (due to its sheer simplicity) as an approximation under specific conditions (e.g., Newton's laws of motion as an approximation to special relativity at velocities which are small relative to the speed of light).

Momentum

In classical mechanics, linear momentum or translational momentum (pl. momenta; SI unit kg m/s, or equivalently, Newton second) is the product of the mass and velocity of an object. For example, a heavy truck moving rapidly has a large momentum—it takes a large or prolonged force to get the truck up to this speed, and it takes a large or prolonged force to bring it to a stop afterwards. If the truck were lighter, or moving more slowly, then it would have less momentum.

Like velocity, linear momentum is a vector quantity, possessing a direction as well as a magnitude:

where p is the three-dimensional vector stating the object's momentum in the three directions of three-dimensional space, v is the three-dimensional velocity vector giving the object's rate of movement in each direction, and m is the object's mass.

Linear momentum is also a conserved quantity, meaning that if a closed system is not affected by external forces, its total linear momentum cannot change.

In classical mechanics, conservation of linear momentum is implied by Newton's laws. It also holds in special relativity (with a modified formula) and, with appropriate definitions, a (generalized) linear momentum conservation law holds in electrodynamics, quantum mechanics, quantum field theory, and general relativity. It is ultimately an expression of one of the fundamental symmetries of space and time, that of translational symmetry.

Momentum (Steve Lacy album)

Momentum is the first album by Steve Lacy to be released on the Arista Novus label. It was released in 1987 and features six of Lacy's compositions (although tracks 2 and 3 only appeared on the CD edition) with texts by Giulia Niccolai, Herman Melville, and Brion Gysin performed by Lacy, Bobby Few, Steve Potts, Jean-Jacques Avenel, Oliver Johnson and Irene Aebi.

Reception

The Allmusic review by Scott Yanow awarded the album 4½ stars stating "On Steve Lacy's first album for an American label in over a decade, his sextet is heard on four extensive originals by the great soprano saxophonist. The music is complex yet often melodic and, although Irene Aebi takes typically eccentric vocals on two of the songs, the main reasons to acquire this album are for the thoughtful yet unpredictable solos of Lacy and altoist Steve Potts. ".

Track listing

Momentum (electromagnetic simulator)

Momentum is 3-D planar EM simulation software for electronics and antenna analysis, a partial differential equation solver of Maxwell's equations based on the method of moments. It is a 3-D planar electromagnetic (EM) simulator used for passive circuit analysis.

It combines full-wave and quasi-static EM solvers to provide insight into EM behavior of MMIC, RFIC, RF Board, Signal Integrity, and antenna designs. The Momentum simulation engine is integrated into Keysight ADS and Keysight Genesys.

It was originally developed by a Belgian company, Alphabit, a spinoff from IMEC. Early contributors to the technology include Niels Faché, Jan Van Hese, Frank Libbrecht, Jeannick Sercu, Luc Vandormael, Mieke Herreman, Peter Kok, Tom Dhaene and Krist Blomme.

The company was acquired by Hewlett-Packard, later it became part of Agilent Technologies and since November 2014 it is part of Keysight Technologies EEsof division, the current owners.

References