An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

1) Considered as the typical, traditional, or usual form of something. → classical T Tauri star.
2) → classical physics.

From classic (+ → -al), from Fr. classique, from L. classicus "belonging to a class, relating to the first or highest class of the Roman people," from classis perhaps akin to calare "to call."

Loan from Fr. classique, as above.

A → galaxy bulge that appears protruding from the disk plane when seen at an appropriate → inclination. Classical bulges are somewhat → spheroidal, featureless (no → spiral arms, → bars, → rings, etc.), contain mostly → old stars (not much dust or star-forming regions), and are kinematically hot, i.e. dynamically supported by the → velocity dispersion of their stars. Their → surface brightness profile follows the → de Vaucouleurs law. Currently, they are thought to form through → gravitational collapse or → mergers in violent events, inducing a fast → burst of star formation if gas is available. An example is the → Sombrero galaxy bulge (D. A. Gadotti, 2012, astro-ph/1208.2295).

→ classical; → bulge.

The theory that studies distributions of → energy, → matter, and other physical quantities under circumstances where their discrete nature is unimportant. Classical field theory traditionally includes → Newtonian mechanics, Maxwell's → electromagnetic theory, and Einstein's theory of → general relativity. The main scope of classical field theory is to construct the mathematical description of → dynamical systems with an infinite number of degrees of freedom. The word "classical" is used in contrast to those field theories that incorporate → quantum mechanics (→ quantum field theory). Classical field theories are usually categorized as → non-relativistic and → relativistic.

→ classical; → field; → theory.

The traditional logic in which → sets are sharply defined (→ crisp set) for example, the number of students registered for a course, or the names beginning with P in a given telephone directory. Classical logic also defines relations between sets of → propositions. Consider for example two sets: elephants and mammals, a simple proposition would be the assertion that all elephants are mammals, that is E ⊂ M, where E is the elephant set and M is the mammal set. The classical logic proposition is either true or false. Compare with → fuzzy logic.

→ classical; → logic.

The branch of physical science which deals with the motions of bodies travelling at velocities that are very much less than that of light in a vacuum. Same as → Newtonian mechanics.

→ classical; → mechanics.

Physics not taking into account → quantum mechanics or Einstein's → relativity theory. Classical physics includes the branches developed before the beginning of the 20th cantury: Mechanics, Acoustics, Optics, Thermodynamics, and Electricity and Magnetism. Most of classical physics is concerned with matter and energy on the normal scale of observation.

→ classical; → physics.

A → T Tauri star in which → accretion from a → circumstellar disk is responsible for ultraviolet and infrared excess emission and for a moderate to strong emission line spectrum superimposed on the photospheric spectrum. Classical T Tauri stars probably evolve into → weak-line T Tauri stars when their disks are fully accreted by the stars.

→ classical; → T Tauri star.