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

The total energy of a → closed system is constant. This means that energy can be changed from one form to another, or transferred from one system to another, but it cannot be created or destroyed. A mathematical formulation of the first law is: δQ = δU + δW, where δQ is the heat transferred to the system, δU the change in internal energy (resulting in a rise or fall of temperature), and δW is the work done by the system.

→ first; → law; → thermodynamics.

The branch of → fluid mechanics that deals with the movement of gases and liquids.

→ fluid; → dynamics.

The branch of physics that extends the ideas developed in → mechanics and → thermodynamics to the study of motion and equilibrium of → fluids.

→ mechanics; → fluid.

The study of the → motions of the → stars, → gas, and → dark matter in a → galaxy to explain the main → morphological and → kinematical features of the galaxy.

→ galactic; → dynamics.

The study of heredity and inheritance, of the transmission of traits from one individual to another, of how genes are transmitted from generation to generation.

From → genetic and → -ics.

A branch of physics that deals with reflection and refraction of rays of light without reference to the wave or physical nature of light.

→ geometric; → optics.

The branch of physics that deals with the Earth and its environment, including meteorology, oceanography, seismology, and geomagnetism.

→ geo-; → physics.

The study or the application of the influence of political and economic geography on the politics, national power, foreign policy, etc., of a state (Dictionary.com).

→ geo-; → politics.

The study of → dynamical systems in terms of the → Hamilton's equations.

→ Hamiltonian function; → dynamics.

The science or art of → interpretation. Originally the term was limited to the interpretation of the Scriptures, but since the nineteenth century it has developed into a general theory of human understanding through the work of Friedrich Schleiermacher (1768-1834), Wilhelm Dilthey (1833-1911), and others. The comprehension of any written text requires hermeneutics. Many different hermeneutic theorists have proposed many different methodologies.

From Gk. hermeneutikos "interpreting," from hermeneutes "interpreter," from hermeneuein "to interpret," of unknown origin. It was formerly thought to derive from Hermes, the tutelary divinity of speech, writing, and eloquence.

Âzand-pardâzik, from âzand, → interpretation, + pardâz, present stem of pardâxtan "to accomplish, bring to perfection; to care," → theoretician, + -ik, → ics.

A branch of astrophysics that deals with objects emitting highly energetic radiation, such as X-ray astronomy, gamma-ray astronomy, and extreme ultraviolet astronomy, as well as neutrinos and cosmic rays.

→ high; → energy; → astrophysics.

The branch of physics dealing with the motion, energy, and pressure of neutral → fluids.

→ hydro- + → dynamics.

Same as → magnetohydrodynamics.

→ hydro-; → magnetics.

A branch of physics that deals with the characteristics of → fluids at rest and especially with the pressure in a fluid or exerted by a fluid on an immersed body.

→ hydro- + → statics.

Magnetohydrodynamics of a → plasma with very large (infinite) → conductivity. In this condition, → Ohm's law reduces to E = -v × B, where E represents → electric field, B → magnetic field, and v the → fluid velocity. Ideal MHD is the simplest model to describe the dynamics of plasmas immersed in a magnetic field. It is concerned with → one-fluid magnetohydrodynamics and neglects → resistivity. This theory treats the plasma composed of many charged particles with locally neutral charge as a continuous single → fluid. Ideal MHD does not provide information on the velocity distribution and neglects the physics relating to wave-particle interactions, as does the two-fluid theory as well. It does have the advantage that the macroscopic dynamics of the → magnetized plasma can be analyzed in realistic three-dimensional geometries (K. Nishikawa & M. Wakatani, 2000, Plasma Physics, Springer). See also → non-ideal magnetohydrodynamics.

→ ideal; → magnetohydrodynamics.

The science concerned with gathering, manipulating, storing, retrieving, and classifying recorded → information. Also called → information science, computer science.

Informatics, from informat(ion), → information + → ics.

The branch of electronics that deals with integrated circuits, especially the interdependence of material, circuits, and design.

Integrated, p.p. of → integrate; → electronics.

The branch of mechanics dealing with the description of the motion of bodies or fluids without reference to the forces producing the motion.

From Gk. kinetikos "moving, putting in motion," from kinetos "moved," verbal adj. of kinein "to move;" PIE base *kei- "to move to and fro" (cf. Mod.Pers. šodan, šow- "to go; to become;" Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Goth. haitan "call, be called;" O.E. hatan "command, call").

Jonbešik, from jonbeš "motion" + -ik→ -ics. The first element from Mid.Pers. jumbidan, jumb- "to move," Lori, Laki jem "motion," related to gâm "step, pace;" O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," gāman- "step, pace" (Mod.Pers. âmadan "to come"); Skt. gamati "goes;" Gk. bainein "to go, walk, step," L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come."

A reformulation of → Newtonian mechanics in which dynamical properties of the system are described in terms of generalized variables. In this approach the → generalized coordinates and → generalized velocities are treated as independent variables. Indeed applying Newton's laws to complicated problems can become a difficult task, especially if a description of the motion is needed for systems that either move in a complicated manner, or other coordinates than → Cartesian coordinates are used, or even for systems that involve several objects. Lagrangian dynamics encompasses Newton dynamics, and moreover leads to the concept of the → Hamiltonian of the system and a process by means of which it can be calculated. The Hamiltonian is a cornerstone in the field of → quantum mechanics.

→ Lagrangian; → dynamics.

The three basic laws of → dynamics which were first formulated by Isaac Newton in his classical work "Mathematical Principles of Natural Philosophy" published in 1687. → Newton's first law of motion; → Newton's second law of motion; → Newton's third law of motion.

→ law; → dynamics.