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

A cosmological model in which a static (neither expanding nor collapsing) Universe is maintained by introducing a cosmological repulsion force (in the form of the cosmological constant) to counterbalance the gravitational force.

→ Einstein; → static; arr; universe.

Referring to electric charges at rest.

→ electro-; → static.

A quantity of electricity at rest on the surface of an insulator or an insulated conductor.

→ electrostatic; → charge.

A region of space in which a non-moving → electric charge would be subjected to a force of attraction or repulsion as a result of the presence of another stationary electric charge. The electrostatic field is a special case of the → electromagnetic field.

→ electrostatic; → field.

The production of stationary electric charges on an uncharged object as a result of a charged body being brought near it without touching it. A positive charge will induce a negative charge, and vice versa.

→ electrostatic; → induction.

The unit of electric charge in the → cgs system of units. Also called the → statcoulomb. The esu is defined such that if two objects, each carrying a charge of +1 esu, are 1 cm aparat, then they repel each other with a force of 1 → dyne. 1 esu = 3.3356 × 10^-10 → coulombs.

→ electrostatic; → unit; → charge.

In a → plasma, a disturbance that is devoid of magnetic field, and hence can be expressed by an electrostatic potential. The electric field is always parallel to the propagation vector, so that the electrostatic wave is → longitudinal.

→ electrostatic; → wave.

The branch of → electricity dealing with the phenomena and properties of stationary → electric charges, as opposed to → electrodynamics. It involves the build-up of charge on the → surface of → objects due to → contact with other surfaces.

→ electro- + → statics.

Of or pertaining to → hydrostatics.

→ hydro- + → static.

The equation describing the → hydrostatic equilibrium in a star, expressed as: dP/dr = -GMρ/r², where P and M are the mass and pressure of a spherical shell with thickness dr at some distance r around the center of the star, ρ is the density of the gas, and G the → gravitational constant.

→ hydrostatic; → equation.

1) The physical situation reached in a fluid when complete balance exists between the internal pressure at any point and the weight of the material above the point.
2) For a star, the balance between the inward → gravitational force and the outward gas pressure everywhere in the star. → hydrostatic equation. See also → hydrodynamic equilibrium.

→ hydrostatic; → equilibrium.

A model of the → Milky Way galaxy in which the → Galactic halo (composed of → gas, → magnetic fields, and → cosmic rays) is assumed to be in → hydrostatic equilibrium. Parker (1966) presented the first study of stability considerations between gas, magnetic fields and cosmic rays in an equilibrium configuration. He found that it is difficult to maintain a stable configuration due to magnetohydrodynamic self-attraction (→ Parker instability). Subsequent works taking into account turbulent motions showed that turbulent pressure can mitigate the influence of Parker instabilities. This enabled new attempts to find conditions under which a stable equilibrium configuration of the Galaxy could exist.

→ hydrostatic; → halo.

The term ρgz in the → Bernoulli equation. It is not pressure in a real sense, because its value depends on the reference level selected.

→ hydrostatic; → pressure.

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.

1) Pertaining to bodies, forces, charges, etc. that act in equilibrium; at rest; stationary.
2) Pertaining to → statistics.

From Mod.L. statica, from Gk. statikos "causing to stand," from stem of histanai "to cause to stand," cognate with Pers. istâdan "to stand," as below.

Istâ "standing, static," from istâdan "to stand" (Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand").

The state of a rigid body which is not moving at all. The conditions for static equilibrium are: 1) the sum of the external forces on the object must equal zero, and 2) the sum of the → torques must equal zero. See also → dynamic equilibrium and → mechanical equilibrium.

→ static; → equilibrium.

Same as → stationary limit.

→ static; → limit.

In → fluid mechanics, the → pressure felt by an object suspended in a → fluid and moving with it. This pressure is called static because the object is not moving relative to the fluid. See also → dynamic pressure.

→ static; → pressure.

A closed Universe of finite volume with a constant radius of curvature.

→ static; → Universe.

The branch of → mechanics which studies the laws of composition of forces and the conditions of equilibrium of material bodies under the action of forces.

→ static; → -ics.

Istâyik, from istâ, → static + -ik, → -ics.