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

That component of a an object's motion which is perpendicular to the observer's → line of sight.

→ tangential; → motion.

The random motions and collisions of molecules, atoms, electrons, or other subatomic particles constituting an object at all temperatures above → absolute zero. The thermal motion of particles rises with the temperature of those particles and is governed by the laws of → thermodynamics. The most convincing experimental proof of thermal motion → Brownian motion.

→ thermal; → motion.

The motion of a solid body whose rotation axis is not fixed in space. For example, that of an asteroid that does not rotate about one of their principal axes. → tumbling asteroid.

→ tumble; → motion.

The motion of an object around a fixed point at a constant angular speed, and at constant radius.

→ uniform; → circular; → motion.

Motion at a constant → velocity. The state of rest is a special case of uniform motion. → accelerated motion; → inertial motion.

→ uniform; motion.