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

A collected meteorite whose arrival on Earth is witnessed, as opposed to a → find.

M.E. fallen, from O.E. feallan, from P.Gmc. *fallanan (cf. O.N. falla, O.H.G. fallan), from PIE base *phol- "to fall" (cf. Arm. p'ul "downfall;" Lith. puola "to fall").

Oft, stem of oftâdan "to fall;" Mid.Pers. opastan "to fall," patet "falls;" Av. pat- " to fly, fall, rush," patarəta- "winged;" cf. Skt. patati "he flies, falls," pátra- "wing, feather, leaf;" Gk. piptein "to fall," pterux "wing;" L. penna "feather, wing;" O.E. feðer "feather;" PIE base *pet- "to fly, rush."

Logic: An → error in → reasoning that renders an → argument logically → invalid such as affirming the → consequent and → denying the → antecedent.

From L. fallacia "deception," from fallere "to deceive, trick, cheat; fail, be defective."

Titâl (Dehxodâ) "deceit; deceiving speech, fallacious words;" cf. Tabari titâl hâ kərdan "to deceive (somebody) wheedlingly," Pashtu titâl "duplicity, guile, deceit, fraud."

The motion of a body under the influence of → gravity alone. See also → free-fall time.

→ free; → fall.

The characteristic time it would take a body to collapse under its own → gravitational attraction, if no other forces existed to oppose the collapse. It is given by: t_ff = (3π/32 ρ₀ G)^1/2, where ρ₀ denotes the initial density and G the → gravitational constant. Free-fall time is independent of the starting radius. Also known as → dynamical time scale.

→ free fall; → time.

In the absence of air resistance, any two bodies that are dropped from rest at the same moment will reach the ground at the same time regardless of their mass.

Galileo (1564-1642) was the first to determine, at the start of the seventeenth century, the law of constant acceleration of free-falling bodies. → law; → fall; → body.

The fall of matter toward the center of a region of gravitational influence.

Infall, from → in- + → fall.

Darun-oft, from darun- "in, into; within" (Mid.Pers. andarôn "inside," from andar, → inter-, + rôn "side, direction;" Av. ravan- "(course of a) river") + oft, → fall.

The total liquid product of precipitation or condensation from the atmosphere, as received and measured in a rain gauge.

→ rain + → fall.

Bâreš verbal noun of bâridan "to rain," bâridan "to rain;" Mid.Pers. vârân "rain," vâritan "to rain;" Av. vār- "rain; to rain;" cf. Skt. vār- "rain, water; to rain;" L. urinari "to plunge under water, to dive;" Gk. ourein "to urinate;" PIE base *uer- "water, rain, river."

Same as → weak equivalence principle.

→ universality; → free; → fall.