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

→ extraterrestrial life.

→ exo-; → life.

Life that may exist and originate outside the planet Earth.

→ extraterrestrial; → life.

The length of time required for half of a given quantity of → radioactive material to → decay.

→ half; → life.

The condition that distinguishes living organisms from inorganic objects, i.e. non-life, and dead organisms. It is manifested by growth through metabolism, reproduction, and the power of adaptation to environment through changes originating internally.

O.E. life, from P.Gmc. *liba- (cf. O.N. lif "life, body," Du. lijf "body," O.H.G. lib "life," Ger. Leib "body"), properly "continuance, perseverance," from PIE *lip- "to remain, persevere, continue, live;" cf. Gk. liparein "to persist, persevere."

Zist "life, existence," from zistan "to live;" Mid.Pers. zivastan "to live," zivižn "life," zivik, zivandag "alive, living;" O.Pers./Av. gay- "to live," Av. gaya- "life," gaeθâ- "being, world, mankind," jivya-, jva- "aliving, alive;" cf. Skt. jiva- "alive, living;" Gk. bios "life;" L. vivus "living, alive," vita "life;" O.E. cwic "alive;" E. quick; Lith. gyvas "living, alive;" PIE base *gweie- "to live."

The average amount of time an unstable radioisotope exists before it decays, It is equal to 1.44 times the half-life.

→ mean; → life.

The time scale on which a stellar image changes significantly due to → atmospheric turbulence. It is proportional to the ratio r₀/Δv, where r₀ is the → Fried parameter and Δv the standard deviation of the distribution of wind velocities weighted by the turbulence structure coefficient. Typical lifetimes in the visible range from about 3 to 30 milliseconds.

→ speckle; → life; → time.

Omr "life-time;" from Ar. 'umr; pakâl, → speckle.

Animals and plants living in their natural habitat.

→ wild; → life.