(Encyclopedia) tropical year, time between successive vernal equinoxes; 365 days, 5 hr, 48 min, 46 sec of mean solar time (see solar time). The tropical year is the basis of the year used in the…
(Encyclopedia) Luce, Henry Robinson, 1898–1967, American publisher, b. Tengchow (now Penglai), China, the son of a Presbyterian missionary. After studying at Yale and Oxford, he worked (1921–22) as a…
(Encyclopedia) year, time required for the earth to complete one orbit about the sun. The solar or tropical year is measured relative to the sun and is equal to 365 days, 5 hr, 48 min, 46 sec of mean…
(Encyclopedia) horologyhorologyhōrŏlˈəjē [key], science of measuring time and technology of constructing instruments for its measurement or recording. Early measurements of the passage of time were…
(Encyclopedia) sidereal year, time required for the earth to complete an orbit of the sun relative to the stars. The sidereal year is 365 days, 6 hr, 9 min, 9.5 sec of mean solar time (see solar time…
(Encyclopedia) day, period of time for the earth to rotate once on its axis. The ordinary day, or solar day, is measured relative to the sun, being the time between successive passages of the sun…
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geologic timescale, a chronological scale of earth's history used to measure the relative or absolute age of any part of geologic time. Of the numerous timescales, the most…
(Encyclopedia) second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the…
(Encyclopedia) JanusJanusjāˈnəs [key], in Roman religion, god of beginnings. He was one of the principal Roman gods, the custodian of the universe. The first hour of the day, the first day of the…
