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chronometer

(Encyclopedia) chronometerchronometerkrənŏmˈətər [key], instrument for keeping highly accurate time, used especially in navigation. Before the advent of radio time signals it was the only device that…

hourglass

(Encyclopedia) hourglass, glass instrument for measuring time, usually consisting of two bulbs united by a narrow neck. One bulb is filled with fine sand that runs through the neck into the other…

prime meridian

(Encyclopedia) prime meridian, meridian that is designated zero degree (0°) longitude, from which all other longitudes are measured. By international convention, it passes through the site of the…

Alexander, Samuel

(Encyclopedia) Alexander, Samuel, 1859–1938, British philosopher, b. Australia. From 1893 to 1924 he was professor of philosophy at Victoria Univ., Manchester. Strongly influenced by the theory of…

tropical year

(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…

Luce, Henry Robinson

(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…

sidereal period

(Encyclopedia) sidereal period, in astronomy, length of time a body takes to complete an orbit relative to the fixed stars. See sidereal time.

year

(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…