Science / Tides and Currents / Sidereal Day: The time of the rotation of the Earth with respect to the vernal equinox. It equals approximately 0.997,27 of a mean solar day. Because of the precession of the equinoxes, the sidereal day thus defined is slightly less than the period of rotation with respect to the fixed stars, but the difference is less than a hundredth part of a second.
Day Noun Synonyms: time, hour, age, period, era, epoch, date, prime, heyday, lifetime
Day Verb Synonyms: daytime, daylight, broad daylight, light of day
Science / Tides and Currents / Day: The period of rotation of the Earth. There are several kinds of days depending on whether the Sun, Moon, or other object or location is used as the reference for the rotation. See constituent day, lun MORE
Science / Astrology / Sidereal Time: Time measured in relation to fixed stars, as distinguished from clock time, based upon the Sun's position relative to Earth. Astrological time data is listed in sidereal time units. MORE